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Sample records for montmorillonite-ca-modified carbon paste

  1. XRD, TEM, and thermal analysis of Arizona Ca-montmorillonites modified with didodecyldimethylammonium bromide.

    Science.gov (United States)

    Sun, Zhiming; Park, Yuri; Zheng, Shuilin; Ayoko, Godwin A; Frost, Ray L

    2013-10-15

    An Arizona SAz-2 calcium montmorillonite was modified by a typical dialkyl cationic surfactant (didodecyldimethylammonium bromide, abbreviated to DDDMA) through direct ion exchange. The obtained organoclays were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), high-resolution thermogravimetric analysis (HR-TG), and infrared emission spectroscopy (IES). The intercalation of surfactants greatly increased the basal spacing of the interlayers and the conformation arrangement of the loaded surfactant were assessed based on the XRD and TEM measurements. This work shows that the dialkyl surfactant can be directly intercalated into the montmorillonite without first undergoing Na(+) exchange. Moreover, the thermal stability of organoclays and the different arrangements of the surfactant molecules intercalated in the SAz-2 Ca-montmorillonite were determined by a combination of TG and IES techniques. The detailed conformational ordering of different intercalated surfactants under different conditions was also studied. The surfactant molecule DDDMA has proved to be thermally stable even at 400°C which indicates that the prepared organoclay is stable to significantly high temperatures. This study offers new insights into the structure and thermal stabilities of SAz-2 Ca-montmorillonite modified with DDDMA. The experimental results also confirm the potential applications of organic SAz-2 Ca-montmorillonites as adsorbents and polymer-clay nanocomposites. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. Thermal stability and hot-stage Raman spectroscopic study of Ca-montmorillonite modified with different surfactants: A comparative study

    International Nuclear Information System (INIS)

    Sun, Zhiming; Park, Yuri; Zheng, Shuilin; Ayoko, Godwin A.; Frost, Ray L.

    2013-01-01

    Highlights: • A typical Ca-montmorillonite was modified with three surfactants through ion exchange. • The organoclays were characterized by XRD, TG and hot stage Raman. • The structural geometry and thermal properties of organoclays were analyzed. • The prepared organoclays show potential prospects in the environmental remediation. - Abstract: Three long chain cationic surfactants were intercalated into Ca-montmorillonite through ion exchange and the obtained organoclays were characterized by X-ray diffraction (XRD), high resolution thermogravimetric analysis (TG) and Raman spectroscopy. The intercalation of surfactants not only changes the surface properties of clay from hydrophilic to hydrophobic but also greatly increases the basal spacing of the interlayers based on XRD analysis. The thermal stability of organoclays intercalated with three surfactants (TTAB, DTAB and CTAB) and the different arrangements of the surfactant molecules intercalated into Ca-montmorillonite were determined by TG-DTG analysis. A Raman spectroscopic study on the Ca-montmorillonite modified by three surfactants prepared at different concentrations provided the detailed conformational ordering of different intercalated long-chain surfactants under different conditions. The wavenumber of the antisymmetric stretching mode is more sensitive than that of the symmetric stretching mode to the mobility of the tail of the amine chain. At room temperature, the conformational ordering is more easily affected by the packing density in the lateral model. With the increase of the temperature, the positions of both the antisymmetric and symmetric stretching bands shift to higher wavenumbers, which indicates a decrease of conformational ordering. This study offers new insights into the structure and properties of Ca-montmorillonite modified with different long chain surfactants. Moreover, the experimental results confirm the potential applications of organic Ca-montmorillonites for the removal

  3. Break-up of Ca-montmorillonite particles by Na-montmorillonite

    International Nuclear Information System (INIS)

    Hedstroem, Magnus; Birgersson, Martin

    2012-01-01

    Document available in extended abstract form only. In the Swedish KBS-3 concept for a geological deep storage of spent nuclear fuel, bentonite of high montmorillonite content is proposed to serve as a buffer surrounding copper canisters containing the spent fuel. Montmorillonite has an exceptional affinity for water which results in the build-up of a swelling pressure when bentonite is placed in a confined volume. However, there is a concern that during and after a glaciation, meltwater of low ionic strength may cause the bentonite to swell extensively into fractures and turn into a sol that could be transported away by the seeping water. It is thus warranted to understand the behaviour of montmorillonite at aqueous condition of low ionic strength. Turbidity measurements were used to a large extent in previous work to follow the free swelling or settling process of montmorillonite in various aqueous solutions and thereby give information regarding sol formation. From theory we know that turbidity of a suspension is proportional to the particle concentration. However turbidity is also proportional to V p 2 where V p is the volume of the scattering particle. Thus the fact that turbidity of a Ca-montmorillonite suspension is higher than the turbidity of a Na- montmorillonite suspension of the same clay concentration indicates that Na-montmorillonite separate into smaller particles than Ca-montmorillonite. In this work we make use this size dependence to quantify the difference between Wyoming, Milos and Kutch montmorillonite in particular with respect to how mixed Ca/Na montmorillonite systems behave. Some Ca/Mg, Mg/Na and Na/K systems are also included for comparison. Figure 1 shows the final (stabilized) turbidity response of mixed Wy-Ca/Na montmorillonite as a function of the fraction of Ca 2+ in the clay. Starting material are suspensions of homo-ionic Wy-Ca and Wy-Na montmorillonite at a concentration of 1 g/l. The turbidity of the suspensions of the homo

  4. Methanol oxidation at carbon paste electrodes modified with (Pt–Ru)/carbon aerogels nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Fort, Carmen I., E-mail: iladiu@chem.ubbcluj.ro [Laboratory of Electrochemical Research and Nonconventional Materials, Babes-Bolyai University, Arany Janos 11, RO-400028, Cluj-Napoca (Romania); Cotet, Liviu C. [Laboratory of Electrochemical Research and Nonconventional Materials, Babes-Bolyai University, Arany Janos 11, RO-400028, Cluj-Napoca (Romania); Vasiliu, Florin [The National Institute of Materials Physics, Atomistilor str. 105 bis, PO Box MG. 7, Magurele, RO 077125, Bucharest (Romania); Marginean, Petre [National Institute for Research and Development of Isotopic and Molecular Technologies, RO 400293, Cluj-Napoca (Romania); Danciu, Virginia; Popescu, Ionel C. [Laboratory of Electrochemical Research and Nonconventional Materials, Babes-Bolyai University, Arany Janos 11, RO-400028, Cluj-Napoca (Romania)

    2016-04-01

    Mesoporous carbon aerogels (CAs) impregnated with (Pt–Ru) nanoparticles were prepared, incorporated into carbon paste electrodes (CPEs) and investigated as electrocatalysts for CH{sub 3}OH electro-oxidation. The sol–gel method, followed by supercritical drying with liquid CO{sub 2} and thermal pyrolysis in an inert atmosphere, was used to obtain high mesoporous CAs. (Pt–Ru)/CAs nanocomposites with various (Pt–Ru) loading were prepared by using Ru(AcAc){sub 3} and H{sub 2}PtCl{sub 6} as metal precursors and the impregnation method. The morpho-structural peculiarities of the so prepared (Pt–Ru)/CAs electrocatalysts were examined by using elemental analysis, N{sub 2} adsorption-desorption isotherms, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) and selected area electron diffraction (SAED). Cyclic voltammetry measurements, carried out at (Pt–Ru)/CA-CPEs incorporating nanocomposites with various Pt–Ru loading and different specific surface areas, showed that CA with the highest specific surface area (843 m{sup 2}/g) and impregnated with 6% (w/w) (Pt–Ru) nanoparticles exhibit the best CH{sub 3}OH electro-oxidation efficiency. The Michaelis–Menten formalism was used to describe the dependence of the oxidation peak current on the CH{sub 3}OH concentration, allowing the estimation of the modified electrodes sensitivities. Thus, for (Pt–Ru, 10%)/CA{sub 535}-CPE was observed the highest sensitivity (12.5 ± 0.8 mA/M) and, at the same time, the highest maximum current density ever reported (153.1 mA/cm{sup 2} for 2 M CH{sub 3}OH and an applied potential of 600 mV vs. SHE). - Highlights: • (Pt–Ru) nanoparticles were deposited on high mesoporous carbon aerogels (CAs). • (Pt–Ru)/CAs were characterized by TEM, EDX, SAED and N{sub 2} adsorption-desorption. • Carbon paste electrodes modified with (Pt–Ru)/CA were used for CH{sub 3}OH oxidation. • (Pt–Ru, 10

  5. Preparation and Characterization of Modified Montmorillonite/Paraffin Phase Change Microcapsules for Energy Storage

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    LIN Sen

    2017-03-01

    Full Text Available The phase change microcapsules of modified montmorillonite/paraffin were prepared by Pickering emulsion method. Analytic techniques of optical microscopy, scanning electron microscopy(SEM, infrared spectroscopy(FTIR, differential scanning calorimetry(DSC and thermogravimetry(TG were utilized for characterizing chemical structure, morphology and thermal properties. Results show that modified montmorillonite as a new type wall material has excellent performance for protecting core material of paraffin. FTIR spectra of phase change of modified montmorillonite/paraffin microcapsules shows that their characteristic peaks match with corresponding peaks of pure paraffin and modified montmorillonite. DSC results indicate that modified montmorillonite/paraffin microcapsules have similar solid-liquid phase change temperature with pure paraffin. The phase transition enthalpy values of microcapsules with paraffin contents varying from 55% to 80% are 110.5-147.2J/g, indicating that microcapsules have excellent thermal storage performance and the phase change properties can be adjusted by changing contents of paraffin. TG results confirm that modified montmorillonite/paraffin microcapsules have outstanding thermal stability. The presented study indicates that modified montmorillonite is a suitable wall material for preparing paraffin microcapsule. Modified montmorillonite/paraffin microcapsules have advantages of low cost and high performance with a great application potential in the field of thermal storage.

  6. Imprinted zeolite modified carbon paste electrode as a potentiometric sensor for uric acid

    Science.gov (United States)

    Khasanah, Miratul; Widati, Alfa Akustia; Fitri, Sarita Aulia

    2016-03-01

    Imprinted zeolite modified carbon paste electrode (carbon paste-IZ) has been developed and applied to determine uric acid by potentiometry. The imprinted zeolite (IZ) was synthesized by the mole ratio of uric acid/Si of 0.0306. The modified electrode was manufactured by mass ratio of carbon, IZ and solid paraffin was 40:25:35. The modified electrode had shown the measurement range of 10-5 M to 10-2 M with Nernst factor of 28.6 mV/decade, the detection limit of 5.86 × 10-6 M and the accuracy of 95.3 - 105.0%. Response time of the electrode for uric acid 10-5 M - 10-2 M was 25 - 44 s. The developed electrode showed the high selectivity toward uric acid in the urea matrix. Life time of the carbon paste-IZ electrode was 10 weeks.

  7. Nanocomposites prepared from acrylonitrile butadiene rubber and organically modified montmorillonite with vinyl groups

    Science.gov (United States)

    Han, Mijeong; Kim, Hoonjung; Kim, Eunkyoung

    2006-01-01

    Nanocomposites were prepared from acrylonitrile-butadiene rubber (NBR), vinyl groups containing organically modified montmorillonite and additives, such as zinc oxide, stearic acid, and sulfur. The organically modified montmorillonites used in these nanocomposites were prepared by ion exchange reactions of N,N'-dimethylalkyl-(p-vinylbenzyl)-ammonium chlorides (DAVBAs, alkyl = octyl, dodecyl, and octadecyl) with sodium montmorillonite (Na+-MMT). NBR nanocomposites were obtained by controlling both the mixing and vulcanization conditions, by using a Brabender mixer and hot-press process. X-ray diffraction (XRD) analysis shows that, depending on the amount of montmorillonite that is added, both exfoliated and intercalated nanocomposite structures are formed. The NBR/DAVBA-MMT nanocomposites exhibit much higher mechanical properties (e.g., tensile strength, Young's modulus, 300% modulus, and hardness) as well as gas barrier properties as compared to NBR Na+-MMT or NBR composites generated from modified montmorillonites without vinyl groups. Consistent with the results of XRD, transmission electron microscopy (TEM) reveals that the intercalation and exfoliation structures of the nanocomposites coexist and that the DAVBA-MMT layers are well dispersed in NBR.

  8. [Adsorptive Stabilization of Soil Cr (VI) Using HDTMA Modified Montmorillonite].

    Science.gov (United States)

    2016-03-15

    A series of organo-montomorillonites were prepared using Na-montomorillonite and hexadecyl trimethyl ammonium bromide (HDTMA). The organo-montomorillonites were then investigated for the remediation of Cr(VI) contaminated soils. FT-IR, XRD, SEM and N2 -BET, CEC, Zeta potential measurement were conducted to understand the structural changes of montmorillonites as different amounts of HDTMAs were added as modifier. The characterization results indicated that the clay interlayer spacing distance increased from 1. 25 nm to 2. 13 nm, the clay surface roughness decreased, the clay surface area reduced from 38.91 m² · g⁻¹ to 0.42 m² · g⁻¹, the clay exchangeable cation amount reduced from 62 cmol · kg⁻¹ to 9.9 cmol · kg⁻¹ and the clay surface charge changed from -29.1 mV to 5.59 mV as the dosage of HDTMA in montmorillonite was increased. The TCLP (toxicity characteristic leaching procedure) was used to evaluate the leachate toxicity of Cr(VI). The effects of the initial soil Cr(VI) concentration, montmorillonites dosage, reaction time and HDTMA modification amount were investigated, respectively. The results revealed that modification of montmorillonites would manifest an attenuated physical adsorptive effect and an enhanced electrostatic adsorptive effect on Cr(VI), suggesting electrostatic effect was the major force that resulted in improved Cr(VI) adsorption onto HDTMA modified montmorillonites.

  9. Diffusion of helium and estimated diffusion coefficients of hydrogen dissolved in water-saturated, compacted Ca-montmorillonite

    International Nuclear Information System (INIS)

    Higashihara, Tomohiro; Sato, Seichi; Ohashi, Hiroshi; Otsuka, Teppei

    2001-01-01

    The diffusion coefficients of hydrogen gas dissolved in water-saturated, compacted montmorillonite are required to estimate the performance of bentonite buffer materials for geological disposal of nuclear waste. As part of the effort to determine the diffusion coefficients, the diffusion coefficients of helium in water-saturated, compacted calcium montmorillonite (Ca-montmorillonite) were determined as a function of dry density, 0.78 to 1.37x10 3 kg m -3 , by a transient diffusion method. The diffusion coefficients were from 8.3x10 -10 m 2 s -1 at 0.78x10 3 kgm -3 to 2.8x10 -10 m 2 s -1 at 1.37x10 3 kgm -3 . The data obtained by this diffusion experiment of helium were highly reproducible. The diffusion coefficients of helium in Ca-montmorillonite were somewhat larger than those previously obtained for helium in sodium montmorillonite (Na-montmorillonite). The diffusion coefficients of hydrogen gas in the montmorillonites were roughly estimated using the diffusion coefficients of helium. These estimates were based on assumptions that both helium and hydrogen molecules are non-adsorptive and that the geometric factors in the compacted montmorillonites are approximately the same for diffusion of helium and diffusion of hydrogen. (author)

  10. Electrochemical oxidation of ascorbic acid mediated by carbon nano tubes/ Li+/ carbon paste modified solid electrode

    International Nuclear Information System (INIS)

    Goh, J.K.; Tan, W.T.

    2008-01-01

    Multi-walled carbon nano tube (MWCNT) was used to modify BPPG electrode because of its unique structure and extraordinary properties. MWCNT modified electrode exhibited obvious enhancing and electro catalyzing effects to the oxidation of ascorbic acid using cyclic voltammetry technique. MWCNT was bonded on BPPG electrode surface using carbon paste with ratio of 30 % (w/ W) carbon paste (binder): 70 % (w/ w) MWCNT. This method of modification has lowered the capacitance background current and enabled lower detection limit of ascorbic acid concentration. The electrical conductivity property of MWCNT modified electrode was further improved with the intercalation with lithium ion and resulted in current enhancement of 2 times on the oxidation current of ascorbic acid. Parameters of pH and temperature showed significant relation to the sensitivity of MWCNT modified electrode. Under the optimized parameters, the calibration curve constructed was linear up from 50 μM to 5 mM with sensitivity of 34.5 mA M -1 . The practical application of MWCNT modified electrode was demonstrated with Vitamin C pill and orange juice. Good reproducibility and recovery of ascorbic acid concentration showed the feasibility of MWCNT modified electrode to be used in the detection of ascorbic acid in aqueous solution. This also proposed MWCNT modified BPPG electrode possessed advantages such as low detection limit, high stability, low cost and simplicity in fabrication. (author)

  11. New Electrochemically-Modified Carbon Paste Inclusion β-Cyclodextrin and Carbon Nanotubes Sensors for Quantification of Dorzolamide Hydrochloride

    Directory of Open Access Journals (Sweden)

    Nawal Ahmad Alarfaj

    2016-12-01

    Full Text Available The present article introduces a new approach to fabricate carbon paste sensors, including carbon paste, modified carbon paste inclusion β-cyclodextrin, and carbon nanotubes for the quantification of dorzolamide hydrochloride (DRZ. This study is mainly based on the construction of three different carbon paste sensors by the incorporation of DRZ with phosphotungstic acid (PTA to form dorzolamide-phosphotungstate (DRZ-PT as an electroactive material in the presence of the solvent mediator ortho-nitrophenyloctyl ether (o-NPOE. The fabricated conventional carbon paste sensor (sensor I, as well as the other modified carbon paste sensors using β-cyclodextrin (sensor II and carbon nanotubes (sensor III, have been investigated. The sensors displayed Nernstian responses of 55.4 ± 0.6, 56.4 ± 0.4 and 58.1 ± 0.2 mV·decade−1 over concentration ranges of 1.0 × 10−5–1.0 × 10−2, 1.0 × 10−6–1.0 × 10−2, and 5.0 × 10−8–1.0 × 10−2 mol·L−1 with lower detection limits of 5.0 × 10−6, 5.0 × 10−7, and 2.5 × 10−9 mol·L−1 for sensors I, II, and III, respectively. The critical performance of the developed sensors was checked with respect to the effect of various parameters, including pH, selectivity, response time, linear concentration relationship, lifespan, etc. Method validation was applied according to the international conference on harmonisation of technical requirements for registration of pharmaceuticals for human use ICH guidelines. The developed sensors were employed for the determination of DRZ in its bulk and dosage forms, as well as bio-samples. The observed data were statistically analyzed and compared with those obtained from other published methods.

  12. Determination of ascorbic acid in pharmaceutical preparation and fruit juice using modified carbon paste electrode

    Directory of Open Access Journals (Sweden)

    Simona Žabčíková

    2016-06-01

    Full Text Available Acrobic acid is key substance in the human metabolism and the rapid and accurate determination in food is of a great interest. Ascorbic acid is an electroactive compound, however poorly responded on the bare carbon paste electrodes. In this paper, brilliant cresyl blue and multi-walled carbon nanotubes were used for the modification of carbon paste electrode. Brilliant cresyl blue acts as a mediator improving the transition of electrons, whereas multiwalled carbon nanotubes increased the surface of the electrode. Both brilliant cresyl blue and multiwalled carbon nanotubes were added directly to the composite material. The electrochemical behavior of modified electode was determined in electrolyte at various pH, and the effect of the scan rate was also performed. It was shown that the electrochemical process on the surface of the modified carbon paste electrode was diffusion-controlled. The resulted modified carbon paste electrode showed a good electrocatalytic activity towards the oxidation of ascorbic acid at a reduced overpotential of +100 mV descreasing the risk of interferences. A linear response of the ascorbic acid oxidation current measured by the amperometry in the range of 0.1 - 350 µmol.L-1 was obtained applying the sensor for the standard solution. The limit of detection and limit of quantification was found to be 0.05 and 0.15 µmol.L-1, respectively. The novel method was applied for the determination of ascorbic acid in pharmaceutical vitamin preparation and fruit juice, and the results were in good agreement with the standard HPLC method. The presented modification of carbon paste electrode is suitable for the fast, sensitive and very accurate determination of ascorbic acid in fruit juices and pharmaceutical preparation.

  13. Electrochemical Investigation of Catechol at Poly(niacinamide Modified Carbon Paste Electrode: A Voltammetric Study

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    A. B. Teradale

    2016-01-01

    Full Text Available A polymeric thin film modified electrode, that is, poly(niacinamide modified carbon paste electrode (MCPE, was developed for the electrochemical determination of catechol (CC by using cyclic voltammetric technique. Compared to bare carbon paste electrode (BCPE, the poly(niacinamide MCPE shows good electrocatalytic activity towards the oxidation of catechol in phosphate buffer solution (PBS of physiological pH 7.4. All experimental parameters were optimized. Poly(niacinamide modified carbon paste electrode gave a linear response between concentration of CC and its anodic peak current in the range within 20.6–229.0 μM. The limit of detection (3S/M and limit of quantification (10S/M were 1.497 μM and 4.99 μM, respectively. From the study of scan rate variation, the electrode process was found to be adsorption-controlled. The involvement of protons and electrons in the oxidation of CC was found to be equal. The probable electropolymerisation mechanism of niacinamide was proposed. Finally, this method can be used in development of a sensor for sensitive determination of CC.

  14. Immobilization of Glucose Oxidase on Modified-Carbon-Paste-Electrodes for Microfuel Cell

    Directory of Open Access Journals (Sweden)

    Laksmi Ambarsari

    2016-03-01

    Full Text Available Glucose oxidase (GOx is being developed for many applications such as an implantable fuel cell, due to its attractive property of operating under physiological conditions. This study reports the functional immobilization of glucose oxidase onto polyaniline-nanofiber-modified-carbon-paste-electrodes (GOx/MCPE as bioanodes in fuel cell applications. In particular, GOx is immobilized onto the electrode surface via a linker molecule (glutaraldehyde. Polyaniline, synthesized by the interfacial polymerization method, produces a morphological form of nanofibers (100-120 nm which have good conductivity. The performance of the polyaniline-modified-carbon-paste-electrode (MCPE was better than the carbon- paste-electrode (CPE alone. The optimal pH and temperature of the GOx/MCPE were 4.5 (in 100 mM acetate buffer and 65 °C, respectively. The GOx/MCPE exhibit high catalytic performances (activation energy 16.4 kJ mol-1, have a high affinity for glucose (Km value 37.79 µM and can have a maximum current (Imax of 3.95 mA. The sensitivity of the bioelectrode also was high at 57.79 mA mM-1 cm-2.

  15. Genotoxicity of unmodified and organo-modified montmorillonite

    DEFF Research Database (Denmark)

    Sharma, Anoop Kumar; Schmidt, Bjørn; Frandsen, Henrik Lauritz

    2010-01-01

    absent in the filtered samples, which was independently confirmed by dynamic light-scattering measurements. Detection and identification of free quaternary ammonium modifier in the filtered sample was carried out by HPLC-Q-TOF/MS and revealed a total concentration of a mixture of quaternary ammonium...... assay, none of the clays produced ROS in a cell-free test system (the DCFH-DA assay). Inductively coupled plasma mass-spectrometry (ICP-MS) was used to detect clay particles in the filtered samples using aluminium as a tracer element characteristic to clay. The results indicated that clay particles were...... analogues of 1.57 mu g/ml. These findings suggest that the genotoxicity of organo-modified montmorillonite was caused by the organo-modifier. The detected organo-modifier mixture was synthesized and comet-assay results showed that the genotoxic potency of this synthesized organo-modifier was in the same...

  16. Proton conductive montmorillonite-Nafion composite membranes for direct ethanol fuel cells

    Science.gov (United States)

    Wu, Xiu-Wen; Wu, Nan; Shi, Chun-Qing; Zheng, Zhi-Yuan; Qi, Hong-Bin; Wang, Ya-Fang

    2016-12-01

    The preparation of Nafion membranes modified with montmorillonites is less studied, and most relative works mainly applied in direct methanol fuel cells, less in direct ethanol fuel cells. Organic/inorganic composite membranes are prepared with different montmorillonites (Ca-montmorillonite, Na-montmorillonite, K-montmorillonite, Mg-montmorillonite, and H-montmorillonite) and Nafion solution via casting method at 293 K in air, and with balance of their proton conductivity and ethanol permeability. The ethanol permeability and proton conductivity of the membranes are comparatively studied. The montmorillonites can well decrease the ethanol permeability of the membranes via inserted them in the membranes, while less decrease the proton conductivities of the membranes depending on the inserted amount and type of montmorillonites. The proton conductivities of the membranes are between 36.0 mS/cm and 38.5 mS/cm. The ethanol permeability of the membranes is between 0.69 × 10-6 cm2/s and 2.67 × 10-6 cm2/s.

  17. Cyclic Voltammetric Investigation of Dopamine at Poly-(Gabapentin Modified Carbon Paste Electrode

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    M. T. Shreenivas

    2011-01-01

    Full Text Available The poly (gabapentin film was prepared on the surface of carbon paste electrode by electrochemical method using cyclic voltammetric technique. The poly (gabapentin film-modified carbon paste electrode was calibrated with standard potassium ferrocyanide solution in 1 M KCl as a supporting electrolyte. The prepared poly (gabapentin film-coated electrode exhibits excellent electrocatalytic activity towards the detection of dopamine at physiological pH. The scan rate effect was found to be diffusion-controlled electrode process. The concentration effect of dopamine was studied, and the redox peak potentials of dopamine were dependant on pH.

  18. Carbon nanotubes rooted montmorillonite (CNT-MM) reinforced nanocomposite membrane for PEM fuel cells

    International Nuclear Information System (INIS)

    Manikandan, Dhanagopal; Mangalaraja, Ramalinga Viswanathan; Avila, Ricardo E.; Siddheswaran, Rajendran; Ananthakumar, Solaiappan

    2012-01-01

    Highlights: ► Novel montmorillonite-CNT (MM-CNT) nanohybrid materials were produced by CVD. ► Highly selective crystalline carbon nanotubes were grown over montmorillonite. ► Fabricated Nafion-MM-CNT nanocomposite membrane by solution casting method. ► Homogeneous dispersion of MM-CNT in the Nafion matrix was achieved. ► Combined effect of montmorillonite and CNT improves the thermal stability of Nafion. - Abstract: Nafion based nanocomposite membranes containing montmorillonite-carbon nanotubes (a binary hybrid material) were produced to develop high performance polymer electrolyte fuel cells. Multi walled carbon nanotubes were grown over 20 and 25 wt% iron loaded montmorillonite catalysts by CVD using acetylene as the carbon precursor. Growth experiments were carried out at optimised conditions to obtain highly selective crystalline carbon nanotubes. X-ray diffraction spectra of the catalysts were recorded for the structural characterisation and definition of particle size. The carbon nanotubes obtained were examined by various physico chemical characterisation studies such as SEM, TEM, Raman spectroscopy and TG analyses to understand the morphology and crystallinity of the CNTs. The MM-CNT hybrid material with I D /I G ratio of Raman spectral band as 0.53 represents the high selectivity towards CNTs. Thus the hybrid material produced was considered as the best nanofiller to develop polymer nanocomposites. Nafion based nanocomposite membranes were prepared by adding MM-CNT as nanofiller by solution casting method. A better dispersion of MM-CNT into the Nafion matrix was observed and the addition of the MM-CNT improved the thermal stability of the Nafion membrane.

  19. Seawater Durability of Nano-Montmorillonite Modified Single-Lap Joining Epoxy Composite Laminates

    OpenAIRE

    ULUS, Hasan; KAYBAL, Halil Burak; DEMİR, Okan; TATAR, Ahmet Caner; SENYURT, Muhammed Ali; AVCI, Ahmet

    2018-01-01

    The objective of this study was to investigate of nano-montmorillonite modified epoxy composite single-lap bonded joints, after being exposed to seawater immersion in order to understand the effect of seawater environment on their performance. To prepare the nano adhesives, nano montmorillonite (2 wt %) was incorporated into epoxy resin. Composite bonded specimens which manufactured with VARIM (Vacuum Assisted Resin Infusion Method) were prepared accordance with ASTM D5868-01 and immersed in ...

  20. Carbon nanotubes rooted montmorillonite (CNT-MM) reinforced nanocomposite membrane for PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Manikandan, Dhanagopal, E-mail: dmani_cat@yahoo.co.in [Department of Materials Engineering, Faculty of Engineering, University of Concepcion, Concepcion (Chile); Mangalaraja, Ramalinga Viswanathan, E-mail: mangal@udec.cl [Department of Materials Engineering, Faculty of Engineering, University of Concepcion, Concepcion (Chile); Avila, Ricardo E. [Personal Dosimetry Section, Chilean Nuclear Energy Commission, Cas. 188-D, Santiago (Chile); Siddheswaran, Rajendran [Department of Materials Engineering, Faculty of Engineering, University of Concepcion, Concepcion (Chile); Ananthakumar, Solaiappan [Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum, Kerala (India)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer Novel montmorillonite-CNT (MM-CNT) nanohybrid materials were produced by CVD. Black-Right-Pointing-Pointer Highly selective crystalline carbon nanotubes were grown over montmorillonite. Black-Right-Pointing-Pointer Fabricated Nafion-MM-CNT nanocomposite membrane by solution casting method. Black-Right-Pointing-Pointer Homogeneous dispersion of MM-CNT in the Nafion matrix was achieved. Black-Right-Pointing-Pointer Combined effect of montmorillonite and CNT improves the thermal stability of Nafion. - Abstract: Nafion based nanocomposite membranes containing montmorillonite-carbon nanotubes (a binary hybrid material) were produced to develop high performance polymer electrolyte fuel cells. Multi walled carbon nanotubes were grown over 20 and 25 wt% iron loaded montmorillonite catalysts by CVD using acetylene as the carbon precursor. Growth experiments were carried out at optimised conditions to obtain highly selective crystalline carbon nanotubes. X-ray diffraction spectra of the catalysts were recorded for the structural characterisation and definition of particle size. The carbon nanotubes obtained were examined by various physico chemical characterisation studies such as SEM, TEM, Raman spectroscopy and TG analyses to understand the morphology and crystallinity of the CNTs. The MM-CNT hybrid material with I{sub D}/I{sub G} ratio of Raman spectral band as 0.53 represents the high selectivity towards CNTs. Thus the hybrid material produced was considered as the best nanofiller to develop polymer nanocomposites. Nafion based nanocomposite membranes were prepared by adding MM-CNT as nanofiller by solution casting method. A better dispersion of MM-CNT into the Nafion matrix was observed and the addition of the MM-CNT improved the thermal stability of the Nafion membrane.

  1. Enhanced sorption of radiocobalt from water by Bi(III) modified montmorillonite: A novel adsorbent

    International Nuclear Information System (INIS)

    Guo Zhiqiang; Li Yuan; Zhang Shouwei; Niu Haihong; Chen Zhesheng; Xu Jinzhang

    2011-01-01

    Highlights: → Bi-Mt has higher surface area than Ca-Mt. → The sorption of Co(II) on Bi-Mt is dependent on ionic strength and pH. → The sorption of Co(II) on Bi-Mt is an spontaneous and endothermic process. → Bi-Mt has good practical application potential in wastewater disposal. - Abstract: In this study, Ca-montmorillonite (Ca-Mt) modified with Bi 3+ was used as a novel adsorbent for the sorption of Co(II) from aqueous solutions. The sorption of Co(II) on Bi-montmorillonite (Bi-Mt) was investigated as a function of contact time, pH, ionic strength, adsorbent content, Co(II) concentrations, fulvic acid (FA) and temperature. Compared to Ca-Mt, Bi-Mt showed a higher affinity to bind Co(II) ions. The sorption percentage of Co(II) on Bi-Mt increased with increasing pH at pH 3.0-8.5, and then maintained the high level at pH 8.5-12. The sorption of Co(II) on Bi-Mt was dependent on ionic strength at low pH, and independent of ionic strength at high pH. The presence of FA enhanced Co(II) sorption at low pH, but suppressed Co(II) sorption at high pH. The thermodynamic data derived from temperature dependent sorption isotherms suggested that the sorption of Co(II) on Bi-Mt was spontaneous and endothermic process. Outer-sphere surface complexation and/or ion exchange were the main mechanisms of Co(II) sorption on Bi-Mt at low pH, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. From the experimental results, it is possible to conclude that Bi-Mt is suitable for application of Co(II) removal from aqueous solutions.

  2. Osmotic pressure in Ca/Na montmorillonite dispersions: Monte Carlo simulations

    International Nuclear Information System (INIS)

    Joensson, Bo; Aakesson, T.; Segad, M.; Cabane, B.

    2010-01-01

    Document available in extended abstract form only. In the past, clay-water systems have been extensively studied. due to its importance in agricultural as well as technological applications. A more recent use of clay is as sealing material for nuclear waste. The success for such a containment depends on the clay structure and its swelling properties. This means that the clay should be able to sustain considerable changes in the surrounding ground water including salinities of glacial melt water as well as sea water, while still being an effective hydraulic barrier. We have approached this problem using statistical mechanical simulation techniques. The osmotic pressure in Ca/Na montmorillonite dispersions has been calculated via Monte Carlo simulations. For a clay system in equilibrium with pure water, Monte Carlo simulations predict a large swelling when the clay counterions are monovalent, while in presence of divalent counterions a limited swelling is predicted with an aqueous layer between the clay lamellae of about 1 nm - in excellent agreement with SAXS data. Montmorillonite in contact with a salt reservoir with e.g. both Na and Ca counterions will only show a modest swelling unless the Na + concentration in the bulk is several orders of magnitude larger than the Ca 2+ concentration. This is true both for a clay repository surrounded by ground water as well as sea water of high salinity. The limited swelling of clay in presence of divalent counterions is a consequence of ion-ion correlations, which both reduce the entropic repulsion and give rise to an attractive component in the total osmotic pressure. Ion-ion correlations also favour divalent counterions when competing with monovalent ones. This is an important aspect for the retention of radioactive charged species. A more fundamental result of ion-ion correlations is that the osmotic pressure as a function of clay sheet separation becomes non-monotonic - which indicates the possibility of a phase

  3. Degradation of surfactant-modified montmorillonites in HCl

    International Nuclear Information System (INIS)

    Madejová, Jana; Pálková, Helena; Jankovič, Ľuboš

    2012-01-01

    The effect of surfactant size on the extent of montmorillonites decomposition in HCl was investigated. Na-SAz montmorillonite and tetraalkylammonium salts of alkyl-chains length increasing from methyl- Me 4 N to pentyl- Pe 4 N were used for organo-montmorillonites preparation. Decreasing intensity of d 001 diffraction proved destruction of montmorillonite structure connected with gradual surfactant release. A shift of the SiO stretching band to 1097 cm −1 confirmed formation of amorphous silica phase. A new band near 7315 cm −1 corresponding to SiOH overtone revealed creation of protonated silica. This band was observed in the spectra of all acid-treated samples, also in those with minor decomposition of the structure. The size of the cations significantly affected decomposition of montmorillonites in HCl. The less stable were Na-SAz and Me 4 N-SAz in which the content of octahedral atoms dropped to ∼5% of their original values upon 8 h treatments. Et 4 N-SAz and Pr 4 N-SAz were slightly more resistant mainly at short times. Bu 4 N-SAz and Pe 4 N-SAz showed the least structural modifications, only 50% and 35% of octahedral atoms, respectively, were released into solution within 8 h treatments. This observation proves that bulky alkylammonium cations covering the inner and outer surfaces of montmorillonite prevent effectively the access of protons to the layers protecting the mineral from degradation in the acid. - Highlights: ► Hybrid materials were prepared from montmorillonite and alkylammonium cations with short alkyl chains. ► The effect of surfactant on organo-montmorillonites dissolution in HCl was studied. ► With increasing size of cation the extent of montmorillonite decomposition decreased. ► Bulky surfactants prevent the access of protons to the layers and thus protect montmorillonite from degradation.

  4. Characterization of sodium dodecyl sulfate modified iron pillared montmorillonite and its application for the removal of aqueous Cu(II) and Co(II)

    International Nuclear Information System (INIS)

    Li Shuzhen; Wu Pingxiao

    2010-01-01

    Anionic surfactant modified Fe-pillared montmorillonites were prepared by Fe-hydrate solution and sodium dodecyl sulfate (SDS) solution. These organo-inorgano complex montmorillonites were divided into three types (CM1, CM2 and CM3) depending on different intercalation processes. X-ray diffraction spectra, the Fourier transform infrared (FTIR) spectra were used to analyze the structure of the raw and modified montmorillonites. X-ray photoelectron spectra of the simples have been studied to determine spectral characteristics to allow the identification of Fe(III) hydroxide. The specific surface area of the host montmorillonite (M0) is 73.2 m 2 /g, while for the modified montmorillonites it is 114.0 m 2 /g, 117.2 m 2 /g, and 115.8 m 2 /g, respectively. The mesopore volumes of the montmorillonites decrease after modification. Ions of copper and cobalt were selected as adsorbates to evaluate the adsorption performance of each montmorillonite. The adsorption data was analyzed by both Freundlich and Langmuir isotherm models and the data was well fit by the Langmuir isotherm model. The adsorption was efficient and significantly influenced by metal speciation, metal concentration, contact time, and pH. Higher adsorption capacity of the modified montmorillonites were obtained at pH 5-6. The results of desorption indicated that the metal ions were covalently bound to the modified montmorillonites.

  5. Adsorption of Carbon Dioxide, Methane, and Their Mixtute by Montmorillonite in the Presence of Water

    KAUST Repository

    Kadoura, Ahmad Salim; Nair, Arun Kumar Narayanan; Sun, Shuyu

    2016-01-01

    Using grand canonical Monte Carlo (GCMC) simulations, we study the adsorption behavior of CH4, CO2, and their mixture at 298.15 K and pressures up to 50 bar in Na-, Cs-, and Ca-montmorillonite clays in the presence of water. Montmorillonite clays

  6. Effect of kaolinite and Ca-montmorillonite on the alleviation of soil water repellency

    Czech Academy of Sciences Publication Activity Database

    Dlapa, P.; Doerr, S. H.; Lichner, Ľ.; Šír, Miloslav; Tesař, Miroslav

    2004-01-01

    Roč. 50, č. 8 (2004), s. 358-363 ISSN 0370-663X R&D Projects: GA AV ČR IAA3042301; GA AV ČR IBS2060104 Keywords : water repellency * kaolinite * Ca-montmorillonite Subject RIV: DA - Hydrology ; Limnology Impact factor: 0.379, year: 2004

  7. Fe(III)-EDDHA and -EDDHMA sorption on Ca-montmorillonite, ferrihydrite, and peat.

    Science.gov (United States)

    Hernández-Apaolaza, L; Lucena, J J

    2001-11-01

    The effectiveness of Fe chelates as Fe sources and carriers in soil can be severely limited by the adsorption of Fe chelates or chelating agents in the solid phase. To study this phenomenon, well-characterized peat, Ca-montmorillonite, and ferrihydrite were used as model compounds, and the adsorption of Fe-EDDHA and Fe-EDDHMA chelates were studied. Sorption isotherms for the meso and racemic isomers of these chelates on the soil materials are described. The variability of sorption with pH in peat and ferrihydrite was also determined because both have variable surface charge at different pH values. In montmorillonite, at low concentrations, the retention of Fe from the Fe-EDDHMA chelate is greater than the one of the Fe-EDDHA chelate. As well as the concentration increased, the inverse situation occurs. The behavior of both meso and racemic isomers of chelates in contact with Ca-montmorillonite is similar. The Fe-meso-EDDHA isomer was highly adsorbed on ferrihydrite, but the racemic isomer is not significantly retained by this oxide. For Fe-EDDHMA isomers, the racemic isomer was more retained by the oxide, but a small sorption of the racemic isomer was also observed. Results suggest that Fe-EDDHA chelates were more retained in peat than Fe-EDDHMA chelates. The most retained isomer of Fe-EDDHA was the meso isomer. For Fe-EDDHMA, the adsorption was very low for both racemic and meso isomers.

  8. Sorption of polluting metal ions on a palm tree frond sawdust studied by the means of modified carbon paste electrodes.

    Science.gov (United States)

    Nouacer, Sana; Hazourli, Sabir; Despas, Christelle; Hébrant, Marc

    2015-11-01

    Water remediation by adsorption of the metal ions on a low cost sorbent is the frame of the present study. The metal ions adsorption properties of sawdust of palm tree fronds (PTF sawdust) are investigated by both equilibrium measurements and modified carbon paste electrode. The ability to adsorb Cu(II), Cr(VI) and As(III) in significant quantities is demonstrated. Carbon paste electrodes modified by incorporation of PTF sawdust (PTF-CPE) or, for comparison, an organically modified silica for the detection of copper(II) are investigated in term of sensitivity, estimation of number of possible reuses, repeatability and interference effect. A detection limit for Cu(II) analysis of 1.0×10(-8) M has been achieved after 5 min preconcentration and a single PTF-CPE can be used for up to 10 preconcentration-analysis-regeneration cycles. The relative standard deviation (n=9) for the determination of a 10(-6) M Cu(II) solution (pH=5) was about 26%. The effects of Ca(II), As(III) and Cr(VI) on the copper detection are investigated: calcium ions were shown to compete with copper on the same adsorption sites, arsenic(III) has no effect on the copper detection whereas chromium(VI) was shown to enhance the copper detection. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. The application of modified montmorillonite in the processes of baromembrane purification of water from U (VI)

    International Nuclear Information System (INIS)

    Yurlova, L.Yu.; Krivoruchko, A.P.

    2010-01-01

    The processes of uranium-containing water purification by ultra- and nanofiltration methods combined with the use of montmorillonite modified by polyethyleneimine are studied. It is shown that the application of montmorillonite allows one to obtain the high indices of the uranium-containing water purification by baromembrane methods.

  10. Ibuprofen analysis in blood samples by palladium particles-impregnated sodium montmorillonite electrodes: Validation using high performance liquid chromatography.

    Science.gov (United States)

    Loudiki, A; Boumya, W; Hammani, H; Nasrellah, H; El Bouabi, Y; Zeroual, M; Farahi, A; Lahrich, S; Hnini, K; Achak, M; Bakasse, M; El Mhammedi, M A

    2016-12-01

    The electrochemical detection of ibuprofen has been studied on Palladium-Montmorillonite (Mt) modified carbon paste electrode using differential pulse voltammetry. The optimization of the modifier preparation and the instrumental parameters was investigated. The results indicate that ibuprofen oxidation was favored in the presence of Pd-PdO particles. The quantitative determination of ibuprofen was statistically analyzed and validated using HPLC method. The detection and quantification limits, specificity and precision were found to be acceptable. Finally, the developed method was successfully applied for ibuprofen determination in human blood samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Electrochemical determination of bisphenol A at ordered mesoporous carbon modified nano-carbon ionic liquid paste electrode.

    Science.gov (United States)

    Li, Yonghong; Zhai, Xiurong; Liu, Xinsheng; Wang, Ling; Liu, Herong; Wang, Haibo

    2016-02-01

    A simple bisphenol A (BPA) sensor was successfully fabricated based on ordered mesoporous carbon CMK-3 modified nano-carbon ionic liquid paste electrode (CMK-3/nano-CILPE). The nanostructure of CMK-3 and the surface morphologies of modified electrodes were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Electrochemical properties of the fabricated electrodes were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The fabricated sensor displayed excellent electroactivity towards bisphenol A using linear sweep voltammetry (LSV). Experimental conditions influencing the analytical performance of the modified electrode were optimized. Under optimal conditions, the oxidation peak current was proportional to BPA concentration in the range from 0.2 μM to 150 μM with a detection limit of 0.05 μM (S/N=3). This method was successfully used for determination of BPA leached from drinking bottle and plastic bag with good recoveries. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. Proton conductive montmorillonite-Nafion composite membranes for direct ethanol fuel cells

    International Nuclear Information System (INIS)

    Wu, Xiu-Wen; Wu, Nan; Shi, Chun-Qing; Zheng, Zhi-Yuan; Qi, Hong-Bin; Wang, Ya-Fang

    2016-01-01

    Highlights: • Composite membranes are prepared with different montmorillonites and nafion solution. • Proton conductivities of the composite membranes are between 36.0 mS/cm and 38.5 mS/cm. • Ethanol permeability is between 0.69 × 10"−"6 cm"2/s and 2.67 × 10"−"6 cm"2/s. • Water uptake is approximately 24.30 mass%. - Abstract: The preparation of Nafion membranes modified with montmorillonites is less studied, and most relative works mainly applied in direct methanol fuel cells, less in direct ethanol fuel cells. Organic/inorganic composite membranes are prepared with different montmorillonites (Ca-montmorillonite, Na-montmorillonite, K-montmorillonite, Mg-montmorillonite, and H-montmorillonite) and Nafion solution via casting method at 293 K in air, and with balance of their proton conductivity and ethanol permeability. The ethanol permeability and proton conductivity of the membranes are comparatively studied. The montmorillonites can well decrease the ethanol permeability of the membranes via inserted them in the membranes, while less decrease the proton conductivities of the membranes depending on the inserted amount and type of montmorillonites. The proton conductivities of the membranes are between 36.0 mS/cm and 38.5 mS/cm. The ethanol permeability of the membranes is between 0.69 × 10"−"6 cm"2/s and 2.67 × 10"−"6 cm"2/s.

  13. Modeling uranium(VI) adsorption onto montmorillonite under varying carbonate concentrations: A surface complexation model accounting for the spillover effect on surface potential

    Science.gov (United States)

    Tournassat, C.; Tinnacher, R. M.; Grangeon, S.; Davis, J. A.

    2018-01-01

    The prediction of U(VI) adsorption onto montmorillonite clay is confounded by the complexities of: (1) the montmorillonite structure in terms of adsorption sites on basal and edge surfaces, and the complex interactions between the electrical double layers at these surfaces, and (2) U(VI) solution speciation, which can include cationic, anionic and neutral species. Previous U(VI)-montmorillonite adsorption and modeling studies have typically expanded classical surface complexation modeling approaches, initially developed for simple oxides, to include both cation exchange and surface complexation reactions. However, previous models have not taken into account the unique characteristics of electrostatic surface potentials that occur at montmorillonite edge sites, where the electrostatic surface potential of basal plane cation exchange sites influences the surface potential of neighboring edge sites ('spillover' effect). A series of U(VI) - Na-montmorillonite batch adsorption experiments was conducted as a function of pH, with variable U(VI), Ca, and dissolved carbonate concentrations. Based on the experimental data, a new type of surface complexation model (SCM) was developed for montmorillonite, that specifically accounts for the spillover effect using the edge surface speciation model by Tournassat et al. (2016a). The SCM allows for a prediction of U(VI) adsorption under varying chemical conditions with a minimum number of fitting parameters, not only for our own experimental results, but also for a number of published data sets. The model agreed well with many of these datasets without introducing a second site type or including the formation of ternary U(VI)-carbonato surface complexes. The model predictions were greatly impacted by utilizing analytical measurements of dissolved inorganic carbon (DIC) concentrations in individual sample solutions rather than assuming solution equilibration with a specific partial pressure of CO2, even when the gas phase was

  14. Effect of mediator added to modified paste carbon electrodes with immobilized laccase from Aspergillus oryzae

    Directory of Open Access Journals (Sweden)

    Marcelo Silva Ferreira

    2015-05-01

    Full Text Available Carbon paste electrodes based on the immobilization of laccase from Aspergillus oryzae were developed and voltammetric measurements were performed to evaluate the amperometric response. The 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid diammonium salt  (ABTS functions as substrate and mediator for the laccase enzyme. Electrodes were modified  in two different conditions: without mediator (EPC/laccase and with mediator (EPC/laccase/ABTS. The addition of ABTS as a mediator increased eight-fold the amperometric response. The electrode was sensitive to pH variation with best response at pH 4.0. Studies on different concentrations of laccase and ABTS at different pH rates revealed that the composition 187 U mL-1 in laccase and 200 µL of ABTS obtained the highest amperometric response. The carbon paste electrode modified with ABTS proved to be a good base for the immobilization of the laccase enzyme. Moreover, it is easy to manufacture and inexpensive to produce a modified electrode with potential application in biosensors.

  15. Voltammetric sensor for electrochemical determination of the floral origin of honey based on a zinc oxide nanoparticle modified carbon paste electrode

    Directory of Open Access Journals (Sweden)

    K. Tiwari

    2018-04-01

    Full Text Available A new methodology based on cyclic voltammetry using a chemically modified electrode has been developed for the discrimination of the floral origin of honey. This method involves an electronic tongue with an electrochemical sensor made from a carbon paste (CPs electrode where zinc oxide (ZnO nanoparticles are used as an electroactive binder material. The bare CPs electrode is evaluated for comparison. The electrochemical response of the modified electrode in 50 samples of five different floral types of honey has been analysed by the cyclic voltammetric technique. The voltammograms of each floral variety of honey reflect the redox properties of the ZnO nanoparticles present inside the carbon paste matrix and are strongly influenced by the nectar source of honey. Thus, each type of honey provides a characteristic signal which is evaluated by using principal component analysis (PCA and an artificial neural network (ANN. The result of a PCA score plot of the transient responses obtained from the modified carbon paste electrode clearly shows discrimination among the different floral types of honey. The ANN model for floral classification of honey shows more than 90 % accuracy. These results indicate that the ZnO nanoparticles modified carbon paste (ZnO Nps modified CPs electrode can be a useful electrode for discrimination of honey samples from different floral origins.

  16. Effects of humidity and interlayer cations on the frictional strength of montmorillonite

    Science.gov (United States)

    Tetsuka, Hiroshi; Katayama, Ikuo; Sakuma, Hiroshi; Tamura, Kenji

    2018-04-01

    We developed a humidity control system in a biaxial friction testing machine to investigate the effect of relative humidity and interlayer cations on the frictional strength of montmorillonite. We carried out the frictional experiments on Na- and Ca-montmorillonite under controlled relative humidities (ca. 10, 30, 50, 70, and 90%) and at a constant temperature (95 °C). Our experimental results show that frictional strengths of both Na- and Ca-montmorillonite decrease systematically with increasing relative humidity. The friction coefficients of Na-montmorillonite decrease from 0.33 (at relative humidity of 10%) to 0.06 (at relative humidity of 93%) and those of Ca-montmorillonite decrease from 0.22 (at relative humidity of 11%) to 0.04 (at relative humidity of 91%). Our results also show that the frictional strength of Na-montmorillonite is higher than that of Ca-montmorillonite at a given relative humidity. These results reveal that the frictional strength of montmorillonite is sensitive to hydration state and interlayer cation species, suggesting that the strength of faults containing these clay minerals depends on the physical and chemical environment.[Figure not available: see fulltext.

  17. Mechanism of amitriptyline adsorption on Ca-montmorillonite (SAz-2)

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Po-Hsiang [Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Jiang, Wei-Teh, E-mail: atwtj@mail.ncku.edu.tw [Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Li, Zhaohui, E-mail: li@uwp.edu [Department of Geosciences, University of Wisconsin – Parkside, 900 Wood Road, Kenosha, WI 53144 (United States); Kuo, Chung-Yih [Department of Public Health, College of Health Care and Management, Chung Shan Medical University, No. 110, Sec. 1, Chien-kuo N Road, Taichung 40242, Taiwan (China); Jean, Jiin-Shuh [Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Chen, Wan-Ru [Department of Environmental Engineering, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Lv, Guocheng [School of Materials Science and Technology, China University of Geosciences, Beijing 100083 (China)

    2014-07-30

    Graphical abstract: XRD patterns to show AMI intercalation into SAz-2 vs. direct mixing of the same amount of AMI with SAz-2. - Highlights: • Ca-montmorillonite is proven to be an efficient adsorbent or sink for amitriptyline. • The high adsorption capacity is accompanied with intercalation into interlayers. • The adsorption is mainly governed by a cation exchange mechanism. • Horizontal mono- and bi-layer conformations occur at low and high adsorption levels. • The process is an endothermic physisorption at high adsorption levels. - Abstract: The uptake of amitriptyline (AMI) from aqueous environment by Ca-montmorillonite (SAz-2) was studied in a batch system under different physicochemical conditions. The adsorbent was characterized by X-ray diffraction and Fourier transform infrared (FTIR) analyses. The AMI adsorption on SAz-2 obeyed the Langmuir isotherm with a capacity of 330 mg/g (1.05 mmol/g) at pH 6–7. The adsorption kinetics was fast, almost reaching equilibrium in 2 h, and followed a pseudo-second-order kinetic model. Desorption of exchangeable cations correlated with the AMI adsorption well, indicating that cation exchange was the major mechanism. X-ray diffraction patterns showing significant expansions of the d{sub 0} {sub 0} {sub 1} spacing and characteristic FTIR band shifts toward higher frequencies after AMI adsorption onto SAz-2 indicated that the adsorbed AMI molecules were intercalated into the interlayers of the mineral. Thermodynamic parameters based on partitioning coefficients suggested that the AMI adsorption was an endothermic physisorption at high adsorption levels. At low and higher AMI adsorption levels, the intercalated AMI molecules take a horizontal monolayer and bilayer conformation, respectively. The higher adsorption capacity suggested that SAz-2 could be a good candidate to remove AMI from wastewater and would be an important environmental sink for the fate and transport of AMI in soils and groundwater.

  18. Mechanism of amitriptyline adsorption on Ca-montmorillonite (SAz-2)

    International Nuclear Information System (INIS)

    Chang, Po-Hsiang; Jiang, Wei-Teh; Li, Zhaohui; Kuo, Chung-Yih; Jean, Jiin-Shuh; Chen, Wan-Ru; Lv, Guocheng

    2014-01-01

    Graphical abstract: XRD patterns to show AMI intercalation into SAz-2 vs. direct mixing of the same amount of AMI with SAz-2. - Highlights: • Ca-montmorillonite is proven to be an efficient adsorbent or sink for amitriptyline. • The high adsorption capacity is accompanied with intercalation into interlayers. • The adsorption is mainly governed by a cation exchange mechanism. • Horizontal mono- and bi-layer conformations occur at low and high adsorption levels. • The process is an endothermic physisorption at high adsorption levels. - Abstract: The uptake of amitriptyline (AMI) from aqueous environment by Ca-montmorillonite (SAz-2) was studied in a batch system under different physicochemical conditions. The adsorbent was characterized by X-ray diffraction and Fourier transform infrared (FTIR) analyses. The AMI adsorption on SAz-2 obeyed the Langmuir isotherm with a capacity of 330 mg/g (1.05 mmol/g) at pH 6–7. The adsorption kinetics was fast, almost reaching equilibrium in 2 h, and followed a pseudo-second-order kinetic model. Desorption of exchangeable cations correlated with the AMI adsorption well, indicating that cation exchange was the major mechanism. X-ray diffraction patterns showing significant expansions of the d 0 0 1 spacing and characteristic FTIR band shifts toward higher frequencies after AMI adsorption onto SAz-2 indicated that the adsorbed AMI molecules were intercalated into the interlayers of the mineral. Thermodynamic parameters based on partitioning coefficients suggested that the AMI adsorption was an endothermic physisorption at high adsorption levels. At low and higher AMI adsorption levels, the intercalated AMI molecules take a horizontal monolayer and bilayer conformation, respectively. The higher adsorption capacity suggested that SAz-2 could be a good candidate to remove AMI from wastewater and would be an important environmental sink for the fate and transport of AMI in soils and groundwater

  19. Proton conductive montmorillonite-Nafion composite membranes for direct ethanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xiu-Wen, E-mail: wuxw2008@163.com [School of Science, China University of Geosciences, Beijing 100083 (China); National Laboratory of Mineral Materials, China University of Geosciences, Beijing 100083 (China); Wu, Nan; Shi, Chun-Qing; Zheng, Zhi-Yuan; Qi, Hong-Bin; Wang, Ya-Fang [School of Science, China University of Geosciences, Beijing 100083 (China)

    2016-12-01

    Highlights: • Composite membranes are prepared with different montmorillonites and nafion solution. • Proton conductivities of the composite membranes are between 36.0 mS/cm and 38.5 mS/cm. • Ethanol permeability is between 0.69 × 10{sup −6} cm{sup 2}/s and 2.67 × 10{sup −6} cm{sup 2}/s. • Water uptake is approximately 24.30 mass%. - Abstract: The preparation of Nafion membranes modified with montmorillonites is less studied, and most relative works mainly applied in direct methanol fuel cells, less in direct ethanol fuel cells. Organic/inorganic composite membranes are prepared with different montmorillonites (Ca-montmorillonite, Na-montmorillonite, K-montmorillonite, Mg-montmorillonite, and H-montmorillonite) and Nafion solution via casting method at 293 K in air, and with balance of their proton conductivity and ethanol permeability. The ethanol permeability and proton conductivity of the membranes are comparatively studied. The montmorillonites can well decrease the ethanol permeability of the membranes via inserted them in the membranes, while less decrease the proton conductivities of the membranes depending on the inserted amount and type of montmorillonites. The proton conductivities of the membranes are between 36.0 mS/cm and 38.5 mS/cm. The ethanol permeability of the membranes is between 0.69 × 10{sup −6} cm{sup 2}/s and 2.67 × 10{sup −6} cm{sup 2}/s.

  20. 1-ethanone modified carbon paste electrode

    African Journals Online (AJOL)

    a

    7.00) in cyclic voltammetry, the oxidation of L-cysteic acid at the surface of 4FEPEMCPE is occurred at a potential about 220 mV less positive than that an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, α, and catalytic reaction rate constant, K/ h, were also determined using.

  1. Nanomodified Carbon/Carbon Composites for Intermediate Temperature

    Science.gov (United States)

    2007-08-31

    7] Properties Values Appearance Light yellow liquid (material is waxy at room temperature) Specific Gravity 1.245 Ionic Cl (ppm) ᝺ Ionic Na and K...and several types of nanoparticles: chemically modified montmorillonite (MMT) organoclays, polyhedral oligomeric silsesquioxanes (POSS®), carbon...montmorillonite (MMT) organoclays, carbon nanofibers, polyhedral oligomeric silsesquioxanes (POSS®), nanosilica, nano- silicon carbide (n-SiC), and

  2. Molecular Dynamics Simulations of Carbon Dioxide, Methane, and Their Mixture in Montmorillonite Clay Hydrates

    KAUST Repository

    Kadoura, Ahmad Salim; Nair, Arun Kumar Narayanan; Sun, Shuyu

    2016-01-01

    Molecular dynamics simulations were carried out to study the structural and transport properties of carbon dioxide, methane, and their mixture at 298.15 K in Na-montmorillonite clay in the presence of water. The simulations show that, the self-diffusion coefficients of pure CO2 and CH4 molecules in the interlayers of Na-montmorillonite decrease as their loading increases, possibly because of steric hindrance. The diffusion of CO2 in the interlayers of Na-montmorillonite, at constant loading of CO2, is not significantly affected by CH4 for the investigated CO2/CH4 mixture compositions. We attribute this to the preferential adsorption of CO2 over CH4 in Na-montmorillonite. While the presence of adsorbed CO2 molecules, at constant loading of CH4, very significantly reduces the self-diffusion coefficients of CH4, and relatively larger decrease in those diffusion coefficients are obtained at higher loadings. The preferential adsorption of CO2 molecules to the clay surface screens those possible attractive surface sites for CH4. The competition between screening and steric effects leads to a very slight decrease in the diffusion coefficients of CH4 molecules at low CO2 loadings. The steric hindrance effect, however, becomes much more significant at higher CO2 loadings and the diffusion coefficients of methane molecules significantly decrease. Our simulations also indicate that, similar effects of water on both carbon dioxide and methane, increase with increasing water concentration, at constant loadings of CO2 and CH4 in the interlayers of Na-montmorillonite. Our results could be useful, because of the significance of shale gas exploitation and carbon dioxide storage.

  3. Molecular Dynamics Simulations of Carbon Dioxide, Methane, and Their Mixture in Montmorillonite Clay Hydrates

    KAUST Repository

    Kadoura, Ahmad Salim

    2016-05-26

    Molecular dynamics simulations were carried out to study the structural and transport properties of carbon dioxide, methane, and their mixture at 298.15 K in Na-montmorillonite clay in the presence of water. The simulations show that, the self-diffusion coefficients of pure CO2 and CH4 molecules in the interlayers of Na-montmorillonite decrease as their loading increases, possibly because of steric hindrance. The diffusion of CO2 in the interlayers of Na-montmorillonite, at constant loading of CO2, is not significantly affected by CH4 for the investigated CO2/CH4 mixture compositions. We attribute this to the preferential adsorption of CO2 over CH4 in Na-montmorillonite. While the presence of adsorbed CO2 molecules, at constant loading of CH4, very significantly reduces the self-diffusion coefficients of CH4, and relatively larger decrease in those diffusion coefficients are obtained at higher loadings. The preferential adsorption of CO2 molecules to the clay surface screens those possible attractive surface sites for CH4. The competition between screening and steric effects leads to a very slight decrease in the diffusion coefficients of CH4 molecules at low CO2 loadings. The steric hindrance effect, however, becomes much more significant at higher CO2 loadings and the diffusion coefficients of methane molecules significantly decrease. Our simulations also indicate that, similar effects of water on both carbon dioxide and methane, increase with increasing water concentration, at constant loadings of CO2 and CH4 in the interlayers of Na-montmorillonite. Our results could be useful, because of the significance of shale gas exploitation and carbon dioxide storage.

  4. Molecular Simulation Study of Montmorillonite in Contact with Variably Wet Supercritical Carbon Dioxide

    KAUST Repository

    Kadoura, Ahmad Salim; Nair, Arun Kumar Narayanan; Sun, Shuyu

    2017-01-01

    We perform grand canonical Monte Carlo simulations to study the detailed molecular mechanism of intercalation behavior of CO2 in Na-, Ca-, and Mg- montmorillonite exposed to variably hydrated supercritical CO2 at 323.15 K and 90 bar, The simulations

  5. Synthesis and utilization of poly (methylmethacrylate) nanocomposites based on modified montmorillonite

    OpenAIRE

    Youssef, Ahmed M.; Malhat, F.M.; Abdel Hakim, A.A.; Dekany, Imre

    2015-01-01

    Poly (methylmethacrylate) nanocomposite was prepared via in-situ emulsion polymerization (PMMA/Mt-CTA). The modified montmorillonite (Mt-CTA) is used as hosts for the preparation of poly (methylmethacrylate) nanocomposites with basal distance 1.95 nm. Moreover, exfoliated nanocomposite was characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC). The fashioned nanocomposites exhibited bett...

  6. Electrochemical detection of phenolic estrogenic compounds at clay modified carbon paste electrode

    Science.gov (United States)

    Belkamssa, N.; Ouattara, L.; Kawachi, A.; Tsujimura, M.; Isoda, H.; Chtaini, A.; Ksibi, M.

    2015-04-01

    A simple and sensitive electroanalytical method was developed to determine the Endocrine Disrupting chemical 4-tert-octylphenol on clay modified carbon paste electrode (Clay/CPE). The electrochemical response of the proposed electrode was studied by means of cyclic and square wave voltammetry. It has found that the oxidation of 4-tert-octylphenol on the clay/CPE displayed a well-defined oxidation peak. Under these optimal conditions, a linear relation between concentrations of 4-tert-octylphenol current response was obtained over range of 7.26×10-6 to 3.87×10-7 with a detection and quantification limit of 9.2×10-7 M and 3.06×10-6 M, respectively. The correlation coefficient is 0.9963. The modified electrode showed suitable sensitivity, high stability and an accurate detection of 4-tert-octylphenol. The modified electrode also relevant suitable selectivity for various phenolic estrogenic compounds.

  7. Soil-modified carbon paste electrode: a useful tool in environmental assessment of heavy metal ion binding interactions.

    Science.gov (United States)

    Svegl, I G; Ogorevc, B

    2000-08-01

    Carbon paste electrodes (CPEs) modified with different soils in their native form were prepared to create a soil-like solid phase suitable for application in studies of heavy metal ion uptake and binding interactions. The preparation of CPEs modified with five different soils was examined and their heavy metal ion uptake behavior investigated using a model Cu(II) aqueous solution. Metal ions were accumulated under open circuit conditions and were determined after a medium exchange using differential pulse anodic stripping voltammetry, applying preelectrolysis at -0.7 V. The soil-modified CPE accumulation behavior, including the linearity of the current response versus Cu(II) concentration, the influence of the pH on the solution, and the uptake kinetics, was thoroughly investigated. The correlation between the soil-modified CPE uptake capability and the standard soil parameters, such as ion exchange capacity, soil pH, organic matter and clay content, were evaluated for all five examined soils. The influence of selected endogenous cations (K(I), Ca(II), Fe(III)) on the transfer of Cu(II) ions from a solution to the simulated soil solid phase was examined and is discussed. Preliminary examinations of the soil-modified CPE uptake behavior with some exogenous heavy metal ions of strong environmental interest (Pb(II), Hg(II), Cd(II) and Ag(I)) are also presented. This work demonstrates some attractive possibilities for the application of a soil-modified CPE in studying soil-heavy metal ion binding interactions, with a further potential use as a new environmental sensor appropriate for fist on-site testing of polluted soils.

  8. Adsorption-regeneration by heterogeneous Fenton process using modified carbon and clay materials for removal of indigo blue.

    Science.gov (United States)

    Almazán-Sánchez, Perla Tatiana; Solache-Ríos, Marcos J; Linares-Hernández, Ivonne; Martínez-Miranda, Verónica

    2016-01-01

    Indigo blue dye is mainly used in dyeing of denim clothes and its presence in water bodies could have adverse effects on the aquatic system; for this reason, the objective of this study was to promote the removal of indigo blue dye from aqueous solutions by iron and copper electrochemically modified clay and activated carbon and the saturated materials were regenerated by a Fenton-like process. Montmorillonite clay was modified at pH 2 and 7; activated carbon at pH 2 and pH of the system. The elemental X-ray dispersive spectroscopy analysis showed that the optimum pH for modification of montmorillonite with iron and copper was 7 and for activated carbon was 2. The dye used in this work was characterized by infrared. Unmodified and modified clay samples showed the highest removal efficiencies of the dye (90-100%) in the pH interval from 2 to 10 whereas the removal efficiencies decrease as pH increases for samples modified at pH 2. Unmodified clay and copper-modified activated carbon at pH 2 were the most efficient activated materials for the removal of the dye. The adsorption kinetics data of all materials were best adjusted to the pseudo-second-order model, indicating a chemisorption mechanism and the adsorption isotherms data showed that the materials have a heterogeneous surface. The iron-modified clay could be regenerated by a photo-Fenton-like process through four adsorption-regeneration cycles, with 90% removal efficiency.

  9. Diffusion and sorption of neptunium(V) in compacted montmorillonite: effects of carbonate and salinity

    International Nuclear Information System (INIS)

    Tachi, Y.; Yotsuji, K.; Suyama, T.; Seida, Y.; Yui, M.; Nakazawa, T.; Yamada, N.; Ochs, M.

    2010-01-01

    Diffusion and sorption of radionuclides in compacted bentonite/montmorillonite are key processes in the safe geological disposal of radioactive waste. In this study, the effects of carbonate and salinity on neptunium(V) diffusion and sorption in compacted sodium montmorillonite were investigated by experimental and modeling approaches. Effective diffusion coefficients (D e ) and distribution coefficients (K d ) of 237 Np(V) in sodium montmorillonite compacted to a dry density of 800 kg m -3 were measured under four chemical conditions with different salinities (0.05/0.5 M NaCl) and carbonate concentrations (0.0.01 M NaHCO 3 ). D e values for carbonate-free conditions were of the order of 10 -10 -10 -11 m 2 s -1 and decreased as salinity increased, and those for carbonate conditions were of the order of 10 -11 -10 -12 m 2 s -1 and showed the opposite dependence. Diffusion-derived K d values for carbonate-free conditions were higher by one order of magnitude than those for carbonate conditions. Diffusion and sorption behaviors were interpreted based on mechanistic models by coupling thermodynamic aqueous speciation, thermodynamic sorption model (TSM) based on ion exchange, and surface complexation reactions, and a diffusion model based on electrical double layer (EDL) theory in homogeneous narrow pores. The model predicted the experimentally observed tendency of D e and K d qualitatively, as a result of the following mechanisms; 1) the dominant aqueous species are NpO 2 + and NpO 2 CO 3 - for carbonate-free and carbonate conditions, respectively, 2) the effects of cation excess and anion exclusion result in opposite tendencies of D e for salinity, 3) higher carbonate in solution inhibits sorption due to the formation of carbonate complexes. (orig.)

  10. Exfoliated polypyrrole-organically modified montmorillonite clay nanocomposite as a potential adsorbent for Cr (VI) removal

    CSIR Research Space (South Africa)

    Setshedi, KZ

    2013-01-01

    Full Text Available Exfoliated polypyrrole-organically modified montmorillonite clay nanocomposite (PPy OMMT NC), was prepared as a potential adsorbent, via in situ polymerization of pyrrole monomer for adsorption of toxic Cr(VI) from aqueous solution. The WAXD...

  11. Adsorption of Carbon Dioxide, Methane, and Their Mixtute by Montmorillonite in the Presence of Water

    KAUST Repository

    Kadoura, Ahmad Salim

    2016-01-16

    Using grand canonical Monte Carlo (GCMC) simulations, we study the adsorption behavior of CH4, CO2, and their mixture at 298.15 K and pressures up to 50 bar in Na-, Cs-, and Ca-montmorillonite clays in the presence of water. Montmorillonite clays in the presence of preadsorbed water, preferentially adsorb CO2 over CH4 during both pure component and mixture adsorption. The atomistic model we have used, gives good agreement with available single-component experimental adsorption isotherms, for CH4 and CO2 molecules adsorbed onto montmorillonite clays in the presence of water. We observe the general trend that the presence of increasing preadsorbed water content in the clay interlayers, reduced adsorption amounts of pure CH4 and CO2 molecules. With a relatively large basal spacing (d= 30 Å), the favorability of adsorption of CO2 by montmorillonite at relatively low pressures and intermediate water contents has been demonstrated using simulations. GCMC simulation is also used to assess the effect of water on the adsorption of N2/CH4, H2 S/CH4, CO2/N2, and CO2/H2 S binary mixtures in Na-montmorillonite clay. The ideal adsorbed solution theory is shown to agree well with the observed adsorption capacities and selectivities of mixtures in Na-montmorillonite clay.

  12. Comparative investigation on electrochemical behavior of hydroquinone at carbon ionic liquid electrode, ionic liquid modified carbon paste electrode and carbon paste electrode

    International Nuclear Information System (INIS)

    Zhang, Ya; Zheng, Jian Bin

    2007-01-01

    Ionic liquid, 1-heptyl-3-methylimidazolium hexafluorophosphate (HMIMPF 6 ), has been used to fabricate two new electrodes, carbon ionic liquid electrode (CILE) and ionic liquid modified carbon paste electrode (IL/CPE), using graphite powder mixed with HMIMPF 6 or the mixture of HMIMPF 6 /paraffin liquid as the binder, respectively. The electrochemical behaviors of hydroquinone at the CILE, the IL/CPE and the CPE were investigated in phosphate buffer solution. At all these electrodes, hydroquinone showed a pair of redox peaks. The order of the current response and the standard rate constant of hydroquinone at these electrodes were as follows: CILE > IL/CPE > CPE, while the peak-to-peak potential separation was in an opposite sequence: CILE < IL/CPE < CPE. The results show the superiority of CILE to IL/CPE and CPE, and IL/CPE to CPE in terms of promoting electron transfer, improving reversibility and enhancing sensitivity. The CILE was chosen as working electrode to determine hydroquinone by differential pulse voltammetry, which can be used for sensitive, simple and rapid determination of hydroquinone in medicated skin cosmetic cream

  13. Synthesis and Optical Properties of MnS–ZnS and MnS–CdS Nanoparticles in Montmorillonite.

    Science.gov (United States)

    Kabilaphat, Jirabhorn; Poosimma, Poonsuk; Khaorapapong, Nithima; Intachai, Sonchai; Ogawa, Makoto

    2017-02-01

    The incorporation of metal sulfide mixture, manganese sulfide and zinc sulfide (MnS–ZnS) or manganese sulfide and cadmium sulfide (MnS–CdS), in two types of montmorillonites (sodium montmorillonite and cetyltrimethylammonium modified montmorillonite) was investigated. The hybrids were characterized by powder X-ray diffraction, thermogravimetric-differential thermal analysis, transmission electron microscopy (TEM), and Raman, UV-visible and photoluminescence spectroscopies. The experimental evidences such as the expansion of the interlayer spaces and the presence of the absorption and photoluminescence due to MnS, ZnS and/or CdS revealed that the mixed metal sulfides formed in the interlayer space of montmorillonites. TEM images of the hybrids showed diskor plate-shaped nanoparticles with a mean diameter of ca. 2 nm. The increase of the luminescence intensities of the hybrids was assumed to be caused by quantum confinement effect in the interlayer space of montmorillonite.

  14. Simultaneous determination of hydroquinone and catechol at gold nanoparticles mesoporous silica modified carbon paste electrode

    Energy Technology Data Exchange (ETDEWEB)

    Tashkhourian, J., E-mail: tashkhourian@susc.ac.ir [Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71456 (Iran, Islamic Republic of); Daneshi, M.; Nami-Ana, F. [Department of Chemistry, College of Sciences, Shiraz University, Shiraz 71456 (Iran, Islamic Republic of); Behbahani, M.; Bagheri, A. [Department of Chemistry, Shahid Beheshti University, G.C., Evin, Tehran (Iran, Islamic Republic of)

    2016-11-15

    Highlights: • An electrochemical sensor based on gold nanoparticles mesoporous silica modified carbon paste electrode was developed. • The electrode provides an accessible surface for simultaneous determination of hydroquinone and catechol. • Hydroquinone and catechol are highly toxic to both environment and human even at very low concentrations. - Abstract: A new electrochemical sensor based on gold nanoparticles mesoporous silica modified carbon paste electrode (AuNPs-MPS) was developed for simultaneous determination of hydroquinone and catechol. Morphology and structure of the AuNPs-MPS were characterized by transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The electrochemical behavior of hydroquinone and catechol were investigated using square wave voltammetry and the results indicate that the electrochemical responses are improved significantly at the modified electrode. The observed oxidative peaks separation of about 120 mV made possible the simultaneous determination of hydroquinone and catechol in their binary-mixture. Under the optimized condition, a linear dynamic range of 10.0 μM–1.0 mM range for hydroquinone with the detection limit of 1.2 μM and from 30.0 μM–1.0 mM for catechol with the detection limit of 1.1 μM were obtained. The applicability of the method was demonstrated by the recovery studies of hydroquinone and catechol in spiked tap water samples.

  15. Electrochemical detection of carbidopa using a ferrocene-modified carbon nanotube paste electrode

    Directory of Open Access Journals (Sweden)

    FATEMEH KARIMI

    2009-12-01

    Full Text Available A chemically modified carbon paste electrode (MCPE containing ferrocene (FC and carbon nanotubes (CNT was constructed. The electrochemical behavior and stability of the MCPE were investigated by cyclic voltammetry. The electrocatalytic activity of the MCPE was investigated and it showed good characteristics for the oxidation of carbidopa (CD in phosphate buffer solution (PBS. A linear concentration range of 5 to 600 μM CD, with a detection limit of 3.6±0.17 μM CD, was obtained. The diffusion coefficient of CD and the transfer coefficient ( were also determined. The MCPE showed good reproducibility, remarkable long-term stability and especially good surface renewability by simple mechanical polishing. The results showed that this electrode could be used as an electrochemical sensor for the determination of CD in real samples, such as urine samples.

  16. Potentiometric stripping analysis of antimony based on carbon paste electrode modified with hexathia crown ether and rice husk

    International Nuclear Information System (INIS)

    Gadhari, Nayan S.; Sanghavi, Bankim J.; Srivastava, Ashwini K.

    2011-01-01

    Highlights: → Potentiometric stripping analysis (PSA) employed for the determination of antimony. → Hexathia-18C6 and rice husk modified carbon paste electrode developed for the analysis. → Lowest detection limit obtained for the determination of Sb(III) using PSA. → Analysis of Sb in pharmaceutical formulations, human hair, blood serum, urine and sea water. → Rice husk used as a modifier for the first time in electrochemistry. - Abstract: An electrochemical method based on potentiometric stripping analysis (PSA) employing a hexathia 18C6 (HT18C6) and rice husk (RH) modified carbon paste electrode (HT18C6-RH-CPE) has been proposed for the subnanomolar determination of antimony. The characterization of the electrode surface has been carried out by means of scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and chronocoulometry. By employing HT18C6-RH-CPE, a 12-fold enhancement in the PSA signal (dt/dE) was observed as compared to plain carbon paste electrode (PCPE). Under the optimized conditions, dt/dE (s V -1 ) was proportional to the Sb(III) concentration in the range of 1.42 x 10 -8 to 6.89 x 10 -11 M (r = 0.9944) with the detection limit (S/N = 3) of 2.11 x 10 -11 M. The practical analytical utilities of the modified electrode were demonstrated by the determination of antimony in pharmaceutical formulations, human hair, sea water, urine and blood serum samples. The prepared modified electrode showed several advantages, such as simple preparation method, high sensitivity, very low detection limit and excellent reproducibility. Moreover, the results obtained for antimony analysis in commercial and real samples using HT18C6-RH-CPE and those obtained by inductively coupled plasma-atomic emission spectrometry (ICP-AES) are in agreement at the 95% confidence level.

  17. Potentiometric stripping analysis of antimony based on carbon paste electrode modified with hexathia crown ether and rice husk

    Energy Technology Data Exchange (ETDEWEB)

    Gadhari, Nayan S.; Sanghavi, Bankim J. [Department of Chemistry, University of Mumbai, Vidyanagari, Santacruz (East), Mumbai 400098 (India); Srivastava, Ashwini K., E-mail: aksrivastava@chem.mu.ac.in [Department of Chemistry, University of Mumbai, Vidyanagari, Santacruz (East), Mumbai 400098 (India)

    2011-10-03

    Highlights: {yields} Potentiometric stripping analysis (PSA) employed for the determination of antimony. {yields} Hexathia-18C6 and rice husk modified carbon paste electrode developed for the analysis. {yields} Lowest detection limit obtained for the determination of Sb(III) using PSA. {yields} Analysis of Sb in pharmaceutical formulations, human hair, blood serum, urine and sea water. {yields} Rice husk used as a modifier for the first time in electrochemistry. - Abstract: An electrochemical method based on potentiometric stripping analysis (PSA) employing a hexathia 18C6 (HT18C6) and rice husk (RH) modified carbon paste electrode (HT18C6-RH-CPE) has been proposed for the subnanomolar determination of antimony. The characterization of the electrode surface has been carried out by means of scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy and chronocoulometry. By employing HT18C6-RH-CPE, a 12-fold enhancement in the PSA signal (dt/dE) was observed as compared to plain carbon paste electrode (PCPE). Under the optimized conditions, dt/dE (s V{sup -1}) was proportional to the Sb(III) concentration in the range of 1.42 x 10{sup -8} to 6.89 x 10{sup -11} M (r = 0.9944) with the detection limit (S/N = 3) of 2.11 x 10{sup -11} M. The practical analytical utilities of the modified electrode were demonstrated by the determination of antimony in pharmaceutical formulations, human hair, sea water, urine and blood serum samples. The prepared modified electrode showed several advantages, such as simple preparation method, high sensitivity, very low detection limit and excellent reproducibility. Moreover, the results obtained for antimony analysis in commercial and real samples using HT18C6-RH-CPE and those obtained by inductively coupled plasma-atomic emission spectrometry (ICP-AES) are in agreement at the 95% confidence level.

  18. Carbon paste electrode incorporating multi-walled carbon nanotube ...

    Indian Academy of Sciences (India)

    The preparation and electrochemical performance of the carbon nanotube paste electrode modified with ferrocene (FCMCNPE) was investigated for electrocatalytic behaviour toward oxidation of -acetyl--cysteine (NAC) in the presence of tryptophan (Trp) using cyclic voltammetry (CV) and differential pulse voltammetry ...

  19. Carbon paste electrode modified with silver thimerosal for the potentiometric flow injection analysis of silver(I)

    Energy Technology Data Exchange (ETDEWEB)

    Ibrahim, Hosny [Chemistry Department, Faculty of Science, Cairo University, Cairo (Egypt)]. E-mail: dr_hosny@yahoo.com

    2005-07-27

    The utility of carbon paste electrode modified with silver ethylmercurythiosalicylate (silver thimerosal) in both static mode and flow injection analysis (FIA) is demonstrated. The electrode was fully characterized in terms of composition, response time, thermal stability, usable pH and ionic strength ranges. It has been shown that diisononyl phthalate (DINP) acts as more suitable solvent mediator for preparation of the electrode, which exhibits linear response range to Ag(I) extending from 5.0 x 10{sup -7} to 1.0 x 10{sup -3} M with detection limit of 2.5 x 10{sup -7} M and Nernstian slope of 59.3 {+-} 1.0 mV/decade. The proposed chemically modified carbon paste electrode shows a very good selectivity for Ag(I) over a wide variety of metal ions and successfully used for the determination of the silver content of silver sulphadiazine (burning cream) and developed radiological films. The electrode was also used as an indicator electrode in the potentiometric titration of thiopental and thimerosal with AgNO{sub 3}.

  20. Role of heat on the development of electrochemical sensors on bare and modified Co3O4/CuO composite nanopowder carbon paste electrodes.

    Science.gov (United States)

    Kumar, Mohan; Kumara Swamy, B E

    2016-01-01

    The Co3O4/CuO composite nanopowder (NP) was synthesized by a mechanochemical method and characterized by using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The synthesized Co3O4/CuO NP was used as a modified carbon paste electrode (MCPE) and further the bare carbon paste and Co3O4/CuO NP modified carbon paste was heated at different temperatures (100, 150, 200 and 250 °C) for 10 min. The Co3O4/CuO NP MCPE was used to study the consequences of scan rate and dopamine concentration. Furthermore the preheated modified electrodes were used to study the electrochemical response to dopamine (DA), ascorbic acid (AA) and uric acid (UA). Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Sorption of triclosan onto activated carbon, kaolinite and montmorillonite: effects of pH, ionic strength, and humic acid.

    Science.gov (United States)

    Behera, Shishir Kumar; Oh, Seok-Young; Park, Hung-Suck

    2010-07-15

    Sorption of triclosan on three sorbents, viz., activated carbon, kaolinite and montmorillonite was studied as a function of pH, ionic strength and humic acid (HA) concentration through controlled batch experiments. Triclosan sorption was found to be higher in the acidic pH range, as varying pH showed significant influence on the surface charge of the sorbents and degree of ionization of the sorbate. Sorption capacity of the sorbents increased with an increase in the ionic strength of solution. At low pH (pH 3), the overall increase in triclosan sorption was 1.2, approximately 4 and 3.5 times, respectively for activated carbon, kaolinite and montmorillonite when ionic strength was increased from 1x10(-3) to 5x10(-1) M. Triclosan sorption onto activated carbon decreased from 31.4 to 10.6 mg g(-1) by increasing the HA concentration to 200 mg C L(-1). However, during sorption onto kaolinite and montmorillonite, the effect of HA was very complex probably due to (i) hydrophobicity (log K(ow)=4.76) of triclosan; and (ii) complexation of HA with triclosan. Though triclosan sorption onto activated carbon is higher, the potential of kaolinite and montmorillonite in controlling the transport of triclosan in subsurface environment can still be appreciable. 2010 Elsevier B.V. All rights reserved.

  2. Role of uniform pore structure and high positive charges in the arsenate adsorption performance of Al13-modified montmorillonite

    International Nuclear Information System (INIS)

    Zhao, Shou; Feng, Chenghong; Huang, Xiangning; Li, Baohua; Niu, Junfeng; Shen, Zhenyao

    2012-01-01

    Highlights: ► Al 13 modification changes As(V) sorption mechanism of montmorillonites. ► Intercalated ion charges mainly affects As(V) adsorption kinetics. ► Uniform pore structure exhibit more excellent As(V) adsorption performance. - Abstract: Four modified montmorillonite adsorbents with varied Al 13 contents (i.e., Na-Mont, AC-Mont, PAC 20 -Mont, and Al 13 -Mont) were synthesized and characterized by N 2 adsorption/desorption, X-ray diffraction, and Fourier-transform infrared analyses. The arsenate adsorption performance of the four adsorbents were also investigated to determine the role of intercalated Al 13 , especially its high purity, high positive charge (+7), and special Keggin structure. With increased Al 13 content, the physicochemical properties (e.g., surface area, structural uniformity, basal spacing, and pore volume) and adsorption performance of the modified montmorillonites were significantly but disproportionately improved. The adsorption data well fitted the Freundlich and Redlich–Peterson isotherm model, whereas the kinetic data better correlated with the pseudo-second-order kinetic model. The arsenate sorption mechanism of the montmorillonites changed from physical to chemisorption after intercalation with Al 13 . Increasing charges of the intercalated ions enhanced the arsenate adsorption kinetics, but had minimal effect on the structural changes of the montmorillonites. The uniform pore structure formed by intercalation with high-purity Al 13 greatly enhanced the pore diffusion and adsorption rate of arsenate, resulting in the high adsorption performance of Al 13 -Mont.

  3. Voltammetric determination of carbidopa and folic acid using a modified carbon nanotubes paste electrode

    Directory of Open Access Journals (Sweden)

    Keshtkar Nasrin

    2015-01-01

    Full Text Available A novel electrochemical sensor for the selective and sensitive detection of carbidopa in presence of large excess of folic acid at physiological pH was developed by the bulk modification of carbon paste electrode (CPE with carbon nanotubes (CNTs and vinylferrocene. Large peak separation, good sensitivity and stability allow this modified electrode to analyze carbidopa individually and simultaneously along with folic acid. Applying square wave voltammetry (SWV, a linear dynamic range of 1.0×10-6- 7.0×10-4 M with detection limit of 2.0×10-7 M was obtained for carbidopa. Finally, the proposed method was applied to the determination of carbidopa and folic acid in urine sample.

  4. Effect of organo-modified montmorillonite on poly(butylene succinate/poly(butylene adipate-co-terephthalate nanocomposites

    Directory of Open Access Journals (Sweden)

    2010-07-01

    Full Text Available The composite material based on poly(butylene succinate (PBS, poly(butylene adipate-co-terephthalate (PBAT and organo-modified montmorillonite (OMMT were prepared by melt blending technique and characterized. Sodium montmorillonite (Na-MMT was successfully modified by octadecylammonium (ODA and dimethyldioctadecylammonium (DDOA salts to become OMMT through cation exchange technique which is shown by the increase of basal spacing of clay by XRD. The addition of the OMMT to the PBS/PBAT blends produced nanocomposites which is proved by XRD and TEM. Tensile tests showed increase in tensile strength and modulus which is attributed to the existence of strong interactions between PBS/PBAT and clay, particularly with OMMT. Highest tensile strength of nanocomposite was observed at 1 wt% of OMMT incorporated. TGA study showed that the thermal stability of the blend increased after the addition of clays. SEM micrographs of the fracture surfaces show that the morphology of the blend becomes homogeneous and smoother with presence of OMMT.

