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Sample records for silica gel sorbent

  1. Preparation of an aminopropyl imidazole-modified silica gel as a sorbent for solid-phase extraction of carboxylic acid compounds and polycyclic aromatic hydrocarbons.

    Science.gov (United States)

    Wang, Na; Guo, Yong; Wang, Licheng; Liang, Xiaojing; Liu, Shujuan; Jiang, Shengxiang

    2014-05-21

    In this paper, a kind of aminopropyl imidazole-modified silica sorbent was synthesized and used as a solid-phase extraction (SPE) sorbent for the determination of carboxylic acid compounds and polycyclic aromatic hydrocarbons (PAHs). The resultant aminopropyl imidazole-modified silica sorbent was characterized by Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (EA) to ensure the successful binding of aminopropyl imidazole on the surface of silica gel. Then the aminopropyl imidazole-modified silica sorbent served as a SPE sorbent for the enrichment of carboxylic acid compounds and PAHs. The new sorbent exhibited high extraction efficiency towards the tested compounds and the results show that such a sorbent can offer multiple intermolecular interactions: electrostatic, π-π, and hydrophobic interactions. Several parameters affecting the extraction recovery, such as the pH of sample solution, the pH of eluent, the solubility of eluent, the volume of eluent, and sample loading, were also investigated. Under the optimized conditions, the proposed method was applied to the analysis of four carboxylic acid compounds and four PAHs in environmental water samples. Good linearities were obtained for all the tested compounds with R(2) larger than 0.9903. The limits of detection were found to be in the range of 0.0065-0.5 μg L(-1). The recovery values of spiked river water samples were from 63.2% to 112.3% with relative standard deviations (RSDs) less than 10.1% (n = 4).

  2. Silica- and germania-based dual-ligand sol-gel organic-inorganic hybrid sorbents combining superhydrophobicity and π-π interaction. The role of inorganic substrate in sol-gel capillary microextraction.

    Science.gov (United States)

    Seyyal, Emre; Malik, Abdul

    2017-04-29

    Principles of sol-gel chemistry were utilized to create silica- and germania-based dual-ligand surface-bonded sol-gel coatings providing enhanced performance in capillary microextraction (CME) through a combination of ligand superhydrophobicity and π-π interaction. These organic-inorganic hybrid coatings were prepared using sol-gel precursors with bonded perfluorododecyl (PF-C 12 ) and phenethyl (PhE) ligands. Here, the ability of the PF-C 12 ligand to provide enhanced hydrophobic interaction was advantageously combined with π-π interaction capability of the PhE moiety to attain the desired sorbent performance in CME. The effect of the inorganic sorbent component on microextraction performance of was explored by comparing microextraction characteristics of silica- and germania-based sol-gel sorbents. The germania-based dual-ligand sol-gel sorbent demonstrated superior CME performance compared to its silica-based counterpart. Thermogravimetric analysis (TGA) of the created silica- and germania-based dual-ligand sol-gel sorbents suggested higher carbon loading on the germania-based sorbent. This might be indicative of more effective condensation of the organic ligand-bearing sol-gel-active chemical species to the germania-based sol-gel network (than to its silica-based counterpart) evolving in the sol solution. The type and concentration of the organic ligands were varied in the sol-gel sorbents to fine-tune extraction selectivity toward different classes of analytes. Specific extraction (SE) values were used for an objective comparison of the prepared sol-gel CME sorbents. The sorbents with higher content of PF-C 12 showed remarkable affinity for aliphatic hydrocarbons. Compared to their single-ligand sol-gel counterparts, the dual-ligand sol-gel coatings demonstrated significantly superior CME performance in the extraction of alkylbenzenes, providing up to ∼65.0% higher SE values. The prepared sol-gel CME coatings provided low ng L -1 limit of detections (LOD

  3. Silica gel matrix immobilized Chlorophyta hydrodictyon africanum ...

    African Journals Online (AJOL)

    Chlorophyta hydrodictyon africanum was immobilized on a silica gel matrix to improve its mechanical properties. The algae-silica gel adsorbent was used for batch sorption studies of a cationic dye, methylene blue (MB). Optimum adsorption was obtained with a dosage of 0.8 g bio sorbent. Results from sorption studies ...

  4. Sol-gel derived sorbents

    Science.gov (United States)

    Sigman, Michael E.; Dindal, Amy B.