  5. Role of heat on the development of electrochemical sensors on bare and modified Co{sub 3}O{sub 4}/CuO composite nanopowder carbon paste electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Mohan; Kumara Swamy, B.E., E-mail: kumaraswamy21@yahoo.com

    2016-01-01

    The Co{sub 3}O{sub 4}/CuO composite nanopowder (NP) was synthesized by a mechanochemical method and characterized by using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The synthesized Co{sub 3}O{sub 4}/CuO NP was used as a modified carbon paste electrode (MCPE) and further the bare carbon paste and Co{sub 3}O{sub 4}/CuO NP modified carbon paste was heated at different temperatures (100, 150, 200 and 250 °C) for 10 min. The Co{sub 3}O{sub 4}/CuO NP MCPE was used to study the consequences of scan rate and dopamine concentration. Furthermore the preheated modified electrodes were used to study the electrochemical response to dopamine (DA), ascorbic acid (AA) and uric acid (UA). - Highlights: • Co{sub 3}O{sub 4}/CuO composite nanopowders (NPs) are prepared by the mechanochemical method. • Co{sub 3}O{sub 4}/CuO was used as a modified electrode for detection of DA, AA and UA. • The role of temperature on the sensor development was studied. • The modified carbon paste electrode shows good sensitivity to DA and UA.

  6. Rhodium-Prussian Blue modified carbon paste electrode (Rh-PBMCPE for amperometric detection of hydrogen peroxide

    Directory of Open Access Journals (Sweden)

    Ivama Viviane Midori

    2003-01-01

    Full Text Available Prussian Blue was deposited at carbon paste electrode surface from a solution containing 2.0 x 10-3 mol L-1 K3[Fe(CN6], 3.0 x 10-3 mol L-1 FeCl3 and 1.0 x 10-2 mol L-1 HCl using two controlled potentials. To improve the stability of the modified electrode it was 50 times cycled in a solution containing 1.0 x 10-3 mol L-1 RhCl3, 0.50 mol L-1 KCl and 0.010 mol L-1 HCl in the potential range from - 0.40 V to 0.60 V at 60 mV s-1. The Rh - Prussian Blue carbon paste modified electrode (Rh-PBMCPE showed good stability during amperometric catalytic determination of H2O2 at 0.040 V, without ascorbic and uric acids interferences. The current changed linearly with H2O2 concentrations in the range of 5.0 x 10-5 - 8.6 x 10-4 mol L-1. The estimated detection limit was 2.8 x 10-5 mol L-1 with sensibility changing from 1.32 to 0.96 A mol-1 L cm-2 along five days (180 determinations.

  7. Electrochemical behavior of an anticancer drug 5-fluorouracil at methylene blue modified carbon paste electrode

    International Nuclear Information System (INIS)

    Bukkitgar, Shikandar D.; Shetti, Nagaraj P.

    2016-01-01

    A novel sensor for the determination of 5-fluorouracil was constructed by electrochemical deposition of methylene blue on surface of carbon paste electrode. The electrode surface morphology was studied using Atomic force microscopy and XRD. The electrochemical activity of modified electrode was characterized using cyclic voltammetry and differential pulse method. The developed sensor shows impressive enlargement in sensitivity of 5-fluorouracil determination. The peak currents obtained from differential pulse voltammetry was linear with concentration of 5-fluorouracil in the range 4 × 10 −5 –1 × 10 −7 M and detection limit and quantification limit were calculated to be 2.04 nM and 6.18 nM respectively. Further, the sensor was successfully applied in pharmaceutical and biological fluid sample analysis. - Highlights: • Electrochemical oxidation of 5-fluorouracil has been investigated for first time at methylene blue modified carbon paste electrode • The electrode process was irreversible and diffusion controlled • Probable electrochemical mechanism was proposed which involved two proton and two electron transfer reaction • The LOD and LOQ values were calculated to be 2.04 nM and 6.18 nM, respectively, with good selectivity and sensitivity. • Proposed method was applied to 5-Fluorouracil determination in pharmaceutical and spiked human urine samples

  8. Facile preparation of poly(methylene blue) modified carbon paste electrode for the detection and quantification of catechin

    Energy Technology Data Exchange (ETDEWEB)

    Manasa, G [Electrochemistry Research Group, Department of Chemistry, St. Joseph' s College, Lalbagh Road, Bangalore, 560027, Karnataka (India); Mascarenhas, Ronald J, E-mail: ronaldmasc2311@yahoo.co.in [Electrochemistry Research Group, Department of Chemistry, St. Joseph' s College, Lalbagh Road, Bangalore, 560027, Karnataka (India); Satpati, Ashis K [Analytical Chemistry Division, Bhabha Atomic Research Centre, Anushakthi Nagar, Trombay, Mumbai 400094, Maharashtra (India); D' Souza, Ozma J [Electrochemistry Research Group, Department of Chemistry, St. Joseph' s College, Lalbagh Road, Bangalore, 560027, Karnataka (India); Dhason, A [Soft Condensed Matter, Raman Research Institute, Sadashivnagar, Bangalore 560080, Karnataka (India)

    2017-04-01

    Free radicals are formed as byproducts of metabolism, and are highly unstable due to the presence of unpaired electrons. They readily react with other important cellular components such as DNA causing them damage. Antioxidants such as (+)-catechin (CAT), neutralize free radicals in the blood stream. Hence there is a need for detection and quantification of catechin concentration in various food sources and beverages. Electro-oxidative properties of catechin were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). A carbon paste working electrode modified by electropolymerizing methylene blue (MB) was fabricated. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) techniques were used to study the surface morphology of the electrode. Quasi-reversible electron transfer reaction occurred at + 0.260 V through a diffusion controlled process. In comparison to the bare carbon paste electrode (CPE), there was a significant 5.3 times increment in anodic current sensitivity at the modified electrode at physiological pH. Our findings indicate that for the electro-oxidation of CAT, CPE is a better base material for electropolymerization of MB compared to glassy carbon electrode (GCE). Nyquist plot followed the theoretical shape, indicating low interfacial charge transfer resistance of 0.095 kΩ at the modified electrode. Calibration plots obtained by DPV were linear in two ranges of 1.0 × 10{sup −3} to 1.0 × 10{sup −6} and 1.0 × 10{sup −7} to 0.1 × 10{sup −8} M. The limit of detection (LOD) and limit of quantification (LOQ) was 4.9 nM and 14 nM respectively. Application of the developed electrode was demonstrated by detecting catechin in green tea and spiked fruit juice with satisfactory recoveries. The sensor was stable, sensitive, selective and reproducible. - Highlights: • Remarkable electrocatalytic oxidation of Catechin at poly(methylene blue) modified CPE • Complete elimination of signal

  9. Carbon paste electrode in a solid-contact minicavity

    International Nuclear Information System (INIS)

    Ferreira, Antonio Ap. Pupim; Ribeiro, Sidney Jose Lima; Fugivara, Cecilio Sadao; Caiut, Jose Mauricio Almeida; Sargentelli, Vagner; Benedetti, Assis Vicente

    2011-01-01

    This work describes the preparation of carbon paste electrode (EPC) in a solid-contact minicavity and its evaluation when containing carbon paste without and with SiO 2 (Eu 3+ 2%) and SiO 2 (Eu 3+ 2%)-lysine sub-micrometrics particles. For this study cyclic voltammetry and electrochemical impedance measurements were performed at pH 7.4 in 0.1 mol L -1 PBS containing Fe(CN) 6 -3 / -4 redox species. The impedance results were interpreted based on a charge-transfer reaction involving Fe(CN) 6 -3 / -4 species and/or oxygen at higher frequencies and, diffusion of the electroactive species and carbon paste characteristics at lower frequencies. EPC-minicavity is suitable for electroanalysis using modified carbon paste. (author)

  10. Development of a novel MWCNTs-triazene-modified carbon paste electrode for potentiometric assessment of Hg(II) in the aquatic environments.

    Science.gov (United States)

    Mashhadizadeh, Mohammad Hossein; Ramezani, Soleyman; Rofouei, Mohammad Kazem

    2015-02-01

    In this approach, a new chemically modified carbon paste electrode was assembled for potentiometric assay of mercury(II) ion in the aqueous environments. Hereby, MWCNTs were used in the carbon paste composition to meliorate the electrical conductivity and sensitivity of the carbon paste owing to its exceptional physicochemical characteristics. Likewise, participation of the BEPT as a super-selective ionophore in the carbon paste composition boosted significantly the selectivity of the modified electrode towards Hg(II) ions over a wide concentration range of 4.0 × 10(-9)-2.2 × 10(-3) mol L(-1) with a lower detection limit of 3.1 × 10(-9) mol L(-1). Besides, Nernstian slope of the proposed sensor was 28.9(± 0.4)mV/decade over a pH range of 3.0-5.2 with potentiometric short response time of 10s. In the interim, by storing in the dark and cool dry place during non-usage period, the electrode can be used for at least 30 days without any momentous divergence of the potentiometric response. Eventually, to judge about its practical efficiency, the arranged sensor was utilized successfully as an indicator electrode for potentiometric titration of mercury(II) with standard solution of EDTA. As well, the quantitative analysis of mercury(II) ions in some aqueous samples with sensible accuracy and precision was satisfactorily performed. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Preparation and application of a carbon paste electrode modified with multi-walled carbon nanotubes and boron-embedded molecularly imprinted composite membranes.

    Science.gov (United States)

    Wang, Hongjuan; Qian, Duo; Xiao, Xilin; Deng, Chunyan; Liao, Lifu; Deng, Jian; Lin, Ying-Wu

    2018-06-01

    An innovative electrochemical sensor was fabricated for the sensitive and selective determination of tinidazole (TNZ), based on a carbon paste electrode (CPE) modified with multi-walled carbon nanotubes (MWCNTs) and boron-embedded molecularly imprinted composite membranes (B-MICMs). Density functional theory (DFT) calculations were carried out to investigate the utility of template-monomer interactions to screen appropriate monomers for the rational design of B-MICMs. The distinct synergic effect of MWCNTs and B-MICMs was evidenced by the positive shift of the reduction peak potential of TNZ at B-MICMs/MWCNTs modified CPE (B-MICMs/MWCNTs/CPE) by about 200 mV, and the 12-fold amplification of the peak current, compared with a bare carbon paste electrode (CPE). Moreover, the coordinate interactions between trisubstituted boron atoms embedded in B-MICMs matrix and nitrogen atoms of TNZ endow the sensor with advanced affinity and specific directionality. Thereafter, a highly sensitive electrochemical analytical method for TNZ was established by different pulse voltammetry (DPV) at B-MICMs/MWCNTs/CPE with a lower detection limit (1.25 × 10 -12  mol L -1 ) (S/N = 3). The practical application of the sensor was demonstrated by determining TNZ in pharmaceutical and biological samples with good precision (RSD 1.36% to 3.85%) and acceptable recoveries (82.40%-104.0%). Copyright © 2018 Elsevier B.V. All rights reserved.

  12. Effect of PW12–GPK on the acid characteristics of Ni-, Pd- and Pt- catalysts deposited onto pillared Al montmorillonite

    Directory of Open Access Journals (Sweden)

    D. Zhumadullaev

    2012-03-01

    Full Text Available Acid characteristics of Ni-, Pd-, Pt- catalyzers , deposited to Al pillared CaH montmorillonite modified by heteropolyacid H3PW12O40·xH2O (PW12 by ammonia thermoadsorbtion method has been studied.

  13. Anodic stripping voltammetric determination of silver ion at a carbon paste electrode modified with carbon nanotubes

    International Nuclear Information System (INIS)

    Tashkhourian, J.; Javadi, S.; Ana, F.N.

    2011-01-01

    A carbon paste electrode (CPE) was modified with multi-wall carbon nanotubes and successfully applied to the determination of silver ion by differential pulse anodic stripping voltammetry. Compared to a conventional CPE, a remarkably improved peak current response and sensitivity is observed. The analytical procedure consisted of an open circuit accumulation step for 2 min in -0.4 V, this followed by an anodic potential scan between +0.2 and + 0.6 V to obtain the voltammetric peak. The oxidation peak current is proportional to the concentration of silver ion in the range from 1.0 x 10 -8 to 1.0 x 10 -5 mol L -1 , with a detection limit of 1.8 x 10 -9 mol L -1 after an accumulation time of 120 s. The relative standard deviation for 7 successive determinations of Ag(I) at 0.1 μM concentration is 1.99%. The procedure was validated by determining Ag(I) in natural waters. (author)

  14. Adsorption of acetanilide herbicides on soil and its components. II. Adsorption and catalytic hydrolysis of diethatyl-ethyl on saturated Na(+)-, K(+)-, Ca(2+)-, and Mg(2+)-montmorillonite.

    Science.gov (United States)

    Liu, W P; Fang, Z; Liu, H J; Yang, W C

    2001-04-01

    Adsorption and catalytic hydrolysis of the herbicide diethatyl-ethyl [N-chloroacetyl-N-(2,6-diethylphenyl)glycine ethyl ester] on homoionic Na(+)-, K(+)-, Ca(2+)-, and Mg(2+)-montmorillonite clays were investigated in water solution. The Freundlich adsorption coefficient, Ki, got from isotherms on clay followed the order of Na+ approximately K+ > Mg2+ approximately Ca2+. Analysis of FT-IR spectra of diethatyl-ethyl adsorbed on clay suggests probable bonding at the carboxyl and amide carbonyl groups of the herbicide. The rate of herbicide hydrolysis in homoionic clay suspensions followed the same order as that for adsorption, indicating that adsorption may have preceded and thus caused hydrolysis. Preliminary product identification showed that hydrolysis occurred via nucleophilic substitution at the carboxyl carbon, causing the cleavage of the ester bond and formation of diethatyl and its dechlorinated derivative, and at the amide carbon, yielding an ethyl ester derivative and its acid. These pathways also suggest that hydrolysis of diethatyl-ethyl was catalyzed by adsorption on the clay surface.

  15. Manganese dioxide-modified carbon paste electrode for voltammetric determination of riboflavin

    International Nuclear Information System (INIS)

    Mehmeti, Eda; Kalcher, Kur; Stanković, Dalibor M.; Chaiyo, Sudkate; Švorc, Ľubomir

    2016-01-01

    A carbon paste electrode bulk was modified with MnO 2 and investigated for use as an electrochemical sensor for riboflavin (vitamin B 2 ) using differential pulse voltammetry (DPV). Riboflavin displays a well expressed oxidation peak at −0.15 V (versus Ag/AgCl) in solutions with a pH value of 2. Effects of pH value, pulse amplitude and pulse time were optimized by employing DPV. The signals obtained are linearly related to the concentrations of riboflavin in the range from 0.02 to 9 μM. Other features include a 15 nM detection limit, and good reproducibility (±3 %) and repeatability (±2 %). Interferences by common compounds were tested, and the method was successfully applied to the determination of riboflavin in pharmaceutical formulations where is gave recoveries in the range from 95 to 97 %. (author)

  16. Removal of Disperse Blue 56 and Disperse Red 135 dyes from aqueous dispersions by modified montmorillonite nanoclay

    Directory of Open Access Journals (Sweden)

    Ahmadishoar Javad

    2017-01-01

    Full Text Available In this study modified montmorillonite was used as an adsorbent for the removal of two selected disperse dyes i.e., Disperse Blue 56 (DB and Disperse Red 135 (DR from dye dispersions. The adsorption equilibrium data of dyes adsorption were investigated by using Nernst, Freundlich and Langmuir isotherm models. The adsorption kinetics was analyzed by using different models including pseudo-first-order, pseudo-second-order, Elovich and Intraparticle diffusion model. The Freundlich isotherm was found to be the most appropriate model for describing the sorption of the dyes on modified nanoclay. The best fit to the experimental results was obtained by using the pseudo-second-order kinetic equation, which satisfactorily described the process of dye adsorption. Although different kinetic models may control the rate of the adsorption process, the results indicated that the main rate limiting step was the intraparticle diffusion. The results showed that the proposed modified montmorillonite could be used as an effective adsorbent for the removal of disperse dyes even from highly concentrated dispersions.

  17. EFFECT OF ORGANOPHILIZATION AND INTERLAMELLAR SILYLATION OF MONTMORILLONITE ON COMPATIBLIZATION OF POLYMER COMPOSITES

    Directory of Open Access Journals (Sweden)

    Mamdouh Abdel Rahim

    2016-12-01

    Full Text Available Sodium montmorillonite (Na-Mt was modified by cetyltriemethylammoniumbromide (CTAB through cation exchange technique followed by grafting with 3-aminopropyltriethoxysilane (APT. The effects of organophillic surface treatments of montmorillonite on compatibilization of natural rubber (NR /acrylonitrile butadiene rubber (NBR blends was investigated. Physico-mechanical properties of rubber nanocomposites compatibilized with organomodified montmorillonite revealed strong nanocomposite with high tensile properties, impact strength and good resistance to flex fatigue, abrasion and compression set. Dynamic mechanical thermal analysis (DMTA revealed a marked increase in storage modulus (E' and lesser damping characteristics of organically modified clay mineral polymer nanocomposites (CPN due to intercalation of organophilic montmorillonite by rubber matrix. The morphology of the blends became homogeneous and smoother with the presence of exofoliated/intercalated organically modified montmorillonite. Organomodified layered silicate sheets of montmorillonite greatly enhanced barrier properties by creating tortuous path that retarded the progress of solvent molecules through rubber matrix.

  18. Electrochemical sensor for ranitidine determination based on carbon paste electrode modified with oxovanadium (IV) salen complex.

    Science.gov (United States)

    Raymundo-Pereira, Paulo A; Teixeira, Marcos F S; Fatibello-Filho, Orlando; Dockal, Edward R; Bonifácio, Viviane Gomes; Marcolino, Luiz H

    2013-10-01

    The preparation and electrochemical characterization of a carbon paste electrode modified with the N,N-ethylene-bis(salicyllideneiminato)oxovanadium (IV) complex ([VO(salen)]) as well as its application for ranitidine determination are described. The electrochemical behavior of the modified electrode for the electroreduction of ranitidine was investigated using cyclic voltammetry, and analytical curves were obtained for ranitidine using linear sweep voltammetry (LSV) under optimized conditions. The best voltammetric response was obtained for an electrode composition of 20% (m/m) [VO(salen)] in the paste, 0.10 mol L(-1) of KCl solution (pH 5.5 adjusted with HCl) as supporting electrolyte and scan rate of 25 mV s(-1). A sensitive linear voltammetric response for ranitidine was obtained in the concentration range from 9.9×10(-5) to 1.0×10(-3) mol L(-1), with a detection limit of 6.6×10(-5) mol L(-1) using linear sweep voltammetry. These results demonstrated the viability of this modified electrode as a sensor for determination, quality control and routine analysis of ranitidine in pharmaceutical formulations. Copyright © 2013. Published by Elsevier B.V.

  19. Highly sensitive simultaneous electrochemical determination of trace amounts of Pb(II) and Cd(II) using a carbon paste electrode modified with multi-walled carbon nanotubes and a newly synthesized Schiff base

    International Nuclear Information System (INIS)

    Afkhami, Abbas; Ghaedi, Hamed; Madrakian, Tayyebeh; Rezaeivala, Majid

    2013-01-01

    Highlights: ► A new chemically modified carbon paste electrode was constructed and used. ► A new Schiff base and multi-walled carbon nanotube was used as modifiers. ► The electrochemical properties of the modified electrode were studied. ► The electrode was used to the simultaneous determination of Pb 2+ and Cd 2+ . -- Abstract: A new chemically modified electrode was constructed for rapid, simple, accurate, selective and highly sensitive simultaneous determination of lead and cadmium using square wave anodic stripping voltammetry (SWASV). The electrode was prepared by incorporation of new synthesized Schiff base and multi-walled carbon nanotubes (MWCNT) in carbon paste electrode. The limit of detection was found to be 0.25 ng mL −1 and 0.74 ng mL −1 for Pb 2+ and Cd 2+ , respectively. The stability constants of the complexes of the ligand with several metal cations in ethanol medium were determined. The effects of different cations and anions on the simultaneous determination of metal ions were studied and it was found that the electrode is highly selective. The proposed chemically modified electrode was used for the determination of lead and cadmium in several foodstuffs and water samples

  20. Voltammetric determination of ultratrace levels of cerium(III) using a carbon paste electrode modified with nano-sized cerium-imprinted polymer and multiwalled carbon nanotubes

    International Nuclear Information System (INIS)

    Alizadeh, Taher; Ganjali, Mohammad Reza; Akhoundian, Maede; Norouzi, Parviz

    2016-01-01

    A carbon paste electrode was modified with a Ce(III)-imprinted polymer (Ce-IP) and used for voltammetric determination of Ce(III) ions in real water samples. Precipitation polymerization was used for synthesis of the nano-sized Ce-IP from vinylpyridine and methacrylic acid (acting as the complexing ligands and functional monomers), divinylbenzene (cross-linker) and AIBN as the radical starter. The Ce-IP was characterized by scanning electron microscopy and zeta potentials. A carbon paste electrode (CPE) was then impregnated with the Ce-IP and used for the extraction and subsequent determination of Ce(III). Oxidative square wave voltammetry showed the electrode to give a significantly better response than an electrode modified with the non-imprinted polymer. The addition of multiwalled carbon nanotubes to the Ce-IP-modified electrode further improves the signal, thereby increasing the sensitivity of the method. The effects of electrode composition, extraction pH value, volume and time were optimized. The electrode, if operated at a voltage of 1.05 V (vs. Ag/AgCl), displays a linear response to Ce(III) in the 1.0 μM to 25 pM concentration range, and the detection limit is 10 pM (at an S/N ratio of 3). The relative standard deviation of 5 separate determinations is 3.1 %. The method was successfully applied to the determination of Ce(III) in the spiked samples of drinking water and sea water. (author)

  1. The effect of exchangeable cations in clinoptilolite and montmorillonite on the adsorption of aflatoxin B1

    Directory of Open Access Journals (Sweden)

    DRAGAN STOJSIC

    2001-08-01

    Full Text Available The adsorption of aflatoxin B1 (AFB1 by cation-exchanged clinoptilolite zeolitic tuff and montmorillonite was investigated at 37°C and pH 3.8 from an aqueous electrolyte having a composition similar to that of gastric juices of animals. Both minerals were exchanged from the natural form to the sodium form and then to the Cu2+, Zn2+ and Co2+-rich forms. The cation exchange was different for the different cations, but in all cases the exchanges were larger on montmorillonite than on clinoptilolite. The degree of exchange on montmorillonite was 76 % for copper (from a total of CEC 0.95 meq/g, Cu2+ –0.73 meq/g and 85 % for zinc and cobalt. Under the same conditions (concentration, temperature, pH, contact time, the degree of exchange on zeolitic tuff was 12 % for Cu2+ (from a total CEC of 1.46 meq/g, Cu2+ –0.17 meq/g, 8 % for Zn2+ and 10 % for Co2+. Both groups of mineral adsorbents showed high AFB1 chemisorption indexes (ca. For the montmorillonite forms, ca ranged from 0.75 for the Cu-exchanged montmorillonite to 0.89 for the natural Ca-form, 0.90 for the Zn-exchanged form and 0.93 for the Co-exchanged montmorillonite. The adsorption of AFB1 on the different exchanged forms of clinoptilolite gave similar values of ca for the Cu and Ca forms (0.90 and values of 0.94 and 0.95 for the Zn- and Co-exchanged form. The impact of the mineral adsorbents on the reduction of essential nutrients present in animal feed (Cu, Zn, Mn and Co showed that the Ca-rich montmorillonite had a higher capability for the reduction of the microelements than the Ca-rich clinoptilolite.

  2. Early Age Carbonation Heat and Products of Tricalcium Silicate Paste Subject to Carbon Dioxide Curing

    Directory of Open Access Journals (Sweden)

    Zhen Li

    2018-05-01

    Full Text Available This paper presents a study on the carbonation reaction heat and products of tricalcium silicate (C3S paste exposed to carbon dioxide (CO2 for rapid curing. Reaction heat was measured using a retrofitted micro-calorimeter. The highest heat flow of a C3S paste subject to carbonation curing was 200 times higher than that by hydration, and the cumulative heat released by carbonation was three times higher. The compressive strength of a C3S paste carbonated for 2 h and 24 h was 27.5 MPa and 62.9 MPa, respectively. The 24-h carbonation strength had exceeded the hydration strength at 28 days. The CO2 uptake of a C3S paste carbonated for 2 h and 24 h was 17% and 26%, respectively. The X-ray diffraction (XRD, transmission electron microscope coupled with energy dispersive spectrometer (TEM-EDS, and 29Si magic angle spinning–nuclear magnetic resonance (29Si MAS-NMR results showed that the products of a carbonated C3S paste were amorphous silica (SiO2 and calcite crystal. There was no trace of calcium silicate hydrate (C–S–H or other polymorphs of calcium carbonate (CaCO3 detected.

  3. Electrocatalytic behavior of carbon paste electrode modified with metal phthalocyanines nanoparticles toward the hydrogen evolution

    International Nuclear Information System (INIS)

    Abbaspour, Abdolkarim; Norouz-sarvestani, Fatemeh; Mirahmadi, Ehsan

    2012-01-01

    Highlights: ► The new construction of a carbon paste electrode impregnated with nanoparticles of Zn and Ni phthalocyanine (nano ZnPc and nano NiPc). ► The decrease overpotential and higher current value obtained in nano ZnPc and nano NiPc compared to bulky ZnPc and bulky NiPc, respectively. ► Types of the catalyst and pH of the solution affect the electro catalytic proton reduction reaction considerably. - Abstract: This paper describes the construction of a carbon paste electrode (CPE) impregnated with nanoparticles of Zn and Ni phthalocyanine (nano ZnPc and nano NiPc). These new electrodes (nano ZnPc-CPE and nano NiPc-CPE) reveal interesting electrocatalytic behavior toward hydrogen evolution reaction (HER). Voltammetric characteristics indicated that the proposed electrodes display better electrocatalytic activity compared to their corresponding bulky modified metal phthalocyanines (MPcs) in minimizing overpotential and increasing the reduction current of HER. Electrocatalytic activities irregularly change with the pH of the solution. However by increasing the pH while nano MPcs are still active, bulky MPcs are almost inactive, and their corresponding ΔE increase by increasing the pH.

  4. Adsorption of Lysine on Na-Montmorillonite and Competition with Ca(2+): A Combined XRD and ATR-FTIR Study.

    Science.gov (United States)

    Yang, Yanli; Wang, Shengrui; Liu, Jingyang; Xu, Yisheng; Zhou, Xiaoyun

    2016-05-17

    Lysine adsorption at clay/aqueous interfaces plays an important role in the mobility, bioavailability, and degradation of amino acids in the environment. Knowledge of these interfacial interactions facilitates our full understanding of the fate and transport of amino acids. Here, X-ray diffraction (XRD) and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) measurements were used to explore the dynamic process of lysine adsorption on montmorillonite and the competition with Ca(2+) at the molecular level. Density functional theory (DFT) calculations were employed to determine the peak assignments of dissolved lysine in the solution phase. Three surface complexes, including dicationic, cationic, and zwitterionic structures, were observed to attach to the clay edge sites and penetrate the interlayer space. The increased surface coverage and Ca(2+) competition did not affect the interfacial lysine structures at a certain pH, whereas an elevated lysine concentration contributed to zwitterionic-type coordination at pH 10. Moreover, clay dissolution at pH 4 could be inhibited at a higher surface coverage with 5 and 10 mM lysine, whereas the inhibition effect was inconspicuous or undetected at pH 7 and 10. The presence of Ca(2+) not only could remove a part of the adsorbed lysine but also could facilitate the readsorption of dissolved Si(4+) and Al(3+) and surface protonation. Our results provide new insights into the process of lysine adsorption and its effects on montmorillonite surface sites.

  5. Sensing nitric oxide with a carbon nanofiber paste electrode modified with a CTAB and nafion composite

    International Nuclear Information System (INIS)

    Zheng, Dongyun; Liu, Xiaojun; Zhu, Shanying; Cao, Huimin; Chen, Yaguang; Hu, Shengshui

    2015-01-01

    We describe an electrochemical sensor for nitric oxide that was obtained by modifying the surface of a nanofiber carbon paste microelectrode with a film composed of hexadecyl trimethylammonium bromide and nafion. The modified microelectrode displays excellent catalytic activity in the electrochemical oxidation of nitric oxide. The mechanism was studied by scanning electron microscopy and cyclic voltammetry. Under optimal conditions, the oxidation peak current at a working voltage of 0.75 V (vs. SCE) is related to the concentration of nitric oxide in the 2 nM to 0.2 mM range, and the detection limit is as low as 2 nM (at an S/N ratio of 3). The sensor was successfully applied to the determination of nitric oxide released from mouse hepatocytes. (author)

  6. Highly sensitive and selective determination of methylergometrine maleate using carbon nanofibers/silver nanoparticles composite modified carbon paste electrode

    International Nuclear Information System (INIS)

    Kalambate, Pramod K.; Rawool, Chaitali R.; Karna, Shashi P.; Srivastava, Ashwini K.

    2016-01-01

    A highly sensitive and selective voltammetric method for determination of Methylergometrine maleate (MM) in pharmaceutical formulations, urine and blood serum samples has been developed based on enhanced electrochemical response of MM at carbon nanofibers and silver nanoparticles modified carbon paste electrode (CNF-AgNP-CPE). The electrode material was characterized by various techniques viz., X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The electrocatalytic response of MM at CNF-AgNP-CPE was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Under optimized conditions, the proposed sensor exhibits excellent electrochemical response towards MM. The DPV study shows greatly enhanced electrochemical signal for MM at CNF-AgNP-CPE lending high sensitivity to the proposed sensor for MM detection. The peak (I p ) current for MM is found to be rectilinear in the range 4.0 × 10 −8 –2.0 × 10 −5 M with a detection limit of 7.1 × 10 −9 M using DPV. The feasibility of the proposed sensor in analytical applications was investigated by conducting experiments on commercial pharmaceutical formulations, human urine and blood serum samples, which yielded satisfactory recoveries of MM. The proposed electrochemical sensor offers high sensitivity, selectivity, reproducibility and practical utility. We recommend it as an authentic and productive electrochemical sensor for successful determination of MM. - Highlights: • Voltammetric sensor for methylergometrine maleate using carbon nanofibers and silver nanoparticle - carbon paste electrode • Wide working range, good reproducibility, fast response and high stability were the main advantages of the proposed sensor • Analysis of methylergometrine maleate in pharmaceutical formulations, urine and blood serum samples • Lowest limit of detection obtained for methylergometrine maleate

  7. Stripping voltammetry of technetium using a TOA modified carbon paste electrode

    International Nuclear Information System (INIS)

    Ruf, H.; Schorb, K.

    1989-10-01

    Low concentrations of technetium have been measured DP-stripping-voltammetrically using a carbon paste electrode modified with tri-n-octylamine (TOA-CPE). Preconcentration of the metal ion on the electrode surface accomplished by dipping of the latter in the sample solution which is 2M in HCl, relies on the chemical reaction with the amine acting as a liquid anion exchanger. Both, Tc-IV occurring as the TcCl 6 2- ion in chloride solutions as well as Tc-VII hereby are deposited. Measurements following deposition yield voltammograms of essentially different shapes for the two Tc species. With Tc-IV a characteristic curve with a prominent current signal at -280 mV (vs. Ag/AgCl) is obtained which can be evaluated for Tc quantitation. However, starting from Tc-VII, complex voltammograms are registered not allowing direct technetium assays. Nevertheless, after reduction to Tc-IV, e.g. by means of ascorbic acid, also Tc-VII can be quantified reliably by the method described, the lower detection limit for both oxidation states being about 4x10 -8 M. (orig.) [de

  8. Adsorption properties of Congo Red from aqueous solution onto surfactant-modified montmorillonite

    International Nuclear Information System (INIS)

    Wang Li; Wang Aiqin

    2008-01-01

    A series of surfactant-modified montmorillonites (MMT) were prepared using octyltrimethylammonium bromide (OTAB), dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB) and stearyltrimethylammonium bromide (STAB), and the organification of MMT was proved by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron micrographic (SEM) and transmission electron microscope (TEM). The adsorption of Congo Red (CR) anionic dye from aqueous solution onto surfactant-modified MMT was carried out. Compared with MMT, the adsorption capacity of surfactant-modified MMT for CR was greatly enhanced and MMT modified with CTAB (2.0 CEC) exhibited the higher adsorption capacity. The effects of pH value of the dye solution, adsorption temperature, adsorption time and the initial dye concentration on the adsorption capacity of CR on CTAB-MMT have been investigated. The results showed that the adsorption kinetic of CR on CTAB-MMT could be best described by the pseudo-second-order model and that the adsorption isotherm of CR was in good agreement with the Langmuir equation. The IR spectra and SEM analysis also revealed that the adsorption of CTAB-MMT was a chemical adsorption process between CTAB and the NH 2 , -N=N- and SO 3 groups of CR

  9. A new luminescent montmorillonite/borane nanocomposite

    Czech Academy of Sciences Publication Activity Database

    Kolská, Z.; Matoušek, J.; Čapková, P.; Braborec, Jakub; Benkocká, M.; Černá, H.; Londesborough, Michael Geoffrey Stephen

    2015-01-01

    Roč. 118, DEC (2015), s. 295-300 ISSN 0169-1317 Institutional support: RVO:61388980 Keywords : Luminophore * Montmorillonite/borane nanocomposite * X-ray photoelectron spectroscopy * X-ray diffraction * UV–Vis spectra Subject RIV: CA - Inorganic Chemistry Impact factor: 2.586, year: 2015

  10. Simultaneous trace-levels determination of Hg(II) and Pb(II) ions in various samples using a modified carbon paste electrode based on multi-walled carbon nanotubes and a new synthesized Schiff base

    International Nuclear Information System (INIS)

    Afkhami, Abbas; Bagheri, Hasan; Khoshsafar, Hosein; Saber-Tehrani, Mohammad; Tabatabaee, Masoumeh; Shirzadmehr, Ali

    2012-01-01

    Highlights: ► A new chemically modified carbon paste electrode was constructed and used. ► A new Schiff base and multi-walled carbon nanotube was used as a modifier. ► The electrochemical properties of the modified electrode were studied. ► The electrode was used to the simultaneous determination of Pb 2+ and Hg 2+ . - Abstract: A modified carbon paste electrode based on multi-walled carbon nanotubes (MWCNTs) and 3-(4-methoxybenzylideneamino)-2-thioxothiazolodin-4-one as a new synthesized Schiff base was constructed for the simultaneous determination of trace amounts of Hg(II) and Pb(II) by square wave anodic stripping voltammetry. The modified electrode showed an excellent selectivity and stability for Hg(II) and Pb(II) determinations and for accelerated electron transfer between the electrode and the analytes. The electrochemical properties and applications of the modified electrode were studied. Operational parameters such as pH, deposition potential and deposition time were optimized for the purpose of determination of traces of metal ions at pH 3.0. Under optimal conditions the limits of detection, based on three times the background noise, were 9.0 × 10 −4 and 6.0 × 10 −4 μmol L −1 for Hg(II) and Pb(II) with a 90 s preconcentration, respectively. In addition, the modified electrode displayed a good reproducibility and selectivity, making it suitable for the simultaneous determination of Hg(II) and Pb(II) in real samples such as sea water, waste water, tobacco, marine and human teeth samples.

  11. A quantitative mechanistic description of Ni, Zn and Ca sorption on Na-montmorillonite. Part III: modelling

    International Nuclear Information System (INIS)

    Baeyens, B.; Bradbury, M.H.

    1995-07-01

    Titration and sorption measurements, carried out under a wide variety of conditions on Na-montmorillonite, were examined in terms of cation exchange and surface complexation mechanisms. A computer code called MINSORB was developed and used throughout this work. This code allowed the uptake of radionuclides by both mechanisms to be calculated simultaneously; also taking into account competitive reactions from other cations present. A stepwise iterative fitting/modelling procedure is described. For the case of Na-montmorillonite it is demonstrated that an electrostatic term in the surface complexation model is not required. A basic data set comprising of site capacities and protonation/deprotonation constants was defined, which was valid for all surface complexation sorption reactions. The main study was carried out with Ni, but impurity cations present in the system, particularly Zn, had to be examined in addition due to their competitive effects on Ni sorption. The surface complexation behaviour of Ni and Zn was investigated in detail to give intrinsic surface complexation constants on two of the =SOH type sites included in the model. The sorption of Mg, Ca and Mn is also considered, though in less detail, and estimated surface complexation constants for these nuclides are presented. Cation exchange was included in all of the calculations. Measured selectivity coefficients for Ni-Na, Zn-Na and Ca-Na exchange reactions are given. The model, with the derived parameters, allowed all the data from titration measurements through sorption edges to sorption isotherms to be calculated. (author) 31 figs., 9 tabs., refs

  12. A quantitative mechanistic description of Ni, Zn and Ca sorption on Na-Montmorillonite. Part III: Modelling

    International Nuclear Information System (INIS)

    Baeyens, B.; Bradbury, M.H.

    1995-07-01

    Titration and sorption measurements, carried out under a wide variety of conditions on Na-montmorillonite, were examined in terms of cation exchange and surface complexation mechanisms. A computer code called MINSORB was developed and used throughout this work. This code allowed the uptake of radionuclides by both mechanisms to be calculated simultaneously; also taking into account competitive reactions from other cations present. A stepwise iterative fitting/modelling procedure is described. For the case of Na-montmorillonite it is demonstrated that an electrostatic term in the surface complexation model is not required. A basic data set comprising of site capacities and protonation/deprotonation constants was defined, which was valid for all surface complexation sorption reactions. The main study was carried out with Ni, but impurity cations present in the system, particularly Zn, had to be examined in addition due to their competitive effects on Ni sorption. The surface complexation behaviour of Ni and Zn was investigated in detail to give intrinsic surface complexation constants on two of the ≡SOH type sites included in the model. The sorption of Mg, Ca and Mn is also considered, though in less detail, and estimated surface complexation constants for these nuclides are presented. Cation exchange was included in all of the calculations. Measured selectivity coefficients for Ni-Na, Zn-Na and Ca-Na exchange reactions are given. The model, with the derived parameters, allowed all the data from titration measurements through sorption edges to sorption isotherms to be calculated. (author) 31 figs., 9 tabs., refs

  13. Application of graphene oxide/lanthanum-modified carbon paste electrode for the selective determination of dopamine

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Fengying; Feng, Chenqi; Fu, Ning; Wu, Huihui; Jiang, Jibo, E-mail: jibojiang0506@163.com; Han, Sheng, E-mail: hansheng654321@sina.com

    2015-12-01

    Highlights: • The effective surface area of the modified CPE has been expanded after self-assembly. • The GO–La composite exhibited excellent electrocatalytic activity toward DA. • The GO–La/CPE presented high selectivity, sensitivity, excellent stability and repeatability. - Abstract: A home-made carbon paste electrode (CPE) was reformed by graphene oxide (GO)/lanthanum (La) complexes, and a modified electrode, called GO–La/CPE, was fabricated for the selective determination of dopamine (DA) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Several factors affecting the electrocatalytic performance of the modified sensor were investigated. Owning to the combination of GO and La ions, the GO–La/CPE sensor exhibited large surface area, well selectivity, good repeatability and stability in the oxidation reaction of DA. At optimal conditions, the response of the GO–La/CPE electrode for determining DA was linear in the region of 0.01–0.1 μM and 0.1–400.0 μM. The limit of detection was down to 0.32 nM (S/N = 3). In addition, this modified electrode was successfully applied to the detection of DA in real urine and serum samples by using standard adding method, showing its promising application in the electroanalysis of real samples.

  14. Molecular Simulation Study of Montmorillonite in Contact with Variably Wet Supercritical Carbon Dioxide

    KAUST Repository

    Kadoura, Ahmad Salim

    2017-03-07

    We perform grand canonical Monte Carlo simulations to study the detailed molecular mechanism of intercalation behavior of CO2 in Na-, Ca-, and Mg- montmorillonite exposed to variably hydrated supercritical CO2 at 323.15 K and 90 bar, The simulations indicate that the intercalation of CO2 strongly depends on the relative humidity (RH). The intercalation of CO2 in the dehydrated interlayer is inhibited, followed by the swelling of the interlayer region due to uptake of water and CO2 as the RH increases. In all of the hydrated clay samples, the amount of the intercalated CO2 generally decreases as a function of increasing RH, which is attributed mainly to the weakening of the interaction between CO2 and clay. At low RH values, Ca- and Mg- montmorillonite are relatively more efficient in capturing CO2. The amount of CO2 trapped in all clay samples shows similar values above RH of similar to 60%. Molecular dynamics simulations show that the diffusion coefficient of each species generally increases with increasing RH due to the associated expansion of the interlayer distance of the clay. For all the hydrated samples, the diffusion coefficients of CO2 and water in the interlayers are mostly comparable due to the fact that CO2 molecules are well solvated. The diffusion of CO2 in each hydration state is mostly independent of the type of cation in accordance with the fact that CO2 molecules hardly migrate into the first hydration shell of the interlayer cations.

  15. Nano-clays from natural and modified montmorillonite with and without added blueberry extract for active and intelligent food nanopackaging materials

    Energy Technology Data Exchange (ETDEWEB)

    Gutiérrez, Tomy J., E-mail: tomy.gutierrez@ciens.ucv.ve [Departamento Químico Analítico, Facultad de Farmacia, Universidad Central de Venezuela, Apartado 40109, Caracas, 1040-A (Venezuela, Bolivarian Republic of); Instituto de Ciencia y Tecnología de Alimentos, Facultad de Ciencias, Universidad Central de Venezuela, Apartado 47097, Caracas, 1041-A (Venezuela, Bolivarian Republic of); Grupo de Materiales Compuestos Termoplásticos (CoMP), Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA), Facultad de Ingeniería, Universidad Nacional de Mar del Plata UNMdP y Consejo Nacional de Investigaciones Científicas y Técnicas - CONICET, Colón 10850, B7608FLC, Mar del Plata (Argentina); Ponce, Alejandra G. [Grupo de Investigación en Ingeniería en Alimentos, Facultad de Ingeniería, Universidad Nacional de Mar del Plata (UNMdP), Juan B. Justo 4302, 7600, Mar del Plata (Argentina); Alvarez, Vera A. [Grupo de Materiales Compuestos Termoplásticos (CoMP), Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA), Facultad de Ingeniería, Universidad Nacional de Mar del Plata UNMdP y Consejo Nacional de Investigaciones Científicas y Técnicas - CONICET, Colón 10850, B7608FLC, Mar del Plata (Argentina)

    2017-06-15

    The aim of this study was to evaluate the potential of nano-clays as active and intelligent (A&I) food nanopackaging materials. Nanopackaging is a structured system that allows the storage of certain compounds in a stable form. Nano-clays were prepared from natural and modified montmorillonite (Mnt) with and without added blueberry extract, and characterized in terms of their: X-ray diffraction (XRD) patterns, thermogravimetric (TGA) properties, microstructure, moisture content, water activity (a{sub w}), infrared spectra (FTIR), Raman spectra, color parameters, response to pH changes, and antioxidant and antimicrobial activity. Mnt prepared with added blueberry extract showed antioxidant activity and intelligent behavior under different pH conditions. Modifying the Mnt increased the interlayer spacing, thus allowing more blueberry extract to be incorporated within the system. In conclusion, natural and modified Mnt are eco-friendly resources with potential applications for nano-packaging. The addition of blueberry extract imparted intelligent properties to the nano-clays as regards their responses to changes in pH. - Highlights: • Food nano-packaging were obtained from natural and modified montmorillonite (Mnt). • XRD, TGA and FTIR results suggests the blueberry extract nano-packaging. • Intelligent nanocomposites were obtained. • Greater interlayer spacing of the nano-Mnt allows greater nano-packaging.

  16. Nano-clays from natural and modified montmorillonite with and without added blueberry extract for active and intelligent food nanopackaging materials

    International Nuclear Information System (INIS)

    Gutiérrez, Tomy J.; Ponce, Alejandra G.; Alvarez, Vera A.

    2017-01-01

    The aim of this study was to evaluate the potential of nano-clays as active and intelligent (A&I) food nanopackaging materials. Nanopackaging is a structured system that allows the storage of certain compounds in a stable form. Nano-clays were prepared from natural and modified montmorillonite (Mnt) with and without added blueberry extract, and characterized in terms of their: X-ray diffraction (XRD) patterns, thermogravimetric (TGA) properties, microstructure, moisture content, water activity (a_w), infrared spectra (FTIR), Raman spectra, color parameters, response to pH changes, and antioxidant and antimicrobial activity. Mnt prepared with added blueberry extract showed antioxidant activity and intelligent behavior under different pH conditions. Modifying the Mnt increased the interlayer spacing, thus allowing more blueberry extract to be incorporated within the system. In conclusion, natural and modified Mnt are eco-friendly resources with potential applications for nano-packaging. The addition of blueberry extract imparted intelligent properties to the nano-clays as regards their responses to changes in pH. - Highlights: • Food nano-packaging were obtained from natural and modified montmorillonite (Mnt). • XRD, TGA and FTIR results suggests the blueberry extract nano-packaging. • Intelligent nanocomposites were obtained. • Greater interlayer spacing of the nano-Mnt allows greater nano-packaging.

  17. Thermal treatment to improve the hydrophobicity of ground CaCO3 particles modified with sodium stearate

    Science.gov (United States)

    Liang, Yong; Yu, Keyi; Zheng, Qinzhong; Xie, Jiuren; Wang, Ting-Jie

    2018-04-01

    The surface modification of calcium carbonate (CaCO3) particles, which is used as a filler, significantly affects the properties of the composed materials. The effects of thermal treatment on ground calcium carbonate (GCC) particles subjected to hydrophobic modification using sodium stearate (RCOONa) were studied. The contact angle of the modified GCC particles increased from 24.7° to 118.9° when the amount of RCOONa added was increased from 0% to 5% and then decreased to 97.5° when the RCOONa content was further increased to 10%. When a large amount of RCOONa was added, RCOO- reacts with Ca2+ and generates (RCOO)2Ca nuclei, which are adsorbed on the surface of the GCC particles, forming a discontinuous (RCOO)2Ca modified layer. After thermal treatment under sealed conditions, the contact angle of the GCC particles modified using 1.5% RCOONa/GCC increased from 112.8° to 139.6°. The thermal stability of the (RCOO)2Ca modified layer was increased, with the temperature increase of the mass-loss peak from 358.0 to 463.0 °C. It is confirmed that the spreading of melted (RCOO)2Ca nuclei on the surface of the GCC particles during the thermal treatment increased the continuity of the modified layer, converting the physical adsorption of the (RCOO)2Ca nuclei into chemisorption. The grafting density of RCOO- on the GCC particle surface after thermal treatment approximates to 5.00/nm2, which is close to the single-molecular-layer grafting density of RCOO-, indicating that excellent modification was achieved.

  18. Electrochemical behavior of labetalol at an ionic liquid modified carbon paste electrode and its electrochemical determination

    Directory of Open Access Journals (Sweden)

    Zhang Yan-Mei

    2013-01-01

    Full Text Available Electrochemical behavior of labetalol (LBT at carbon paste electrode (CPE and an ionic liquid1-benzyl-3-methylimidazolehexafluorophosphate([BnMIM]PF6modified carbon paste electrode([BnMIM]PF6/CPEin Britton-Robinson buffer solution (pH 2.0 was investigated by cyclic voltammetry (CV and square wave voltammetric (SWV. The experimental results showed that LBT at both the bare CPE and [BnMIM]PF6/CPEshowed an irreversible oxidation process, but at [BnMIM]PF6/CPE its oxidation peak current increased greatly and the oxidation peak potential shifted negatively. The electrode reaction process is a diffusion-controlled process involving one electron transferring accompanied by a participation of one proton at [BnMIM]PF6/CPE. At the same time, the electrochemical kinetic parameters were determined. Under the optimized electrochemical experimental conditions, the oxidation peak currents were proportional to LBT concentration in the range of 7.0 x 10-6-1.0 x 10-4 mol L-1 with the limit of detection(LOD, S/N=3 of 4.810 x 10-8 mol L-1and the limit of quantification(LOQ, S/N=10 of 1.60 x 10-7 mol L-1, respectively. The proposed method was successfully applied in the determination of LBT content in commercial tablet samples.

  19. Hybrid structures based on montmorillonite/modified starch intercalate

    Czech Academy of Sciences Publication Activity Database

    Duchek, P.; Špírková, Milena

    2010-01-01

    Roč. 104, č. 9 (2010), s. 885 ISSN 0009-2770. [International Conference on Polysaccharides-Glycoscience /6./. 29.09.2010-1.10.2010, Praha] R&D Projects: GA AV ČR(CZ) IAAX08240901 Institutional research plan: CEZ:AV0Z40500505 Keywords : organic/inorganic hybrides * montmorillonite Subject RIV: JI - Composite Materials

  20. Effect of telechelic ionic groups on the dispersion of organically modified clays in bisphenol A polycarbonate nanocomposites by in-situ polymerization using activated carbonates

    Directory of Open Access Journals (Sweden)

    M. Colonna

    2017-05-01

    Full Text Available Nanocomposites of bisphenol A polycarbonate with organically modified clays have been prepared for the first time by in-situ polymerization using bis(methyl salicyl carbonate as activated carbonate. The use of the activated carbonate permits to conduct the polymerization reaction at lower temperature and with shorter polymerization time with respect to those necessary for traditional melt methods that uses diphenyl carbonate, affording a nanocomposite with improved color. Moreover, an imidazolium salt with two long alkyl chains has been used to modify the montmorillonite, providing an organically modified clay with high thermal stability and wide d-spacing. The addition of ionic groups at the end of the polymer chain increases the interaction between the clay surface and the polymer producing a better dispersion of the clay. The presence of the clay increases the thermal stability of the polymer.

  1. Non-enzymatic sensing of uric acid using a carbon nanotube ionic-liquid paste electrode modified with poly(β-cyclodextrin)

    International Nuclear Information System (INIS)

    Li, Yonghong; Ji, Xiaoling; Wang, Ling; Qiu, Hongyan; Zhai, Xiurong; Wang, Haibo; Liu, Xinsheng; Guo, Le; Liu, Xiaoying

    2015-01-01

    We describe a nonenzymatic electrochemical sensor for uric acid. It is based on a carbon nanotube ionic-liquid paste electrode modified with poly(β-cyclodextrin) that was prepared in-situ by electropolymerization. The functionalized multi-walled carbon nanotubes and the surface morphology of the modified electrodes were characterized by transmission electronic microscopy and scanning electron microscopy. The electrochemical response of uric acid was studied by cyclic voltammetry and linear sweep voltammetry. The effects of scan rate, pH value, electropolymerization cycles and accumulation time were also studied. Under optimized experimental conditions and at a working voltage of 500 mV vs. Ag/AgCl (3 M KCl), response to uric acid is linear in the 0.6 to 400 μΜ and in the 0.4 to 1 mΜ concentration ranges, and the detection limit is 0.3 μΜ (at an S/N of 3). The electrode was successfully applied to the detection of uric acid in (spiked) human urine samples. (author)

  2. Changes in suspension properties of structural modified montmorillonites Mudanças em propriedades de suspensões de montmorilonitas modificadas estruturalmente

    Directory of Open Access Journals (Sweden)

    C. Volzone

    2001-03-01

    Full Text Available Rheological changes were found in smectite (Wyoming- and Cheto-type montmorillonites suspensions after structural modifications. The effect of the particle size and Na+ exchange on the flow curves of 6% wt/wt suspensions of smectites with and without Na2CO3 were examined. Mineralogical, structural and physicochemical characteristics were studied by X-ray diffraction (XRD, infrared spectroscopy (IR, cationic exchange capacity (CEC, Mg2+, Al3+ determinations, particle size distribution and swelling index (SI. Grinding in an oscillating mill modified the particle sizes. The montmorillonite grain size and the structural disorder increased after larger grinding times. The grinding treatment modified the apparent viscosity and the yield stress of the montmorillonite suspensions. The homoionic Na Cheto-type montmorillonite with fine particle size (obtained by grinding increased the flow properties. Nevertheless, rheological properties were lower than those of suspensions of the Wyoming-type montmorillonite. Montmorillonite-types reacted differently with Na2CO3 additions and this behavior may be related to their structural composition. The Na2CO3 activation improved the flow properties of the original Wyoming-type montmorillonite and after 30 s grinding.Foram encontradas mudanças reológicas em suspensões de esmectitas (montmorillonitas tipos Wyoming e Cheto após modificações estruturais. Foi examinado o efeito do tamanho de partícula e troca de Na+ nas curvas de escoamento de suspensões de esmectitas 6% peso com e sem Na2CO3. As características mineralógicas, estructurais e físico-químicas foram estudadas por difração de raios X (DRX, espectroscopia no infravermelho (IV, capacidade de troca catiônica (CTC, determinações de Mg2+ e Al3+, de distribuição de tamanho de partículas e de índice de expansão (swelling index - SI. Moagem em moinho oscilatório modificou o tamanho das partículas. O tamanho de grão da montmorillonita e a

  3. Physicochemical Study of Irradiated polypropylene/Organo :Modified Montmorillonite Composites by Using Electron Beam Irradiation Technique

    International Nuclear Information System (INIS)

    Hassan, M.S.

    2008-01-01

    Polypropylene/ Organo modified montmorillonite composites (PP/ OMMT) were prepared by melt blending with a twin screw extruder. The thermal properties by thermo gravimetric analysis (TGA), the dispersion of OMMT of macromolecules by X-ray diffraction (XRD), mechanical properties and the morphology by scanning electron microscopy (SEM) were investigated. The effect of electron beam irradiation on these properties was also studied. The results showed an intercalation between the silicate layers and the PP polymer matrix. The (PP/ OMMT) composites exhibit higher thermal stability and lower mechanical properties than pure polypropylene

  4. Chloroplatinum(II) complex-modified MWCNTs paste electrode for electrochemical determination of mercury in skin lightening cosmetics

    International Nuclear Information System (INIS)

    Isa, Illyas Md; Saidin, Mohamad Idris; Ahmad, Mustaffa; Hashim, Norhayati; Bakar, Suriani Abu; Ali, Noorshida Mohd; Si, Suyanta M.

    2017-01-01

    The chemically modified multiwalled carbon nanotubes (MWCNTs) paste electrode with chloroplatinum(II) complex for the determination of mercury is presented. The chloroplatinum(II) complex was characterized by nuclear magnetic resonance spectroscopy (NMR), Fourier transforms infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). The capability of the electron transfer rate on the surface of modified electrode evaluated is by electrochemical impedance spectroscopy (EIS). The square wave stripping voltammetry (SWSV) technique was employed to investigate the performance of chloroplatinum(II) complex-MWCNTs paste electrode for determination of mercury. Several operational parameters such as the composition ratios of the electrode, type of supporting electrolyte, pH of the solution, and the SWSV parameters were thoroughly investigated. Under optimal conditions, the linear range obtained was from 5.0 μM to 0.1 mM with limit detection of 3.7 μM. The interference from other heavy metals such as Ca 2+ , Mg 2+ , Ni 2+ , Zn 2+ , Cd 2+ , Co 2+ , Ba 2+ , Mn 2+ , and Ce 3+ did not influence the electrochemical response. The chloroplatinum(II) complex-MWCNTs paste electrode was successfully applied to determine mercury in skin lightening cosmetics with a good recovery (98.9%–101.1%).

  5. Cathodic stripping voltammetric determination of arsenic in sugarcane brandy at a modified carbon nanotube paste electrode.

    Science.gov (United States)

    Teixeira, Meryene C; Tavares, Elisângela de F L; Saczk, Adelir A; Okumura, Leonardo L; Cardoso, Maria das Graças; Magriotis, Zuy M; de Oliveira, Marcelo F

    2014-07-01

    We have developed an eletroanalytical method that employs Cu(2+) solutions to determine arsenic in sugarcane brandy using an electrode consisting of carbon paste modified with carbon nanotubes (CNTPE) and polymeric resins. We used linear sweep (LSV) and differential-pulse (DPV) voltammetry with cathodic stripping for CNTPE containing mineral oil or silicone as binder. The analytical curves were linear from 30 to 110μgL(-1) and from 10 to 110μgL(-1) for LSV and DPV, respectively. The limits of detection (L.O.D.) and quantification (L.O.Q.) of CNTPE were 10.3 and 34.5μgL(-1) for mineral oil and 3.4 and 11.2μgL(-1) for silicone. We applied this method to determine arsenic in five commercial sugarcane brandy samples. The results agreed well with those obtained by hydride generation combined with atomic absorption spectrometry (HG AAS). Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Sorption behavior of thorium onto montmorillonite and illite

    International Nuclear Information System (INIS)

    Iida, Yoshihisa; Barr, Logan; Yamaguchi, Tetsuji; Hemmi, Ko

    2016-01-01

    Thorium (Th)-229 is one of the important radionuclides for the performance assessment calculations for high-level radioactive waste repositories. The sorption behavior of Th onto montmorillonite and illite were investigated by batch sorption experiments. Experiments were carried out under variable pH and carbonate concentrations. The sorbability of montmorillonite was higher than that of illite. Distribution coefficients, K d (m 3 kg -1 ), decreased with increased carbonate concentrations and showed the minimal value at around pH 10. The sorption behaviors of Th were analyzed by the non-electrostatic surface complex model with PHREEQC computer program. The model calculations were able to explain the experimental results reasonably well. The decreases of K d was likely due to the stabilization of aqueous species by hydroxo-carbonate complexations in the solutions. (author) [ja

  7. Fabrication of gallium hexacyanoferrate modified carbon ionic liquid paste electrode for sensitive determination of hydrogen peroxide and glucose

    International Nuclear Information System (INIS)

    Haghighi, Behzad; Khosravi, Mehdi; Barati, Ali

    2014-01-01

    Gallium hexacyanoferrate (GaHCFe) and graphite powder were homogeneously dispersed into n-dodecylpyridinium hexafluorophosphate and paraffin to fabricate GaHCFe modified carbon ionic liquid paste electrode (CILPE). Mixture experimental design was employed to optimize the fabrication of GaHCFe modified CILPE (GaHCFe-CILPE). A pair of well-defined redox peaks due to the redox reaction of GaHCFe through one-electron process was observed for the fabricated electrode. The fabricated GaHCFe-CILPE exhibited good electrocatalytic activity towards reduction and oxidation of H 2 O 2 . The observed sensitivities for the electrocatalytic oxidation and reduction of H 2 O 2 at the operating potentials of + 0.8 and − 0.2 V were about 13.8 and 18.3 mA M −1 , respectively. The detection limit (S/N = 3) for H 2 O 2 was about 1 μM. Additionally, glucose oxidase (GOx) was immobilized on GaHCFe-CILPE using two methodology, entrapment into Nafion matrix and cross-linking with glutaraldehyde and bovine serum albumin, in order to fabricate glucose biosensor. Linear dynamic rage, sensitivity and detection limit for glucose obtained by the biosensor fabricated using cross-linking methodology were 0.1–6 mM, 0.87 mA M −1 and 30 μM, respectively and better than those obtained (0.2–6 mM, 0.12 mA M −1 and 50 μM) for the biosensor fabricated using entrapment methodology. - Highlights: • Gallium hexacyanoferrate modified carbon ionic liquid paste electrode was fabricated. • Mixture experimental design was used to optimize electrode fabrication. • Response trace plot was used to show the effect of electrode materials on response. • The sensor exhibited electrocatalytic activity towards H 2 O 2 reduction and oxidation. • Glucose biosensor was fabricated by immobilization of glucose oxidase on sensor

  8. Fe(III)-modified montmorillonite and bentonite: synthesis, chemical and UV-Vis spectral characterization, arsenic sorption, and catalysis of oxidative dehydrogenation of propane

    Czech Academy of Sciences Publication Activity Database

    Grygar, Tomáš; Hradil, David; Bezdička, Petr; Doušová, B.; Čapek, L.; Schneeweiss, Oldřich

    2007-01-01

    Roč. 55, č. 2 (2007), s. 165-176 ISSN 0009-8604 R&D Projects: GA ČR GA202/04/0221; GA AV ČR IAA3032401 Institutional research plan: CEZ:AV0Z40320502; CEZ:AV0Z20410507 Keywords : As sorption * Fe-montmorillonite * Fe- bentonite Subject RIV: CA - Inorganic Chemistry Impact factor: 1.375, year: 2007

  9. Preparation of alanine and tyrosine functionalized graphene oxide nanoflakes and their modified carbon paste electrodes for the determination of dopamine

    International Nuclear Information System (INIS)

    Kumar, Mohan; Swamy, B.E. Kumara; Asif, M.H. Mohammed; Viswanath, C.C.

    2017-01-01

    Highlights: • The prepared graphene oxide was functionalized by alanine and tyrosine. • The prepared materials were used for sensor for dopamine. • The functionalized graphene oxide modified carbon paste electrodes shows good sensitivity, stability and repeatability. - Abstract: Herein, established the synthesis of graphene oxide (GO) by Hummers Method with addition of KMnO_4 followed by thermal heating at 80 °C. The obtained GO was further functionalized by alanine and tyrosine. The prepared GO, alanine functionalized GO nanoflakes (AGONF) and tyrosine functionalized GO nanoflakes (TGONF) were characterized by spectroscopic technique using energy-dispersive spectroscopy (EDS), quantitatively by scanning electron microscopy (SEM) and structural studies along with interlayer distance verified through X-ray diffraction technique. Afterwards, the prepared AGONF and TGONF were used as the modifier for the carbon paste electrode (CPE). The electrochemical behavior of the AGONF and TGONF modified carbon paste electrodes (MCPEs) towards dopamine (DA) in phosphate buffer solution (PBS) were examined by cyclic voltammetric (CV) technique and the obtained consequences showed good electrocatalytic activity of MCPEs by increasing the redox peak current with a lower potential difference compared to the bare CPE (BCPE). The AGONF and TGONF MCPEs were further used for the optimization studies. From the pH studies, it was found that the equal number of proton and electron transfer reaction involved in both the modified electrodes. The scan rate studies demonstrate the adsorption controlled electrode process at AGONF MCPE and diffusion controlled at TGONF MCPE. The oxidation peak current increased linearly with two concentration interval of DA at a range of 2–7 μM and 10–30 μM in presence of PBS (pH 7.4) at MCPEs and the limit of detection (LOD) were found to be 0.84 μM and 0.96 μM for first interval DA concentration range (2–7 μM) at AGONF and TGONF MCPE. The

  10. Preparation of alanine and tyrosine functionalized graphene oxide nanoflakes and their modified carbon paste electrodes for the determination of dopamine

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Mohan [Department of P.G. Studies and Research in Industrial Chemistry, Kuvempu University, Shankaraghatta, 577 451, Shimoga, Karnataka (India); Swamy, B.E. Kumara, E-mail: kumaraswamy21@yahoo.com [Department of P.G. Studies and Research in Industrial Chemistry, Kuvempu University, Shankaraghatta, 577 451, Shimoga, Karnataka (India); Asif, M.H. Mohammed [Nanoscience and Technology, Kuvempu University, Shankaraghatta, 577451, Shimoga, Karnataka (India); Viswanath, C.C. [Department of P.G. Studies and Research in Industrial Chemistry, Kuvempu University, Shankaraghatta, 577 451, Shimoga, Karnataka (India)

    2017-03-31

    Highlights: • The prepared graphene oxide was functionalized by alanine and tyrosine. • The prepared materials were used for sensor for dopamine. • The functionalized graphene oxide modified carbon paste electrodes shows good sensitivity, stability and repeatability. - Abstract: Herein, established the synthesis of graphene oxide (GO) by Hummers Method with addition of KMnO{sub 4} followed by thermal heating at 80 °C. The obtained GO was further functionalized by alanine and tyrosine. The prepared GO, alanine functionalized GO nanoflakes (AGONF) and tyrosine functionalized GO nanoflakes (TGONF) were characterized by spectroscopic technique using energy-dispersive spectroscopy (EDS), quantitatively by scanning electron microscopy (SEM) and structural studies along with interlayer distance verified through X-ray diffraction technique. Afterwards, the prepared AGONF and TGONF were used as the modifier for the carbon paste electrode (CPE). The electrochemical behavior of the AGONF and TGONF modified carbon paste electrodes (MCPEs) towards dopamine (DA) in phosphate buffer solution (PBS) were examined by cyclic voltammetric (CV) technique and the obtained consequences showed good electrocatalytic activity of MCPEs by increasing the redox peak current with a lower potential difference compared to the bare CPE (BCPE). The AGONF and TGONF MCPEs were further used for the optimization studies. From the pH studies, it was found that the equal number of proton and electron transfer reaction involved in both the modified electrodes. The scan rate studies demonstrate the adsorption controlled electrode process at AGONF MCPE and diffusion controlled at TGONF MCPE. The oxidation peak current increased linearly with two concentration interval of DA at a range of 2–7 μM and 10–30 μM in presence of PBS (pH 7.4) at MCPEs and the limit of detection (LOD) were found to be 0.84 μM and 0.96 μM for first interval DA concentration range (2–7 μM) at AGONF and TGONF MCPE

  11. Preparation of polypyrrole/ferrocyanide films modified carbon paste electrode and its application on the electrocatalytic determination of ascorbic acid

    Energy Technology Data Exchange (ETDEWEB)

    Raoof, Jahan-Bakhsh; Ojani, Reza; Rashid-Nadimi, Sahar

    2004-01-15

    Functionalized polypyrrole film were prepared by incorporation of (Fe(CN){sub 6}){sup 4-} as doping anion, during the electropolymerization of pyrrole onto a carbon paste electrode (CPE) in aqueous solution by using potentiostatic method. The electrochemical behavior of the (Fe(CN){sub 6}){sup 3-}/(Fe(CN){sub 6}){sup 4-} redox couple in polypyrrole was studied by cyclic voltammetry and double step potential chronoamperometry methods. In this study, an obvious surface redox reaction was observed and dependence of this reaction on the solution pH was illustrated. The electrocatalytic ability of polypyrrole/ferrocyanide films modified carbon paste electrode (Ppy/FCNMCPEs) was demonstrated by oxidation of ascorbic acid. It has been found that under optimum condition (pH 7.00), the oxidation of ascorbic acid at the surface of such electrode occurs at a potential about 540 mV less positive than unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient, {alpha} and catalytic reaction rate constant, k{sub h}', were also determined by using various electrochemical approaches. The catalytic oxidation peak current showed a linear dependent on the ascorbic acid concentration and a linear calibration curve was obtained in the range of 4.5x10{sup -4} to 9.62x10{sup -3} M of ascorbic acid with a correlation coefficient of 0.9999. The detection limit (2{sigma}) was determined as 5.82x10{sup -5} M.

  12. Nitrate sorption on activated carbon modified with CaCl2: Equilibrium, isotherms and kinetics

    Directory of Open Access Journals (Sweden)

    Zanella Odivan

    2015-01-01

    Full Text Available In this study, nitrate (NO3- removal from aqueous solutions was investigated using granular activated carbon (GAC modified with CaCl2. Batch sorption studies were performed as a function of sorbent dose, initial nitrate concentration and pH. Sorption was maximized between pH 3 and 9. Studies on the effect of pH showed that the ion exchange mechanism might be involved in the sorption process. The percentage of nitrate removed increased with increasing sorbent concentration, and the ideal sorbent dose was found to be 20 g•L-1. Four isotherm models-Langmuir, Freundlich, Redlich-Peterson and Sips-were used to fit the experimental data. The Redlich-Peterson isotherm model explained the sorption process well and showed the best coefficient of determination (0.9979 and Chi-square test statistic (0.0079. Using the Sips isotherm model, the sorption capacity (qe was found to be 1.93 mg nitrate per g of sorbent. Kinetic experiments indicated that sorption was a fast process, reaching equilibrium within 120 min. The nitrate sorption kinetic data were successfully fitted to a pseudo-second-order kinetic model. The overall results demonstrated potential applications of modified GAC for nitrate removal from aqueous solutions.

  13. Transient Thermal Stability of Polymer Nanocomposites

    Science.gov (United States)

    2012-08-01

    modified Montmorillonite, Nanocor masterbatch ) 1 wt % carbon black (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2·nH2O Multiwalled Carbon Nanotubes (Nanocyl... masterbatch ) Twin screw extrusion (190C) Slow Heating Regime Thermogravimetric Analysis Nanospecies improve thermal stability as expected Laser

  14. Cerium Modified Pillared Montmorillonite Supported Cobalt Catalysts for Fischer Tropsch Synthesis

    International Nuclear Information System (INIS)

    Ahmad, N.; Ali, Z.; Abbas, S. M.; Hussain, F.

    2015-01-01

    Fischer-Tropsch (FT) synthesis was accomplished over Al-pillared Montmorillonite supported 20 wt% Co modified with different weight% of cerium catalysts. These catalysts were prepared by impregnation method while structural characterizations of the prepared samples were performed by XRD, TPR, NH/sub 3/TPD, TGA, BET, XRF and SEM techniques. The Fischer Tropsch reaction was studied in fixed bed micro catalytic reactor at temperature range of 220, 260 and 275 degree C and at different pressure (1, 5 and 10 bars). From the activity results, it was found that by pillaring NaMMT with Al higher catalytic activity and lower methane selectivity of NaMMT was achieved. Furthermore, the results of FT synthesis reaction revealed that cerium incorporation increased the dispersion of Co/sub 3/O/sub 4/ on the surface and consequently resulted in enhanced catalytic activity. Additionally, the C/sub 5/-C/sub 12/ hydrocarbons and methane selectivity increased while C/sub 22+/ hydrocarbons selectivity was decreased over cerium modified catalysts. Higher reaction temperature (>220 degree C) resulted in significant enhancement in CO conversion and methane selectivity. Though, increase in pressure from 1 to 10 bars eventually resulted in increase in C/sub 5+/ hydrocarbons and decrease in methane and C/sub 2/-C/sub 5/ hydrocarbons selectivity. (author)

  15. Synthesis and Characterization of Polystyrene-Montmorillonite Nanocomposite Particles Using an Anionic-Surfactant-Modified Clay and Their Friction Performance

    Directory of Open Access Journals (Sweden)

    Chengcheng Yu

    2018-06-01

    Full Text Available Polystyrene-organo-montmorillonite (PS-OMMT nanocomposite particles were prepared via emulsion polymerization of styrene in the presence of montmorillonite modified with an anionic surfactant, sodium lauryl sulfonate (SLS, and its tribological properties as an additive to polyalphaolefin (PAO were tested. The results of Fourier transform infrared spectroscopy (FT-IR, X-ray diffraction (XRD and thermogravimetric analysis (TGA showed that SLS molecules resided in the montmorillonite (MMT interlayer space. The effects of OMMT on the morphology and properties of the nanocomposites were also investigated. Gel permeation chromatography (GPC and dynamic light scattering (DLS demonstrate that the presence of OMMT can effectively reduce the average molecular weight and average particle size of PS. XRD and transmission electron microscopy (TEM of the PS-OMMT nanocomposites indicate that exfoliated and intercalated structures form and that the MMT layers either are partly embedded inside the PS particles or remain on their surface. Compared with pure PS, the PS-OMMT nanocomposites possessed higher stability to thermal decomposition and higher glass transition temperatures. Adding nanocomposite particles reduces the friction coefficient, and thus, the antiwear properties of the PAO are significantly improved. The PS-OMMT-3 (3 wt % of OMMT based on styrene particles have the best tribological performance and maintained a stable, very low coefficient of friction of 0.09.

  16. Properties of a epoxy-based powder coating containing modified montmorillonite with cerium

    International Nuclear Information System (INIS)

    Beux, A.R.D.; Piazza, D.; Zattera, A.J.; Ferreira, C.A.; Scienza, L.C.

    2014-01-01

    Organic coatings are widely used to prevent corrosion in metal structures. The incorporation of nanofiller the polymer matrix in order to obtain polymer nanocomposites has been arousing scientific and technological interest, because it provides significant improvements when incorporated into pure polymeric materials or conventional composites. In the present study were been developed epoxy-based powder coating with addition of different concentrations (2, 4 and 8% (w / w)) of the montmorillonite type Cloisite® 15A modified with cerium in the melt state on a double-screw extruder co-rotating. The coatings were characterized by average particle size, time (gel time) gel, X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Coatings with intercalated structure was observed in the XRD analysis and confirmed by SEM to the observe an increase in the concentration of tactoids an increased filler content. (author)

  17. Carbonation of calcium aluminate cement pastes

    Directory of Open Access Journals (Sweden)

    Fernández-Carrasco, L.

    2001-12-01

    Full Text Available This work discusses the results from accelerated tests intended to investigate the ways the different curing methods affect the carbonation of calcium aluminate cements pastes (CAC. The research was focused on the mineralogical composition of hydrated and carbonated samples. The compressive strengths and the porosity of the samples have been determined. Results point out that vaterite and aragonite are formed as a result of carbonation of both cubic and hexagonal calcium aluminate hydrates. The polymorph of calcium carbonate formed does not depend on the curing process. Carbonation rates is higher in hexagonal than in cubic hydrates. Results obtained through this study evidence that, as a consequence of the carbonation process of CAC pastes, in test conditions, an increase of the mechanical strengths occurs.

    En el presente trabajo se discuten los resultados obtenidos en los ensayos acelerados llevados a cabo para investigar los efectos de diferentes métodos de curado sobre la carbonatacion de pastas del cemento de aluminato de calcio (CAC. Se estudió la composición mineralógica de las muestras hidratadas y carbonatadas. Además, se determinaron las resistencias mecánicas a compresión y la porosidad de las probetas. Los resultados indican que la vaterita y el aragonito son las polimorfías del CaCO3 que se forman al carbonatar los aluminatos cálcicos hidratos, tanto los de naturaleza hexagonal como cúbica. El polimorfo del carbonato cálcico formado no depende del proceso de curado. La velocidad de carbonatación de los hidratos hexagonales es mayor que la de los cúbicos. Los resultados obtenidos en el presente trabajo han evidenciado que como consecuencia del proceso de carbonatación sobre pastas de CAC, en las condiciones realizadas, se produce un incremento en las resistencias mecánicas.

  18. Mechanism of 3,4-dihydroxybenzaldehyde electropolymerization at carbon paste electrodes : catalytic detection of NADH

    Directory of Open Access Journals (Sweden)

    Delbem Maria Flávia

    2002-01-01

    Full Text Available Cyclic voltammetry was used to study 3,4-dihydroxybenzaldehyde (3,4-DHB electropolymerization processes on carbon paste electrodes. The characteristics of the electropolymerized films were highly dependent on pH, anodic switching potential, scan rate, 3,4-DHB concentrations and number of cycles. Film stability was determined in citrate/phosphate buffer solutions at the same pH used during the electropolymerization process. The best conditions to prepare carbon paste modified electrodes were pH 7.8; 0.0 <= Eapl <= 0.25 V; 10 mV s-1; 0.25 mmol L-1 3,4-DHB and 10 scans. These carbon paste modified electrodes were used for NADH catalytic detection at 0.23 V in the range 0.015 <= [NADH] <= 0.21 mmol L-1. Experimental data were used to propose a mechanism for the 3,4--DHB electropolymerization processes, which involves initial phenoxyl radical formation.

  19. Voltammetric copper(2) determination with a montmorillonite - modified carbon paste electrode

    Czech Academy of Sciences Publication Activity Database

    Kula, Petr; Navrátilová, Zuzana

    1996-01-01

    Roč. 354, 5-6 (1996), s. 692-695 ISSN 0937-0633. [International Hans Wolfgang Nürnberg Memorial Symposium on Metal Compounds in Environment and Life /6./. Jülich, 09.05.1995-12.05.1995] R&D Projects: GA ČR GA203/93/0363 Impact factor: 1.038, year: 1996

  20. Comparison of two fabricated aptasensors based on modified carbon paste/oleic acid and magnetic bar carbon paste/Fe3O4@oleic acid nanoparticle electrodes for tetracycline detection.

    Science.gov (United States)

    Jahanbani, Shahriar; Benvidi, Ali

    2016-11-15

    In this research, we have improved two aptasensors based on a modified carbon paste electrode (CPE) with oleic acid (OA), and a magnetic bar carbon paste electrode (MBCPE) with Fe3O4 magnetic nanoparticles and oleic acid (OA). After the immobilization process of anti-TET at the electrode surfaces, the aptasensors were named CPE/OA/anti-TET and MBCPE/Fe3O4NPs/OA/anti-TET respectively. In this paper, the detection of tetracycline is compared using CPE/OA/anti-TET and MBCPE/Fe3O4NPs/OA/anti-TET aptasensors. These modified electrodes were characterized by infrared spectroscopy (IR), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), UV-vis spectroscopy, and voltammetric methods. The linear range and the detection limit for TET with the CPE/OA/anti-TET aptasensor were found to be 1.0×10(-12)-1.0×10(-7)M and 3.0×10(-13)M respectively by EIS method. The linear range and the detection limit for TET with the CPE/OA/anti-TET aptasensor were found to be 1.0×10(-10)-1.0×10(-7)M with a limit of detection of 2.9×10(-11)M using differential pulse voltammetry (DPV) technique. The MBCPE/Fe3O4NPs/OA/anti-TET aptasensor was used for determination of TET, and a liner range of 1.0×10(-14)-1.0×10(-6)M with a detection limit of 3.8×10(-15)M was obtained by EIS method. Also, the linear range and detection limit of 1.0×10(-12)-1.0×10(-6)M and 3.1×10(-13)M respectively, were obtained for MBCPE/Fe3O4NPs/OA/anti-TET aptasensor using DPV. The proposed aptasensors were applied for determination of tetracycline in some real samples such as drug, milk, honey and blood serum samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Preparation and characterization of silver loaded montmorillonite modified with sulfur amino acid

    Energy Technology Data Exchange (ETDEWEB)

    Li, Tian, E-mail: phdlitian@163.com; Lin, Oulian; Lu, Zhiyuan; He, Liuimei; Wang, Xiaosheng

    2014-06-01

    The Na{sup +} montmorillonite (MMT) was modified with sulfur containing amino acid (L-cystine, L-cysteine or L-methionine) and characterized by energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectrum (FT-IR). The results showed the modification was smooth and the surface condition of MMT was changed with sulfur containing groups. Then silver was loaded on the modified MMTs via ion-exchange reaction under microwave irradiation, the spectra of X-ray photoelectron spectroscopy (XPS), EDS and FT-IR confirmed the successful loading of massive silver and the strong interaction between sulfur and silver, the silver loaded L-cystine modified MMT (Ag@AA-MMT-3) with a silver content of 10.93 wt% was the highest of all. Further more, the Ag@AA-MMT-3 was under the irradiation of a UV lamp to turn silver ions to silver nano particles (Ag NPs). The XPS, specific surface area (SSA), transmission electron microscopy (TEM), XRD patterns and UV–vis spectra proved the existence of uniform nano scaled metallic Ag NPs. By contrast, the UV irradiated Ag@AA-MMT-3 (Ag@AA-MMT-UV) showed a much better slow release property than Ag@AA-MMT-3 or Ag@MMT. The Ag@AA-MMT-UV showing a large inhibition zone and high inhibition ratio presented very good antibacterial property.

  2. Determination of Diclofenac on a Dysprosium Nanowire- Modified Carbon Paste Electrode Accomplished in a Flow Injection System by Advanced Filtering

    Directory of Open Access Journals (Sweden)

    Ali Akbar Moosavi-Movahedi

    2009-09-01

    Full Text Available A new detection technique called Fast Fourier Transform Square-Wave Voltammetry (FFT SWV is based on measurements of electrode admittance as a function of potential. The response of the detector (microelectrode, which is generated by a redox processes, is fast, which makes the method suitable for most applications involving flowing electrolytes. The carbon paste electrode was modified by nanostructures to improve sensitivity. Synthesized dysprosium nanowires provide a more effective nanotube-like surface [1-4] so they are good candidates for use as a modifier for electrochemical reactions. The redox properties of diclofenac were used for its determination in human serum and urine samples. The support electrolyte that provided a more defined and intense peak current for diclofenac determination was a 0.05 mol L−1 acetate buffer pH = 4.0. The drug presented an irreversible oxidation peak at 850 mV vs. Ag/AgCl on a modified nanowire carbon paste electrode which produced high current and reduced the oxidation potential by about 100 mV. Furthermore, the signal-to-noise ratio was significantly increased by application of a discrete Fast Fourier Transform (FFT method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. To obtain the much sensivity the effective parameters such as frequency, amplitude and pH was optimized. As a result, CDL of 2.0 × 10−9 M and an LOQ of 5.0 × 10−9 M were found for the determination for diclofenac. A good recovery was obtained for assay spiked urine samples and a good quantification of diclofenac was achieved in a commercial formulation.

  3. Fabrication of gallium hexacyanoferrate modified carbon ionic liquid paste electrode for sensitive determination of hydrogen peroxide and glucose

    Energy Technology Data Exchange (ETDEWEB)

    Haghighi, Behzad, E-mail: haghighi@iasbs.ac.ir; Khosravi, Mehdi; Barati, Ali

    2014-07-01

    Gallium hexacyanoferrate (GaHCFe) and graphite powder were homogeneously dispersed into n-dodecylpyridinium hexafluorophosphate and paraffin to fabricate GaHCFe modified carbon ionic liquid paste electrode (CILPE). Mixture experimental design was employed to optimize the fabrication of GaHCFe modified CILPE (GaHCFe-CILPE). A pair of well-defined redox peaks due to the redox reaction of GaHCFe through one-electron process was observed for the fabricated electrode. The fabricated GaHCFe-CILPE exhibited good electrocatalytic activity towards reduction and oxidation of H{sub 2}O{sub 2}. The observed sensitivities for the electrocatalytic oxidation and reduction of H{sub 2}O{sub 2} at the operating potentials of + 0.8 and − 0.2 V were about 13.8 and 18.3 mA M{sup −1}, respectively. The detection limit (S/N = 3) for H{sub 2}O{sub 2} was about 1 μM. Additionally, glucose oxidase (GOx) was immobilized on GaHCFe-CILPE using two methodology, entrapment into Nafion matrix and cross-linking with glutaraldehyde and bovine serum albumin, in order to fabricate glucose biosensor. Linear dynamic rage, sensitivity and detection limit for glucose obtained by the biosensor fabricated using cross-linking methodology were 0.1–6 mM, 0.87 mA M{sup −1} and 30 μM, respectively and better than those obtained (0.2–6 mM, 0.12 mA M{sup −1} and 50 μM) for the biosensor fabricated using entrapment methodology. - Highlights: • Gallium hexacyanoferrate modified carbon ionic liquid paste electrode was fabricated. • Mixture experimental design was used to optimize electrode fabrication. • Response trace plot was used to show the effect of electrode materials on response. • The sensor exhibited electrocatalytic activity towards H{sub 2}O{sub 2} reduction and oxidation. • Glucose biosensor was fabricated by immobilization of glucose oxidase on sensor.

  4. Electrospun composite nanofibers of poly vinyl pyrrolidone and zinc oxide nanoparticles modified carbon paste electrode for electrochemical detection of curcumin

    Energy Technology Data Exchange (ETDEWEB)

    Afzali, Moslem, E-mail: moslem_afzali@yahoo.com [Chemistry Department, Shahid Bahonar University of Kerman, Kerman (Iran, Islamic Republic of); Young Research Society, Shahid Bahonar University of Kerman, Kerman (Iran, Islamic Republic of); Mostafavi, Ali; Shamspur, Tayebeh [Chemistry Department, Shahid Bahonar University of Kerman, Kerman (Iran, Islamic Republic of)

    2016-11-01

    A simple and novel ferrocene-nanofiber carbon paste electrode was developed to determine curcumin in a phosphate buffer solution at pH = 8. ZnO nanoparticles were produced via a sonochemical process and composite nanofibers of PVP/ZnO were prepared by electrospinning. The characterization was performed by SEM, XRD and IR. The results suggest that the electrospun composite nanofibers having a large surface area promote electron transfer for the oxidation of curcumin and hence the FCNFCPE exhibits high electrocatalytic activity and performs well in regard to the oxidation of curcumin. The proposed method was successfully applied for measurement of curcumin in urine and turmeric as real samples. - Highlights: • A novel ferrocene-nanofiber carbon paste electrode is presented to determine an anticancer material curcumin. • Composite nanofibers of PVP and zinc oxide nanoparticles with average diameter of 64 nm, were produced by electrospinning. • High surface area of nanofibers resulted in high effective surface of the electrode increases sensitivity of the method. • This modified electrode is successfully employed for determining curcumin in real samples and LOD was 0.024 μM.

  5. Carbon Paste Electrode Modified with Carbamoylphosphonic Acid Functionalized Mesoporous Silica: A New Mercury-Free Sensor for Uranium Detection

    International Nuclear Information System (INIS)

    Yantasee, Wassana; Lin, Yuehe; Fryxell, Glen E.; Wang, Zheming

    2004-01-01

    This study reports a new approach for developing a uranium (U(VI)) electrochemical sensor that is mercury-free, solid-state, and has less chance for ligand depletion than existing sensors. A carbon-paste electrode modified with carbamoylphosphonic acid self-assembled monolayer on mesoporous silica was developed for uranium detection based on an adsorptive square-wave stripping voltammetry technique. Voltammetric responses for U(VI) detection are reported as a function of pH, preconcentration time, and aqueous phase U(VI) concentration. The uranium detection limit is 25 ppb after 5 minutes preconcentration and improved to 1 ppb after 20 minutes preconcentration. The relative standard deviations are normally less than 5%

  6. In-vivo study of genotoxic and inflammatory effects of the organo-modified Montmorillonite Cloisite® 30B

    DEFF Research Database (Denmark)

    Sharma, Anoop Kumar; Mortensen, Alicja; Schmidt, Bjørn

    2014-01-01

    exposure to clay particles from Cloisite® 30B. Detection and identification of free quaternary ammonium modifier in the highest dose of Cloisite® 30B was carried out by high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF-MS). This analysis revealed...... a mixture of three quaternary ammonium analogues. The detected concentration of the organomodifier corresponded to an exposure of rats to about 5 mg quaternary ammonium analogues/kg body weight.......Because of the increasing use of clays and organoclays in industrial applications it is of importance to consider the toxicity of these materials. Recently it was reported that the commercially available Montmorillonite clay, Cloisite® 30B, which is surface-modified by organic quaternary ammonium...

  7. Highly sensitive and selective determination of methylergometrine maleate using carbon nanofibers/silver nanoparticles composite modified carbon paste electrode.

    Science.gov (United States)

    Kalambate, Pramod K; Rawool, Chaitali R; Karna, Shashi P; Srivastava, Ashwini K

    2016-12-01

    A highly sensitive and selective voltammetric method for determination of Methylergometrine maleate (MM) in pharmaceutical formulations, urine and blood serum samples has been developed based on enhanced electrochemical response of MM at carbon nanofibers and silver nanoparticles modified carbon paste electrode (CNF-AgNP-CPE). The electrode material was characterized by various techniques viz., X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The electrocatalytic response of MM at CNF-AgNP-CPE was studied by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). Under optimized conditions, the proposed sensor exhibits excellent electrochemical response towards MM. The DPV study shows greatly enhanced electrochemical signal for MM at CNF-AgNP-CPE lending high sensitivity to the proposed sensor for MM detection. The peak (Ip) current for MM is found to be rectilinear in the range 4.0×10(-8)-2.0×10(-5)M with a detection limit of 7.1×10(-9)M using DPV. The feasibility of the proposed sensor in analytical applications was investigated by conducting experiments on commercial pharmaceutical formulations, human urine and blood serum samples, which yielded satisfactory recoveries of MM. The proposed electrochemical sensor offers high sensitivity, selectivity, reproducibility and practical utility. We recommend it as an authentic and productive electrochemical sensor for successful determination of MM. Copyright © 2016. Published by Elsevier B.V.

  8. Carbon nanotube/paraffin/montmorillonite composite phase change material for thermal energy storage.

    Science.gov (United States)

    Li, Min; Guo, Qiangang; Nutt, Steven

    2017-04-01

    A composite phase change material (PCM) comprised of organic montmorillonite (OMMT)/paraffin/grafted multi-walled nanotube (MWNT) is synthesized via ultrasonic dispersion and liquid intercalation. The microstructure of the composite PCM has been characterized to determine the phase distribution, and thermal properties (latent heat and thermal conductivity) have been measured by differential scanning calorimetry (DSC) and a thermal constant analyzer. The results show that paraffin molecules are intercalated in the montmorillonite layers and the grafted MWNTs are dispersed in the montmorillonite layers. The latent heat is 47.1 J/g, and the thermal conductivity of the OMMT/paraffin/grafted MWNT composites is 34% higher than that of the OMMT/paraffin composites and 65% higher than that of paraffin.

  9. Carbon paste electrodes in electroanalytical chemistry

    Directory of Open Access Journals (Sweden)

    KAREL VYTŘAS

    2009-09-01

    Full Text Available An overview is given dealing with the applications of carbon paste electrodes in equilibrium potentiometry as well as in electrochemical stripping analysis using both voltammetric and potentiometric modes. Various modifications of carbon pastes and carbon paste-based biosensors are also mentioned. The main emphasis in this article is directed at summarizing recent results of the authors’ research group during the past few years.

  10. Characterization and Identification of Bituminous Materials Modified with Montmorillonite Nanoclay

    NARCIS (Netherlands)

    Liu, G.

    2011-01-01

    Montmorillonite (Mt) nanoclay is a layered silicate mineral with a 2:1-type layer structure, two tetrahedrals sandwiching one octahedral. In recent decades, it is successfully introduced into polymer systems to form polymer-clay nanocomposites (PCN) in which the silicate layers of the Mt are

  11. Synthesis of poly(furfuryl alcohol)/montmorillonite nanocomposites ...

    Indian Academy of Sciences (India)

    The purpose of this study was to obtain poly(furfuryl alcohol) nanocomposites with Algerian organically modified clay (termed 12-montmorillonite). The formation of poly(furfuryl alcohol) was confirmed by infrared spectroscopy (IR); the prepared nanocomposites were characterized by X-ray diffraction (XRD), transmission ...

  12. Investigations on uranium sorption on bentonite and montmorillonite, respectively, and uranium in environmental samples; Untersuchungen zur Uransorption an Bentonit bzw. Montmorillonit sowie von Uran in Umweltproben

    Energy Technology Data Exchange (ETDEWEB)

    Azeroual, Mohamed

    2010-09-22

    The geotechnical barrier is an important component of a geological repository and consists of compacted bentonite surrounding radioactive waste containers. Its most important functions are, to retard the radionuclide migration into the biosphere and to prevent groundwater contact with containers. lt is therefore of central importance to investigate the bentonite material on its capacity to sorb radionuclides under near-natural chemical and physical conditions. The purpose of this work was to study the adsorption of uranium(VI) on bentonit and on montmorillonite-standards at high uranium concentrations. Thereby, a special account was given to the calcium-uranyl-carbonate complexation, which leads to the formation of very stable and mobile uncharged Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3} complex. Results of batch experiments showed that the dicalcium-uranyl-tricarbonate complexation lowers the uranium(VI) sorption on natural clay (bentonite) by a factor of up to 3. After 21 days of contact time, about 40 % and 20 % of the initial uranium(VI)concentration were sorbed on Na-bentonite and ea-bentonite, respectively, from a solution with Ca{sub 2}UO{sub 2}(CO{sub 3}){sub 3} dominating the uranium(VI) speciation. On the contrary, about 55 % of the initial uranium(VI)-concentration were sorbed on thes clays from the solution, in which (UO{sub 2}){sub 2}CO{sub 3}(OH){sub 3}{sup -} complex dominated the uranium(VI) speciation. Thus uranium(VI) sorption is more strongly influenced by the solution composition than by bentonite type. Na-bentonite should be used instead of ea-bentonite as a geotechnical barrier, since calcium-uranyl-carbonate complexation may be a realistic scenario. Further SEM-EDX and HREM-EDX studies showed that uranium(VI) sorption occurred predominantly on montmorillonite, which is the main component of bentonite. Uranium(VI) sorption on bentonite's accessory Minerals (pyrite, calcite, mica, and feldspar) was not observed. Investigation of uranium

  13. Montmorillonite dissolution kinetics: Experimental and reactive transport modeling interpretation

    Science.gov (United States)

    Cappelli, Chiara; Yokoyama, Shingo; Cama, Jordi; Huertas, F. Javier

    2018-04-01

    The dissolution kinetics of K-montmorillonite was studied at 25 °C, acidic pH (2-4) and 0.01 M ionic strength by means of well-mixed flow-through experiments. The variations of Si, Al and Mg over time resulted in high releases of Si and Mg and Al deficit, which yielded long periods of incongruent dissolution before reaching stoichiometric steady state. This behavior was caused by simultaneous dissolution of nanoparticles and cation exchange between the interlayer K and released Ca, Mg and Al and H. Since Si was only involved in the dissolution reaction, it was used to calculate steady-state dissolution rates, RSi, over a wide solution saturation state (ΔGr ranged from -5 to -40 kcal mol-1). The effects of pH and the degree of undersaturation (ΔGr) on the K-montmorillonite dissolution rate were determined using RSi. Employing dissolution rates farthest from equilibrium, the catalytic pH effect on the K-montmorillonite dissolution rate was expressed as Rdiss = k·aH0.56±0.05 whereas using all dissolution rates, the ΔGr effect was expressed as a non-linear f(ΔGr) function Rdiss = k · [1 - exp(-3.8 × 10-4 · (|ΔGr|/RT)2.13)] The functionality of this expression is similar to the equations reported for dissolution of Na-montmorillonite at pH 3 and 50 °C (Metz, 2001) and Na-K-Ca-montmorillonite at pH 9 and 80 °C (Cama et al., 2000; Marty et al., 2011), which lends support to the use of a single f(ΔGr) term to calculate the rate over the pH range 0-14. Thus, we propose a rate law that also accounts for the effect of pOH and temperature by using the pOH-rate dependence and the apparent activation energy proposed by Rozalén et al. (2008) and Amram and Ganor (2005), respectively, and normalizing the dissolution rate constant with the edge surface area of the K-montmorillonite. 1D reactive transport simulations of the experimental data were performed using the Crunchflow code (Steefel et al., 2015) to quantitatively interpret the evolution of the released cations

  14. Study of CaCl2 as an agent that modifies the surface of activated carbon used in sorption/treatment cycles for nitrate removal

    Directory of Open Access Journals (Sweden)

    O. Zanella

    2014-03-01

    Full Text Available The efficiency of the application of a chemically-modified activated carbon surface was investigated. The purpose of this study was to examine the effect of treatment with CaCl2 solution at a concentration of 2000 mg.L-1 on the sorption of nitrate ions from aqueous solutions in successive sorption/t reatment cycles. The sorbent was initially subjected to chemical treatment with CaCl2 and subsequently to the sorption process. Nine sorption cycles were performed. The concentrations of nitrate ions in the solution were measured by UV-Vis spectrophotometry before and after sorption. The results show that treatment with CaCl2 caused a significant increase in the percentage removal for each treatment step, reaching a removal rate of 80% of nitrate in the solution after nine cycles.

  15. Electrochemical behaviour of carbon paste electrodes enriched with tin oxide nanoparticles using voltammetry and electrochemical impedance spectroscopy.

    Science.gov (United States)

    Muti, Mihrican; Erdem, Arzum; Caliskan, Ayfer; Sınag, Ali; Yumak, Tugrul

    2011-08-01

    The effect of the SnO(2) nanoparticles (SNPs) on the behaviour of voltammetric carbon paste electrodes were studied for possible use of this material in biosensor development. The electrochemical behaviour of SNP modified carbon paste electrodes (CPE) was first investigated by using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. The performance of the SNP modified electrodes were compared to those of unmodified ones and the parameters affecting the response of the modified electrode were optimized. The SNP modified electrodes were then tested for the electrochemical sensing of DNA purine base adenine to explore their further development in biosensor applications. Copyright © 2011 Elsevier B.V. All rights reserved.

  16. Probing the internal calcification chemistry of O. universa using B/Ca

    Science.gov (United States)

    Holland, K.; Eggins, S.; Hoenisch, B.; Haynes, L.; Russell, A. D.

    2014-12-01

    The B/Ca, U/Ca ratio values of calcitic foraminifer shells are all influenced by seawater carbonate chemistry (seawater [B(OH)4-/HCO3-], [CO32-], and pH respectively), and as such are increasingly being used as proxies to reconstruct past changes in ocean inorganic carbon content, saturation state and pH. However, the behavior of these proxies is subject to modification by foraminifers' efforts to regulate the conditions under which they grow their shells. We have undertaken experiments on Orbulina universa that manipulate synthetic culture water DIC, pH and [Ca] in an effort to disentangle the biological versus environmental influences of seawater carbonate system and saturation state on B/Ca, U/Ca and Mg/Ca ratio into foraminiferal calcite. Experiments were designed to be able determine the extent to which foraminifers are able to modify the chemical composition of their (vacuolized?) internal calcification fluid, in particular by using B/Ca and U/Ca as sensors for calcification chemistry (i.e. internal [B(OH)4-/HCO3-] and [CO32-]) . We have used a high resolution LA-ICPMS depth profiling techniques to characterize the amplitude of B/Ca, U/Ca, Mg/Ca, and Sr/Ca ratio values across and the thickness (calcification rate) of diurnal bands that are developed in individual shells grown under different synthetic seawater compositions. Results indicate Orbulina universa modify the chemistry of their calcification fluid far from that of external seawater, but are not able to mitigate changes in external seawater. This most likely achieved through the interactive effects of internal pH manipulation and a carbon concentration mechanism. Our results are likely to have important implications for the interpretation of Mg/Ca, B/Ca and U/Ca as proxies seawater temperatures and carbonate system parameters.

  17. Determination of picomolar silver concentrations by differential pulse anodic stripping voltammetry at a carbon paste electrode modified with phenylthiourea-functionalized high ordered nanoporous silica gel

    International Nuclear Information System (INIS)

    Javanbakht, Mehran; Divsar, Faten; Badiei, Alireza; Fatollahi, Fatemeh; Khaniani, Yeganeh; Ganjali, Mohammad Reza; Norouzi, Parviz; Chaloosi, Marzieh; Ziarani, Ghodsi Mohammadi

    2009-01-01

    This study introduces the design of an anodic stripping voltammetric (ASV) method for the silver ion determination at a carbon paste electrode (CPE), chemically modified with phenylthiourea-nanoporous silica gel (Tu-SBA-15-CPE). The electroanalytical pro includes two steps: preconcentration of metal ions at an electrode surface, followed by quantification of the accumulated species by differential pulse anodic stripping voltammetric methods. Factors affecting the performance of the anodic stripping were investigated, including the modifier quantity in the paste, the electrolyte concentrations, the solution pH and the accumulation potential or time. The most sensitive and reliable electrode contained 10% Tu-SBA-15 and 90% carbon paste. The accumulation potential and time were set at, -200 mV and 300 s, respectively, and the scan rate at 50 mV s -1 in the scan range of -200 to 700 mV. The resulting electrode demonstrated a linear response over range of silver ion concentration of 8.0-80 pmol/L with detection limit (S/N = 3) of 5 pmol/L. The prepared electrodes were used for the silver determination in sea and tap water samples and very good recovery results were obtained. The accuracy was assessed through recovery experiments and independent analysis by graphite furnace atomic absorption spectrometry.

  18. Determination of picomolar silver concentrations by differential pulse anodic stripping voltammetry at a carbon paste electrode modified with phenylthiourea-functionalized high ordered nanoporous silica gel

    Energy Technology Data Exchange (ETDEWEB)

    Javanbakht, Mehran [Department of Chemistry, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Nano Science and Technology Research Center, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of)], E-mail: mehranjavanbakht@gmail.com; Divsar, Faten [Department of Chemistry, University of Tarbiat Moallem, Tehran (Iran, Islamic Republic of); Badiei, Alireza [School of Chemistry, University College of Science, University of Tehran, Tehran (Iran, Islamic Republic of); Fatollahi, Fatemeh [Department of Chemistry, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Khaniani, Yeganeh [School of Chemistry, University College of Science, University of Tehran, Tehran (Iran, Islamic Republic of); Ganjali, Mohammad Reza; Norouzi, Parviz [Center of Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, Tehran (Iran, Islamic Republic of); Chaloosi, Marzieh [Department of Chemistry, University of Tarbiat Moallem, Tehran (Iran, Islamic Republic of); Ziarani, Ghodsi Mohammadi [Department of Chemistry, University of Alzahra, Tehran (Iran, Islamic Republic of)

    2009-09-30

    This study introduces the design of an anodic stripping voltammetric (ASV) method for the silver ion determination at a carbon paste electrode (CPE), chemically modified with phenylthiourea-nanoporous silica gel (Tu-SBA-15-CPE). The electroanalytical pro includes two steps: preconcentration of metal ions at an electrode surface, followed by quantification of the accumulated species by differential pulse anodic stripping voltammetric methods. Factors affecting the performance of the anodic stripping were investigated, including the modifier quantity in the paste, the electrolyte concentrations, the solution pH and the accumulation potential or time. The most sensitive and reliable electrode contained 10% Tu-SBA-15 and 90% carbon paste. The accumulation potential and time were set at, -200 mV and 300 s, respectively, and the scan rate at 50 mV s{sup -1} in the scan range of -200 to 700 mV. The resulting electrode demonstrated a linear response over range of silver ion concentration of 8.0-80 pmol/L with detection limit (S/N = 3) of 5 pmol/L. The prepared electrodes were used for the silver determination in sea and tap water samples and very good recovery results were obtained. The accuracy was assessed through recovery experiments and independent analysis by graphite furnace atomic absorption spectrometry.

  19. The natural diatomite from caldiran-van (Turkey): electroanalytical application to antimigraine compound naratriptan at modified carbon paste electrode.

    Science.gov (United States)

    Calışkan, Necla; Sögüt, Eda; Saka, Cafer; Yardım, Yavuz; Sentürk, Zuhre

    2010-09-01

    This paper is the first report describing the characterization of local diatomite of Caldiran-Van region (Eastern Anatolia, Turkey). Special attention was paid to the ability of its electroanalytical performance at modified electrodes and to the potential application of diatomite-modified electrode. For this purpose, the determination of Naratriptan which is a novel oral triptan (5-hydroxytryptamine receptor agonist) in migraine treatment, by means of a carbon paste electrode modified with 10% (w/w) of diatomite was studied using cyclic and square-wave voltammetry. The experimental conditions that affect the electrode reaction process were studied in terms of pH of the supporting electrolyte, scan rate, accumulation variables, modifier composition and square-wave parameters. Using square-wave stripping mode, the drug yielded a well-defined voltammetric response in Britton-Robinson buffer, pH 4.0 at 0.84 V (vs. Ag/AgCl) (a pre-concentration step being carried out with an open circuit at 120 s). The process could be used to determine Naratriptan concentrations in the range 5x10(-7)-9x10(-7) M, with a detection limit of 1.25x10(-7) M (46.5 mug L(-1)). The applicability of the method to spiked human urine samples was illustrated.

  20. Microbial mineral illization of montmorillonite in low-permeability oil reservoirs for microbial enhanced oil recovery.

    Science.gov (United States)

    Cui, Kai; Sun, Shanshan; Xiao, Meng; Liu, Tongjing; Xu, Quanshu; Dong, Honghong; Wang, Di; Gong, Yejing; Sha, Te; Hou, Jirui; Zhang, Zhongzhi; Fu, Pengcheng

    2018-05-11

    Microbial mineral illization has been investigated for its role in the extraction and recovery of metals from ores. Here we report our application of mineral bioillization for the microbial enhanced oil recovery in low-permeability oil reservoirs. It aimed to reveal the etching mechanism of the four Fe (III)-reducing microbial strains under anaerobic growth conditions on the Ca-montmorillonite. The mineralogical characterization of the Ca-montmorillonite was performed by Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy and energy dispersive spectrometer. Results showed that the microbial strains could efficiently reduce Fe (III) at an optimal rate of 71 %, and alter the crystal lattice structure of the lamella to promote the interlayer cation exchange, and to efficiently inhibit the Ca-montmorillonite swelling at an inhibitory rate of 48.9 %. Importance Microbial mineral illization is ubiquitous in the natural environment. Microbes in low-permeability reservoirs are able to enable the alteration of the structure and phase of the Fe-poor minerals by reducing Fe (III) and inhibiting clay swelling which is still poorly studied. This study aimed to reveal the interaction mechanism between Fe (III)-reducing bacterial strains and Ca-montmorillonite under anaerobic atmosphere, and to investigate the extent and rates of Fe (III) reduction and phase changes with their activities. Application of Fe (III)-reducing bacteria will provide a new way to inhibit clay swelling, to elevate reservoir permeability, and to reduce pore throat resistance after water flooding for enhanced oil recovery in low-permeability reservoirs. Copyright © 2018 American Society for Microbiology.

  1. Bismuth Modified Carbon-Based Electrodes for the Determination of Selected Neonicotinoid Insecticides

    Directory of Open Access Journals (Sweden)

    Marko Rodić

    2011-05-01

    Full Text Available Two types of bismuth modified electrodes, a bismuth-film modified glassy carbon (BiF-GCE and a bismuth bulk modified carbon paste, were applied for the determination of selected nitroguanidine neonicotinoid insecticides. The method based on an ex situ prepared BiF-GCE operated in the differential pulse voltammetric (DPV mode was applied to determine clothianidin in the concentration range from 2.5 to 23 μg cm−3 with a relative standard deviation (RSD not exceeding 1.5%. The tricresyl phosphate-based carbon paste electrodes (TCP-CPEs, bulk modified with 5 and 20 w/w% of bismuth, showed a different analytical performance in the determination of imidacloprid, regarding the peak shape, potential window, and noise level. The TCP-CPE with 5% Bi was advantageous, and the developed DPV method based on it allowed the determination in the concentration range from 1.7 to 60 μg cm−3 with an RSD of 2.4%. To get a deeper insight into the morphology of the bismuth-based sensor surfaces, scanning electron microscopic measurements were performed of both the surface film and the bulk modified electrodes.

  2. Synthesis and utilization of poly (methylmethacrylate nanocomposites based on modified montmorillonite

    Directory of Open Access Journals (Sweden)

    Ahmed M. Youssef

    2017-07-01

    Full Text Available Poly (methylmethacrylate nanocomposite was prepared via in-situ emulsion polymerization (PMMA/Mt-CTA. The modified montmorillonite (Mt-CTA is used as hosts for the preparation of poly (methylmethacrylate nanocomposites with basal distance 1.95 nm. Moreover, exfoliated nanocomposite was characterized by X-ray diffraction (XRD, transmission electron microscope (TEM, thermal gravimetric analysis (TGA, and differential scanning calorimetry (DSC. The fashioned nanocomposites exhibited better thermal stability than pristine PMMA which make it suitable for packaging applications. Furthermore, this nanocomposite reveals tremendous affinity for removing pesticides from aquatic solutions. The data obtained from GC/ECD gas liquid chromatography illustrated that the removal efficiency of PMMA/Mt-CTA nanocomposites for organochlorine pesticides (OCPs varied from 73.65% to 99.36% that make it as a new method for water treatment. Also, the antimicrobial activity of the Mt-CTA and PMMA/Mt-CTA nanocomposites was evaluated by the inhibitory zone tests and revealed good activity against Escherichia coli and Staphylococcus aureus, which makes it suitable materials for packaging applications.

  3. Application of simplified desorption method to sorption study. (2) Sorption of neptunium (V) on montmorillonite-based mixtures

    International Nuclear Information System (INIS)

    Kozai, Naofumi; Ohnuki, Toshihiko

    2013-01-01

    To elucidate the sorption behaviors of radionuclides in multi-mineral systems and the mutual effects of minerals on the sorption, this paper carried out the sorption and desorption experiments of neptunium(V) on montmorillonite-based two-mineral mixtures. The Np sorbed on montmorillonite at pH from 4 to 8 was desorbed with 1M KCl solutions, indicating that the sorption was cation exchange. The Np sorbed on apatite and calcite was nondesorbable with 1M KCl solutions, which is in harmony with the knowledge that Np forms strong complexes with the phosphate groups of apatite and the carbonate groups of calcite. This study utilized these clear distinguishes of the desorption behaviors for examining the two-mineral systems. In montmorillonite-apatite mixtures, the sorption on the montmorillonite was decreased and Np was accumulated on the apatite. In montmorillonite-calcite mixtures, the sorption on the montmorillonite was decreased due to the interference by the calcium and carbonate ions dissolved from calcite while no accumulation of Np to calcite was observed. (author)

  4. Mechano-Physical Properties and Microstructure of Carbon Nanotube Reinforced Cement Paste after Thermal Load.

    Science.gov (United States)

    Szeląg, Maciej

    2017-09-11

    The article presents the results obtained in the course of a study on the use of carbon nanotubes (CNTs) for the modification of a cement matrix. Carbon nanotubes were introduced into a cement paste in the form of an aqueous dispersion in the presence of a surfactant (SDS-sodium dodecyl sulfate), which was sonicated. The selected physical and mechanical parameters were examined, and the correlations between these parameters were determined. An analysis of the local microstructure of the modified cement pastes has been carried out using scanning electron microscope (SEM) and X-ray microanalysis (EDS). In addition, the effect of carbon nanotubes on the change in characteristics of the cementitious material exposed to the sudden, short-term thermal load, was determined. The obtained material was characterized by a much lower density than a traditional cement matrix because the phenomenon of foaming occurred. The material was also characterized by reduced durability, higher shrinkage, and higher resistance to the effect of elevated temperature. Further research on the carbon nanotube reinforced cement paste, with SDS, may contribute to the development of a modified cement binder for the production of a lightweight or an aerated concrete.

  5. Mechano-Physical Properties and Microstructure of Carbon Nanotube Reinforced Cement Paste after Thermal Load

    Science.gov (United States)

    2017-01-01

    The article presents the results obtained in the course of a study on the use of carbon nanotubes (CNTs) for the modification of a cement matrix. Carbon nanotubes were introduced into a cement paste in the form of an aqueous dispersion in the presence of a surfactant (SDS—sodium dodecyl sulfate), which was sonicated. The selected physical and mechanical parameters were examined, and the correlations between these parameters were determined. An analysis of the local microstructure of the modified cement pastes has been carried out using scanning electron microscope (SEM) and X-ray microanalysis (EDS). In addition, the effect of carbon nanotubes on the change in characteristics of the cementitious material exposed to the sudden, short-term thermal load, was determined. The obtained material was characterized by a much lower density than a traditional cement matrix because the phenomenon of foaming occurred. The material was also characterized by reduced durability, higher shrinkage, and higher resistance to the effect of elevated temperature. Further research on the carbon nanotube reinforced cement paste, with SDS, may contribute to the development of a modified cement binder for the production of a lightweight or an aerated concrete. PMID:28891976

  6. Effects of Montmorillonite on the Mineralization and Cementing Properties of Microbiologically Induced Calcium Carbonate

    Directory of Open Access Journals (Sweden)

    Tao Chen

    2017-01-01

    Full Text Available Carbonate mineralization microbe is a microorganism capable of decomposing the substrate in the metabolic process to produce the carbonate, which then forms calcium carbonate with calcium ions. By taking advantage of this process, contaminative uranium tailings can transform to solid cement, where calcium carbonate plays the role of a binder. In this paper, we have studied the morphology of mineralized crystals by controlling the mineralization time and adding different concentrations of montmorillonite (MMT. At the same time, we also studied the effect of carbonate mineralized cementation uranium tailings by controlling the amount of MMT. The results showed that MMT can regulate the crystal morphology of calcium carbonate. What is more, MMT can balance the acidity and ions in the uranium tailings; it also can reduce the toxicity of uranium ions on microorganisms. In addition, MMT filling in the gap between the uranium tailings made the cement body more stable. When the amount of MMT is 6%, the maximum strength of the cement body reached 2.18 MPa, which increased by 47.66% compared with that the sample without MMT. Therefore, it is reasonable and feasible to use the MMT to regulate the biocalcium carbonate cemented uranium tailings.

  7. A simple and efficient electrochemical sensor for folic acid determination in human blood plasma based on gold nanoparticles–modified carbon paste electrode

    International Nuclear Information System (INIS)

    Arvand, Majid; Dehsaraei, Mohammad

    2013-01-01

    Folic acid (FA) is a water soluble vitamin that exists in many natural species. The lack of FA causes some deficiencies in human body, so finding a simple and sensitive method for determining the FA is important. A new chemically modified electrode was fabricated for determination of FA in human blood plasma using gold nanoparticles (AuNPs) and carbon paste electrode (CPE). Gold nanoparticles–modified carbon paste electrode (AuNPs/CPE) was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The experimental parameters such as pH, scan rate (ν) and amount of modifier were studied by cyclic voltammetry and the optimized values were chosen. The electrochemical parameters such as diffusion coefficient of FA (D FA ), electrode surface area (A) and electron transfer coefficient (α) were calculated. Square wave voltammetry as an accurate technique was used for quantitative calculations. A good linear relation was observed between anodic peak current (i pa ) and FA concentration (C FA ) in the range of 6 × 10 −8 to 8 × 10 −5 mol L −1 , and the detection limit (LOD) achieved 2.7 × 10 −8 mol L −1 , that is comparable with recently studies. This paper demonstrated a novel, simple, selective and rapid sensor for determining the FA in the biological samples. - Highlights: • We examine a AuNPs/CPE for direct electrooxidation behavior and determination of FA. • Characterization of the electrode showed an obvious increase in surface area and porosity after modification. • The modified electrode showed good ability to distinguish the electrochemical response of FA. • The results were attributed to the specific characteristics of AuNPs present in the AuNPs/CPE. • This paper demonstrated a simple and rapid sensor for determination of FA in plasma

  8. Electrochemically pretreated zeolite-modified carbon-paste electrodes for determination of linuron in an agricultural formulation and water

    International Nuclear Information System (INIS)

    Siara, L.R.; Lima, F. de; Cardoso, C.A.L.; Arruda, G.J.

    2015-01-01

    Highlights: • Cyclic voltammetry, square-wave voltammetry, electrochemical impedance spectroscopic, and scanning electron microscopy were employed. • Kinetic parameters (n, α, k s , and Γ) were calculated. • High sensitivity was observed in the linear concentration range. • Excellent recovery rates were achieved for tap water samples. • The method proved applicable to the determination of linuron in the presence of potential organic and inorganic interferents, none of which affected the results. - Abstract: A simple and inexpensive, yet highly sensitive electrochemical method for quantifying linuron in tap and distilled water and in agricultural formulations was developed using electrochemically pretreated zeolite-modified carbon-paste electrodes (ZMCPEs). Compared with untreated ZMCPEs, the electrochemically pretreated electrodes showed significantly enhanced peak currents for linuron oxidation. Scanning electron microscopy and energy-dispersive x-ray spectroscopy were used to examine the structure of the zeolite-modified and unmodified carbon-paste electrodes (CPEs). ZMCPEs were electrochemically characterized using cyclic voltammetry, chronocoulometry, square-wave voltammetry, and electrochemical impedance spectroscopy. A mechanism for linuron oxidation on ZMCPE surfaces was proposed. The electrochemical variables taken into account were electrode area, number of transferred electrons, electron transfer coefficient, electrode reaction standard rate constant, surface coverage, and capacitance of the electric double layer. Zeolite was found to have a strong influence on these variables. The electrochemical procedure applied to linuron was developed using electrochemically pretreated ZMCPEs under optimal conditions. Linuron oxidation currents exhibited linear concentration in the 87.36 to 625.72 nmol L −1 range, with a limit of detection of 22.57 nmol L −1 . The proposed electrochemical method was employed to quantify linuron in tap and distilled

  9. A study of the fixing of phosphoric ions by zirconium-montmorillonite; Etude de la fixation d'ions phosphoriques par la montmorillonite-zirconium

    Energy Technology Data Exchange (ETDEWEB)

    Bittel, R; Boursat, C; Platzer, R [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1960-07-01

    In connection with the research carried out on the purification of nuclear reactor water, we have undertaken a study of the ion-exchange properties of acid montmorillonite. In a previous paper, we described the preparation of zirconium-montmorillonite small plate. The present article aims to study some of the properties of the clay obtained. We have observed that zirconium-montmorillonite fixes very strongly the phosphorus from solutions of phosphoric acid or of phosphates: on 1 g of clay it is possible to fix 1,2 milli-atoms-gram of zirconium and the zirconium montmorillonite itself fixes 2,1 milli-atoms-gram of phosphorus. An explanation of these experimental results, which is as much chemical as mineralogical, is the hypothesis that the fixing of phosphoric ions modifies the distribution of the ions between the platelets and precipitates a very slightly soluble product of the type diphospho-zirconic acid. (author) [French] En rapport avec des recherches sur I'epuration de l'eau des reacteurs nucleaires nous avons entrepris une etude sur les proprietes d'echangeur d'ions de la montmorillonite-acide. Dans une precedente publication, nous avons decrit la preparation des plaquettes de montmorillonite-zirconium. La presente communication a pour but d'etudier quelques proprietes de l'argile obtenue. Nous avons constate que la montmorilionite-zirconium fixe le phosphore de solutions d'acide phosphorique ou de phosphate avec une grande intensite: sur 1 g d'argile, on peut fixer 1,2 atomes-gramme de zirconium, et la montmorillonite-zirconium fixe a son tour 2,1 milli-atomesgramme de phosphore. Une explication des resultats experimentaux, tant d'ordre chimique que d'ordre mineralogique, consiste en l'hypothese suivant laquelle la fixation d'ions phosphoriques modifierait la repartition des ions entre les feuillets avec precipitation du compose tres peu soluble (type: acide diphosphozirconique). (auteur)

  10. Glucose biosensor based on immobilization of glucose oxidase on a carbon paste electrode modified with microsphere-attached l-glycine.

    Science.gov (United States)

    Donmez, Soner; Arslan, Fatma; Sarı, Nurşen; Hasanoğlu Özkan, Elvan; Arslan, Halit

    2017-09-01

    In the present study, a novel biosensor that is sensitive to glucose was prepared using the microspheres modified with (4-formyl-3-methoxyphenoxymethyl)polystyrene (FMPS) with l-glycine. Polymeric microspheres having Schiff bases were prepared from FMPS using the glycine condensation method. Glucose oxidase enzyme was immobilized onto modified carbon paste electrode by cross-linking with glutaraldehyde. Oxidation of enzymatically produced H 2 O 2 (+0.5 V vs. Ag/AgCl) was used for determination of glucose. Optimal temperature and pH were found as 50 °C and 8.0, respectively. The glucose biosensor showed a linear working range from 5.0 × 10 -4 to 1.0 × 10 -2 M, R 2 = 0.999. Storage and operational stability of the biosensor were also investigated. The biosensor gave perfect reproducible results after 20 measurements with 3.3% relative standard deviation. It also had good storage stability. © 2016 International Union of Biochemistry and Molecular Biology, Inc.

  11. Polyaniline/MWCNTs/starch modified carbon paste electrode for non-enzymatic detection of cholesterol: application to real sample (cow milk).

    Science.gov (United States)

    Gautam, Vineeta; Singh, Karan P; Yadav, Vijay L

    2018-03-01

    Nanocomposite materials are potentially revolutionizing many technologies, including sensors. In this paper, we described the application of "PANI/MWCNTs/Starch" modified carbon paste electrode (PCS-CPE) as a simple and highly sensitive cholesterol sensor. This novel nano-composite material has integrated nano-morphology, where polyaniline could interact effectively with the additives; pi-pi stacking "MWCNTs," and covalently bonded with starch. Specific binding sites (sugar chains), better electro-catalytic properties and fast electron transfer facilitated the oxidation of cholesterol. Fourier transform infrared spectra confirmed the interaction of cholesterol with the composite material. The sensing response of PCS was measured by cyclic voltammetry and chronoamperometry (0.1 M PBS-5 used as supporting electrolyte). As the amount of cholesterol increased in the test solution, cyclic voltammograms showed a rise of peak current (cathodic and anodic). Under the normal experimental conditions, the developed sensor exhibited wide linear dynamic range (0.032 to 5 mM) (upper limit is due to lack of solubility of cholesterol), high sensitivity (800 μAmM -1  cm -2 ), low detection limit (0.01 mM) and shorter response time (within 4-6 s). Analytical specificity, selectivity, and sensitivity during cholesterol estimation were compared with the response of some other analytes (ascorbic acid, glucose, l-dopa, urea and lactic acid). This novel sensor was successfully applied to estimate cholesterol in cow milk (used as a model real sample). The sensing platform is highly sensitive and shows a linear response towards cholesterol without using any additional redox mediator or enzyme, thus this material is extremely promising for the realization of a low-cost integrated cholesterol sensor device. Graphical abstract Cyclic voltammetric response of cholesterol of composite modified carbon paste capillary electrode.

  12. The adsorption of Cs+ from wastewater using lithium-modified montmorillonite caged in calcium alginate beads.

    Science.gov (United States)

    Xia, Meng; Zheng, Xianming; Du, Mingyang; Wang, Yingying; Ding, Aizhong; Dou, Junfeng

    2018-07-01

    The increasing nuclear energy consumption has posed serious environmental concerns (e.g. nuclear leakage), and the removal of radionuclides such as cesium becomes an urgent issue to be solved currently. In this research, a novel non-toxic adsorbent lithium-modified montmorillonite clay encapsulated in calcium alginate microbeads (MCA/Li) was fabricated by using ion-exchange method and then used successfully in the remediation of cesium-contaminated wastewater. Analyses of scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to characterize the physicochemical properties of adsorbent MCA/Li, such as internal crystal structure, constituent elements, and functional groups. The effects of concentration ratios (sodium alginate/montmorillonite), solution pH, contacting time and initial Cs + concentration on the adsorption behavior were carefully investigated via batch adsorption experiments. The adsorbent MCA/Li exhibited higher selectivity and removal efficiency towards Cs + with the maximum adsorption capacity of 100.25 mg/g. In the kinetics study, the pseudo-first-order fitted the cesium adsorption data of MCA/Li better than the pseudo-second-order. The adsorption mechanism studies revealed the process followed the Langmuir isotherm model, which suggested that Cs + adsorption onto MCA/Li is a monolayer homogeneous adsorption process. The research findings indicated this novel adsorbent MCA/Li demonstrated great potential in radioactive wastewater treatment due to its convenience in synthesis, high adsorption capacity, and low cost. Copyright © 2018 Elsevier Ltd. All rights reserved.

  13. In situ characterization of organo-modified and unmodified montmorillonite aqueous suspensions by UV-visible spectroscopy.

    Science.gov (United States)

    Alin, Jonas; Rubino, Maria; Auras, Rafael

    2015-10-15

    UV-visible (UV-Vis) spectroscopy (Tyndall spectra) was applied and tested for its ability to measure organo-modified and unmodified montmorillonite (MMT) clays in aqueous suspensions. A full factorial design of experiments was used to study the influence of pH, NaCl and clay concentrations on the average particle size of the clay agglomerates. The methodology was evaluated by observing results that were consistent with previous research about the unmodified clay's behavior in aqueous suspensions. The results from this evaluation corresponded to accepted theories about the unmodified clay's behavior, indicating that the methodology is precise enough to distinguish the effects of the studied factors on these clay suspensions. The effect of clay concentration was related to the amount of ions per clay particle for the unmodified clay, but was not significant for the organo-modified MMT. The average particle size of the organo-modified MMT in suspension was significantly larger than that of the unmodified clay. Size of the organo-modified MMT agglomerates in suspension decreased in the presence of NaCl and at both high and low pH; this behavior was opposite to that of the unmodified clay. These results demonstrate that the UV-Vis methodology is well-suited for characterizing clay particle size in aqueous suspensions. The technique also is simple, rapid, and low-cost. Copyright © 2015 Elsevier Inc. All rights reserved.

  14. Hybrids of ethylene vinyl acetate with Na-montmorillonite and titania: preparation and characterization

    International Nuclear Information System (INIS)

    Ashfaq, M.

    2010-01-01

    Hybrids of Ethylene vinyl acetate (EVA) with Na-montmorillonite and titania were formed. Montmorillonite was organically modified by two different modifiers: Pyridinium ions and 4. 4-oxydianilinium ions. X-ray diffraction results revealed that Pyridinium ions increased the .interlayer spacing by 0.33 nm and 4, 4-oxydianilinium by 0.55 nm approximately. These modified organo-clays were successfully exfoliated in EVA using melt blending. These hybrids showed improvement in mechanical and thermal properties. 4, 4-oxydianilinium ions were degraded at higher temperature due to which thermal degradation was enhanced in EVA. In addition to this, EVA/titania hybrids were also prepared using sot-gel technique and modified by triethoxy vinyl silane and (3-aminopropyI)- triethoxy silane to increase their compatibility with EVA. Some portion of unmodified titania was heat treated to 600 degree C to obtain particulate titania. The hybrid of particulate titania and modified titania improved the mechanical properties and thermal properties. Especially in case of modified titania toughness was almost doubled. (author)

  15. Simulation of salinity effects on past, present, and future soil organic carbon stocks.

    Science.gov (United States)

    Setia, Raj; Smith, Pete; Marschner, Petra; Gottschalk, Pia; Baldock, Jeff; Verma, Vipan; Setia, Deepika; Smith, Jo

    2012-02-07

    Soil organic carbon (SOC) models are used to predict changes in SOC stocks and carbon dioxide (CO(2)) emissions from soils, and have been successfully validated for non-saline soils. However, SOC models have not been developed to simulate SOC turnover in saline soils. Due to the large extent of salt-affected areas in the world, it is important to correctly predict SOC dynamics in salt-affected soils. To close this knowledge gap, we modified the Rothamsted Carbon Model (RothC) to simulate SOC turnover in salt-affected soils, using data from non-salt-affected and salt-affected soils in two agricultural regions in India (120 soils) and in Australia (160 soils). Recently we developed a decomposition rate modifier based on an incubation study of a subset of these soils. In the present study, we introduce a new method to estimate the past losses of SOC due to salinity and show how salinity affects future SOC stocks on a regional scale. Because salinity decreases decomposition rates, simulations using the decomposition rate modifier for salinity suggest an accumulation of SOC. However, if the plant inputs are also adjusted to reflect reduced plant growth under saline conditions, the simulations show a significant loss of soil carbon in the past due to salinization, with a higher average loss of SOC in Australian soils (55 t C ha(-1)) than in Indian soils (31 t C ha(-1)). There was a significant negative correlation (p < 0.05) between SOC loss and osmotic potential. Simulations of future SOC stocks with the decomposition rate modifier and the plant input modifier indicate a greater decrease in SOC in saline than in non-saline soils under future climate. The simulations of past losses of SOC due to salinity were repeated using either measured charcoal-C or the inert organic matter predicted by the Falloon et al. equation to determine how much deviation from the Falloon et al. equation affects the amount of plant inputs generated by the model for the soils used in this study

  16. Carbon nanotubes paste sensor modified with bismuth film for determination of metallic ions in ethanol fuel

    Directory of Open Access Journals (Sweden)

    Felipe Augusto Gorla

    2015-05-01

    Full Text Available In the present study an anodic stripping voltammetric method using a bismuth film modified carbon nanotubes paste electrode for simultaneous determination of metals Zn2+, Cd2+and Pb2+in ethanol fuel is described. The metallic ions were preconcentrated on the bismuth film in the time and deposition potential of 500 s and -1.2 V and the stripping step was carried out by square wave voltammetry (frequency of 15 Hz, pulse amplitude of 25 mV and potential step of 5 mV. Acetate buffer at 0.1 mol L-1concentration and pH 4.5 was used as support electrolyte. The method showed linearity including the analytical blank up to 48.39 ?g L-1 for the metals and the obtained limits of detection were 3.36, 0.32 and 0.47 ?g L-1for Zn2+, Cd2+and Pb2+, respectively. The proposed method was applied in ethanol fuel samples.

  17. Carbonate reservoirs modified by magmatic intrusions in the Bachu area, Tarim Basin, NW China

    Directory of Open Access Journals (Sweden)

    Kang Xu

    2015-09-01

    Full Text Available Oil and gas exploration in carbonate rocks was extremely successful in recent years in the Ordovician in Tarim Basin, NW China. Here, we investigate the carbonate reservoirs in the Bachu area of the Tarim Basin through petrological and geochemical studies combined with oil and gas exploration data. Geochemical analysis included the major, trace, and rare earth elements; fluid inclusion thermometry; clay mineral characterization; and carbon and oxygen isotopes of the carbonate rocks. Homogenization temperatures of the fluid inclusions of Well He-3 in the Bachu area indicate three groups, 60–80 °C, 90–130 °C, and 140–170 °C, and suggest that the carbonate rocks experienced modification due to heating events. The porosity in the reservoir is defined by fractures and secondary pores, and there is a notable increase in the porosity of the carbonate reservoirs in proximity to magmatic intrusion, particularly approximately 8–10 m from the intrusive rocks. The development of secondary pores was controlled by lithofacies and corrosion by various fluids. We identify supercritical fluids with high density (138.12–143.97 mg/cm3 in the Bachu area. The negative correlations of δ13C (−2.76‰ to −0.97‰ and δ18O (−7.91‰ to −5.07‰ suggest that the carbonate rocks in the study area were modified by high-salinity hydrothermal fluid. The formation of clay minerals, such as illite and montmorillonite, caused a decrease in porosity. Our study demonstrates the effect of magmatic intrusions in modifying the reservoir characteristics of carbonate rocks and has important implications for oil and gas exploration.

  18. Antimicrobial hyperbranched poly(ester amide)/polyaniline nanofiber modified montmorillonite nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Pramanik, Sujata [Advanced Polymer and Nanomaterial Laboratory, Department of Chemical Sciences, Tezpur University, Tezpur 784028 (India); Bharali, Pranjal; Konwar, B.K. [Department of Molecular Biology and Biotechnology, Tezpur University, Tezpur 784028 (India); Karak, Niranjan, E-mail: karakniranjan@yahoo.com [Advanced Polymer and Nanomaterial Laboratory, Department of Chemical Sciences, Tezpur University, Tezpur 784028 (India)

    2014-02-01

    There has been growing interest in the use of nanomaterials featuring potent of antimicrobial activity in the biomedical domain. It still remains a challenge for the researchers to develop an efficient nanocomposite possessing antimicrobial efficacy against broad spectrum microbes including bacteria, fungi as well as algal consortium, posing serious challenges for the human survival. In addressing the above problem, we report the fabrication of bio-based hyperbranched poly(ester amide) (HBPEA)/polyaniline nanofiber modified montmorillonite (MMT) nanocomposites by an ex-situ polymerization technique at varied weight percentages (1, 2.5, 5 wt.%) of the modified MMT (nanohybrid). The Fourier transform infrared spectroscopy confirmed the structural changes upon interaction of the nanohybrid with HBPEA. A probable mechanism is proposed for the formation of nanocomposites with partially exfoliated nanoplatelet structure, which was further confirmed from the high resolution transmission electron microscopic analyses. The prepared nanocomposites exhibited potent efficacy against gram positive bacteria like Bacillus subtilis and Staphylococcus aureus as compared to the gram negative ones like Pseudomonas aeruginosa and Escherichia coli. The nanocomposites showed significant antifungal activity against Aspergillus niger, Fusarium oxysporum and Coleotricum capcii and antialgal activity against algal consortium comprising of Chlorella, Hormidium and Cladophorella species. The formation of thermosetting nanocomposites resulted in the acceptable improvement of desired physico-chemical and mechanical properties including thermostability. Thus pronounced antimicrobial activity of the nanocomposites against a spectrum of bacterial and fungal strains as well as a consortium of algal species along with other desired performance vouched them as potent antimicrobial materials in the realm of health and biomedical industry. - Highlights: • A possible approach for fabrication of the

  19. Antimicrobial hyperbranched poly(ester amide)/polyaniline nanofiber modified montmorillonite nanocomposites

    International Nuclear Information System (INIS)

    Pramanik, Sujata; Bharali, Pranjal; Konwar, B.K.; Karak, Niranjan

    2014-01-01

    There has been growing interest in the use of nanomaterials featuring potent of antimicrobial activity in the biomedical domain. It still remains a challenge for the researchers to develop an efficient nanocomposite possessing antimicrobial efficacy against broad spectrum microbes including bacteria, fungi as well as algal consortium, posing serious challenges for the human survival. In addressing the above problem, we report the fabrication of bio-based hyperbranched poly(ester amide) (HBPEA)/polyaniline nanofiber modified montmorillonite (MMT) nanocomposites by an ex-situ polymerization technique at varied weight percentages (1, 2.5, 5 wt.%) of the modified MMT (nanohybrid). The Fourier transform infrared spectroscopy confirmed the structural changes upon interaction of the nanohybrid with HBPEA. A probable mechanism is proposed for the formation of nanocomposites with partially exfoliated nanoplatelet structure, which was further confirmed from the high resolution transmission electron microscopic analyses. The prepared nanocomposites exhibited potent efficacy against gram positive bacteria like Bacillus subtilis and Staphylococcus aureus as compared to the gram negative ones like Pseudomonas aeruginosa and Escherichia coli. The nanocomposites showed significant antifungal activity against Aspergillus niger, Fusarium oxysporum and Coleotricum capcii and antialgal activity against algal consortium comprising of Chlorella, Hormidium and Cladophorella species. The formation of thermosetting nanocomposites resulted in the acceptable improvement of desired physico-chemical and mechanical properties including thermostability. Thus pronounced antimicrobial activity of the nanocomposites against a spectrum of bacterial and fungal strains as well as a consortium of algal species along with other desired performance vouched them as potent antimicrobial materials in the realm of health and biomedical industry. - Highlights: • A possible approach for fabrication of the

  20. Synthesis of Pd and Rh metal nanoparticles in the interlayer space of organically modified montmorillonite

    International Nuclear Information System (INIS)

    Patel, Hasmukh A.; Bajaj, Hari C.; Jasra, Raksh Vir

    2008-01-01

    This study reports the synthesis of palladium and rhodium metal nanoparticles supported on montmorillonite (MMT) and partially organically modified MMT (POMM) using tetraamine palladium and hexaamine rhodium complex as precursor for palladium and rhodium respectively. The synthesized nanoparticles were characterized by powder X-ray diffraction PXRD and TEM. The PXRD study shows characteristic crystallographic planes for Pd and Rh metal and confirm the formation of metal nanoparticles in MMT and POMM. The TEM images reveal the effect of organic modification of MMT on decreasing particle size of Pd and Rh metal. The Pd and Rh metal nanoparticles are agglomerated in pristine MMT while nanoparticles are well dispersed in POMM. ICP-AES analysis was carried out to estimate quantitative amount of Pd and Rh metal in MMT and POMM

  1. Cadmium Adsorption on HDTMA Modified Montmorillionite

    Directory of Open Access Journals (Sweden)

    Mohd. Elmuntasir I. Ahmed

    2009-06-01

    Full Text Available In this paper the possibility of cadmium removal from aqueous solutions by adsorption onto modified montmorillonite clay is investigated. Batch adsorption experiments performed revealed an enhanced removal of cadmium using HDTMA modified montmorillonite to 100% of its exchange capacity. Modified montmorillonite adsorption capacity increases at higher pHs suggesting adsorption occurs as a result of surface precipitation and HDTMA complex formation due to the fact that the original negatively charged montmorillonite is now covered by a cationic layer of HDTMA. Adsorption isotherms generated followed a Langmuir isotherm equation possibly indicating a monolayer coverage. Adsorption capacities of up to 49 mg/g and removals greater than 90% were achieved. Anionic selectivity of the HDTMA modified monmorillonite is particularly advantageous in water treatment applications where high concentrations of less adsorbable species are present, and the lack of organoclay affinity for these species may allow the available capacity to be utilized selectively by the targeted species.

  2. Effect of type and content of modified montmorillonite on the structure and properties of bio-nanocomposite films based on soy protein isolate and montmorillonite.

    Science.gov (United States)

    Kumar, P; Sandeep, K P; Alavi, S; Truong, V D; Gorga, R E

    2010-06-01

    The nonbiodegradable and nonrenewable nature of plastic packaging has led to a renewed interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanoparticles such as layered silicates). Bio-nanocomposite films based on soy protein isolate (SPI) and modified montmorillonite (MMT) were prepared using melt extrusion. The effect of different type (Cloisite 20A and Cloisite 30B) and content (0% to 15%) of modified MMT on the structure (degree of intercalation and exfoliation) and properties (color, mechanical, dynamic mechanical, thermal stability, and water vapor permeability) of SPI-MMT bio-nanocomposite films were investigated. Extrusion of SPI and modified MMTs resulted in bio-nanocomposites with exfoliated structures at lower MMT content (5%). At higher MMT content (15%), the structure of bio-nanocomposites ranged from intercalated for Cloisite 20A to disordered intercalated for Cloisite 30B. At an MMT content of 5%, bio-nanocomposite films based on modified MMTs (Cloisite 20A and Cloisite 30B) had better mechanical (tensile strength and percent elongation at break), dynamic mechanical (glass transition temperature and storage modulus), and water barrier properties as compared to those based on natural MMT (Cloisite Na(+)). Bio-nanocomposite films based on 10% Cloisite 30B had mechanical properties comparable to those of some of the plastics that are currently used in food packaging applications. However, much higher WVP values of these films as compared to those of existing plastics might limit the application of these films to packaging of high moisture foods such as fresh fruits and vegetables.

  3. Calcium Ion Removal by KMnO4 Modified Pineapple Leaf Waste Carbon Prepared from Waste of Pineapple Leaf Fiber Production Processing

    Directory of Open Access Journals (Sweden)

    Sumrit Mopoung

    2016-12-01

    Full Text Available Pineapple leaf fiber waste carbon, modified with 3% KMnO4, was used for Ca2+ removal from aqueous solution. The effects of contact time, loading, water hardness, and isotherms on Ca2+ adsorption were studied. The results show that the Ca2+ ion removal by pineapple leaf fiber waste carbon could be improved by modification with KMnO4. The adsorption would reach equilibrium state at about 60 min for a water source with hardness values of 40-200 mg/dm3. Increases in total hardness (40 to 200 mg/dm3 lead to a decrease in Ca2+ ion removal efficiency (90.05% to 37.65% and an increase in Ca2+ ion adsorption capacity at equilibrium (4.37 mg/g to 8.95 mg/g. The Ca2+ removal efficiencies increase with increasing loading of modified waste carbon. The equilibrium data were fitted well by both the Langmuir isotherm and the Freundlich isotherm. For the Langmuir isotherm model, the values of the maximum Ca2+ adsorption capacity and Langmuir constant being 2.81 mg/g and 0.9262 dm3 /g, respectively. On the other hand for the Freundlich isotherm model, the KF and n values are 1.374 dm3 (1/n mg (1-1/n/g and 4.671, respectively. These results indicate that modified pineapple fiber waste carbon is a material with high Ca2+ ion adsorption capacity, heterogeneity, and high affinity.

  4. Moisture Absorption Behaviour of Biopolymer Polycapralactone (PCL) / Organo Modified Montmorillonite Clay (OMMT) biocomposite films

    Science.gov (United States)

    Malik, Neetu; Shrivastava, Sharad; Bandhu Ghosh, Subrata

    2018-04-01

    Bio composite materials were fabricated using mixing biodegradable polymer polycaptalactone (PCL) and Organo Modified Montmorillonite Clay (OMMT) through solution casting. Various samples of bio composite films were prepared by varying the OMMT wt% composition by 0.1%, 0.5%, 1% and 1.5%. Thereafter, the density and water absorption of the composites were investigated with respect to immersion time in water. The moisture absorption results show that with an increase in weight percentage (from 0.1 to wt 1.5%) of OMMT within the bio polymer films, the absorption value of bio-nanocomposite films reduced rapidly from 34.4% to 22.3%. The density of hybrid composites also increased with increase in weight percentage of OMMT. The swelling characteristic of PCL increased with increasing % of OMMT clay. These results indicate that the optimized composition of constituents in composite membrane could effectively reduce the anhydrous conditions of bio-composite film.

  5. Electrochemical determination of paraquat in citric fruit based on electrodeposition of silver particles onto carbon paste electrode

    OpenAIRE

    Abdelfettah Farahi; Mounia Achak; Laila El Gaini; Moulay Abderrahim El Mhammedi; Mina Bakasse

    2015-01-01

    Carbon paste electrodes (CPEs) modified with silver particles present an interesting tool in the determination of paraquat (PQ) using square wave voltammetry. Metallic silver particle deposits have been obtained via electrochemical deposition in acidic media using cyclic voltammetry. Scanning electron microscopy and X-ray diffraction measurements show that the silver particles are deposited onto carbon surfaces in aggregate form. The response of PQ with modified electrode (Ag-CPE) related to ...

  6. Metallophthalocyanine based carbon paste electrodes for the determination of 2’,3’-Dideoxyinosine

    CSIR Research Space (South Africa)

    Ozoemena, KI

    2009-07-01

    Full Text Available Novel electrochemical sensors based on carbon paste impregnated with metallopthalocyanine (MPc, M¼Co, Fe) complexes, have been constructed for the assay of anti-HIV drug 2’,3’-dideoxyinosine (didanosine, DDI). Both modified electrodes showed...

  7. Effects of Applying Lime and CalciumMontmorillonite on Nitrification Dynamics in Acidic Soil

    Directory of Open Access Journals (Sweden)

    WANG Mei

    2017-01-01

    Full Text Available Soil acidification is known as a natural and slow process along with clay mineral weathering. In recent years however, with inten sive soil utilization in agriculture, soil acidification has increased dramatically and nitrification of ammonium nitrogen fertilizer is one of the main contributors to soil acidification. Lime application is the traditional practice to improve acidic soils but it often makes the soil acidic a gain leading to soil compaction in most cases. Montmorillonite is the main clay mineral component of alkaline or neutral soils, more so it is known to undergo further weathering processes during soil acidification. The laboratory-based incubations were used in this study, and nitri fication was measured while kinetic curves were fitted to check the effects of decreasing soil acidity by lime(Ca-OHand montmorillonite (Ca-Mon nitrification of the acidic soil. The results showed that significant nitrification was observed both in Ca-OH and Ca-M treatments, and the nitrification process was fitted in the first-order kinetic model, NNO3=N0+Np(1-exp(-k1t(P-1·d-1was significantly higher than that of Ca-M treatment(2.381 mg·kg-1·d-1. The potential nitrifi cation rate(Vpwere 6.42, 8.58 mg N·kg-1·d-1 at pH 5.7 and 6.2 respectively, and the average nitrification rate(Vaof Ca-OH treatment were 2.71, 3.88 mg N·kg-1·d-1 respectively, which were significantly greater than those of Ca-M treatment(Vp were 3.40, 4.56 mg N·kg-1·d-1 and Va were 2.36, 3.04 mg N·kg-1·d-1 at pH 5.7 and 6.2 respectively. Therefore the net nitrification rate, potential nitrification rate(Vp and average nitrification rate(Vaof Ca-OH treatment were significantly higher than that of Ca-M treatment, suggesting that the possibili ty and degree of soil reacidification by using lime to improve acidic soil is greater than using calcium montmorillonite. This study will provide a new reference for the improvement of acid soils.

  8. Electrochemical Studies of Interactions Between Fe(II/Fe(III and Amino Acids Using Ferrocene-Modified Carbon Paste Electrode

    Directory of Open Access Journals (Sweden)

    Vatrál Jaroslav

    2014-12-01

    Full Text Available The electrochemical behavior of an Fe(II/Fe(III redox couple in the presence of various selected amino acids has been studied using ferrocene-modified carbon paste electrode at pH = 7.4. Because of Fe(II/Fe(III solubility issues at physiological pH, ferrocene was used as a source of iron. Anodic oxidation of iron (pH = 7.2 occurred at 0.356 V and cathodic oxidation at 0.231 V, both vs Ag|AgCl. Treatment of the voltammetric data showed that it was a purely diffusion-controlled reaction with the involvement of one electron. After addition of amino acids, potential shifts and current changes can be observed on the voltammograms. Cyclic voltammetry experiments revealed the capability of amino acids to change the electrochemical behavior of the Fe(II/Fe(III redox couple.

  9. Carbon paste electrode modified molecularly imprinted polymer as a sensor for creatinine analysis by stripping voltammetry

    Science.gov (United States)

    Khasanah, M.; Darmokoesoemo, H.; Rizki, D. A.

    2017-09-01

    Modification of carbon paste electrode with molecularly imprinted polymer (CP-MIP) as a voltammetric sensor for creatinine has been developed. MIP was synthesized by reacting melamine, chloranil and creatinine with a mole ratio of 1:1:0.1. Creatinine was extracted from polymer chain by using hot water to form a specific imprinted for creatinine molecule. Carbon paste-MIP electrode was prepared by mixing activated carbon, solid paraffin, and MIP in a 45:40:15(w/w %) ratio. The optimum conditions of creatinine analysis by differential pulse stripping voltammetry (DPSV) using the developed electrode were the accumulation potential -1000 mV during 90 s at pH 5. The precision of the method for 0.1-0.5 μlg/L creatinine was 88.7-96.3%, while the detection limit of this method was 0.0315 μlg/L. The accuracy compared by spectrophotometric method was 95.3-103.6%

  10. Carbon paste electrode in a solid-contact minicavity; Eletrodo de pasta de carbono em minicavidade de contato solido

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Antonio Ap. Pupim; Ribeiro, Sidney Jose Lima; Fugivara, Cecilio Sadao; Caiut, Jose Mauricio Almeida; Sargentelli, Vagner; Benedetti, Assis Vicente [UNESP - Universidade Estadual Paulista, Instituto de Quimica, Araraquara SP (Brazil)

    2011-07-01

    This work describes the preparation of carbon paste electrode (EPC) in a solid-contact minicavity and its evaluation when containing carbon paste without and with SiO{sub 2}(Eu{sup 3+} 2%) and SiO{sub 2}(Eu{sup 3+} 2%)-lysine sub-micrometrics particles. For this study cyclic voltammetry and electrochemical impedance measurements were performed at pH 7.4 in 0.1 mol L{sup -1} PBS containing Fe(CN){sub 6}{sup -3}/{sup -4} redox species. The impedance results were interpreted based on a charge-transfer reaction involving Fe(CN){sub 6}{sup -3}/{sup -4} species and/or oxygen at higher frequencies and, diffusion of the electroactive species and carbon paste characteristics at lower frequencies. EPC-minicavity is suitable for electroanalysis using modified carbon paste. (author)

  11. Dry sliding wear behaviour of organo-modified montmorillonite filled epoxy nanocomposites using Taguchi's techniques

    International Nuclear Information System (INIS)

    Rashmi; Renukappa, N.M.; Suresha, B.; Devarajaiah, R.M.; Shivakumar, K.N.

    2011-01-01

    Highlights: → Successful fabrication of OMMT filled epoxy nanocomposites by high-shear mixing mehod. → Systematic tribological behaviour of the nanocomposites was made using Taguchi method. → Worn surface morphologies of the samples were discussed for different wear mechanisms. → Generation of wear data for sliding/bearing parts for different industries. -- Abstract: The aim of the research article is to study the dry sliding wear behaviour of epoxy with different wt.% of organo-modified montmorillonite (OMMT) filled nanocomposites. An orthogonal array (L 9 ) was used to investigate the influence of tribological parameters. The results indicate that the sliding distance emerges as the most significant factor affecting wear rate of epoxy nanocomposites. Experimental results showed that the inclusion of 5 wt.% OMMT nanofiller increased the wear resistance of the epoxy nanocomposite significantly. Furthermore, the worn surfaces of the samples were analyzed by scanning electron microscopy (SEM) to study the wear mechanisms and to correlate them with the wear test results.

  12. Evaluation of a carbon paste electrode modified with Strontium substituted bismuth and titanium oxide nanoparticles in the toxic metal chromium (VI determination potentiometric method

    Directory of Open Access Journals (Sweden)

    Atefeh Badri

    2016-09-01

    Full Text Available Strontium substituted bismuth and titanium oxide nanoparticles with aurivillius morphology synthesized by chemical co-precipitation method and were characterized using XRD. The nanopartcles were used in the composition of the carbon paste to improve conductivity and transduction of chemical signal to electrical signal. A procedure for the determination of chromium is described based on pre-concentration of the dichromate anion at a carbon paste electrode modified. A novel potentiometric Cr6+carbon paste electrode incorporating Strontium substituted bismuth and titanium oxide nanoparticles (SSBTO. Ina acetate buffer solution of pH 5, the sensor displays a rapid and linear response for Cr6+ over the concentration range 1.0×10-5 to 1.0×10-1mol L-1 M with an anionic slope of 54.8± 0.2 mV decade ’ and a detection limit of the order of0.002 /µg ml ‘. The sensor is used for determination of Cr6+ by direct monitoring of Cr6+.The average recoveries of Cr6+at concentration levels of 0.5~40 pg/ml ’is 98.3. The electrode has a short response time (<6s and can be used for at least twenty days without any considerable divergence in potentials and the working pH range was 4.5-6.5. The proposed electrode was successfully used as an indicator for potentiometric determination of Cr6+in water sample.

  13. Removal of remazol yellow with modified clays with iron

    International Nuclear Information System (INIS)

    Diaz-Gomez T, A. P.

    2012-01-01

    Clays have the ability to absorb water and to retain in its structure both hydrophilic and hydrophobic substances, therefore, it is possible to use them in the sorption of dyes from waste water, in order to avoid affecting water bodies or storm drains when they are discharged. In this paper the montmorillonite KSF and a sodium bentonite from the Morelos State, Mexico were studied for the sorption of an azo dye used in textiles knows as remazol yellow. These clays were modified with iron, the dye sorption behaviors and their regeneration processes for their reuse were determined. It was difficult to separate the sodium bentonite after being in contact with aqueous solutions; therefore it was nor a candidate dor the removal of remazol yellow from aqueous solutions. The montmorillonite KSF was characterized before and after the iron modification, and after its regeneration by scanning electron microscopy (elemental analysis), infrared spectrometry, X-ray diffraction, and the specific areas of the materials were determined by Bet analysis. The adsorption equilibrium time and the adsorption rate for remazol yellow were determined from the fitting of the experimental results to mathematical models for the unmodified and iron modified montmorillonite KSF. The adsorption capacity was determined from the adsorption isotherms and mathematical models. The influence of the ph in the sorption processes was determined as well, and it was found that, ph values between 2 and 12 do not have any influence on the adsorption processes for iron modified montmorillonite KSF. The montmorillonite KSF and the iron modified montmorillonite KSF are adequate adsorbents for the removal of remazol yellow from aqueous solutions. Although, the sorption capacity for the unmodified montmorillonite KSF is higher (about 10%) than the capacity for the iron modified montmorillonite KSF and the stability of the last one increased. The saturated clays with remazol yellow were treated with Fenton reactive

  14. Rubber/clay nanocomposites by combined latex compounding and melt mixing: A masterbatch process

    International Nuclear Information System (INIS)

    Tan, Jinghua; Wang, Xiaoping; Luo, Yuanfang; Jia, Demin

    2012-01-01

    Highlights: → Rubber/Ca-montmorillonite nanocomposites were prepared by the masterbatch process. → Latex compounding method is efficient to improve the Ca-montmorillonite dispersion. → Exfoliated structure was obtained in the masterbatch by latex compounding method. → Intercalated and exfoliated structures were achieved in the vulcanizate. → The properties of vulcanizate are improved by the addition of Ca-montmorillonite. -- Abstract: Rubber/Ca-montmorillonite (Ca-MMT) nanocomposites with well exfoliated Ca-MMT layers were prepared by combination of latex compounding and melt mixing. Firstly, a high Ca-MMT content masterbatch was co-coagulated by natural rubber (NR) latex and modified Ca-MMT aqueous suspension through latex compounding. The masterbatch was added in the system of styrene butadiene rubber (SBR) and epoxidized natural rubber (ENR) by melt mixing subsequently. The X-ray diffraction (XRD) and transmission electronic microscopy (TEM) results showed that intercalated and exfoliated nanocomposites were obtained by the masterbatch technique. The effects of modified Ca-MMT introduction into the rubber matrix, via the masterbatch technique, on the properties of the resulting composites were studied. It was found that the vulcanization was hindered by the incorporation of modified Ca-MMT, while mechanical performances, thermal stability and aging resistance were improved. The increasingly glass transition temperature and the storage modulus with the loading of modified Ca-MMT were measured by dynamic mechanical analysis (DMA).

  15. Modified montmorillonite clay microparticles for stable oil-in-seawater emulsions.

    Science.gov (United States)

    Dong, Jiannan; Worthen, Andrew J; Foster, Lynn M; Chen, Yunshen; Cornell, Kevin A; Bryant, Steven L; Truskett, Thomas M; Bielawski, Christopher W; Johnston, Keith P

    2014-07-23

    Environmentally benign clay particles are of great interest for the stabilization of Pickering emulsions. Dodecane-in-synthetic seawater (SSW) emulsions formed with montmorillonite (MMT) clay microparticles modified with bis(2-hydroxyethyl)oleylamine were stable against coalescence, even at clay concentrations down to 0.1% w/v. Remarkably, as little as 0.001% w/v surfactant lowered the hydrophilicity of the clay to a sufficient level for stabilization of oil-in-SSW emulsions. The favorable effect of SSW on droplet size reduction and emulsion stability enhancement is hypothesized to be due to reduced electrostatic repulsion between adsorbed clay particles and a consequent increase in the continuous phase (an aqueous clay suspension) viscosity. Water/oil (W/O) emulsions were inverted to O/W either by decreasing the mass ratio of surfactant-to-clay (transitional inversion) or by increasing the water volume fraction (catastrophic inversion). For both types of emulsions, coalescence was minimal and the sedimentation or creaming was highly correlated with the droplet size. For catastrophic inversions, the droplet size of the emulsions was smaller in the case of the preferred curvature. Suspensions of concentrated clay in oil dispersions in the presence of surfactant were stable against settling. The mass transfer pathways during emulsification of oil containing the clay particles were analyzed on the droplet size/stability phase diagrams to provide insight for the design of dispersant systems for remediating surface and subsurface oceanic oil spills.

  16. Development of carbon paste electrodes modified by molecularly imprinted polymer as potentiometry sensor of uric acid

    Science.gov (United States)

    Khasanah, Miratul; Darmokoesoemo, Handoko; Widayanti, Nesti; Kadmi, Yassine; Elmsellem, Hicham; Kusuma, Heri Septya

    The development of carbon paste electrodes modified by molecularly imprinted polymer (MIP) for the potentiometric analysis of uric acid was carried out in this study. The aim of the study was to determine the optimum composition of the electrode constituent material, the optimum pH of the uric acid solution, and the performance of the electrode, which was measured by its response time, measurement range, Nernst factor, detection limits, selectivity coefficient, precision, accuracy, and life time. MIP was made from methyl methacrylate as the monomer, ethylene glycol dimethacrylate as the cross-linker, and uric acid as the template. Electrodes that give optimum performance were produced from carbon, MIP, and paraffin with a ratio of 40:25:35 (% w/w). The obtained results show that the measurement of uric acid solution gives optimum results at pH 5, Nernst factor of 30.19 mV/decade, and a measurement range of 10-6-10-3 M. The minimum detection limit of this method was 3.03.10-6 M, and the precision and accuracy toward uric acid with concentration of 10-6-10-3 M ranged between 1.36-2.03% and 63.9-166%. The selectivity coefficient value was less than 1, which indicated that the electrode was selective against uric acid and not interfered with by urea. This electrode has a response time of less than 2 min; its life time is 8 weeks with 104 usage times.

  17. Electrochemical oxidation of 4-chloro phenol over a carbon paste electrode modified with Zn Al layered double hydroxides

    International Nuclear Information System (INIS)

    Hernandez F, D.; Palomar P, M.; Licona S, T. de J.; Romero R, M.; Valente, Jaime S.

    2014-01-01

    A study is presented on the electrochemical oxidation of 4-chloro phenol (4cp) in aqueous solution using a bare carbon paste electrode, Cpe, and another one that was modified with Zn Al layered double hydroxides (Cpe/Zn Al-LDH). The electro-oxidation was effected at ph values ranging from 3 up to 11. It was found through cyclic voltammetry that this process was irreversible, namely, there were no reduction peaks, and that depending on the nature of the electrode, the anodic current was limited either by adsorption (Cpe) or diffusion (Cpe/Zn Al-LDH). The energy required and the oxidation reaction rate depended on the ph and on the nature of the electrode, such that the greater rates were obtained when the Cpe/Zn Al-LDH electrode and acid ph were used. The Zn Al-LDH was characterized by means of X-ray diffraction. (Author)

  18. Electrochemical oxidation of 4-chloro phenol over a carbon paste electrode modified with Zn Al layered double hydroxides

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez F, D.; Palomar P, M.; Licona S, T. de J.; Romero R, M. [Universidad Autonoma Metropolitana, Unidad Azcapotzalco, Departamento de Materiales, Av. San Pablo 180, Col. Reynosa-Tamaulipas, 02200 Mexico D. F. (Mexico); Valente, Jaime S., E-mail: mepp@correo.azc.uam.mx [Instituto Mexicano del Petroleo, Eje Central No. 152, 07730 Mexico D. F. (Mexico)

    2014-07-01

    A study is presented on the electrochemical oxidation of 4-chloro phenol (4cp) in aqueous solution using a bare carbon paste electrode, Cpe, and another one that was modified with Zn Al layered double hydroxides (Cpe/Zn Al-LDH). The electro-oxidation was effected at ph values ranging from 3 up to 11. It was found through cyclic voltammetry that this process was irreversible, namely, there were no reduction peaks, and that depending on the nature of the electrode, the anodic current was limited either by adsorption (Cpe) or diffusion (Cpe/Zn Al-LDH). The energy required and the oxidation reaction rate depended on the ph and on the nature of the electrode, such that the greater rates were obtained when the Cpe/Zn Al-LDH electrode and acid ph were used. The Zn Al-LDH was characterized by means of X-ray diffraction. (Author)

  19. Preparation of calcium phosphate paste

    International Nuclear Information System (INIS)

    Mohd Reusmaazran Yusof; Norzita Yaacob; Idris Besar; Che Seman Mahmood; Rusnah Mustafa

    2010-01-01

    Calcium phosphate paste were prepared by mixing between calcium sodium potassium phosphate, Ca 2 NaK (PO 4 ) 2 (CSPP) and monocalcium phosphate monohydrate, Ca(H 2 PO 4 ) 2 .H 2 O (MCPM). CSPP were obtained by reaction between calcium hydrogen phosphate (CaHPO 4 ), potassium carbonate (K 2 CO 3 ) and sodium carbonate (Na 2 CO 3 ) in solid state sintering process followed by quenching in air at 1000 degree Celsius. The paste was aging in simulated body fluid (SBF) for 0.5, 1, 3, 6, 12, 24, 48 hrs, 3, 7 and 14 days. The morphological investigation indicated the formation of apatite crystal were first growth after 24 hours. The obvious growth of apatite crystal was shown at 3 days. The obvious growth of apatite crystal was shown in 7 and 14 days indicated the prediction of paste would have rapid reaction with bone after implantation. (author)

  20. Behind adhesion of uranyl onto montmorillonite surface: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    Yang, W.; Zaoui, A., E-mail: azaoui@polytech-lille.fr

    2013-10-15

    Highlights: • We investigated the adsorption of uranyl onto Montmorillonite surface. • We studied the surface energy between layered Montmorillonite sheets. • We studied the work of adhesion between radionuclide and charged Montmorillonite. -- Abstract: We have performed molecular dynamics simulations to investigate the adsorption of radionuclide elements species onto substituted Montmorillonite (001) surface in the presence of different counterions. The structure and the dynamics of uranyl ion as well as its aquo, chloride ion, and carbonate complexes are analyzed. In addition, we have studied the surface energy between layered Montmorillonite sheets and the work of adhesion between radionuclide and charged Montmorillonite. The clay model used here is a Wyoming-type Montmorillonite with 0.75e negative charge per unit cell resulting from substitutions in Octahedral and Tetrahedral sheets. The system model was constructed based on CLAYFF force field potential model. To evaluate the thermodynamic work of adhesion, each surface and clay layer regions are converted to a thin film model. One and two species of radionuclide elements (UO{sub 2}(H{sub 2}O){sub 5},UO{sub 2}CO{sub 3}(H{sub 2}O){sub 5}, and UO{sub 2}Cl{sub 2}(H{sub 2}O){sub 5}) were deposited near the clay surface in a pseudo-two-dimensional periodic cell. Analysis shows that the uranyl ion structure is preserved with two axial oxygen atoms detected at 1.8 Å. Radial distribution functions results indicate that average U-O{sub w} distances are 2.45–2.61 Å, and 2.29–2.40 Å for U-O{sub c} distance. Average U-Cl distances are 2.78–3.08 Å, which is relatively larger than that of Uranium atom-Oxygen atom because of electrostatic factors.

  1. Effect of one step KOH activation and CaO modified carbon in transesterification reaction

    Science.gov (United States)

    Yacob, Abd Rahim; Zaki, Muhammad Azam Muhammad

    2017-11-01

    In this work, one step activation was introduced using potassium hydroxide (KOH) and calcium oxide (CaO) modified palm kernel shells. Various concentration of calcium oxide was used as catalyst while maintaining the same concentration of potassium hydroxide to activate and impregnate the palm kernel shell before calcined at 500°C for 5 hours. All the prepared samples were characterized using Fourier Transform Infrared (FTIR) and Field Emission Scanning Electron Microscope (FESEM). FTIR analysis of raw palm kernel shell showed the presence of various functional groups. However, after activation, most of the functional groups were eliminated. The basic strength of the prepared samples were determined using back titration method. The samples were then used as base heterogeneous catalyst for the transesterification reaction of rice bran oil with methanol. Analysis of the products were performed using Gas Chromatography Flame Ionization Detector (GC-FID) to calculate the percentage conversion of the biodiesel products. This study shows, as the percentage of one step activation potassium and calcium oxide doped carbon increases thus, the basic strength also increases followed by the increase in biodiesel production. Optimization study shows that the optimum biodiesel production was at 8 wt% catalyst loading, 9:1 methanol: oil molar ratio at 65°C and 6 hours which gives a conversion up to 95%.

  2. Electrocatalytic and simultaneous determination of isoproterenol, uric acid and folic acid at molybdenum (VI) complex-carbon nanotube paste electrode

    International Nuclear Information System (INIS)

    Beitollahi, Hadi; Sheikhshoaie, Iran

    2011-01-01

    Highlights: → A molybdenum (VI) complex-carbon nanotube paste electrode have been fabricated. → This electrode reduced the oxidation potential of isoproterenol by about 175 mV. → It resolved the voltammetric waves of isoproterenol, uric acid and folic acid. - Abstract: This paper describes the development, electrochemical characterization and utilization of a novel modified molybdenum (VI) complex-carbon nanotube paste electrode for the electrocatalytic determination of isoproterenol (IP). The electrochemical profile of the proposed modified electrode was analyzed by cyclic voltammetry (CV) that showed a shift of the oxidation peak potential of IP at 175 mV to less positive value, compared with an unmodified carbon paste electrode. Differential pulse voltammetry (DPV) in 0.1 M phosphate buffer solution (PBS) at pH 7.0 was performed to determine IP in the range from 0.7 to 600.0 μM, with a detection limit of 35.0 nM. Then the modified electrode was used to determine IP in an excess of uric acid (UA) and folic acid (FA) by DPV. Finally, this method was used for the determination of IP in some real samples.

  3. Carbon paste electrode with covalently immobilized thionine for electrochemical sensing of hydrogen peroxide

    Science.gov (United States)

    Thenmozhi, K.; Sriman Narayanan, S.

    2017-11-01

    A water-soluble redox mediator, thionin was covalently immobilized to the functionalized graphite powder and a carbon paste electrode was fabricated from this modified graphite powder. The immobilization procedure proved to be effective in anchoring the thionin mediator in the graphite electrode setup without any leakage problem during the electrochemical studies. The covalent immobilization of the thionin mediator was studied with FT-IR and the electrochemical response of the thionin carbon paste electrode was optimized on varying the supporting electrolyte, pH and scan rate. The modified electrode exhibited well-defined electrocatalytic activity towards the reduction of H2O2 at a lower potential of -0.266 V with good sensitivity. The developed amperometric sensor was efficient towards H2O2 in the linear range from 2.46 × 10-5 M to 4.76 × 10-3 M, with a detection limit of 1.47 × 10-5 M respectively. Important advantages of this sensor are its excellent electrochemical performance, simple fabrication, easy renewability, reproducible analytical results, acceptable accuracy and good operational and long-term stability.

  4. Cation exchange interaction between antibiotic ciprofloxacin and montmorillonite

    International Nuclear Information System (INIS)

    Wang, Chih-Jen; Li, Zhaohui; Jiang, Wei-Teh; Jean, Jiin-Shuh; Liu, Chia-Chuan

    2010-01-01

    Exploring the interactions between antibiotics and soils/minerals is of great importance in resolving their fate, transport, and elimination in the environment due to their frequent detection in wastewater, river water, sewage sludge and soils. This study focused on determining the adsorption properties and mechanisms of interaction between antibiotic ciprofloxacin and montmorillonite (SAz-1), a swelling dioctahedral mineral with Ca 2+ as the main interlayer cation. In acidic and neutral aqueous solutions, a stoichiometric exchange between ciprofloxacin and interlayer cations yielded an adsorption capacity as high as 330 mg/g, corresponding to 1.0 mmol/g. When solution pH was above its pK a2 (8.7), adsorption of ciprofloxacin was greatly reduced due to the net repulsion between the negatively charged clay surfaces and the ciprofloxacin anion. The uptake of ciprofloxacin expanded the basal spacing (d 001 ) of montmorillonite from 15.04 to 17.23 A near its adsorption capacity, confirming cation exchange within the interlayers in addition to surface adsorption. Fourier transform infrared results further suggested that the protonated amine group of ciprofloxacin in its cationic form was electrostatically attracted to negatively charged sites of clay surfaces, and that the carboxylic acid group was hydrogen bonded to the basal oxygen atoms of the silicate layers. The results indicate that montmorillonite is an effective sorbent to remove ciprofloxacin from water.

  5. Cation exchange interaction between antibiotic ciprofloxacin and montmorillonite

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chih-Jen [Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Department of Geosciences, National Taiwan University, Taipei 10617, Taiwan (China); Li, Zhaohui, E-mail: li@uwp.edu [Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Department of Geosciences, University of Wisconsin - Parkside, Kenosha, WI 53144 (United States); Jiang, Wei-Teh, E-mail: atwtj@mail.ncku.edu.tw [Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China); Jean, Jiin-Shuh; Liu, Chia-Chuan [Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 70101, Taiwan (China)

    2010-11-15

    Exploring the interactions between antibiotics and soils/minerals is of great importance in resolving their fate, transport, and elimination in the environment due to their frequent detection in wastewater, river water, sewage sludge and soils. This study focused on determining the adsorption properties and mechanisms of interaction between antibiotic ciprofloxacin and montmorillonite (SAz-1), a swelling dioctahedral mineral with Ca{sup 2+} as the main interlayer cation. In acidic and neutral aqueous solutions, a stoichiometric exchange between ciprofloxacin and interlayer cations yielded an adsorption capacity as high as 330 mg/g, corresponding to 1.0 mmol/g. When solution pH was above its pK{sub a2} (8.7), adsorption of ciprofloxacin was greatly reduced due to the net repulsion between the negatively charged clay surfaces and the ciprofloxacin anion. The uptake of ciprofloxacin expanded the basal spacing (d{sub 001}) of montmorillonite from 15.04 to 17.23 A near its adsorption capacity, confirming cation exchange within the interlayers in addition to surface adsorption. Fourier transform infrared results further suggested that the protonated amine group of ciprofloxacin in its cationic form was electrostatically attracted to negatively charged sites of clay surfaces, and that the carboxylic acid group was hydrogen bonded to the basal oxygen atoms of the silicate layers. The results indicate that montmorillonite is an effective sorbent to remove ciprofloxacin from water.

  6. Enhanced proton conductivity by the influence of modified montmorillonite on poly (vinyl alcohol) based blend composite membranes

    Energy Technology Data Exchange (ETDEWEB)

    Palani, P. Bahavan, E-mail: bahavanpalani@gmail.com; Abidin, K. Sainul [Department of Physics, University College of Engineering, Anna University, Dindigul-624622 (India); Kannan, R., E-mail: rksrsrk@gmail.com [Department of Physics, University College of Engineering, Anna University, Dindigul-624622 (India); Department of Material Sciences & Engineering, Cornell University, Ithaca, NewYork-14853 (United States); Rajashabala, S. [School of Physics, Madurai Kamaraj University, Madurai-625021 (India); Sivakumar, M. [School of Physics, Alagappa University, Karaikudi-630004 (India)

    2016-05-23

    The highest proton conductivity value of 0.0802 Scm{sup −1} is obtained at 6 wt% of protonated MMT added to the PVA/PEG blends. The polymer blend composite membranes are prepared with varied concentration of Poly vinyl alcohol (PVA), Poly ethylene glycol (PEG) and Montmorillonite (MMT) by solution casting method. The Na{sup +} MMT was modified (protonated) to H{sup +} MMT with ion exchange process. The prepared membranes were characterized by using TGA, FTIR, XRD, Ion Exchange Capacity, Water/Methanol uptake, swelling ratio and proton conductivity. The significant improvements in the hydrolytic stability were observed. In addition, thermal stability of the composite membranes were improved and controlled by the addition of MMT. All the prepared membranes are shown appreciable values of proton conductivity at room temperature with 100% relative humidity.

  7. Investigations of the Montmorillonite and Aluminium Trihydrate Addition Effects on the Ignitability and Thermal Stability of Asphalt

    Directory of Open Access Journals (Sweden)

    Kai Zhu

    2014-01-01

    Full Text Available By means of limiting oxygen index (LOI, cone calorimeter, and TG-DSC tests, this paper investigated the effect of unmodified montmorillonite (MMT, organically modified montmorillonite (OMMT, and aluminium trihydrate (ATH additions on the flame retardancy for asphalt combustion. Experimental results showed that adding a small amount of montmorillonite did not significantly increase the oxygen index of the asphalt but reduced the heat release rate during asphalt combustion. TGA tests had indicated that the montmorillonite (MMT and OMMT could suppress the release of flammable volatiles and form more asphaltenes, which hence postponed the burnout time of asphalt. Furthermore, the combination of montmorillonite (MMT and OMMT and ATH had yielded a synergistic effect, which had further reduced the heat release rate and also increased the oxygen index of asphalt. In particular, after further addition of OMMT, the barrier layer showed less crack, leading to a significant decrease in the heat release rate as compared to the adding of ATH alone.

  8. Chemically modified carbon paste electrode for fast screening of oxalic acid levels in soil solutions

    Czech Academy of Sciences Publication Activity Database

    Šestáková, Ivana; Jakl, M.; Jaklová Dytrtová, J.