    2003-11-11

    Described is a method for producing copolymerized sol-gel derived sorbent particles for the production of copolymerized sol-gel derived sorbent material. The method for producing copolymerized sol-gel derived sorbent particles comprises adding a basic solution to an aqueous metal alkoxide mixture for a pH.ltoreq.8 to hydrolyze the metal alkoxides. Then, allowing the mixture to react at room temperature for a precalculated period of time for the mixture to undergo an increased in viscosity to obtain a desired pore size and surface area. The copolymerized mixture is then added to an immiscible, nonpolar solvent that has been heated to a sufficient temperature wherein the copolymerized mixture forms a solid upon the addition. The solid is recovered from the mixture, and is ready for use in an active sampling trap or activated for use in a passive sampling trap.

  5. Pecan drying with silica gel

    Energy Technology Data Exchange (ETDEWEB)

    Ghate, S.R.; Chhinnan, M.S.

    1983-07-01

    High moisture in-shell pecans were dried by keeping them in direct and indirect contact with silica gel to investigate their drying characteristics. In-shell pecans were also dried with ambient air from a controlled environment chamber and with air dehumidified by silica gel. Direct contact and dehumidified air drying seemed feasible approaches.

  6. Silica reinforced triblock copolymer gels

    DEFF Research Database (Denmark)

    Theunissen, E.; Overbergh, N.; Reynaers, H.

    2004-01-01

    The effect of silica and polymer coated silica particles as reinforcing agents on the structural and mechanical properties of polystyrene-poly(ethylene/butylene)-polystyrene (PS-PEB-PS) triblock gel has been investigated. Different types of chemically modified silica have been compared in order...

  7. Metal-silica sol-gel materials

    Science.gov (United States)

    Stiegman, Albert E. (Inventor)

    2002-01-01

    The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

  8. Separation of pharmacologically active nitrogen-containing compounds on silica gels modified with 6,10-ionene, dextran sulfate, and gold nanoparticles

    Science.gov (United States)

    Ioutsi, A. N.; Shapovalova, E. N.; Ioutsi, V. A.; Mazhuga, A. G.; Shpigun, O. A.

    2017-12-01

    New stationary phases for HPLC are obtained via layer-by-layer deposition of polyelectrolytes and studied: (1) silica gel modified layer-by-layer with 6,10-ionene and dextran sulfate (Sorbent 1); (2) silica gel twice subjected to the above modification (Sorbent 2); and (3) silica gel modified with 6,10-ionene, gold nanoparticles, and dextran sulfate (Sorbent 3). The effect the content of the organic solvent in the mobile phase and the concentration and pH of the buffer solution have on the chromatographic behavior of several pharmacologically active nitrogen-containing compounds is studied. The sorbents are stable during the process and allow the effective separation of beta-blockers, calcium channel blockers, alpha-agonists, and antihistamines. A mixture of caffeine, nadolol, tetrahydrozoline, pindolol, orphenadrine, doxylamine, carbinoxamine, and chlorphenamine is separated in 6.5 min on the silica gel modified with 6,10-ionene, gold nanoparticles, and dextran sulfate.

  9. Method of making ionic liquid mediated sol-gel sorbents

    Science.gov (United States)

    Malik, Abdul; Shearrow, Anne M.

    2017-01-31

    Ionic liquid (IL)-mediated sol-gel hybrid organic-inorganic materials present enormous potential for effective use in analytical microextraction. One obstacle to materializing this prospect arises from high viscosity of ILs significantly slowing down sol-gel reactions. A method was developed which provides phosphonium-based, pyridinium-based, and imidazolium-based IL-mediated advanced sol-gel organic-inorganic hybrid materials for capillary microextraction. Scanning electron microscopy results demonstrate that ILs can serve as porogenic agents in sol-gel reactions. IL-mediated sol-gel coatings prepared with silanol-terminated polymers provided up to 28 times higher extractions compared to analogous sol-gel coatings prepared without any IL in the sol solution. This study shows that IL-generated porous morphology alone is not enough to provide effective extraction media: careful choice of the organic polymer and the precursor with close sol-gel reactivity must be made to ensure effective chemical bonding of the organic polymer to the created sol-gel material to be able to provide the desired sorbent characteristics.

  10. Efficacy of a new tan doped sol-gel sorbent for uptake of zinc

    International Nuclear Information System (INIS)

    Khan, A.; Ahmed, S.; Riaz, M.; Mahmood, F.; Younas Khokhar, M.

    2003-01-01

    A TAN (1-(2-Thiazolylazo)-2-naphthol) doped sol gel silica sorbent (reddish colour, porous, stable, hard, non-swelling) were prepared and investigated for the removal of Zn (II) from aqueous solutions. The kinetics, adsorption isotherm, equilibration time and pH effect on the removal were studied from non competitive aqueous solution to optimize the conditions to be utilized on a large scale. Fast equilibration was observed and adsorption equilibria were reached within 30 minutes. Adsorption of zinc ions on the blank (un-doped) sol gel was found negligible. The maximum adsorption of Zn (II) ions onto the TAN doped sol-gel from single solutions were 2.33 mg/g (0.035 mmol/g). TAN doped sol gel can be regenerated through washing with a solution of 0.1 M HCl solution. The maximum regeneration value was as high as 99.0%. The TAN-doped sol gel silica is suitable at least for four adsorption-desorption cycles without experiencing considerable loss of adsorption capacity. The uptake route and the nature of the Zn-TAN complex have been discussed. (orig.)

  11. Comparative DNA isolation behaviours of silica and polymer based sorbents in batch fashion: monodisperse silica microspheres with bimodal pore size distribution as a new sorbent for DNA isolation.

    Science.gov (United States)

    Günal, Gülçin; Kip, Çiğdem; Eda Öğüt, S; İlhan, Hasan; Kibar, Güneş; Tuncel, Ali

    2018-02-01

    Monodisperse silica microspheres with bimodal pore-size distribution were proposed as a high performance sorbent for DNA isolation in batch fashion under equilibrium conditions. The proposed sorbent including both macroporous and mesoporous compartments was synthesized 5.1 μm in-size, by a "staged shape templated hydrolysis and condensation method". Hydrophilic polymer based sorbents were also obtained in the form of monodisperse-macroporous microspheres ca 5.5 μm in size, with different functionalities, by a developed "multi-stage microsuspension copolymerization" technique. The batch DNA isolation performance of proposed material was comparatively investigated using polymer based sorbents with similar morphologies. Among all sorbents tried, the best DNA isolation performance was achieved with the monodisperse silica microspheres with bimodal pore size distribution. The collocation of interconnected mesoporous and macroporous compartments within the monodisperse silica microspheres provided a high surface area and reduced the intraparticular mass transfer resistance and made easier both the adsorption and desorption of DNA. Among the polymer based sorbents, higher DNA isolation yields were achieved with the monodisperse-macroporous polymer microspheres carrying trimethoxysilyl and quaternary ammonium functionalities. However, batch DNA isolation performances of polymer based sorbents were significantly lower with respect to the silica microspheres.

  12. Silica gel matrix immobilized Chlorophyta hydrodictyon africanum ...

    African Journals Online (AJOL)

    Aghomotsegin

    2015-08-05

    Aug 5, 2015 ... The algae-silica gel adsorbent was used for batch sorption studies of a cationic dye, ... traditional methods of treating industrial effluent, these ... Author(s) agree that this article remains permanently open access under the terms of the Creative ... sodium silicate solution (v/v) and 25 mL of distilled water. With.

  13. Fluorescence metrology of silica sol-gels

    Indian Academy of Sciences (India)

    We have developed a new method for measuring in-situ the growth of the nanometre-size silica particles which lead to the formation of sol-gel glasses. This technique is based on the decay of fluorescence polarisation anisotropy due to Brownian rotation of dye molecules bound to the particles. Results to date give near ...

  14. Uptake of metal ions by a silica-based tetraphenylporphyrin sorbent

    Energy Technology Data Exchange (ETDEWEB)

    Pyrzynska, K.; Sadowska, M.; Trojanowicz, M.

    1999-09-01

    The [5-p-carboxyphenyl-10,15,20-triphenyl]porphyrin (TPP) covalently attached to aminopropyl silica gel was examined with respect to the sorption of transition metal ions. The distribution coefficients (K{sub d}) are reported for some metal ions with this new sorbent as a function of pH. It was found that in optimum pH conditions the sorption of Cu(II) and Fe(III) is much faster than that of Co(II) and Cr(III). The binding of metal ions is strongly affected by the presence of various species accelerating the complex formation. The application of porphyrin ligands for preconcentration and metal-matrix separation was also examined using complex formation in solution coupled with an anion exchange resin and column chelation procedure, e.g. sorption of metal on an anion exchanger previously loaded with tetra(4-carboxyphenyl)porphyrin.