    2008-01-01

    Roč. 102, - (2008), s. 140-140 E-ISSN 1213-7103. [International Conference on Electroanalysis /12./. 16.06.2008-19.06.2008, Prague] R&D Projects: GA ČR GA521/06/0496 Institutional research plan: CEZ:AV0Z40400503 Keywords : oxalic acid * carbon paste electrodes * soil solutions Subject RIV: CG - Electrochemistry

  9. Optimization of modified carbon paste electrode with multiwalled carbon nanotube/ionic liquid/cauliflower-like gold nanostructures for simultaneous determination of ascorbic acid, dopamine and uric acid

    International Nuclear Information System (INIS)

    Afraz, Ahmadreza; Rafati, Amir Abbas; Najafi, Mojgan

    2014-01-01

    We describe the modification of a carbon paste electrode (CPE) with multiwalled carbon nanotubes (MWCNTs) and an ionic liquid (IL). Electrochemical studies by using a D-optimal mixture design in Design-Expert software revealed an optimized composition of 60% graphite, 14.2% paraffin, 10.8% MWCNT and 15% IL. The optimal modified CPE shows good electrochemical properties that are well matched with model prediction parameters. In the next step, the optimized CPE was modified with gold nanostructures by applying a double-pulse electrochemical technique. The resulting electrode was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and electrochemical impedance spectroscopy. It gives three sharp and well-separated oxidation peaks for ascorbic acid (AA), dopamine (DA), and uric acid (UA). The sensor enables simultaneous determination of AA, DA and UA with linear responses from 0.3 to 285, 0.08 to 200, and 0.1 to 450 μM, respectively, and with 120, 30 and 30 nM detection limits (at an S/N of 3). The method was successfully applied to the determination of AA, DA, and UA in spiked samples of human serum and urine. - Highlights: • New method for simultaneous determination of AA, DA and UA was developed. • MWCNT/ionic liquid/cauliflower-like Au nanostructure was used for CPE modification. • Optimization of electrode composition was done by Design-Expert software. • The pH effect, peak separation mechanism and real samples was thoroughly studied

  10. Optimization of modified carbon paste electrode with multiwalled carbon nanotube/ionic liquid/cauliflower-like gold nanostructures for simultaneous determination of ascorbic acid, dopamine and uric acid

    Energy Technology Data Exchange (ETDEWEB)

    Afraz, Ahmadreza [Department of Physical Chemistry, Faculty of Chemistry, Bu-Ali Sina University, P.O. Box 65174, Hamedan (Iran, Islamic Republic of); Rafati, Amir Abbas, E-mail: aa_rafati@basu.ac.ir [Department of Physical Chemistry, Faculty of Chemistry, Bu-Ali Sina University, P.O. Box 65174, Hamedan (Iran, Islamic Republic of); Najafi, Mojgan [Department of Materials Engineering, Hamedan University of Technology (HUT), 65169 Hamedan (Iran, Islamic Republic of)

    2014-11-01

    We describe the modification of a carbon paste electrode (CPE) with multiwalled carbon nanotubes (MWCNTs) and an ionic liquid (IL). Electrochemical studies by using a D-optimal mixture design in Design-Expert software revealed an optimized composition of 60% graphite, 14.2% paraffin, 10.8% MWCNT and 15% IL. The optimal modified CPE shows good electrochemical properties that are well matched with model prediction parameters. In the next step, the optimized CPE was modified with gold nanostructures by applying a double-pulse electrochemical technique. The resulting electrode was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and electrochemical impedance spectroscopy. It gives three sharp and well-separated oxidation peaks for ascorbic acid (AA), dopamine (DA), and uric acid (UA). The sensor enables simultaneous determination of AA, DA and UA with linear responses from 0.3 to 285, 0.08 to 200, and 0.1 to 450 μM, respectively, and with 120, 30 and 30 nM detection limits (at an S/N of 3). The method was successfully applied to the determination of AA, DA, and UA in spiked samples of human serum and urine. - Highlights: • New method for simultaneous determination of AA, DA and UA was developed. • MWCNT/ionic liquid/cauliflower-like Au nanostructure was used for CPE modification. • Optimization of electrode composition was done by Design-Expert software. • The pH effect, peak separation mechanism and real samples was thoroughly studied.

  11. Silver nanoparticles in montmorillonite to application in polymeric materials

    International Nuclear Information System (INIS)

    Morita, R.Y.; Barbosa, R.V.; Kloss, J.R.; Schnitzler, M.; Garcia, J.

    2012-01-01

    This work presents the preparation of silver nanoparticles (AgNPs) through industrially viable methodologies and free of organic solvents, and their insertion in montmorillonite, to produce a nanomaterial with bactericidal properties. The modified montmorillonite was characterized through the techniques of Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and x-ray diffraction (XRD). The FTIR and Raman spectrum's showed specific bands of involving stretching silver. In the XRD analyses was observed the occurrence of the following crystallographic planes (111), (200) e (220) silver related. For application in low density polyethylene, the mechanical tests showed no loss in the mechanical properties, when the AgNPs is present, this fact is important and indicate that the nanomaterial can be inserted in this polymer matrix with considerable technology interest. (author)

  12. Oxidized multi walled carbon nanotubes for improving the electrocatalytic activity of a benzofuran derivative modified electrode

    Directory of Open Access Journals (Sweden)

    Mohammad Mazloum-Ardakani

    2016-01-01

    Full Text Available In the present paper, the use of a novel carbon paste electrode modified by 7,8-dihydroxy-3,3,6-trimethyl-3,4-dihydrodibenzo[b,d]furan-1(2H-one (DTD and oxidized multi-walled carbon nanotubes (OCNTs is described for determination of levodopa (LD, acetaminophen (AC and tryptophan (Trp by a simple and rapid method. At first, the electrochemical behavior of DTD is studied, then, the mediated oxidation of LD at the modified electrode is investigated. At the optimum pH of 7.4, the oxidation of LD occurs at a potential about 330 mV less positive than that of an unmodified carbon paste electrode. Based on differential pulse voltammetry (DPV, the oxidation current of LD exhibits a linear range between 1.0 and 2000.0 μM of LD with a detection limit (3σ of 0.36 μM. DPV was also used for simultaneous determination of LD, AC and Trp at the modified electrode. Finally, the proposed electrochemical sensor was used for determinations of these substances in human serum sample.

  13. In situ prepared PET nanocomposites: Effect of organically modified montmorillonite and fumed silica nanoparticles on PET physical properties and thermal degradation kinetics

    International Nuclear Information System (INIS)

    Vassiliou, A.A.; Chrissafis, K.; Bikiaris, D.N.

    2010-01-01

    In the present study a series of PET nanocomposites were prepared by in situ polymerization using different amounts of organically modified montmorillonite (OMMT) with a triphenylphosphine compound and fumed silica nanoparticles (SiO 2 ). As verified by TEM micrographs, the dispersion of both nanoparticles into the PET matrix was homogeneous while montmorillonite was dispersed in the exfoliated form. The intrinsic viscosities of the prepared nanocomposites were affected by the addition of the nanoparticles and in both cases a slight increase was observed. Tensile strength was also increased by increasing nanoparticles content while both types of nanoparticles act as nucleating agents, enhancing the crystallization rates of PET. From the thermogravimetric curves it was concluded that PET and the samples with different nanoparticles presented good thermostability, since no remarkable mass loss occurred up to 320 o C ( 2 2 wt.% nanocomposites was almost identical (222.1 kJ/mol). However, PET/OMMT 2 wt.% nanocomposites exhibited a higher activation energy (228.3 kJ/mol), indicating that OMMT incurred a stabilizing effect upon the decomposition of the matrix. The form of the conversion function for all the studied samples obtained by fitting was the mechanism of n th -order auto-catalysis.

  14. Fabrication and anti-frosting performance of super hydrophobic coating based on modified nano-sized calcium carbonate and ordinary polyacrylate

    Energy Technology Data Exchange (ETDEWEB)

    Wang Hao [Department of Chemical Engineering, Tsinghua University, Beijing 100084 (China); Tang Liming [Department of Chemical Engineering, Tsinghua University, Beijing 100084 (China)], E-mail: tanglm@mail.tsinghua.edu.cn; Wu Xiaomin; Dai Wantian [Department of Thermal Engineering, Tsinghua University, Beijing 100084 (China); Qiu Yipeng [Department of Chemical Engineering, Tsinghua University, Beijing 100084 (China)

    2007-09-15

    Nano-sized calcium carbonate (CaCO{sub 3}) particles were modified by heptadecafluorodecyl trimethoxysilane under acidic water condition. An ordinary polyacrylate prepared via radical copolymerization of methyl methacrylate, butyl acrylate, acrylic acid and {beta}-hydroxyethyl methacrylate was used as the binder to form hydrophobic coatings with the modified CaCO{sub 3}. Super hydrophobic coating with water contact angle of 155{sup o} was obtained from modified CaCO{sub 3} and the polyacrylate at their weight ratio of 8/2 by a simple procedure. Based on surface analysis by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS), the super hydrophobicity can be attributed to both the surface microstructure and surface enrichment of fluoroalkyl chains. Due to a low water sliding angle, carbon black powder on super hydrophobic surface was easily removed by rolling water droplet. Furthermore, the anti-frosting performance of different surfaces was investigated, which indicated that the frost formed on superhydrophobic surface was greatly retarded compared with that on bare copper surface. The surface kept super hydrophobicity even after freezing-thawing treatment for 10 times.

  15. Monte Carlo studies of TPP+ and BE+ arrangements in the interlayer and at the external surface of montmorillonite

    International Nuclear Information System (INIS)

    Jeschke, F.; Meleshyn, A.

    2010-01-01

    Document available in extended abstract form only. Unlike natural clay minerals, organically modified montmorillonite possesses a very high sorption capacity for anions, which favors its use for waste storage and sewage purposes. Understanding of this anion sorption requires a detailed knowledge about the underlying structure, which is only partially accessible with currently applied experimental methods. To get more structural information, Na-montmorillonite modified with tetraphenyl-phosphonium (TPP + , (C 6 H 5 ) 4 P + ) chloride or benzethonium (BE + , C 27 H 42 O 2 N + ) chloride was simulated using the Metropolis Monte Carlo method as extended by the configurational-bias procedure for flexible organic molecules. The simulated interlayer content of TPP + varied between 8% and 100% of CEC (cation exchange capacity). Two different initial arrangements of TPP + were considered, taking into account experimentally derived suggestions: 1) 'mono-facial' arrangement with three of the phenyl groups of all TPP + aligned to the same basal surface, and 2) 'bi-facial' arrangement with an equivalent distribution of phenyl groups between the two opposite basal surfaces of the montmorillonite. Pressure, temperature and number of particles were kept constant whereas the layer spacing was allowed to vary during the simulations. The OPLS-AA force field was used for calculation of the intermolecular and intramolecular interactions and Ewald summation was used to calculate the electrostatic interactions. The layer spacings, determined for the first arrangement, are between 17.4 A for the lowest and 19 A for the highest TPP + contents and show a very good agreement with experimental values. For this arrangement, a segregation of organic (TPP + ) and inorganic (Na + , Cl - and H 2 O) phases is observed. On the contrary, the simulated layer spacings for the second arrangement agree with the experimental data only for lower contents of TPP + . For higher contents

  16. Bioelectrocatalytic mediatorless dioxygen reduction at carbon ceramic electrodes modified with bilirubin oxidase

    International Nuclear Information System (INIS)

    Nogala, Wojciech; Celebanska, Anna; Szot, Katarzyna; Wittstock, Gunther; Opallo, Marcin

    2010-01-01

    Carbon ceramic electrodes were prepared by sol-gel processing of a hydrophobic precursor - methyltrimethoxysilane (MTMOS) - together with dispersed graphite microparticles according to a literature procedure. Bilirubin oxidase (BOx) was adsorbed on this electrode from buffer solution and this process was followed by atomic force microscopy (AFM). The electrodes exhibited efficient mediatorless electrocatalytic activity towards dioxygen reduction. The activity depends on the time of adsorption of the enzyme and the pH. The electrode remains active in neutral solution. The bioelectrocatalytic activity is further increased when a fraction of the carbon microparticles is replaced by sulfonated carbon nanoparticles (CNPs). This additive enhances the electrical communication between the enzyme and the electronic conductor. At pH 7 the carbon ceramic electrode modified with bilirubin oxidase retains ca. half of its highest activity. The role of the modified nanoparticles is confirmed by experiments in which a film embedded in a hydrophobic silicate matrix also exhibited efficient mediatorless biocatalytic dioxygen reduction. Scanning electrochemical microscopy (SECM) of the studied electrodes indicated a rather even distribution of the catalytic activity over the electrode surface.

  17. A high sensitive biosensor based on FePt/CNTs nanocomposite/N-(4-hydroxyphenyl)-3,5-dinitrobenzamide modified carbon paste electrode for simultaneous determination of glutathione and piroxicam.

    Science.gov (United States)

    Karimi-Maleh, Hassan; Tahernejad-Javazmi, Fahimeh; Ensafi, Ali A; Moradi, Reza; Mallakpour, Shadpour; Beitollahi, Hadi

    2014-10-15

    This study describes the development, electrochemical characterization and utilization of novel modified N-(4-hydroxyphenyl)-3,5-dinitrobenzamide-FePt/CNTs carbon paste electrode for the electrocatalytic determination of glutathione (GSH) in the presence of piroxicam (PXM) for the first time. The synthesized nanocomposite was characterized with different methods such as TEM and XRD. The modified electrode exhibited a potent and persistent electron mediating behavior followed by well-separated oxidation peaks of GSH and PXM. The peak currents were linearly dependent on GSH and PXM concentrations in the range of 0.004-340 and 0.5-550 µmol L(-1), with detection limits of 1.0 nmol L(-1) and 0.1 µmolL(-1), respectively. The modified electrode was successfully used for the determination of the analytes in real samples with satisfactory results. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Hexadimethrine-montmorillonite nanocomposite: Characterization and application as a pesticide adsorbent

    International Nuclear Information System (INIS)

    Gámiz, B.; Hermosín, M.C.; Cornejo, J.; Celis, R.

    2015-01-01

    Graphical abstract: - Highlights: • Characterization of hexadimethrine-montmorillonite nanocomposite was appraised. • Comparative studies with traditional HDTMA-montmorillonite were performed. • We investigated the pesticide adsorption mechanisms displayed by the nanocomposites. • Hexadimethrine-nanocomposite showed selective affinity for anionic pesticides. - Abstract: The goal of this work was to prepare and characterize a novel functional material by the modification of SAz-1 montmorillonite with the cationic polymer hexadimethrine (SA-HEXAD), and to explore the potential use of this nanocomposite as a pesticide adsorbent. Comparative preparation and characterization with the well-known hexadecyltrimethylammonium-modified SAz-1 montmorillonite (SA-HDTMA) was also assessed. The characterization was performed by elemental analysis, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), physisorption of N 2 , scanning electron microscopy (SEM) and Z potential measurements. The characterization and adsorption experiments showed that the extent of pesticide adsorption was markedly subjected to the structure and features of the surface of each organo-clay and also to the nature of the considered pesticide. SA-HEXAD displayed a high affinity for anionic pesticides which, presumably, were adsorbed by electrostatic attraction on positively-charged ammonium groups of the polymer not directly interacting with the clay. In contrast, SA-HDTMA displayed great adsorption of both uncharged and anionic pesticides with predominance of hydrophobic interactions. This work provided information about the surface properties of a new organic–inorganic nanohybrid material, SA-HEXAD, and its potential as an adsorbent for the removal of anionic organic pollutants from aqueous solutions

  19. Surface complexation modeling of Cd(II) sorption to montmorillonite, bacteria, and their composite

    Science.gov (United States)

    Wang, Ning; Du, Huihui; Huang, Qiaoyun; Cai, Peng; Rong, Xingmin; Feng, Xionghan; Chen, Wenli

    2016-10-01

    Surface complexation modeling (SCM) has emerged as a powerful tool for simulating heavy metal adsorption processes on the surface of soil solid components under different geochemical conditions. The component additivity (CA) approach is one of the strategies that have been widely used in multicomponent systems. In this study, potentiometric titration, isothermal adsorption, zeta potential measurement, and extended X-ray absorption fine-structure (EXAFS) spectra analysis were conducted to investigate Cd adsorption on 2 : 1 clay mineral montmorillonite, on Gram-positive bacteria Bacillus subtilis, and their mineral-organic composite. We developed constant capacitance models of Cd adsorption on montmorillonite, bacterial cells, and mineral-organic composite. The adsorption behavior of Cd on the surface of the composite was well explained by CA-SCM. Some deviations were observed from the model simulations at pH SCM closely coincided with the estimated value of EXAFS at pH 6. The model could be useful for the prediction of heavy metal distribution at the interface of multicomponents and their risk evaluation in soils and associated environments.

  20. Montmorillonite Nanoparticles

    Directory of Open Access Journals (Sweden)

    H. Almasi

    2009-12-01

    Full Text Available Novel citric acid modified starch-carboxy methyl cellulose (CMC -montmorillonite (MMT bionanocomposite films were prepared by casting method and the effect of MMT on the structural and physical properties of the starch-CMC biocomposites was studied. X-ray diffraction test showed thatstrong polar interactions between the hydroxyl groups present in the starch and CMC chains and in the silicate layers led to intercalation of biopolymer chains into MMT layers galleries. The water vapor permeability decreased from 2.44 to 1.13×10-7 g/mhPa as the MMT percentage increased from0 to 7%. At the level of 7% MMT, the composite films showed the highest ultimate tensile strength (27.55 MPa and lowest strain-to-break (18.25%. The DSC tests showed that, the temperature position of the melting peak increased from 221.5°C to 243.0°C as MMT content increased from 1 to 7%, but the glass transition decreased and gradually disappeared.

  1. Gold-copper bimetallic nanoparticles supported on nano P zeolite modified carbon paste electrode as an efficient electrocatalyst and sensitive sensor for determination of hydrazine.

    Science.gov (United States)

    Amiripour, Fatemeh; Azizi, Seyed Naser; Ghasemi, Shahram

    2018-06-01

    In this report, a facile, efficient and low cost electrochemical sensor based on bimetallic Au-Cu nanoparticles supported on P nanozeolite modified carbon paste electrode (Au-Cu/NPZ/CPE) was constructed and its efficiency for determination of hydrazine in trace level was studied. For this purpose, agro waste material, stem sweep ash (SSA) was employed as the starting material (silica source) for the synthesis of nano P zeolite (NPZ). After characterization of the synthesized NPZ by analytical instruments (scanning electronic microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy), construction of Au-Cu/NPZ/CPE was performed by three steps procedure involving preparation of nano P zeolite modified carbon paste electrode (NPZ/CPE), introducing Cu +2 ions into nano zeolite structure by ion exchange and electrochemical reduction of Cu +2 ions upon applying constant potential. This procedure is followed by partial replacement of Cu by Au due to galvanic replacement reaction (GRR). The electrochemical properties of hydrazine at the surface of Au-Cu/NPZ/CPE was evaluated using cyclic voltammetry (CV), amperometry, and chronoamperometry methods in 0.1 M phosphate buffer solution (PBS). It was found that the prepared sensor has higher electrocatalytic activity at a relatively lower potential compared to other modified electrodes including Au/NPZ/CPE, Cu/NPZ/CPE, Au-Cu/CPE and etc. Moreover, the proposed electrochemical sensor presented the favorable analytical properties for determination of hydrazine such as low detection limit (0.04 µM), rapid response time (3 s), wide linear range (0.01-150 mM), and high sensitivity (99.53 µA mM -1 ) that are related to the synergic effect of bimetallic of Au-Cu, porous structure and enough surface area of NPZ. In addition, capability of Au-Cu/NPZ/CPE sensor was successfully tested in real samples with good accuracy and precision. Copyright

  2. Sorption of tetracycline on organo-montmorillonites

    International Nuclear Information System (INIS)

    Liu, Niu; Wang, Ming-xia; Liu, Ming-ming; Liu, Fan; Weng, Liping; Koopal, Luuk K.; Tan, Wen-feng

    2012-01-01

    Highlights: ► The sorption capacity of tetracycline on Mont. modified with QACs was highly promoted. ► Tetracycline adsorbed on organoclay was affected by the amount and the length of QACs. ► Tetracycline adsorption on organoclay exhibited high pH-dependence below 5. - Abstract: Tetracycline (TC) is a veterinary antibiotic that is frequently detected as pollutant in the environment. Powerful adsorbents are required for removing TC. The present paper compares the TC adsorption capacity of Na-montmorillonite (Na-mont) with six organo-montmorillonites (organo-monts). Three quaternary ammonium cations (QACs) with different alkyl-chain lengths were used as modifiers. Powder X-ray diffraction indicated that the d 001 values of organo-monts increased with increasing the QACs loading and alkyl-chain length. The CECs of the organo-monts were substantially lower than that of Na-mont and decreased with QACs chain length and increased loading. The modeling of the adsorption kinetics revealed that the processes of TC adsorption on the tested samples could be well fitted by the pseudo-second-order equation. The maximum adsorption capacities of TC on the organo-monts (1000–2000 mmol/kg) were considerably higher than that on Na-mont (769 mmol/kg). Both the Langmuir and Freundlich model could fit the adsorption isotherms. The TC adsorption to the organo-monts increase significantly with decreasing the pH below 5.5 because of the electrostatic interaction, and a high QACs loading performed better than a low loading at around pH 3.

  3. Development of plasticised nano-biocomposites of poly(hydroxybutyrate-co-hydroxyvalerate)/montmorillonite organically modified (PHBV/OMMT)

    International Nuclear Information System (INIS)

    Correa, M.C.; Pollet, E.; Averous, L.; Agnell, J.A.M.; Nascente, P.A.P.

    2010-01-01

    Several studies have aimed to improve the properties of biopolymers by the incorporation of nano-sized fillers, such as organo-modified montmorillonite (OMMT), to form nano-biocomposites. The objective of this work is to investigate the influence of acetyl tributyl citrate (ATBC) plasticizer with PHBV/OMMT nano-biocomposites aiming at improving their behavior. The materials PHBV, OMMT (C30B), and ATBC were provided by PHB Industrial S/A (Brazil), Southern Clay Products (USA), and Scandiflex S/A (Brazil), respectively. In this study the processing parameters and the formulations were controlled, pursuing materials with good mechanical and barrier properties with high biodegradability and with greater ease of processing. The analysis of the results obtained by TGA, GPC, WAXS, DSC, mechanical properties, and biodegradability lead to the conclusion that the addition of plasticizer in nanobiocomposites improved processability and did not influence the state of nano-sized load dispersion. It can be concluded that the addition of plasticizer is a good alternative to the processability of nanocomposites of PHAs. (author)

  4. Sorption and direct speciation of neptunium(V) on aluminium oxide and montmorillonite

    International Nuclear Information System (INIS)

    Wendt, Sonja

    2009-01-01

    This study comprised batch experiments, direct speciation studies via EXAFS, and modelling with the 2SPNE SC/CE model to elucidate the mechanisms of Np(V) sorption on montmorillonite and, for reference, on γ-Al 2 O 3 . The sorption of pM 239 Np(V) and μM 237 Np(V) on montmorillonite (STx-1, 4 g/L) and γ-Al 2 O 3 (0.5 g/L) was studied at room temperature in the presence and absence of ambient CO 2 covering a pH-range from 2.5 (STx-1) or 5 (γ-Al 2 O 3 ) to 10.5 with 0.01 or 0.1M NaClO 4 as background electrolyte. The Np(V) uptake was determined by γ spectroscopy of the supernatants and calculated as percentage as well as distribution coefficient K d . Sorption starts from pH ∼6 and, under exclusion of CO 2 , increases continuously, while, in the presence of ambient air, it reaches a maximum at pH ∝8.5 (γ-Al 2 O 3 : logK d max ∼ 4 mL/g; STx-1: logK d max ∼ 2.7 mL/g). Beyond that it decreases again due to the formation of aqueous neptunium carbonate complexes. Furthermore, neptunium sorption on montmorillonite is influenced by ionic strength at pH <6 through ion exchange processes pointing towards the formation of outer-sphere surface complexes there. Isotherms measured at the sorption maximum showed the precipitation of presumably neptunium carbonate complexes above 3.10 -5 M under ambient air conditions. Additionally, they indicated progressive saturation of the sorption sites of γ-Al 2 O 3 . At selected pH (STx-1: 5.0, 7.0, 8.0, 8.5, 9.0, 9.5; γ-Al 2 O 3 : 8.5, 9.5) EXAFS samples were prepared as wet pastes with μM 237 Np and measured at room temperature in fluorescence mode at ANKA and ESRF. Several spectra were averaged and analysed with EXAFSPAK and FEFF 8.20 employing models of NaNpO 2 (CO 3 ) or soddyite, (UO 2 ) 2 SiO 4 .2(H 2 O). The shorter atomic distances of the neptunyl ion at pH 5 compared to the others hinted at the retention of the hydration shell and, thus, at outer-sphere sorption. On average the bond lengths for Np(V) sorbed on STx

  5. Nanomolar simultaneous determination of tryptophan and melatonin by a new ionic liquid carbon paste electrode modified with SnO{sub 2}-Co{sub 3}O{sub 4}@rGO nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Zeinali, Homa [Department of Chemistry, Payame Noor University, Qazvin (Iran, Islamic Republic of); Bagheri, Hasan, E-mail: h.bagheri82@gmail.com [Chemical Injuries Research Center, Baqiyatallah University of Medical Sciences, Tehran (Iran, Islamic Republic of); Monsef-Khoshhesab, Zahra [Department of Chemistry, Payame Noor University, Qazvin (Iran, Islamic Republic of); Khoshsafar, Hosein [Department of Internal Medicine, Zabol University of Medical Sciences, Zabol (Iran, Islamic Republic of); Hajian, Ali [Laboratory for Sensors, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges Köhler Allee 103, 79110 Freiburg (Germany)

    2017-02-01

    This work describes the development of a new sensor for simultaneous determination of tryptophan and melatonin. The proposed sensor was an ionic liquid carbon paste electrode modified with reduced graphene oxides decorated with SnO{sub 2}-Co{sub 3}O{sub 4} nanoparticles. The voltammetric oxidation of the analytes by the proposed sensor confirmed that the electrooxidation process undergoes a two-electron/one-proton reaction for melatonin and a two-electron/two-proton reaction for tryptophan in diffusion-controlled processes. Moreover, based on the excellent electrochemical properties of the modified electrode, a sensitive voltammetric method was used for individual and simultaneous determination of melatonin and tryptophan in the aqueous solutions. Under the optimized experimental conditions, a linear response obtained in the range of 0.02 to 6.00 μmol L{sup −1} with detection limits of 4.1 and 3.2 nmol L{sup −1} for melatonin and tryptophan, respectively. The prepared sensor possessed accurate and rapid response toward melatonin and tryptophan with a good sensitivity, selectivity, stability, and repeatability. Finally, the applicability of the proposed sensor was verified by evaluation of melatonin and tryptophan in various real samples including human serum and tablet samples. - Highlights: • Ionic liquid-SnO{sub 2}-Co{sub 3}O{sub 4}@rGO nanocomposite as electrode material • This modifier can promote the electrochemical properties of carbon paste electrode. • Determination of tryptophan and melatonin was investigated.

  6. Synthesis and characterization of carbon nanotubes synthesized over NiO/Na-montmorillonite catalyst and application to a hydrogen peroxide sensor

    International Nuclear Information System (INIS)

    Hsu, H.-L.; Jehng, J.-M.; Liu, Y.-C.

    2009-01-01

    In this study, we demonstrate the synthesis of carbon nanotubes (CNTs) on clay mineral layers, and the preparation of hydrogen peroxide (H 2 O 2 ) sensor based on CNT/Nafion/Na-montmorillonite (Clay) composite film for the detection of H 2 O 2 . The nickel oxide metallic catalyst (NiO) has been prepared by the polyol method and then dispersed onto the clay mineral layers. The CNTs were successfully synthesized over the NiO/Clay catalyst onto clay layers to form a three-dimensional CNT/Clay network by thermal chemical vapor deposition method. From field-emission scanning electron microscope images, the results of X-ray diffraction and Fourier transfer infrared spectra; the layered clay platelets are apparently delaminated and exfoliated after the growth of CNTs onto the surface of clay minerals. The mixed hybrid film of Nafion and CNT/Clay is coated on the glassy carbon electrode to detect hydrogen peroxide (H 2 O 2 ). This composite film performs a detection limit of 1.0 x 10 -4 M for H 2 O 2 and the current is linear for H 2 O 2 concentrations from 0.1 to 12.8 mM. Furthermore, the sensitivity of the GCE modified with the CNT/Clay/Nafion hybrid film to H 2 O 2 was calculated to be 1.71 x 10 5 μA M -1 cm -2 . Consequently, the CNT/Clay/Nafion medium can probably be a useful electrode for the development of sensors due to its high sensitivity and applicability

  7. PVC membrane, coated-wire, and carbon-paste ion-selective electrodes for potentiometric determination of galantamine hydrobromide in physiological fluids.

    Science.gov (United States)

    Abdel-Haleem, Fatehy M; Saad, Mohamed; Barhoum, Ahmed; Bechelany, Mikhael; Rizk, Mahmoud S

    2018-08-01

    We report on highly-sensitive ion-selective electrodes (ISEs) for potentiometric determining of galantamine hydrobromide (GB) in physiological fluids. Galantamine hydrobromide (GB) was selected for this study due to its previous medical importance for treating Alzheimer's disease. Three different types of ISEs were investigated: PVC membrane electrode (PVCE), carbon-paste electrode (CPE), and coated-wire electrode (CWE). In the construction of these electrodes, galantaminium-reineckate (GR) ion-pair was used as a sensing species for GB in solutions. The modified carbon-paste electrode (MCPE) was prepared using graphene oxide (MCPE-GO) and sodium tetrakis (trifluoromethyl) phenyl borate (MCPE-STFPB) as ion-exchanger. The potentiometric modified CPEs (MCPE-GO and MCPE-STFPB) show an improved performance in term of Nernstian slope, selectivity, response time, and response stability compared to the unmodified CPE. The prepared electrodes PVCE, CWE, CPE, MCPE-GO and MCPE-STFPB show Nernstian slopes of 59.9, 59.5, 58.1, 58.3 and 57.0 mV/conc. decade, and detection limits of 5.0 × 10 -6 , 6.3 × 10 -6 , 8.0 × 10 -6 , 6.0 × 10 -6 and 8.0 × 10 -6  mol L -1 , respectively. The prepared ISEs also show high selectivity against cations (i.e. Na + , K + , NH 4 + , Ca 2+ , Al 3+ , Fe 3+ ), amino acids (i.e. glycine, L-alanine alanine), and sugars (i.e. fructose, glucose, maltose, lactose). The prepared ISEs are applicable for determining GB in spiked serums, urines, and pharmaceutical preparations, using a standard addition and a direct potentiometric method. The fast response time (<10 s), long lifetime (1-5 weeks), reversibility and stability of the measured signals facilitate the application of these sensors for routine analysis of the real samples. Copyright © 2018 Elsevier B.V. All rights reserved.

  8. Electrochemical quantification of the thermodynamic equilibrium constant of the tenoxicam-β-cyclodextrin inclusion complex formed on the surface of a poly-β cyclodextrin-modified carbon paste electrode

    International Nuclear Information System (INIS)

    Guzmán-Hernández, D.S.; Palomar-Pardavé, M.; Rojas-Hernández, A.; Corona-Avendaño, S.; Romero-Romo, M.; Ramírez-Silva, M.T.

    2014-01-01

    Graphical abstract: - Highlights: • A carbon paste electrode (CPE) was modified with a β-CD polymer. • Tenoxicam oxidation on the CPE/poly-β-CD was adsorption controlled. • Influence of pH, scan rate, angular velocity and concentration was evaluated. • Fittings of i-E plots were done considering an irreversible surface reaction. • Electrochemical evaluation of the surface inclusion constant is presented. - Abstract: In this work it is shown that when a carbon paste electrode, CPE, is modified with a β-cyclodextrin polymer, the tenoxicam oxidation becomes an adsorption controlled process due to formation of a surface inclusion complex with the β-CD molecules comprising the surface of the polymer. It was found that such surface inclusion complex can be formed independently of the tenoxicam predominant species, Tenox’, in the aqueous solution namely: H 2 Tenox + , HTenox or Tenox − , depending on the solution pH. The electrochemical quantification of the thermodynamic constant of the equilibrium Tenox’ + β-CD (polymer) = Tenox’-β-CD (polymer) was estimated as log K incl. = 4.26 ± 0.01. Furthermore, from the analyses of the experimental voltammograms according with Laviron's equation for an irreversible surface reaction [E. Laviron, J. Electroanal. Chem. 52 (1974) 355-393] it is shown that the surface concentration, Γ R , of tenoxicam increases as its concentration in solution does, reaching a maximum value of 1.51 × 10 −10 mol cm −2 at 64 μM

  9. A quantitative mechanistic description of Ni, Zn and Ca sorption on Na-Montmorillonite. Part I: Physico-chemical characterisation and titration measurements

    International Nuclear Information System (INIS)

    Baeyens, B.; Bradbury, M.H.

    1995-07-01

    The work presented in this report is primarily concerned with characterisation studies and titration measurements on conditioned Na-montmorillonite. The starting material, SWy-1 Na-montmorillonite (Crook County, Wyoming, USA), contains background metal impurities, soluble salts and sparingly soluble minerals which can influence titration and sorption measurements and thereby lead to difficulties in the interpretation of the data. A conditioning procedure is described which yielded a purified clay material in the homoionic sodium form with a particle size 4 . The reasons for choosing a batch method, coupled with back titration of the supernatant solutions, instead of a continuous procedure, are fully discussed. Chemical analyses data for the supernatant solutions are presented in detail. The influence of background impurities, not removed by the conditioning, and cation exchange processes on the form of the titration curves were investigates. Net Na-montmorillonite titration curves at two different ionic strengths were derived which are considered to reflect only the acid/base behaviour of ≡SOH type surface sites. The acid end point in the titration data was used to estimate an ≡SOH site capacity of 0.08 moles per kg conditioned Na-montmorillonite. (author) 8 figs., 19 tabs., refs

  10. Enrichment and stripping voltametric behavior of technetium traces at a carbon paste electrode modified with TTA

    International Nuclear Information System (INIS)

    Dick, R.; Ruf, H.; Ache, H.J.

    1988-06-01

    The possibility of enrichment as well as the stripping voltammetric behavior of technetium traces at a carbon paste electrode modified with thenoyltrifluoroacetone (TTA) was studied. Accumulation of Tc(IV) on the electrode surface occurs without application of a deposition voltage due to complex formation with TTA, probably resulting Tc(TTA) 4 . During the following cathodic potential scan made with the differential pulse mode a characteristic current peak is obtained at -40 mV (vs. Ag/AgCl) which increases with Tc concentration and deposition time. However, Tc(IV) gives much more sensitive stripping current signals if a reductive deposition potential of -0.4 V is applied, presumably on account of the formation of Tc(TTA) 3 . In this case an anodic voltammetric scan was applied resulting a stripping peak at about +30 mV, the height of which is related to the concentration of Tc in solution as well as to the time of deposition. Calibration graphs revealed good reproducibility for analytical application. The lower detection limit for Tc(IV) achieved for 1 M sodium chloride solutions 4.6 x 10 -9 M. Tc(VII) is not enriched in the absence of reduction which takes place only from about -0.6 V on with the pH optimally set at 3.5. Therefore it is basically possible to discriminate Tc(IV) from Tc(VII). (orig.) [de

  11. Fast and simultaneous determination of Pb2+ and Cu2+ in water samples using a solid paraffin-based carbon paste electrode chemically modified with 2-aminothiazole-silica-gel

    OpenAIRE

    Silva, Daiane H; Costa, Dayane A; Takeuchi, Regina M; Santos, André L

    2011-01-01

    A solid paraffin-based carbon paste electrode modified with 2-aminothiazole functionalized silica-gel was used for simultaneous quantification of Pb2+ and Cu2+ in water samples by anodic stripping voltammetry. The present method uses short preconcentration time (180 s), which allowed reliable and simultaneous quantification of Pb2+ and Cu2+ in a very fast way. Detection limits of 7.3 and 90 nmol L-1 were obtained for Pb2+ and Cu2+, respectively. These values are below their maximum concentrat...

  12. Poly(dimethylsiloxane) cross-linked carbon paste electrodes for microfluidic electrochemical sensing.

    Science.gov (United States)

    Sameenoi, Yupaporn; Mensack, Meghan M; Boonsong, Kanokporn; Ewing, Rebecca; Dungchai, Wijitar; Chailapakul, Orawan; Cropek, Donald M; Henry, Charles S

    2011-08-07

    Recently, the development of electrochemical biosensors as part of microfluidic devices has garnered a great deal of attention because of the small instrument size and portability afforded by the integration of electrochemistry in microfluidic systems. Electrode fabrication, however, has proven to be a major obstacle in the field. Here, an alternative method to create integrated, low cost, robust, patternable carbon paste electrodes (CPEs) for microfluidic devices is presented. The new CPEs are composed of graphite powder and a binder consisting of a mixture of poly(dimethylsiloxane) (PDMS) and mineral oil. The electrodes are made by filling channels molded in previously cross-linked PDMS using a method analogous to screen printing. The optimal binder composition was investigated to obtain electrodes that were physically robust and performed well electrochemically. After studying the basic electrochemistry, the PDMS-oil CPEs were modified with multi-walled carbon nanotubes (MWCNT) and cobalt phthalocyanine (CoPC) for the detection of catecholamines and thiols, respectively, to demonstrate the ease of electrode chemical modification. Significant improvement of analyte signal detection was observed from both types of modified CPEs. A nearly 2-fold improvement in the electrochemical signal for 100 μM dithiothreitol (DTT) was observed when using a CoPC modified electrode (4.0 ± 0.2 nA (n = 3) versus 2.5 ± 0.2 nA (n = 3)). The improvement in signal was even more pronounced when looking at catecholamines, namely dopamine, using MWCNT modified CPEs. In this case, an order of magnitude improvement in limit of detection was observed for dopamine when using the MWCNT modified CPEs (50 nM versus 500 nM). CoPC modified CPEs were successfully used to detect thiols in red blood cell lysate while MWCNT modified CPEs were used to monitor temporal changes in catecholamine release from PC12 cells following stimulation with potassium.

  13. Initial reaction between CaO and SO2 under carbonating and non-carbonating conditions

    DEFF Research Database (Denmark)

    Rasmussen, Martin Hagsted; Wedel, Stig; Pedersen, Kim H.

    2015-01-01

    The initial kinetics of the CaO/SO2 reaction have been investigated for reaction times shorter than 1s and in the temperature interval between 450 and 600°C under both carbonating and non-carbonating conditions (0-20 vol% CO2) to clarify how recirculating CaO influences the emission of SO2 from...... showed that the CaO conversion with respect to SO2 declined when the CO2 concentration was increased. Under all conditions, larger specific surface areas of CaO gave higher reaction rates with SO2. Higher temperatures had a positive effect on the reaction between SO2 and CaO under non......-carbonating conditions, but no or even a negative effect under carbonating conditions. The results led to the conclusion that SO2 released from raw meal in the upper stages of the preheater does not to any significant extent react with CaO recirculating in the preheater tower....

  14. Ice nucleation of ammonia gas exposed montmorillonite mineral dust particles

    Directory of Open Access Journals (Sweden)

    A. Salam

    2007-07-01

    Full Text Available The ice nucleation characteristics of montmorillonite mineral dust aerosols with and without exposure to ammonia gas were measured at different atmospheric temperatures and relative humidities with a continuous flow diffusion chamber. The montmorillonite particles were exposed to pure (100% and diluted ammonia gas (25 ppm at room temperature in a stainless steel chamber. There was no significant change in the mineral dust particle size distribution due to the ammonia gas exposure. 100% pure ammonia gas exposure enhanced the ice nucleating fraction of montmorillonite mineral dust particles 3 to 8 times at 90% relative humidity with respect to water (RHw and 5 to 8 times at 100% RHw for 120 min exposure time compared to unexposed montmorillonite within our experimental conditions. The percentages of active ice nuclei were 2 to 8 times higher at 90% RHw and 2 to 7 times higher at 100% RHw in 25 ppm ammonia exposed montmorillonite compared to unexposed montmorillonite. All montmorillonite particles are more efficient as ice nuclei with increasing relative humidities and decreasing temperatures. The activation temperature of montmorillonite exposed to 100% pure ammonia was 15°C higher than for unexposed montmorillonite particles at 90% RHw. In the 25 ppm ammonia exposed montmorillonite experiments, the activation temperature was 10°C warmer than unexposed montmorillonite at 90% RHw. Degassing does not reverse the ice nucleating ability of ammonia exposed montmorillonite mineral dust particles suggesting that the ammonia is chemically bound to the montmorillonite particle. This is the first experimental evidence that ammonia gas exposed montmorillonite mineral dust particles can enhance its activation as ice nuclei and that the activation can occur at temperatures warmer than –10°C where natural atmospheric ice nuclei are very scarce.

  15. Preparation and Evaluation of Acetabularia-Modified Carbon Paste Electrode in Anodic Stripping Voltammetry of Copper and Lead Ions

    Directory of Open Access Journals (Sweden)

    Muhammad Raziq Rahimi Kooh

    2013-01-01

    Full Text Available Seaweed is well known about for potential in chelating heavy metals. In this study, carbon paste electrodes were fabricated with siphonous seaweed Acetabularia acetabulum as the modifiers to sense lead (II and copper (II by square-wave anodic stripping voltammetry. Various scan rates and deposition potentials were measured to obtain the optimal peak current for Pb(II and Cu(II. Optimum conditions of Acetabularia-CPE for sensing Pb(II were at the scan rate of 75 mV/s and deposition potential of −800 mV, while for Cu(II sensing were at 100 mV/s and −300 mV, respectively. The electrodes were characterized by the duration of accumulation time, preconcentration over a range of standards, supporting electrolyte, and standard solutions of various pH values. Interference studies were carried out. Both Zn(II and Cu(II were found to interfere with Pb(II sensing, whereas only Zn(II causes interference with Cu(II sensing. The electrode was found to have good regeneration ability via electrochemical cleaning. Preliminary testing of complex samples such as NPK fertilisers, black soil, and sea salt samples was included.

  16. Electroanalytical Determination of Gemifloxacin Mesylate in Bulk, Tablets and Human Urine Using Gold Nanoparticles Modified Carbon Paste Electrode

    Directory of Open Access Journals (Sweden)

    Ali Attia

    2014-12-01

    Full Text Available A simple, precise, inexpensive and sensitive voltammetric method has been developed for the determination of gemifloxacin mesylate (GEM in the presence of tween 80 in the bulk, farmaceutical dosage forms and human urine at gold nanoparticles modified carbon paste electrode (GNCPE. The electrochemical behavior of GEM has been investigated by using cyclic voltammetry (CV and differential pulse voltammetry (DPV techniques. The electrochemical oxidation of GEM was an irreversible process which exhibited adsorption-diffusion controlled process behavior in Britton-Robinson (BR buffer over the entire pH range of values from 2 to 9. The adsorptive stripping response was evaluated as a function of some variables such as pH, type of surfactant, scan rate and accumulation time. The anodic peak current varied linearly over the range from 8.0 × 10-7 to 2.8 × 10-5 M. The limits of detection and quantification were 7.32 × 10-8 M and 2.44 × 10-7 M, respectively. The relative standard deviations and the percentage recoveries were found in the following ranges: 0.58-1.35% and 99.37-101.76%, respectively.

  17. Fabrication and Characterization of Cellulose Acetate/Montmorillonite Composite Nanofibers by Electrospinning

    Directory of Open Access Journals (Sweden)

    Se Wook Kim

    2015-01-01

    Full Text Available Nanofibers composed of cellulose acetate (CA and montmorillonite (MMT were prepared by electrospinning method. MMT was first dispersed in water and mixed with an acetic acid solution of CA. The viscosity and conductivity of the CA/MMT solutions with different MMT contents were measured to compare with those of the CA solution. The CA/MMT solutions were electrospun to fabricate the CA/MMT composite nanofibers. The morphology, thermal stability, and crystalline and mechanical properties of the composite nanofibers were characterized by scanning electron microscopy (SEM, transmission electron microscopy (TEM, energy dispersive X-ray spectroscopy (EDX, thermogravimetric analysis (TGA, X-ray diffraction (XRD, and tensile test. The average diameters of the CA/MMT composite nanofibers obtained by electrospinning 18 wt% CA/MMT solutions in a mixed acetic acid/water (75/25, w/w solvent ranged from 150~350 nm. The nanofiber diameter decreased with increasing MMT content. TEM indicated the coexistence of CA nanofibers. The CA/MMT composite nanofibers showed improved tensile strength compared to the CA nanofiber due to the physical protective barriers of the silicate clay layers. MMT could be incorporated into the CA nanofibers resulting in about 400% improvement in tensile strength for the CA sample containing 5 wt% MMT.

  18. Nanocomposites of polyamide 6/residual monomer with organic-modified montmorillonite and their nanofibers produced by electrospinning

    Directory of Open Access Journals (Sweden)

    Cesar Augusto Gonçalves Beatrice

    2012-08-01

    Full Text Available Nanocomposites of an organic-modified montmorillonite (MMT and polyamide 6 (PA6 with a residual monomer were produced by melt mixing in a torque rheometer. By wide angle X-rays diffraction (WAXD, intercalated/exfoliated structures were observed in the PA6/MMT nanocomposites with 3 and 5 wt. (% of MMT; on the other hand, when 7 wt. (% of MMT was added, a nanocomposite with exfoliated structures was obtained due to the predominant linking reactions between the residual monomer and the "nanoclays" organic surfactant. Solutions of these PA6/MMT nanocomposites at 15, 17 and 20 wt. (% in formic acid were prepared. The 3 and 5 wt. (% nanocomposites were successfully electrospun; however, electrospinning of the 7 wt. (% nanocomposite was not possible. WAXD, scanning and transmission electron microscopy results showed that the 3 and 5 wt. (% nanofibers with average diameter between 80-250 nm had exfoliated structures. These results indicate that the high elongational forces developed during the electrospinning process changed the initial intercalated/exfoliated structure of the nanocomposites to an exfoliated one.

  19. Selective removal and inactivation of bacteria by nanoparticle composites prepared by surface modification of montmorillonite with quaternary ammonium compounds.

    Science.gov (United States)

    Khalil, Rowaida K S

    2013-10-01

    The purpose of the present study was to prepare new nanocomposites with antibacterial activities by surface modification of montmorillonite using quaternary ammonium compounds that are widely applied as disinfectants and antiseptics in food-processing environments. The intercalation of four quaternary ammonium compounds namely benzalkonium chloride, cetylpyridinium chloride monohydrate, hexadecyltrimethylammonium bromide, tetraethylammonium chloride hydrate into montmorillonite layers was confirmed by X-ray diffraction. The antibacterial influences of the modified clay variants against important foodborne pathogens differed based on modifiers quantities, microbial cell densities, and length of contact. Elution experiments through 0.1 g of the studied montmorillonite variants indicated that Staphylococcus aureus, Pseudomonas aeroginosa, and Listeria monocytogenes were the most sensitive strains. 1 g of hexadecyltrimethylammonium bromide intercalated montmorillonites demonstrated maximum inactivation of L. monocytogenes populations, with 4.5 log c.f.u./ml units of reduction. In adsorption experiments, 0.1 g of tetraethylammonium chloride hydrate montmorillonite variants significantly reduced the growth of Escherichia coli O157:H7, L. monocytogenes, and S. aureus populations by 5.77, 6.33, and 7.38 log units respectively. Growth of wide variety of microorganisms was strongly inhibited to undetectable levels (benzalkonium chloride montmorillonite variants. This investigation highlights that reduction in counts of microbial populations adsorbed to the new nanocomposites was substantially different from that in elution experiments, where interactions of nanocomposites with bacteria were specific and more complex than simple ability to inactivate. Treatment columns packed with modified variants maintained their inactivation capacity to the growth of Salmonella Tennessee and S. aureus populations after 48 h of incubation at room temperature with maximum reductions

  20. Thermodynamic of hydration of a Wyoming montmorillonite saturated with Ca, Mg, Na and K

    International Nuclear Information System (INIS)

    Vieillard, P.; Blanc, P.; Gailhanou, H.; Gaboreau, S.; Giffaut, E.

    2010-01-01

    enthalpy of immersion, and isotherms of adsorption - desorption has been done for Wyoming montmorillonite saturated by Mg 2+ , Ca 2+ , Na + and K + . Smectite water-vapor pressure isotherms represent the total concentration of H 2 O taken up the sample which is distributed among the interlayers, the outer surfaces of particles and the open pore space in the sample. In order to retrieve standard state thermodynamic properties for smectite hydration and dehydration from such data, the amount of H 2 O in excess of that in the interlayer must be assessed and subtracted from the total amount taken up by the clay sample. Berend et al. (1995), Cases et al. (1992, 1997) provide careful measurements of recovering waters in both processes (hydration and dehydration) on Wyoming saturated by monovalent and divalent cations. Despite the fact that neither the hydration, nor the dehydration isotherm necessarily represents the equilibrium state of the system, the two isotherms together can be considered to bracket the equilibrium values of Xhs and the activity of H 2 O. Paired hydration and dehydration isotherm in the one hand and enthalpy of immersion in the other hand, which constitute the limits of these brackets can be regressed to assess standard state thermodynamic parameters (enthalpy and entropy) for the hydration- dehydration process. Experimental enthalpies of hydration are used in the determination of ΔH deg. hyd. W H1 and W H2 by the minimization technique. For the adsorption-desorption isotherms, the determination of parameters ΔS deg. hyd. W S1 and W S2 are obtained by minimizing the difference between measured sets of data (relative humidity and number of adsorbed interlayer water) and calculated ones. For each Wyoming saturated with one cation, six parameters are requested and characterize the standard state thermodynamic properties of hydration between smectite and interlayer H 2 O. Relations between hydration parameters ΔH deg. hyd. and ΔS deg. hyd. in the one hand

  1. Neutron Time-of-Flight Quantification of Water Desorption Isotherms of Montmorillonite

    DEFF Research Database (Denmark)

    Gates, Will P.; Bordallo, Heloisa N.; Aldridge, Laurence P.

    2012-01-01

    enabled us to differentiate at least two water motions during dehydration of Ca- and Na-SAz-1 (initially equilibrated at RH = 55%) by using a "controlled water loss" time-of-flight procedure. This work confirms that (a) interlayer and cationic water in dioctahedral smectites are characterized by slower...... motions than interparticle water, (b) interlayer cations influenced the dynamics of water loss, probably through its affect on clay fabric, and (c) interparticle water behaves more like bulk water. At 55% RH the Ca montmorillonite held more interparticle water, but on dehydration under controlled......The multiple energy states of water held by surfaces of a clay mineral can be effectively probed with time-of-flight and fixed elastic window neutron scattering. We used these techniques to quantitatively differentiate water types, including rotational and translational diffusions, in Ca- and Na...

  2. Carboxymethyl starch/montmorillonite composite microparticles: Properties and controlled release of isoproturon.

    Science.gov (United States)

    Wilpiszewska, Katarzyna; Spychaj, Tadeusz; Paździoch, Waldemar

    2016-01-20

    Preparation of novel high substituted carboxymethyl starch-based microparticles containing sodium montmorillonite (MMT) by crosslinking with Al(3+) was described. For preparing nanocomposite granules carboxymethyl starch (CMS) from native potato starch as well as CMS from amylopectin has been used. The hydrophilic CMS/MMT composite systems were used for herbicide, i.e. isoproturon encapsulation (ca. 75% encapsulation efficiency). The herbicide release rate from CMS/MMT composites in water was significantly reduced when compared to commercial isoproturon: 95% released after ca. 700 h and ca. 24h, respectively. Leaching in soil from composite systems was relatively slower than release in water. After a series of eight irrigations leached about 10% of isoproturon loaded. The CMS/MMT carriers could reduce the potential leaching of herbicide and beneficially reduce pollution of the environment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. Development of carbon nanotube modified cement paste with microencapsulated phase-change material for structural-functional integrated application.

    Science.gov (United States)

    Cui, Hongzhi; Yang, Shuqing; Memon, Shazim Ali

    2015-04-10

    Microencapsulated phase-change materials (MPCM) can be used to develop a structural-functional integrated cement paste having high heat storage efficiency and suitable mechanical strength. However, the incorporation of MPCM has been found to degrade the mechanical properties of cement based composites. Therefore, in this research, the effect of carbon nanotubes (CNTs) on the properties of MPCM cement paste was evaluated. Test results showed that the incorporation of CNTs in MPCM cement paste accelerated the cement hydration reaction. SEM micrograph showed that CNTs were tightly attached to the cement hydration products. At the age of 28 days, the percentage increase in flexural and compressive strength with different dosage of CNTs was found to be up to 41% and 5% respectively. The optimum dosage of CNTs incorporated in MPCM cement paste was found to be 0.5 wt %. From the thermal performance test, it was found that the cement paste panels incorporated with different percentages of MPCM reduced the temperature measured at the center of the room by up to 4.6 °C. Inverse relationship was found between maximum temperature measured at the center of the room and the dosage of MPCM.

  4. Development of Carbon Nanotube Modified Cement Paste with Microencapsulated Phase-Change Material for Structural–Functional Integrated Application

    Directory of Open Access Journals (Sweden)

    Hongzhi Cui

    2015-04-01

    Full Text Available Microencapsulated phase-change materials (MPCM can be used to develop a structural–functional integrated cement paste having high heat storage efficiency and suitable mechanical strength. However, the incorporation of MPCM has been found to degrade the mechanical properties of cement based composites. Therefore, in this research, the effect of carbon nanotubes (CNTs on the properties of MPCM cement paste was evaluated. Test results showed that the incorporation of CNTs in MPCM cement paste accelerated the cement hydration reaction. SEM micrograph showed that CNTs were tightly attached to the cement hydration products. At the age of 28 days, the percentage increase in flexural and compressive strength with different dosage of CNTs was found to be up to 41% and 5% respectively. The optimum dosage of CNTs incorporated in MPCM cement paste was found to be 0.5 wt %. From the thermal performance test, it was found that the cement paste panels incorporated with different percentages of MPCM reduced the temperature measured at the center of the room by up to 4.6 °C. Inverse relationship was found between maximum temperature measured at the center of the room and the dosage of MPCM.

  5. Electrochemical characterisation of novel screen-printed carbon paste electrodes for voltammetric measurements

    Directory of Open Access Journals (Sweden)

    Sýs Milan

    2017-01-01

    Full Text Available This work is focused on the homemade screen-printed carbon paste electrode containing basically graphite powder (or glassy carbon powder, poly(vinylbchloride (PVC and paraffin oil. It compares the electrochemical properties of conventional carbon-based electrodes and prepared screen-printed carbon paste electrodes towards [Fe(CN6]3-/[Fe(CN6]4- and quinone/hydroquinone redox couples. Significant attention is paid to the development of the corresponding carbon inks, printing and the surface characterisation of the resulting electrodes by the scanning electron microscopy. An optimization consisted of the selection of the organic solvent, the optimal content of the used polymer with the chosen paste binder, appropriate isolation of electric contact, etc. Very similar properties of the prepared screen-printed electrodes, containing only corresponding carbon powder and 3 % PVC, with their conventional carbon paste electrode and glassy carbon-based electrodes, were observed during their characterisation. Screen-printed electrodes, with the pasting liquid usually provided satisfactory analytical data. Moreover, they can be used in the flow injection analysis and could undoubtedly replace the carbon paste grooved electrodes. It can be assumed that certain progress in the development of electrode materials was achieved by this research.

  6. Molecular simulation of the role of interlayer water on the mechanical properties of montmorillonite

    International Nuclear Information System (INIS)

    Carrier, Benoit; Vandamme, Matthieu; Ebrahimi, Davoud; Whittle, Andrew J.; Pellenq, Roland J.M.; Van Damme, Henri

    2012-01-01

    Document available in extended abstract form only. Full text of publication follows: Montmorillonite - a swelling clay - is the main component of the clay fraction of the Callovo-Oxfordian argillite, which is considered as a possible host rock for radioactive waste disposal, and of the sealing bentonite plugs of storage tunnels. Montmorillonite layers have a great ability to adsorb water, resulting in the swelling of the clay. Montmorillonite consists of water molecules and sodium or calcium cations between negatively charged layers. Both the water content of the interlayer space and the nature of the charge-balancing cations are expected to have an effect on the mechanical properties of the clay layer. Computer simulations allow to reproduce the experimental swelling isotherms of the layers and to gain a deeper understanding of the physical mechanisms of the swelling process. They show how water is organized in discrete layers and how this process depends on the type of inter-layer cation. However, the effect of the swelling on the mechanical properties of the nano-scale have not been fully investigated. The objective of this work is to compute the elastic properties of a Na + - Montmorillonite and a Ca 2+ -Montmorillonite versus relative humidity at 300 K. The results of this work is the first step to build a macroscopic state equation of unsaturated clay-based materials. We use a simulation cell containing two Montmorillonite layers and sodium or calcium counterions. The partial charges of the atoms and the interatomic interaction parameters are given by the CLAYFF force field. Grand Canonical Monte-Carlo simulations are used to compute the adsorption/desorption isotherm. Each equilibrium configuration is then strained in all directions of space. Then, we perform Molecular Dynamics and compute the stress tensor and all the components of the elasticity tensor. We present the evolution of the elastic properties of the clay layers with the relative humidity. In

  7. Origin of enhanced Brønsted acidity of NiF-modified synthetic mica-montmorillonite clay

    NARCIS (Netherlands)

    Liu, Chong; Pidko, Evgeny A.; Hensen, Emiel J.M.

    2018-01-01

    The Brønsted acidity of synthetic mica-montmorillonite (SMM) clay was studied by periodic DFT calculations. Different structural models were compared to determine the Brønsted acidity of protons of the SMM clay based on (i) isomorphous substitution of Si4+ by Al3+ in the tetrahedral silicate layer

  8. Stable isotopes of pedogenic carbonates from the Somma-Vesuvius area, southern Italy, over the past 18 kyr: palaeoclimatic implications

    Science.gov (United States)

    Zanchetta, G.; di Vito, M.; Fallick, A. E.; Sulpizio, R.

    2000-12-01

    Stable isotopes were measured in the carbonate and organic matter of palaeosols in the Somma-Vesuvius area, southern Italy in order to test whether they are suitable proxy records for climatic and ecological changes in this area during the past 18000 yr. The ages of the soils span from ca. 18 to ca. 3 kyr BP. Surprisingly, the Last Glacial to Holocene climate transition was not accompanied by significant change in 18O of pedogenic carbonate. This could be explained by changes in evaporation rate and in isotope fractionation between water and precipitated carbonate with temperature, which counterbalanced the expected change in isotope composition of meteoric water. Because of the rise in temperature and humidity and the progressive increase in tree cover during the Holocene, the Holocene soil carbonates closely reflect the isotopic composition of meteoric water. A cooling of about 2°C after the Avellino eruption (3.8 ka) accounts for a sudden decrease of about 1 in 18O of pedogenic carbonate recorded after this eruption. The 13C values of organic matter and pedogenic carbonate covary, indicating an effective isotope equilibrium between the organic matter, as the source of CO2, and the pedogenic carbonate. Carbon isotopes suggest prevailing C3 vegetation and negligible mixing with volcanogenic or atmospheric CO2.

  9. Origin of enhanced Brønsted acidity of NiF-modified synthetic mica-montmorillonite clay

    NARCIS (Netherlands)

    Liu, C.; Pidko, E.A.; Hensen, Emiel J M

    2018-01-01

    The Brønsted acidity of synthetic mica-montmorillonite (SMM) clay was studied by periodic DFT calculations. Different structural models were compared to determine the Brønsted acidity of protons of the SMM clay based on (i) isomorphous substitution of Si4+ by Al3+ in the

  10. A voltammetric sensor based on NiO/CNTs ionic liquid carbon paste electrode for determination of morphine in the presence of diclofenac

    International Nuclear Information System (INIS)

    Sanati, Afsaneh L.; Karimi-Maleh, Hassan; Badiei, Alireza; Biparva, Pourya; Ensafi, Ali A.

    2014-01-01

    A novel ionic liquid modified NiO/CNTs carbon paste electrode (IL/NiO/CNTCPE) had been fabricated by using hydrophilic ionic liquid 1-methyl-3-butylimidazolium chloride [MBIDZ]Cl as a binder. The cyclic voltammogram showed an irreversible oxidation peak at 0.61 V (vs. Ag/AgCl sat ), which corresponded to the oxidation of morphine. Compared to common carbon paste electrode, the electrochemical response was greatly improved for morphine electrooxidation. This modified electrode exhibited a potent and persistent electron mediating behavior followed by well separated oxidation peaks of morphine and diclofenac. Detection limit of morphine was found to be 0.01 μM using square wave voltammetry (SWV) method. The proposed sensor was successfully applied for the determination of morphine in human urine and pharmaceutical samples. - Graphical abstract: Diclofenac as a nonsteroidal anti-inflammatory drug has been shown to decrease morphine consumption after operation in adults. The addition of regular doses of diclofenac may reduce the need for morphine after abdominal surgery. Therefore, in this study we describe a sensitive electrochemical sensor for simultaneous determination of morphine and diclofenac. - Highlights: • Electrochemical behavior of morphine study using modified carbon paste electrode • The sensor resolved the overlap of morphine and diclofenac • This sensor is also used for the determination of morphine in real samples

  11. A voltammetric sensor based on NiO/CNTs ionic liquid carbon paste electrode for determination of morphine in the presence of diclofenac

    Energy Technology Data Exchange (ETDEWEB)

    Sanati, Afsaneh L. [Department of Chemistry, Graduate University of Advanced Technology, Kerman (Iran, Islamic Republic of); Karimi-Maleh, Hassan, E-mail: h.karimi.maleh@gmail.com [Department of Chemistry, Graduate University of Advanced Technology, Kerman (Iran, Islamic Republic of); Badiei, Alireza [School of Chemistry, College of Science, University of Tehran, Tehran (Iran, Islamic Republic of); Biparva, Pourya [Department of Basic Sciences, Sari Agricultural Sciences and Natural Resources University, Sari (Iran, Islamic Republic of); Ensafi, Ali A. [Department of Chemistry, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2014-02-01

    A novel ionic liquid modified NiO/CNTs carbon paste electrode (IL/NiO/CNTCPE) had been fabricated by using hydrophilic ionic liquid 1-methyl-3-butylimidazolium chloride [MBIDZ]Cl as a binder. The cyclic voltammogram showed an irreversible oxidation peak at 0.61 V (vs. Ag/AgCl{sub sat}), which corresponded to the oxidation of morphine. Compared to common carbon paste electrode, the electrochemical response was greatly improved for morphine electrooxidation. This modified electrode exhibited a potent and persistent electron mediating behavior followed by well separated oxidation peaks of morphine and diclofenac. Detection limit of morphine was found to be 0.01 μM using square wave voltammetry (SWV) method. The proposed sensor was successfully applied for the determination of morphine in human urine and pharmaceutical samples. - Graphical abstract: Diclofenac as a nonsteroidal anti-inflammatory drug has been shown to decrease morphine consumption after operation in adults. The addition of regular doses of diclofenac may reduce the need for morphine after abdominal surgery. Therefore, in this study we describe a sensitive electrochemical sensor for simultaneous determination of morphine and diclofenac. - Highlights: • Electrochemical behavior of morphine study using modified carbon paste electrode • The sensor resolved the overlap of morphine and diclofenac • This sensor is also used for the determination of morphine in real samples.

  12. Removal of remazol yellow with modified clays with iron; Remocion de amarillo remazol con arcillas modificadas con hierro

    Energy Technology Data Exchange (ETDEWEB)

    Diaz-Gomez T, A. P.

    2012-07-01

    Clays have the ability to absorb water and to retain in its structure both hydrophilic and hydrophobic substances, therefore, it is possible to use them in the sorption of dyes from waste water, in order to avoid affecting water bodies or storm drains when they are discharged. In this paper the montmorillonite KSF and a sodium bentonite from the Morelos State, Mexico were studied for the sorption of an azo dye used in textiles knows as remazol yellow. These clays were modified with iron, the dye sorption behaviors and their regeneration processes for their reuse were determined. It was difficult to separate the sodium bentonite after being in contact with aqueous solutions; therefore it was nor a candidate dor the removal of remazol yellow from aqueous solutions. The montmorillonite KSF was characterized before and after the iron modification, and after its regeneration by scanning electron microscopy (elemental analysis), infrared spectrometry, X-ray diffraction, and the specific areas of the materials were determined by Bet analysis. The adsorption equilibrium time and the adsorption rate for remazol yellow were determined from the fitting of the experimental results to mathematical models for the unmodified and iron modified montmorillonite KSF. The adsorption capacity was determined from the adsorption isotherms and mathematical models. The influence of the ph in the sorption processes was determined as well, and it was found that, ph values between 2 and 12 do not have any influence on the adsorption processes for iron modified montmorillonite KSF. The montmorillonite KSF and the iron modified montmorillonite KSF are adequate adsorbents for the removal of remazol yellow from aqueous solutions. Although, the sorption capacity for the unmodified montmorillonite KSF is higher (about 10%) than the capacity for the iron modified montmorillonite KSF and the stability of the last one increased. The saturated clays with remazol yellow were treated with Fenton reactive

  13. Determination of dopamine in presence of ascorbic acid and uric acid using poly (Spands Reagent) modified carbon paste electrode

    Energy Technology Data Exchange (ETDEWEB)

    Veera Manohara Reddy, Y.; Prabhakara Rao, V.; Vijaya Bhaskar Reddy, A.; Lavanya, M.; Venu, M.; Lavanya, M.; Madhavi, G., E-mail: gmchem01@gmail.com

    2015-12-01

    In this paper, we have fabricated a modified carbon paste electrode (CPE) by electropolymerisation of spands reagent (SR) onto surface of CPE using cyclic voltammetry (CV). The developed electrode was abbreviated as poly(SR)/CPE and the surface morphology of the modified electrode was studied by using scanning electron microscopy (SEM). The developed electrode showed higher electrocatalytic properties towards the detection of dopamine (DA) in 0.1 M phosphate buffer solution (PBS) at pH 7.0. The effect of pH, scan rate, accumulation time and concentration of dopamine was studied at poly(SR)/CPE. The poly(SR)/CPE was successfully used as a sensor for the selective determination of DA in presence of ascorbic acid (AA) and uric acid (UA) without any interference. The poly(SR)/CPE showed a good detection limit of 0.7 μM over the linear dynamic range of 1.6 μM to 16 μM, which is extremely lower than the reported methods. The prepared poly(SR)/CPE exhibited good stability, high sensitivity, better reproducibility, low detection limit towards the determination of DA. The developed method was also applied for the determination of DA in real samples. - Highlights: • Electropolymerization of spands reagent was fabricated by cyclic voltammetry • The Poly (spands reagent) electrode shows excellent electrocatalytic activity for the detection of dopamine. • The detection limit for dopamine was found to be 0.7 μM. • The proposed method can be applied for DA in injection and human blood serum samples.

  14. Aflatoxin Toxicity Reduction in Feed by Enhanced Binding to Surface-Modified Clay Additives

    Science.gov (United States)

    Jaynes, William F.; Zartman, Richard E.

    2011-01-01

    Animal feeding studies have demonstrated that clay additives, such as bentonites, can bind aflatoxins in ingested feed and reduce or eliminate the toxicity. Bentonite deposits are found throughout the world and mostly consist of expandable smectite minerals, such as montmorillonite. The surfaces of smectite minerals can be treated with organic compounds to create surface-modified clays that more readily bind some contaminants than the untreated clay. Montmorillonites treated with organic cations, such as hexadecyltrimethylammonium (HDTMA) and phenyltrimethylammonium (PTMA), more effectively remove organic contaminants, such as benzene and toluene, from water than untreated clay. Similarly, montmorillonite treated with PTMA (Kd = 24,100) retained more aflatoxin B1 (AfB1) from aqueous corn flour than untreated montmorillonite (Kd = 944). Feed additives that reduced aflatoxin toxicity in animal feeding studies adsorbed more AfB1 from aqueous corn flour than feed additives that were less effective. The organic cations HDTMA and PTMA are considered toxic and would not be suitable for clay additives used in feed or food, but other non-toxic or nutrient compounds can be used to prepare surface-modified clays. Montmorillonite (SWy) treated with choline (Kd = 13,800) and carnitine (Kd = 3960) adsorbed much more AfB1 from aqueous corn flour than the untreated clay (Kd = 944). A choline-treated clay prepared from a reduced-charge, high-charge montmorillonite (Kd = 20,100) adsorbed more AfB1 than the choline-treated high-charge montmorillonite (Kd = 1340) or the untreated montmorillonite (Kd = 293). Surface-modified clay additives prepared using low-charge smectites and nutrient or non-toxic organic compounds might be used to more effectively bind aflatoxins in contaminated feed or food and prevent toxicity. PMID:22069725

  15. Direct electrochemistry and electrocatalysis of myoglobin using an ionic liquid-modified carbon paste electrode coated with Co3O4 nanorods and gold nanoparticles

    International Nuclear Information System (INIS)

    Wang, Xiaofeng; You, Zheng; Sha, Hailiang; Gong, Shixing; Niu, Qingjuan; Sun, Wei

    2014-01-01

    A nanohybrid biomaterial was fabricated by mixing Co 3 O 4 nanorods, gold nanoparticles (Au-NPs) and myoglobin (Mb), and depositing it on the surface of a carbon paste electrode containing the ionic liquid N-hexylpyridinium hexafluorophosphate as the binder. UV–vis and FT-IR revealed the Mb in the composite film to have remained in its native structure. A pair of well-defined redox peaks appears in cyclic voltammograms and indicates direct electron transfer from the Mb to the underlying electrode. The results are attributed to the favorable orientation of Mb in the composite film, to the synergistic effects of Co 3 O 4 nanorods and Au-NPs. The modified electrode shows excellent electrocatalytic ability towards the reduction of substrates such as trichloroacetic acid and nitrite, and displays good stability and reproducibility. (author)

  16. Modification of montmorillonite fillers by ionizing radiation

    International Nuclear Information System (INIS)

    Zimek, Z.; Przybytniak, G.; Nowicki, A.; Mirkowski, K.

    2006-01-01

    The mineral fillers can be modified by using unsaturated compounds: styrene, methacrylic acid and maleic anhydride (MA), following by irradiation with high energy electron beam. In presented paper the authors have used this method to change properties of bentonite S pecjal , containing about 70% of pure montmorillonite. It has been shown that: (a) the particles obtained in this process can be good fillers for the production of composites; (b) maleic anhydride reacts via anhydride group with active ionic sites of bentonite, forming a salt-like compound. Irradiation with electron beam leads to the breakage of double bond in maleic anhydride and to the production of new organic phases

  17. Nanocomposites of rice and banana flours blend with montmorillonite: Partial characterization

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez-Marín, María L.; Bello-Pérez, Luis A. [Centro de Desarrollo de Productos Bióticos, Instituto Politécnico Nacional, Km 6 carr Yautepec-Jojutla, Calle Ceprobi No. 8, Colonia San Isidro, Apartado Postal 24, C.P 62731, Yautepec, Morelos (Mexico); Yee-Madeira, Hernani [Departamento de Física, Escuela Superior de Física y Matemáticas-IPN, Edificio 9, U.P., ‘Adolfo López Mateos’ Col. Lindavista, C.P. 07738, México, D. F. (Mexico); Zhong, Qixin [Department of Food science and Technology, the University of Tennessee, Knoxville (United States); González-Soto, Rosalía A., E-mail: rsoto@ipn.mx [Centro de Desarrollo de Productos Bióticos, Instituto Politécnico Nacional, Km 6 carr Yautepec-Jojutla, Calle Ceprobi No. 8, Colonia San Isidro, Apartado Postal 24, C.P 62731, Yautepec, Morelos (Mexico)

    2013-10-15

    Rice and banana flours are inexpensive starchy materials that can form films with more improved properties than those made with their starch because flour and starch present different hydrophobicity. Montmorillonite (MMT) can be used to further improve the properties of starch-based films, which has not received much research attention for starchy flours. The aim of this work was to evaluate the mechanical and barrier properties of nanocomposite films of banana and rice flours as matrix material with addition of MMT as a nanofiller. MMT was modified using citric acid to produce intercalated structures, as verified by the X-ray diffraction pattern. The intercalated MMT was blended with flour slurries, and films were prepared by casting. Nanocomposite films of banana and rice flours presented an increase in the tensile at break and elongation percentage, respectively, more than their respective control films without MMT. This study showed that banana and rice flours could be alternative raw materials to use in making nanocomposite films. - Highlights: • Flour films presented adequate mechanical and barrier properties. • Addition of montmorillonite modified the mechanical and barrier properties of flour films. • The mechanical properties of the films were influenced by the different components of the flours. • The fiber of the banana flour improved the mechanical properties of the films.

  18. Nanocomposites of rice and banana flours blend with montmorillonite: Partial characterization

    International Nuclear Information System (INIS)

    Rodríguez-Marín, María L.; Bello-Pérez, Luis A.; Yee-Madeira, Hernani; Zhong, Qixin; González-Soto, Rosalía A.

    2013-01-01

    Rice and banana flours are inexpensive starchy materials that can form films with more improved properties than those made with their starch because flour and starch present different hydrophobicity. Montmorillonite (MMT) can be used to further improve the properties of starch-based films, which has not received much research attention for starchy flours. The aim of this work was to evaluate the mechanical and barrier properties of nanocomposite films of banana and rice flours as matrix material with addition of MMT as a nanofiller. MMT was modified using citric acid to produce intercalated structures, as verified by the X-ray diffraction pattern. The intercalated MMT was blended with flour slurries, and films were prepared by casting. Nanocomposite films of banana and rice flours presented an increase in the tensile at break and elongation percentage, respectively, more than their respective control films without MMT. This study showed that banana and rice flours could be alternative raw materials to use in making nanocomposite films. - Highlights: • Flour films presented adequate mechanical and barrier properties. • Addition of montmorillonite modified the mechanical and barrier properties of flour films. • The mechanical properties of the films were influenced by the different components of the flours. • The fiber of the banana flour improved the mechanical properties of the films

  19. Modified montmorillonite as vector for gene delivery.

    Science.gov (United States)

    Lin, Feng-Huei; Chen, Chia-Hao; Cheng, Winston T K; Kuo, Tzang-Fu

    2006-06-01

    Currently, gene delivery systems can be divided into two parts: viral or non-viral vectors. In general, viral vectors have a higher efficiency on gene delivery. However, they may sometimes provoke mutagenesis and carcinogenesis once re-activating in human body. Lots of non-viral vectors have been developed that tried to solve the problems happened on viral vectors. Unfortunately, most of non-viral vectors showed relatively lower transfection rate. The aim of this study is to develop a non-viral vector for gene delivery system. Montmorillonite (MMT) is one of clay minerals that consist of hydrated aluminum with Si-O tetrahedrons on the bottom of the layer and Al-O(OH)2 octahedrons on the top. The inter-layer space is about 12 A. The room is not enough to accommodate DNA for gene delivery. In the study, the cationic hexadecyltrimethylammonium (HDTMA) will be intercalated into the interlayer of MMT as a layer expander to expand the layer space for DNA accommodation. The optimal condition for the preparation of DNA-HDTMA-MMT is as follows: 1 mg of 1.5CEC HDTMA-MMT was prepared under pH value of 10.7 and with soaking time for 2 h. The DNA molecules can be protected from nuclease degradation, which can be proven by the electrophoresis analysis. DNA was successfully transfected into the nucleus of human dermal fibroblast and expressed enhanced green fluorescent protein (EGFP) gene with green fluorescence emission. The HDTMA-MMT has a great potential as a vector for gene delivery in the future.

  20. Developing an electrochemical sensor based on a carbon paste electrode modified with nano-composite of reduced graphene oxide and CuFe2O4 nanoparticles for determination of hydrogen peroxide.

    Science.gov (United States)

    Benvidi, Ali; Nafar, Mohammad Taghi; Jahanbani, Shahriar; Tezerjani, Marzieh Dehghan; Rezaeinasab, Masoud; Dalirnasab, Sudabeh

    2017-06-01

    In this paper, a highly sensitive voltammetric sensor based on a carbon paste electrode with CuFe 2 O 4 nanoparticle (RGO/CuFe 2 O 4 /CPE) was designed for determination of hydrogen peroxide (H 2 O 2 ). The electrocatalytic reduction of H 2 O 2 was examined using various techniques such as cyclic voltammetry (CV), chronoamperometry, amperometry and differential pulse voltammetry (DPV). CuFe 2 O 4 nanoparticles were synthesized by co-precipitation method and characterized with scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) techniques. Then, a high conductive platform based on a carbon paste electrode modified with RGO and CuFe 2 O 4 nanoparticles was prepared as a suitable platform for determination of hydrogen peroxide. Under the optimum conditions (pH5), the modified electrode indicated a fast amperometric response of determination of hydrogen peroxide. Also, the peak current of differential pulse voltammetry (DPV) of hydrogen peroxide is increased linearly with its concentration in the ranges of 2 to 10μM and 10 to 1000μM. The obtained detection limit for hydrogen peroxide was evaluated to be 0.064μM by DPV. The designed sensor was successfully applied for the assay of hydrogen peroxide in biological and pharmaceutical samples such as milk, green tea, and hair dye cream and mouthwash solution. Copyright © 2017. Published by Elsevier B.V.

  1. Micro-extraction and trace determination of cadmium by square wave voltammetry at the carbon paste electrode impregnated with Ca10(PO4)6(OH)2

    International Nuclear Information System (INIS)

    El Mhammedi, M.A.; Achak, M.; Najih, R.; Bakasse, M.; Chtaini, A.

    2009-01-01

    The electrochemical behavior of cadmium ions at hydroxyapatite modified carbon paste electrode (HAP-CPE) is reported. The electrode paste was prepared as a mixture of finely powdered hydroxyapatite (HAP) together with graphite powder. The influence of variables such as the accumulation time, pH solution and apatite loading was tested by square wave voltammetry (SWV). The best results were obtained under the following optimized conditions: 5 min accumulation time, 5 mV pulse amplitude, 1 mV s -1 scan rate in 1.0 mol L -1 HClO 4 . The electrochemical responses obtained by SWV at HAP-CPE were found to be analytically suitable to develop a method for the determination of cadmium at low concentration levels. Under optimized operational conditions, a linear response range from 2 x 10 -8 mol L -1 to 2.5 x 10 -5 mol L -1 was obtained. The detection limit for cadmium determination was 4.0 x 10 -9 mol L -1 . The proposed sensor presented good repeatability, evaluated in terms of relative standard deviation (R.S.D. = 3.8%) for n = 5 and was applied for cadmium determination in water samples. The average recovery for these samples was 104%.

  2. Montmorillonite stability. With special respect to KBS-3 conditions

    International Nuclear Information System (INIS)

    Karnland, Ola; Birgersson, Martin

    2006-08-01

    The basic advantageous properties, e.g. low hydraulic conductivity and high swelling pressure, of the bentonite buffer in a KBS- repository stem from a strong interaction between water and the montmorillonite mineral in the bentonite. Minerals similar in structure but with substantially lower mineral-water interaction exist in nature. Transformations from montmorillonite to such minerals are observed e.g. in burial diagenesis and in contact metamorphism. A thermodynamic consideration confirms that medium and low charged montmorillonite is not in chemical equilibrium with quartz. From a safety assessment perspective it is therefore of vital importance to quantify the montmorillonite transformation under KBS- conditions. Silica release from the montmorillonite tetrahedral layers is the initial process for several possible transformations. Replacement of silica by aluminum increases the layer charge but maintains the basic atomic structure. A sufficiently high layer charge results in an irreversible collapse of the clay-water structure, i.e. a non-swelling mineral is formed. Compared to other cations, potassium as counter ion leads to a collapse at lower layer charge and the produced phase is generally termed illite. Montmorillonite-to-illite transformation is the most frequently found alteration process in nature. Three different kinetic illitization models are reviewed and the model proposed by Huang et al. is considered the most suitable for quantification in a KBS- repository, since the kinetic rate expression and its associated parameters are systematically determined by laboratory work. The model takes into account temperature, montmorillonite fraction and potassium concentration, but do not include relevant parameters such as pH, temperature gradients and water content. Calculations by use of the Huang illitization model applied for repository conditions yield insignificant montmorillonite transformation also under very pessimistic assumptions. Other non

  3. Montmorillonite stability. With special respect to KBS-3 conditions

    Energy Technology Data Exchange (ETDEWEB)

    Karnland, Ola; Birgersson, Martin [Clay Technology AB, Lund (Sweden)

    2006-08-15

    The basic advantageous properties, e.g. low hydraulic conductivity and high swelling pressure, of the bentonite buffer in a KBS- repository stem from a strong interaction between water and the montmorillonite mineral in the bentonite. Minerals similar in structure but with substantially lower mineral-water interaction exist in nature. Transformations from montmorillonite to such minerals are observed e.g. in burial diagenesis and in contact metamorphism. A thermodynamic consideration confirms that medium and low charged montmorillonite is not in chemical equilibrium with quartz. From a safety assessment perspective it is therefore of vital importance to quantify the montmorillonite transformation under KBS- conditions. Silica release from the montmorillonite tetrahedral layers is the initial process for several possible transformations. Replacement of silica by aluminum increases the layer charge but maintains the basic atomic structure. A sufficiently high layer charge results in an irreversible collapse of the clay-water structure, i.e. a non-swelling mineral is formed. Compared to other cations, potassium as counter ion leads to a collapse at lower layer charge and the produced phase is generally termed illite. Montmorillonite-to-illite transformation is the most frequently found alteration process in nature. Three different kinetic illitization models are reviewed and the model proposed by Huang et al. is considered the most suitable for quantification in a KBS- repository, since the kinetic rate expression and its associated parameters are systematically determined by laboratory work. The model takes into account temperature, montmorillonite fraction and potassium concentration, but do not include relevant parameters such as pH, temperature gradients and water content. Calculations by use of the Huang illitization model applied for repository conditions yield insignificant montmorillonite transformation also under very pessimistic assumptions. Other non

  4. Fungal biomineralization of montmorillonite and goethite to short-range-ordered minerals

    Science.gov (United States)

    Li, Huan; Hu, Shuijin; Polizzotto, Matthew L.; Chang, Xiaoli; Shen, Qirong; Ran, Wei; Yu, Guanghui

    2016-10-01

    Highly reactive nano-scale minerals, e.g., short-range-ordered minerals (SROs) and other nanoparticles, play an important role in soil carbon (C) retention. Yet, the mechanisms that govern biomineralization from bulk minerals to highly reactive nano-scale minerals remain largely unexplored, which critically hinders our efforts toward managing nano-scale minerals for soil C retention. Here we report the results from a study that explores structural changes during Aspergillus fumigatus Z5 transformation of montmorillonite and goethite to SROs. We examined the morphology and structure of nano-scale minerals, using high-resolution transmission electron microscopy, time-resolved solid-state 27Al and 29Si NMR, and Fe K-edge X-ray absorption fine structure spectroscopy combined with two dimensional correlation spectroscopy (2D COS) analysis. Our results showed that after a 48-h cultivation of montmorillonite and goethite with Z5, new biogenic intracellular and extracellular reactive nano-scale minerals with a size of 3-5 nm became abundant. Analysis of 2D COS further suggested that montmorillonite and goethite were the precursors of the dominant biogenic nano-scale minerals. Carbon 1s near edge X-ray absorption fine structure (NEXAFS) spectra and their deconvolution results demonstrated that during fungus Z5 growth, carboxylic C (288.4-289.1 eV) was the dominant organic group, accounting for approximately 34% and 59% in the medium and aggregates, respectively. This result suggested that high percentage of the production of organic acids during the growth of Z5 was the driving factor for structural changes during biomineralization. This is, to the best of our knowledge, the first report of the structural characterization of nano-scale minerals by 2D COS, highlighting its potential to elucidate biomineralization pathways and thus identify the precursors of nano-scale minerals.

  5. Synthesis and characterization of montmorillonite clay intercalated with molecular magnetic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Marcel G.; Martins, Daniel O.T.A.; Carvalho, Beatriz L.C. de [Instituto de Química, Universidade Federal Fluminense, Niterói, RJ 24.020–150 (Brazil); Mercante, Luiza A. [Laboratório Nacional de Nanotecnologia para o Agronegócio (LNNA), Embrapa Instrumentação, São Carlos, SP 13560 970 (Brazil); Soriano, Stéphane [Instituto de Física, Universidade Federal Fluminense, Niterói, RJ 24.210 346 (Brazil); Andruh, Marius [Inorganic Chemistry Laboratory, Faculty of Chemistry, University of Bucharest, Str. Dumbrava Rosie nr. 23, Bucharest (Romania); Vieira, Méri D., E-mail: gqimeri@vm.uff.br [Instituto de Química, Universidade Federal Fluminense, Niterói, RJ 24.020–150 (Brazil); Vaz, Maria G.F., E-mail: mariavaz@vm.uff.br [Instituto de Química, Universidade Federal Fluminense, Niterói, RJ 24.020–150 (Brazil)

    2015-08-15

    In this work montmorillonite (MMT) clay, whose matrix was modified with an ammonium salt (hexadecyltrimethylammonium bromide – CTAB), was employed as an inorganic host for the intercalation of three different molecular magnetic compounds through ion exchange: a nitronyl nitroxide derivative 2-[4-(N-ethyl)-pyridinium]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (p-EtRad{sup +}) and two binuclear coordination compounds, [Ni(valpn)Ln]{sup 3+}, where H{sub 2}valpn stands for 1,3-propanediyl-bis(2-iminomethylene-6-methoxy-phenol), and Ln=Gd{sup III}; Dy{sup III}. The pristine MMT and the intercalated materials were characterized by X-ray powder diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and magnetic measurements. The X-ray diffraction data analysis showed an increase of the interlamellar space of the intercalated MMT, indicating the intercalation of the magnetic compounds. Furthermore, the magnetic properties of the hybrid compounds were investigated, showing similar behavior as the pure magnetic guest species. - Graphical abstract: Montmorillonite clay was employed as inorganic host for the intercalation of three different molecular magnetic compounds through ion exchange - Highlights: • Montmorillonite was employed as a host material. • Three molecular magnetic compounds were intercalated through ion exchange. • The compounds were successful intercalated maintaining the layered structure. • The hybrid materials exhibited similar magnetic behavior as the pure magnetic guest.

  6. Modified clay minerals efficiency against chemical and biological warfare agents for civil human protection.

    Science.gov (United States)

    Plachá, Daniela; Rosenbergová, Kateřina; Slabotínský, Jiří; Kutláková, Kateřina Mamulová; Studentová, Soňa; Martynková, Gražyna Simha

    2014-04-30

    Sorption efficiencies of modified montmorillonite and vermiculite of their mono ionic Na and organic HDTMA and HDP forms were studied against chemical and biological warfare agents such as yperite and selected bacterial strains. Yperite interactions with modified clay minerals were observed through its capture in low-density polyethylene foil-modified clay composites by measuring yperite gas permeation with using chemical indication and gas chromatography methods. The antibacterial activities of synthetized organoclays were tested against selected Gram-positive and Gram-negative bacterial species in minimum inhibitory concentration tests. The obtained results showed a positive influence of modified clay minerals on the significant yperite breakthrough-time increase. The most effective material was the polyethylene-Na form montmorillonite, while the polyethylene-Na form vermiculite showed the lowest efficiency. With increasing organic cations loading in the interlayer space the montmorillonite efficiency decreased, and in the case of vermiculite an opposite effect was observed. Generally the modified montmorillonites were more effective than modified vermiculites. The HDP cations seem to be more effective compare to the HDTMA. The antibacterial activity tests confirmed efficiency of all organically modified clay minerals against Gram-positive bacteria. The confirmation of antibacterial activity against Y. pestis, plague bacteria, is the most interesting result of this part of the study. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Preparation of carbon paste electrodes including poly(styrene) attached glycine-Pt(IV) for amperometric detection of glucose.