  15. New Silica Magnetite Sorbent: The Influence of Variations of Sodium Silicate Concentrations on Silica Magnetite Character

    Science.gov (United States)

    Azmiyawati, C.; Pratiwi, P. I.; Darmawan, A.

    2018-04-01

    The adsorption capacity of an adsorbent is determined by the adsorbent and the adsorbate properties. The character of the adsorbent will play a major role in its ability to adsorb the corresponding adsorbate. Therefore, in this study we looked at the effects of variations of sodium silicate concentrations on the resulting magnetite silica adsorbent properties. The application of silica coating on the magnetite was carried out through a sol-gel process with sodium silicate and HCl precursors. Based on the characterization data obtained, it was found that the silica coating on magnetite can increase the resistance to acid leaching, increase the particle size, but decrease the magnetic properties of the magnetite. Based on Gas Sorption Analyzer (GSA) and X-ray Difraction (XRD) data it can successively be determined that increase in concentration of sodium silicate will increase the surface area and amorphous structure of the Silica Magnetie.

  16. Matrix molecularly imprinted mesoporous sol-gel sorbent for efficient solid-phase extraction of chloramphenicol from milk.

    Science.gov (United States)

    Samanidou, Victoria; Kehagia, Maria; Kabir, Abuzar; Furton, Kenneth G

    2016-03-31

    Highly selective and efficient chloramphenicol imprinted sol-gel silica based inorganic polymeric sorbent (sol-gel MIP) was synthesized via matrix imprinting approach for the extraction of chloramphenicol in milk. Chloramphenicol was used as the template molecule, 3-aminopropyltriethoxysilane (3-APTES) and triethoxyphenylsilane (TEPS) as the functional precursors, tetramethyl orthosilicate (TMOS) as the cross-linker, isopropanol as the solvent/porogen, and HCl as the sol-gel catalyst. Non-imprinted sol-gel polymer (sol-gel NIP) was synthesized under identical conditions in absence of template molecules for comparison purpose. Both synthesized materials were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and nitrogen adsorption porosimetry, which unambiguously confirmed their significant structural and morphological differences. The synthesized MIP and NIP materials were evaluated as sorbents for molecularly imprinted solid phase extraction (MISPE) of chloramphenicol in milk. The effect of critical extraction parameters (flow rate, elution solvent, sample and eluent volume, selectivity coefficient, retention capacity) was studied in terms of retention and desorption of chloramphenicol. Competition and cross reactivity tests have proved that sol-gel MIP sorbent possesses significantly higher specific retention and enrichment capacity for chloramphenicol compared to its non-imprinted analogue. The maximum imprinting factor (IF) was found as 9.7, whereas the highest adsorption capacity of chloramphenicol by sol-gel MIP was 23 mg/g. The sol-gel MIP was found to be adequately selective towards chloramphenicol to provide the necessary minimum required performance limit (MRPL) of 0.3 μg/kg set forth by European Commission after analysis by LC-MS even without requiring time consuming solvent evaporation and sample reconstitution step, often considered as an integral part in solid phase extraction work-flow. Intra and

  17. Silica scintillating materials prepared by sol-gel methods

    International Nuclear Information System (INIS)

    Werst, D.W.; Sauer, M.C. Jr.; Cromack, K.R.; Lin, Y.; Tartakovsky, E.A.; Trifunac, A.D.

    1993-01-01

    Silica was investigated as a rad-hard alternative to organic polymer hosts for organic scintillators. Silica sol-gels were prepared by hydrolysis of tetramethoxysilane in alcohol solutions. organic dyes were incorporated into the gels by dissolving in methanol at the sol stage of gel formation. The silica sol-gel matrix is very rad-hard. The radiation stability of silica scintillators prepared by this method is dye-limited. Transient radioluminescence was measured following excitation with 30 ps pulses of 20 MeV electrons

  18. Efficient CO2 sorbents based on silica foam with ultra-large mesopores

    KAUST Repository

    Qi, Genggeng; Fu, Liling; Choi, Brian Hyun; Giannelis, Emmanuel P.

    2012-01-01

    A series of high-capacity, amine impregnated sorbents based on a cost-effective silica foam with ultra-large mesopores is reported. The sorbents exhibit fast CO2 capture kinetics, high adsorption capacity (of up to 5.8 mmol g-1 under 1 atm of dry CO2), as well as good stability over multiple adsorption-desorption cycles. A simple theoretical analysis is provided relating the support structure to sorbent performance. © 2012 The Royal Society of Chemistry.

  19. Radiation effect on polystyrene deposited and grafted on silica gel

    International Nuclear Information System (INIS)

    Kusama, Y.; Udagawa, A.; Takehisa, M.

    1978-01-01

    The effect of radiation on polystyrene was studied in the presence and absence of silica gel by molecular weight measurement with gel permeation chromatography (GPC). Polystyrene crosslinked under vacuum in the absence of silica gel, but it either crosslinked or degraded by radiation, depending on the molecular weight of the polymer in the presence of silica gel. part of the deposited polymer bonded to silica gel by radiation; the G value for graft-chain formation is in the range of 0.01 to 0.1. Irradiation of polystyrene grafted on silica gel resulted in degradation of the graft chain because of the transfer of energy from silica gel. The G value for main chain scission was about 2 when graft polymer was irradiated in the absence of homopolymer. The degradation of graft polymer was suppressed when the polymer was irradiated in the presence of homopolymer, and the amount of unextractable polymer from silica gel increased with increasing irradiation. This adds evidence to the estimation that an increase in grafting percent coupled with a slight decrease in molecular weight at a later stage of radiation-induced polymerization of styrene adsorbed on slica gel is due to a secondary effect of radiation on the polymer

  20. Synthesis and application of silica gel modified with alkoxyalcohols. Alkoxyalcohol shushoku silica gel no gosei to riyo

    Energy Technology Data Exchange (ETDEWEB)

    Moriguchi, T.; Ishiguro, H.; Matsubara, Y.; Yoshihara, M.; Maeshima, T.; Ito, S. (Kinki University, Osaka (Japan). Faculty of Science and Engineering)

    1991-08-20

    Several kinds of silica gel modified by alkoxyalcohols were synthesized by refluxing and dehyration and the organic reactions were studied when these silica gels were used as the catalyst. It could be confirmed by FT-IR spectra, DTA and elementary analysis that alkoxylalcohols adhere to the surface of silica gels without any decomposition. The acetate was produced by using alkyl halides. It was found that the modified silica gels had clearly the catalytic action for the reaction with n-hexyl bromide and dibromoethane although unmodified silica gels did not show the catalytic action. The reducing reaction of carbonyl compounds was carried out. The reaction proceeded at 25 centigrade for acetophenone, cyclohexanone, 1-indanone and 2-octanone to produce the corresponding reduction products. 11 refs., 5 figs., 4 tabs.

  1. Matrix molecularly imprinted mesoporous sol–gel sorbent for efficient solid-phase extraction of chloramphenicol from milk

    International Nuclear Information System (INIS)

    Samanidou, Victoria; Kehagia, Maria; Kabir, Abuzar; Furton, Kenneth G.

    2016-01-01

    Highly selective and efficient chloramphenicol imprinted sol–gel silica based inorganic polymeric sorbent (sol–gel MIP) was synthesized via matrix imprinting approach for the extraction of chloramphenicol in milk. Chloramphenicol was used as the template molecule, 3-aminopropyltriethoxysilane (3-APTES) and triethoxyphenylsilane (TEPS) as the functional precursors, tetramethyl orthosilicate (TMOS) as the cross-linker, isopropanol as the solvent/porogen, and HCl as the sol–gel catalyst. Non-imprinted sol–gel polymer (sol–gel NIP) was synthesized under identical conditions in absence of template molecules for comparison purpose. Both synthesized materials were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and nitrogen adsorption porosimetry, which unambiguously confirmed their significant structural and morphological differences. The synthesized MIP and NIP materials were evaluated as sorbents for molecularly imprinted solid phase extraction (MISPE) of chloramphenicol in milk. The effect of critical extraction parameters (flow rate, elution solvent, sample and eluent volume, selectivity coefficient, retention capacity) was studied in terms of retention and desorption of chloramphenicol. Competition and cross reactivity tests have proved that sol–gel MIP sorbent possesses significantly higher specific retention and enrichment capacity for chloramphenicol compared to its non-imprinted analogue. The maximum imprinting factor (IF) was found as 9.7, whereas the highest adsorption capacity of chloramphenicol by sol–gel MIP was 23 mg/g. The sol–gel MIP was found to be adequately selective towards chloramphenicol to provide the necessary minimum required performance limit (MRPL) of 0.3 μg/kg set forth by European Commission after analysis by LC-MS even without requiring time consuming solvent evaporation and sample reconstitution step, often considered as an integral part in solid phase extraction work