    Science.gov (United States)

    Dönmez, Soner; Arslan, Fatma; Sarı, Nurşen; Kurnaz Yetim, Nurdan; Arslan, Halit

    2014-04-15

    In this study, a novel carbon paste electrode that is sensitive to glucose was prepared using the nanoparticles modified (4-Formyl-3-methoxyphenoxymethyl) with polystyren (FMPS) with L-Glycine-Pt(IV) complexes. Polymeric nanoparticles having Pt(IV) ion were prepared from (4-Formyl-3-methoxyphenoxymethyl) polystyren, glycine and PtCl4 by template method. Glucose oxidase enzyme was immobilized to a modified carbon paste electrode (MCPE) by cross-linking with glutaraldehyde. Determination of glucose was carried out by oxidation of enzymatically produced H2O2 at 0.5 V vs. Ag/AgCl. Effects of pH and temperature were investigated, and optimum parameters were found to be 8.0 and 55°C, respectively. Linear working range of the electrode was 5.0×10(-6)-1.0×10(-3) M, R(2)=0.997. Storage stability and operational stability of the enzyme electrode were also studied. Glucose biosensor gave perfect reproducible results after 10 measurements with 2.3% relative standard deviation. Also, it had good storage stability (gave 53.57% of the initial amperometric response at the end of 33th day). © 2013 Published by Elsevier B.V.

  8. Square wave voltammetry at carbon paste electrode modified with surfactant for alpha tocopheryl acetate determination in cosmetics

    Directory of Open Access Journals (Sweden)

    Simona Žabčíková

    2018-03-01

    Full Text Available Normal 0 false false false CS X-NONE X-NONE The aim of this study was describe electrochemical properties of a carbon paste electrode (CPE bulk modified with 30% (w/w surfactant sodium dodecyl sulphate (CPE/SDS and demonstrates its application in the determination of α‑tocopheryl acetate (α‑TAc, known as vitamin E acetate, in selected cosmetic products, especially body creams. In addition to anionic SDS, cationic hexadecylpyridinium chloride monohydrate (CPC was also tested as possible modifier. It was found that selection of surfactant type and its content significantly affect an electrical conductivity and mechanical stability of these heterogeneous electroanalytical sensors in pure organic solvents. Under this study, it was found that CPC is a totally inappropriate mediator due to very high backgroundcurrent. Together with other lipophilic vitamins characterized by antioxidant activity (dominantly retionoids, this completely synthetic substance is widely used as significant cosmetic additive due its preservative properties. Monitoring of its content in cosmetic products is usually performed by high‑performance liquid chromatography (HPLC with UV detection. This standard analytical protocol is always burdened with the complex and time‑consuming preparation of the sample before analysis. For that reason, robust and simple electroanalytical method based on anodic oxidation of the α‑TAc at CPE/SDS by square wave voltammetry (SWV performed in pure organic electrolyte (99.8% acetonitrile containing 0.1 mol·L‑1 LiClO4 was developed. Moreover, simple dissolution of sample in supporting electrolyte using ultrasonic bath and subsequent filtering through a stacked filter included all the necessary procedures for sample preparation. The linear range from 0.1 to 1.2 mmol·L‑1and limit of detection 37 µmol·L‑1 were found at pulse amplitude 10 mV and frequency 10 Hz as optimum. In analysis of selected cosmetics, the developed

  9. Rational interface design of epoxy-organoclay nanocomposites: role of structure-property relationship for silane modifiers.

    Science.gov (United States)

    Bruce, Alex N; Lieber, Danielle; Hua, Inez; Howarter, John A

    2014-04-01

    Montmorillonite was modified by three silane surfactants with different functionalities to investigate the role of surfactant structure on the properties of a final epoxy-organoclay nanocomposite. N-aminopropyldimethylethoxysilane (APDMES), an aminated monofunctional silane, was chosen as a promising surfactant for several reasons: (1) it will bond to silica in montmorillonite, (2) it will bond to epoxide groups, and (3) to overcome difficulties found with trifunctional aminosilane bonding clay layers together and preventing exfoliation. A trifunctional and non-aminated version of APDMES, 3-aminopropyltriethoxysilane (APTES) and n-propyldimethylmethoxysilane (PDMMS), respectively, was also studied to provide comparison to this rationally chosen surfactant. APDMES and APTES were grafted onto montmorillonite in the same amount, while PDMMS was barely grafted (nanocomposite gallery spacing was not dependent on the surfactant used. Different concentrations of APDMES modified montmorillonite yielded different properties, as concentration decreased glass transition temperature increased, thermal stability increased, and the storage modulus decreased. Storage modulus, glass transition temperature, and thermal stability were more similar for epoxy-organoclay composites modified with the same concentration of silane surfactant, neat epoxy, and epoxy-montmorillonite nanocomposite. Copyright © 2013 Elsevier Inc. All rights reserved.

  10. HTCC-Modified Nanoclay for Tissue Engineering Applications: A Synergistic Cell Growth and Antibacterial Efficiency

    Directory of Open Access Journals (Sweden)

    Majid Aliabadi

    2013-01-01

    Full Text Available This paper deals with the synthesis of a biocompatible chitosan ammonium salt N-(2-hydroxy propyl-3-trimethylammonium chitosan chloride (HTCC and using it in montmorillonite ion-exchange process. HTCC-modified montmorillonite (Mt with different chemical ratios was successfully synthesized, and their characteristics have been verified by XRD and FTIR analyses. Produced samples have been evaluated in terms of antibacterial efficiency and biocompatibility (cell culture test. Antibacterial efficiency of synthesized HTCC/Mt samples has been confirmed against both gram negative bacteria (Escherichia coli and gram positive bacteria (Staphylococcus aureus. The results disclosed that the antibacterial efficiency of HTCC-modified montmorillonite was unexpectedly even more than HTCC. This excellent synergistic effect has been referred to entrapping bacteria between the intercalated structures of HTCC-modified montmorillonite. Then HTCC on clay layers can seriously attack and damage the entrapped bacteria. An extraordinary biocompatibility, cell attachment, and cell growth even more than tissue culture polystyrene (TCPS have been recorded in the case of this novel kind of modified clay. Due to existing concerns about serious and chronic infections after implant placement, this natural-based bioactive and antibacterial modified clay can be used in electrospun nanofibers and other polymeric implants with promising mechanical properties for tissue engineering applications.

  11. Multiwall carbon nanotubes chemically modified carbon paste electrodes for determination of gentamicin sulfate in pharmaceutical preparations and biological fluids.

    Science.gov (United States)

    Khalil, M M; Abed El-Aziz, G M

    2016-02-01

    This article focused on the construction and characteristics of novel and sensitive gentamicin carbon paste electrodes which are based on the incorporation of multiwall carbon nanotubes (MWCNTs) which improve the characteristics of the electrodes. The electrodes were constructed based on gentamicin-phosphotungstate (GNS-PTA) called CPE1, gentamicin-phosphomolybdate (GNS-PMA) called CPE2, GNS-PTA+ MWMCNTs called MWCPE1, and GNS-PMA+ MWMCNTs called MWCPE2. The constructed electrodes, at optimum paste composition, exhibited good Nernstian response for determination of gentamicin sulfate (GNS) over a linear concentration range from 2.5×10(-6) to 1×10(-2), 3.0×10(-6) to 1×10(-2), 4.9×10(-7) to 1×10(-2) and 5.0×10(-7) to 1×10(-2)molL(-1), with lower detection limit 1×10(-6), 1×10(-6), 1.9×10(-7) and 2.2×10(-7)molL(-1), and with slope values of 29.0±0.4, 29.2±0.7, 31.2±0.5 and 31.0±0.6mV/decade for CPE1, CPE2, MWCPE1 and MWCPE2, respectively. The response of electrodes is not affected by pH in the range 3-8 for CPE1 and CPE2 and in the range 2.5-8.5 for MWCPE1 and MWCPE2. The results showed fast dynamic response time (about 8-5s) and long lifetime (more than 2months) for all electrodes. The sensors showed high selectivity for gentamicin sulfate (GNS) with respect to a large number of interfering species. The constructed electrodes were successfully applied for determination of GNS in pure form, its pharmaceutical preparations and biological fluids using standard addition and potentiometric titration methods with high accuracy and precision. Published by Elsevier B.V.

  12. EDTA modified glassy carbon electrode: Preparation and characterization

    International Nuclear Information System (INIS)

    Ustuendag, Zafer; Solak, Ali Osman

    2009-01-01

    EDTA-phenoxyamide modified glassy carbon electrode (EDTA-GC) was prepared at a glassy carbon electrode by surface synthesis. In the first step, nitrophenyl was grafted to the glassy carbon (GC) surface via the electrochemical reduction of its tetraflouroborate diazonium salt. In the second step, nitrophenyl-modified electrode (NP-GC) was subjected to the cathodic potential scan to reduce the nitro to amine group. p-Aminophenyl modified glassy carbon electrode (AP-GC) was dipped into a EDTA solution containing 1-ethyl-3(3-(dimethlyamino)propyl)-carbodiimide (EDC) as an activating agent. Thus formed ((2-anilino-2-oxoethyl){2-[bis(carboxymethyl)amino]-ethyl}amino)acetic acid modified GC electrode was denoted as EDTA-GC and characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ellipsometry and X-ray photoelectron spectroscopy (XPS). Complexation of the EDTA-GC surface with Pb 2+ ions was investigated if this electrode could be used as a metal sensor.

  13. Chemically modified carbon fibers and their applications

    International Nuclear Information System (INIS)

    Ermolenko, I.N.; Lyubliner, I.P.; Gulko, N.V.

    1990-01-01

    This book gives a comprehensive review about chemically modified carbon fibers (e.g. by incorporation of other elements) and is structured as follows: 1. Types of carbon fibers, 2. Structure of carbon fibers, 3. Properties of carbon fibers, 4. The cellulose carbonization process, 5. Formation of element-carbon fiber materials, 6. Surface modification of carbon fibers, and 7. Applications of carbon fibers (e.g. adsorbents, catalysts, constituents of composites). (MM)

  14. An easy and effective method for the intercalation of hydrophobic natural dye into organo-montmorillonite for improved photostability

    Science.gov (United States)

    Taguchi, Taiga; Kohno, Yoshiumi; Shibata, Masashi; Tomita, Yasumasa; Fukuhara, Choji; Maeda, Yasuhisa

    2018-05-01

    β-carotene (BC) is one of the naturally occurring dyes belonging to the carotenoids group. Although it is more environmentally friendly and better suited for humans compared with synthetic dyes, it destabilizes with light and heat, easily losing its color under irradiation. Extended application of BC are therefore limited. The aim of this study is to improve the stability of BC by intercalation into the montmorillonite layers modified with a cationic surfactant, by a simple mixing and minimal solvent use. The physical mixing of small quantities of concentrated BC/hexane solutions with organo-modified montmorillonite successfully resulted in the composite material. The length and the number of alkyl chains of the surfactant used for the organic modification influenced the stability enhancement of the incorporated dye. The improved stability of the dye molecules incorporated in the interlayer space was found to be due to restricted contact with atmospheric oxygen.

  15. EDTA modified glassy carbon electrode: Preparation and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Ustuendag, Zafer [Dumlupinar University, Faculty of Arts and Sciences, Department of Chemistry, Kuetahya (Turkey); Solak, Ali Osman [Ankara University, Faculty of Science, Department of Chemistry, Degol Street, Tandogan, 06100 Ankara (Turkey)], E-mail: osolak@science.ankara.edu.tr

    2009-11-01

    EDTA-phenoxyamide modified glassy carbon electrode (EDTA-GC) was prepared at a glassy carbon electrode by surface synthesis. In the first step, nitrophenyl was grafted to the glassy carbon (GC) surface via the electrochemical reduction of its tetraflouroborate diazonium salt. In the second step, nitrophenyl-modified electrode (NP-GC) was subjected to the cathodic potential scan to reduce the nitro to amine group. p-Aminophenyl modified glassy carbon electrode (AP-GC) was dipped into a EDTA solution containing 1-ethyl-3(3-(dimethlyamino)propyl)-carbodiimide (EDC) as an activating agent. Thus formed ((2-anilino-2-oxoethyl){l_brace}2-[bis(carboxymethyl)amino]-ethyl{r_brace}amino)acetic acid modified GC electrode was denoted as EDTA-GC and characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), ellipsometry and X-ray photoelectron spectroscopy (XPS). Complexation of the EDTA-GC surface with Pb{sup 2+} ions was investigated if this electrode could be used as a metal sensor.

  16. Polymer Nanocomposites—A Comparison between Carbon Nanotubes, Graphene, and Clay as Nanofillers

    Science.gov (United States)

    Bhattacharya, Mrinal

    2016-01-01

    Nanofilled polymeric matrices have demonstrated remarkable mechanical, electrical, and thermal properties. In this article we review the processing of carbon nanotube, graphene, and clay montmorillonite platelet as potential nanofillers to form nanocomposites. The various functionalization techniques of modifying the nanofillers to enable interaction with polymers are summarized. The importance of filler dispersion in the polymeric matrix is highlighted. Finally, the challenges and future outlook for nanofilled polymeric composites are presented. PMID:28773388

  17. New synthesis of poly ortho-methoxyaniline nanostructures and its application to construct modified multi-wall carbon nanotube/graphite paste electrode for simultaneous determination of uric acid and folic acid

    Energy Technology Data Exchange (ETDEWEB)

    Rajabi, Hossein, E-mail: h.rajabi8086@gmail.com; Noroozifar, Meissam

    2017-06-01

    Uric acid (UA) and folic acid (FA) are compounds of biomedical interest. In humans, about 70% of daily uric acid disposal occurs via the kidneys, and in 5–25% of humans, impaired renal (kidney) excretion leads to hyperuricemia. Folate is another form folic acid of which is known as, is one of the B vitamins. It is used as a supplement by women to prevent neural tube defects developing during pregnancy. Polyortho-methoxyaniline nanostructures (POMANS) was synthesized with a new two phase (organic-water) synthesis method. The POMANS was characterized using transmission electron microscopy (TEM) and Fourier transform IR (FTIR). This polymer was used to construct a modified multi-wall carbon nanotube, graphite paste electrode (POMANS-MWCNT/GPE). Linear sweep voltammograms (LSV), cyclic voltammetry (CV) and chronoamperometry were used to investigate the suitability of polyortho-methoxyaniline with multi-wall carbon nanotubes paste electrode as a modifier for the electrocatalytic oxidation of UA and FA in aqueous solutions with various pHs. The results showed that POMANS-MWCNT/GPE had high anodic peak currents for the electrooxidation of UA and FA in pH 6.0.Under the optimized conditions, The catalytic peak currents obtained, was linearly dependent on the UA and FA concentrations in the range of 0.6–52 and 0.5–68 μM with two segments and the detection limits 0.157 and 0.113 μM for UA and FA were, respectively. Finally, the proposed method was also examined as a sensitive, simple and inexpensive electrochemical sensor for the simultaneous determination of UA and FA in real samples such as urine and serum. - Highlights: • For the first time, POMANS was synthesized with a new method of two-phase organic & water. • POMANS-MWCNT/GPE was used for simultaneous determination of UA and FA at optimum pH 6.0. • Parameters n and α were also determined for UA and FA. • Electrochemical simultaneous determination of UA and FA with modified electrode real samples.

  18. Montmorillonite based artificial nacre prepared via a drying process

    International Nuclear Information System (INIS)

    Bennadji-Gridi, Fayza; Smith, Agnes; Bonnet, Jean-Pierre

    2006-01-01

    Taking advantage of the specific behaviour of Na/Ca montmorillonite in aqueous dispersion, textured films were prepared by progressive evaporation of dispersions with low concentrations of delaminated platelets. The increase of the concentration of ions during evaporation changes the nature of the clay mineral platelet face interactions from repulsive to attractive. After complete drying, a dense brick-like structure is obtained when a sodium salt is used as deflocculant. The bending strength of the textured film is strongly affected by cracks formation during drying, specially when the sample thickness increases. After optimisation, crack-free textured samples with a 140 μm thickness, 20 cm x 25 cm area and 120 MPa bending strength were obtained

  19. The Adsorption Mechanism of Modified Activated Carbon on Phenol

    Directory of Open Access Journals (Sweden)

    Lin J. Q.

    2016-01-01

    Full Text Available Modified activated carbon was prepared by thermal treatment at high temperature under nitrogen flow. The surface properties of the activated carbon were characterized by Boehm titration, BET and point of zero charge determination. The adsorption mechanism of phenol on modified activated carbon was explained and the adsorption capacity of modified activated carbon for phenol when compared to plain activated carbon was evaluated through the analysis of adsorption isotherms, thermodynamic and kinetic properties. Results shows that after modification the surface alkaline property and pHpzc value of the activated carbon increase and the surface oxygen-containing functional groups decrease. The adsorption processes of the plain and modified carbon fit with Langmuir isotherm equation well, and the maximum adsorption capacity increase from 123.46, 111.11, 103.09mg/g to 192.31, 178.57, 163,93mg/g under 15, 25 and 35°C after modification, respectively. Thermodynamic parameters show that the adsorption of phenol on activated carbon is a spontaneously exothermic process of entropy reduction, implying that the adsorption is a physical adsorption. The adsorption of phenol on activated carbon follows the pseudo-second-order kinetics (R2>0.99. The optimum pH of adsorption is 6~8.

  20. Effect of Mg/Ca ratios on microbially induced carbonate precipitation

    Science.gov (United States)

    Balci, Nurgul; Demirel, Cansu; Seref Sonmez, M.; Kurt, M. Ali

    2016-04-01

    Influence of Mg/Ca ratios on microbially induced carbonate mineralogy were investigated by series of experiments carried out under various environmental conditions (Mg/Ca ratio, temperature and salinity). Halophilic bacterial cultures used for biomineralization experiments were isolated from hypersaline Lake Acıgöl (Denizli, SW Turkey), displaying extreme water chemistry with an average pH around 8.6 (Balci eta l.,2015). Enriched bacterial culture used in the experiments consisted of Halomonas saccharevitans strain AJ275, Halomonas alimentaria strain L7B; Idiomarina sp. TBZ29, 98% Idiomarina seosensis strain CL-SP19. Biomineralization experiments were set up using above enriched culture with Mg/Ca ratios of 0.05, 1, 4 and 15 and salinity of 8% and 15% experiments at 30oC and 10oC. Additionally, long-term biomineralization experiments were set up to last for a year, for Mg/Ca=4 and Mg/Ca=15 experiments at 30oC. For each experimental condition abiotic experiments were also conducted. Solution chemistry throughout incubation was monitored for Na, K, Mg, Ca, bicarbonate, carbonate, ammonium and phosphate for a month. At the end of the experiments, precipitates were collected and morphology and mineralogy of the biominerals were investigated and results were evaluated using the software DIFFRAC.SUITE EVA. Overall the preliminary results showed chemical precipitation of calcite, halite, hydromagnesite and sylvite. Results obtained from biological experiments indicate that, low Mg/Ca ratios (0.05 and 1) favor chlorapatite precipitation, whereas higher Mg/Ca ratios favor struvite precipitation. Biomineralization of dolomite, huntite and magnesite is favorable at high Mg/Ca ratios (4 and 15), in the presence of halophilic bacteria. Moreover, results indicate that supersaturation with respect to Mg (Mg/Ca=15) combined with NaCl (15%) inhibits biomineralization and forms chemical precipitates. 15% salinity is shown to favor chemical precipitation of mineral phases more than

  1. All-solid-state carbonate-selective electrode based on screen-printed carbon paste electrode

    International Nuclear Information System (INIS)

    Li, Guang; Lyu, Xiaofeng; Wang, Zhan; Rong, Yuanzhen; Hu, Ruifen; Wang, You; Luo, Zhiyuan

    2017-01-01

    A novel disposable all-solid-state carbonate-selective electrode based on a screen-printed carbon paste electrode using poly(3-octylthiophene-2,5-diyl) (POT) as an ion-to-electron transducer has been developed. The POT was dropped onto the reaction area of the carbon paste electrode covered by the poly(vinyl chloride) (PVC) membrane, which contains N,N-Dioctyl-3 α ,12 α -bis(4-trifluoroacetylbenzoyloxy)-5 β -cholan-24-amide as a carbonate ionophore. The electrode showed a near-Nernstian slope of  −27.5 mV/decade with a detection limit of 3.6 * 10 −5 mol l −1 . Generally, the detection time was 30 s. Because these electrodes are fast, convenient and low in cost, they have the potential to be mass produced and used in on-site testing as disposable sensors. Furthermore, the repeatability, reproducibility and stability have been studied to evaluate the properties of the electrodes. Measurement of the carbonate was also conducted in a human blood solution and achieved good performance. (paper)

  2. Nano Copper Oxide-Modified Carbon Cloth as Cathode for a Two-Chamber Microbial Fuel Cell

    OpenAIRE

    Dong, Feng; Zhang, Peng; Li, Kexun; Liu, Xianhua; Zhang, Pingping

    2016-01-01

    In this work, Cu2O nanoparticles were deposited on a carbon cloth cathode using a facile electrochemical method. The morphology of the modified cathode, which was characterized by scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) tests, showed that the porosity and specific surface area of the cathode improved with longer deposition times. X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) results showed that cupric oxide and cuprous oxide coexisted on the ca...

  3. Influence of montmorillonite on antimicrobial activity of tetracycline and ciprofloxacin

    Science.gov (United States)

    Lv, Guocheng; Pearce, Cody W.; Gleason, Andrea; Liao, Libing; MacWilliams, Maria P.; Li, Zhaohui

    2013-11-01

    Antibiotics are used not only to fight infections and inhibit bacterial growth, but also as growth promotants in farm livestock. Farm runoff and other farm-linked waste have led to increased antibiotic levels present in the environment, the impact of which is not completely understood. Soil, more specifically clays, that the antibiotic contacts may alter its effectiveness against bacteria. In this study a swelling clay mineral montmorillonite was preloaded with antibiotics tetracycline and ciprofloxacin at varying concentrations and bioassays were conducted to examine whether the antibiotics still inhibited bacterial growth in the presence of montmorillonite. Escherichia coli was incubated with montmorillonite or antibiotic-adsorbed montmorillonite, and then the number of viable bacteria per mL was determined. The antimicrobial activity of tetracycline was affected in the presence of montmorillonite, as the growth of non-resistant bacteria was still found even when extremely high TC doses were used. Conversely, in the presence of montmorillonite, ciprofloxacin did inhibit E. coli bacterial growth at high concentrations. These results suggest that the effectiveness of antimicrobial agents in clayey soils depends on the amount of antibiotic substance present, and on the interactions between the antibiotic and the clays in the soil, as well.

  4. Damage identification in cement paste amended with carbon nanotubes

    Science.gov (United States)

    Soltangharaei, Vafa; Anay, Rafal; Assi, Lateef; Ziehl, Paul; Matta, Fabio

    2018-04-01

    Cement-based composites have been used as reliable materials in building and civil engineering infrastructure for many decades. Although there are several advantages, some drawbacks such as premature cracking may be problematic for sensitive applications such as those found in nuclear power plants or associated waste storage facilities. In this study, acoustic emission monitoring was employed to detect stress waves associated with damage progression during uniaxial compressive loading. Acoustic emission data resulting from loading of plain cement paste prisms and cement paste prisms amended with carbon nanotubes are compared. Unsupervised pattern recognition is employed to categorize the data. Results indicate that increased acoustic emission activity was recorded for the plain cement paste prisms when compared to prisms amended with carbon nanotubes.

  5. Modified glassy carbon electrodes based on carbon nanostructures for ultrasensitive electrochemical determination of furazolidone

    Energy Technology Data Exchange (ETDEWEB)

    Shahrokhian, Saeed, E-mail: shahrokhian@sharif.edu [Department of Chemistry, Sharif University of Technology, Tehran 11155-9516 (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Naderi, Leila [Department of Chemistry, Sharif University of Technology, Tehran 11155-9516 (Iran, Islamic Republic of); Ghalkhani, Masoumeh [Department of Chemistry, Faculty of Science, Shahid Rajaee Teacher Training University, Lavizan, Tehran (Iran, Islamic Republic of); Institute for advanced technology, Shahid Rajaee Teacher Training University, Lavizan, Tehran, 16788 (Iran, Islamic Republic of)

    2016-04-01

    The electrochemical behavior of Furazolidone (Fu) was investigated on the surface of the glassy carbon electrode modified with different carbon nanomaterials, including carbon nanotubes (CNTs), carbon nanoparticles (CNPs), nanodiamond-graphite (NDG), graphene oxide (GO), reduced graphene oxide (RGO) and RGO-CNT hybrids (various ratios) using linear sweep voltammetry (LSV). The results of voltammetric studies exhibited a considerable increase in the cathodic peak current of Fu at the RGO modified GCE, compared to other modified electrodes and also bare GCE. The surface morphology and nature of the RGO film was thoroughly characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The modified electrode showed two linear dynamic ranges of 0.001–2.0 μM and 2.0–10.0 μM with a detection limit of 0.3 nM for the voltammetric determination of Fu. This sensor was used successfully for Fu determination in pharmaceutical and clinical preparations. - Highlights: • The electrochemical behavior of Furazolidone (Fu) was investigated on the surface of the modified electrode with different carbon nanomaterials by Linear sweep voltammetry. • Two linear dynamic ranges and a low detection limit were obtained. • The modified electrode was applied for the detection of Fu in pharmaceutical and clinical preparations.

  6. Modified montmorillonite as a heterogeneous catalyst in (m)ethyl esterification reaction of lauric acid; Montmorilonita modificada como catalisador heterogeneo em reacoes de esterificacao (M)etilica de acido laurico

    Energy Technology Data Exchange (ETDEWEB)

    Zatta, Leandro; Nepel, Angelita; Barison, Andersson; Wypych, Fernando, E-mail: wypych@ufpr.br [Departamento de Quimica, Universidade Federal do Parana (UFPR), Curitiba , PR (Brazil)

    2012-07-01

    Montmorillonite was modified with zirconium polyoxycations in the presence of ammonium sulphate. The material was characterized and used as a catalyst in the esterification of lauric acid, the reactions being accompanied by 2{sup 3} factorial design. Conversions of up to 95.33 and 83.35% were observed for the methyl and ethyl esterification reactions respectively, proving superior to results obtained by thermal conversion. The material was submitted to three reaction cycles and similar conversions were observed, indicating the catalyst is not significantly deactivated after reuse. The catalyst was also tested under reflux conditions, yielding a maximum conversion of 36.86%. (author)

  7. Electrochemical Effect of Different Modified Glassy Carbon Electrodes on the Values of Diffusion Coefficient for Some Heavy Metal Ions

    International Nuclear Information System (INIS)

    Radhi, M M; Alwan, S H; Amir, Y K A; Tee, T W

    2013-01-01

    Glassy carbon electrode (GCE) was modified with carbon nanotubes (CNT), C 60 and activated carbon (AC) by mechanical attachment method and solution evaporation technique to preparation CNT/GCE, C 60 /GCE and AC/GCE, these electrodes were modified in Li + solution via cyclic voltammetry (CV) potential cycling to preparing CNT/Li + /GCE, C 60 /Li + /GCE and AC/Li + /GCE. The sensing characteristics of the modified film electrodes, demonstrated in the application study for different heavy metal ions such as Hg 2+ , Cd 2+ , and Mn 2+ . Cyclic voltammetric effect by chronoamperometry (CA) technique was investigated to determination the diffusion coefficient (D f ) values from Cottrell equation at these ions. Based on Cottrell equation (diffusion coefficient) of the redox current peaks of different heavy metal ions at different modified electrodes were studied to evaluate the sensing of these electrodes by the diffusion coefficient values. The modification of GCE with nano materials and Li + act an enhancement for the redox current peaks to observe that the diffusion process are high at CNT/Li + /GCE, C 60 /Li + /GCE and AC/Li+/GCE, but it has low values at unmodified GCE.

  8. Preparation and Characterization of Phenolic Resin/Montmorillonite Nanocomposite

    Directory of Open Access Journals (Sweden)

    Morteza Soltan-Dehghan

    2012-12-01

    Full Text Available Phenolic resins have been widely used for selective high technology applications due to their excellent ablative properties, structural integrity and thermal stability that make them appropriate for thermal insulation materials, wood products industry, coatings, moulding compounds and composite materials. Polymer layered silicate nanocomposites based on montmorillonite (MMT have attracted a great deal of attention because of enhanced properties in mechanical, thermal, barrier and clarity properties without a significant increase in density, which is not possible with conventional fillers. Phenolic resin/montmorillonite (Cloisite 15A nanocomposite was prepared by a combined route of solution blending and in-situ polymerization. Theoptimized conditions for preparation of nanocomposite were achieved by evaluation of various processing parameters (mechanical mixer, high speed disperser and high energy ultrasonic source, mixing time (0.5, 1, 3, 10, 24, 48, 72, and 96 h and different amounts of montmorillonite (5 and 10 weight percents of montmorillonite relative to resol. X-Ray Diffractometer and thermal gravimetric analyzer were used accordingly to show the degree of nanodispersions of organomontmorillonite in polymeric matrix and the effect of nanofiller on thermal stability of nanocomposite with respect to neatresol. The results of high energy ultrasonic source show that a nanocomposite of phenolic resin with 5 wt% montmorillonite displays the best dispersion of clay layers. Thermal stability of nanocomposite was increased by 27% in comparison with neat resol.

  9. Polymerization of alanine in the presence of a non-swelling montmorillonite

    Science.gov (United States)

    Paecht-Horowitz, M.; Lahav, N.

    1977-01-01

    Alanine, starting from alanine-adenylate, has been polymerized in the presence of non-swelling Al-montmorillonite. The yield of polymerization is much lower than that obtained in the presence of swelling Na-montmorillonite. The possibility that the changing interlayer spacing in Na-montmorillonite might be responsible for its catalytic properties, is discussed.

  10. Water-based synthesis of TiO2/CeO2 composites supported on plasma-treated montmorillonite for parathion methyl degradation

    Czech Academy of Sciences Publication Activity Database

    Henych, Jiří; Kormunda, M.; Šťastný, Martin; Janoš, P.; Vomáčka, Petr; Matoušek, J.; Štengl, Václav

    2017-01-01

    Roč. 144, AUG (2017), s. 26-35 ISSN 0169-1317 R&D Projects: GA MŠk(CZ) LM2015073 Institutional support: RVO:61388980 Keywords : Montmorillonite * Parathion methyl * Plasma treatment * TiO2 /CeO2 composites Subject RIV: CA - Inorganic Chemistry OBOR OECD: Inorganic and nuclear chemistry Impact factor: 3.101, year: 2016

  11. Rheological, pasting, thermal and retrogradation properties of octenyl succinic anhydride modified potato starch

    Directory of Open Access Journals (Sweden)

    Chuin WON

    Full Text Available Abstract The objective of the present study was to investigate the rheological, pasting, and thermal properties of octenyl succinic anhydrate (OSA-modified potato starch. Potato starch was modified using different concentrations of OSA (0, 1, 3, and 5%, v/v. The degree of substitution (DS for the OSA-modified starch ranged from 0.0012 to 0.0055. The amylose leaching values of native and OSA-modified potato starch with different DS levels were in the range of 47.09-87.32%. The gel strength values of the OSA-modified starch were lower than those of native potato starch. Rapid Visco Analyzer data showed that peak, hot pasting, final and setback viscosities of the native starch decreased after OSA modification. Dynamic shear rheological tests, conducted at 4 °C, indicated that OSA-modified potato starch had weak gel-like behavior with the storage moduli (G' higher than the loss moduli (G” over most of the frequency ranges (0.63-63.8 rad·s-1.

  12. Citrate- and Succinate-Modified Carbonate Apatite Nanoparticles with Loaded Doxorubicin Exhibit Potent Anticancer Activity against Breast Cancer Cells

    Directory of Open Access Journals (Sweden)

    Sultana Mehbuba Hossain

    2018-03-01

    Full Text Available Biodegradable inorganic apatite-based particle complex is popular for its pH-sensitivity at the endosomal acidic environment to facilitate drug release following cellular uptake. Despite being a powerful anticancer drug, doxorubicin shows severe off-target effects and therefore would need a carrier for the highest effectiveness. We aimed to chemically modify carbonate apatite (CA with Krebs cycle intermediates, such as citrate and succinate in order to control the growth of the resultant particles to more efficiently carry and transport the anticancer drug into the cancer cells. Citrate- or succinate-modified CA particles were synthesized with different concentrations of sodium citrate or sodium succinate, respectively, in the absence or presence of doxorubicin. The drug loading efficiency of the particles and their cellular uptake were observed by quantifying fluorescence intensity. The average diameter and surface charge of the particles were determined using Zetasizer. Cell viability was assessed by MTT assay. Citrate-modified carbonate apatite (CMCA exhibited the highest (31.38% binding affinity for doxorubicin and promoted rapid cellular uptake of the drug, leading to the half-maximal inhibitory concentration 1000 times less than that of the free drug in MCF-7 cells. Hence, CMCA nanoparticles with greater surface area enhance cytotoxicity in different breast cancer cells by enabling higher loading and more efficient cellular uptake of the drug.

  13. Accumulation of organic carbon over the past 150 years in five freshwater peatlands in western and central Europe

    International Nuclear Information System (INIS)

    Novak, Martin; Brizova, Eva; Adamova, Marie; Erbanova, Lucie; Bottrell, Simon H.

    2008-01-01

    Under predicted scenarios of global climate change, peatlands may become a net source of greenhouse gases which will accelerate warming of the atmosphere. Comparative studies of peat bogs along present climatic gradients may provide an insight into the future response of boreal and subarctic peatlands to changing temperature and moisture. Three maritime peat bogs in the British Isles, and two high-elevation peatlands in the Czech Republic were studied. All sites were relatively wet, the mean annual temperatures were higher by up to 6 o C at the British/Irish sites than at the Czech sites. Cumulative carbon content in 210 Pb-dated Sphagnum-dominated vertical peat cores increased from the warmer to the colder sites when evaluated for the most recent decades (since ca. 1950). That would correspond to formation of thinner, more highly decomposed peat deposits over the long-term in warmer conditions, and deeper peat bogs in colder conditions. However, when cumulative carbon content was evaluated for the last ca. 150 years, no relationship was found between mean annual temperature and the carbon pool size. Even along broad present-day climatic gradients, site-specific factors controlled organic carbon preservation in peat. Pollen analysis was instrumental in corroborating the 210 Pb dates, identifying wet and dry periods in the past, and it also provided evidence for increasing nitrogen loads in wetland areas

  14. Structural, dielectric and piezoelectric study of Ca-, Zr-modified ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 40; Issue 5. Structural, dielectric and piezoelectric study of Ca-, Zr-modified BaTiO 3 lead-free ceramics. H MSOUNI A TACHAFINE M EL AATMANI D FASQUELLE J C CARRU M EL HAMMIOUI M RGUITI A ZEGZOUTI A OUTZOURHIT M DAOUD. Volume 40 Issue 5 ...

  15. Adsorption of ferrous ions onto montmorillonites

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Dawei, E-mail: qdw109@163.com [Qilu University of Technology, Jinan, 250353, Shandong (China); Niu, Xia [Qilu University of Technology, Jinan, 250353, Shandong (China); Qiao, Min; Liu, Gang; Li, Hongxin; Meng, Zhenxiao [Shandong SiBang pharmaceutical co., LTD, Jinan, Shandong, 250200 (China)

    2015-04-01

    Highlights: • Adsorption study of ferrous ions on montmorillonites. • Using ascorbic acid as antioxidants in adsorption process. • Fe (II)-MMT had good affinity for phosphate. - Abstract: The adsorption of Fe (II) onto montmorillonites was investigated through initial concentration, contact time, pH and temperature. During the whole adsorption process, the ascorbic acid (Vitamin C) was added as a kind of antioxidant, at the same time, deionized water (after boiling) and nitrogen protection were also used to avoid oxidation. The Fe{sup 2+}/Fe{sub total} ratio of the iron exists in the Fe-montmorillonites was found more than 95%. Two kinetic models, including pseudo-first-order and pseudo-second-order model, were used to analyze the adsorption process of Fe (II) on montmorillonites. The results of our study showed that adsorption process fitted with pseudo-second-order well. Adsorption isotherms showed that Langmuir model was better than Freundlich model. The thermodynamic parameters ΔG{sup 0} and ΔH{sup 0} were 3.696 kJ/mol and 6.689 kJ/mol (we just gave the values at 298 K), respectively. The positive values at different temperatures showed that the adsorption process was non-spontaneous and endothermic. The characteristics of materials were determined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Surface area and porosity analyzer, Thermogravimetric analysis (TGA), Differential scanning calorimeter (DSC) and Zeta potential distribution.

  16. Adsorption of copper ions of natural montmorillonite clay

    Directory of Open Access Journals (Sweden)

    Pimneva Ludmila

    2017-01-01

    Full Text Available The prospects of montmorillonite clay using for the extraction of copper ions from natural and waste waters were determined. Specified chemical and phase composition of natural forms of the montmorillonite clay are shown in the article. Quantitative characteristics of adsorption process of copper ions, the statistical exchange capacity is 1,21 (298 К, 1,25 (313 К, 1,43 (333 К. The authors have studied the balance of copper ions by the method of constructing the isotherms. The description of the adsorption process was carried out by the Langmuir, Freundlich and Temkin models. The calculations showed that the best data for the sorption described by Langmuir model. The nature of the interaction of copper ions with montmorillonite clay in natural form is presented. The calculated thermodynamic parameters of the adsorption process, the obtained values of the Gibbs energy have a negative sign -11,5 (298 К, -15,6 (313 К, -16,2 (333 К кJ/mol, that corresponds to a sustainable consolidation of copper ions on the surface of the montmorillonite clay.

  17. Application of Modified Nanonaturally Montmorillonite in Monochlorobenzene Remediation in River Water

    Science.gov (United States)

    Liu, Chen; Chen, Jun-Feng; Li, Yun; Chen, Rong-Chang; Asaoka, Sachio; Yuan, Guo-Li

    2012-12-01

    As the inland waterway transportation developed rapidly in China, the frequency of hazardous chemical leakage accidents is increasing every year. Such pollution to inland river environment has become a world-wide issue. Montmorillonite (Mont) is typical 2:1 layer type silicate clay and due to their special structure, it has been used in organic pollution removal process. In order to improve their ability in pollution adsorption, the pillared Mont was made in this work. Since the common toxic structure in most chemical pollutants is the halogen atom-benzene ring part, we select a typical compound Monochlorobenzene (MCB) as the aim contaminant. In this research, the original Mont, Na-Mont, TiO2 and TiO2-Mont were prepared and used in MCB degradation experiment as catalysts. The influence of catalyst amount, promoter (H2O2) amount, MCB concentration and reaction time to MCB removal rate were studied, respectively in detail.

  18. Montmorillonite-supported Pd{sup 0}, Fe{sup 0}, Cu{sup 0} and Ag{sup 0} nanoparticles: Properties and affinity towards CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Bouazizi, Nabil, E-mail: bouazizi.nabil@hotmail.fr [Nanoqam, Department of Chemistry, University of Quebec at Montreal, QC, H3C 3P8 Canada (Canada); Research unit: Environment, Catalyzes and Process Analysis, ENIG University of Gabes (Tunisia); Barrimo, Diana; Nousir, Saadia [Nanoqam, Department of Chemistry, University of Quebec at Montreal, QC, H3C 3P8 Canada (Canada); Ben Slama, Romdhane [Research unit: Environment, Catalyzes and Process Analysis, ENIG University of Gabes (Tunisia); Roy, René [Nanoqam, Department of Chemistry, University of Quebec at Montreal, QC, H3C 3P8 Canada (Canada); Azzouz, Abdelkrim, E-mail: azzouz.a@uqam.ca [Nanoqam, Department of Chemistry, University of Quebec at Montreal, QC, H3C 3P8 Canada (Canada)

    2017-04-30

    Highlights: • Purification and modification of montmorillonite. • Dispersion and immobilization of metallic nanoparticles within NaMt layers. • Changes of the distance between the minerals clay layers. • Applications of NaMt-M-NPs adsorbents for adsorption of CO{sub 2}. - Abstract: This study reports the carbon dioxide (CO{sub 2}) adsorption on montmorillonite (NaMt) incorporating Cu{sup 0}, Fe{sup 0}, Pd{sup 0} and Ag{sup 0} as metallic nanoparticles (MNPs). The changes in structural, textural, morphological and adsorption properties of the resulting materials (NaMt-MNPs) were investigated. Electron microscopy and X-ray diffraction showed that dispersion of fine MNPs occurs mainly within the interlayer space of NaMt, producing a slight structure expansion. This was accompanied by a visible enhancement of the affinity towards CO{sub 2}, as supported by thermal programmed desorption measurements. NaMt-MNPs displayed high CO{sub 2} retention capacity (CRC) of ca. 657 μmol/g for NaMt-Cu as compared to NaMt. This was explained in terms of increased number of available adsorption sites due to enlarged interlayer spaces caused by MNP insertion. The differences in CO{sub 2} adsorption capacities clearly demonstrate the key role of MNPs in improving the surface properties and adsorption capacity. The results reported herein open new prospects for clay supported metal nanoparticles as efficient adsorbents for CO{sub 2}.

  19. A sensitive method for electrochemical determination of molybdenum (VI in plant foodstuff samples using Ni0.5Zn0.5Fe2O4 nanocomposite modified carbon paste electrode

    Directory of Open Access Journals (Sweden)

    Abbas Afkhami

    2016-07-01

    Full Text Available In the present study, a new chemically modified carbon paste electrode (CPE is constructed for rapid, accurate, simple, highly sensitive, and selective determination of Mo (VI using differential pulse voltammetry. The electrode was prepared using magnetic nickel zinc ferrite nanocomposite (Ni0.5Zn0.5Fe2O4, as the modifier in CPE (Ni0.5Zn0.5Fe2O4/CPE. Mo (VI was determined after preconcentration at the surface of the modified electrode at -0.7 V vs. Ag/AgCl. Under the optimal conditions, the linear dynamic range and limit of detection were 0.005-1.00 and 0.003 µgmL-1, respectively. Ten successive measurements of 0.06 and 0.70 µg mL-1 of Mo (VI ions showed the relative standard deviation of 3.20 and 1.98 %, respectively. The reproducibility and stability of the electrode response were also studied. Investigation of the effects of different cations and anions on the determination of Mo (VI indicated that the electrode is highly selective. Furthermore, the present method was applied to the determination of Mo (VI in several plant foodstuff samples with satisfactory results.

  20. Synthesis of a Biglucoside and Its Application as Montmorillonite Hydration Inhibitor

    Directory of Open Access Journals (Sweden)

    Xin-chun Zhang

    2014-01-01

    Full Text Available A biglucoside (BG was synthesized with glucose and epichlorohydrin as raw materials. The inhibition of BG against montmorillonite swelling was investigated by various methods including montmorillonite linear expansion test, mud ball immersing test, thermogravimetric analysis, and scanning electron microscopy. The results show that the BG has good inhibition ability to the hydration swelling and dispersion of montmorillonite. Under the same condition, the linear expansion ratio of montmorillonite in BG solution is much lower than that of MEG. The particle distribution measurement, thermogravimetric analysis, FT-IR, and scanning electron microscopy results all prove the efficient inhibition of BG.

  1. Hydrothermal effects on montmorillonite

    International Nuclear Information System (INIS)

    Pusch, R.; Karnland, O.

    1988-06-01

    Hydrothermal effects on montmorillonite clay are usually taken to have the form of conversion of this clay mineral to other species, such as illite, disregarding microstructural alteration and cementation caused by precipitation of silica and other compounds. The report is focussed on identification of the primary processes that are involved in such alteration, the release of silica and the microstructural changes associated with heating being of major interest. In the first test phase, Na montmorillonite in distilled water was investigated by XRD, rheology tests and electron microscopy after heating to 60-225 0 C for 0.01 to 1 year. The preliminary conclusions are that heating produces contraction of the particle network to form dense 'branches', the effect being most obvious at the highest temperature but of significance even at 60-100 0 C. Release of substantial amounts of silica gas been documented for temperatures exceeding 150 0 and precipitation of silica was observed on cooling after the hydrothermal testing under the closed conditions that prevailed throughout the tests. The precipitates, which appeared to be amorphous and probably consisted of hydrous silica gels, were concluded to have increased the mechanical strength and caused some brittleness, particularly of the dense clays. The nature of the silica release, which is assumed to be associated with beidellitization, may be closely related to an unstable state of a certain fraction of tetrahedral silica at heat-inducted transfer between two different crystal modes of montmorillonite. (orig.)

  2. Oxygen isotope fractionation effects in soil water via interaction with cations (Mg, Ca, K, Na) adsorbed to phyllosilicate clay minerals

    Science.gov (United States)

    Oerter, Erik; Finstad, Kari; Schaefer, Justin; Goldsmith, Gregory R.; Dawson, Todd; Amundson, Ronald

    2014-07-01

    In isotope-enabled hydrology, soil and vadose zone sediments have been generally considered to be isotopically inert with respect to the water they host. This is inconsistent with knowledge that clay particles possessing an electronegative surface charge and resulting cation exchange capacity (CEC) interact with a wide range of solutes which, in the absence of clays, have been shown to exhibit δ18O isotope effects that vary in relation to the ionic strength of the solutions. To investigate the isotope effects caused by high CEC clays in mineral-water systems, we created a series of monominerallic-water mixtures at gravimetric water contents ranging from 5% to 32%, consisting of pure deionized water of known isotopic composition with homoionic (Mg, Ca, Na, K) montmorillonite. Similar mixtures were also created with quartz to determine the isotope effect of non-, or very minimally-, charged mineral surfaces. The δ18O value of the water in these monominerallic soil analogs was then measured by isotope ratio mass spectrometry (IRMS) after direct headspace CO2 equilibration. Mg- and Ca-exchanged homoionic montmorillonite depleted measured δ18O values up to 1.55‰ relative to pure water at 5% water content, declining to 0.49‰ depletion at 30% water content. K-montmorillonite enriched measured δ18O values up to 0.86‰ at 5% water content, declining to 0.11‰ enrichment at 30% water. Na-montmorillonite produces no measureable isotope effect. The isotope effects observed in these experiments may be present in natural, high-clay soils and sediments. These findings have relevance to the interpretation of results of direct CO2-water equilibration approaches to the measurement of the δ18O value of soil water. The adsorbed cation isotope effect may bear consideration in studies of pedogenic carbonate, plant-soil water use and soil-atmosphere interaction. Finally, the observed isotope effects may prove useful as molecular scale probes of the nature of mineral

  3. Nanocomposite fibers and film containing polyolefin and surface-modified carbon nanotubes

    Science.gov (United States)

    Chu,Benjamin; Hsiao, Benjamin S.

    2010-01-26

    Methods for modifying carbon nanotubes with organic compounds are disclosed. The modified carbon nanotubes have enhanced compatibility with polyolefins. Nanocomposites of the organo-modified carbon nanotubes and polyolefins can be used to produce both fibers and films having enhanced mechanical and electrical properties, especially the elongation-to-break ratio and the toughness of the fibers and/or films.

  4. Montmorillonite ameliorates hyperthyroidism of rats and mice attributed to its adsorptive effect.

    Science.gov (United States)

    Cai, Yan; Meng, Xin-fang; Cao, Yong-xiao; Lu, Hua; Zhu, Shao-fei; Zhou, Liang-zhen

    2006-12-03

    The present study aims to evaluate the adsorbing effect of montmorillonite on thyroid hormone in the entero-hepatic circulation. The concentration of thyroid hormone in the serum of hyperthyroidism model rats and in solution was measured by radioimmunoassay and ultraviolet spectrometry, respectively. The body weight, temperature, and consumption of food and water were observed in hyperthyroidism model rats. Furthermore, hypoxia tolerance, sodium-pentobarbital-induced sleep time, spontaneous activities were measured on hyperthyroidism model mice after being treated with montmorillonite. Results showed that montmorillonite adsorbed thyroxin (T(4)) and triiodothyronine (T(3)) in vitro. Montmorillonite at dosage of 1.0 g/kg and 0.3 g/kg decreased thyroid hormone levels on hyperthyroidism model rats; Montmorillonite (2.0 g/kg and 0.6 g/kg) prolonged the sleep time, improved the hypoxia tolerant capacity and reduced the spontaneous activities of the hyperthyroidism model mice. These results suggest montmorillonite has anti-hyperthyroidism effect attributed to its adsorptive effect.

  5. Gemini Surfactant-Modified Activated Carbon for Remediation of Hexavalent Chromium from Water

    Directory of Open Access Journals (Sweden)

    Yingying Zhou

    2018-01-01

    Full Text Available Gemini surfactants, with double hydrophilic and hydrophobic groups, offer potentially orders of magnitude greater surface activity compared to similar single unit molecules. A cationic Gemini surfactant (Propyl didodecyldimethylammonium Bromide, PDDDAB and a conventional cationic surfactant (Dodecyltrimethylammonium Bromide, DTAB were used to pre-treat and generate activated carbon. The removal efficiency of the surfactant-modified activated carbon through adsorption of chromium(VI was investigated under controlled laboratory conditions. Fourier-transform infrared spectroscopy (FT-IR and scanning electron microscopy (SEM were used to investigate the surface changes of surfactant-modified activated carbon. The effect of important parameters such as adsorbent dosage, pH, ionic strength and contact time were also investigated. The chromium(VI was adsorbed more significantly on the Gemini surfactant-modified activated carbon than on the conventional surfactant-modified activated carbon. The correlation coefficients show the data best fit the Freundlich model, which confirms the monolayer adsorption of chromium(VI onto Gemini surfactant-modified activated carbon. From this assessment, the surfactant-modified (especially Gemini surfactant-modified activated carbon in this study showed promise for practical applications to treat water pollution.

  6. Using a cut-paste method to prepare a carbon nanotube fur electrode

    International Nuclear Information System (INIS)

    Zhang, H; Cao, G P; Yang, Y S

    2007-01-01

    We describe and realize an aligned carbon nanotube array based 'carbon nanotube fur (CNTF)' electrode. We removed an 800 μm long aligned carbon nanotube array from the silica substrate, and then pasted the array on a nickel foam current collector to obtain a CNTF electrode. CNTF's characteristics and electrochemical properties were studied systemically in this paper. The cut-paste method is simple, and does not damage the microstructure of the aligned carbon nanotube array. The CNTF electrode obtained a specific capacitance of 14.1 F g -1 and excellent rate capability

  7. Electrochemical Sensor for Determination of Ascorbic Acid Using a 2-Chlorobenzoyl Ferrocene/Carbon Nanotube Paste Electrode

    Directory of Open Access Journals (Sweden)

    Sayed Zia Mohammadi

    2016-12-01

    Full Text Available A chemically modified carbon paste electrode with 2-chlorobenzoyl ferrocene (2CBF and carbon nanotube (2CBFCNPE was employed to study the electrocatalytic oxidation of ascorbic acid in aqueous solution using cyclic voltammetry, square wave voltammetry and chronoamperometry. The diffusion coefficient (D = 1.42 × 10-6 cm2 s-1, and the kinetic parameter such as the catalytic rate constant (k = 3.7 × 10 3 M-1 s-1 of ascorbic acid oxidation at the surface of 2CBFCNPE were determined using electrochemical approaches. It has been found that under an optimum condition (pH 4.0, the oxidation of ascorbic acid at the surface of such an electrode occurs at a potential about 85 mV less positive than that of an unmodified carbon paste electrode. Applying square wave voltammetry, in phosphate buffer solution (PBS of pH 4.0, the oxidation current increases linearly with two concentration intervals of ascorbic acid, one is 1.0 × 10-7-2.5 × 10-6 M and the other is 2.5 × 10-6-7.0 × 10-5 M. Detection limit (3δ was obtained 64.0 nM. This method was also examined for determination of ascorbic acid in some real samples.

  8. An ultrasensitive and selective electrochemical sensor for determination of estrone 3-sulfate sodium salt based on molecularly imprinted polymer modified carbon paste electrode.

    Science.gov (United States)

    Song, Han; Wang, Yuli; Zhang, Lu; Tian, Liping; Luo, Jun; Zhao, Na; Han, Yajie; Zhao, Feilang; Ying, Xue; Li, Yingchun

    2017-11-01

    A highly sensitive and selective electrochemical sensor based on carbon paste electrode (CPE) modified with molecularly imprinted polymers (MIPs) has been developed for the determination of estrone 3-sulfate sodium salt (ESS). MIPs were prepared in polar medium via bulk polymerization and characterized by scanning electron microscopy and infrared spectroscopy. Cyclic voltammetry was performed to the study preparation process and binding behavior of the MIP-modified CPE (MIP/CPE) toward ESS. The conditions for preparing MIPs and MIP/CPE as well as ESS detection were optimized. Under the optimal experimental conditions, the detection linear range for ESS is 4 × 10 -12 to 6 × 10 -9  M with a limit of detection of 1.18 × 10 -12  M (S/N = 3). In addition, the sensor exhibits high binding affinity toward ESS over its structural analogues with excellent repeatability and stability. The fabricated MIP/CPE was then successfully employed to detect ESS in pregnant mare urine (PMU) without any pretreatment, and the average recoveries were from 99.6 to 104.9% with relative standard deviation less than 3.0%. High-performance liquid chromatography was adopted as a reference to validate the established approach in detecting ESS and their results showed good agreement. The as-prepared sensor has high potential to be a decent tool for on-site determination of ESS in PMU in a fast and convenient manner. Graphical Abstract ᅟ.

  9. Optimising carbon electrode materials for adsorptive stripping voltammetry

    OpenAIRE

    Chaisiwamongkhol, K; Batchelor-McAuley, C; Sokolov, S; Holter, J; Young, N; Compton, R

    2017-01-01

    Different types of carbon electrode materials for adsorptive stripping voltammetry are studied through the use of cyclic voltammetry. Capsaicin is utilised as a model compound for adsorptive stripping voltammetry using unmodified and modified basal plane pyrolytic graphite (BPPG) electrodes modified with multi-walled carbon nanotubes, carbon black or graphene nanoplatelets, screen printed carbon electrodes (SPE), carbon nanotube modified screen printed electrodes, and carbon paste electrodes....

  10. Enzymatic activity of Glucose Oxidase from Aspergillus niger IPBCC.08.610 On Modified Carbon Paste Electrode as Glucose Biosensor

    Science.gov (United States)

    Rohmayanti, T.; Ambarsari, L.; Maddu, A.

    2017-03-01

    Glucose oxidase (GOx) has been developed as glucose sensor for measuring blood glucose level because of its specificity to glucose oxidation. This research aimed to determine kinetic parameters of GOx activity voltametrically and further test its potential as a glucose biosensor. GOx, in this research, was produced by local fungi Aspergillus niger IPBCC.08.610 which was isolated from local vine in Tarakan, East Borneo, Indonesia. GOx was immobilized with glutaraldehyde, which cross-linked onto modified carbon paste electrode (MCPE) nanofiber polyaniline. Intracellular GOx activity was higher than extracellular ones. Immobilized GOx used glutaraldehyde 2.5% and dripped on the surface of MCPE nanofiber polyaniline. MCPE have a high conductance in copper with the diameter of 3 mm. The concentration of glucose in the lowest concentration of 0.2 mM generated a current value of 0.413 mA while 2 mM of glucose induced a current of 3,869 mA value. Km and Imax of GOx in MCPE activities polyaniline nanofiber were 2.88 mM and 3.869 mA,respectively, with turnover (Kcat) of 13 s-1. Sensitivity was 1.09 mA/mM and response time to produce a maximum peak current was 25 seconds. Km value was then converted into units of mg/dL and obtained 56.4 mg/dL. GOximmo-IPB|MCPE electrode is potential to be able to detect blood glucose level in a normal condition and hypoglycemia conditions

  11. Multiwall carbon nanotubes chemically modified carbon paste electrodes for determination of gentamicin sulfate in pharmaceutical preparations and biological fluids

    Energy Technology Data Exchange (ETDEWEB)

    Khalil, M.M., E-mail: magdy_mmagdy@yahoo.com; Abed El-aziz, G.M., E-mail: Gamal_abedelaziz@yahoo.com

    2016-02-01

    This article focused on the construction and characteristics of novel and sensitive gentamicin carbon paste electrodes which are based on the incorporation of multiwall carbon nanotubes (MWCNTs) which improve the characteristics of the electrodes. The electrodes were constructed based on gentamicin-phosphotungstate (GNS-PTA) called CPE{sub 1}, gentamicin-phosphomolybdate (GNS-PMA) called CPE{sub 2}, GNS-PTA + MWMCNTs called MWCPE{sub 1}, and GNS-PMA + MWMCNTs called MWCPE{sub 2}. The constructed electrodes, at optimum paste composition, exhibited good Nernstian response for determination of gentamicin sulfate (GNS) over a linear concentration range from 2.5 × 10{sup −6} to 1 × 10{sup −2}, 3.0 × 10{sup −6} to 1 × 10{sup −2}, 4.9 × 10{sup −7} to 1 × 10{sup −2} and 5.0 × 10{sup −7} to 1 × 10{sup −2} mol L{sup −1}, with lower detection limit 1 × 10{sup −6}, 1 × 10{sup −6}, 1.9 × 10{sup −7} and 2.2 × 10{sup −7} mol L{sup −1}, and with slope values of 29.0 ± 0.4, 29.2 ± 0.7, 31.2 ± 0.5 and 31.0 ± 0.6 mV/decade for CPE{sub 1}, CPE{sub 2}, MWCPE{sub 1} and MWCPE{sub 2}, respectively. The response of electrodes is not affected by pH in the range 3–8 for CPE{sub 1} and CPE{sub 2} and in the range 2.5–8.5 for MWCPE{sub 1} and MWCPE{sub 2}. The results showed fast dynamic response time (about 8–5 s) and long lifetime (more than 2 months) for all electrodes. The sensors showed high selectivity for gentamicin sulfate (GNS) with respect to a large number of interfering species. The constructed electrodes were successfully applied for determination of GNS in pure form, its pharmaceutical preparations and biological fluids using standard addition and potentiometric titration methods with high accuracy and precision. - Graphical abstract: The incorporation of MWCNTs in paste composition improves the characteristics of the MWCPE electrodes which show better responses in terms of sensitivity, Nernstian slope, linear range, faster

  12. Molecularly imprinted polymer based electrochemical detection of L-cysteine at carbon paste electrode.

    Science.gov (United States)

    Aswini, K K; Vinu Mohan, A M; Biju, V M

    2014-04-01

    A methacrylic acid (MAA) based molecularly imprinted polymer (MIP) modified carbon paste electrode (CPE) was developed for electrochemical detection of L-cysteine (Cys). Characterisation of MIP was done with FTIR and the modified electrode with cyclic voltammetry (CV) and differential pulse voltammetry (DPV). CV, DPV and impedance analysis demonstrated that the modified electrode is responsive towards the target molecule. The optimum percentage composition of MIP for MIP/CPE and the effect of pH towards the electrode response for Cys were studied. The detection of Cys in the range of 2×10(-8) to 18×10(-8)M at MIP/CPE was monitored by DPV with a limit of detection of 9.6nM and R(2) of 0.9974. Also, various physiological interferents such as ascorbic acid, L-tryptophan, D-glucose, D-cysteine and L-cysteine were found to have little effect on DPV response at MIP/CPE. The utility of the electrode was proved by the effective detection of Cys from tap water and human blood plasma samples with reproducible results. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Synthesis and characterization of nanohybrid of montmorillonite and zinc oxide

    International Nuclear Information System (INIS)

    Chagas, Beatriz S.; Mendes, Luis C.; Brito, Alice S.

    2009-01-01

    Zinc oxide-aluminosilicate nanohybrids through a hydrothermal reaction of a colloidal suspension of exfoliated montmorillonite nanosheets and zinc oxide in acid solution, performed in three different routes, were synthesized. The products were characterized by wide angle X-ray diffraction (WAXD). In all routes, it was found that the intercalation of zinc oxide into the host montmorillonite gallery was successfully performed so that the crystalline peaks of the montmorillonite and zinc oxide were suppressed from the X-ray patterns. The use of ultrasound decreased the reaction time.(author)

  14. Novel applications of locally sourced montmorillonite (MMT) clay as ...

    African Journals Online (AJOL)

    This work explores the application of a locally sourced raw material, montmorillonite (MMT) clay, as a disintegrant in the formulation of an analgesic pharmaceutical product - paracetamol. The raw MMT was refined and treated with 0.IM NaCl to yield sodium montmorillonite (NaMMT) and the powder properties established in ...

  15. Polyaniline nanocomposites via in situ emulsion polymerization based on montmorillonite: Preparation and characterization

    Directory of Open Access Journals (Sweden)

    M.A. Abd El-Ghaffar

    2015-11-01

    Full Text Available Polyaniline nanocomposites were prepared via in situ emulsion polymerization in the presence of Na+ montmorillonite (Na+MMT. For achieving this purpose the clay was organophilized to (MMT-CTA form using cetyltrimethyl ammonium bromide (CTAB. The X-ray diffraction (XRD demonstrated that the basal space of Na+-montmorillonite increased after the organophilization from 11.21 to 19.35 Å. Polyaniline/montmorillonite (PAn/MMT nanocomposites were prepared by intercalating the emulsion of aniline monomer with treated organically layers of (Na+-MMT using ammonium peroxydisulfate (APS as an initiator. Furthermore aniline hydrochloride (AnHCl was used as a modifier and monomer to prepare PAn/H+MMT nanocomposites by cation exchange of the anilinuim moiety with the sodium ion inside the basal spaces which enlarged after the polymerization process to 35 Å as evidenced from X-ray diffraction (XRD. The d-spacing of the PAn/H+-MMT nanocomposite was found to become wider about 23.79 Å than that of the pure Na+-MMT, and successful intercalation or exfoliation of PAnH+ into Na+-MMT layers. The prepared PAn/MMT nanocomposites were characterized by thermal gravimetric analysis (TGA, scanning electron microscope (SEM, and transmission electron microscope (TEM. The electrical property measurements showed an enhancement in the conductivity values of the prepared nanocomposites especially on using AnHCl monomer to be in the order of 10−1 S/cm.

  16. Electrochemical sensing of etoposide using carbon quantum dot modified glassy carbon electrode.

    Science.gov (United States)

    Nguyen, Hoai Viet; Richtera, Lukas; Moulick, Amitava; Xhaxhiu, Kledi; Kudr, Jiri; Cernei, Natalia; Polanska, Hana; Heger, Zbynek; Masarik, Michal; Kopel, Pavel; Stiborova, Marie; Eckschlager, Tomas; Adam, Vojtech; Kizek, Rene

    2016-04-25

    In this study, enhancement of the electrochemical signals of etoposide (ETO) measured by differential pulse voltammetry (DPV) by modifying a glassy carbon electrode (GCE) with carbon quantum dots (CQDs) is demonstrated. In comparison with a bare GCE, the modified GCE exhibited a higher sensitivity towards electrochemical detection of ETO. The lowest limit of detection was observed to be 5 nM ETO. Furthermore, scanning electron microscopy (SEM), fluorescence microscopy (FM), and electrochemical impedance spectroscopy (EIS) were employed for the further study of the working electrode surface after the modification with CQDs. Finally, the GCE modified with CQDs under optimized conditions was used to analyse real samples of ETO in the prostate cancer cell line PC3. After different incubation times (1, 3, 6, 9, 12, 18 and 24 h), these samples were then prepared prior to electrochemical detection by the GCE modified with CQDs. High performance liquid chromatography with an electrochemical detection method was employed to verify the results from the GCE modified with CQDs.

  17. Salinity dependence of 226Ra adsorption on montmorillonite and kaolinite

    International Nuclear Information System (INIS)

    Shuji Tamamura; Takahiro Takada; Seiya Nagao; Masayoshi Yamamoto; Keisuke Fukushi

    2014-01-01

    The effect of NaCl concentration (10.0-1,000 mM) on 226 Ra adsorption was investigated in the presence of montmorillonite and kaolinite. A positive correlation was observed between the dissolved 226 Ra and NaCl concentrations in the presence of these adsorbents. Distribution coefficients decreased from the order of 10 4 to 10 0 (mL g -1 ) with an increase in NaCl concentration. Although the coefficients were higher for montmorillonite than kaolinite at lower NaCl concentrations, the trend was reversed at higher NaCl concentrations (≥500 mM) owing to the sharper reduction of the coefficient for montmorillonite with the increase in NaCl concentration. The rapid reduction was ascribed to higher negative charge density of montmorillonite, which leads the Ra 2+ adsorption mechanism to approach charge-compensating ion exchange. (author)

  18. Copper nanoparticle modified carbon electrode for determination of dopamine

    International Nuclear Information System (INIS)

    Oztekin, Yasemin; Tok, Mutahire; Bilici, Esra; Mikoliunaite, Lina; Yazicigil, Zafer; Ramanaviciene, Almira; Ramanavicius, Arunas

    2012-01-01

    This paper reports the synthesis and characterization of copper nanoparticles (CuNPs) and application of copper nanoparticle-modified glassy carbon electrode for the electrochemical determination of dopamine. Electrochemical measurements were performed using differently modified glassy carbon (GC) electrodes. Bare, oxidized before modification and copper nanoparticle-modified glassy carbon electrodes (bare-GC, ox-GC and CuNP/GC electrodes, respectively) were characterized by cyclic voltammetry and electrochemical impedance spectroscopy in the presence of redox probes. Atomic force microscopy was used for the visualization of electrode surfaces. The CuNP/GC electrode was found to be suitable for the selective determination of dopamine even in the presence of ascorbic acid, uric acid, and p-acetamidophenol. The observed linear range of CuNP/GC for dopamine was from 0.1 nM to 1.0 μM while the detection limit was estimated to be 50 pM. It was demonstrated that here reported glassy carbon electrode modified by copper nanoparticles is suitable for the determination of dopamine in real samples such as human blood serum.

  19. Modified glassy carbon electrodes based on carbon nanostructures for ultrasensitive electrochemical determination of furazolidone.

    Science.gov (United States)

    Shahrokhian, Saeed; Naderi, Leila; Ghalkhani, Masoumeh

    2016-04-01

    The electrochemical behavior of Furazolidone (Fu) was investigated on the surface of the glassy carbon electrode modified with different carbon nanomaterials, including carbon nanotubes (CNTs), carbon nanoparticles (CNPs), nanodiamond-graphite (NDG), graphene oxide (GO), reduced graphene oxide (RGO) and RGO-CNT hybrids (various ratios) using linear sweep voltammetry (LSV). The results of voltammetric studies exhibited a considerable increase in the cathodic peak current of Fu at the RGO modified GCE, compared to other modified electrodes and also bare GCE. The surface morphology and nature of the RGO film was thoroughly characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The modified electrode showed two linear dynamic ranges of 0.001-2.0 μM and 2.0-10.0 μM with a detection limit of 0.3 nM for the voltammetric determination of Fu. This sensor was used successfully for Fu determination in pharmaceutical and clinical preparations. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. mwnts composite film modified glassy carbon electrode

    African Journals Online (AJOL)

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    ABSTRACT: A poly p-aminosalicylic acid (Poly(p-ASA)) and multiwall carbon nanotubes. (MWCNTs) composite modified glassy carbon (GC) electrode was constructed by casting the MWNTs on the GC electrode surface followed by electropolymerization of the p-ASA on the MWCNTs/GCE. The electrochemical behaviours ...

  1. Carbon nanofiber vs. carbon microparticles as modifiers of glassy carbon and gold electrodes applied in electrochemical sensing of NADH.

    Science.gov (United States)

    Pérez, Briza; Del Valle, Manel; Alegret, Salvador; Merkoçi, Arben

    2007-12-15

    Carbon materials (CMs), such as carbon nanotubes (CNTs), carbon nanofibers (CNFs), and carbon microparticles (CMPs) are used as doping materials for electrochemical sensors. The efficiency of these materials (either before or after acidic treatments) while being used as electrocatalysts in electrochemical sensors is discussed for beta-nicotinamide adenine dinucleotide (NADH) detection using cyclic voltammetry (CV). The sensitivity of the electrodes (glassy carbon (GC) and gold (Au)) modified with both treated and untreated materials have been deeply studied. The response efficiencies of the GC and Au electrodes modified with CNF and CMP, using dimethylformamide (DMF) as dispersing agent are significantly different due to the peculiar physical and chemical characteristics of each doping material. Several differences between the electrocatalytic activities of CMs modified electrodes upon NADH oxidation have been observed. The CNF film promotes better the electron transfer of NADH minimizing the oxidation potential at +0.352 V. Moreover higher currents for the NADH oxidation peak have been observed for these electrodes. The shown differences in the electrochemical reactivities of CNF and CMP modified electrodes should be with interest for future applications in biosensors.

  2. Simultaneous voltammetric determination of dopamine and ascorbic acid using multivariate calibration methodology performed on a carbon paste electrode modified by a mer-[RuCl3(dppb)(4-pic)] complex

    International Nuclear Information System (INIS)

    Santos, Poliana M.; Sandrino, Bianca; Moreira, Tiago F.; Wohnrath, Karen; Nagata, Noemi; Pessoa, Christiana A.

    2007-01-01

    The preparation and electrochemical characterization of a carbon paste electrode (CPE) modified with mer-[Ru0Cl 3 (dppb)(4-pic)] (dppb=Ph 2 P(CH 2 ) 4 PPh 2 , 4-pic=CH 3 C 5 H 4 N), referred to as Rupic, were investigated. The CPE/Rupic system displayed only one pair of redox peaks, with a midpoint potential at 0.28 V vs. Ag/AgCl, which were ascribed to Ru III /Ru II charge transfer. This modified electrode presented the property of electrocatalysing the oxidation of dopamine (DA) and ascorbic acid (AA) at 0.35 V and 0.30 V vs. Ag/AgCl, respectively. Because the oxidation for both AA and DA practically occurred at the same potential, distinguishing between them was difficult with cyclic voltammetry. This limitation was overcome using Partial Least Square Regression (PLSR), which allowed us, with the optimised models, to determine four synthetic samples with prediction errors (RMSEP) of 5.55 X 10 -5 mol L -1 and 7.48 X 10 -6 mol L -1 for DA and AA, respectively. (author)

  3. The electrochemical behavior of Co(TPTZ)2 complex on different carbon based electrodes modified with TiO2 nanoparticles

    International Nuclear Information System (INIS)

    Ortaboy, Sinem; Atun, Gülten

    2015-01-01

    Electrochemical behavior of cobalt (II) complex with the N-donor ligand 2,2′-bipyridyl-1,3,5-tripyridyl-s-triazine (TPTZ) was investigated to elucidate the electron-proton transfer mechanisms. The electrochemical response of the complex was studied using square-wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) techniques. A conventional three-electrode system, consisting of glassy carbon (GCE), TiO 2 modified glassy carbon (T/GCE), carbon paste (CPE) and TiO 2 modified carbon paste (T/CPE) working electrodes were employed. The ligand/metal ratio and stability constant of the complex as well as the mechanisms of the electrode processes were elucidated by examining the effects of pH, ligand concentration and frequency on the voltammograms. The EIS results indicated that the samples modified with TiO 2 had the higher charge transfer resistance than that of the bare electrodes and also suggested that the electroactivity of the electrode surfaces increased in the following order, T/CPE > CPE > T/GCE > GCE. The surface morphology of the working electrodes was also characterized by atomic force microscopy (AFM). The values of surface roughness parameters were found to be consistent with the results obtained by EIS experiments. - Graphical abstract: Schematic illustration of the experimental process. - Highlights: • Electrochemical behavior of Co(TPTZ) 2 complex studied by SWV and EIS techniques. • GCE, CPE T/GCE and T/CPE were used as working electrodes for comparative studies. • The surface morphologies of the electrodes were characterized by AFM. • Mechanisms were proposed from the effects of pH, ligand concentration and frequency. • EIS and morphologic relationships of the surfaces were established successfully

  4. Ionic liquid-functionalized graphene as modifier for electrochemical and electrocatalytic improvement: comparison of different carbon electrodes.

    Science.gov (United States)

    Du, Meng; Yang, Tao; Ma, Suyan; Zhao, Changzhi; Jiao, Kui

    2011-04-01

    Electrochemical activities of typically electrochemical targets at three kinds of modified carbon electrodes, i.e. carbon ionic liquid electrode (CILE), graphene/carbon paste electrode (CPE), and ionic liquid-functionalized graphene (IL-graphene)/CPE, were compared in detail. The redox processes of the probes at IL-graphene/CPE were faster than those at CILE and graphene/CPE from cyclic voltammetry. An electrochemical method for the simultaneous determination of guanine and adenine was described with detection limits of 6.5×10(-8) mol L(-1) (guanine) and 3.2×10(-8) mol L(-1) (adenine). Single A→G mutation of sequence-specific DNA could be discriminated by the IL-graphene/CPE. Copyright © 2011 Elsevier B.V. All rights reserved.

  5. Adsorption of ferrous ions onto montmorillonites

    Science.gov (United States)

    Qin, Dawei; Niu, Xia; Qiao, Min; Liu, Gang; Li, Hongxin; Meng, Zhenxiao

    2015-04-01

    The adsorption of Fe (II) onto montmorillonites was investigated through initial concentration, contact time, pH and temperature. During the whole adsorption process, the ascorbic acid (Vitamin C) was added as a kind of antioxidant, at the same time, deionized water (after boiling) and nitrogen protection were also used to avoid oxidation. The Fe2+/Fetotal ratio of the iron exists in the Fe-montmorillonites was found more than 95%. Two kinetic models, including pseudo-first-order and pseudo-second-order model, were used to analyze the adsorption process of Fe (II) on montmorillonites. The results of our study showed that adsorption process fitted with pseudo-second-order well. Adsorption isotherms showed that Langmuir model was better than Freundlich model. The thermodynamic parameters ΔG0 and ΔH0 were 3.696 kJ/mol and 6.689 kJ/mol (we just gave the values at 298 K), respectively. The positive values at different temperatures showed that the adsorption process was non-spontaneous and endothermic. The characteristics of materials were determined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Surface area and porosity analyzer, Thermogravimetric analysis (TGA), Differential scanning calorimeter (DSC) and Zeta potential distribution.

  6. Sulfation of CaO particles in a carbonation/calcination loop to capture CO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Grasa, G.S.; Alonso, M.; Abanades, J.C. [CSIC, Zaragoza (Spain)

    2008-03-15

    CaO is being proposed as a regenerable sorbent of CO{sub 2} via a carbonation/calcination loop. It is well known that natural sorbents lose their capacity to capture CO{sub 2} with the number of cycles due to textural degradation. In coal combustion systems, reaction with the SO{sub 2} present in flue gases also causes sorbent deactivation. This work investigates the effect of partial sorbent sulfation on the amount of CaO used in systems where both carbonation and sulfation reactions are competing. We have found that SO{sub 2} reacts with the deactivated CaO resulting from repetitive calcination/carbonation reactions. Therefore, the deactivation of CaO as a result of the presence of SO{sub 2} is lower than one would expect if one assumes that SO{sub 2} reacts only with active CaO. This work shows that changes in the texture of the sorbent due to repetitive carbonation/calcination cycles tend to increase the sulfation capacity of the sorbents tested. This suggests that the purge of deactivated CaO obtained from a CO{sub 2} capture loop could be a more effective sorbent of SO{sub 2} than fresh CaO.

  7. The Cytoplasmic Carbonic Anhydrases βCA2 and βCA4 Are Required for Optimal Plant Growth at Low CO2.

    Science.gov (United States)

    DiMario, Robert J; Quebedeaux, Jennifer C; Longstreth, David J; Dassanayake, Maheshi; Hartman, Monica M; Moroney, James V

    2016-05-01

    Carbonic anhydrases (CAs) are zinc metalloenzymes that interconvert CO2 and HCO3 (-) In plants, both α- and β-type CAs are present. We hypothesize that cytoplasmic βCAs are required to modulate inorganic carbon forms needed in leaf cells for carbon-requiring reactions such as photosynthesis and amino acid biosynthesis. In this report, we present evidence that βCA2 and βCA4 are the two most abundant cytoplasmic CAs in Arabidopsis (Arabidopsis thaliana) leaves. Previously, βCA4 was reported to be localized to the plasma membrane, but here, we show that two forms of βCA4 are expressed in a tissue-specific manner and that the two proteins encoded by βCA4 localize to two different regions of the cell. Comparing transfer DNA knockout lines with wild-type plants, there was no reduction in the growth rates of the single mutants, βca2 and βca4 However, the growth rate of the double mutant, βcaca4, was reduced significantly when grown at 200 μL L(-1) CO2 The reduction in growth of the double mutant was not linked to a reduction in photosynthetic rate. The amino acid content of leaves from the double mutant showed marked reduction in aspartate when compared with the wild type and the single mutants. This suggests the cytoplasmic CAs play an important but not previously appreciated role in amino acid biosynthesis. © 2016 American Society of Plant Biologists. All Rights Reserved.

  8. Spatial Associations and Chemical Composition of Organic Carbon Sequestered in Fe, Ca, and Organic Carbon Ternary Systems.

    Science.gov (United States)

    Sowers, Tyler D; Adhikari, Dinesh; Wang, Jian; Yang, Yu; Sparks, Donald L

    2018-05-25

    Organo-mineral associations of organic carbon (OC) with iron (Fe) oxides play a major role in environmental OC sequestration, a process crucial to mitigating climate change. Calcium has been found to have high coassociation with OC in soils containing high Fe content, increase OC sorption extent to poorly crystalline Fe oxides, and has long been suspected to form bridging complexes with Fe and OC. Due to the growing realization that Ca may be an important component of C cycling, we launched a scanning transmission X-ray microscopy (STXM) investigation, paired with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, in order to spatially resolve Fe, Ca, and OC relationships and probe the effect of Ca on sorbed OC speciation. We performed STXM-NEXAFS analysis on 2-line ferrihydrite reacted with leaf litter-extractable dissolved OC and citric acid in the absence and presence of Ca. Organic carbon was found to highly associate with Ca ( R 2 = 0.91). Carboxylic acid moieties were dominantly sequestered; however, Ca facilitated the additional sequestration of aromatic and phenolic moieties. Also, C NEXAFS revealed polyvalent metal ion complexation. Our results provide evidence for the presence of Fe-Ca-OC ternary complexation, which has the potential to significantly impact how organo-mineral associations are modeled.

  9. Effect of carbonation temperature on CO_2 adsorption capacity of CaO derived from micro/nanostructured aragonite CaCO_3

    International Nuclear Information System (INIS)

    Hlaing, Nwe Ni; Sreekantan, Srimala; Hinode, Hirofumi; Kurniawan, Winarto; Thant, Aye Aye; Othman, Radzali; Mohamed, Abdul Rahman; Salime, Chris

    2016-01-01

    Recent years, CaO-based synthetic materials have been attracted attention as potential adsorbents for CO_2 capture mainly due to their high CO_2 adsorption capacity. In this study, micro/nanostructured aragonite CaCO_3 was synthesized by a simple hydrothermal method with using polyacrylamide (PAM). The structural, morphological and thermal properties of the synthesized sample were investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and thermogravimetry analysis (TG-DTA). The XRD and FESEM results showed that the obtained sample was aragonite CaCO_3 with aggregated nanorods and microspheres composed of nanorods. A TG-DTA apparatus with Thermoplus 2 software was used to investigate the effect of carbonation temperature on the CO_2 adsorption capacity of CaO derived from aragonite CaCO_3 sample. At 300 °C, the sample reached the CO_2 adsorption capacity of 0.098 g-CO_2/g-adsorbent, whereas the sample achieved the highest capacity of 0.682 g-CO_2/g-adsorbent at 700 °C. The results showed that the carbonation temperature significantly influenced on the CO_2 adsorption capacity of the CaO derived from aragonite CaCO_3.

  10. Simultaneous carbonation and sulfation of CaO in Oxy-Fuel CFB combustion

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C. [School of Energy and Power Engineering, North China Electric Power University, Baoding City, Hebei Province (China); Jia, L.; Tan, Y. [CanmetENERGY, 1 Haanel Drive, Ottawa, Ontario, K1A 1M1 (Canada)

    2011-10-15

    For anthracites and petroleum cokes, the typical combustion temperature in a circulating fluidized bed (CFB) is > 900 C. At CO{sub 2} concentrations of 80-85 % (typical of oxy-fuel CFBC conditions), limestone still calcines. When the ash which includes unreacted CaO cools to the calcination temperature, carbonation of fly ash deposited on cool surfaces may occur. At the same time, indirect and direct sulfation of limestone also will occur, possibly leading to more deposition. In this study, CaO was carbonated and sulfated simultaneously in a thermogravimetric analyzer (TGA) under conditions expected in an oxy-fuel CFBC. It was found that temperature, and concentrations of CO{sub 2}, SO{sub 2}, and especially H{sub 2}O are important factors in determining the carbonation/sulfation reactions of CaO. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Immobilization of metallothionein to carbon paste electrode surface via anti-MT antibodies and its use for biosensing of silver.

    Science.gov (United States)

    Trnkova, Libuse; Krizkova, Sona; Adam, Vojtech; Hubalek, Jaromir; Kizek, Rene

    2011-01-15

    In this paper, heavy metal biosensor based on immobilization of metallothionein (MT) to the surface of carbon paste electrode (CPE) via anti-MT-antibodies is reported. First, the evaluation of MT electroactivity was done. The attention was focused on the capturing of MT to the CPE surface. Antibodies incorporated and mixed into carbon paste were stable; even after two weeks the observed changes in signal height were lower than 5%. Further, the interaction of MT with polyclonal chicken antibodies incorporated in carbon paste electrode was determined by square-wave voltammetry. In the voltammogram, two signals--labelled as cys(MT) and W(a)--were observed. The cys(MT) corresponded to -SH moieties of MT and W(a) corresponded to tryptophan residues of chicken antibodies. Time of interaction (300 s) and MT concentration (125 μg/ml) were optimized to suggest a silver(I) ions biosensor. Biosensor (CPE modified with anti-MT antibody) prepared under the optimized conditions was then used for silver(I) ions detection. The detection limit (3 S/N) for silver(I) ions was estimated as 0.5 nM. The proposed biosensor was tested by detection spiking of silver(I) ions in various water samples (from very pure distilled water to rainwater). Recoveries varied from 74 to 104%. Copyright © 2010 Elsevier B.V. All rights reserved.

  12. Past and present of sediment and carbon biogeochemical cycling models

    Directory of Open Access Journals (Sweden)

    F. T. Mackenzie

    2004-01-01

    Full Text Available The global carbon cycle is part of the much more extensive sedimentary cycle that involves large masses of carbon in the Earth's inner and outer spheres. Studies of the carbon cycle generally followed a progression in knowledge of the natural biological, then chemical, and finally geological processes involved, culminating in a more or less integrated picture of the biogeochemical carbon cycle by the 1920s. However, knowledge of the ocean's carbon cycle behavior has only within the last few decades progressed to a stage where meaningful discussion of carbon processes on an annual to millennial time scale can take place. In geologically older and pre-industrial time, the ocean was generally a net source of CO2 emissions to the atmosphere owing to the mineralization of land-derived organic matter in addition to that produced in situ and to the process of CaCO3 precipitation. Due to rising atmospheric CO2 concentrations because of fossil fuel combustion and land use changes, the direction of the air-sea CO2 flux has reversed, leading to the ocean as a whole being a net sink of anthropogenic CO2. The present thickness of the surface ocean layer, where part of the anthropogenic CO2 emissions are stored, is estimated as of the order of a few hundred meters. The oceanic coastal zone net air-sea CO2 exchange flux has also probably changed during industrial time. Model projections indicate that in pre-industrial times, the coastal zone may have been net heterotrophic, releasing CO2 to the atmosphere from the imbalance between gross photosynthesis and total respiration. This, coupled with extensive CaCO3 precipitation in coastal zone environments, led to a net flux of CO2 out of the system. During industrial time the coastal zone ocean has tended to reverse its trophic status toward a non-steady state situation of net autotrophy, resulting in net uptake of anthropogenic CO2 and storage of carbon in the coastal ocean, despite the significant calcification

  13. Electrochemical evaluation of the a carbon-paste electrode modified with spinel manganese(IV) oxide under flow conditions for amperometric determination of lithium

    International Nuclear Information System (INIS)

    Raymundo-Pereira, Paulo A.; Martin, Cibely S.; Bergamini, Marcio F.; Bocchi, Nerilso; Teixeira, Marcos F.S.

    2011-01-01

    The participation of cations in redox reactions of manganese oxides provides an opportunity for development of chemical sensors for non-electroactive ions. This paper describes the amperometric determination of lithium ions using carbon-paste electrode modified with spinel manganese(IV) oxide under flow conditions. Systematic investigations were made to optimize the experimental parameters for lithium sensor by flow injection analysis. The detection was based on the measurement of anodic current generated by oxidation of Mn(III) to Mn(IV) at the surface of the electrode and consequently the lithium ions extraction into the spinel structure. An operating potential of 0.50 V (vs. Ag/AgCl/3 KCl mol/L) was exploited for amperometric monitoring. The amperometric signal was linearly dependent on the lithium ions concentration over the range 4.0 x 10 -5 to 1.0 x 10 -3 mol L -1 . The equilibrium constant of insertion/extraction of the lithium ion in the spinel structure, apparent Gibbs energy of insertion, and surface coverage of the electrode with manganese oxide, were calculated by peak charge (Q) in different concentration under flow conditions. Considering selectivity, the peak charge of the sensor was found to be linearly dependent on the ionic radius of the alkaline and earth-alkaline cations.

  14. Thermal and Electrical Characterization of the Carbon Nanofibers Based Cement Composites

    Directory of Open Access Journals (Sweden)

    Agnieszka ŚLOSARCZYK

    2017-08-01

    Full Text Available The paper describes the influence of chemical modification of vapor grown carbon nanofibers (VGCnFs on the thermal and electrical properties of the cement composites. The surface modification of nanofibers was performed by means of ozone and nitric acid treatments. It was shown that the oxidized carbon nanofibers surface plays an important role in shaping the mechanical and especially electrical properties of cement composite. For cement matrix modified with carbon nanofibers subjected to oxidized treatment, the slightly increase of cement paste resistivity was observed. It confirms the better adhesion of carbon nanofibers to cement paste. However, independently of carbon nanofibers modification, the occurrence of VGCnFs in cement paste increased the electrical conductivity of the composite in comparison to the cement paste without fibers. The obtained values of electrical resistivity were comparable with values of cement composites modified with 4 mm long carbon fibers. Moreover, it was shown that the chemical modification of carbon nanofibers surface does not influence on the thermal properties of cement composites. In case of cement paste with unmodified and modified carbon nanofibers, the Seebeck voltage was proportional to the temperature difference and was independent of the oxidation degree of carbon nanofibers.DOI: http://dx.doi.org/10.5755/j01.ms.23.2.14993

  15. Nanomolar simultaneous determination of tryptophan and melatonin by a new ionic liquid carbon paste electrode modified with SnO2-Co3O4@rGO nanocomposite.

    Science.gov (United States)

    Zeinali, Homa; Bagheri, Hasan; Monsef-Khoshhesab, Zahra; Khoshsafar, Hosein; Hajian, Ali

    2017-02-01

    This work describes the development of a new sensor for simultaneous determination of tryptophan and melatonin. The proposed sensor was an ionic liquid carbon paste electrode modified with reduced graphene oxides decorated with SnO 2 -Co 3 O 4 nanoparticles. The voltammetric oxidation of the analytes by the proposed sensor confirmed that the electrooxidation process undergoes a two-electron/one-proton reaction for melatonin and a two-electron/two-proton reaction for tryptophan in diffusion-controlled processes. Moreover, based on the excellent electrochemical properties of the modified electrode, a sensitive voltammetric method was used for individual and simultaneous determination of melatonin and tryptophan in the aqueous solutions. Under the optimized experimental conditions, a linear response obtained in the range of 0.02 to 6.00μmolL -1 with detection limits of 4.1 and 3.2nmolL -1 for melatonin and tryptophan, respectively. The prepared sensor possessed accurate and rapid response toward melatonin and tryptophan with a good sensitivity, selectivity, stability, and repeatability. Finally, the applicability of the proposed sensor was verified by evaluation of melatonin and tryptophan in various real samples including human serum and tablet samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. A new sensor based on glassy carbon electrode modified with nanocomposite for simultaneous determination of acetaminophen, ascorbic acid and uric acid

    Directory of Open Access Journals (Sweden)

    Mohammad Afrasiabi

    2016-09-01

    Full Text Available A chemically-modified electrode has been constructed based on a single walled carbon nanotube/chitosan/room temperature ionic liquid nanocomposite modified glassy carbon electrode (SWCNTs–CHIT–RTIL/GCE. It was demonstrated that this sensor could be used for simultaneous determination of acetaminophen (ACT, uric acid (URI and ascorbic acid (ASC. The measurements were carried out by application of differential pulse voltammetry (DPV, cyclic voltammetry (CV and chronoamperometry (CA methods. Electrochemical studies suggested that the RTIL and SWCNTs provided a synergistic augmentation that can increase current responses by improvement of electron transfers of these compounds on the electrode surface. The presence of the CHIT in the modified electrode can enhance the repeatability of the sensor by its antifouling effect. The modified electrode showed electrochemical responses with high sensitivity for ACT, URI and ASC determination, which makes it a suitable sensor for simultaneous sub-μmol L−1 detection of ACT, URI and ASC in aqueous solutions. The analytical performance of this sensor has been evaluated for detection of ACT, URI and ASC in human serum and urine with satisfactory results.

  17. Drastic lake level changes of Lake Van (eastern Turkey) during the past ca. 600 ka: climatic, volcanic and tectonic control

    Science.gov (United States)

    Cukur, D.; Krastel, S.; Schmincke, H.; Sumita, M.; Tomonaga, Y.; Damci, E.

    2013-12-01

    Lake Van is the largest soda lake in the world with a present surface of 3,574 km2 and a maximum water depth of 450 m. Sedimentary deposits in the lake preserve one of the most complete record of continental climate in the Middle East since the Middle Pleistocene. We studied these deposits to characterize the evolution of the lake level and its possible relationships with changes in climate, volcanic, and regional tectonics since the formation of the lake ca. 600 ka ago. Changes in lake level were determined based on high-resolution seismic reflection profiles showing erosional surfaces, changes in stratal geometries such as downward shifts in coastal onlap, and recognition of distinctive stratigraphic features such as prograding delta clinoforms. Our results show that Lake Van has undergone drastic changes in surface elevation by as much as 600 meters over the past ca. 600 ka. Five major lowstands occurred at ca. ~600 ka, ca. 365-340 ka, ca 290-230 ka; ca. 150-130 ka; and ca. 30-14 ka. During a first period (A) (ca. 600-ca 230 ka) lake levels changed drastically by hundreds of m but at longer time intervals between low and high stands. Changes occurred more frequently but mostly by a few tens of m during the past ca. 230 ka years where we can distinguish a first period (B1) of stepwise transgressions between ca. 230 and 150 ka followed by a short regression between ca. 150 and 130 ka. Lake level rose stepwise again during period B2 lasting until ca 30 ka. During the past 30 ka a regression and a final transgression each lasted ca. 15 ka years. The major lowstand periods in Lake Van occurred during glacial periods, arguing for a climatic control of these lake-level fluctuations (i.e., significantly reduced precipitation leading to lake level low stands). Although climate forcing may have been the dominant cause for the drastic lake level changes of Lake Van, volcanic and tectonic forcing factors are also invoked. For example, the number of distinct tephra layers

  18. Cement Pastes and Mortars Containing Nitrogen-Doped and Oxygen-Functionalized Multiwalled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Mauricio Martínez-Alanis

    2016-01-01

    Full Text Available Cement pastes and mortars based on ordinary Portland cement containing nitrogen-doped multiwalled carbon nanotubes (MWCNT-Nx or oxygen-functionalized multiwalled carbon nanotubes (MWCNT-Ox are investigated. To incorporate MWCNTs into the cementitious matrix, the as-produced carpets are dispersed over periods of 1 and 2 hours in distilled water at pH levels of 1 and 7. The cement pastes are prepared by adding 0.1 wt% of MWCNTs to cement powder, followed by characterization with SEM and X-ray diffraction (XRD at an early age (first hours of hydration. The mortars are mechanically characterized during the hydration process for a period of 28 days. SEM characterization of cement pastes revealed that the carbon nanotubes are well incorporated in the cementitious matrix, with the hydrated cement grains interconnected by long carbon nanotubes. XRD characterizations demonstrated that, during the hydration of cement pastes, different peaks emerged that were associated with ettringite, hydrated calcium silicate, and calcium hydroxide, among other structures. Results of the compressive strength measurements for mortars simultaneously mixed with MWCNT-Nx and MWCNT-Ox reached an increment of approximately 30% in compressive strength. In addition, density functional theory calculations were performed in nitrogen-doped and oxygen-functionalized carbon nanotubes interacting with a cement grain.

  19. Mössbauer study of pH dependence of iron-intercalation in montmorillonite

    Energy Technology Data Exchange (ETDEWEB)

    Kuzmann, E., E-mail: kuzmann@caesar.elte.hu [Eötvös Loránd University, Institute of Chemistry (Hungary); Garg, V. K.; Singh, H.; Oliveira, A. C. de; Pati, S. S. [University of Brasília, Institute of Physics (Brazil); Homonnay, Z.; Rudolf, M. [Eötvös Loránd University, Institute of Chemistry (Hungary); Molnár, Á. M.; Kovács, E. M. [University of Debrecen, Imre Lajos Isotope Laboratory, Department of Colloid and Environmental Chemistry (Hungary); Baranyai, E. [University of Debrecen, Department of Inorganic and Analytical Chemistry (Hungary); Kubuki, S. [Tokyo Metropolitan University, Department of Chemistry (Japan); Nagy, N. M.; Kónya, J. [University of Debrecen, Imre Lajos Isotope Laboratory, Department of Colloid and Environmental Chemistry (Hungary)

    2016-12-15

    {sup 57}Fe Mössbauer spectroscopy and XRD have successfully been applied to show the incorporation of Fe ion into the interlayer space of montmorillonite via treatment with FeCl {sub 3} in acetone. The 78K {sup 57}Fe Mössbauer spectra of montmorillonite samples reflected magnetically split spectrum part indicating the intercalation of iron into the interlayer of montmorillonite via the treatment with FeCl {sub 3}+acetone and washed with water until the initial pH=2.3 increased to pH=4.14. It was found that the occurrence of intercalated iron in the form of oxide-oxihydroxide in montmorillonite increases with the pH. Intercalation was confirmed by the gradual increase in the basal spacing d{sub 001} with pH.

  20. Molecular dynamics simulations of the three-layer hydrate of Na-montmorillonite

    International Nuclear Information System (INIS)

    Holmboe, Michael; Bourg, Ian C.

    2012-01-01

    Document available in extended abstract form only. In many nuclear waste repositories concepts, compacted and smectite-rich bentonite clay is considered as an engineered transport barrier surrounding the canisters holding the nuclear waste. One of the requirements in the safety assessment of these repositories is to predict the transport rate of radionuclides as well as the overall hydraulic conductivity through the bentonite barrier. Kozaki and co-workers have obtained important information from diffusion experiments in bentonite on the mechanisms that control solute transport by studying the temperature-dependence of apparent diffusivity for solutes such as Na + , Cs + and Sr 2+ . Their results showed that the apparent diffusivity follows an Arrhenius relation (ln D a ∝ -E A /RT) with distinct activation energies of diffusion (E A ) for certain montmorillonite compactions, ionic strengths, and types of interlayer cation (Na + vs. Ca 2+ ). Their results suggest that solutes follow different diffusion pathways in compacted montmorillonite at different experimental conditions. In order to identify these transport pathways in compacted montmorillonite one needs independent knowledge of the relative abundance of the different types of interlayer nano-pores, i.e. the different coexisting hydration states (1W-3W), and of the molecular-scale EA for solute diffusion on the external basal surfaces of montmorillonite particles and in the interlayer nano-pores. The latter property can be obtained using molecular dynamics (MD) simulations, an important tool in the characterization of clays and clay minerals that yields detailed atomistic insights into the structural, dynamical and thermodynamic properties of many different geochemically relevant systems. In particular, MD simulations yield insight into the behavior of individual atoms, where most experimental methods only would probe the average behavior of large numbers of atoms or molecules. Thus, by simulating systems of

  1. XRD study of intercalation in statically annealed composites of ethylene copolymers and organically modified montmorillonites. 2. One-tailed organoclays

    Directory of Open Access Journals (Sweden)

    Sara Filippi

    2014-01-01

    Full Text Available Ethylene copolymers with different polar comonomers, such as vinyl acetate, methyl acrylate, glycidyl methacrylate, and maleic anhydride, were used for the preparation of polymer/clay nanocomposites by statically annealing their mechanical mixtures with different commercial or home-made organically modified montmorillonites containing only one long alkyl tail. The nanostructure of the products was monitored by X-ray diffraction, and the dispersion of the silicate particles within the polymer matrix was qualitatively evaluated through microscopic analyses. The effect of the preparation conditions on the structure and the morphology of the composites was also addressed through the characterization of selected samples with similar composition prepared by melt compounding. In agreement with the findings reported in a previous paper for the composites filled with two-tailed organoclays, intercalation of the copolymer chains within the tighter galleries of the one-tailed clays occurs easily, independent of the application of a mechanical stress. However, the shear-driven break-up of the intercalated clay particles into smaller platelets (exfoliation seems more hindered. A collapse of the organoclay interlayer spacing was only observed clearly for a commercial one-tailed organoclay – Cloisite® 30B – whereas the same effect was almost negligible for a home-made organoclay with similar structure.

  2. Caffeine adsorption of montmorillonite in coffee extracts.

    Science.gov (United States)

    Shiono, Takashi; Yamamoto, Kenichiro; Yotsumoto, Yuko; Yoshida, Aruto

    2017-08-01

    The growth in health-conscious consumers continues to drive the demand for a wide variety of decaffeinated beverages. We previously developed a new technology using montmorillonite (MMT) in selective decaffeination of tea extract. This study evaluated and compared decaffeination of coffee extract using MMT and activated carbon (AC). MMT adsorbed caffeine without significant adsorption of caffeoylquinic acids (CQAs), feruloylquinic acids (FQAs), dicaffeoylquinic acids (di-CQAs), or caffeoylquinic lactones (CQLs). AC adsorbed caffeine, chlorogenic acids (CGAs) and CQLs simultaneously. The results suggested that the adsorption selectivity for caffeine in coffee extract is higher in MMT than AC. The caffeine adsorption isotherms of MMT in coffee extract fitted well to the Langmuir adsorption model. The adsorption properties in coffee extracts from the same species were comparable, regardless of roasting level and locality of growth. Our findings suggest that MMT is a useful adsorbent in the decaffeination of a wide range of coffee extracts.

  3. Electrochemical investigations of Pu(IV)/Pu(III) redox reaction using graphene modified glassy carbon electrodes and a comparison to the performance of SWCNTs modified glassy carbon electrodes

    International Nuclear Information System (INIS)

    Gupta, Ruma; Gamare, Jayashree; Sharma, Manoj K.; Kamat, J.V.

    2016-01-01

    Highlights: • First report of aqueous electrochemistry of Plutonium on graphene modified electrode. • Graphene is best electrocatalytic material for Pu(IV)/Pu(III) redox couple among the reported modifiers viz. reduced graphene oxide (rGO) and SWCNT’s. • The electrochemical reversibility of Pu(IV)/Pu(III) redox couple improves significantly on graphene modified electrode compared to previously reported rGO & SWCNTs modified electrodes • Donnan interaction between plutonium species and graphene surface offers a possibility for designing a highly sensitive sensor for plutonium • Graphene modified electrode shows higher sensitivity for the determination of plutonium compared to glassy carbon and single walled carbon nanotube modified electrode - Abstract: The work reported in this paper demonstrates for the first time that graphene modified glassy carbon electrode (Gr/GC) show remarkable electrocatalysis towards Pu(IV)/Pu(III) redox reaction and the results were compared with that of single-walled carbon nanotubes modified GC (SWCNTs/GC) and glassy carbon (GC) electrodes. Graphene catalyzes the exchange of current of the Pu(IV)/Pu(III) couple by reducing both the anodic and cathodic overpotentials. The Gr/GC electrode shows higher peak currents (i p ) and smaller peak potential separation (ΔE p ) values than the SWCNTs/GC and GC electrodes. The heterogeneous electron transfer rate constants (k s ), charge transfer coefficients (α) and the diffusion coefficients (D) involved in the electrocatalytic redox reaction were determined. Our observations show that graphene is best electrocatalytic material among both the SWCNTs and GC to study Pu(IV)/Pu(III) redox reaction.

  4. Ca/Na selectivity coefficients from the Poisson-Boltzmann theory

    International Nuclear Information System (INIS)

    Hedstroem, Magnus; Karnland, Ola

    2010-01-01

    Document available in extended abstract form only. A possible scenario in the post-glacial evolution of the bentonite buffer used in a KBS-3 repository for spent nuclear fuel is that parts of the buffer may erode due to sol formation caused by the extensive swelling of, in particular, Na-montmorillonite in water of low ionic strength. Presence of calcium in the interlayer has been shown to promote gel formation even in electrolytes with ionic strengths in the vicinity of those in glacial melt waters. In order to estimate the amount of calcium in the clay at the onset of glaciation one needs information of the selectivity coefficient for Ca/Na exchange. Hitherto, most experimental data for evaluating the Gaines-Thomas selectivity coefficient, K GT have been obtained in batch experiments, i.e. at high water-to-solid ratios. The conditions in highly compacted bentonite are, however, radically different in many respects, e.g. the interlayer space is on the nanometre scale and the concentration of counterions is in molar range. Therefore we would like to theoretically investigate the transferability of the selectivity coefficients, determined in batch experiments, to compacted conditions. We solve the Poisson-Boltzmann (PB) equation for two parallel charged surfaces in equilibrium with an external NaCl/CaCl 2 mixed solution. Integration of the ion concentration profiles obtained from the PB equation gives the occupancy of Na + and Ca 2+ in the clay. That information together with the composition of the external electrolyte is all that is needed for the calculation of K GT . With a surface layer-charge density of one charge per 145 A 2 , which is close to the value for Wyoming montmorillonite, we find a variation of the selectivity coefficient from about 4 M in batch to 8 M for compacted montmorillonite with dry density 1700 kg/m 3 . The significance as well as the physics behind these results will be presented in detail. The predictions, based on the PB theory, will

  5. Magnetic core–shell Fe{sub 3}O{sub 4}@SiO{sub 2}/MWCNT nanocomposite modified carbon paste electrode for amplified electrochemical sensing of uric acid

    Energy Technology Data Exchange (ETDEWEB)

    Arvand, Majid, E-mail: arvand@guilan.ac.ir; Hassannezhad, Morassa

    2014-03-01

    A new type of nanocomposite based on multi-walled carbon nanotubes decorated with magnetic core–shell Fe{sub 3}O{sub 4}@SiO{sub 2} nanoparticles (Fe{sub 3}O{sub 4}@SiO{sub 2}/MWCNTs) was prepared and used to fabricate a modified carbon paste electrode (CPE). The nanocomposite was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FT-IR) techniques. Electrochemical behavior of uric acid (UA) was investigated on Fe{sub 3}O{sub 4}@SiO{sub 2}/MWCNTs-CPE by cyclic voltammetry (CV) and square wave voltammetry (SWV) in phosphate buffer solution (pH 6.0). Under the optimized conditions, the peak currents increased linearly with the concentration of UA in the range from 0.60 to 100.0 μM, with a detection limit of 0.13 μM. The proposed sensor was successfully applied for the determination of UA in biological fluids. - Highlights: • A simple and rapid sensor for determination of UA in human blood serum and urine was prepared. • The Fe{sub 3}O{sub 4}@SiO{sub 2}/MWCNTs-CPE showed an obvious increase in surface area and sensitivity. • The presence of Fe{sub 3}O{sub 4}@SiO{sub 2} nanoparticles showed good ability to distinguish the response of UA.

  6. Precipitation of Nd-Ca carbonate solid solution at 25 degrees C

    International Nuclear Information System (INIS)

    Carroll, S.A.

    1993-01-01

    The formation of a Nd-Ca carbonate solid solution was studied by monitoring the reactions of calcite with aqueous Nd, orthorhombic NdOHCO 3 (s) with aqueous Ca, and calcite with hexagonal Nd-carbonate solid phase as a function of time at 25 degrees C and controlled pCO 2 (g). All experiments reached steady state after 200 h of reaction. The dominant mechanism controlling the formation of the solid solution was precipitation of a Nd-Ca carbonate phase from the bulk solution as individual crystals or at the orthorhombic NdOHCO 3 (s)-solution interface. The lack of Nd adsorption or solid solution at the calcite-solution interface suggests that the solid solution was orthorhombic and may be modeled as a mixture of orthorhombic NdOHCO 3 (s) and aragonite. Orthorhombic NdOHCO 3 (s) was determined to be the stable Nd-carbonate phase in the Nd-CO 2 -H 2 O system at pCO 2 (g) 0.1 atmospheres at 25 degrees C. The equilibrium constant corrected to zero ionic strength for orthorhombic NdOHCO 3 (s) solubility is 10 10.41(±0.29) for the following: NdOHCO 3 (s) + 3H + = Nd 3+ + CO 2 (g) + H 2 O. Results are discussed in relation to radioactive waste disposal by burial, and specifically in relation to americium chemistry

  7. Preparation and characterization of exfoliated polyaniline/montmorillonite nanocomposites

    International Nuclear Information System (INIS)

    Narayanan, Binitha N.; Koodathil, Ranjana; Gangadharan, Tripti; Yaakob, Zahira; Saidu, Femina K.; Chandralayam, Soumini

    2010-01-01

    Transition metal ions were exchanged with the interlamellar cations of montmorillonite clays and polymerization of aniline was done within the layers. The delaminated clay layers upon ion exchange resulted in exfoliated polyaniline/clay nanocomposite formation which has profound effects on polymer structure, properties and electrical conduction mechanisms. Here we offer polyaniline (PANI)/montmorillonite exfoliated nanocomposite synthesized through a simple, cheap route which need not require complicated and less economical organophilic modification. The prepared composites were characterized using XRD, FTIR, and TG/DTA to prove exfoliation.

  8. Preparation and characterization of exfoliated polyaniline/montmorillonite nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Narayanan, Binitha N., E-mail: binithann@yahoo.co.i [Department of Chemistry, Sree Neelakanta Government Sanskrit College, Pattambi, Palakkad 679306, Kerala (India); Department of Chemical and Process Engineering, Faculty of Engineering, National University of Malaysia, 43600 UKM Bangi, Selangor (Malaysia); Koodathil, Ranjana; Gangadharan, Tripti [Department of Chemistry, Sree Neelakanta Government Sanskrit College, Pattambi, Palakkad 679306, Kerala (India); Yaakob, Zahira [Department of Chemical and Process Engineering, Faculty of Engineering, National University of Malaysia, 43600 UKM Bangi, Selangor (Malaysia); Saidu, Femina K.; Chandralayam, Soumini [Department of Chemistry, Sree Neelakanta Government Sanskrit College, Pattambi, Palakkad 679306, Kerala (India)

    2010-04-15

    Transition metal ions were exchanged with the interlamellar cations of montmorillonite clays and polymerization of aniline was done within the layers. The delaminated clay layers upon ion exchange resulted in exfoliated polyaniline/clay nanocomposite formation which has profound effects on polymer structure, properties and electrical conduction mechanisms. Here we offer polyaniline (PANI)/montmorillonite exfoliated nanocomposite synthesized through a simple, cheap route which need not require complicated and less economical organophilic modification. The prepared composites were characterized using XRD, FTIR, and TG/DTA to prove exfoliation.

  9. Remediation of arsenic-contaminated groundwater using media-injected permeable reactive barriers with a modified montmorillonite: sand tank studies.

    Science.gov (United States)

    Luo, Ximing; Liu, Haifei; Huang, Guoxin; Li, Ye; Zhao, Yan; Li, Xu

    2016-01-01

    A modified montmorillonite (MMT) was prepared using an acid activation-sodium activation-iron oxide coating method to improve the adsorption capacities of natural MMTs. For MMT, its interlamellar distance increased from 12.29 to 13.36 Å, and goethite (α-FeOOH) was intercalated into its clay layers. Two novel media-injected permeable reactive barrier (MI-PRB) configurations were proposed for removing arsenic from groundwater. Sand tank experiments were conducted to investigate the performance of the two MI-PRBs: Tank A was filled with quartz sand. Tank B was packed with quartz sand and zero-valent iron (ZVI) in series, and the MMT slurry was respectively injected into them to form reactive zones. The results showed that for tank A, total arsenic (TA) removal of 98.57% was attained within the first 60 mm and subsequently descended slowly to 88.84% at the outlet. For tank B, a similar spatial variation trend was observed in the quartz sand layer, and subsequently, TA removal increased to ≥99.80% in the ZVI layer. TA removal by MMT mainly depended on both surface adsorption and electrostatic adhesion. TA removal by ZVI mainly relied on coagulation/precipitation and adsorption during the iron corrosion. The two MI-PRBs are feasible alternatives for in situ remediation of groundwater with elevated As levels.

  10. Electrochemical Behaviour of Tinidazole at 1,4-Benzoquinone Modified Carbon Paste Electrode and Its Direct Determination in Pharmaceutical Tablets and Urine by Differential Pulse Voltammetry

    Directory of Open Access Journals (Sweden)

    Yosef Nikodimos

    2017-01-01

    Full Text Available A simple and highly sensitive electrochemical method based on a 1,4-benzoquinone modified carbon paste electrode (1,4-BQMCPE was described for the determination of tinidazole (TDZ. In Britton Robinson buffer solution, TDZ yields well-defined irreversible reduction peak at −0.344 V on a 1,4-BQMCPE. Compared with that on a bare CPE, the reduction peak of TDZ increased significantly on the modified CPE and the effects of different parameters on the voltammetric responses were also investigated. Differential pulse voltammetric method was proposed and optimized for TDZ determination and its reductive peak current response at 1,4-BQMCPE was found to show linear dependence on the concentration of TDZ in the range of 1.0 × 10−6 to 5.0 × 10−4 M with a linear regression equation, correlation coefficient, limit of detection (LOD, and limit of quantification (LOQ of IPC (μA = 0.19958 + 0.02657C (μM, 0.99486, 1.10 × 10−7 M, and 3.77 × 10−7, respectively. Excellent recovery results for spiked TDZ in pharmaceutical tablet samples ranging within 97.44–97.51% and in urine ranging within 95.37–96.91% were observed. The selectivity of the method for TDZ was further studied in the presence of selected potential interferents and confirmed the potential applicability of the developed method for the determination of TDZ.

  11. The electrochemical behavior of Co(TPTZ){sub 2} complex on different carbon based electrodes modified with TiO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ortaboy, Sinem, E-mail: ortaboy@istanbul.edu.tr; Atun, Gülten, E-mail: gatun@istanbul.edu.tr

    2015-04-15

    Electrochemical behavior of cobalt (II) complex with the N-donor ligand 2,2′-bipyridyl-1,3,5-tripyridyl-s-triazine (TPTZ) was investigated to elucidate the electron-proton transfer mechanisms. The electrochemical response of the complex was studied using square-wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) techniques. A conventional three-electrode system, consisting of glassy carbon (GCE), TiO{sub 2} modified glassy carbon (T/GCE), carbon paste (CPE) and TiO{sub 2} modified carbon paste (T/CPE) working electrodes were employed. The ligand/metal ratio and stability constant of the complex as well as the mechanisms of the electrode processes were elucidated by examining the effects of pH, ligand concentration and frequency on the voltammograms. The EIS results indicated that the samples modified with TiO{sub 2} had the higher charge transfer resistance than that of the bare electrodes and also suggested that the electroactivity of the electrode surfaces increased in the following order, T/CPE > CPE > T/GCE > GCE. The surface morphology of the working electrodes was also characterized by atomic force microscopy (AFM). The values of surface roughness parameters were found to be consistent with the results obtained by EIS experiments. - Graphical abstract: Schematic illustration of the experimental process. - Highlights: • Electrochemical behavior of Co(TPTZ){sub 2} complex studied by SWV and EIS techniques. • GCE, CPE T/GCE and T/CPE were used as working electrodes for comparative studies. • The surface morphologies of the electrodes were characterized by AFM. • Mechanisms were proposed from the effects of pH, ligand concentration and frequency. • EIS and morphologic relationships of the surfaces were established successfully.

  12. Characterization of montmorillonite-Ca to use polymer nanocomposites

    International Nuclear Information System (INIS)

    Neto, Joao E.; Neto, Jose C.M.; Campo, Eduardo R.B. del; Nascimento, Nayra R. do; Diaz, Francisco Rolando Valenzuela

    2015-01-01

    Bentonite is an important type of industrial clays due to its rheological properties or accession that are dependent on its high hydrophilicity. This clay has the capability of being modified with organic compounds by treatment with ammonium quaternary salts. After the clay treatment with these salts it presents a high degree of swelling property in organic liquids. Due to this swelling characteristics, the bentonite can be used in dispersions of organic liquids viscous and thixotropic. Another focus of interest this clay is in industry and academia because of its potential use in the adsorption of toxic substances and as fillers in nanocomposites clay / polymer. The objective of this study is to characterize a Cuban calcium bentonite modified with sodium dodecyl sulfate. The clay was characterized by X-ray diffraction, particle size analysis by laser diffraction and scanning electron microscopy. (author)

  13. Reproducing early Martian atmospheric carbon dioxide partial pressure by modeling the formation of Mg-Fe-Ca carbonate identified in the Comanche rock outcrops on Mars

    Science.gov (United States)

    Berk, Wolfgang; Fu, Yunjiao; Ilger, Jan-Michael

    2012-10-01

    The well defined composition of the Comanche rock's carbonate (Magnesite0.62Siderite0.25Calcite0.11Rhodochrosite0.02) and its host rock's composition, dominated by Mg-rich olivine, enable us to reproduce the atmospheric CO2partial pressure that may have triggered the formation of these carbonates. Hydrogeochemical one-dimensional transport modeling reveals that similar aqueous rock alteration conditions (including CO2partial pressure) may have led to the formation of Mg-Fe-Ca carbonate identified in the Comanche rock outcrops (Gusev Crater) and also in the ultramafic rocks exposed in the Nili Fossae region. Hydrogeochemical conditions enabling the formation of Mg-rich solid solution carbonate result from equilibrium species distributions involving (1) ultramafic rocks (ca. 32 wt% olivine; Fo0.72Fa0.28), (2) pure water, and (3) CO2partial pressures of ca. 0.5 to 2.0 bar at water-to-rock ratios of ca. 500 molH2O mol-1rock and ca. 5°C (278 K). Our modeled carbonate composition (Magnesite0.64Siderite0.28Calcite0.08) matches the measured composition of carbonates preserved in the Comanche rocks. Considerably different carbonate compositions are achieved at (1) higher temperature (85°C), (2) water-to-rock ratios considerably higher and lower than 500 mol mol-1 and (3) CO2partial pressures differing from 1.0 bar in the model set up. The Comanche rocks, hosting the carbonate, may have been subjected to long-lasting (>104 to 105 years) aqueous alteration processes triggered by atmospheric CO2partial pressures of ca. 1.0 bar at low temperature. Their outcrop may represent a fragment of the upper layers of an altered olivine-rich rock column, which is characterized by newly formed Mg-Fe-Ca solid solution carbonate, and phyllosilicate-rich alteration assemblages within deeper (unexposed) units.

  14. Electrical and dielectric investigation of intercalated polypyrrole montmorillonite nanocomposite prepared by spontaneous polymerization of pyrrole into Fe(III)-montmorillonite

    Energy Technology Data Exchange (ETDEWEB)

    Zidi, Rabii, E-mail: rabiizidi@gmail.com [Physical Chemistry Laboratory for Mineral Materials and their Applications, National Center for Research in Materials Sciences (CNRSM), B.P.73, 8020 Soliman (Tunisia); Bekri-Abbes, Imene; Sdiri, Nasr [Physical Chemistry Laboratory for Mineral Materials and their Applications, National Center for Research in Materials Sciences (CNRSM), B.P.73, 8020 Soliman (Tunisia); Vimalanandan, Ashokanand; Rohwerder, Michael [Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf (Germany); Srasra, Ezzeddine [Physical Chemistry Laboratory for Mineral Materials and their Applications, National Center for Research in Materials Sciences (CNRSM), B.P.73, 8020 Soliman (Tunisia)

    2016-10-15

    Highlights: • We have prepared and characterized a Fe-MMT/PPy nanocomposites. • Investigate electrical conductivity and dielectric properties of the nanocomposite. • Investigate the temperature and frequency dependencies of alternating current conductivity of nanocomposites. - Abstract: Pyrrole was introduced into Fe(III)-exchanged montmorillonite to spontaneously polymerize within the interlayer resulting in the formation of intercalated polypyrrole-montmorillonite nanocomposite. The molar proportion of pyrrole to interlayer Fe{sup 3+} (R) has been varied from 0.5 to 5. The nanocomposite has been characterized by X-ray diffraction, Scanning Electronic Microscope, FTIR spectroscopy and impedance spectroscopy. It has been shown that intercalated polypyrrole montmorillonite nanocomposite was obtained. The results showed that the dc conductivity and dielectric properties of polypyrrole depend on R. The alternating current (ac) conductivity of the polymer obeys the power law, i.e., σ{sub ac}(ω) = Aω{sup s}. The alternating conductivity of nanocomposite was controlled by the correlated barrier hopping model. The activation energy for alternating current mechanism decreases with increasing frequency which confirms the hopping conduction to the dominant mechanism as compared with the dc activation energy. The dielectric relaxation mechanism was explained on the basis of complex dielectric modulus.

  15. Adsorption of ethyl acetate onto modified clays and its regeneration with supercritical CO2

    Directory of Open Access Journals (Sweden)

    A. M. Cavalcante

    2005-03-01

    Full Text Available Modified clays were used to remove ethyl acetate from aqueous solutions. These clays were regenerated using supercritical CO2. Structural changes in the montmorillonite clay after treatment with quaternary amines were studied. The surface properties of the modified clay changed from highly hydrophilic to highly organophilic. The clay was regenerated by percolation of a stream of CO2 through the porous montmorillonite matrix. Different pressures and temperatures were employed, resulting in different fluid conditions (gas, liquid, and supercritical. The experimental data was fitted with a simplified model. The best desorption result was found under supercritical conditions. A crossover effect was observed. The capacity of the modified clay as a pollutant attenuator remained almost unchanged after a regeneration cycle.

  16. The acid-base titration of montmorillonite

    Science.gov (United States)

    Bourg, I. C.; Sposito, G.; Bourg, A. C.

    2003-12-01

    Proton binding to clay minerals plays an important role in the chemical reactivity of soils (e.g., acidification, retention of nutrients or pollutants). If should also affect the performance of clay barriers for waste disposal. The surface acidity of clay minerals is commonly modelled empirically by assuming generic amphoteric surface sites (>SOH) on a flat surface, with fitted site densities and acidity constant. Current advances in experimental methods (notably spectroscopy) are rapidly improving our understanding of the structure and reactivity of the surface of clay minerals (arrangement of the particles, nature of the reactive surface sites, adsorption mechanisms). These developments are motivated by the difficulty of modelling the surface chemistry of mineral surfaces at the macro-scale (e.g., adsorption or titration) without a detailed (molecular-scale) picture of the mechanisms, and should be progressively incorporated into surface complexation models. In this view, we have combined recent estimates of montmorillonite surface properties (surface site density and structure, edge surface area, surface electrostatic potential) with surface site acidities obtained from the titration of alpha-Al2O3 and SiO2, and a novel method of accounting for the unknown initial net proton surface charge of the solid. The model predictions were compared to experimental titrations of SWy-1 montmorillonite and purified MX-80 bentonite in 0.1-0.5 mol/L NaClO4 and 0.005-0.5 mol/L NaNO3 background electrolytes, respectively. Most of the experimental data were appropriately described by the model after we adjusted a single parameter (silanol sites on the surface of montmorillonite were made to be slightly more acidic than those of silica). At low ionic strength and acidic pH the model underestimated the buffering capacity of the montmorillonite, perhaps due to clay swelling or to the interlayer adsorption of dissolved aluminum. The agreement between our model and the experimental

  17. Determination of Zinc, Cadmium, Lead, Copper and Silver Using a Carbon Paste Electrode and a Screen Printed Electrode Modified with Chromium(III Oxide

    Directory of Open Access Journals (Sweden)

    Zuzana Koudelkova

    2017-08-01

    Full Text Available In this study, the preparation and electrochemical application of a chromium(III oxide modified carbon paste electrode (Cr-CPE and a screen printed electrode (SPE, made from the same material and optimized for the simple, cheap and sensitive simultaneous determination of zinc, cadmium, lead, copper and the detection of silver ions, is described. The limits of detection and quantification were 25 and 80 µg·L−1 for Zn(II, 3 and 10 µg·L−1 for Cd(II, 3 and 10 µg·L−1 for Pb(II, 3 and 10 µg·L−1 for Cu(II, and 3 and 10 µg·L−1 for Ag(I, respectively. Furthermore, this promising modification was transferred to the screen-printed electrode. The limits of detection for the simultaneous determination of zinc, cadmium, copper and lead on the screen printed electrodes were found to be 350 µg·L−1 for Zn(II, 25 µg·L−1 for Cd(II, 3 µg·L−1 for Pb(II and 3 µg·L−1 for Cu(II. Practical usability for the simultaneous detection of these heavy metal ions by the Cr-CPE was also demonstrated in the analyses of wastewaters.

  18. Determination of Zinc, Cadmium, Lead, Copper and Silver Using a Carbon Paste Electrode and a Screen Printed Electrode Modified with Chromium(III) Oxide.

    Science.gov (United States)

    Koudelkova, Zuzana; Syrovy, Tomas; Ambrozova, Pavlina; Moravec, Zdenek; Kubac, Lubomir; Hynek, David; Richtera, Lukas; Adam, Vojtech

    2017-08-09

    In this study, the preparation and electrochemical application of a chromium(III) oxide modified carbon paste electrode (Cr-CPE) and a screen printed electrode (SPE), made from the same material and optimized for the simple, cheap and sensitive simultaneous determination of zinc, cadmium, lead, copper and the detection of silver ions, is described. The limits of detection and quantification were 25 and 80 µg·L -1 for Zn(II), 3 and 10 µg·L -1 for Cd(II), 3 and 10 µg·L -1 for Pb(II), 3 and 10 µg·L -1 for Cu(II), and 3 and 10 µg·L -1 for Ag(I), respectively. Furthermore, this promising modification was transferred to the screen-printed electrode. The limits of detection for the simultaneous determination of zinc, cadmium, copper and lead on the screen printed electrodes were found to be 350 µg·L -1 for Zn(II), 25 µg·L -1 for Cd(II), 3 µg·L -1 for Pb(II) and 3 µg·L -1 for Cu(II). Practical usability for the simultaneous detection of these heavy metal ions by the Cr-CPE was also demonstrated in the analyses of wastewaters.

  19. Using CaO- and MgO-rich industrial waste streams for carbon sequestration

    International Nuclear Information System (INIS)

    Stolaroff, Joshuah K.; Lowry, Gregory V.; Keith, David W.

    2005-01-01

    To prevent rapid climate change, it will be necessary to reduce net anthropogenic CO 2 emissions drastically. This likely will require imposition of a tax or tradable permit scheme that creates a subsidy for negative emissions. Here, we examine possible niche markets in the cement and steel industries where it is possible to generate a limited supply of negative emissions (carbon storage or sequestration) cost-effectively. Ca(OH) 2 and CaO from steel slag or concrete waste can be dissolved in water and reacted with CO 2 in ambient air to capture and store carbon safely and permanently in the form of stable carbonate minerals (CaCO 3 ). The kinetics of Ca dissolution for various particle size fractions of ground steel slag and concrete were measured in batch experiments. The majority of available Ca was found to dissolve on a time scale of hours, which was taken to be sufficiently fast for use in an industrial process. An overview of the management options for steel slag and concrete waste is presented, which indicates how their use for carbon sequestration might be integrated into existing industrial processes. Use of the materials in a carbon sequestration scheme does not preclude subsequent use and is likely to add value by removing the undesirable qualities of water absorption and expansion from the products. Finally, an example scheme is presented which could be built and operated with current technology to sequester CO 2 with steel slag or concrete waste. Numerical models and simple calculations are used to establish the feasibility and estimate the operating parameters of the scheme. The operating cost is estimated to be US$8/t-CO 2 sequestered. The scheme would be important as an early application of technology for capturing CO 2 directly from ambient air

  20. Carbon materials modified by plasma treatment as electrodes for supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Lota, Grzegorz; Frackowiak, Elzbieta [Institute of Chemistry and Technical Electrochemistry, Poznan University of Technology, Piotrowo 3, 60-965 Poznan (Poland); Tyczkowski, Jacek; Kapica, Ryszard [Technical University of Lodz, Faculty of Process and Environmental Engineering, Division of Molecular Engineering, Wolczanska 213, 90-924 Lodz (Poland); Lota, Katarzyna [Institute of Non-Ferrous Metals Branch in Poznan, Central Laboratory of Batteries and Cells, Forteczna 12, 61-362 Poznan (Poland)

    2010-11-15

    The carbon material was modified by RF plasma with various reactive gases: O{sub 2}, Ar and CO{sub 2}. Physicochemical properties of the final carbon products were characterized using different techniques such as gas adsorption method and XPS. Plasma modified materials enriched in oxygen functionalities were investigated as electrodes for supercapacitors in acidic medium. The electrochemical measurements have been carried out using cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy. The electrochemical measurements have confirmed that capacity characteristics are closely connected with a type of plasma exposition. Modification processes have an influence on the kind and amount of surface functional groups in the carbon matrix. The moderate increase of capacity of carbon materials modified by plasma has been observed using symmetric two-electrode systems. Whereas investigations made in three-electrode system proved that the suitable selection of plasma modification parameters allows to obtain promising negative and positive electrode materials for supercapacitor application. (author)

  1. Porphyran-capped gold nanoparticles modified carbon paste electrode: a simple and efficient electrochemical sensor for the sensitive determination of 5-fluorouracil

    Science.gov (United States)

    Lima, Dhésmon; Calaça, Giselle Nathaly; Viana, Adriano Gonçalves; Pessôa, Christiana Andrade

    2018-01-01

    The application of carbon paste electrodes modified with porphyran-capped gold nanoparticles (CPE/AuNps-PFR) to detect an important anticancer drug, 5-fluorouracil (5-FU), is described. Gold nanoparticles (AuNps) were synthesized through a green one-pot route, by using porphyran (PFR) (a sulfated polysaccharide extracted from red seaweed) as reducing and stabilizing agent. The reaction temperature and the concentrations of AuCl4- and PFR for AuNps-PFR synthesis were optimized by using a 23 full factorial design with central point assayed in triplicate. The smallest particle size (128.7 nm, obtained by DLS) was achieved by employing a temperature of 70 °C and AuCl4- and PFR concentrations equal to 2.5 mmol L-1 and 0.25 mg mL-1, respectively. The AuNps-PFR nanocomposite was characterized by UV-vis spectroscopy, FTIR, DLS, TEM, XRD and zeta potential, which proved that PFR was effective at reducing and capping the AuNps. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) experiments showed that the nanocomposite could enhance the electrochemical performance of the electrodes, as a consequence of the high conductivity and large surface area presented by the AuNps. The CPE/AuNps-PFR was able to electrocatalyze the oxidation of 5-FU by CV and differential pulse voltammetry (DPV). A linear relationship between the DPV peak currents and 5-FU concentration was verified in the range from 29.9 to 234 μmol L-1 in 0.04 mol L-1 BR buffer solution pH 8.0. Detection and quantification limits were found to be 0.66 and 2.22 μmol L-1, respectively. Besides the good sensitivity, CPE/AuNps-PFR showed reproducibility and did not suffer significant interference from potentially electroative biological compounds. The good analytical performance of the modified electrode was confirmed for determining 5-FU in pharmaceutical formulations, with good percent recoveries (ranging from 96.6 to 101.4%) and an acceptable relative standard deviation (RSD = 2.80%).

  2. Combining charcoal and elemental black carbon analysis in sedimentary archives: Implications for past fire regimes, the pyrogenic carbon cycle, and the human-climate interactions

    Science.gov (United States)

    Thevenon, Florian; Williamson, David; Bard, Edouard; Anselmetti, Flavio S.; Beaufort, Luc; Cachier, Hélène

    2010-07-01

    This paper addresses the quantification of combustion-derived products in oceanic and continental sediments by optical and chemical approaches, and the interest of combining such methods for reconstructing past biomass burning activity and the pyrogenic carbon cycle. In such context, the dark particles > 0.2 µm 2 remaining after the partial digestion of organic matter are optically counted by automated image analysis and defined as charcoal, while the elemental carbon remaining after thermal and chemical oxidative treatments is quantified as black carbon (BC). The obtained pyrogenic carbon records from three sediment core-based case studies, (i) the Late Pleistocene equatorial Pacific Ocean, (ii) the mid-Holocene European Lake Lucerne, and (iii) the Late Holocene African Lake Masoko, are interpreted as proxy records of regional transportation mechanisms and biomass burning activities. The results show that the burial of dark carbon-rich particles in the 360 kyr-long record from the west equatorial Pacific is controlled by the combination of sea-level changes and low-latitude atmospheric circulation patterns (summer monsoon dynamics). However, the three fold increases in charcoal and BC sediment influxes between 53-43 and 12-10 kyr BP suggest that major shifts in fire activity occur synchronously with human colonization in the Indo/Pacific region. The coarse charcoal distribution from a 7.2 kyr record from Lake Lucerne in Switzerland closely matches the regional timing of major technical, land-use, and socio-economic changes during the Neolithic (between ca. 5.7 and 5.2 kyr BP and 4.9-4.5 kyr BP), the Bronze and Iron Ages (at ca. 3.3 and 2.4 kyr BP, respectively), and the industrialization (after AD 1838), pointing to the key impact of human activities on the sources, transportation processes and reservoirs of refractory carbon during the Holocene. In the tropical Masoko maar lake in Tanzania, where charcoal and BC records are highly sensitive to the local climate

  3. Effect of humidity and interlayer cation on frictional strength of montmorillonite

    Science.gov (United States)

    Tetsuka, H.; Katayama, I.; Sakuma, H.; Tamura, K.

    2016-12-01

    Smectite has been ubiquitously seen in fault gouge (Schleicher et al., 2006; Kuo et al., 2009; Si et al., 2014; Kameda, 2015) and is characteristic by low frictional coefficient (Saffer et al., 2001; Ikari et al., 2007); consequently, it has a key role in fault dynamics. The frictional strength of montmorillonite (a typical type of smectite) is affected by mainly two factors, 1) hydration state and 2) interlayer cation. Previous laboratory experiments have shown that the frictional strength of montmorillonite changes with hydration state (Ikari et al., 2007) and with interlayer cation (Behnsen and Faulkner, 2013). However, experimental study for frictional strengths of interlayer cation-exchanged montmorillonite under controlled hydration state has not been reported. We are developing humidity control system in biaxial friction testing machine and try to investigate the effect of relative humidity and interlayer cation on frictional strength of montmorillonite. The humidity control system consists of two units, 1) the pressure vessel (core holder) unit controlled by a constant temperature and 2) the vapor generating unit controlled by variable temperature. We control relative humidity around sample, which is calculated from the temperature around sample and the vapor pressure at vapor generating unit. Preliminary experiments under controlled humidity show frictional coefficient of montmorillonite decrease with increasing relative humidity. In the meeting, we will report the systematic study of frictional coefficient as function of relative humidity and interlayer cation species.

  4. Simultaneous voltammetric determination of dopamine and ascorbic acid using multivariate calibration methodology performed on a carbon paste electrode modified by a mer-[RuCl{sub 3}(dppb)(4-pic)] complex

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Poliana M.; Sandrino, Bianca; Moreira, Tiago F.; Wohnrath, Karen; Nagata, Noemi; Pessoa, Christiana A. [Universidade Estadual de Ponta Grossa, PR (Brazil). Dept. de Quimica]. E-mail: capessoa@uepg.br

    2007-07-01

    The preparation and electrochemical characterization of a carbon paste electrode (CPE) modified with mer-[Ru0Cl{sub 3}(dppb)(4-pic)] (dppb=Ph{sub 2}P(CH{sub 2}){sub 4}PPh{sub 2}, 4-pic=CH{sub 3}C{sub 5}H{sub 4}N), referred to as Rupic, were investigated. The CPE/Rupic system displayed only one pair of redox peaks, with a midpoint potential at 0.28 V vs. Ag/AgCl, which were ascribed to Ru{sup III}/Ru{sup II} charge transfer. This modified electrode presented the property of electrocatalysing the oxidation of dopamine (DA) and ascorbic acid (AA) at 0.35 V and 0.30 V vs. Ag/AgCl, respectively. Because the oxidation for both AA and DA practically occurred at the same potential, distinguishing between them was difficult with cyclic voltammetry. This limitation was overcome using Partial Least Square Regression (PLSR), which allowed us, with the optimised models, to determine four synthetic samples with prediction errors (RMSEP) of 5.55 X 10{sup -5} mol L{sup -1} and 7.48 X 10{sup -6} mol L{sup -1} for DA and AA, respectively. (author)

  5. IUPAC-NIST Solubility Data Series. 95. Alkaline Earth Carbonates in Aqueous Systems. Part 2. Ca

    Science.gov (United States)

    Vanderdeelen, Jan

    2012-06-01

    The alkaline earth carbonates are an important class of minerals. This article is part of a volume in the IUPAC-NIST Solubility Data Series that compiles and critically evaluates solubility data of the alkaline earth carbonates in water and in simple aqueous electrolyte solutions. Part 1 outlined the procedure adopted in this volume, and presented the beryllium and magnesium carbonates. Part 2, the current paper, compiles and critically evaluates the solubility data of calcium carbonate. The chemical forms included are the anhydrous CaCO3 types calcite, aragonite, and vaterite, the monohydrate monohydrocalcite (CaCO3. H2O), the hexahydrate ikaite (CaCO3.6H2O), and an amorphous form. The data were analyzed with two model variants, and thermodynamic data of each form consistent with each of the models and with the CODATA key values for thermodynamics are presented.

  6. The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate

    Science.gov (United States)

    Pilo, Raphael; Harel, Noga; Nissan, Joseph; Levartovsky, Shifra

    2016-01-01

    The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP) crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM) technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC) or Self Adhesive Resin Cement (SARC)). Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa) were significantly higher than those for SARC (2.28 ± 0.58 MPa). The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns. PMID:27023532

  7. The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate

    Directory of Open Access Journals (Sweden)

    Raphael Pilo

    2016-03-01

    Full Text Available The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC or Self Adhesive Resin Cement (SARC. Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa were significantly higher than those for SARC (2.28 ± 0.58 MPa. The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns.

  8. Fixation of enzyme protein in soil by the clay mineral montmorillonite

    DEFF Research Database (Denmark)

    Sørensen, L.H.

    1969-01-01

    Aminosäureverbindungen, die im Boden während des biologischen Abbaus von Kohlehydraten gebildet und vom Tonmineral Montmorillonit stabilisiert werden, haben Enzymcharakter und sind folglich Proteine.......Aminosäureverbindungen, die im Boden während des biologischen Abbaus von Kohlehydraten gebildet und vom Tonmineral Montmorillonit stabilisiert werden, haben Enzymcharakter und sind folglich Proteine....

  9. A hydrous Ca-bearing magnesium carbonate from playa lake sediments, Salines Lake, Spain

    Science.gov (United States)

    Queralt, I.; Julia, R.; Plana, F.; Bischoff, J.L.

    1997-01-01

    Sediments of playa Lake Salines, SE, Spain, contain a carbonate mineral characterized by X-ray diffraction peaks very similar to, but systematically shifted from those of pure magnesite. Analyses (SEM, IR and Raman spectroscopy, DTA, TGA, and ICP) indicate the mineral is a hydrous Ca-bearing magnesium carbonate with the chemical formula (Mg0.92,Ca0.08)CO3??3H2O. Thermal characteristics of the mineral are similar to those of other known hydrated magnesium carbonates. X-ray and electron diffraction data suggests a monoclinic system (P21/n space group) with unit-cell parameters of a = 6.063(6), b = 10.668(5), and c = 6.014(4) A?? and ?? = 107.28??.

  10. Characterisation, in vitro release study, and antibacterial activity of montmorillonite-gentamicin complex material

    International Nuclear Information System (INIS)

    Rapacz-Kmita, A.; Bućko, M.M.; Stodolak-Zych, E.; Mikołajczyk, M.; Dudek, P.; nd Department of Surgery, Kopernika 21, 31-501 Krakow (Poland))" data-affiliation=" (Jagiellonian University, Medical College, 2nd Department of Surgery, Kopernika 21, 31-501 Krakow (Poland))" >Trybus, M.

    2017-01-01

    The present paper concerns the potential use of montmorillonite as a drug carrier and focusses on the intercalation of the studied clay with gentamicin (an aminoglycoside antibiotic) at various temperatures (20, 50 and 80 °C). The experiments were performed to identify the temperature required for the optimum intercalation of gentamicin into the interlayer of montmorillonite. The structural and microstructural properties of gentamicin and the potential for introducing it between smectite clay layers were investigated by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopic techniques, and SEM with EDS analysis. Additionally, the in vitro drug release behaviour of the montmorillonite-gentamicin complex and its antibacterial activity against Escherichia coli (E. coli) bacteria was investigated. Based on these studies, the impact of temperature on the intercalation of the drug between layers of smectite was evaluated. It was found that an intercalation temperature of 50 °C resulted in the highest shift in the position of principle peak d (001) as measured by XRD, suggesting, that the greatest amount of gentamicin had been introduced into the interlayer space of montmorillonite at this temperature. Subsequently, the montmorillonite-gentamicin complex material obtained at 50 °C revealed the greatest capacity for killing E. coli bacteria during an in vitro test. - Highlights: • A novel montmorillonite-gentamicin hybrid materials was prepared as potential drug carrier. • Optimal conditions for the intercalation of gentamicin into the interlayer space of montmorillonite were tested. • The MMT-G complex material obtained at 50 °C revealed the greatest capacity for killing E. coli during the inhibitory zone test. • Modulating drug delivery was monitored and confirmed in in vitro drug release study.

  11. Characterisation, in vitro release study, and antibacterial activity of montmorillonite-gentamicin complex material

    Energy Technology Data Exchange (ETDEWEB)

    Rapacz-Kmita, A., E-mail: kmita@agh.edu.pl [AGH University of Science and Technology, Faculty of Materials Science and Ceramics, Mickiewicza 30, 30-059 Krakow (Poland); Bućko, M.M.; Stodolak-Zych, E. [AGH University of Science and Technology, Faculty of Materials Science and Ceramics, Mickiewicza 30, 30-059 Krakow (Poland); Mikołajczyk, M. [The University Hospital in Krakow, Division of Microbiology, Kopernika 19, 31-501 Krakow (Poland); Dudek, P. [AGH University of Science and Technology, Faculty of Mechanical Engineering and Robotics, Mickiewicza 30, 30-059 Krakow (Poland); Trybus, M. [Jagiellonian University, Medical College, 2" n" d Department of Surgery, Kopernika 21, 31-501 Krakow (Poland)

    2017-01-01

    The present paper concerns the potential use of montmorillonite as a drug carrier and focusses on the intercalation of the studied clay with gentamicin (an aminoglycoside antibiotic) at various temperatures (20, 50 and 80 °C). The experiments were performed to identify the temperature required for the optimum intercalation of gentamicin into the interlayer of montmorillonite. The structural and microstructural properties of gentamicin and the potential for introducing it between smectite clay layers were investigated by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopic techniques, and SEM with EDS analysis. Additionally, the in vitro drug release behaviour of the montmorillonite-gentamicin complex and its antibacterial activity against Escherichia coli (E. coli) bacteria was investigated. Based on these studies, the impact of temperature on the intercalation of the drug between layers of smectite was evaluated. It was found that an intercalation temperature of 50 °C resulted in the highest shift in the position of principle peak d{sub (001)} as measured by XRD, suggesting, that the greatest amount of gentamicin had been introduced into the interlayer space of montmorillonite at this temperature. Subsequently, the montmorillonite-gentamicin complex material obtained at 50 °C revealed the greatest capacity for killing E. coli bacteria during an in vitro test. - Highlights: • A novel montmorillonite-gentamicin hybrid materials was prepared as potential drug carrier. • Optimal conditions for the intercalation of gentamicin into the interlayer space of montmorillonite were tested. • The MMT-G complex material obtained at 50 °C revealed the greatest capacity for killing E. coli during the inhibitory zone test. • Modulating drug delivery was monitored and confirmed in in vitro drug release study.

  12. Characterization of poly pyrrole/montmorillonite electro polymerised onto Pt

    International Nuclear Information System (INIS)

    Castagno, K.R.L.; Azambuja, D.S.; Dalmoro, V.; Mauller, R.S.

    2010-01-01

    In this study films of polypyrrole/montmorillonite (PPy/MT) were electropolymerized on platinum in order to evaluate the performance of this technique in the preparation of nanocomposite materials and to determine the thermal properties and conductivity of the composites. The films were synthesized from a solution containing pyrrole, dodecylbenzene sulfonate, acid and two types of clays: montmorillonite-Na + (MT-Na) and montmorillonite-30B (MT-M). The characterization of the films we have used FT-IR, TEM, XRD, TGA, DSC and resistivity measurement by the four-point van der Pauw method. The study showed that the adopted method of exfoliation and the electropolymerization method used, allows obtaining nanocomposite materials. Analyses of FT-IR, TEM and XRD show that the clays are exfoliated in the polymer matrix. Thermal analysis of the films indicates that the addition of clay reflects an enhancement in the thermal properties of the matrix of PPy, but decreases the conductivity of the same. (author)

  13. Electrochemical parameters of ethamsylate at multi-walled carbon nanotube modified glassy carbon electrodes.

    Science.gov (United States)

    Wang, Sheng-Fu; Xu, Qiao

    2007-05-01

    In this paper, some electrochemical parameters of ethamsylate at a multi-walled carbon nanotube modified glassy carbon electrode, such as the charge number, exchange current density, standard heterogeneous rate constant and diffusion coefficient, were measured by cyclic voltammetry, chronoamperometry and chronocoulometry. The modified electrode exhibits good promotion of the electrochemical reaction of ethamsylate and increases the standard heterogeneous rate constant of ethamsylate greatly. The differential pulse voltammetry responses of ethamsylate were linearly dependent on its concentrations in a range from 2.0 x 10(-6) to 6.0 x 10(-5) mol L(-1), with a detection limit of 4.0 x 10(-7) mol L(-1).

  14. Gas barrier properties of nanocomposites based on in situ polymerized poly(n-butyl methacrylate) in the presence of surface modified montmorillonite

    Czech Academy of Sciences Publication Activity Database

    Herrera-Alonso, J. M.; Sedláková, Zdeňka; Marand, E.

    2010-01-01

    Roč. 349, 1-2 (2010), s. 251-257 ISSN 0376-7388 R&D Projects: GA AV ČR KAN100500651; GA MŠk ME09058 Institutional research plan: CEZ:AV0Z40500505 Keywords : barrier membranes * nanocomposites * montmorillonite Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.673, year: 2010

  15. IUPAC-NIST Solubility Data Series. 95. Alkaline Earth Carbonates in Aqueous Systems. Part 2. Ca

    International Nuclear Information System (INIS)

    De Visscher, Alex; Vanderdeelen, Jan

    2012-01-01

    The alkaline earth carbonates are an important class of minerals. This article is part of a volume in the IUPAC-NIST Solubility Data Series that compiles and critically evaluates solubility data of the alkaline earth carbonates in water and in simple aqueous electrolyte solutions. Part 1 outlined the procedure adopted in this volume, and presented the beryllium and magnesium carbonates. Part 2, the current paper, compiles and critically evaluates the solubility data of calcium carbonate. The chemical forms included are the anhydrous CaCO 3 types calcite, aragonite, and vaterite, the monohydrate monohydrocalcite (CaCO 3 · H 2 O), the hexahydrate ikaite (CaCO 3 ·6H 2 O), and an amorphous form. The data were analyzed with two model variants, and thermodynamic data of each form consistent with each of the models and with the CODATA key values for thermodynamics are presented.

  16. Effect of carbonation temperature on CO{sub 2} adsorption capacity of CaO derived from micro/nanostructured aragonite CaCO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Hlaing, Nwe Ni, E-mail: nwenihlaing76@gmail.com [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Department of International Development Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo (Japan); Department of Physics, University of Yangon, 11041 Kamayut, Yangon (Myanmar); Sreekantan, Srimala, E-mail: srimala@usm.my [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Hinode, Hirofumi, E-mail: hinode@ide.titech.ac.jp; Kurniawan, Winarto, E-mail: Kurniawan.w.ab@m.titech.ac.jp [Department of International Development Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo (Japan); Thant, Aye Aye, E-mail: a2thant@gmail.com [Department of Physics, University of Yangon, 11041 Kamayut, Yangon (Myanmar); Othman, Radzali, E-mail: radzali@utem.edu.my [Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Malacca (Malaysia); Mohamed, Abdul Rahman, E-mail: chrahman@eng.usm.my [Low Carbon Economy (LCE) Research Group, School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang (Malaysia); Salime, Chris, E-mail: chris.salim@surya.ac.id [Environmental Engineering, Surya University, Tangerang, 15810 Banten (Indonesia)

    2016-07-06

    Recent years, CaO-based synthetic materials have been attracted attention as potential adsorbents for CO{sub 2} capture mainly due to their high CO{sub 2} adsorption capacity. In this study, micro/nanostructured aragonite CaCO{sub 3} was synthesized by a simple hydrothermal method with using polyacrylamide (PAM). The structural, morphological and thermal properties of the synthesized sample were investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and thermogravimetry analysis (TG-DTA). The XRD and FESEM results showed that the obtained sample was aragonite CaCO{sub 3} with aggregated nanorods and microspheres composed of nanorods. A TG-DTA apparatus with Thermoplus 2 software was used to investigate the effect of carbonation temperature on the CO{sub 2} adsorption capacity of CaO derived from aragonite CaCO{sub 3} sample. At 300 °C, the sample reached the CO{sub 2} adsorption capacity of 0.098 g-CO{sub 2}/g-adsorbent, whereas the sample achieved the highest capacity of 0.682 g-CO{sub 2}/g-adsorbent at 700 °C. The results showed that the carbonation temperature significantly influenced on the CO{sub 2} adsorption capacity of the CaO derived from aragonite CaCO{sub 3}.

  17. Functional properties of extruded nano composites based on cassava starch, polyvinyl alcohol and montmorillonite

    International Nuclear Information System (INIS)

    Debiagi, Flavia; Matsuda, Daniel K.M.; Marengo, Vitor A.; Vercelheze, Ana Elisa S.; Mali, Suzana

    2011-01-01

    The objectives of this work were to produce biodegradable trays based on cassava starch (native or modified by acid), sugarcane fibers and nano clay (sodium montmorillonite) and also to characterize the produced trays according to their density, tensile strength, X-ray diffraction and biodegradability. The trays were obtained by thermoforming into a hydraulic press coupled to a Teflon mold (18 x 23 cm) at 130 degree C/ 20 min and 100 bars of pressure. The peak related to the nano clay (2 = 7.1 o ) were not observed in XRD patterns of the trays, suggesting the formation of an exfoliated structure in the nano composite. The addition of modified starch increased tensile strength and density of the samples, and the addition of fibers and nano clays decreased the tensile strength of native and modified starch trays. The weight loss of trays was not affected by the starch type, however the addition of fibers increased the biodegradation and the addition of nano clays decreased. (author)

  18. Chemical synthesis, characterization and electro-oxidation of hydrazine via a carbon paste electrode modified with poly (P-phenylendiamine/Al2O3) nanocomposite

    International Nuclear Information System (INIS)

    Emamgholizadeh, Abbas; Omrani, Abdollah; Rostami, Abbas Ali

    2012-01-01

    Highlights: ► A novel nanocomposite based on poly (P-phenylendiamine)/alumina was synthesized. ► It was observed that the nanocomposite increased the surface catalytic activity of CPE toward oxidation of hydrazine. ► The EIS measurements showed that the values of R ct decreases by the nanoalumina presence. - Abstract: In this article, the chemical synthesis and characterization of Al 2 O 3 nanoparticles dispersed into poly (P-phenylendiamine) (PpDP) was reported. The morphology, conductivity and structure of the nanocomposite was characterized by scanning electron microscopy (SEM), four probe testing and XRD experiment, respectively. Catalytic activity and stability for the oxidation of hydrazine were studied by using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The results show that the nanocomposite significantly enhances the effective surface area and the catalytic activity of the CPE (carbon paste electrode) for oxidation of hydrazine. The results obtained confirmed that the dispersion of the Al 2 O 3 particles is connected with catalytic response to a higher activity. The nanotubular morphology of poly (P-phenylendiamine) helps in the effective dispersion of Al 2 O 3 particles facilitating the easier access of hydrazine to the catalytic sites. The poly (P-phenylendiamine) nanotubes modified with Al 2 O 3 nanoparticles cause a great increase in electroactivity and the electro-catalytic properties of CPE for hydrazine oxidation.

  19. IUPAC-NIST Solubility Data Series. 95. Alkaline Earth Carbonates in Aqueous Systems. Part 2. Ca

    Energy Technology Data Exchange (ETDEWEB)

    De Visscher, Alex; Vanderdeelen, Jan [Department of Chemical and Petroleum Engineering, and Centre for Environmental Engineering Research and Education (CEERE), Schulich School of Engineering, University of Calgary, Calgary, Alberta, T2N 1N4 (Canada); Department of Applied Analytical and Physical Chemistry, Faculty of Bioscience Engineering, Ghent University, B-9000 Ghent (Belgium)

    2012-06-15

    The alkaline earth carbonates are an important class of minerals. This article is part of a volume in the IUPAC-NIST Solubility Data Series that compiles and critically evaluates solubility data of the alkaline earth carbonates in water and in simple aqueous electrolyte solutions. Part 1 outlined the procedure adopted in this volume, and presented the beryllium and magnesium carbonates. Part 2, the current paper, compiles and critically evaluates the solubility data of calcium carbonate. The chemical forms included are the anhydrous CaCO{sub 3} types calcite, aragonite, and vaterite, the monohydrate monohydrocalcite (CaCO{sub 3}{center_dot} H{sub 2}O), the hexahydrate ikaite (CaCO{sub 3}{center_dot}6H{sub 2}O), and an amorphous form. The data were analyzed with two model variants, and thermodynamic data of each form consistent with each of the models and with the CODATA key values for thermodynamics are presented.

  20. Validating carbonation parameters of alkaline solid wastes via integrated thermal analyses: Principles and applications

    International Nuclear Information System (INIS)

    Pan, Shu-Yuan; Chang, E.-E.; Kim, Hyunook; Chen, Yi-Hung; Chiang, Pen-Chi

    2016-01-01

    Highlights: • Key carbonation parameters of wastes are determined by integrated thermal analyses. • A modified TG-DTG interpretation is proposed, and validated by the DSC technique. • The modified TG-DTG interpretation is further verified by DTA, TG-MS and TG-FTIR. • Kinetics and thermodynamics of CaCO 3 decomposition in solid wastes are determined. • Implication to maximum carbonation conversion of various solid wastes is described. - Abstract: Accelerated carbonation of alkaline solid wastes is an attractive method for CO 2 capture and utilization. However, the evaluation criteria of CaCO 3 content in solid wastes and the way to interpret thermal analysis profiles were found to be quite different among the literature. In this investigation, an integrated thermal analyses for determining carbonation parameters in basic oxygen furnace slag (BOFS) were proposed based on thermogravimetric (TG), derivative thermogravimetric (DTG), and differential scanning calorimetry (DSC) analyses. A modified method of TG-DTG interpretation was proposed by considering the consecutive weight loss of sample with 200–900 °C because the decomposition of various hydrated compounds caused variances in estimates by using conventional methods of TG interpretation. Different quantities of reference CaCO 3 standards, carbonated BOFS samples and synthetic CaCO 3 /BOFS mixtures were prepared for evaluating the data quality of the modified TG-DTG interpretation, in terms of precision and accuracy. The quantitative results of the modified TG-DTG method were also validated by DSC analysis. In addition, to confirm the TG-DTG results, the evolved gas analysis was performed by mass spectrometer and Fourier transform infrared spectroscopy for detection of the gaseous compounds released during heating. Furthermore, the decomposition kinetics and thermodynamics of CaCO 3 in BOFS was evaluated using Arrhenius equation and Kissinger equation. The proposed integrated thermal analyses for

  1. Validating carbonation parameters of alkaline solid wastes via integrated thermal analyses: Principles and applications

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Shu-Yuan [Graduate Institute of Environmental Engineering, National Taiwan University, Taipei 10673, Taiwan (China); Chang, E.-E. [Department of Biochemistry, Taipei Medical University, Taipei 110, Taiwan (China); Kim, Hyunook [Department of Environmental Engineering, University of Seoul, Seoul 130-743 (Korea, Republic of); Chen, Yi-Hung [Department of Chemical Engineering and Biotechnology, National Taipei University of Technology, Taipei 10608, Taiwan (China); Chiang, Pen-Chi, E-mail: pcchiang@ntu.edu.tw [Graduate Institute of Environmental Engineering, National Taiwan University, Taipei 10673, Taiwan (China)

    2016-04-15

    Highlights: • Key carbonation parameters of wastes are determined by integrated thermal analyses. • A modified TG-DTG interpretation is proposed, and validated by the DSC technique. • The modified TG-DTG interpretation is further verified by DTA, TG-MS and TG-FTIR. • Kinetics and thermodynamics of CaCO{sub 3} decomposition in solid wastes are determined. • Implication to maximum carbonation conversion of various solid wastes is described. - Abstract: Accelerated carbonation of alkaline solid wastes is an attractive method for CO{sub 2} capture and utilization. However, the evaluation criteria of CaCO{sub 3} content in solid wastes and the way to interpret thermal analysis profiles were found to be quite different among the literature. In this investigation, an integrated thermal analyses for determining carbonation parameters in basic oxygen furnace slag (BOFS) were proposed based on thermogravimetric (TG), derivative thermogravimetric (DTG), and differential scanning calorimetry (DSC) analyses. A modified method of TG-DTG interpretation was proposed by considering the consecutive weight loss of sample with 200–900 °C because the decomposition of various hydrated compounds caused variances in estimates by using conventional methods of TG interpretation. Different quantities of reference CaCO{sub 3} standards, carbonated BOFS samples and synthetic CaCO{sub 3}/BOFS mixtures were prepared for evaluating the data quality of the modified TG-DTG interpretation, in terms of precision and accuracy. The quantitative results of the modified TG-DTG method were also validated by DSC analysis. In addition, to confirm the TG-DTG results, the evolved gas analysis was performed by mass spectrometer and Fourier transform infrared spectroscopy for detection of the gaseous compounds released during heating. Furthermore, the decomposition kinetics and thermodynamics of CaCO{sub 3} in BOFS was evaluated using Arrhenius equation and Kissinger equation. The proposed

  2. Molecular Level Investigation of CH 4 and CO 2 Adsorption in Hydrated Calcium–Montmorillonite

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Mal-Soon [Physical; McGrail, B. Peter [Physical; Rousseau, Roger [Physical; Glezakou, Vassiliki-Alexandra [Physical

    2017-11-17

    We have studied the mechanism of intercalation and methane adsorption from a H2O/CH4/CO2 mixture on a prototypical shale component, Ca-montmorillonite. We employed ab initio molecular dynamics simulations at 323 K and 90 bar to obtain molecular level information of adsorption energetics, speciation, and structural and thermodynamic properties. Interaction of CH4 with surface Lewis acidic sites (Ca2+, surface OH) results in large induced dipoles (~1 D) that lead to relatively strong adsorption energies that level off once a full CH4 layer is formed. Intercalated CH4, also exhibits induced dipoles at low hydration levels, when the interaction with Ca2+ cations are less hindered. CO2 displaces CH4 in the coordination sphere of the cations (in the interlayer) or in the surface, thereby driving CH4 extraction. Our simulations indicate that there is a Goldilocks pressure range (~60-100 bar) where scCO2 –facilitated CH4 extraction will be maximized.

  3. Effects of mineral additives on biochar formation: carbon retention, stability, and properties.

    Science.gov (United States)

    Li, Feiyue; Cao, Xinde; Zhao, Ling; Wang, Jianfei; Ding, Zhenliang

    2014-10-07

    Biochar is being recognized as a promising tool for long-term carbon sequestration, and biochar with high carbon retention and strong stability is supposed to be explored for that purpose. In this study, three minerals, including kaolin, calcite (CaCO3), and calcium dihydrogen phosphate [Ca(H2PO4)2], were added to rice straw feedstock at the ratio of 20% (w/w) for biochar formation through pyrolysis treatment, aiming to improve carbon retention and stabilization in biochar. Kaolin and CaCO3 had little effect on the carbon retention, whereas Ca(H2PO4)2 increased the carbon retention by up to 29% compared to untreated biochar. Although the carbon loss from the kaolin-modified biochar with hydrogen peroxide oxidation was enhanced, CaCO3 and Ca(H2PO4)2 modification reduced the carbon loss by 18.6 and 58.5%, respectively. Moreover, all three minerals reduced carbon loss of biochar with potassium dichromate oxidation from 0.3 to 38.8%. The microbial mineralization as CO2 emission in all three modified biochars was reduced by 22.2-88.7% under aerobic incubation and 5-61% under anaerobic incubation. Enhanced carbon retention and stability of biochar with mineral treatment might be caused by the enhanced formation of aromatic C, which was evidenced by cross-polarization magic angle spinning (13)C nuclear magnetic resonance spectra and Fourier transform infrared spectroscopy analysis. Our results indicated that the three minerals, especially Ca(H2PO4)2, were effective in increasing carbon retention and strengthening biochar stabilization, which provided a novel idea that people could explore and produce the designated biochar with high carbon sequestration capacity and stability.

  4. Nano-rod Ca-decorated sludge derived carbon for removal of phosphorus.

    Science.gov (United States)

    Kong, Lingjun; Han, Meina; Shih, Kaimin; Su, Minhua; Diao, Zenghui; Long, Jianyou; Chen, Diyun; Hou, Li'an; Peng, Yan

    2018-02-01

    Recovering phosphorus (P) from waste streams takes the unique advantage in simultaneously addressing the crisis of eutrophication and the shortage of P resource. A novel calcium decorated sludge carbon (Ca-SC) was developed from dyeing industry wastewater treatment sludge by decorating calcium (Ca) to effectively adsorb phosphorus from solution. The X-ray diffraction (XRD) and Fourier transform infrared (FTIR) techniques were used to characterize the Ca-SCs, followed by isotherm and kinetic sorption experiments. A preferred design with CaCO 3 to sludge mass ratio of 1:2 was found to have a sorption capacity of 116.82 mg/g for phosphorus. This work reveals the crucial role of well-dispersed nano-rod calcium on the Ca-SC surface for the sorption of phosphorus. Moreover, the decoration of nano-rod calcium was found to further promote the uptake of phosphorus through the formation of hydroxylapatite (Ca 5 (PO 4 ) 3 (OH)). Thus, the development of decorated Ca-SC for sorption of phosphorus is very important in solving the P pollution and resource loss. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Solvent Free Preparation of p-Cymene from Limonene Using Vietnamese Montmorillonite

    DEFF Research Database (Denmark)

    Nguyen, Thao-Tran Thi; Duus, Fritz; Le, Thach Ngoc

    2013-01-01

    p-Cymene, an important intermediate in industrial chemistry, has been prepared in good yields by thermally induced dehydrogenation of limonene under solvent-free reaction conditions using Vietnamese montmorillonite as an efficient green catalyst.......p-Cymene, an important intermediate in industrial chemistry, has been prepared in good yields by thermally induced dehydrogenation of limonene under solvent-free reaction conditions using Vietnamese montmorillonite as an efficient green catalyst....

  6. Molecular dynamics as a method to gain understanding in questions concerning montmorillonite

    International Nuclear Information System (INIS)

    Seppaelae, A.; Vaari, J.; Puhakka, E.; Tanhua-Tyrkkoe, M.; Olin, M.; Kasa, S.

    2012-01-01

    Document available in extended abstract form only. Bentonite is one of the main material components to be used in the KBS-3 concept for safe disposal of spent nuclear fuel. The functional material in bentonite giving its beneficial properties is montmorillonite mineral. Montmorillonite consists of two completely different components: one nano-metre thick and approximately 200-400 nano-metres wide mineral layers carrying constant charge and charge compensating cations very near the mineral surfaces. The first component is more of a passive component while the second can absorb water molecules and change the cationic composition. In addition to montmorillonite bentonite usually contains some salts dissolved into water and accessory minerals. Any bulk bentonite is formed from these components via many scales of which structure is not yet fully known to science. Therefore the beneficial macroscopic properties of bentonite are assumed to follow from the nano-level structure and reactions. In safety studies of spent fuel disposal the time span to be considered extends beyond a hundred thousand years making any straightforward experimenting impossible. However, by modelling it is possible to study even very long periods of time. Unfortunately the model data and reactions are at least implicitly based on our short term experiments and may therefore be biased in some way. One possible solution to this may be the application of molecular chemistry or dynamics to construct the basis for our modelling studies. We have applied molecular chemistry on surface properties of kaolinite clay and biotite mineral but molecular dynamics is a new type of modelling for us. We believe that (during the coming ten years) molecular dynamics could make it easier to understand for example the following topics: How do charge compensating (exchanged) and aqueous cations interact? Why does water expand montmorillonite during wetting? Exact mechanism? How does water leave montmorillonite during

  7. A novel sensor based on electropolymerization of β-cyclodextrin and L-arginine on carbon paste electrode for determination of fluoroquinolones

    International Nuclear Information System (INIS)

    Zhang, Fenfen; Gu, Shuqing; Ding, Yaping; Zhang, Zhen; Li, Li

    2013-01-01

    Graphical abstract: The inner cavities of β-CD could restrain fluoroquinolones to form stable host–guest inclusion complexes, and the guanidyl group of L-arg could enable L-arg to form electrostatic interactions with negatively charged groups -COO − of fluoroquinolones. Highlights: ► Electropolymerization of β-cyclodextrin and L-arginine on carbon paste electrode. ► The electrooxidation and reaction of FQs on the modified CPE were surmised. ► The sensor is used to detect ciprofloxacin, ofloxacin, norfloxacin and gatifloxacin. ► Determine FQs drugs in pharmaceutical formulations and human serum samples. ► It showed high stability, repeatability, reproducibility, good sensitivity. -- Abstract: An electrochemical sensor for fluoroquinolones (FQs) based on polymerization of β-cyclodextrin (β-CD) and L-arginine (L-arg) modified carbon paste electrode (CPE) (P-β-CD-L-arg/CPE) was built for the first time. Synergistic effect of L-arg and β-CD was used to construct this sensor for quantification of these important antibiotics. Scanning electron microscope (SEM) image shows that polymer of β-CD and L-arg has been successfully modified on electrode. Electrochemical impedance spectroscopy (EIS) and cyclic voltammograms (CV) further indicate that polymer of β-CD and L-arg efficiently decreased the charge transfer resistance value of electrode and improved the electron transfer kinetic between analyte and electrode. Under the optimized conditions, this modified electrode was utilized to determine the concentrations of ciprofloxacin, ofloxacin, norfloxacin and gatifloxacin. The differential pulse voltammogram (DPV) exhibits the oxidation peak currents were linearly proportional to their concentration in the range of 0.05–100 μM for ciprofloxacin, 0.1–100 μM for ofloxacin, 0.1–40 μM for norfloxacin and 0.06–100 μM for gatifloxacin, respectively. This method was also successfully used to detect the concentrations of each drug in pharmaceutical

  8. A novel sensor based on electropolymerization of β-cyclodextrin and L-arginine on carbon paste electrode for determination of fluoroquinolones

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Fenfen [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Gu, Shuqing [Department of Chemistry, Shanghai University, Shanghai 200444 (China); School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Ding, Yaping, E-mail: wdingyp@sina.com [Department of Chemistry, Shanghai University, Shanghai 200444 (China); School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Zhang, Zhen [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); School of Chemistry and Chemical Engineering, Linyi University, 18 TongDa Road, Linyi 276005 (China); Li, Li [Department of Chemistry, Shanghai University, Shanghai 200444 (China)

    2013-04-03

    Graphical abstract: The inner cavities of β-CD could restrain fluoroquinolones to form stable host–guest inclusion complexes, and the guanidyl group of L-arg could enable L-arg to form electrostatic interactions with negatively charged groups -COO{sup −} of fluoroquinolones. Highlights: ► Electropolymerization of β-cyclodextrin and L-arginine on carbon paste electrode. ► The electrooxidation and reaction of FQs on the modified CPE were surmised. ► The sensor is used to detect ciprofloxacin, ofloxacin, norfloxacin and gatifloxacin. ► Determine FQs drugs in pharmaceutical formulations and human serum samples. ► It showed high stability, repeatability, reproducibility, good sensitivity. -- Abstract: An electrochemical sensor for fluoroquinolones (FQs) based on polymerization of β-cyclodextrin (β-CD) and L-arginine (L-arg) modified carbon paste electrode (CPE) (P-β-CD-L-arg/CPE) was built for the first time. Synergistic effect of L-arg and β-CD was used to construct this sensor for quantification of these important antibiotics. Scanning electron microscope (SEM) image shows that polymer of β-CD and L-arg has been successfully modified on electrode. Electrochemical impedance spectroscopy (EIS) and cyclic voltammograms (CV) further indicate that polymer of β-CD and L-arg efficiently decreased the charge transfer resistance value of electrode and improved the electron transfer kinetic between analyte and electrode. Under the optimized conditions, this modified electrode was utilized to determine the concentrations of ciprofloxacin, ofloxacin, norfloxacin and gatifloxacin. The differential pulse voltammogram (DPV) exhibits the oxidation peak currents were linearly proportional to their concentration in the range of 0.05–100 μM for ciprofloxacin, 0.1–100 μM for ofloxacin, 0.1–40 μM for norfloxacin and 0.06–100 μM for gatifloxacin, respectively. This method was also successfully used to detect the concentrations of each drug in

  9. Study on intercalation of ionic liquid into montmorillonite and its property evaluation

    International Nuclear Information System (INIS)

    Takahashi, Chisato; Shirai, Takashi; Fuji, Masayoshi

    2012-01-01

    Present study report fabrication of a solid–liquid intercalated compound using montmorillonite and ionic liquid [IL; 1-Butyl-3-methylimidazolium tetrafluoroborate; ([BMIM][BF 4 ])]. The intercalation of IL into the interlayer of montmorillonite was revealed by swelling behavior measured by X-ray diffraction (XRD) and cation exchange capacity (CEC). The crystal swelling structure of intercalation compound was further evidenced by transmission electron microscope (TEM). From these results, the arrangement of [BMIM] + ions (cationic part of IL) into the unit layer were proposed. Furthermore, the montmorillonite showed electrical conductivity with the aid of IL. This demonstrates a successful attempt to fabricate a solid–liquid state nano-structure compound as possible transparent electrically conducting thin film. -- Highlights: ► Direct intercalation of ionic liquid into the montmorillonite was studied. ► The crystal swelling structure in liquid state was successfully characterized by TEM. ► We proposed the atomic arrangement of intercalated compound using ionic liquid. ► Ionic liquid is useful for fabricating an intercalated compound with electrical-conductivity.

  10. Processing and properties of polyethylene/montmorillonite nanocomposites

    Czech Academy of Sciences Publication Activity Database

    Měřínská, D.; Kubisova, H.; Kalendová, A.; Svoboda, P.; Hromádková, Jiřina

    2012-01-01

    Roč. 25, č. 1 (2012), s. 115-131 ISSN 0892-7057 Institutional research plan: CEZ:AV0Z40500505 Keywords : polymer nanocomposite * montmorillonite * polyethylene Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.750, year: 2012

  11. Coulometric determination of dissolved hydrogen with a multielectrolytic modified carbon felt electrode-based sensor.

    Science.gov (United States)

    Matsuura, Hiroaki; Yamawaki, Yosuke; Sasaki, Kosuke; Uchiyama, Shunichi

    2013-06-01

    A multielectrolytic modified carbon electrode (MEMCE) was fabricated by the electrolytic-oxidation/reduction processes. First, the functional groups containing nitrogen atoms such as amino group were introduced by the electrode oxidation of carbon felt electrode in an ammonium carbamate aqueous solution, and next, this electrode was electroreduced in sulfuric acid. The redox waves between hydrogen ion and hydrogen molecule at highly positive potential range appeared in the cyclic voltammogram obtained by MEMCE. A coulometric cell using MEMCE with a catalytic activity of electrooxidation of hydrogen molecule was constructed and was used for the measurement of dissolved hydrogen. The typical current vs. time curve was obtained by the repetitive measurement of the dissolved hydrogen. These curves indicated that the measurement of dissolved hydrogen was finished completely in a very short time (ca. 10 sec). A linear relationship was obtained between the electrical charge needed for the electrooxidation process of hydrogen molecule and dissolved hydrogen concentration. This indicates that the developed coulometric method can be used for the determination of the dissolved hydrogen concentration.

  12. Electrochemical Determination of Glycoalkaloids Using a Carbon Nanotubes-Phenylboronic Acid Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Huiying Wang

    2013-11-01

    Full Text Available A versatile strategy for electrochemical determination of glycoalkaloids (GAs was developed by using a carbon nanotubes-phenylboronic acid (CNTs-PBA modified glassy carbon electrode. PBA reacts with α-solanine and α-chaconine to form a cyclic ester, which could be utilized to detect GAs. This method allowed GA detection from 1 μM to 28 μM and the detection limit was 0.3 μM. Affinity interaction of GAs and immobilized PBA caused an essential change of the peak current. The CNT-PBA modified electrodes were sensitive for detection of GAs, and the peak current values were in quite good agreement with those measured by the sensors.

  13. Inorganic synthesis of Fe-Ca-Mg carbonates at low temperature

    NARCIS (Netherlands)

    Romanek, Christopher S.; Jiménez-López, Concepción; Navarro, Alejandro Rodriguez; Sánchez-Román, Monica; Sahai, Nita; Coleman, Max

    2009-01-01

    A set of free-drift experiments was undertaken to synthesize carbonates of mixed cation content (Fe, Ca, Mg) from solution at 25 and 70 °C to better understand the relationship between the mineralogy and composition of these phases and the solutions from which they precipitate. Metastable solid

  14. Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium

    International Nuclear Information System (INIS)

    Afkhami, Abbas; Bahiraei, Atousa; Madrakian, Tayyebeh

    2016-01-01

    A simple and highly sensitive sensor for the determination of diclofenac sodium based on gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode is reported. Scanning electron microscopy along with energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry was used to characterize the nanostructure and performance of the sensor and the results were compared with those obtained at the multi-walled carbon nanotube modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions diclofenac sodium gave linear response over the range of 0.03–200 μmol L −1 . The lower detection limits were found to be 0.02 μmol L −1 . The effect of common interferences on the current response of DS was investigated. The practical application of the modified electrode was demonstrated by measuring the concentration of diclofenac sodium in urine and pharmaceutical samples. This revealed that the gold nanoparticle/multiwalled carbon nanotube modified glassy carbon electrode shows excellent analytical performance for the determination of diclofenac sodium in terms of a very low detection limit, high sensitivity, very good accuracy, repeatability and reproducibility. - Highlights: • GCE was modified with multiwalled carbon nanotube and gold nanoparticles. • AuNP/MWCNT/GCE was used for the determination of diclofenac sodium. • Modified electrode was characterized by SEM, EDS and EIS. • The proposed method showed excellent analytical figures of merit. • This sensor was used for the determination of diclofenac sodium in real samples.

  15. Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium

    Energy Technology Data Exchange (ETDEWEB)

    Afkhami, Abbas, E-mail: afkhami@basu.ac.ir; Bahiraei, Atousa; Madrakian, Tayyebeh

    2016-02-01

    A simple and highly sensitive sensor for the determination of diclofenac sodium based on gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode is reported. Scanning electron microscopy along with energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry was used to characterize the nanostructure and performance of the sensor and the results were compared with those obtained at the multi-walled carbon nanotube modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions diclofenac sodium gave linear response over the range of 0.03–200 μmol L{sup −1}. The lower detection limits were found to be 0.02 μmol L{sup −1}. The effect of common interferences on the current response of DS was investigated. The practical application of the modified electrode was demonstrated by measuring the concentration of diclofenac sodium in urine and pharmaceutical samples. This revealed that the gold nanoparticle/multiwalled carbon nanotube modified glassy carbon electrode shows excellent analytical performance for the determination of diclofenac sodium in terms of a very low detection limit, high sensitivity, very good accuracy, repeatability and reproducibility. - Highlights: • GCE was modified with multiwalled carbon nanotube and gold nanoparticles. • AuNP/MWCNT/GCE was used for the determination of diclofenac sodium. • Modified electrode was characterized by SEM, EDS and EIS. • The proposed method showed excellent analytical figures of merit. • This sensor was used for the determination of diclofenac sodium in real samples.

  16. An all-solid-state screen-printed carbon paste reference electrode based on poly(3,4-ethylenedioxythiophene) as solid contact transducer

    International Nuclear Information System (INIS)

    Xu, Hui; Pan, Yiwen; Chen, Ying; Ye, Ying; Wang, You; Li, Guang

    2012-01-01

    The paper presents the design of an all-solid-state portable reference electrode based on a screen-printed carbon paste electrode suitable for rapid human serum testing. The electrode was covered by electropolymerized poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS) as an internal solid contact layer and polyvinyl chloride (PVC) membrane containing lipophilic anion and cation additives. The electrochemical properties of PEDOT(PSS) and PEDOT(PSS)/PVC film on a carbon paste electrode were studied by electrochemical impedance spectroscopy and cyclic voltammetry methods. The reference electrode exhibited good potential stability (for H + , Na + , K + , Ca 2+ , Cl − and CO 2− 3 /HCO − 3 ), good reproducibility and long-term stability. The structure is applied as reference electrodes in human serum pH analysis with pH ion selective planar electrodes, forming a serum pH sensor. The response time of such a pH sensor was 15 s and the sensitivity was −52.2 ± 1.0 mV per decade. Other properties, such as repeatability, reproducibility and stability, were also evaluated. Clinical trials were carried out and compared with the results obtained from the routine hospital electrolyte analyzer, which demonstrated that their analytical performance was closely matched. (paper)

  17. Experimental and theoretical study of Co sorption in clay montmorillonites

    Science.gov (United States)

    Gil Rebaza, A. V.; Montes, M. L.; Taylor, M. A.; Errico, L. A.; Alonso, R. E.

    2018-03-01

    Montmorillonite (MMT) clays are 2:1 layered structures which in natural state may allocate different hydrated cations such as M-nH2O (M = Na, Ca, Fe, etc) in its interlayer space. Depending on the capability for ion sorption, these materials are interesting for environmental remediation. In this work we experimentally study the Co sorption in a natural Na-MMT using UV-visible spectrometry and XRD on semi-oriented samples, and then analyze the sorption ability of this clay by means of ab initio calculation performed on pristine MMT. The structural properties of Na-MMT and Co-adsorbed MMT, and the hyperfine parameters at different atomic sites were analyzed and compared with the experimental ones for the first, and for the case of the hyperfine parameters, presented for the first time for the last. The theoretical predictions based on total energy considerations confirm that Co incorporation replacing Na is energetically favorable. Also, the basal spacing d001 experimentally obtained is well reproduced.

  18. The site of net absorption of Ca from the intestinal tract of growing pigs and effect of phytic acid, Ca level and Ca source on Ca digestibility.

    Science.gov (United States)

    González-Vega, J Caroline; Walk, Carrie L; Liu, Yanhong; Stein, Hans H

    2014-01-01

    An experiment was conducted to test the hypothesis that the standardised digestibility of Ca in calcium carbonate and Lithothamnium calcareum Ca is not different regardless of the level of dietary Ca, and that phytic acid affects the digestibility of Ca in these two ingredients to the same degree. The objectives were to determine where in the intestinal tract Ca absorption takes place and if there are measurable quantities of basal endogenous Ca fluxes in the stomach, small intestine or large intestine. Diets contained calcium carbonate or L. calcareum Ca as the sole source of Ca, 0% or 1% phytic acid and 0.4% or 0.8% Ca. A Ca-free diet was also formulated and used to measure endogenous fluxes and losses of Ca. Nine growing pigs (initial body weight 23.8 ± 1.3 kg) were cannulated in the duodenum and in the distal ileum, and faecal, ileal and duodenal samples were collected. Duodenal endogenous fluxes of Ca were greater (p calcareum Ca diets, but that was not the case if calcium carbonate was the source of Ca (interaction, p calcareum Ca was greater (p calcareum Ca. In conclusion, under the conditions of this experiment, standardised digestibility of Ca is not affected by the level of phytic acid, but may be affected by dietary Ca level depending on the Ca source. Calcium from calcium carbonate is mostly absorbed before the duodenum, but Ca from L. calcareum Ca is mostly absorbed in the jejunum and ileum.

  19. Fabrication of nanostructured clay-carbon nanotube hybrid nanofiller by chemical vapour deposition

    International Nuclear Information System (INIS)

    Manikandan, Dhanagopal; Mangalaraja, Ramalinga Viswanathan; Siddheswaran, Rajendran; Avila, Ricardo E.; Ananthakumar, Solaiappan

    2012-01-01

    Growth of multiwalled carbon nanotube (CNT) assemblies by chemical vapour decomposition (CVD) technique was achieved through decomposition of acetylene using iron impregnated montmorillonite (MM) catalysts. Various amounts of iron loaded montmorillonite catalysts were prepared by wet impregnation method and calcined at 450 °C. The catalysts were subjected to X-ray diffraction (XRD) and surface area analyses. Acetylene decomposition at a feed ratio of N 2 :H 2 :C 2 H 2 = 1:1:0.18 was conducted in the presence of iron impregnated montmorillonite catalysts in the CVD reactor for the growth of CNT structures. The role of Fe-activated clay catalyst on the formation of CNT structures has been systematically examined at various temperatures and correlated with the morphological features of CNTs. Catalyst assisted acetylene decomposition results the formation of different carbon nanostructures such as nanotubes, nanofibres and nanoflakes. These clay-CNT products were characterised for their morphological, thermal, qualitative and quantitative analyses. The morphological variations of CNT assemblies reveal Fe-montmorillonite catalysts have high selectivity at given reaction conditions. Thermogravimetric and Raman spectral analyses prove that the CNTs contain a good crystallanity and less structural defects.

  20. Fabrication of nanostructured clay-carbon nanotube hybrid nanofiller by chemical vapour deposition

    Energy Technology Data Exchange (ETDEWEB)

    Manikandan, Dhanagopal, E-mail: dmani_cat@yahoo.co.in [Department of Materials Engineering, Faculty of Engineering, University of Concepcion, Concepcion (Chile); Mangalaraja, Ramalinga Viswanathan, E-mail: mangal@udec.cl [Department of Materials Engineering, Faculty of Engineering, University of Concepcion, Concepcion (Chile); Siddheswaran, Rajendran [Department of Materials Engineering, Faculty of Engineering, University of Concepcion, Concepcion (Chile); Avila, Ricardo E. [Personal Dosimetry Section, Chilean Nuclear Energy Commission, Santiago (Chile); Ananthakumar, Solaiappan [Materials and Minerals Division, National Institute for Interdisciplinary Science and Technology (NIIST), Trivandrum, Kerala (India)

    2012-03-01

    Growth of multiwalled carbon nanotube (CNT) assemblies by chemical vapour decomposition (CVD) technique was achieved through decomposition of acetylene using iron impregnated montmorillonite (MM) catalysts. Various amounts of iron loaded montmorillonite catalysts were prepared by wet impregnation method and calcined at 450 Degree-Sign C. The catalysts were subjected to X-ray diffraction (XRD) and surface area analyses. Acetylene decomposition at a feed ratio of N{sub 2}:H{sub 2}:C{sub 2}H{sub 2} = 1:1:0.18 was conducted in the presence of iron impregnated montmorillonite catalysts in the CVD reactor for the growth of CNT structures. The role of Fe-activated clay catalyst on the formation of CNT structures has been systematically examined at various temperatures and correlated with the morphological features of CNTs. Catalyst assisted acetylene decomposition results the formation of different carbon nanostructures such as nanotubes, nanofibres and nanoflakes. These clay-CNT products were characterised for their morphological, thermal, qualitative and quantitative analyses. The morphological variations of CNT assemblies reveal Fe-montmorillonite catalysts have high selectivity at given reaction conditions. Thermogravimetric and Raman spectral analyses prove that the CNTs contain a good crystallanity and less structural defects.

  1. Process for derivatizing carbon nanotubes with diazonium species

    Science.gov (United States)

    Tour, James M. (Inventor); Bahr, Jeffrey L. (Inventor); Yang, Jiping (Inventor)

    2007-01-01

    The invention incorporates new processes for the chemical modification of carbon nanotubes. Such processes involve the derivatization of multi- and single-wall carbon nanotubes, including small diameter (ca. 0.7 nm) single-wall carbon nanotubes, with diazonium species. The method allows the chemical attachment of a variety of organic compounds to the side and ends of carbon nanotubes. These chemically modified nanotubes have applications in polymer composite materials, molecular electronic applications and sensor devices. The methods of derivatization include electrochemical induced reactions thermally induced reactions (via in-situ generation of diazonium compounds or pre-formed diazonium compounds), and photochemically induced reactions. The derivatization causes significant changes in the spectroscopic properties of the nanotubes. The estimated degree of functionality is ca. 1 out of every 20 to 30 carbons in a nanotube bearing a functionality moiety. Such electrochemical reduction processes can be adapted to apply site-selective chemical functionalization of nanotubes. Moreover, when modified with suitable chemical groups, the derivatized nanotubes are chemically compatible with a polymer matrix, allowing transfer of the properties of the nanotubes (such as, mechanical strength or electrical conductivity) to the properties of the composite material as a whole. Furthermore, when modified with suitable chemical groups, the groups can be polymerized to form a polymer that includes carbon nanotubes ##STR00001##.

  2. Simultaneous determination of Sunset yellow and Tartrazine in soft drinks using gold nanoparticles carbon paste electrode.

    Science.gov (United States)

    Ghoreishi, Sayed Mehdi; Behpour, Mohsen; Golestaneh, Mahshid

    2012-05-01

    The monitoring of synthetic dyes in foods is very important due to their potential harmfulness to human beings. Herein, a carbon-paste electrode (CPE) that is chemically modified with gold nanoparticles (nAu) was fabricated and used for the determination of Sunset yellow (SY) and Tartrazine (Tz). Cyclic and differential pulse voltammetry (CV and DPV) results revealed two well-resolved anodic peaks for SY and Tz with remarkably increase in oxidation signals of these colourants. Based on this, a novel electrochemical method was developed for the simultaneous determination of SY and Tz. High sensitivity and selectivity, sub-micromolar detection limit, high reproducibility and regeneration of the electrode surface by simple polishing make the nAu-CPE electrode very suitable for the determination of SY and Tz in commercially available soft drinks. The detection limits was 3.0×10(-8) and 2.0×10(-9)moll(-1) for SY and Tz, respectively, which are remarkably lower than those reported previously for SY and Tz using other modified electrodes. Copyright © 2011 Elsevier Ltd. All rights reserved.

  3. Cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode as electrochemical sensor on microfluidic chip

    International Nuclear Information System (INIS)

    Li Xinchun; Chen Zuanguang; Zhong Yuwen; Yang Fan; Pan Jianbin; Liang Yajing

    2012-01-01

    Highlights: ► CoHCF nanoparticles modified MWCNTs/graphite electrode use for electrochemistry on electrophoresis microchip for the first time. ► Simultaneous, rapid, and sensitive electrochemical detection of hydrazine and isoniazid in real samples. ► An exemplary work of CME sensor assembly onto microchip for determination of analytes with environmental significance. ► Manifestation of the applicability and flexibility of CME sensor for electroanalysis on microfluidic chip. - Abstract: Nanomaterial-based electrochemical sensor has received significant interest. In this work, cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode was electrochemically prepared and exploited as an amperometric detector for microchip electrophoresis. The prepared sensor displayed rapid and sensitive response towards hydrazine and isoniazid oxidation, which was attributed to synergetic electrocatalytic effect of cobalt hexacyanoferrate and multi-walled carbon nanotubes. The sensitivity enhancement with nearly two orders of magnitude was gained, compared with the bare carbon paste electrode, with the detection limit of 0.91 μM (S/N = 3) for hydrazine. Acceptable repeatability of the microanalysis system was verified by consecutive eleven injections of hydrazine without chip and electrode treatments, the RSDs for peak current and migration time were 3.4% and 2.1%, respectively. Meanwhile, well-shaped electrophoretic peaks were observed, mainly due to fast electron transfer of electroactive species on the modified electrode. The developed microchip-electrochemistry setup was successfully applied to the determination of hydrazine and isoniazid in river water and pharmaceutical preparation, respectively. Several merits of the novel electrochemical sensor coupled with microfluidic platform, such as comparative stability, easy fabrication and high sensitivity, hold great potential for hydrazine compounds assay in the lab-on-a-chip system.

  4. THERMODINAMIC PARAMETERS ON THE SORPTION OF PHOSPHATE IONS BY MONTMORILLONITE

    Directory of Open Access Journals (Sweden)

    Ikhsan Jaslin

    2016-04-01

    Full Text Available The sorption of phosphate by montmorillonite at 10, 30, and 50 oC were investigated aiming to mainly determine thermodynamic parameters for the formation of surface complexes in the adsorption of phosphate ions by montmorillonite. Data were collected by adsorption edge experiments investigating the effect of pH, adsorption isotherms enabling the effect of sorbate concentration, and acid-base titration calculating protons released or taken up by adsorption process. Data analysis was carried out using surface complexation model to fit the data collected in this study using the parameters obtained from previous study, as well as to calculate the values of ΔH and ΔS. Previous study reported that phosphate ions formed two outer-sphere surface complexes with active sites of montmorillonite through hydrogen bonding. In the first complex,  [(XH0– H2L─]─, the phosphate was held to permanent-charge X─ sites on the tetrahedral siloxane faces, and the second complex, [[(SO─(SOH]– – [H2L]─] 2─ was formed through the interaction between the phosphate and variable charge surface hydroxyl groups at the edges of montmorillonite crystals and on the octahedral alumina faces. The values of ΔH for the first and second reactions are 39.756 and 3.765x10-7 kJ mol‒1 respectively. Since both reactions have positive enthalpy values, it can be concluded that the reactions are endothermic. Large energy for the first reaction is needed by X─  sites (permanent negatively charge sites of montmorillonite to be partially desolvated, on which K+ or other surface cations are replaced by H+ ions in the surface protonated process, and are then ready to interact phosphate ions in the solution. Small values of ΔH for the second reactions indicates that hydrogen bonds formed by phosphate and SOH sites in the second reaction are easily broken out, and the phosphate can easily desorbed from the surface. The values of ΔS for the first and second reactions are

  5. Electrocatalysis of oxygen reduction on nitrogen-containing multi-walled carbon nanotube modified glassy carbon electrodes

    International Nuclear Information System (INIS)

    Vikkisk, Merilin; Kruusenberg, Ivar; Joost, Urmas; Shulga, Eugene; Tammeveski, Kaido

    2013-01-01

    Highlights: ► Pyrolysis in the presence of urea was used for nitrogen doping of carbon nanotubes. ► N-doped carbon nanotubes were used as catalysts for the oxygen reduction reaction. ► N-doped carbon material showed a high catalytic activity for ORR in alkaline media. ► N-containing CNT material is an attractive cathode catalyst for alkaline membrane fuel cells. - Abstract: The electrochemical reduction of oxygen was studied on nitrogen-doped multi-walled carbon nanotube (NCNT) modified glassy carbon (GC) electrodes employing the rotating disk electrode (RDE) method. Nitrogen doping was achieved by simple pyrolysis of the carbon nanotube material in the presence of urea. The surface morphology and composition of the NCNT samples were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The SEM images revealed a rather uniform distribution of NCNTs on the GC electrode substrate. The XPS analysis showed a successful doping of carbon nanotubes with nitrogen species. The RDE results revealed that in alkaline solution the N-doped nanotube materials showed a remarkable electrocatalytic activity towards oxygen reduction. At low overpotentials the reduction of oxygen followed a two-electron pathway on undoped carbon nanotube modified GC electrodes, whereas on NCNT/GC electrodes a four-electron pathway of O 2 reduction predominated. The results obtained are significant for the development of nitrogen-doped carbon-based cathodes for alkaline membrane fuel cells.

  6. Evaluation of particle release from montmorillonite gel by flowing groundwater based on the DLVO theory

    International Nuclear Information System (INIS)

    Kurosawa, Susumu; Nagasaki, Shinya; Tanaka, Satoru

    2007-01-01

    Theoretical study has been performed to clarify the ability of colloid release form the montmorillonite gel by the flowing groundwater. Evaluation of montmorillonite colloidal particles release from the bentonite buffer material is important for the performance assessment of radioactive waste disposal because the colloids may influence the radionuclide transport. In this study, the minimum groundwater flow rate required to tear off montmorillonite particles from surface of bentonite buffer was estimated from the shear stress on the gel front, which was calculated by the DLVO theory. The estimated shear force was converted to corresponding groundwater velocity by using Stoke's equation. The results indicated that groundwater velocity in a range of about 10 -5 to 10 -4 m/s would be necessary to release montmorillonite particles. This range is higher than the groundwater flow velocity found generally in deep geological media in Japan. This study suggests that the effect of montmorillonite particles release from the bentonite buffer on radionuclide transport is likely to be negligible in the performance assessment of high-level radioactive waste geological disposal. (author)

  7. Gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode as a sensitive voltammetric sensor for the determination of diclofenac sodium.

    Science.gov (United States)

    Afkhami, Abbas; Bahiraei, Atousa; Madrakian, Tayyebeh

    2016-02-01

    A simple and highly sensitive sensor for the determination of diclofenac sodium based on gold nanoparticle/multi-walled carbon nanotube modified glassy carbon electrode is reported. Scanning electron microscopy along with energy dispersive X-ray spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and square wave voltammetry was used to characterize the nanostructure and performance of the sensor and the results were compared with those obtained at the multi-walled carbon nanotube modified glassy carbon electrode and bare glassy carbon electrode. Under the optimized experimental conditions diclofenac sodium gave linear response over the range of 0.03-200μmolL(-1). The lower detection limits were found to be 0.02μmolL(-1). The effect of common interferences on the current response of DS was investigated. The practical application of the modified electrode was demonstrated by measuring the concentration of diclofenac sodium in urine and pharmaceutical samples. This revealed that the gold nanoparticle/multiwalled carbon nanotube modified glassy carbon electrode shows excellent analytical performance for the determination of diclofenac sodium in terms of a very low detection limit, high sensitivity, very good accuracy, repeatability and reproducibility. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Electrochemical determination of paraquat in citric fruit based on electrodeposition of silver particles onto carbon paste electrode.

    Science.gov (United States)

    Farahi, Abdelfettah; Achak, Mounia; El Gaini, Laila; El Mhammedi, Moulay Abderrahim; Bakasse, Mina

    2015-09-01

    Carbon paste electrodes (CPEs) modified with silver particles present an interesting tool in the determination of paraquat (PQ) using square wave voltammetry. Metallic silver particle deposits have been obtained via electrochemical deposition in acidic media using cyclic voltammetry. Scanning electron microscopy and X-ray diffraction measurements show that the silver particles are deposited onto carbon surfaces in aggregate form. The response of PQ with modified electrode (Ag-CPE) related to Ag/CP loading, preconcentration time, and measuring solution pH was investigated. The result shows that the increase in the two cathodic peak currents (Peak 1 and Peak 2), under optimized conditions, was linear with the increase in PQ concentration in the range 1.0 × 10 -7  mol/L to 1.0 × 10 -3  mol/L. The detection limit and quantification limit were 2.01 × 10 -8  mol/L and 6.073 × 10 -8  mol/L, respectively for Peak 1. The precision expressed as relative standard deviation for the concentration level 1.0 × 10 -5  mol/L (n = 8) was found to be 1.45%. The methodology was satisfactorily applied for the determination of PQ in citric fruit cultures. Copyright © 2015. Published by Elsevier B.V.

  9. Electrochemical determination of paraquat in citric fruit based on electrodeposition of silver particles onto carbon paste electrode

    Directory of Open Access Journals (Sweden)

    Abdelfettah Farahi

    2015-09-01

    Full Text Available Carbon paste electrodes (CPEs modified with silver particles present an interesting tool in the determination of paraquat (PQ using square wave voltammetry. Metallic silver particle deposits have been obtained via electrochemical deposition in acidic media using cyclic voltammetry. Scanning electron microscopy and X-ray diffraction measurements show that the silver particles are deposited onto carbon surfaces in aggregate form. The response of PQ with modified electrode (Ag-CPE related to Ag/CP loading, preconcentration time, and measuring solution pH was investigated. The result shows that the increase in the two cathodic peak currents (Peak 1 and Peak 2, under optimized conditions, was linear with the increase in PQ concentration in the range 1.0 × 10−7 mol/L to 1.0 × 10−3 mol/L. The detection limit and quantification limit were 2.01 × 10−8 mol/L and 6.073 × 10−8 mol/L, respectively for Peak 1. The precision expressed as relative standard deviation for the concentration level 1.0 × 10−5 mol/L (n = 8 was found to be 1.45%. The methodology was satisfactorily applied for the determination of PQ in citric fruit cultures.

  10. Mobility of adsorbed Cry1Aa insecticidal toxin from Bacillus thuringiensis (Bt) on montmorillonite measured by fluorescence recovery after photobleaching (FRAP)

    Science.gov (United States)

    Helassa, Nordine; Daudin, Gabrielle; Noinville, Sylvie; Janot, Jean-Marc; Déjardin, Philippe; Staunton, Siobhán; Quiquampoix, Hervé

    2010-06-01

    The insecticidal toxins produced by genetically modified Bt crops are introduced into soil through root exudates and tissue decomposition and adsorb readily on soil components, especially on clays. This immobilisation and the consequent concentration of the toxins in "hot spots" could increase the exposure of soil organisms. Whereas the effects on non-target organisms are well documented, few studies consider the migration of the toxin in soil. In this study, the residual mobility of Bt Cry1Aa insecticidal toxin adsorbed on montmorillonite was assessed using fluorescence recovery after photobleaching (FRAP). This technique, which is usually used to study dynamics of cytoplasmic and membrane molecules in live cells, was applied for the first time to a protein adsorbed on a finely divided swelling clay mineral, montmorillonite. No mobility of adsorbed toxin was observed at any pH and at different degrees of surface saturation.

  11. Controlled release of agrochemicals intercalated into montmorillonite interlayer space.

    Science.gov (United States)

    Wanyika, Harrison

    2014-01-01

    Periodic application of agrochemicals has led to high cost of production and serious environmental pollution. In this study, the ability of montmorillonite (MMT) clay to act as a controlled release carrier for model agrochemical molecules has been investigated. Urea was loaded into MMT by a simple immersion technique while loading of metalaxyl was achieved by a rotary evaporation method. The successful incorporation of the agrochemicals into the interlayer space of MMT was confirmed by several techniques, such as, significant expansion of the interlayer space, reduction of Barrett-Joyner-Halenda (BJH) pore volumes and Brunauer-Emmett-Teller (BET) surface areas, and appearance of urea and metalaxyl characteristic bands on the Fourier-transform infrared spectra of the urea loaded montmorillonite (UMMT) and metalaxyl loaded montmorillonite (RMMT) complexes. Controlled release of the trapped molecules from the matrix was done in water and in the soil. The results reveal slow and sustained release behaviour for UMMT for a period of 10 days in soil. For a period of 30 days, MMT delayed the release of metalaxyl in soil by more than 6 times. It is evident that MMT could be used to improve the efficiency of urea and metalaxyl delivery in the soil.

  12. Study on electroactive and electrocatalytic surfaces of single walled carbon nanotube-modified electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Salinas-Torres, David [Departamento de Quimica Fisica and Instituto Universitario de Materiales de Alicante, Universidad de Alicante, Apdo. de Correos 99, E-03080 Alicante (Spain); Huerta, Francisco [Departamento de Ingenieria Textil y Papelera, Universidad Politecnica de Valencia, Plaza Ferrandiz y Carbonell, 1. E-03801 Alcoy (Spain); Montilla, Francisco, E-mail: francisco.montilla@ua.e [Departamento de Quimica Fisica and Instituto Universitario de Materiales de Alicante, Universidad de Alicante, Apdo. de Correos 99, E-03080 Alicante (Spain); Morallon, Emilia [Departamento de Quimica Fisica and Instituto Universitario de Materiales de Alicante, Universidad de Alicante, Apdo. de Correos 99, E-03080 Alicante (Spain)

    2011-02-01

    An investigation of the electrocatalysis of single-walled carbon nanotubes modified electrodes has been performed in this work. Nanotube-modified electrodes present a surface area much higher than the bare glassy carbon surfaces as determined by capacitance measurements. Several redox probes were selected for checking the reactivity of specific sites at the carbon nanotube surface. The presence of carbon nanotubes on the electrode improves the kinetics for all the reactions studied compared with the bare glassy carbon electrode with variations of the heterogeneous electron transfer rate constant up to 5 orders of magnitude. The most important effects are observed for the benzoquinone/hydroquinone and ferrocene/ferricinium redox couples, which show a remarkable improvement of their electron transfer kinetics on SWCNT-modified electrodes, probably due to strong {pi}-{pi} interaction between the organic molecules and the walls of the carbon nanotubes. For many of the reactions studied, less than 1% of the nanotube-modified electrode surface is transferring charge to species in solution. This result suggests that only nanotube tips are active sites for the electron transfer in such cases. On the contrary, the electroactive surface for the reactions of ferrocene and quinone is higher indicating that the electron transfer is produced also from the nanotube walls.

  13. Study on electroactive and electrocatalytic surfaces of single walled carbon nanotube-modified electrodes

    International Nuclear Information System (INIS)

    Salinas-Torres, David; Huerta, Francisco; Montilla, Francisco; Morallon, Emilia

    2011-01-01

    An investigation of the electrocatalysis of single-walled carbon nanotubes modified electrodes has been performed in this work. Nanotube-modified electrodes present a surface area much higher than the bare glassy carbon surfaces as determined by capacitance measurements. Several redox probes were selected for checking the reactivity of specific sites at the carbon nanotube surface. The presence of carbon nanotubes on the electrode improves the kinetics for all the reactions studied compared with the bare glassy carbon electrode with variations of the heterogeneous electron transfer rate constant up to 5 orders of magnitude. The most important effects are observed for the benzoquinone/hydroquinone and ferrocene/ferricinium redox couples, which show a remarkable improvement of their electron transfer kinetics on SWCNT-modified electrodes, probably due to strong π-π interaction between the organic molecules and the walls of the carbon nanotubes. For many of the reactions studied, less than 1% of the nanotube-modified electrode surface is transferring charge to species in solution. This result suggests that only nanotube tips are active sites for the electron transfer in such cases. On the contrary, the electroactive surface for the reactions of ferrocene and quinone is higher indicating that the electron transfer is produced also from the nanotube walls.

  14. Sorption of trivalent lanthanides and actinides onto montmorillonite: Macroscopic, thermodynamic and structural evidence for ternary hydroxo and carbonato surface complexes on multiple sorption sites.

    Science.gov (United States)

    Fernandes, M Marques; Scheinost, A C; Baeyens, B

    2016-08-01

    The credibility of long-term safety assessments of radioactive waste repositories may be greatly enhanced by a molecular level understanding of the sorption processes onto individual minerals present in the near- and far-fields. In this study we couple macroscopic sorption experiments to surface complexation modelling and spectroscopic investigations, including extended X-ray absorption fine structure (EXAFS) and time-resolved laser fluorescence spectroscopies (TRLFS), to elucidate the uptake mechanism of trivalent lanthanides and actinides (Ln/An(III)) by montmorillonite in the absence and presence of dissolved carbonate. Based on the experimental sorption isotherms for the carbonate-free system, the previously developed 2 site protolysis non electrostatic surface complexation and cation exchange (2SPNE SC/CE) model needed to be complemented with an additional surface complexation reaction onto weak sites. The fitting of sorption isotherms in the presence of carbonate required refinement of the previously published model by reducing the strong site capacity and by adding the formation of Ln/An(III)-carbonato complexes both on strong and weak sites. EXAFS spectra of selected Am samples and TRLFS spectra of selected Cm samples corroborate the model assumptions by showing the existence of different surface complexation sites and evidencing the formation of Ln/An(III) carbonate surface complexes. In the absence of carbonate and at low loadings, Ln/An(III) form strong inner-sphere complexes through binding to three Al(O,OH)6 octahedra, most likely by occupying vacant sites in the octahedral layers of montmorillonite, which are exposed on {010} and {110} edge faces. At higher loadings, Ln/An(III) binds to only one Al octahedron, forming a weaker, edge-sharing surface complex. In the presence of carbonate, we identified a ternary mono- or dicarbonato Ln/An(III) complex binding directly to one Al(O,OH)6 octahedron, revealing that type-A ternary complexes form with the one

  15. Montmorillonite stability under near-field conditions

    International Nuclear Information System (INIS)

    Leupin, O.X.; Korkeakoski, P.; Sellin, P.; Mäder, U.; Wersin, P.

    2014-07-01

    Clay-based engineered barriers comprising bentonite and bentonite/sand mixtures are the favoured option in geological repositories for high-level waste due to their inherently low hydraulic conductivity at full saturation. This ensures that diffusion of solutes such as radionuclides will be the dominating mechanism for transport through the engineered barriers. Another advantageous property of bentonite is the development of swelling pressure in contact with water under the constant volume conditions of repository excavations, ensuring the closure of unintentional gaps or openings. The predictability of the long-term behaviour of bentonite (up to a million years) is thus key to the safety analysis. The thermal pulse from the radioactive decay of the radionuclides in the high-level waste and spent fuel will lead to temperatures significantly higher than in the undisturbed host rock for hundreds of years, which may influence the thermodynamic stability and kinetics of alteration reactions of montmorillonite, the smectite that is the main constituent of the bentonite. The aim of this report is to review the present understanding of potential alteration of bentonite by focusing on experimental and modeling results under the thermal conditions of a repository. Many studies show that the transformation of smectite-to-illite is induced by increasing temperature and potassium activity. The conversion process is complex and still not completely understood. Nonetheless, it displays very slow kinetics over a wide range of environmental conditions for the temperatures of interest. The various models for illitisation of smectites suggest negligible transformation in a repository due to the relatively short period of elevated temperatures and slow mass transport. However, because of uncertainties and a number of conservatisms in the application of such models, the results of such calculations should be considered as bounding and indicative and not as quantitative predictions. In

  16. Montmorillonite stability under near-field conditions

    Energy Technology Data Exchange (ETDEWEB)

    Leupin, O.X. (ed.); Birgersson, M.; Karnland, O. [Clay Technology AB, Lund (Sweden); Korkeakoski, P. [Posiva Oy, Eurajoki (Finland); Sellin, P. [Svensk Kärnbränslehantering AB, SKB, Stockholm (USSR); Mäder, U.; Wersin, P. [University of Berne, Berne (Switzerland)

    2014-07-15

    Clay-based engineered barriers comprising bentonite and bentonite/sand mixtures are the favoured option in geological repositories for high-level waste due to their inherently low hydraulic conductivity at full saturation. This ensures that diffusion of solutes such as radionuclides will be the dominating mechanism for transport through the engineered barriers. Another advantageous property of bentonite is the development of swelling pressure in contact with water under the constant volume conditions of repository excavations, ensuring the closure of unintentional gaps or openings. The predictability of the long-term behaviour of bentonite (up to a million years) is thus key to the safety analysis. The thermal pulse from the radioactive decay of the radionuclides in the high-level waste and spent fuel will lead to temperatures significantly higher than in the undisturbed host rock for hundreds of years, which may influence the thermodynamic stability and kinetics of alteration reactions of montmorillonite, the smectite that is the main constituent of the bentonite. The aim of this report is to review the present understanding of potential alteration of bentonite by focusing on experimental and modeling results under the thermal conditions of a repository. Many studies show that the transformation of smectite-to-illite is induced by increasing temperature and potassium activity. The conversion process is complex and still not completely understood. Nonetheless, it displays very slow kinetics over a wide range of environmental conditions for the temperatures of interest. The various models for illitisation of smectites suggest negligible transformation in a repository due to the relatively short period of elevated temperatures and slow mass transport. However, because of uncertainties and a number of conservatisms in the application of such models, the results of such calculations should be considered as bounding and indicative and not as quantitative predictions. In

  17. Fish as major carbonate mud producers and missing components of the tropical carbonate factory

    Science.gov (United States)

    Perry, Chris T.; Salter, Michael A.; Harborne, Alastair R.; Crowley, Stephen F.; Jelks, Howard L.; Wilson, Rod W.

    2011-01-01

    Carbonate mud is a major constituent of recent marine carbonate sediments and of ancient limestones, which contain unique records of changes in ocean chemistry and climate shifts in the geological past. However, the origin of carbonate mud is controversial and often problematic to resolve. Here we show that tropical marine fish produce and excrete various forms of precipitated (nonskeletal) calcium carbonate from their guts ("low" and "high" Mg-calcite and aragonite), but that very fine-grained (mostly 4 mole % MgCO3) are their dominant excretory product. Crystallites from fish are morphologically diverse and species-specific, but all are unique relative to previously known biogenic and abiotic sources of carbonate within open marine systems. Using site specific fish biomass and carbonate excretion rate data we estimate that fish produce ~6.1 x 106 kg CaCO3/year across the Bahamian archipelago, all as mud-grade (the marine carbonate factories function both today and in the past.

  18. Prebiotic RNA Synthesis by Montmorillonite Catalysis

    Directory of Open Access Journals (Sweden)

    Sohan Jheeta

    2014-08-01

    Full Text Available This review summarizes our recent findings on the role of mineral salts in prebiotic RNA synthesis, which is catalyzed by montmorillonite clay minerals. The clay minerals not only catalyze the synthesis of RNA but also facilitate homochiral selection. Preliminary data of these findings have been presented at the “Horizontal Gene Transfer and the Last Universal Common Ancestor (LUCA” conference at the Open University, Milton Keynes, UK, 5–6 September 2013. The objective of this meeting was to recognize the significance of RNA in LUCA. We believe that the prebiotic RNA synthesis from its monomers must have been a simple process. As a first step, it may have required activation of the 5'-end of the mononucleotide with a leaving group, e.g., imidazole in our model reaction (Figure 1. Wide ranges of activating groups are produced from HCN under plausible prebiotic Earth conditions. The final step is clay mineral catalysis in the presence of mineral salts to facilitate selective production of functional RNA. Both the clay minerals and mineral salts would have been abundant on early Earth. We have demonstrated that while montmorillonite (pH 7 produced only dimers from its monomers in water, addition of sodium chloride (1 M enhanced the chain length multifold, as detected by HPLC. The effect of monovalent cations on RNA synthesis was of the following order: Li+ > Na+ > K+. A similar effect was observed with the anions, enhancing catalysis in the following order: Cl− > Br− > I−. The montmorillonite-catalyzed RNA synthesis was not affected by hydrophobic or hydrophilic interactions. We thus show that prebiotic synthesis of RNA from its monomers was a simple process requiring only clay minerals and a small amount of salt.

  19. Hematoxylin multi-wall carbon nanotubes modified glassy carbon electrode for electrocatalytic oxidation of hydrazine

    International Nuclear Information System (INIS)

    Zare, Hamid R.; Nasirizadeh, Navid

    2007-01-01

    A new hydrazine sensor has been fabricated by immobilizing hematoxylin at the surface of a glassy carbon electrode (GCE) modified with multi-wall carbon nanotube (MWCNT). The adsorbed thin films of hematoxylin on the MWCNT modified GCE show one pair of peaks with surface confined characteristics. The hematoxylin MWCNT (HMWCNT) modified GCE shows highly catalytic activity toward hydrazine electro-oxidation. The results show that the peak potential of hydrazine at HMWCNT modified GCE surface shifted by about 167 and 255 mV toward negative values compared with that at an MWCNT and activated modified GCE surface, respectively. In addition, at HMWCNT modified electrode surface remarkably improvement the sensitivity of determination of hydrazine. The kinetic parameters, such as the electron transfer coefficient, α, and the standard heterogeneous rate constant, k 0 , for oxidation of hydrazine at the HMWCNT modified GCE were determined and also is shown that the heterogeneous rate constant, k', is strongly potential dependent. The overall number of electron involved in the catalytic oxidation of hydrazine and the number of electrons involved in the rate-determining steps are 2 and 1, respectively. The amperometric detection of hydrazine is carried out at 220 mV in 0.1 M phosphate buffer solution (pH 7) with linear response range 2.0-122.8 μM hydrazine, detection limit of 0.68 μM and sensitivity of 0.0208 μA μM -1 . Finally the amperometric response for hydrazine determination is reproducible, fast and extremely stable, with no loss in sensitivity over a continual 400 s operation

  20. ELECTROCHEMICAL DETERMINATION OF HYDROGEN SULFIDE AT CARBON NANOTUBE MODIFIED ELECTRODES. (R830900)

    Science.gov (United States)

    Carbon nanotube (CNT) modified glassy carbon electrodes exhibiting a strong and stable electrocatalytic response towards sulfide are described. A substantial (400 mV) decrease in the overvoltage of the sulfide oxidation reaction (compared to ordinary carbon electrodes) is...

  1. Rapid analysis of carbohydrates in aqueous extracts and hydrolysates of biomass using a carbonate-modified anion-exchange column.

    Science.gov (United States)

    Sevcik, Richard S; Mowery, Richard A; Becker, Christopher; Chambliss, C Kevin

    2011-03-04

    Quantitative liquid-chromatography techniques used to characterize carbohydrates present in biomass samples can suffer from long analysis times, limited analyte resolution, poor stability, or a combination of these factors. The current manuscript details a novel procedure enabling resolution of glucose, xylose, arabinose, galactose, mannose, fructose, and sucrose via isocratic elution in less than 5 min. Equivalent conditions also enable analysis of cellobiose and maltose with a minimal increase in chromatographic run time (ca. 3 and 6 min, respectively). Noted chromatographic performance requires that a commercially available anion-exchange column be modified with carbonate prior to analysis. Analytical performance of a modified column was assessed over a 5-day period via repeated analyses of 4 samples, resulting from aqueous extraction or quantitative saccharification of a potential biofuel feedstock (i.e., corn stover or switchgrass). A simple solid phase extraction procedure was utilized to clean up each sample prior to analysis. Analytical accuracy of the extraction protocol was assessed by evaluation of matrix spike recoveries which typically ranged from 84% to 98%. The instrumental variability of measured concentrations in real samples over the 5-day period was generally less than 5% RSD for all detected analytes, independent of sample type. Finally, it is important to note that the modified column exhibited exceptional stability over approximately 800 injections of biofeedstock-based samples. These data demonstrate that a carbonate-modified anion-exchange column can be employed for rapid determination of carbohydrates in biomass samples of lignocellulosic origin. Copyright © 2011 Elsevier B.V. All rights reserved.

  2. Carbon and nitrogen isotopic signatures of bat guanos as record of past environments

    International Nuclear Information System (INIS)

    Mizutani, Hiroshi; Kabaya, Yuko; McFarlane, D.A.

    1992-01-01

    Carbon and nitrogen isotope ratios were measured for various ecogeochemical samples relevant to bat guano ecosystems. In particular, ca. 800-year-old subfossil guano from Jackson's Bay Cave Compex, Jamaica, yielded ratios similar to the modern guano from other Jamaican bat caves but quite different from modern guano of the same area. Diagenetic change and differences in bat food habits were unlikely explanations for the observation. Instead, insects that feed on C 4 and CAM plants were the main prey for the bats in present Jackson's Bay area, while the ultimate source of organic matter for bats in other Jamaican caves and for the bats that deposited guano in Jackson's Bay Great Cave ca. 800 years ago were C 3 photosynthesis. We suggests that the isotopic data indicate that the surrounding environment experienced a significant mesic episode in the recent past. This mesic climate would have supported a large population of bats, which in turn would have accumulated significant quantities of guano. The subsequent return to the more xeric conditions prevailing today would have caused a drastic reduction in bat population size and effectively ended significant guano accumulation. Fossil guano from Carlsbad Caverns, New Mexico, U.S.A., suggested that native C 3 plants might have been more abundant in Wisconsinan than today. Isotope analyses of old guanos from Bat Cave in Grand Canyon National Park, Arizona, U.S.A., found a possible implication that C 4 photosynthesis might have had contributed a little more to the bats' diet in the cave before the construction of Glen Canyon Dam. (author)

  3. Sorption of 241Am onto montmorillonite, illite and hematite colloids

    International Nuclear Information System (INIS)

    Degueldre, C.; Ulrich, H.J.; Silby, H.

    1994-01-01

    Actinide sorption on colloids may be described as a competition between the formation of complexes in solution and the build up of surface complexes. The role of particle and of carbonate concentrations on the sorption/desorption of 241 Am on montmorillonite, illite and hematite colloids is investigated. Since the partition coefficient (K p ) values are virtually independent of the colloid concentrations, within the range 1 to 300 ppm, no significant aggregation takes place in the sorption/desorption experiment. At pH 8, a slight decrease of K p is observed if the concentration of total carbonate exceeds 10 -2 M. The formation of the carbonato- (and hydroxo-carbonato-) complexes in the solution competes with the formation of surface complexes on the colloids. A relationship between the sorption coefficient and the complexation of 241 Am in the solution has been found. This leads to the conclusion that, besides free americium cation, the hydroxo-, and carbonato- as well as the mixed hydroxo-carbonato-complexes are sorbed. Only when the tricarbonatocomplex [Am(CO 3 ) 3 ] 3- prevails (total carbonate concentration > 10 -2 M), a significant decrease of the distribution coefficient is observed. At pH 10 this decrease disappears because under these conditions the strong hydroxo-complexes dominate. A pragmatic and relatively simple application of surface complexation model describes the observed features. (orig.)

  4. Electrocatalytic determination of dopamine in the presence of uric acid using an indenedione derivative and multiwall carbon nanotubes spiked in carbon paste electrode

    Energy Technology Data Exchange (ETDEWEB)

    Nasirizadeh, Navid, E-mail: nasirizadeh@yahoo.com [Scientific Society of Nanotechnology, Yazd Branch, Islamic Azad University, Yazd (Iran, Islamic Republic of); Department of Textile Engineering, Yazd Branch, Islamic Azad University, Yazd (Iran, Islamic Republic of); Shekari, Zahra [Scientific Society of Nanotechnology, Yazd Branch, Islamic Azad University, Yazd (Iran, Islamic Republic of); Zare, Hamid R. [Department of Chemistry, Yazd University, P.O. Box 89195-741, Yazd (Iran, Islamic Republic of); Makarem, Somayeh [Department of Chemistry, Faculty of Sciences, ShahidBeheshti University, G. C., P. O. Box 19839-4716, Tehran (Iran, Islamic Republic of)

    2013-04-01

    In the present study, a modified carbon paste electrode (CPE) containing multi-wall carbon nanotubes and an indenedione derivative(IMWCNT−CPE) was constructed and was successfully used for dopamine(DA) electrocatalytic oxidation and simultaneous determination of DA and uric acid (UA). Cyclic voltammograms of the IMWCNT−CPE show a pair of well-defined and reversible redox. The obtained results indicate that the peak potential of DA oxidation at IMWCNT−CPE shifted by about 65 and 185 mV toward the negative values compared with that at a MWCNT and indenedione modified CPE, respectively. The electron transfer coefficient, α, and the heterogeneous electron transfer rate constant, k′, for the oxidation of DA at IMWCNT−CPE were calculated 0.4 ± 0.01 and (1.13 ± 0.03) × 10{sup −3} cm s{sup −1}, respectively. Furthermore, differential pulse voltammetry (DPV) exhibits two linear dynamic ranges of 1.9–79.4 μM, and 79.4–714.3 μM and a detection limit of 0.52 μM for DA determination. Then IMWCNT−CPE was applied to the simultaneous determination of DA and UA with DPV. Finally, the activity of the modified electrode was also investigated for determination of DA and UA in real samples, such as injection solution of DA and urine, with satisfactory results. - Highlights: ► According to referee's comment we have omitted references 33–35. ► Fig. 1 of the revised manuscript was improved based on referee comment. ► We have calculated the effective areas of MWCNT−CPE and unmodified CPE. ► Differential pulse voltammetry was used to estimate the quantitative parameters. ► Based on referee comment, the necessary corrections at the references list were mad.

  5. Preparation of poly (methyl methacrylate)/nanometer calcium carbonate composite by in-situ emulsion polymerization

    Institute of Scientific and Technical Information of China (English)

    史建明; 包永忠; 黄志明; 翁志学

    2004-01-01

    Methyl methacrylate (MMA) emulsion polymerization in the presence of nanometer calcium carbonate (nano-CaCO3) surface modified with (-methacryloxypropyltrimethoxysilane (MPTMS) was carried out to prepare poly (methyl methacrylate) (PMMA)/nano-CaCO3 composite. The reaction between nano-CaCO3 and MPTMS, and the grafting of PMMA onto nano-CaCO3 were confirmed by infrared spectrum. The grafting ratio and grafting efficiency of PMMA on nano-CaCO3 modified with MPTMS were much higher than that on nano-CaCO3 modified with stearic acid. The grafting ratio of PMMA increased as the weight ratio between MMA and nano-CaCO3 increased, while the grafting efficiency of PMMA decreased. Transmission electron micrograph showed that nano-CaCO3 covered with PMMA was formed by in-situ emulsion polymerization.

  6. Luminescence investigations of rare earth doped lead-free borate glasses modified by MO (M = Ca, Sr, Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Janek, Joanna, E-mail: janek.joanna@gmail.com; Sołtys, Marta; Żur, Lidia; Pietrasik, Ewa; Pisarska, Joanna; Pisarski, Wojciech A.

    2016-09-01

    Series of lead-free borate glasses with different oxide modifiers and lanthanide ions were prepared. The effect of oxide modifiers MO (M = Ca, Sr, Ba) on spectroscopic properties of trivalent Ln{sup 3+} (Ln = Eu, Er, Pr) were systematically investigated. Especially, the luminescence spectra of Ln{sup 3+}-doped lead-free borate glasses are presented and discussed in relation to the impact of selective components (CaO, SrO and BaO). Several spectroscopic parameters, such as the fluorescence intensity ratio R/O (Eu{sup 3+}) and measured luminescence lifetimes for the {sup 5}D{sub 0} (Eu{sup 3+}), {sup 4}I{sub 13/2} (Er{sup 3+}) and {sup 1}D{sub 2} (Pr{sup 3+}) excited states of lanthanide ions were analyzed in details. The research proved that spectroscopic properties of trivalent Ln{sup 3+} depend significantly on kind of presence oxide modifiers MO (M = Ca, Sr, Ba) in glass host matrices. - Highlights: • Luminescence of Ln{sup 3+}-doped borate glasses was presented and discussed. • Effect of glass modifiers on spectroscopic properties of rare earths was studied. • Measured luminescence lifetimes of Ln{sup 3+} (Ln = Eu, Er, Pr) were analyzed. • Luminescence intensity ratios R/O (Eu{sup 3+}) were determined.

  7. Effects of Graded Levels of Montmorillonite on Performance, Hematological Parameters and Bone Mineralization in Weaned Pigs

    Directory of Open Access Journals (Sweden)

    Q. W. Duan

    2013-11-01

    Full Text Available The aim of this study was to investigate the effects of graded levels of montmorillonite, a constituent of clay, on performance, hematological parameters and bone mineralization in weaned pigs. One hundred and twenty, 35-d-old crossbred pigs (Duroc×Large White×Landrace, 10.50±1.20 kg were used in a 28-d experiment and fed either an unsupplemented corn-soybean meal basal diet or similar diets supplemented with 0.5, 1.0, 2.5 or 5.0% montmorillonite added at the expense of wheat bran. Each treatment was replicated six times with four pigs (two barrows and two gilts per replicate. Feed intake declined (linear and quadratic effect, p< 0.01 with increasing level of montmorillonite while feed conversion was improved (linear and quadratic effect, p<0.01. Daily gain was unaffected by dietary treatment. Plasma myeloperoxidase declined linearly (p = 0.03 with increasing dietary level of montmorillonite. Plasma malondialdehyde and nitric oxide levels were quadratically affected (p<0.01 by montmorillonite with increases observed for pigs fed the 0.5 and 1.0% levels which then declined for pigs fed the 2.5 and 5.0% treatments. In bone, the content of potassium, sodium, copper, iron, manganese and magnesium were decreased (linear and quadratic effect, p<0.01 in response to an increase of dietary montmorillonite. These results suggest that dietary inclusion of montmorillonite at levels as high as 5.0% does not result in overt toxicity but could induce potential oxidative damage and reduce bone mineralization in pigs.

  8. Anti-tumor response with immunologically modified carbon nanotubes and phototherapy

    Science.gov (United States)

    Acquaviva, Joseph T.; Zhou, Feifan; Boarman, Ellen; Chen, Wei R.

    2013-02-01

    While successes of different cancer therapies have been achieved in various degrees a systemic immune response is needed to effectively treat late-stage, metastatic cancers, and to establish long-term tumor resistance in the patients. A novel method for combating metastatic cancers has been developed using immunologically modified carbon nanotubes in conjunction with phototherapy. Glycated chitosan (GC) is a potent immunological adjuvant capable of increasing host immune responses, including antigen presentation by activation of dendritic cells (DCs) and causing T cell proliferation. GC is also an effective surfactant for nanomaterials. By combining single-walled carbon nanotubes (SWNTs) and GC, immunologically modified carbon nanotubes (SWNT-GC) were constructed. The SWNT-GC suspension retains the enhanced light absorption properties in the near infrared (NIR) region and the ability to enter cells, which are characteristic of SWNTs. The SWNT-GC also retains the immunological properties of GC. Cellular SWNT-GC treatments increased macrophage activity, DC activation and T cell proliferation. When cellular SWNT-GC was irradiated with a laser of an appropriate wavelength, these immune activities could be enhanced. The combination of laser irradiation and SWNT-GC induced cellular toxicity in targeted tumor cells, leading to a systemic antitumor response. Immunologically modified carbon nanotubes in conjunction with phototherapy is a novel and promising method to produce a systemic immune response for the treatment of metastatic cancers.

  9. Montmorillonite Supported Titanium/Antimony Catalyst:Preparation, Characterization and Immobilization

    Institute of Scientific and Technical Information of China (English)

    CHEN Guiyong; WANG Xiaoqun; ZHAO Chuan; DU Shanyi

    2014-01-01

    Montmorillonite supported titanium (Ti-MMT) or antimony catalyst (Sb-MMT) has been a hot area of research on preparing polyethylene terephthalate/montmorillonite (PET/MMT) nanocomposites by in situ polymerization. So removal of Ti or Sb from Ti-MMT or Sb-MMT is not expected during in situ polymerization. Studies on immobilization of Ti or Sb on Ti-MMT or Sb-MMT are seldom reported. In this work, a series of montmorillonite supported catalysts of titanium (Ti-MMT) or antimony (Sb-MMT) and co-intercalated montmorillonite of titanium and antimony (Ti/Sb-MMT) were prepared by (1) the reaction of sodium bentonite suspension with intercalating solution containing titanium tetrachloride and/or antimony chloride, and (2) drying or calcinating the products at different temperature (100, 150, 240, 350 and 450℃). The physicochemical properties of these MMT supported catalysts were studied by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), inductively coupled plasma optical emission spectrometer (ICPOES), N2 adsorption/desorption isotherms, UV-visible diffuse reflectance spectroscopy(UV-vis) and transmission electron microscopy (TEM). The immobile character of Ti or Sb on MMT supported catalysts was evaluated by a two-step method in deionized water or ethylene glycol. Several results were obtained, i e, (a) during the preparation, with an increase in drying or calcinating temperature, the amount of titanium and/or antimony species remained on these MMT supported catalysts decreased, (b) the experiments about immobile character of Ti or/and Sb showed that with an increase in drying or calcinating temperature, the immobilization of Ti and/or Sb species remained on these MMT supported catalysts increased gradually, (c) Ti-MMT calcinated at 450℃had the biggest pore volume, which means Ti-MMT had the best adsorption application prospect.

  10. The influence of montmorillonite content on the kinetics of curing of epoxy nanocomposites

    Directory of Open Access Journals (Sweden)

    Jovičić Mirjana C.

    2012-01-01

    Full Text Available In this work, the attention was paid at the investigation of montmorillonite dispersion in epoxy/amine systems due to improved final properties of the nanocomposites. The influence of different montmorillonite content on the kinetics of curing of epoxy/Jeffamine D-230 systems was followed by differential scanning calorimetry (DSC. The curing of epoxy nanocomposites was performed using dynamic regime at three different heating rates: 5, 10 and 20°C/min. Three isoconversional methods were applied: two integral (Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose methods and one differential (Friedman method. The presence of montmorillonite (MMT causes the beginning of curing at lower temperatures. The shape of the DSC curves has been changed by the addition of MMT, supporting the hypothesis of a change in the reaction mechanism. For hybrids with 3 and 5 wt.% of MMT, the Eα dependence is very similar to those found for the reference system (epoxy/Jeffamine D-230 for the curing degree less than 60%. The hybrid with 10 wt.% of MMT has lower energy activation in regard to the referent system without montmorillonite. Greater differences are observed in the second part of the reaction, where it is known that the curing process is more controlled by diffusion (α>0.60. The Ea value increases at the end of the reaction (α→1, which was observed for all systems, and is more pronounced in the presence of montmorillonite. [Projekat Ministarstva nauke Republike Srbije, br. III45022

  11. Adsorption of cadmium onto Al{sub 13}-pillared acid-activated montmorillonite

    Energy Technology Data Exchange (ETDEWEB)

    Yan Liangguo [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085 (China); Shan Xiaoquan [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085 (China)], E-mail: xiaoquan@rcees.ac.cn; Wen Bei [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085 (China); Owens, Gary [Centre for Environmental Risk Assessment and Remediation, University of South Australia, Mawson Lakes Campus, Mawson Lakes, Boulevard, South Australia 5095 (Australia)

    2008-08-15

    The optimal preparation conditions for Al{sub 13}-pillared acid-activated Na{sup +}-montmorillonite (Al{sub 13}-PAAMt) were (1) an acid-activated Na{sup +}-montmorillonite (Na{sup +}-Mt) solution of pH 3.0, (2) a OH{sup -}/Al{sup 3+} molar ratio of 2.4 and (3) Al{sup 3+}/Na{sup +}-Mt ratio of 1.0 mmol g{sup -1}. The effects of OH{sup -}/Al{sup 3+} and Al{sup 3+}/Na{sup +}-Mt ratios on the adsorption of Cd{sup 2+} onto Al{sub 13}-PAAMt were studied. A comparison of the adsorption of Cd{sup 2+} onto Al{sub 13}-PAAMt, Al{sub 13}-pillared Na{sup +}-montmorillonite (Al{sub 13}-PMt) and Na{sup +}-Mt suggested that Al{sub 13}-PAAMt had higher adsorption affinity for Cd{sup 2+} than the other two adsorbents. A pseudo-second-order model described the adsorption kinetics well. Cadmium adsorption followed the Langmuir two-site equation, while desorption was hysteretic.

  12. Effect of Alumina Incorporation on the Surface Mineralization and Degradation of a Bioactive Glass (CaO-MgO-SiO2-Na2O-P2O5-CaF2-Glycerol Paste

    Directory of Open Access Journals (Sweden)

    Dilshat Tulyaganov

    2017-11-01

    Full Text Available This study investigates the dissolution behavior as well as the surface biomineralization in simulated body fluid (SBF of a paste composed of glycerol (gly and a bioactive glass in the system CaO-MgO-SiO2-Na2O-P2O5-CaF2 (BG. The synthesis of the bioactive glass in an alumina crucible has been shown to significantly affect its bioactivity due to the incorporation of aluminum (ca. 1.3–1.4 wt % into the glass network. Thus, the kinetics of the hydroxyapatite (HA mineralization on the glass prepared in the alumina crucible was found to be slower than that reported for the same glass composition prepared in a Pt crucible. It is considered that the synthesis conditions lead to the incorporation of small amount of aluminum into the BG network and thus delay the HA mineralization. Interestingly, the BG-gly paste was shown to have significantly higher bioactivity than that of the as-prepared BG. Structural analysis of the paste indicate that glycerol chemically interacts with the glass surface and strongly alter the glass network architecture, thus generating a more depolymerized network, as well as an increased amount of silanol groups at the surface of the glass. In particular, BG-gly paste features early intermediate calcite precipitation during immersion in SBF, followed by hydroxyapatite formation after ca. seven days of SBF exposure; whereas the HA mineralization seems to be suppressed in BG, probably a consequence of the incorporation of aluminum into the glass network. The results obtained within the present study reveal the positive effect of using pastes based on bioactive glasses and organic carriers (here alcohols which may be of interest not only due to their advantageous visco-elastic properties, but also due to the possibility of enhancing the glass bioactivity upon surface interactions with the organic carrier.

  13. Wheat gluten/montmorillonite biocomposites: Effect of pH on the mechanical properties and clay dispersion

    Directory of Open Access Journals (Sweden)

    E. Cortes-Trivino

    2018-07-01

    Full Text Available The addition of inorganic fillers into a bioplastic could increase its mechanical properties, which will be influenced strongly by the type of the clay dispersion. In this work, we have used montmorillonite nanoclays (MMT to prepare biocomposites by means of an extrusion process. We present herein the effect of the pH and the addition of montmorillonite nanoclays (MMT on the barrier and mechanical properties of wheat gluten based bioplastics. The pH of the samples was modified by adding aqueous solution of a strong acid or base (H2SO4 and NaOH. Tensile, dynamic mechanical thermal analysis (DMTA, water absorption and X-ray tests were carried out to study the influence of the above-mentioned variables on the physicochemical properties and rheological behaviour of bioplastics and biocomposites obtained. Tensile results showed that both Young’s modulus and tensile strength are higher at unmodified pH. However, the addition of MMT to an alkaline biopolymer matrix produced remarkable improvements in the rheological and mechanical properties because of a high exfoliation of the nanoclay noticeable in X-ray results. To summarise, extrusion process and the use of nanoclays present an excellent opportunity to develop wheat gluten bioplastics able to replace conventional products.

  14. Synthesis of Poly aniline-Montmorillonite Nano composites Using H2O2 as the Oxidant

    International Nuclear Information System (INIS)

    Binitha, N.; Binitha, N.; Suraja, V.; Zahira Yaakob; Sugunan, S.

    2011-01-01

    Poly aniline montmorillonite nano composite was prepared using H 2 O 2 as the oxidant. The catalytic environment of montmorillonite favours polymerization. Intercalation and composite formation was proven from various techniques such as XRD, FTIR, DRS and thermal analysis. XRD patterns give the dimension of the intercalated PANI, from the shift of 2θ values, which is in the nano range. FTIR showed that PANI composite formation occurred without affecting the basic clay layer structure. Thus the successful development of an alternative cheap route for poly aniline-montmorillonite nano composite was well established. (author)

  15. Use of the montmorillonite as crosslink agents for chitosan

    International Nuclear Information System (INIS)

    Barbosa, Rossemberg C.; Lima, Rosemary S. Cunha; Braga, Carla R. Costa; Fook, Marcus V. Lia; Silva, Suedina M. Lima

    2009-01-01

    The montmorillonite (the main constituent of bentonite) has been the most commonly used inorganic load in the formation of nanocomposites chitosan / layered silicate. To evaluate its effect as an agent for the reticulation of chitosan, a sodium montmorillonite, Cloisite Na + , supplied by Southern Clay Products, Texas, USA, was used. For the reticulation of chitosan dispersions of chitosan / Cloisite Na + were prepared in different proportions and the obtained films characterized by infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TG). The results indicated that the Cloisite Na + was for efficient and the reticulation of the chitosan and can be used in place of sulfuric acid, which is one of the most common reticulants for chitosan. (author)

  16. Empleo de arcillas uruguayas pilareadas para el blanqueo de aceite de maiz.

    Directory of Open Access Journals (Sweden)

    Pagano, T.

    1998-02-01

    Full Text Available In the present paper adsorptive capacity to remove carotenes from a com oil by an Uruguayan montmorillonite modified by different treatments: exchange with Na+ ions (M-Na, acid-activation (Act, exchange with Ca2+ and pillaring with Keggin ions (Pile-Act, acid-activation and pillaring (Act Pil-Ca, is studied. Bleaching action of the Uruguayan modified montmorillonites is compared with two commercial days: Tonsil Optimum (Süd-Chemie and montmorillonite of type K 10 (Aldrich. Our results demonstrate that Act and Pilc-Ca samples are so efficient bleaching clays as commercials but M-Na sample Is lower. Also, mixtures of Pilc-Ca with commercial clays, added together in one step or consecutively in two steps, are studied. These procedures do not improved the bleaching action. As conclusion, the modified clay Pilc-Ca allows to bleach a neutralized and degummed corn oil, giving an end product similar to edible commercial oils. Such effect is improved with the simultaneous action with activated clays.

    En este trabajo se estudia la capacidad de adsorción de los carotenos presentes en un aceite de maíz, de una montmorillonita uruguaya modificada por diferentes procedimientos: intercambiada con iones Na+ (M-Na, activada por ácido (Act, intercambiada con iones Ca2+ y pilareada con iones Keggin (Pilc-Ca, activada por ácidos y pilareada (Act Pilc-Ca frente a dos arcillas comerciales: Tonsil Optimum de Süd-Chemie y una Montmorillonita tipo K 10 de Aldrich. Los resultados indican que la muestra Act y la Pilc-Ca son tan eficientes como las comerciales pero que la capacidad de la muestra M-Na es considerablemente menor. También se efectuó ensayos con mezclas de Pilc-Ca con las arcillas comerciales, colocadas simultáneamente (en una sola etapa o agregadas de manera sucesiva (en dos etapas. Dichos procedimientos no mejoraron la eficiencia del blanqueo. En conclusión, la modificación Pilc-Ca permite

  17. Cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode as electrochemical sensor on microfluidic chip

    Energy Technology Data Exchange (ETDEWEB)

    Li Xinchun [School of Pharmaceutical Sciences, Sun Yat-sen University, 132 Waihuan East Road of Higher Education Mega Centre, Guangzhou 510006 (China); Chen Zuanguang, E-mail: chenzg@mail.sysu.edu.cn [School of Pharmaceutical Sciences, Sun Yat-sen University, 132 Waihuan East Road of Higher Education Mega Centre, Guangzhou 510006 (China); Zhong Yuwen, E-mail: yu0106@163.com [Center for Disease Control and Prevention of Guangdong Province, 176 Xingangxi, Guangzhou 510300 (China); Yang Fan; Pan Jianbin; Liang Yajing [School of Pharmaceutical Sciences, Sun Yat-sen University, 132 Waihuan East Road of Higher Education Mega Centre, Guangzhou 510006 (China)

    2012-01-13

    Highlights: Black-Right-Pointing-Pointer CoHCF nanoparticles modified MWCNTs/graphite electrode use for electrochemistry on electrophoresis microchip for the first time. Black-Right-Pointing-Pointer Simultaneous, rapid, and sensitive electrochemical detection of hydrazine and isoniazid in real samples. Black-Right-Pointing-Pointer An exemplary work of CME sensor assembly onto microchip for determination of analytes with environmental significance. Black-Right-Pointing-Pointer Manifestation of the applicability and flexibility of CME sensor for electroanalysis on microfluidic chip. - Abstract: Nanomaterial-based electrochemical sensor has received significant interest. In this work, cobalt hexacyanoferrate modified multi-walled carbon nanotubes/graphite composite electrode was electrochemically prepared and exploited as an amperometric detector for microchip electrophoresis. The prepared sensor displayed rapid and sensitive response towards hydrazine and isoniazid oxidation, which was attributed to synergetic electrocatalytic effect of cobalt hexacyanoferrate and multi-walled carbon nanotubes. The sensitivity enhancement with nearly two orders of magnitude was gained, compared with the bare carbon paste electrode, with the detection limit of 0.91 {mu}M (S/N = 3) for hydrazine. Acceptable repeatability of the microanalysis system was verified by consecutive eleven injections of hydrazine without chip and electrode treatments, the RSDs for peak current and migration time were 3.4% and 2.1%, respectively. Meanwhile, well-shaped electrophoretic peaks were observed, mainly due to fast electron transfer of electroactive species on the modified electrode. The developed microchip-electrochemistry setup was successfully applied to the determination of hydrazine and isoniazid in river water and pharmaceutical preparation, respectively. Several merits of the novel electrochemical sensor coupled with microfluidic platform, such as comparative stability, easy fabrication and

  18. Osteoblast cell response to surface-modified carbon nanotubes

    International Nuclear Information System (INIS)

    Zhang Faming; Weidmann, Arne; Nebe, J. Barbara; Burkel, Eberhard

    2012-01-01

    In order to investigate the interaction of cells with modified multi-walled carbon nanotubes (MWCNTs) for their potential biomedical applications, the MWCNTs were chemically modified with carboxylic acid groups (–COOH), polyvinyl alcohol (PVA) polymer and biomimetic apatite on their surfaces. Additionally, human osteoblast MG-63 cells were cultured in the presence of the surface-modified MWCNTs. The metabolic activities of osteoblastic cells, cell proliferation properties, as well as cell morphology were studied. The surface modification of MWCNTs with biomimetic apatite exhibited a significant increase in the cell viability of osteoblasts, up to 67.23%. In the proliferation phases, there were many more cells in the biomimetic apatite-modified MWCNT samples than in the MWCNTs–COOH. There were no obvious changes in cell morphology in osteoblastic MG-63 cells cultured in the presence of these chemically-modified MWCNTs. The surface modification of MWCNTs with apatite achieves an effective enhancement of their biocompatibility.

  19. An electrospun nanofiber matrix based on organo-clay for biosensors: PVA/PAMAM-Montmorillonite

    Science.gov (United States)

    Unal, Betul; Yalcinkaya, Esra Evrim; Demirkol, Dilek Odaci; Timur, Suna

    2018-06-01

    Diagnostic techniques based on biomolecules have huge a potential to be applied in the application in various areas such as food/beverage industries, diseases diagnostics, monitoring of bio-processes and environmental pollutants. Immobilization of biomolecules on a transducer is the key parameter to being able to prepare a highly stable diagnostic tests. Electrospun nanofibers are a good alternative to immobilize biomolecules. Here, electrospun nanofibers based on an organoclay were used to design the first generation amperometric enzyme biosensor. PAMAM G2 dendrimers were used to intercalate montmorillonite clay (Mt) and then the modification of Mt by PAMAM was characterized using FTIR, XRD, TGA and zeta potential measurements. After that nanofibers were prepared by electrospinning Mt and PAMAM-Mt using poly(vinyl) alcohol (PVA) as an auxiliary polymer and the formed PVA/PAMAM-Mt electrospun nanofibers were proved by SEM, TEM and AFM techniques. Finally, pyranose oxidases (PyOx) were immobilized on a glassy carbon electrode surface, which was modified using the PVA/PAMAM-Mt electrospun nanofibers. Amperometric measurements were carried out using buffer solution at -0.7 V under stirring conditions. The linear response for glucose was from 0.005 mM to 0.25 mM using PVA/Mt/PyOx and PVA/PAMAM-Mt/PyOx biosensors. The limit of detection was 0.7 μM glucose with PVA/PAMAM-Mt/PyOx biosensor. To detect glucose in real sample, measurements were carried out using soft drink cola as a substrate instead of glucose.

  20. Frictional strength of wet and dry montmorillonite

    Science.gov (United States)

    Morrow, C. A.; Moore, D. E.; Lockner, D. A.

    2017-05-01

    Montmorillonite is a common mineral in fault zones, and its low strength relative to other common gouge minerals is important in many models of fault rheology. However, the coefficient of friction, μ, varies with degree of saturation and is not well constrained in the literature due to the difficulty of establishing fully drained or fully dried states in the laboratory. We measured μ of both saturated and oven-dried montmorillonite at normal stresses up to 700 MPa. Care was taken to shear saturated samples slowly enough to avoid pore fluid overpressure. For saturated samples, μ increased from 0.10 to 0.28 with applied effective normal stress, while for dry samples μ decreased from 0.78 to 0.45. The steady state rate dependence of friction, (a - b), was positive, promoting stable sliding. The wide disparity in reported frictional strengths can be attributed to experimental procedures that promote differing degrees of partial saturation or overpressured pore fluid conditions.

  1. Studies on the flammability of polypropylene/ammonium polyphosphate and montmorillonite by using the cone calorimeter test

    Directory of Open Access Journals (Sweden)

    Hanna A.A.

    2018-03-01

    Full Text Available Fire performance of polypropylene (PP containing different percentages of ammonium polyphosphate (APP with montmorillonite (Mt or treated montmorillonite (MtT was carried out by using the cone calorimeter test (CCT. Different samples from ammonium polyphosphate and montmorillonite were mixed with 90% polypropylene. The characterization of the prepared samples indicates that there is incorporation between the components of the samples. Heat release rate (HRR, peak heat release rate (PHRR, average heat release rate (Av-HRR, and time to ignition (TTI of the samples were obtained from the cone calorimeter test. Also, the fire performance index (FPI and the fire growth rate (FIGRA were calculated. The interpretation of the curves and the parameters results from the cone calorimeter test which indicates that the addition of montmorillonite to APP increases its action as a flame retardant for PP. Moreover, the samples contain acid treatment montmorillonite showed an increase in the efficiency of ammonium polyphosphate when used. This result may be due to an increase in the SiO2 content by acid treatment.

  2. In situ synthesis and modification of calcium carbonate nanoparticles via a bobbling method

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Modified calcium carbonate (CaCO3) nanoparticles with cubic- and spindle-like configuration were synthesized in situ by the typical bobbling (gas-liquid-solid) method. The modifiers, such as sodium stearate, octadecyl dihydrogen phosphate (ODP) and oleic acid (OA), were used to obtain hydrophobic nanoparticles. The different modification effects of the modifiers were investigated by measuring the active ratio, whiteness and the contact angle. Moreover, transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetry analysis (TGA analysis) were employed to characterize the obtained products. A preliminary reaction mechanism was discussed. According to the results, the active ratio of CaCO3 modified by ODP was ca. 99.9% and the value of whiteness was 97.3% when the dosage of modifiers reached 2%. The contact angle was 122.25° for the CaCO3 modified in the presence of sodium stearate, ODP and OA. When modified CaCO3 was filled into PVC, the mechanical properties of products were improved greatly such as rupture intensity, pull intensity and fuse temperature. The compatibility and affinity between the modified CaCO3 nanoparticles and the organic matrixes were greatly improved.

  3. In situ synthesis and modification of calcium carbonate nanoparticles via a bobbling method

    Institute of Scientific and Technical Information of China (English)

    ZHAO LiNa; FENG JingDong; WANG ZiChen

    2009-01-01

    Modified calcium carbonate (CaCO3) nanoparticles with cubic- and spindle-like configuration were synthesized in situ by the typical bobbling (gas-liquid-solid) method.The modifiers,such as sodium stearate,octadecyl dihydrogen phosphate (ODP) and oleic acid (OA),were used to obtain hydrophobic nanoparticles.The different modification effects of the modifiers were investigated by measuring the active ratio,whiteness and the contact angle.Moreover,transmission electron microscopy (TEM),X-ray diffraction (XRD) and thermogravimetry analysis (TGA analysis) were employed to characterize the obtained products.A preliminary reaction mechanism was discussed.According to the results,the active ratio of CaCO3 modified by ODP was ca.99.9% and the value of whiteness was 97.3% when the dosage of modifiers reached 2%.The contact angle was 122.25° for the CaCO3 modified in the presence of sodium stearate,ODP and OA.When modified CaCO3 was filled into PVC,the mechanical properties of products were improved greatly such as rupture intensity,pull intensity and fuse temperature.The compatibility and affinity between the modified CaCO3 nanoparticles and the organic matrixes were greatly improved.

  4. Glassy carbon electrode modified with multi-walled carbon nanotubes sensor for the quantification of antihistamine drug pheniramine in solubilized systems

    Directory of Open Access Journals (Sweden)

    Rajeev Jain

    2012-02-01

    Full Text Available A sensitive electroanalytical method for quantification of pheniramine in pharmaceutical formulation has been investigated on the basis of the enhanced electrochemical response at glassy carbon electrode modified with multi-walled carbon nanotubes in the presence of sodium lauryl sulfate. The experimental results suggest that the pheniramine in anionic surfactant solution exhibits electrocatalytic effect resulting in a marked enhancement of the peak current response. Peak current response is linearly dependent on the concentration of pheniramine in the range 200–1500 μg/mL with correlation coefficient 0.9987. The limit of detection is 58.31 μg/mL. The modified electrode shows good sensitivity and repeatability. Keywords: Pheniramine, Sodium lauryl sulfate (SLS, Glassy carbon electrode modified with multi-walled carbon nanotubes (GCE-MWCNTs, Solubilized systems, Voltammetric quantification

  5. Surface Modification of Sodium Montmorillonite Nanoclay by Plasma Polymerization and Its Effect on the Properties of Polystyrene Nanocomposites

    Directory of Open Access Journals (Sweden)

    Rosa Idalia Narro-Céspedes

    2018-01-01

    Full Text Available Sodium montmorillonite nanoclay (Na+-MMT was modified by plasma polymerization with methyl methacrylate (MMA and styrene (St as monomers and was denominated as Na+-MMT/MMA and Na+-MMT/St, respectively. This plasma modified nanoclay was used as reinforcement for polystyrene (PS nanocomposites that were prepared by melt mixing. Pristine and modified Na+-MMT nanoclay were analyzed by the dispersion in various solvents, Fourier transform infrared spectroscopy (FTIR, thermogravimetric analysis (TGA, and scanning electron microscopy (SEM. The results confirmed a change in hydrophilicity of the modified Na+-MMT, as well as the presence of a polymeric material over its surface. The pristine PS/Na+-MMT and modified PS/Na+-MMT/MMA and PS/Na+-MMT/St nanocomposites were studied with X-ray diffraction (XRD, differential scanning calorimetry (DSC, and TGA, as well as mechanical properties. It was found that the PS/Na+-MMT/St nanocomposites presented better thermal properties and an improvement in Young’s modulus (YM in compared to PS/Na+-MMT/MMA nanocomposites.

  6. Improvement in tensile properties of PVC–montmorillonite ...

    Indian Academy of Sciences (India)

    mechanical properties of PVC–montmorillonite materials are also currently of huge ... Its hard form can withstand a tensile stress in the order of 46–52 MPa before .... 2θ at 25 mA and 40 kV using Cu-Kα radiation. X-ray diffraction patterns of the ...

  7. Preliminary report on longevity of montmorillonite clay under repository-related conditions

    International Nuclear Information System (INIS)

    Pusch, R.; Karnland, O.

    1990-12-01

    This report summarizes current work on developing complete models for predicting the chemical stability of montmorillonitic bentonite buffer materials in HLW repositories. The major degrading mechanism is the conversion of montmorillonite to hydrous mica ('illite'), the basis of the derivation of tentative models being offered by ongoing systematic hydrothermal tests, which indicate that such conversion takes place by dissolution, yielding very mobile silica, and aluminium that tends to stay in the clay voids. The key mechanism in the transformation to hydrous mica at temperatures below about 130 degrees C is concluded to be neoformation of the latter mineral, the controlling parameter being the access to potassium. For temperatures ranging between 130 and 200 degrees C, excess silica is released by beidellitization and this yields I/S mixed layer minerals on uptake of potassium, and precipitation of cementing silica in the form of amorphous silica and cristobalite. The rate of transformation of montmorillonite to hydrous mica is still controlled by the access to potassium, i.e. by the rate at which potassium enters the clay. 10 Aa minerals that can be mistaken for hydrous mica can be formed by cementing collapsed stacks together. The models appear to give montmorillonite transformation rates that are in agreement with lab results and geological examples but further calibration, primarily by using the results of ongoing hydrothermal tests in the Stripa study, are required to make them applicable to repository conditions. (au)

  8. Activated carbon supported CaO for conversion of palm oil to ...

    African Journals Online (AJOL)

    In this study, activated carbon supported CaO catalyst was used for the transesterification reaction of palm oil. The catalyst was prepared according to the conventional incipient witness impregnation method. Kinetic experiment was performed in a batch reactor in the presence of heterogeneous catalyst for a wide range of ...

  9. CSMA/CCA: A Modified CSMA/CA Protocol Mitigating the Fairness Problem for IEEE 802.11 DCF

    Directory of Open Access Journals (Sweden)

    Wang Xin

    2006-01-01

    Full Text Available Carrier sense multiple access with collision avoidance (CSMA/CA has been adopted by the IEEE 802.11 standards for wireless local area networks (WLANs. Using a distributed coordination function (DCF, the CSMA/CA protocol reduces collisions and improves the overall throughput. To mitigate fairness issues arising with CSMA/CA, we develop a modified version that we term CSMA with copying collision avoidance (CSMA/CCA. A station in CSMA/CCA contends for the shared wireless medium by employing a binary exponential backoff similar to CSMA/CA. Different from CSMA/CA, CSMA/CCA copies the contention window (CW size piggybacked in the MAC header of an overheard data frame within its basic service set (BSS and updates its backoff counter according to the new CW size. Simulations carried out in several WLAN configurations illustrate that CSMA/CCA improves fairness relative to CSMA/CA and offers considerable advantages for deployment in the 802.11-standard-based WLANs.

  10. Photocatalytic Activity and Characterization of Carbon-Modified Titania for Visible-Light-Active Photodegradation of Nitrogen Oxides

    Directory of Open Access Journals (Sweden)

    Chun-Hung Huang

    2012-01-01

    Full Text Available A variety of carbon-modified titania powders were prepared by impregnation method using a commercial available titania powder, Hombikat UV100, as matrix material while a range of alcohols from propanol to hexanol were used as precursors of carbon sources. Rising the carbon number of alcoholic precursor molecule, the modified titania showed increasing visible activities of NOx photodegradation. The catalyst modified with cyclohexanol exhibited the best activities of 62%, 62%, 59%, and 54% for the total NOx removal under UV, blue, green, and red light irradiation, respectively. The high activity with long wavelength irradiation suggested a good capability of photocatalysis in full visible light spectrum. Analysis of UV-visible spectrum indicated that carbon modification promoted visible light absorption and red shift in band gap. XPS spectroscopic analysis identified the existence of carbonate species (C=O, which increased with the increasing carbon number of precursor molecule. Photoluminescence spectra demonstrated that the carbonate species suppressed the recombination rate of electron-hole pair. As a result, a mechanism of visible-light-active photocatalyst was proposed according to the formation of carbonate species on carbon-modified TiO2.

  11. Fe(III/TiO2-Montmorillonite Photocatalyst in Photo-Fenton-Like Degradation of Methylene Blue

    Directory of Open Access Journals (Sweden)

    Is Fatimah

    2015-01-01

    Full Text Available A photodegradation process of methylene blue (MB in aqueous solution using Fe(III/TiO2-montmorillonite photocatalyst is presented. The photocatalyst material was prepared using Indonesian natural montmorillonite in TiO2 pillarization process followed by Fe(III ion exchange. Kinetic study on MB degradation was conducted and evaluated by three kinetic models: the pseudo-first- and second-order equations and the Elovich equation. From the results, it is concluded that the degradation under the photo-Fenton-like process utilizing Fe(III/TiO2-montmorillonite photocatalyst conformed to the Elovich kinetic model.

  12. Facile synthesis of tunable carbon modified mesoporous TiO{sub 2} for visible light photocatalytic application

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Xiao-Na; Wang, Hui-Long, E-mail: hlwang@dlut.edu.cn; Wang, Xin-Kui; Jiang, Wen-Feng

    2017-08-01

    Highlights: • Combined hydrothermal-calcination steps were used to prepare mesoporous C-TiO{sub 2}. • Polyacrylate was employed as the carbon source. • XPS revealed the interstitial carbon modifying mode through carbonate-like species. • C-TiO{sub 2} exhibited visible light activity towards dinitro butyl phenol degradation. - Abstract: In this paper, we describe a simple and novel approach for preparing tunable carbon-modified mesoporous TiO{sub 2} photocatalysts by combining the in-situ carbonization of PAA-Ti/TiO{sub 2}, hydrothermal reaction process and post-calcination treatment. The synthesized carbon-modified mesoporous TiO{sub 2} powders were of high crystallinity, large specific surface area and good visible light response. The carbon species were formed by the carbonization of polyacrylate (PAA). The presence of carbonates was subsequently confirmed by the XPS spectra, which significantly narrow down the band gap of TiO{sub 2}. The organic group in polyacrylate served as the carbon source and carbon resulted from in-situ carbonization treatment could help to inhibit the excessive growth of TiO{sub 2} grain and enlarge the pore structure of TiO{sub 2}. The amount of carbon species could be feasibly modulated by adjusting the post-calcination temperature and the surface area of the photocatalyst was enlarged further after the partial removal of carbon species. The carbon-modified mesoporous TiO{sub 2} powders exhibit excellent reproducibility and photocatalytic performance under visible light irradiation.

  13. Effect of milling time on the structure, particle size, and morphology of montmorillonite

    International Nuclear Information System (INIS)

    Abareshi, M.

    2017-01-01

    In the current research, effect of milling on the structure, particle size and morphology of montmorillonite was investigated. For this purpose, the montmorillonite was analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Then the montmorillonite was milled using high energy planetary ball mill at different milling times (1-60 hours). After that, the structure, particle size and morphology of all samples were investigated by XRD, FTIR, SEM, and transmission electron microscopy. Results showed that the ball milling causes the particle size reduction of clay and separation of the clay layers. Moreover, ball milling increases the overall structural disorder and transforms the crystalline structure into an amorphous phase. Also, the morphology of clay particle changes from layered to aggregates of almost rounded particles after 60 hours of milling.

  14. Preparation of poly (methyl methacrylate)/nanometer calcium carbonate composite by in-situ emulsion polymerization

    Institute of Scientific and Technical Information of China (English)

    史建明; 包永忠; 黄志明; 翁志学

    2004-01-01

    Methyl methacrylate (MMA) emulsion polymerization in the presence of nanometer calcium carbonate(nano-CaCO3) surface modified with γ-methacryloxypropyltrimethoxysilane (MPTMS) was carried out to prepare poly (methyl methacrylate) (PMMA)/nano-CaCO3 composite. The reaction between nano-CaCO3 and MPTMS, and the grafting of PMMA onto nano-CaCO3 were confirmed by infrared spectrum. The grafting ratio and grafting efficiency of PMMA on nano-CaCO3 modified with MPTMS were much higher than that on nano-CaCO3 modified with stearic acid. The grafting ratio of PMMA increased as the weight ratio between MMA and nano-CaCO3 increased, while the grafting efficiency of PMMA decreased. Transmission electron micrograph showed that nano-CaCO3 covered with PMMA was formed by in-situ emulsion polymerization.

  15. Possibility of ion-exchange column studies using stabilised montmorillonite-H aggregates; Possibilite d'etude d'echanges d'ions en colonne sur des agregats de Montmorillonite-H stabilises

    Energy Technology Data Exchange (ETDEWEB)

    Platzer, R; Bittel, R [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1959-07-01

    The conditions necessary for obtaining stable aggregates of montmorillonite-H, prepared without addition of organic flocculant, is discussed. These aggregates possess the same general ion-exchange properties as montmorillonite-H suspensions, about which many papers have been written. Their insolubility and their stable physical form enable them to be used in columns in exactly the same way as the usual organic ion exchangers. The examples of cation fixation and separation described in this report emphasize the similarities between the properties of this exchanger and those of organic cation-exchange resins, and open up possibilities for the extrapolation of the many investigations carried out on organic exchangers to mineral exchangers of this type. Amongst the essential differences to be remarked, we have shown that the properties of physical stability and chemical exchange remain the same at temperatures up to 300 deg. C, to a first approximation, under very intense {gamma} irradiation. (author) [French] Les conditions d'obtention d'agregats stables de montmorillonite-H prepares sans addition de floculant organique sont discutees. Ces agregats possedent les proprietes generales d'echangeurs d'ions des suspensions de montmorillonite-H, tres etudiees par de nombreux auteurs. Ils presentent une insolubilite et une forme physique stable permettant une utilisation en colonne identique a celle des echangeurs d'ions organiques usuels. Les exemples de fixation et de separation de cations qui ont ete decrits dans cet expose font ressortir les analogies entre les proprietes de cet echangeur et celles des resines organiques echangeurs de cations et permettent d'esperer une extrapolation aux echangeurs mineraux de ce type des tres nombreux travaux consacres aux echangeurs organiques. Parmi les differences essentielles a noter, nous avons mis en evidence que les proprietes de stabilite physique et d'echanges chimiques des agregats de montmorillonite subsistent a des

  16. A study of the electro-catalytic oxidation of methanol on a cobalt hydroxide modified glassy carbon electrode

    International Nuclear Information System (INIS)

    Jafarian, M.; Mahjani, M.G.; Heli, H.; Gobal, F.; Khajehsharifi, H.; Hamedi, M.H.

    2003-01-01

    Cobalt hydroxide modified glassy carbon electrodes (CHM/GC) prepared by the anodic deposition in presence of tartrate ions have been used for the electro-catalytic oxidation of methanol in alkaline solutions where the methods of cyclic voltammetery (CV), chronoamperometry (CA) and impedance spectroscopy (IS) have been employed. In CV studies, in the presence of methanol the peak current of the oxidation of cobalt hydroxide increase is followed by a decrease in the corresponding cathodic current. This suggests that the oxidation of methanol is being catalysed through the mediated electron transfer across the cobalt hydroxide layer comprising of cobalt ions of various valence states. A mechanism based on the electro-chemical generation of Co(IV) active sites and their subsequent consumptions by methanol have been discussed and the corresponding rate law under the control of charge transfer has been developed and kinetic parameters have been derived. In this context the charge transfer resistance accessible both theoretically and through the IS studies have been used as a criteria. Under the CA regimes the reaction followed a Cottrellian behaviour

  17. Radiation damage study in montmorillonites. Application to the high-level nuclear waste disposal in France

    International Nuclear Information System (INIS)

    Sorieul, St.

    2003-11-01

    significantly with the nature of the interlayer cation and less with the interlayer water content. The radiation effects in MX are expected to strongly modify the layer charge of the montmorillonite owing to the production of positive holes and oxidized iron. This is confirmed with the variations of cationic exchange capacity with He ion irradiation. Amorphization absorbed dose was measured for electronic (TEM) and ionic (ions Kr + ) radiations. It was found to vary with the nature of interlayer cations and density charge. Results will be compared with data on of radiation effects in montmorillonite. Discussion will focus on the evolution and reversibility of smectite surface properties relevant for HLNWR. (author)

  18. Potentiometric detection of silver (I) ion based on carbon paste electrode modified with diazo-thiophenol-functionalized nanoporous silica gel

    International Nuclear Information System (INIS)

    Zhang Ting; Chai Yaqin; Yuan Ruo; Guo Junxiang

    2012-01-01

    For the first time, triazene compound functionalized silica gel was incorporated into carbon paste electrode for the potentiometric detection of silver (I) ion. A novel diazo-thiophenol-functionalized silica gel (DTPSG) was synthesized, and the presence of DTPSG acted as not only a paste binder, but also a reactive material. The electrode with optimum composition, exhibited an excellent Nernstian response to Ag + ion ranging from 1.0 × 10 −6 to 1.0 × 10 −1 M with a detection limit of 9.5 × 10 −7 M and a slope of 60.4 ± 0.2 mV dec −1 over a wide pH range (4.0–9.0) with a fast response time (50 s) at 25 °C. The electrode also showed a long-time stability, high selectivity and reproducibility. The response mechanism of the proposed electrode was investigated by using AC impedance. Moreover, the electrode was successfully applied for the determination of silver ions in radiology films, and for potentiometric titration of the mixture solution of Cl − and Br − ions. - Highlights: ► Functionalized silica gels have become promising materials. ► This work is the first attempt to apply triazene functionalized silica gel. ► The Functionalized silica gels were used to detect silver. ► The response of the previously reported papers are compared with this work. ► The result indicates the proposed electrode is better than reported Ag + electrodes.

  19. Effect of sodium monofluorophosphate treatment on microstructure and frost salt scaling durability of slag cement paste

    International Nuclear Information System (INIS)

    Copuroglu, O.; Fraaij, A.L.A.; Bijen, J.M.J.M.

    2006-01-01

    Sodium-monofluorophosphate (Na-MFP) is currently in use as a surface applied corrosion inhibitor in the concrete industry. Its basic mechanism is to protect the passive layer of the reinforcement steel against disruption due to carbonation. Carbonation is known as the most detrimental environmental effect on blast furnace slag cement (BFSC) concrete with respect to frost salt scaling. In this paper the effect of Na-MFP on the microstructure and frost salt scaling resistance of carbonated BFSC paste is presented. The results of electron microscopy, mercury intrusion porosimetry (MIP) and X-ray diffraction (XRD) are discussed. It is found that the treatment modifies the microstructure and improves the resistance of carbonated BFSC paste against frost salt attack

  20. Enhancement of visible-light photocatalytic activity of silver and mesoporous carbon co-modified Bi2WO6

    International Nuclear Information System (INIS)

    Zhao, Qian; Gong, Ming; Liu, Wangping; Mao, Yulin; Le, Shukun; Ju, Shang; Long, Fei; Liu, Xiufang; Liu, Kai; Jiang, Tingshun

    2015-01-01

    Graphical abstract: - Highlights: • Silver and mesoporous carbon co-modified Bi 2 WO 6 (Ag/Bi 2 WO 6 /CMK-3) composite was prepared. • Photocatalytic activity of Bi 2 WO 6 was remarkably enhanced by co-modification of silver and mesoporous carbon. • The degradation rate of MB can reach ca. 95.1% under visible light irradiation. • The Ag/Bi 2 WO 6 /CMK-3 composite has good stability and potential application prospects. - Abstract: Ordered mesoporous carbon CMK-3 was prepared by hard template method using SBA-15 as template, sucrose as carbon source. Flower/sphere-like Bi 2 WO 6 and CMK-3/Bi 2 WO 6 photocatalysts were synthesized by hydrothermal method, and then Ag/Bi 2 WO 6 and Ag/Bi 2 WO 6 /CMK-3 composite photocatalysts were prepared via a photoreduction process. The samples were characterized by XRD, UV–vis, TEM (HR-TEM), SEM, N 2 physical adsorption and PL and their photocatalytic activities were evaluated by the photocatalytic degradation of methylene blue (MB) under visible light irradiation. The results show that both incorporating of CMK-3 and Ag loading greatly improved the photocatalytic activity of Bi 2 WO 6 , and the content of CMK-3 and silver have an impact on the photocatalytic activity of Bi 2 WO 6 . The photocatalytic activity of Ag/Bi 2 WO 6 /CMK-3 photocatalyst is superior to the activities of CMK-3/Bi 2 WO 6 and Ag/Bi 2 WO 6 under comparable conditions, and Ag/Bi 2 WO 6 /CMK-3 photocatalyst has high stability and is easy to be recycled. Also, the mechanism for the enhancement of the photocatalytic activity of CMK-3 and Ag co-modified Bi 2 WO 6 was also investigated

  1. The performance of a surface-applied corrosion inhibitor for the carbon steel in saturated Ca(OH)2 solutions

    International Nuclear Information System (INIS)

    Zheng, Haibing; Li, Weihua; Ma, Fubin; Kong, Qinglin

    2014-01-01

    In the present work, the performance of an amino alcohol based surface applied inhibitor was studied by the electrochemical techniques in saturated Ca(OH) 2 solutions. The surface morphology of the carbon steel was observed by scanning electron microscope, and the energy diffraction spectrum was also tested. Results showed that the inhibitor used in this work demonstrated obvious inhibition efficiency on the carbon steel in saturated Ca(OH) 2 solutions. The inhibition mechanism of the inhibitor lies in the quick adsorption of the active component on carbon steel surface

  2. Sensitive detection of hydroxylamine at a simple baicalin carbon nanotubes modified electrode.

    Science.gov (United States)

    Zhang, Hongfang; Zheng, Jianbin

    2012-05-15

    A baicalin multi-wall carbon nanotubes (BaMWCNT) modified glassy carbon electrode (GCE) for the sensitive determination of hydroxylamine was described. The BaMWCNT/GCE with dramatic stability was firstly fabricated with a simple adsorption method. And it showed excellent catalytic activity toward the electrooxidation of hydroxylamine. The amperometric response at the BaMWCNT/GCE modified electrode increased linearly to hydroxylamine concentrations in the range of 0.5 μM to 0.4mM with a detection limit of 0.1 μM. The modified electrode was applied to detection hydroxylamine in the tap water, and the average recovery for the standards added was 96.0%. Copyright © 2012 Elsevier B.V. All rights reserved.

  3. Carbonation-Induced Mineralogical Changes in Coal Mining Waste Blended Cement Pastes and Their Influence on Mechanical and Microporosity Properties

    Directory of Open Access Journals (Sweden)

    Moisés Frías

    2018-04-01

    Full Text Available The worldwide pursuit of new eco-efficient pozzolans is ongoing. Kaolinite-based waste is an eco-friendly source of recycled metakaolinite, a highly pozzolanic product. In this study, a blended cement paste containing 20% activated coal waste (ACW was exposed to a 100% CO2 atmosphere at 65% RH for 7 days. The variations in its phase composition and strength were studied and compared to an OPC control. Both pastes were cured for 28 days prior to the carbonation test. Reaction kinetics were assessed using XRD, SEM/EDX, TG/DTG, FT-IR, Micro-Raman spectroscopy, pore solution pH and the cumulative carbonated fraction. The blended cement carbonated 68% faster than the control. While portlandite carbonation was the main reaction in both cements, decalcification was also observed (more intensely in the 20% ACW paste in other hydraulic calcium phases (C-S-H gel, monocarboaluminate (C4AcH12, ettringite and tetracalcium aluminate (C4AH13. The end product of this reaction was calcium carbonate, mainly in the form of calcite, although traces of aragonite and amorphous carbonate were also detected. Compressive strength values rose with accelerated carbonation time and pore size reduction in both cement pastes.

  4. Nanostructured Modified Electrode for Electrocatalytic Determination of Epinephrine in the Presence of Acetaminophen

    Directory of Open Access Journals (Sweden)

    M. Mazloum-Ardakani

    2011-04-01

    Full Text Available In this paper, a nanostructured modified electrode was fabricated by incorporating of 2,2′-[1,9-nonanediylbis(nitriloethylidyne]-bis-hydroquinone (NNH as a newly synthesized modifier and TiO2 nanoparticles to the carbon paste (MTCPE and then was used for the electroanalysis of epinephrine (EP. The electrochemical studies were carried out by using cyclic voltammetry, chronoamperometry and differential pulse voltammetry (DPV techniques. It has been found that the oxidation of EP at the surface of this electrode occurs at a potential about 235 mV less positive than that of an unmodified carbon paste electrode. A dynamic range of 1.0–2000.0 μM, with a detection limit of 0.37 μM for EP, was obtained using DPV. Also, this modified electrode exhibits well separated oxidation peaks for EP and acetaminophen (AC using DPV.

  5. Localization of cesium on montmorillonite surface investigated by frequency modulation atomic force microscopy

    Science.gov (United States)

    Araki, Yuki; Satoh, Hisao; Okumura, Masahiko; Onishi, Hiroshi

    2017-11-01

    Cation exchange of clay mineral is typically analyzed without microscopic study of the clay surfaces. In order to reveal the distribution of exchangeable cations at the clay surface, we performed in situ atomic-scale observations of the surface changes in Na-rich montmorillonite due to exchange with Cs cations using frequency modulation atomic force microscopy (FM-AFM). Lines of protrusion were observed on the surface in aqueous CsCl solution. The amount of Cs of the montmorillonite particles analyzed by energy dispersive X-ray spectrometry was consistent with the ratio of the number of linear protrusions to all protrusions in the FM-AFM images. The results showed that the protrusions represent adsorbed Cs cations. The images indicated that Cs cations at the surface were immobile, and their occupancy remained constant at 10% of the cation sites at the surface with different immersion times in the CsCl solution. This suggests that the mobility and the number of Cs cations at the surface are controlled by the permanent charge of montmorillonite; however, the Cs distribution at the surface is independent of the charge distribution of the inner silicate layer. Our atomic-scale observations demonstrate that surface cations are distributed in different ways in montmorillonite and mica.

  6. Physico-mechanical properties of silanized-montmorillonite reinforced chitosan-co-poly(maleic anhydride) composites

    Science.gov (United States)

    Saputra, O. A.; Fajrin, A.; Nauqinida, M.; Suryanti, V.; Pramono, E.

    2017-07-01

    To solve the problems of dependence on petroleum as starting material in the manufacturing of plastics in Indonesia, green plastic from biopolymer like chitosan to be one of promising options and alternative to replace the conventional plastics. However, to overcome the mechanical and physical properties of chitosan, the addition of reinforcement agent was introduced. In this study, silanized-montmorillonite (sMMt) has been prepared as a reinforcement agent in the chitosan-co-poly(maleic anhydride) (referred as Cs-MAH) matrix. Silanizing of montmorillonite is one of strategy to improve the interaction between montmorillonite and chitosan, consequently, the mechanical properties, tensile strength of composites contained 6 phr of sMMt improved 56.5% to chitosan. Moreover, the presence both MAH and sMMt on the comosites also reduced swelling degree and swelling area by 20.6% and 26.7%.

  7. Adsorptive properties and thermal stability of carbon fibers modified by boron and phosphorus compounds

    International Nuclear Information System (INIS)

    Malygin, A.A.; Postnova, A.M.; Shevchenko, G.K.

    1996-01-01

    Sorptional characteristics as regards water vapors and thermal stability of carbon fibers modified by method of molecular superposition of borohydroxide groupings have been studied. Sorptional activity in the range of low and medium relative pressures of water vapors in modified samples increases several times, while thermal stability of carbon fiber increases, as well. 14 refs.; 1 fig.; 1 tab

  8. Construction of a sensitive and selective sensor for morphine using chitosan coated Fe3O4 magnetic nanoparticle as a modifier

    International Nuclear Information System (INIS)

    Dehdashtian, Sara; Gholivand, Mohammad Bagher; Shamsipur, Mojtaba; Kariminia, Samira

    2016-01-01

    A simple and sensitive sensor based on carbon paste electrode (CPE) modified by chitosan-coated magnetic nanoparticle (CMNP) was developed for the electrochemical determination of morphine (MO). The proposed sensor was characterized with scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The electrooxidation of MO was studied on modified carbon paste electrode using cyclic voltammetry, chronoamperometry and differential pulse voltammetry as diagnostic techniques. The oxidation peak potential of morphine on the CMNP/CPE appeared at 380 mV which was accompanied with smaller overpotential and increase in oxidation peak current compared to that obtained on the bare carbon paste electrode (CPE). Under optimum conditions the sensor provides two linear DPV responses in the range of 10–2000 nM and 2–720 μM for MO with a detection limit of 3 nM. The proposed sensor was successfully applied for monitoring of MO in serum and urine samples and satisfactory results were obtained. - Highlights: • A sensitive and selective voltammetric sensor for MO by using a carbon paste electrode modified with CMNP was introduced. • CMNP as a new modifier facilitates the charge transfer of MO oxidation process. • The proposed sensor was used successfully for MO determination in biological fluids such as serum and urine samples. • This sensor is fabricated easily and has good stability and high sensitivity.

  9. Water structure and aqueous uranyl(VI) adsorption equilibria onto external surfaces of beidellite, montmorillonite, and pyrophyllite: results from molecular simulations.

    Science.gov (United States)

    Greathouse, Jeffery A; Cygan, Randall T

    2006-06-15

    Molecular dynamics simulations were performed to provide a systematic study of aqueous uranyl adsorption onto the external surface of 2:1 dioctahedral clays. Our understanding of this key process is critical in predicting the fate of radioactive contaminants in natural groundwaters. These simulations provide atomistic detail to help explain experimental trends in uranyl adsorption onto natural media containing smectite clays. Aqueous uranyl concentrations ranged from 0.027 to 0.162 M. Sodium ions and carbonate ions (0.027-0.243 M) were also present in the aqueous regions to more faithfully model a stream of uranyl-containing groundwater contacting a mineral system comprised of Na-smectite. No adsorption occurred near the pyrophyllite surface, and there was little difference in uranyl adsorption onto the beidellite and montmorillonite, despite the difference in location of clay layer charge between the two. At low uranyl concentration, the pentaaquouranyl complex dominates in solution and readily adsorbs to the clay basal plane. At higher uranyl (and carbonate) concentrations, the mono(carbonato) complex forms in solution, and uranyl adsorption decreases. Sodium adsorption onto beidellite occurred both as inner- and outer-sphere surface complexes, again with little effect on uranyl adsorption. Uranyl surface complexes consisted primarily of the pentaaquo cation (85%) and to a lesser extent the mono(carbonato) species (15%). Speciation diagrams of the aqueous region indicate that the mono(carbonato)uranyl complex is abundant at high ionic strength. Oligomeric uranyl complexes are observed at high ionic strength, particularly near the pyrophyllite and montmorillonite surfaces. Atomic density profiles of water oxygen and hydrogen atoms are nearly identical near the beidellite and montmorillonite surfaces. Water structure therefore appears to be governed by the presence of adsorbed ions and not by the location of layer charge associated with the substrate. The water

  10. Validating carbonation parameters of alkaline solid wastes via integrated thermal analyses: Principles and applications.

    Science.gov (United States)

    Pan, Shu-Yuan; Chang, E-E; Kim, Hyunook; Chen, Yi-Hung; Chiang, Pen-Chi

    2016-04-15

    Accelerated carbonation of alkaline solid wastes is an attractive method for CO2 capture and utilization. However, the evaluation criteria of CaCO3 content in solid wastes and the way to interpret thermal analysis profiles were found to be quite different among the literature. In this investigation, an integrated thermal analyses for determining carbonation parameters in basic oxygen furnace slag (BOFS) were proposed based on thermogravimetric (TG), derivative thermogravimetric (DTG), and differential scanning calorimetry (DSC) analyses. A modified method of TG-DTG interpretation was proposed by considering the consecutive weight loss of sample with 200-900°C because the decomposition of various hydrated compounds caused variances in estimates by using conventional methods of TG interpretation. Different quantities of reference CaCO3 standards, carbonated BOFS samples and synthetic CaCO3/BOFS mixtures were prepared for evaluating the data quality of the modified TG-DTG interpretation, in terms of precision and accuracy. The quantitative results of the modified TG-DTG method were also validated by DSC analysis. In addition, to confirm the TG-DTG results, the evolved gas analysis was performed by mass spectrometer and Fourier transform infrared spectroscopy for detection of the gaseous compounds released during heating. Furthermore, the decomposition kinetics and thermodynamics of CaCO3 in BOFS was evaluated using Arrhenius equation and Kissinger equation. The proposed integrated thermal analyses for determining CaCO3 content in alkaline wastes was precise and accurate, thereby enabling to effectively assess the CO2 capture capacity of alkaline wastes for mineral carbonation. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Effect of dry density and salinity on Cl- diffusion of compacted Na-montmorillonite

    International Nuclear Information System (INIS)

    Goto, T.; Gorai, M.; Kozaki, T.; Sato, S.

    2010-01-01

    Document available in extended abstract form only. Compacted bentonite is candidate buffer material in geological disposal of high-level radioactive waste (HLW). One of the expected functions of the buffer is to retard the migration of radionuclides from waste form to biosphere. Due to low hydraulic conductivity of the compacted bentonite, diffusion is considered to be predominant process in radionuclide migrations. Therefore, it is important for safety assessment of the geological disposal to clarify the diffusion behavior of radionuclides in montmorillonite, which is a major clay mineral of bentonite. However, detail diffusion mechanism has not been fully understood especially for the compacted bentonite saturated with groundwater having relatively high salt concentration. In this study, apparent diffusion coefficient (D a [m 2 s -1 ]) of Cl- ions was determined by one-dimensional, non-steady diffusion method for Na-montmorillonite saturated with NaCl solutions with different concentrations. Activation energy for Cl - diffusion (E a [kJ mol -1 ]) was also obtained from the temperature dependence of Da at each NaCl concentration. Based on these experimental results together with the basal spacing of the montmorillonite determined by XRD measurements, the diffusion mechanism of Cl - ions was discussed. The montmorillonite used in this study was Kunipia-F, a commercial product of Kunimine Industries Co. Ltd., Japan. The montmorillonite sample was homo-ionized into Na-type before use. The Na-montmorillonite was compacted into an acrylic resin cell (20 mm in diameter, 20 mm in height for diffusion experiment or 10 mm in height for XRD measurement) and fully saturated with NaCl solutions of concentration from 0 to 0.5 M. The dry densities of the Na-montmorillonite were 1.0 and 1.3 Mg m -3 for diffusion experiments, and from 0.7 to 1.4 Mg m -3 for the XRD measurements. The apparent diffusion coefficients of 36 Cl - ions in the solution-saturated, compacted

  12. Adsorption of Benzene by “Green” functionalization of Montmorillonite

    Directory of Open Access Journals (Sweden)

    Anjum Hirra

    2018-01-01

    Full Text Available The capacity of organically modified Montmorillonite (MMT clay to adsorb nonpolar organic compound (benzene in an aqueous solution, was investigated under the batch process. MMT was pretreated (centrifuged and then functionalized with green intercalating agent i.e. 1-hexyl-3-methyl imadazolium chloride [HMim][Cl]. The characterization through Fourir Transoform Infrared Spectroscopy (FTIR, Differential Scanning Calorimeter (DSC and Field Emission Scanning Electron Microscope (FE-SEM confirmed the presence of the oxygen containing functional groups, changes in melting point and variation in the morphological properties. The governing parameters for the sorption of benzene such as the effect of contact time, pH, adsorbent dose and rotation were studied. The kinetic data conformed to pseuodo 2nd order kinetic model and the isotherm experimental data were a better fit to Langmuir model with maximum adsorption capacity of 588.23mg/g under experimental conditions. Overall, MMT intercalated with 1-hexyl-3-methyl imadazolium chloride is a promising environmental friendly adsorbent for the abatement of benzene in an aqueous solution.

  13. Modifying the electronic and optical properties of carbon nanotubes

    Science.gov (United States)

    Kinder, Jesse M.

    The intrinsic electronic and optical properties of carbon nanotubes make them promising candidates for circuit elements and LEDs in nanoscale devices. However, applied fields and interactions with the environment can modify these intrinsic properties. This dissertation is a theoretical study of perturbations to an ideal carbon nanotube. It illustrates how transport and optical properties of carbon nanotubes can be adversely affected or intentionally modified by the local environment. The dissertation is divided into three parts. Part I analyzes the effect of a transverse electric field on the single-electron energy spectrum of semiconducting carbon nanotubes. Part II analyzes the effect of the local environment on selection rules and decay pathways relevant to dark excitons. Part III is a series of 26 appendices. Two different models for a transverse electric field are introduced in Part I. The first is a uniform field perpendicular to the nanotube axis. This model suggests the field has little effect on the band gap until it exceeds a critical value that can be tuned with strain or a magnetic field. The second model is a transverse field localized to a small region along the nanotube axis. The field creates a pair of exponentially localized bound states but has no effect on the band gap for particle transport. Part II explores the physics of dark excitons in carbon nanotubes. Two model calculations illustrate the effect of the local environment on allowed optical transitions and nonradiative recombination pathways. The first model illustrates the role of inversion symmetry in the optical spectrum. Broken inversion symmetry may explain low-lying peaks in the exciton spectrum of boron nitride nanotubes and localized photoemission around impurities and interfaces in carbon nanotubes. The second model in Part II suggests that free charge carriers can mediate an efficient nonradiative decay process for dark excitons in carbon nanotubes. The appendices in Part III

  14. Highly anisotropic conductivity of tablets pressed from polyaniline-montmorillonite nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Tokarský, Jonáš, E-mail: jonas.tokarsky@vsb.cz [Nanotechnology centre, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava—Poruba (Czech Republic); IT4Innovations Centre of Excellence, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava—Poruba (Czech Republic); Kulhánková, Lenka [Faculty of Metallurgy and Materials Engineering, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava—Poruba (Czech Republic); Neuwirthová, Lucie; Mamulová Kutláková, Kateřina [Nanotechnology centre, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava—Poruba (Czech Republic); Vallová, Silvie [Faculty of Metallurgy and Materials Engineering, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava—Poruba (Czech Republic); Stýskala, Vítězslav [Faculty of Electrical Engineering and Computer Science, VŠB-TU Ostrava, 17. listopadu 15/2172, 708 33 Ostrava—Poruba (Czech Republic); Čapková, Pavla [Faculty of Science, University of J.E. Purkyně, České mládeže 8, 400 96 Ústí nad Labem (Czech Republic)

    2016-03-15

    Highlights: • Montmorillonite (MMT) can be intercalated with polyaniline (PANI) chains. • Tablets pressed from PANI/MMT exhibit high anisotropy in electrical conductivity. • Pressure 28MPa is sufficient to reach the anisotropy. • Tablets pressed from pure PANI also exhibit anisotropy in electrical conductivity. - Abstract: Polyaniline-montmorillonite nanocomposite was prepared from anilinium sulfate (precursor) and ammonium peroxodisulfate (oxidizing agent) using simple one-step method. The resulting nanocomposite obtained in powder form has been pressed into tablets using various compression pressures (28–400 MPa). Electrical conductivities of tablets in two perpendicular directions, i.e. direction parallel with the main surface of tablet (σ=) and in orthogonal direction (σ⊥), and corresponding anisotropy factors (i.e., the ratio σ=/σ⊥) have been studied in dependence on compression pressure used during the preparation. Polyaniline-montmorillonite nanocomposite was characterized using X-ray diffraction analysis, raman spectroscopy, transmission electron microscopy, thermogravimetric analysis and molecular modeling which led to the understanding of the internal structure. Measurement of hardness performed on pressed tablets has been also involved. Taking into account the highest value of anisotropy factor reached (σ=/σ⊥ = 490), present study shows a chance to design conductors with nearly two-dimensional conductivity.

  15. Highly anisotropic conductivity of tablets pressed from polyaniline-montmorillonite nanocomposite

    International Nuclear Information System (INIS)

    Tokarský, Jonáš; Kulhánková, Lenka; Neuwirthová, Lucie; Mamulová Kutláková, Kateřina; Vallová, Silvie; Stýskala, Vítězslav; Čapková, Pavla

    2016-01-01

    Highlights: • Montmorillonite (MMT) can be intercalated with polyaniline (PANI) chains. • Tablets pressed from PANI/MMT exhibit high anisotropy in electrical conductivity. • Pressure 28MPa is sufficient to reach the anisotropy. • Tablets pressed from pure PANI also exhibit anisotropy in electrical conductivity. - Abstract: Polyaniline-montmorillonite nanocomposite was prepared from anilinium sulfate (precursor) and ammonium peroxodisulfate (oxidizing agent) using simple one-step method. The resulting nanocomposite obtained in powder form has been pressed into tablets using various compression pressures (28–400 MPa). Electrical conductivities of tablets in two perpendicular directions, i.e. direction parallel with the main surface of tablet (σ=) and in orthogonal direction (σ⊥), and corresponding anisotropy factors (i.e., the ratio σ=/σ⊥) have been studied in dependence on compression pressure used during the preparation. Polyaniline-montmorillonite nanocomposite was characterized using X-ray diffraction analysis, raman spectroscopy, transmission electron microscopy, thermogravimetric analysis and molecular modeling which led to the understanding of the internal structure. Measurement of hardness performed on pressed tablets has been also involved. Taking into account the highest value of anisotropy factor reached (σ=/σ⊥ = 490), present study shows a chance to design conductors with nearly two-dimensional conductivity.

  16. Ability of Cu2+-montmorillonite to accept an toxic pollutants

    International Nuclear Information System (INIS)

    Janikova, V.; Jona, E.; Janik, R.; Pavlik, V.

    2015-01-01

    It is global problem that toxic pollutants are in the permanent contact to people through soil and water. Nowadays, it is important to eliminate these pollutants for future generations and to keep environment in the health condition. In relation to this article, aromatic organic compounds like benzene, phenol and aniline were chosen. These are used in various branches of industry, mainly in rubber industry or for production of dyes and in addition, phenol is commonly used in cosmetics or in food industry. Montmorillonite is clay mineral consisting of 2:1 sheets (tetrahedral:octahedral) and interlayer space where exchangeable cations and water molecules are present. Due to its structure, montmorillonite is able to accept some compounds or pollutants. This is the reason why it is mainly used as the covering material of radioactive waste in order to remove toxic pollutants. For investigation of toxic pollutants removing, XRD powder diffraction, infrared spectroscopy and thermal analysis were used. Our results show that Cu 2+ -montmorillonite is able to accept toxic benzene ring-based pollutants into interlayer. This mentioned ability can be proven on the basis of the investigation results relating to difference of interlayer distance, typical frequencies of -OH group or -NH 2 group, while these results were supplemented by thermal properties. (authors)

  17. THE SYNTHESIS OF Cr2O3-PILLARED MONTMORILLONITE (CrPM AND ITS USAGE FOR HOST MATERIAL OF p-NITROANILINE

    Directory of Open Access Journals (Sweden)

    Karna Wijaya

    2010-06-01

    Full Text Available The synthesis of Cr2O3-pillared montmorillonite (CrPM and its usage for host material of p-nitroaniline have been conducted. The Cr2O3-pillared montmorillonite clays was prepared by a direct ion exchange method. First, the polyhydroxychromium as a pillaring spesies was intercalated into the interlayer region of the montmorillonite clays (purified clay in the monocation form, result in a montmorillonite-polyoxychromium intercalation compound. The precursors/pillaring spesies was not stable, hence it must be stabilized by calcination in order to transform the polyoxychromium via dehydration and dehydroxylation processes into Cr2O3. This oxide constituts the so-called pillar that prop the clay layers apart to a relatively large distance. The Cr2O3-pillared clays as a host material was added into ethanol solution saturated with p-nitroaniline, and mixture was stirred for 24 h at room temperature. The Na-montmorillonite, Cr2O3-pillared clay and p-nitroaniline-Cr2O3-pillared clay (pNA-CrPM were characterized by X-Ray Diffraction (XRD, Gas Sorption Analysis, Infrared Spectroscopy (FTIR and Activated Neutron Analysis (ANA methods. The result of research showed that basal spacing (d001 of Cr2O3-pillared montmorillonite (CrPM was 18,55 Å, meanwhile the basal spacing of the hydrated Na-montmorillonite was 14,43 Å. The specific surface area of the Cr2O3-pillared montmorillonite was 174,308 m2/g, whereas p-nitroaniline-Cr2O3-pillared clay (pNA-CrPM was 133,331641 m2/g. This fact indicated that p-nitroaniline has been included into the pore of the Cr2O3-pillared clay.   Keyword: montmorillonite, pillared-clay, ion exchange, intercalate.

  18. Functional interface of polymer modified graphite anode

    Science.gov (United States)

    Komaba, S.; Ozeki, T.; Okushi, K.

    Graphite electrodes were modified by polyacrylic acid (PAA), polymethacrylic acid (PMA), and polyvinyl alcohol (PVA). Their electrochemical properties were examined in 1 mol dm -3 LiClO 4 ethylene carbonate:dimethyl carbonate (EC:DMC) and propylene carbonate (PC) solutions as an anode of lithium ion batteries. Generally, lithium ions hardly intercalate into graphite in the PC electrolyte due to a decomposition of the PC electrolyte at ca. 0.8 V vs. Li/Li +, and it results in the exfoliation of the graphene layers. However, the modified graphite electrodes with PAA, PMA, and PVA demonstrated the stable charge-discharge performance due to the reversible lithium intercalation not only in the EC:DMC but also in the PC electrolytes since the electrolyte decomposition and co-intercalation of solvent were successfully suppressed by the polymer modification. It is thought that these improvements were attributed to the interfacial function of the polymer layer on the graphite which interacted with the solvated lithium ions at the electrode interface.

  19. A curcumin activated carboxymethyl cellulose-montmorillonite clay nanocomposite having enhanced curcumin release in aqueous media.

    Science.gov (United States)

    Madusanka, Nadeesh; de Silva, K M Nalin; Amaratunga, Gehan

    2015-12-10

    A novel curcumin activated carboxymethylcellulose-montmorillonite nanocomposite is reported. A superabsorbent biopolymer; carboxymethyl cellulose (CMC) was used as an emulsifier for curcumin which is a turmeric derived water insoluble polyphenolic compound with antibacterial/anti-cancer properties. Montmorillonite (MMT) nanoclay was incorporated in the formulation as a matrix material which also plays a role in release kinetics. It was observed that water solubility of curcumin in the nanocomposite has significantly increased (60% release within 2h and 30 min in distilled water at pH 5.4) compared to pure curcumin. The prepared curcumin activated carboxymethylcellulose-montmorillonite nanocomposite is suitable as a curcumin carrier having enhanced release and structural properties. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Potentiometric detection of silver (I) ion based on carbon paste electrode modified with diazo-thiophenol-functionalized nanoporous silica gel

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Ting; Chai Yaqin, E-mail: yqchai@swu.edu.cn; Yuan Ruo; Guo Junxiang

    2012-07-01

    For the first time, triazene compound functionalized silica gel was incorporated into carbon paste electrode for the potentiometric detection of silver (I) ion. A novel diazo-thiophenol-functionalized silica gel (DTPSG) was synthesized, and the presence of DTPSG acted as not only a paste binder, but also a reactive material. The electrode with optimum composition, exhibited an excellent Nernstian response to Ag{sup +} ion ranging from 1.0 Multiplication-Sign 10{sup -6} to 1.0 Multiplication-Sign 10{sup -1} M with a detection limit of 9.5 Multiplication-Sign 10{sup -7} M and a slope of 60.4 {+-} 0.2 mV dec{sup -1} over a wide pH range (4.0-9.0) with a fast response time (50 s) at 25 Degree-Sign C. The electrode also showed a long-time stability, high selectivity and reproducibility. The response mechanism of the proposed electrode was investigated by using AC impedance. Moreover, the electrode was successfully applied for the determination of silver ions in radiology films, and for potentiometric titration of the mixture solution of Cl{sup -} and Br{sup -} ions. - Highlights: Black-Right-Pointing-Pointer Functionalized silica gels have become promising materials. Black-Right-Pointing-Pointer This work is the first attempt to apply triazene functionalized silica gel. Black-Right-Pointing-Pointer The Functionalized silica gels were used to detect silver. Black-Right-Pointing-Pointer The response of the previously reported papers are compared with this work. Black-Right-Pointing-Pointer The result indicates the proposed electrode is better than reported Ag{sup +} electrodes.

  1. Synthesis and Characterization of CdS/TiO2-Montmorillonite Nanocomposite with Enhanced Visible-Light Absorption

    Directory of Open Access Journals (Sweden)

    Feng-shan Zhou

    2014-01-01

    Full Text Available Sodium montmorillonite (MMT was chosen as the carrier; a serial of CdS/TiO2-MMT nanocomposites with enhanced visible-light absorption ability was prepared by hydrothermal synthesis method combination with semiconductor compound modification method. The samples are characterized by X-ray diffraction (XRD, X-ray photoelectron spectroscopy (XPS, and ultraviolet visible (UV-Vis spectroscopy; the results showed that TiO2 and CdS nanoparticles were loaded on the surface of montmorillonite uniformly. N2 adsorption-desorption experiment showed that the specific surface area of TiO2/montmorillonite nanocomposite made by this method can reach 200 m2/g and pore-size distribution was from 4 to 6 nm; UV-Vis showed that the recombination of CdS and TiO2 enhanced visible-light absorption ability of samples of TiO2/montmorillonite and visible-light absorption ability increase with the increased of the adsorption of CdS.

  2. Driving factors behind carbon dioxide emissions in China: A modified production-theoretical decomposition analysis

    International Nuclear Information System (INIS)

    Wang, Qunwei; Chiu, Yung-Ho; Chiu, Ching-Ren

    2015-01-01

    Research on the driving factors behind carbon dioxide emission changes in China can inform better carbon emission reduction policies and help develop a low-carbon economy. As one of important methods, production-theoretical decomposition analysis (PDA) has been widely used to understand these driving factors. To avoid the infeasibility issue in solving the linear programming, this study proposed a modified PDA approach to decompose carbon dioxide emission changes into seven drivers. Using 2005–2010 data, the study found that economic development was the largest factor of increasing carbon dioxide emissions. The second factor was energy structure (reflecting potential carbon), and the third factor was low energy efficiency. Technological advances, energy intensity reductions, and carbon dioxide emission efficiency improvements were the negative driving factors reducing carbon dioxide emission growth rates. Carbon dioxide emissions and driving factors varied significantly across east, central and west China. - Highlights: • A modified PDA used to decompose carbon dioxide emission changes into seven drivers. • Two models were proposed to ameliorate the infeasible occasions. • Economic development was the largest factor of increasing CO_2 emissions in China.

  3. Calculating carbon mass balance from unsaturated soil columns treated with CaSO₄₋minerals: test of soil carbon sequestration.

    Science.gov (United States)

    Han, Young-Soo; Tokunaga, Tetsu K

    2014-12-01

    Renewed interest in managing C balance in soils is motivated by increasing atmospheric concentrations of CO2 and consequent climate change. Here, experiments were conducted in soil columns to determine C mass balances with and without addition of CaSO4-minerals (anhydrite and gypsum), which were hypothesized to promote soil organic carbon (SOC) retention and soil inorganic carbon (SIC) precipitation as calcite under slightly alkaline conditions. Changes in C contents in three phases (gas, liquid and solid) were measured in unsaturated soil columns tested for one year and comprehensive C mass balances were determined. The tested soil columns had no C inputs, and only C utilization by microbial activity and C transformations were assumed in the C chemistry. The measurements showed that changes in C inventories occurred through two processes, SOC loss and SIC gain. However, the measured SOC losses in the treated columns were lower than their corresponding control columns, indicating that the amendments promoted SOC retention. The SOC losses resulted mostly from microbial respiration and loss of CO2 to the atmosphere rather than from chemical leaching. Microbial oxidation of SOC appears to have been suppressed by increased Ca(2+) and SO4(2)(-) from dissolution of CaSO4 minerals. For the conditions tested, SIC accumulation per m(2) soil area under CaSO4-treatment ranged from 130 to 260 g C m(-1) infiltrated water (20-120 g C m(-1) infiltrated water as net C benefit). These results demonstrate the potential for increasing C sequestration in slightly alkaline soils via CaSO4-treatment. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. The catalytic activity of Ag{sub 2}S-montmorillonites as peroxidase mimetic toward colorimetric detection of H{sub 2}O{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Qingyun, E-mail: qyliu@sdust.edu.cn [School of Chemistry and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266510 (China); Jiang, Yanling; Zhang, Leyou; Zhou, Xinpei [School of Chemistry and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266510 (China); Lv, Xintian [School of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng 252000 (China); Ding, Yanyuan; Sun, Lifang; Chen, Pengpeng [School of Chemistry and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266510 (China); Yin, Hailiang [Academy of Science & Technology, China University of Petroleum, Dongying 257061 (China)

    2016-08-01

    Nanocomposites based on silver sulfide (Ag{sub 2}S) and Ca-montmorillonite (Ca{sup 2+}-MMT) were synthesized by a simple hydrothermal method. The nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectra (FTIR). The as-prepared Ag{sub 2}S-MMT nanocomposites were firstly demonstrated to possess intrinsic peroxidase-like activity and could rapidly catalytically oxidize the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H{sub 2}O{sub 2} to produce a blue product which can be seen by the naked eye in only one minute. The experimental results revealed that the Ag{sub 2}S-MMT nanocomposites exhibit higher thermal durance. Based on the TMB–H{sub 2}O{sub 2} catalyzed color reaction, the Ag{sub 2}S-MMT nanocomposites were exploited as a new type of biosensor for detection and estimation of H{sub 2}O{sub 2} through a simple, cheap and selective colorimetric method. - Highlights: • Ag{sub 2}S – montmorillonites (MMT) was synthesized by a facile one step method. • The as-prepared Ag{sub 2}S-MMT nanocomposites firstly demonstrate to possess intrinsic peroxidase-like activity. • Ag{sub 2}S-MMT nanocomposites showed highly catalytic activity. • Ag{sub 2}S-MMT could rapidly catalytically oxidize substrates TMB in the presence of H{sub 2}O{sub 2} in 1 min. • The catalytic mechanism is from the generation of hydroxyl radical (·OH) decomposed from H{sub 2}O{sub 2}.

  5. Glassy carbon electrodes modified with multiwalled carbon nanotubes for the determination of ascorbic acid by square-wave voltammetry

    Directory of Open Access Journals (Sweden)

    Sushil Kumar

    2012-05-01

    Full Text Available Multiwalled carbon nanotubes were used to modify the surface of a glassy carbon electrode to enhance its electroactivity. Nafion served to immobilise the carbon nanotubes on the electrode surface. The modified electrode was used to develop an analytical method for the analysis of ascorbic acid (AA by square-wave voltammetry (SWV. The oxidation of ascorbic acid at the modified glassy carbon electrode showed a peak potential at 315 mV, about 80 mV lower than that observed at the bare (unmodified electrode. The peak current was about threefold higher than the response at the bare electrode. Replicate measurements of peak currents showed good precision (3% rsd. Peak currents increased with increasing ascorbic acid concentration (dynamic range = 0.0047–5.0 mmol/L and displayed good linearity (R2 = 0.994. The limit of detection was 1.4 μmol/L AA, while the limit of quantitation was 4.7 μmol/L AA. The modified electrode was applied to the determination of the amount of ascorbic acid in four brands of commercial orange-juice products. The measured content agreed well (96–104% with the product label claim for all brands tested. Recovery tests on spiked samples of orange juice showed good recovery (99–104%. The reliability of the SWV method was validated by conducting parallel experiments based on high-performance liquid chromatography (HPLC with absorbance detection. The observed mean AA contents of the commercial orange juice samples obtained by the two methods were compared statistically and were found to have no significant difference (P = 0.05.

  6. Tartrazine modified activated carbon for the removal of Pb(II), Cd(II) and Cr(III).

    Science.gov (United States)

    Monser, Lotfi; Adhoum, Nafaâ

    2009-01-15

    A two in one attempt for the removal of tartrazine and metal ions on activated carbon has been developed. The method was based on the modification of activated carbon with tartrazine then its application for the removal of Pb(II), Cd(II) and Cr(III) ions at different pH values. Tartrazine adsorption data were modelled using both Langmuir and Freundlich classical adsorption isotherms. The adsorption capacities qm were 121.3, 67 and 56.7mgg(-1) at initial pH values of 1.0, 6.0 and 10, respectively. The adsorption of tartrazine onto activated carbon followed second-order kinetic model. The equilibrium time was found to be 240min at pH 1.0 and 120min at pH 10 for 500mgL(-1) tartrazine concentration. A maximum removal of 85% was obtained after 1h of contact time. The presence of tartrazine as modifier enhances attractive electrostatic interactions between metal ions and carbon surface. The adsorption capacity for Pb(II), Cd(II) and Cr(III) ions has been improved with respect to non-modified carbon reaching a maximum of 140%. The adsorption capacity was found to be a pH dependent for both modified and non-modified carbon with a greater adsorption at higher pH values except for Cr(III). The enhancement percent of Pb(II), Cd(II) and Cr(III) at different pH values was varied from 28% to 140% with respect to non-modified carbon. The amount of metal ions adsorbed using static regime was 11-40% higher than that with dynamic mode. The difference between adsorption capacities could be attributed to the applied flow rate.

  7. Screen-printed carbon electrode modified on its surface with amorphous carbon nitride thin film: Electrochemical and morphological study

    Energy Technology Data Exchange (ETDEWEB)

    Ghamouss, F. [Universite de Nantes, UMR 6006-CNRS, FR-2465-CNRS, Laboratoire d' Analyse isotopique et Electrochimique de Metabolismes (LAIEM) (France); Tessier, P.-Y. [Universite de Nantes, UMR CNRS 6502, Institut des Materiaux Jean Rouxel - IMN Faculte des Sciences and des Techniques de Nantes, 2 rue de la Houssiniere, 44322 Nantes Cedex 3 (France); Djouadi, A. [Universite de Nantes, UMR CNRS 6502, Institut des Materiaux Jean Rouxel - IMN Faculte des Sciences and des Techniques de Nantes, 2 rue de la Houssiniere, 44322 Nantes Cedex 3 (France); Besland, M.-P. [Universite de Nantes, UMR CNRS 6502, Institut des Materiaux Jean Rouxel - IMN Faculte des Sciences and des Techniques de Nantes, 2 rue de la Houssiniere, 44322 Nantes Cedex 3 (France); Boujtita, M. [Universite de Nantes, UMR 6006-CNRS, FR-2465-CNRS, Laboratoire d' Analyse isotopique et Electrochimique de Metabolismes (LAIEM) (France)]. E-mail: mohammed.boujtita@univ-nantes.fr

    2007-04-20

    The surface of a screen-printed carbon electrode (SPCE) was modified by using amorphous carbon nitride (a-CN {sub x}) thin film deposited by reactive magnetron sputtering. Scanning electron microscopy and photoelectron spectroscopy measurements were used to characterise respectively the morphology and the chemical structure of the a-CN {sub x} modified electrodes. The incorporation of nitrogen in the amorphous carbon network was demonstrated by X ray photoelectron spectroscopy. The a-CN {sub x} layers were deposited on both carbon screen-printed electrode (SPCE) and silicon (Si) substrates. A comparative study showed that the nature of substrate, i.e. SPCE and Si, has a significant effect on both the surface morphology of deposited a-CN {sub x} film and their electrochemical properties. The improvement of the electrochemical reactivity of SPCE after a-CN {sub x} film deposition was highlighted both by comparing the shapes of voltammograms and calculating the apparent heterogeneous electron transfer rate constant.

  8. Development of plasticised nano-biocomposites of poly(hydroxybutyrate-co-hydroxyvalerate)/montmorillonite organically modified (PHBV/OMMT); Desenvolvimento de nanobiocompositos plastificados de poli(hidroxibutirato-co-hidroxivalerato)/montimorilonita organomodificada (PHBV/OMMT)

    Energy Technology Data Exchange (ETDEWEB)

    Correa, M.C., E-mail: nascente@ufscar.b [Universidade Federal de Sao Carlos (PPGCEM/UFSCAR), SP (Brazil). Pos-graduacao em Ciencia e Engenharia de Materiais; Pollet, E.; Averous, L. [Ecole Europeenne de Chimie, Polymeres et Materiaux (LIPHT/ECPM), Strasbourg (France). Lab. d' Ingenierie des Polymeres pour les Hautes Technologies; Agnell, J.A.M.; Nascente, P.A.P. [Universidade Federal de Sao Carlos (DEMA/UFSCAR), SP (Brazil). Dept. de Engenharia de Materiais

    2010-07-01

    Several studies have aimed to improve the properties of biopolymers by the incorporation of nano-sized fillers, such as organo-modified montmorillonite (OMMT), to form nano-biocomposites. The objective of this work is to investigate the influence of acetyl tributyl citrate (ATBC) plasticizer with PHBV/OMMT nano-biocomposites aiming at improving their behavior. The materials PHBV, OMMT (C30B), and ATBC were provided by PHB Industrial S/A (Brazil), Southern Clay Products (USA), and Scandiflex S/A (Brazil), respectively. In this study the processing parameters and the formulations were controlled, pursuing materials with good mechanical and barrier properties with high biodegradability and with greater ease of processing. The analysis of the results obtained by TGA, GPC, WAXS, DSC, mechanical properties, and biodegradability lead to the conclusion that the addition of plasticizer in nanobiocomposites improved processability and did not influence the state of nano-sized load dispersion. It can be concluded that the addition of plasticizer is a good alternative to the processability of nanocomposites of PHAs. (author)

  9. Electrocatalytic Determination of Isoniazid by a Glassy Carbon Electrode Modified with Poly (Eriochrome Black T)

    OpenAIRE

    Karim Asadpour-Zeynali; Venus Baghalabadi

    2017-01-01

    In this work poly eriochrome black T (EBT) was electrochemically synthesized on the glassy carbon electrode as electrode modifier. On the modified electrode, voltammetric behavior of isoniazid (INH) was investigated. The poly (EBT)-modified glassy carbon electrode has excellent electrocatalytic ability for the electrooxidation of isoniazid. This fact was appeared as a reduced overpotential of INH oxidation in a wide operational pH range from 2 to 13. It has been found that the catalytic peak ...

  10. Improvement of Heavy Oil Recovery in the VAPEX Process using Montmorillonite Nanoclays Amélioration de la récupération d’huile lourde par utilisation de nanoargiles de Montmorillonite dans le procédé VAPEX

    Directory of Open Access Journals (Sweden)

    Pourabdollah K.

    2011-10-01

    Full Text Available In this paper, the nanoclay particles were introduced as mobile adsorbents in oil reservoirs to adsorb the asphaltenes, reduce the viscosity and enhance the dispersion. The objective of this paper is experimental investigation of enhanced heavy oil recovery using in situ nanoparticles for the first time. Moreover, two thermal analysis methods (thermogravimetry and differential thermal analysis were used to analyze the asphaltene content of residue hydrocarbons in the swept chambers in nano-assisted and conventional VAPEX processes. Experiments were carried out using Iranian heavy oil and propane: the setup consisted of two sand-packed cells; one packed only with glass beads as the oil matrix and the other with glass beads and modified montmorillonite as the nanoclay, while they had similar porosity and permeability. The content of deposited asphaltene in swept matrixes, the propagation pattern of vapor chambers in heavy oil matrixes, and the rates of solvent consumption and oil production were determined. The results elucidated that montmorillonite changed the matrix heterogeneity and led to forming enhanced breakthroughs, to increasing the interfacial surface of vapor/bitumen and to accelerating the oil production. It was found that not only was the rate of vapor injection diminished, but the heavy oil recovery was also markedly enhanced by 30(±4%. Dans cet article, on decrit l’utilisation de particules de nanoargile en tant qu’adsorbant mobile dans des reservoirs d’huile afin d’adsorber les asphaltenes, reduire la viscosite de l’huile et renforcer la dispersion. L’objectif de cet article consiste en la description d’une etude experimentale de recuperation amelioree d’huile lourde par l’utilisation de nanoparticules in situ. Ce qui constitue une premiere. En outre, deux methodes d’analyse thermique (thermogravimetrie et analyse thermique differentielle ont ete utilisees pour analyser la teneur en asphaltene des residus d

  11. Controls over δ44/40Ca and Sr/Ca variations in coccoliths: New perspectives from laboratory cultures and cellular models

    Science.gov (United States)

    Mejía, Luz María; Paytan, Adina; Eisenhauer, Anton; Böhm, Florian; Kolevica, Ana; Bolton, Clara; Méndez-Vicente, Ana; Abrevaya, Lorena; Isensee, Kirsten; Stoll, Heather

    2018-01-01

    Coccoliths comprise a major fraction of the global carbonate sink. Therefore, changes in coccolithophores' Ca isotopic fractionation could affect seawater Ca isotopic composition, affecting interpretations of the global Ca cycle and related changes in seawater chemistry and climate. Despite this, a quantitative interpretation of coccolith Ca isotopic fractionation and a clear understanding of the mechanisms driving it are not yet available. Here, we address this gap in knowledge by developing a simple model (CaSri-Co) to track coccolith Ca isotopic fractionation during cellular Ca uptake and allocation to calcification. We then apply it to published and new δ 44 / 40 Ca and Sr/Ca data of cultured coccolithophores of the species Emiliania huxleyi and Gephyrocapsa oceanica. We identify changes in calcification rates, Ca retention efficiency and solvation-desolvation rates as major drivers of the Ca isotopic fractionation and Sr/Ca variations observed in cultures. Higher calcification rates, higher Ca retention efficiencies and lower solvation-desolvation rates increase both coccolith Ca isotopic fractionation and Sr/Ca. Coccolith Ca isotopic fractionation is most sensitive to changes in solvation-desolvation rates. Changes in Ca retention efficiency may be a major driver of coccolith Sr/Ca variations in cultures. We suggest that substantial changes in the water structure strength caused by past changes in temperature could have induced significant changes in coccolithophores' Ca isotopic fractionation, potentially having some influence on seawater Ca isotopic composition. We also suggest a potential effect on Ca isotopic fractionation via modification of the solvation environment through cellular exudates, a hypothesis that remains to be tested.

  12. Construction of a sensitive and selective sensor for morphine using chitosan coated Fe{sub 3}O{sub 4} magnetic nanoparticle as a modifier

    Energy Technology Data Exchange (ETDEWEB)

    Dehdashtian, Sara [Department of Chemistry, Behbahan Khatam Al-Anbia University of Technology, Behbahan (Iran, Islamic Republic of); Gholivand, Mohammad Bagher, E-mail: mbgholivand@yahoo.com [Department of Analytical Chemistry, Faculty of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of); Shamsipur, Mojtaba; Kariminia, Samira [Department of Analytical Chemistry, Faculty of Chemistry, Razi University, Kermanshah (Iran, Islamic Republic of)

    2016-01-01

    A simple and sensitive sensor based on carbon paste electrode (CPE) modified by chitosan-coated magnetic nanoparticle (CMNP) was developed for the electrochemical determination of morphine (MO). The proposed sensor was characterized with scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The electrooxidation of MO was studied on modified carbon paste electrode using cyclic voltammetry, chronoamperometry and differential pulse voltammetry as diagnostic techniques. The oxidation peak potential of morphine on the CMNP/CPE appeared at 380 mV which was accompanied with smaller overpotential and increase in oxidation peak current compared to that obtained on the bare carbon paste electrode (CPE). Under optimum conditions the sensor provides two linear DPV responses in the range of 10–2000 nM and 2–720 μM for MO with a detection limit of 3 nM. The proposed sensor was successfully applied for monitoring of MO in serum and urine samples and satisfactory results were obtained. - Highlights: • A sensitive and selective voltammetric sensor for MO by using a carbon paste electrode modified with CMNP was introduced. • CMNP as a new modifier facilitates the charge transfer of MO oxidation process. • The proposed sensor was used successfully for MO determination in biological fluids such as serum and urine samples. • This sensor is fabricated easily and has good stability and high sensitivity.

  13. Fabrication and Film Qualification of Sr Modified Pb(Ca) TiO3 Thin Films

    International Nuclear Information System (INIS)

    Naw Hla Myat San; Khin Aye Thwe; Than Than Win; Yin Maung Maung; Ko Ko Kyaw Soe

    2011-12-01

    Strontium and calcium - modified lead titanate (Pb0.7 Ca0.15 Sr0.15 ) TiO3 (PCST)thin films were prepared by using spin coating technique. Phase transition of PCST was interpreted by means of Er-T characteristics. Process temperature dependence on micro-structure of PCST film was studied. Charge conduction mechanism of PCST thin film was also investigated for film qualification.

  14. In situ 3D monitoring of corrosion on carbon steel and ferritic stainless steel embedded in cement paste

    International Nuclear Information System (INIS)

    Itty, Pierre-Adrien; Serdar, Marijana; Meral, Cagla; Parkinson, Dula; MacDowell, Alastair A.; Bjegović, Dubravka; Monteiro, Paulo J.M.

    2014-01-01

    Highlights: • The morphology of the corrosion of steel in cement paste was studied in situ. • During galvanostatic corrosion, carbon steel reinforcement corroded homogeneously. • On ferritic stainless steel, deep corrosion pits formed and caused wider cracks. • The measured rate of steel loss correlated well with Faraday’s law of electrolysis. - Abstract: In a X-ray microcomputed tomography study, active corrosion was induced by galvanostatically corroding steel embedded in cement paste. The results give insight into corrosion product build up, crack formation, leaching of products into the cracks and voids, and differences in morphology of corrosion attack in the case of carbon steel or stainless steel reinforcement. Carbon steel was homogeneously etched away with a homogeneous layer of corrosion products forming at the steel/cement paste interface. For ferritic stainless steel, pits were forming, concentrating the corrosion products locally, which led to more extensive damage on the cement paste cover

  15. Peatland Carbon Dynamics in Alaska During Past Warm Climates

    Science.gov (United States)

    Yu, Z.; Cleary, K.; Massa, C.; Hunt, S. J.; Klein, E. S.; Loisel, J.

    2013-12-01

    Peatlands represent a large belowground carbon (C) pool in the biosphere. However, how peatland C sequestration capacity varies with changes in climate and climate-induced disturbance is still poorly understood and debated. Here we summarize results from Alaskan peatlands to document how peat C accumulation has responded to past warm climate intervals. We find that the greatest C accumulation rates at sites from the Kenai Peninsula to the North Slope occurred during the Holocene thermal maximum (HTM) in the early Holocene. This time period also corresponds with explosive formation and expansion of new peatlands on the landscape across Alaska. In addition, we note that many peatlands that existed during the earlier Holocene on the North Slope have disappeared and are presently covered by mineral soils under tundra or sandy deposits. During the Medieval Climate Anomaly (MCA) around 1000-500 years ago, several peatlands in Alaska show high rates of C accumulation when compared to the period before the MCA during the Neoglacial or the following Little Ice Age period. Altogether, our results indicate that the Alaskan landscape was very different during the last 10,000 years and that peatlands can rapidly accumulate C under warm climatic conditions. We speculate that warmth-stimulated increase in plant production surpasses increase in peat decomposition during the early Holocene, and potentially also during the MCA. Other factors that might have contributed to rapid peat accumulation during the early Holocene include increased summer sunlight, lowered sea levels, and decreased sea-ice cover/duration. Summer insolation was ca. 8% higher than today during the early Holocene due to orbital variations, which likely promoted plant productivity by increasing growing seasons sunlight. Furthermore, lower sea levels and exposed shallow continental shelves in the Beaufort Sea (Arctic Ocean) would have made the present-day Arctic Coastal Plain more continental, with warmer summers

  16. Electrochemical selective detection of dopamine on microbial carbohydrate-doped multiwall carbon nanotube-modified electrodes.

    Science.gov (United States)

    Jin, Joon-Hyung; Cho, Eunae; Jung, Seunho

    2010-03-01

    Microbial carbohydrate-doped multiwall carbon nanotube (MWNT)-modified electrodes were prepared for the purpose of determining if 4-(2-aminoethyl)benzene-1,2-diol (3,4-dihydroxyphenylalanine; dopamine) exists in the presence of 0.5 mM ascorbic acid, a representative interfering agent in neurotransmitter detection. The microbial carbohydrate dopants were alpha-cyclosophorohexadecaose (alpha-C16) from Xanthomonas oryzae and cyclic-(1 --> 2)-beta-d-glucan (Cys) from Rhizobium meliloti. The cyclic voltammetric responses showed that the highest sensitivity (5.8 x 10(-3) mA cm(-2) microM(-1)) is attained with the Cys-doped MWNT-modified ultra-trace carbon electrode, and that the alpha-C16-doped MWNT-modified glassy carbon electrode displays the best selectivity to dopamine (the approximate peak potential separation is 310 mV).

  17. Mechanical Properties of Epoxy and Its Carbon Fiber Composites Modified by Nanoparticles

    Directory of Open Access Journals (Sweden)

    Fang Liu

    2017-01-01

    Full Text Available Compressive properties are commonly weak parts in structural application of fiber composites. Matrix modification may provide an effective way to improve compressive performance of the composites. In this work, the compressive property of epoxies (usually as matrices of fiber composites modified by different types of nanoparticles was firstly investigated for the following study on the compressive property of carbon fiber reinforced epoxy composites. Carbon fiber/epoxy composites were fabricated by vacuum assisted resin infusion molding (VARIM technique using stitched unidirectional carbon fabrics, with the matrices modified with nanosilica, halloysite, and liquid rubber. Testing results showed that the effect of different particle contents on the compressive property of fiber/epoxy composites was more obvious than that in epoxies. Both the compressive and flexural results showed that rigid nanoparticles (nanosilica and halloysite have evident strengthening effects on the compression and flexural responses of the carbon fiber composite laminates fabricated from fabrics.

  18. Mixed ion-exchanger chemically modified carbon paste ion-selective electrodes for determination of triprolidine hydrochloride

    Directory of Open Access Journals (Sweden)

    Yousry M. Issa

    2010-01-01

    Full Text Available Triprolidine hydrochloride (TpCl ion-selective carbon paste electrodes were constructed using Tp-TPB/Tp-CoN and Tp-TPB/Tp-PTA as ion-exchangers. The two electrodes revealed Nernstian responses with slopes of 58.4 and 58.1 mV decade−1 at 25 °C in the ranges 6 × 10−6–1 × 10−2 and 2 × 10−5–1 × 10−2 M for Tp-TPB/Tp-CoN and Tp-TPB/Tp-PTA, respectively. The potentials of these electrodes were independent of pH in the ranges of 2.5–7.0 and 4.5–7.0, and detection limits were 6 × 10−6 and 1 × 10−5 M for Tp-TPB/Tp-CoN and Tp-TPB/Tp-PTA, respectively. The electrodes showed a very good selectivity for TpCl with respect to a large number of inorganic cations and compounds. The standard addition, potentiometric titration methods and FIA were applied to the determination of TpCl in pure solutions and pharmaceutical preparations. The results obtained were in close agreement with those found by the official method. The mean recovery values were 100.91% and 97.92% with low coefficient of variation values of 0.94%, and 0.56% in pure solutions, 99.82% and 98.53% with coefficient of variation values of 2.20%, and 0.73% for Actifed tablet and Actifed syrup, respectively, using the Tp-TPB/Tp-CoN electrode, and 98.85%, and 99.18% with coefficient of variation values of 0.48% and 0.85% for Actifed tablet and Actifed syrup, respectively, using the Tp-TPB/Tp-PTA electrode.

  19. (Ca,Mg)-Carbonate and Mg-Carbonate at the Phoenix Landing Site: Evaluation of the Phoenix Lander's Thermal Evolved Gas Analyzer (TEGA) Data Using Laboratory Simulations

    Science.gov (United States)

    Sutter, B.; Ming, D. W.; Boynton, W. V.; Niles, P. B.; Morris, R. V.

    2011-01-01

    Calcium carbonate (4.5 wt. %) was detected in the soil at the Phoenix Landing site by the Phoenix Lander s The Thermal and Evolved Gas Analyzer [1]. TEGA operated at 12 mbar pressure, yet the detection of calcium carbonate is based on interpretations derived from thermal analysis literature of carbonates measured under ambient (1000 mbar) and vacuum (10(exp -3) mbar) conditions [2,3] as well as at 100 and 30 mbar [4,5] and one analysis at 12 mbar by the TEGA engineering qualification model (TEGA-EQM). Thermodynamics (Te = H/ S) dictate that pressure affects entropy ( S) which causes the temperature (Te) of mineral decomposition at one pressure to differ from Te obtained at another pressure. Thermal decomposition analyses of Fe-, Mg-, and Ca-bearing carbonates at 12 mbar is required to enhance the understanding of the TEGA results at TEGA operating pressures. The objectives of this work are to (1) evaluate the thermal and evolved gas behavior of a suite of Fe-, Mg-, Ca-carbonate minerals at 1000 and 12 mbar and (2) discuss possible emplacement mechanisms for the Phoenix carbonate.

  20. Aggregation of montmorillonite and organic matter in aqueous media containing artificial seawater

    Directory of Open Access Journals (Sweden)

    Kim Jinwook

    2009-01-01

    Full Text Available Abstract Background The dispersion-aggregation behaviors of suspended colloids in rivers and estuaries are affected by the compositions of suspended materials (i.e., clay minerals vs. organic macromolecules and salinity. Laboratory experiments were conducted to investigate the dispersion and aggregation mechanisms of suspended particles under simulated river and estuarine conditions. The average hydrodynamic diameters of suspended particles (representing degree of aggregation and zeta potential (representing the electrokinetic properties of suspended colloids and aggregates were determined for systems containing suspended montmorillonite, humic acid, and/or chitin at the circumneutral pH over a range of salinity (0 – 7.2 psu. Results The montmorillonite-only system increased the degree of aggregation with salinity increase, as would be expected for suspended colloids whose dispersion-aggregation behavior is largely controlled by the surface electrostatic properties and van der Waals forces. When montmorillonite is combined with humic acid or chitin, the aggregation of montmorillonite was effectively inhibited. The surface interaction energy model calculations reveal that the steric repulsion, rather than the increase in electronegativity, is the primary cause for the inhibition of aggregation by the addition of humic acid or chitin. Conclusion These results help explain the range of dispersion-aggregation behaviors observed in natural river and estuarine systems. It is postulated that the composition of suspended particles, specifically the availability of steric polymers such as those contained in humic acid, determine whether the river suspension is rapidly aggregated and settled or remains dispersed in suspension when it encounters increasingly saline environments of estuaries and oceans.

  1. Restricted Inter-ocean Exchange and Attenuated Biological Export Caused Enhanced Carbonate Preservation in the PETM Ocean

    Science.gov (United States)

    Luo, Y.; Boudreau, B. P.; Dickens, G. R.; Sluijs, A.; Middelburg, J. J.

    2015-12-01

    Carbon dioxide (CO2) release during the Paleocene-Eocene Thermal Maximum (PETM, 55.8 Myr BP) acidified the oceans, causing a decrease in calcium carbonate (CaCO3) preservation. During the subsequent recovery from this acidification, the sediment CaCO3 content came to exceed pre-PETM values, known as over-deepening or over-shooting. Past studies claim to explain these trends, but have failed to reproduce quantitatively the time series of CaCO3 preservation. We employ a simple biogeochemical model to recreate the CaCO3 records preserved at Walvis Ridge of the Atlantic Ocean. Replication of the observed changes, both shallowing and the subsequent over-deepening, requires two conditions not previously considered: (1) limited deep-water exchange between the Indo-Atlantic and Pacific oceans and (2) a ~50% reduction in the export of CaCO3 to the deep sea during acidification. Contrary to past theories that attributed over-deepening to increased riverine alkalinity input, we find that over-deepening is an emergent property, generated at constant riverine input when attenuation of CaCO3 export causes an unbalanced alkalinity input to the deep oceans (alkalinization) and the development of deep super-saturation. Restoration of CaCO3 export, particularly in the super-saturated deep Indo-Atlantic ocean, later in the PETM leads to greater accumulation of carbonates, ergo over-shooting, which returns the ocean to pre-PETM conditions over a time scale greater than 200 kyr. While this feedback between carbonate export and the riverine input has not previously been considered, it appears to constitute an important modification of the classic carbonate compensation concept used to explain oceanic response to acidification.

  2. Adsorption characteristics of N-nitrosodimethylamine from aqueous solution on surface-modified activated carbons

    Energy Technology Data Exchange (ETDEWEB)

    Xiaodong, Dai [Chemistry and Chemical Engineering School, China University of Petroleum, Dongying 257061, Shandong (China); Institute for Sustainability and Innovation, Victoria University, Melbourne, VIC 8001 (Australia); Zou, Linda [SA Water Centre for Water Management and Reuse, University of South Australia, Adelaide, SA5095 (Australia); Zifeng, Yan [Chemistry and Chemical Engineering School, China University of Petroleum, Dongying 257061, Shandong (China); Millikan, Mary [Institute for Sustainability and Innovation, Victoria University, Melbourne, VIC 8001 (Australia)

    2009-08-30

    This study investigated the removal of N-nitrosodimethylamine (NDMA) by an adsorption mechanism using commercially available activated carbons and surface-modified activated carbons. The effects of the modification on the properties of the activated carbon were studied by N{sub 2} adsorption/desorption, Diffuse Reflectance Infrared Fourier Transmission (DRIFT) analysis and X-Ray Photoelectron Spectroscopy (XPS). Adsorption experiments revealed that the activated carbons demonstrated a greater capacity for NDMA adsorption capacity than can be achieved using zeolite. The equilibrium data was fitted to the Freundlich equation and it was found that the adsorption capacity was significantly influenced by the micropore size, relative pore volume and surface characteristics. Adsorption experiments were conducted using unmodified and modified activated carbons. The results indicated that the adsorption capacity of NDMA can be significantly improved by heat treatment and doping of TiO{sub 2} particles. This was because the surface treatments yielded more hydrophobic sites and fewer oxygen-containing surface functional groups, and consequently an increased capacity for NDMA adsorption.

  3. Adsorption characteristics of N-nitrosodimethylamine from aqueous solution on surface-modified activated carbons

    International Nuclear Information System (INIS)

    Dai Xiaodong; Zou, Linda; Yan Zifeng; Millikan, Mary

    2009-01-01

    This study investigated the removal of N-nitrosodimethylamine (NDMA) by an adsorption mechanism using commercially available activated carbons and surface-modified activated carbons. The effects of the modification on the properties of the activated carbon were studied by N 2 adsorption/desorption, Diffuse Reflectance Infrared Fourier Transmission (DRIFT) analysis and X-Ray Photoelectron Spectroscopy (XPS). Adsorption experiments revealed that the activated carbons demonstrated a greater capacity for NDMA adsorption capacity than can be achieved using zeolite. The equilibrium data was fitted to the Freundlich equation and it was found that the adsorption capacity was significantly influenced by the micropore size, relative pore volume and surface characteristics. Adsorption experiments were conducted using unmodified and modified activated carbons. The results indicated that the adsorption capacity of NDMA can be significantly improved by heat treatment and doping of TiO 2 particles. This was because the surface treatments yielded more hydrophobic sites and fewer oxygen-containing surface functional groups, and consequently an increased capacity for NDMA adsorption.

  4. Thermal Stabilization of Enzymes Immobilized within Carbon Paste Electrodes.

    Science.gov (United States)

    Wang, J; Liu, J; Cepra, G

    1997-08-01

    In this note we report on the remarkable thermal stabilization of enzymes immobilized in carbon paste electrodes. Amperometric biosensors are shown for the first time to withstand a prolonged high-temperature (>50 °C) stress. Nearly full activity of glucose oxidase is retained over periods of up to 4 months of thermal stress at 60-80 °C. Dramatic improvements in the thermostability are observed for polyphenol oxidase, lactate oxidase, alcohol oxidase, horseradish peroxidase, and amino acid oxidase. Such resistance to heat-induced denaturation is attributed to the conformational rigidity of these biocatalysts within the highly hydrophobic (mineral oil or silicone grease) pasting liquid. While no chemical stabilizer is needed for attaining such protective action, it appears that low humidity (i.e., low water content) is essential for minimizing the protein mobility. Besides their implications for electrochemical biosensors, such observations should lead to a new generation of thermoresistant enzyme reactors based on nonpolar semisolid supports.

  5. Electrocatalytic Study of Paracetamol at a Single-Walled Carbon Nanotube/Nickel Nanocomposite Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Koh Sing Ngai

    2015-01-01

    Full Text Available A rapid, simple, and sensitive method for the electrochemical determination of paracetamol was developed. A single-walled carbon nanotube/nickel (SWCNT/Ni nanocomposite was prepared and immobilized on a glassy carbon electrode (GCE surface via mechanical attachment. This paper reports the voltammetry study on the effect of paracetamol concentration, scan rate, pH, and temperature at a SWCNT/Ni-modified electrode in the determination of paracetamol. The characterization of the SWCNT/Ni/GCE was performed by cyclic voltammetry. Variable pressure scanning electron microscopy (VPSEM and energy dispersive X-ray (EDX spectrometer were used to examine the surface morphology and elemental profile of the modified electrode, respectively. Cyclic voltammetry showed significant enhancement in peak current for the determination of paracetamol at the SWCNT/Ni-modified electrode. A linear calibration curve was obtained for the paracetamol concentration between 0.05 and 0.50 mM. The SWCNT/Ni/GCE displayed a sensitivity of 64 mA M−1 and a detection limit of 1.17 × 10−7 M in paracetamol detection. The proposed electrode can be applied for the determination of paracetamol in real pharmaceutical samples with satisfactory performance. Results indicate that electrodes modified with SWCNT and nickel nanoparticles exhibit better electrocatalytic activity towards paracetamol.

  6. Synthesis and Characterization of the Hybrid Clay- Based Material Montmorillonite-Melanoidin: A Potential Soil Model

    Energy Technology Data Exchange (ETDEWEB)

    V Vilas; B Matthiasch; J Huth; J Kratz; S Rubert de la Rosa; P Michel; T Schäfer

    2011-12-31

    The study of the interactions among metals, minerals, and humic substances is essential in understanding the migration of inorganic pollutants in the geosphere. A considerable amount of organic matter in the environment is associated with clay minerals. To understand the role of organic matter in the environment and its association with clay minerals, a hybrid clay-based material (HCM), montmorillonite (STx-1)-melanoidin, was prepared from L-tyrosine and L-glutamic acid by the Maillard reaction. The HCM was characterized by elemental analysis, nuclear magnetic resonance, x-ray photoelectron spectroscopy (XPS), scanning transmission x-ray microscopy (STXM), and thermal analysis. The presence of organic materials on the surface was confirmed by XPS and STXM. The STXM results showed the presence of organic spots on the surface of the STx-1 and the characterization of the functional groups present in those spots. Thermal analysis confirmed the existence of organic materials in the montmorillonite interlayer, indicating the formation of a composite of melanoidin and montmorillonite. The melanoidin appeared to be located partially between the layers of montmorillonite and partially at the surface, forming a structure that resembles the way a cork sits on the top of a champagne bottle.

  7. Homoionic inorganic montmorillonites as fillers for Polyamide 6 nanocomposites

    Czech Academy of Sciences Publication Activity Database

    Kadlecová, Z.; Puffr, Rudolf; Baldrian, Josef; Schmidt, Pavel; Roda, J.; Brožek, J.

    2008-01-01

    Roč. 44, č. 9 (2008), s. 2798-2806 ISSN 0014-3057 Institutional research plan: CEZ:AV0Z40500505 Keywords : poly(.epsilon.-caprolactam) nanocomposite * calcium and magnesium montmorillonites * WAX analysis Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.143, year: 2008

  8. Electrocatalytic reduction of dioxygen by cobalt porphyrin-modified glassy carbon electrode with single-walled carbon nanotubes and nafion in aqueous solutions

    International Nuclear Information System (INIS)

    Choi, Ayoung; Jeong, Haesang; Kim, Songmi; Jo, Suhee; Jeon, Seungwon

    2008-01-01

    Cobalt porphyrin (CoP)-modified glassy carbon electrode (GCE) with single-walled carbon nanotubes (SWNTs) and Nafion demonstrated a higher electrocatalytic activity for the reduction of dioxygen in 0.1 M H 2 SO 4 solution. Cyclic and hydrodynamic voltammetry at the CoP-SWNTs/GCE-modified electrodes in O 2 -saturated aqueous solutions was used to study the electrocatalytic pathway. Compared with the CoP/GCE-modified electrodes, the reduction potential of dioxygen at the CoP-SWNTs/GCE-modified electrodes was shifted to the positive direction and the limiting current was greatly increased. Especially, the Co(TMPP)-SWNTs/GCE-modified electrode was catalyzed effectively by the 4e - reduction of dioxygen to water, because hydrodynamic voltammetry revealed the transference of approximately four electrons for dioxygen reduction and the minimal generation of hydrogen peroxide in the process of dioxygen reduction

  9. Design of a new hypoxanthine biosensor: xanthine oxidase modified carbon film and multi-walled carbon nanotube/carbon film electrodes.

    Science.gov (United States)

    Torres, A Carolina; Ghica, M Emilia; Brett, Christopher M A

    2013-04-01

    A new and simple-to-prepare hypoxanthine biosensor has been developed using xanthine oxidase (XOD) immobilised on carbon electrode surfaces. XOD was immobilised by glutaraldehyde cross-linking on carbon film (CF) electrodes and on carbon nanotube (CNT) modified CF (CNT/CF). A comparison of the performance of the two configurations was carried out by the current response using amperometry at fixed potential; the best characteristics being exhibited by XOD/CNT/CF modified electrodes. The effects of electrolyte pH and applied potential were evaluated, and a proposal is made for the enzyme mechanism of action involving competition between regeneration of flavin adenine dinucleotide and reduction of hydrogen peroxide. Under optimised conditions, the determination of hypoxanthine was carried out at -0.2 V vs. a saturated calomel electrode (SCE) with a detection limit of 0.75 μM on electrodes with CNT and at -0.3 V vs. SCE with a detection limit of 0.77 μM on electrodes without CNT. The applicability of the biosensor was verified by performing an interference study, reproducibility and stability were investigated, and hypoxanthine was successfully determined in sardine and shrimp samples.

  10. Flow-induced crystallization of a nano composite of poly(butylene adipate-co-terephthalate)/montmorillonite

    International Nuclear Information System (INIS)

    Bonel, Alan B.; Rego, Bruna T.; Beatrice, Cesar A.G.; Marini, Juliano; Bretas, Rosario E.S.

    2011-01-01

    Poly(butylene adipate-co-terephthalate) (PBAT) with 5wt% of an organically modified montmorillonite with polar surfactant was prepared by melt blending in a co-rotational twin-screw extruder at 160 degree C. 100rpm and 1 kg/h. Both pure polymer and nano composite were characterized by wide measurements. The study of the flow-induced crystallization was also done by rheological measurements, monitoring the viscosity as a function of time. The nano clay's lamellas were intercalated in the polymer m loss moduli of the nano composite, at low frequencies, showed that the particles of the nano clay were well dispersed and distributed thru the PBAT matrix. Finally, the presence of the nano clay's particles reduced the induction tim crystals growth, due to the strong interactions with the PBAT chains. (author)

  11. In situ 3D monitoring of corrosion on carbon steel and ferritic stainless steel embedded in cement paste

    KAUST Repository

    Itty, Pierre-Adrien

    2014-06-01

    In a X-ray microcomputed tomography study, active corrosion was induced by galvanostatically corroding steel embedded in cement paste. The results give insight into corrosion product build up, crack formation, leaching of products into the cracks and voids, and differences in morphology of corrosion attack in the case of carbon steel or stainless steel reinforcement. Carbon steel was homogeneously etched away with a homogeneous layer of corrosion products forming at the steel/cement paste interface. For ferritic stainless steel, pits were forming, concentrating the corrosion products locally, which led to more extensive damage on the cement paste cover. © 2014 Elsevier Ltd.

  12. In situ 3D monitoring of corrosion on carbon steel and ferritic stainless steel embedded in cement paste

    KAUST Repository

    Itty, Pierre-Adrien; Serdar, Marijana; Meral, Cagla; Parkinson, Dula; MacDowell, Alastair A.; Bjegović, Dubravka; Monteiro, Paulo J.M.

    2014-01-01

    In a X-ray microcomputed tomography study, active corrosion was induced by galvanostatically corroding steel embedded in cement paste. The results give insight into corrosion product build up, crack formation, leaching of products into the cracks and voids, and differences in morphology of corrosion attack in the case of carbon steel or stainless steel reinforcement. Carbon steel was homogeneously etched away with a homogeneous layer of corrosion products forming at the steel/cement paste interface. For ferritic stainless steel, pits were forming, concentrating the corrosion products locally, which led to more extensive damage on the cement paste cover. © 2014 Elsevier Ltd.

  13. Molecular Simulation Models of Carbon Dioxide Intercalation in Hydrated Sodium Montmorillonite

    Energy Technology Data Exchange (ETDEWEB)

    Myshakin, Evgeniy [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Saidi, Wissam [Univ. of Pittsburgh, PA (United States); Romanov, Vyacheslav [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Cygan, Randall [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jordan, Kenneth [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Univ. of Pittsburgh, PA (United States); Guthrie, George [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-11-22

    In this study, classical molecular dynamics simulations and density functional theory (DFT)-based molecular dynamics are used to elucidate the process of CO2 intercalation into hydrated Na-montmorillonite at P-T conditions relevant to geological formations suitable for CO2 storage. Of particular interest are the structural and transport properties of interlayer species after CO2 intercalation. The conducted simulations allowed the research team to quantify expansion/contraction of smectite as a function of CO2 and H2O compositions. The resulting swelling curves can be used to gauge the amount of stored CO2, compare it to the experiment, and estimate changes in geomechanical properties of the storage formation. The obtained results showed that the infrared signal of the asymmetric stretch vibration of CO2 molecule is extremely sensitive to the solvent environment. The extent of the frequency shift relative to the gas-phase value can be used to probe hydration level in the interlayer with intercalated CO2. Interaction of supercritical CO2 with brine in deep geological formations promotes an increase of hydrophobicity of clay surfaces. As a result of wettability alteration, estimated diffusion constants of CO2 and H2O increase with the increased CO2 load; this can contribute to faster migration of CO2 throughout the formation.

  14. Solid-state synthesis and electrical properties of polyaniline/Cu-montmorillonite nanocomposite

    International Nuclear Information System (INIS)

    Bekri-Abbes, Imene; Srasra, Ezzeddine

    2010-01-01

    In this paper, the solid-state synthesis of polyaniline/Cu-montmorillonite nanocomposite is reported. Mixture of anilinium chlorure and Cu exchanged montmorillonite was grinded at room temperature while we vary the molar rate of aniline to interlayer Cu 2+ cations (R) from 0.5 to 6. The properties of the hybrid compounds are characterized by X-ray diffraction, thermogravimetric analysis, SEM, FTIR and impedance spectroscopy. The results showed that the structure and the conductivity of PANI in hybrid materials depend on R. The ac conduction showed a regime of constant dc conductivity at low frequencies and a crossover to a frequency-dependent regime of the type A ω s at high frequencies.

  15. Calcification in a marginal sea - influence of seawater [Ca2+] and carbonate chemistry on bivalve shell formation

    Science.gov (United States)

    Thomsen, Jörn; Ramesh, Kirti; Sanders, Trystan; Bleich, Markus; Melzner, Frank

    2018-03-01

    In estuarine coastal systems such as the Baltic Sea, mussels suffer from low salinity which limits their distribution. Anthropogenic climate change is expected to cause further desalination which will lead to local extinctions of mussels in the low saline areas. It is commonly accepted that mussel distribution is limited by osmotic stress. However, along the salinity gradient, environmental conditions for biomineralization are successively becoming more adverse as a result of reduced [Ca2+] and dissolved inorganic carbon (CT) availability. In larvae, calcification is an essential process starting during early development with formation of the prodissoconch I (PD I) shell, which is completed under optimal conditions within 2 days. Experimental manipulations of seawater [Ca2+] start to impair PD I formation in Mytilus larvae at concentrations below 3 mM, which corresponds to conditions present in the Baltic at salinities below 8 g kg-1. In addition, lowering dissolved inorganic carbon to critical concentrations (< 1 mM) similarly affected PD I size, which was well correlated with calculated ΩAragonite and [Ca2+][HCO3-] / [H+] in all treatments. Comparing results for larvae from the western Baltic with a population from the central Baltic revealed a significantly higher tolerance of PD I formation to lowered [Ca2+] and [Ca2+][HCO3-] / [H+] in the low saline adapted population. This may result from genetic adaptation to the more adverse environmental conditions prevailing in the low saline areas of the Baltic. The combined effects of lowered [Ca2+] and adverse carbonate chemistry represent major limiting factors for bivalve calcification and can thereby contribute to distribution limits of mussels in the Baltic Sea.

  16. Electrocatalytic oxidation of hydrazine at overoxidized polypyrrole film modified glassy carbon electrode

    Energy Technology Data Exchange (ETDEWEB)

    Majidi, Mir Reza [Department of Analytical Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz 51664 (Iran, Islamic Republic of); Jouyban, Abolghasem [Faculty of Pharmacy and Drug Applied Research Center, Tabriz University of Medical Sciences, Tabriz 51664 (Iran, Islamic Republic of); Asadpour-Zeynali, Karim [Department of Analytical Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz 51664 (Iran, Islamic Republic of)]. E-mail: asadpour@tabrizu.ac.ir

    2007-06-20

    Electrocatalytic oxidation of hydrazine (HZ) was studied on an overoxidized polypyrrole (OPPy) modified glassy carbon electrode using cyclic voltammetry and chronoamperometry techniques. The OPPy-modified glassy carbon electrode has very high catalytic ability for electrooxidation of HZ, which appeared as a reduced overpotential in a wide operational pH range of 5-10. The overall numbers of electrons involved in the catalytic oxidation of HZ, the number of electrons involved in the rate-determining and diffusion coefficient of HZ were estimated using cyclic voltammetry and chronoamperometry. It has been shown that using the OPPy-modified electrode, HZ can be determined by cyclic voltammetry and amperometry with limit of detection 36 and 3.7 {mu}M, respectively. The results of the analysis suggest that the proposed method promises accurate results and could be employed for the routine determination of HZ.

  17. A solid paraffin-based carbon paste electrode modified with 2-aminothiazole organofunctionalized silica for differential pulse adsorptive stripping analysis of nickel in ethanol fuel

    International Nuclear Information System (INIS)

    Takeuchi, Regina M.; Santos, Andre L.; Padilha, Pedro M.; Stradiotto, Nelson R.

    2007-01-01

    A solid paraffin-based carbon paste electrode modified with 2-aminothiazole organofunctionalized silica (SiAt-SPCPE) was applied to Ni 2+ determination in commercial ethanol fuel samples. The proposed method comprised four steps: (1) Ni 2+ preconcentration at open circuit potential directly in the ethanol fuel sample, (2) transference of the electrode to an electrochemical cell containing DMG, (3) differential pulse voltammogram registering and (4) surface regeneration by polishing the electrode. The proposed method combines the high Ni 2+ adsorption capacity presented by 2-aminothiazole organofunctionalized silica with the electrochemical properties of the Ni(DMG) 2 complex, whose electrochemical reduction provides the analytical signal. All experimental parameters involved in the proposed method were optimized. Using a preconcentration time of 20 min, it was obtained a linear range from 7.5 x 10 -9 to 1.0 x 10 -6 mol L -1 with detection limit of 2.0 x 10 -9 mol L -1 . Recovery values between 96.5 and 102.4% were obtained for commercial samples spiked with 1.0 μmol L -1 Ni 2+ and the developed electrode was totally stable in ethanolic solutions. The contents of Ni 2+ found in the commercial samples using the proposed method were compared to those obtained by graphite furnace atomic absorption spectroscopy by using the F- and t-test. Neither the F- nor t-values exceeded the critical values at 95% confidence level, confirming that there are not statistical differences between the results obtained by both methods. These results indicate that the developed electrode can be successfully employed to reliable Ni 2+ determination in commercial ethanol fuel samples without any sample pretreatment or dilution step

  18. Acidity of edge surface sites of montmorillonite and kaolinite

    Science.gov (United States)

    Liu, Xiandong; Lu, Xiancai; Sprik, Michiel; Cheng, Jun; Meijer, Evert Jan; Wang, Rucheng

    2013-09-01

    Acid-base chemistry of clay minerals is central to their interfacial properties, but up to now a quantitative understanding on the surface acidity is still lacking. In this study, with first principles molecular dynamics (FPMD) based vertical energy gap technique, we calculate the acidity constants of surface groups on (0 1 0)-type edges of montmorillonite and kaolinite, which are representatives of 2:1 and 1:1-type clay minerals, respectively. It shows that tbnd Si-OH and tbnd Al-OH2OH groups of kaolinite have pKas of 6.9 and 5.7 and those of montmorillonite have pKas of 7.0 and 8.3, respectively. For each mineral, the calculated pKas are consistent with the experimental ranges derived from fittings of titration curves, indicating that tbnd Si-OH and tbnd Al-OH2OH groups are the major acidic sites responsible to pH-dependent experimental observations. The effect of Mg substitution in montmorillonite is investigated and it is found that Mg substitution increases the pKas of the neighboring tbnd Si-OH and tbnd Si-OH2 groups by 2-3 pKa units. Furthermore, our calculation shows that the pKa of edge tbnd Mg-(OH2)2 is as high as 13.2, indicating the protonated state dominates under common pH. Together with previous adsorption experiments, our derived acidity constants suggest that tbnd Si-O- and tbnd Al-(OH)2 groups are the most probable edge sites for complexing heavy metal cations.

  19. Trace level and highly selective determination of urea in various real samples based upon voltammetric analysis of diacetylmonoxime-urea reaction product on the carbon nanotube/carbon paste electrode.

    Science.gov (United States)

    Alizadeh, Taher; Ganjali, Mohammad Reza; Rafiei, Faride

    2017-06-29

    In this study an innovative method was introduced for selective and precise determination of urea in various real samples including urine, blood serum, soil and water. The method was based on the square wave voltammetry determination of an electroactive product, generated during diacetylmonoxime reaction with urea. A carbon paste electrode, modified with multi-walled carbon nanotubes (MWCNTs) was found to be an appropriate electrochemical transducer for recording of the electrochemical signal. It was found that the chemical reaction conditions influenced the analytical signal directly. The calibration graph of the method was linear in the range of 1 × 10 -7 - 1 × 10 -2  mol L -1 . The detection limit was calculated to be 52 nmol L -1 . Relative standard error of the method was also calculated to be 3.9% (n = 3). The developed determination procedure was applied for urea determination in various real samples including soil, urine, plasma and water samples. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Potentiometric stripping analysis of arsenic using a graphene paste electrode modified with a thiacrown ether and gold nanoparticles

    International Nuclear Information System (INIS)

    Sanghavi, Bankim J.; Gadhari, Nayan S.; Kalambate, Pramod K.; Srivastava, Ashwini K.; Karna, Shashi P.

    2015-01-01

    An electrochemical method is presented for the determination of arsenic at subnanomolar levels. It is based on potentiometric stripping analysis (PSA) using a graphene paste electrode modified with the thiacrown 1,4,7-trithiacyclononane (TTCN) and gold nanoparticles (AuNPs). The electrode surface was characterized by means of cyclic voltammetry, electrochemical impedance spectroscopy, chronocoulometry and scanning electron microscopy. The modified electrode displays a 15-fold enhancement in the PSA signal (dt/dE) compared to a conventional graphene paste electrode. Under optimized conditions, the signal is proportional to the concentration of As(III) in the range from 25 pM to 34 nM (r 2  = 0.9977), and the detection limit (SD/s) is as low as 8 pM. The modified electrode was successfully applied to the determination of total arsenic [i.e., As(III) and As(V)] in pharmaceutical formulations, human hair, sea water, fruits, vegetables, soil, and wine samples. (author)