  2. Matrix molecularly imprinted mesoporous sol–gel sorbent for efficient solid-phase extraction of chloramphenicol from milk

    Energy Technology Data Exchange (ETDEWEB)

    Samanidou, Victoria, E-mail: samanidu@chem.auth.gr [Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University of Thessaloniki (Greece); Kehagia, Maria [Laboratory of Analytical Chemistry, Department of Chemistry, Aristotle University of Thessaloniki (Greece); Kabir, Abuzar, E-mail: akabir@fiu.edu [International Forensic Research Institute, Department of Chemistry and Biochemistry, Florida International University, Miami, FL (United States); Furton, Kenneth G. [International Forensic Research Institute, Department of Chemistry and Biochemistry, Florida International University, Miami, FL (United States)

    2016-03-31

    Highly selective and efficient chloramphenicol imprinted sol–gel silica based inorganic polymeric sorbent (sol–gel MIP) was synthesized via matrix imprinting approach for the extraction of chloramphenicol in milk. Chloramphenicol was used as the template molecule, 3-aminopropyltriethoxysilane (3-APTES) and triethoxyphenylsilane (TEPS) as the functional precursors, tetramethyl orthosilicate (TMOS) as the cross-linker, isopropanol as the solvent/porogen, and HCl as the sol–gel catalyst. Non-imprinted sol–gel polymer (sol–gel NIP) was synthesized under identical conditions in absence of template molecules for comparison purpose. Both synthesized materials were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR) and nitrogen adsorption porosimetry, which unambiguously confirmed their significant structural and morphological differences. The synthesized MIP and NIP materials were evaluated as sorbents for molecularly imprinted solid phase extraction (MISPE) of chloramphenicol in milk. The effect of critical extraction parameters (flow rate, elution solvent, sample and eluent volume, selectivity coefficient, retention capacity) was studied in terms of retention and desorption of chloramphenicol. Competition and cross reactivity tests have proved that sol–gel MIP sorbent possesses significantly higher specific retention and enrichment capacity for chloramphenicol compared to its non-imprinted analogue. The maximum imprinting factor (IF) was found as 9.7, whereas the highest adsorption capacity of chloramphenicol by sol–gel MIP was 23 mg/g. The sol–gel MIP was found to be adequately selective towards chloramphenicol to provide the necessary minimum required performance limit (MRPL) of 0.3 μg/kg set forth by European Commission after analysis by LC-MS even without requiring time consuming solvent evaporation and sample reconstitution step, often considered as an integral part in solid phase extraction work

  3. Humic acid-bonded silica as a novel sorbent for solid-phase extraction of benzo[a]pyrene in edible oils

    International Nuclear Information System (INIS)

    Luo Dan; Yu Qiongwei; Yin Hongrui; Feng Yuqi

    2007-01-01

    A novel solid-phase extraction (SPE) sorbent, humic acid-bonded silica (HAS), was prepared. Humic acids (HAs) were grafted onto silica matrices via an amide linkage between humyl chloride and the amido terminus of 3-aminopropyltrimethoxysilane (APTS)-silica gel. The resulting material was characterized by Fourier transform infrared spectrometer, elemental analysis, and nitrogen adsorption analysis. This sorbent exhibits an excellent adsorption capacity for some electron-abundant analytes owing to its peculiar structure. In this paper, we choose benzo[a]pyrene (BaP) in oil as a probe to validate the adsorption capacity of the material. Thus a fast, cheap and simple SPE method with humic acid-bonded silica cartridge for edible oil clean-up, followed by high-performance liquid chromatography (HPLC) with fluorescence detection was established. The effects of experimental variables, such as washing and elution solvents, and the amount of sorbents have been studied. The recoveries of BaP in edible oils spiked at 0.2-100 μg kg -1 were in the range of 78.8-102.7% with relative standard deviations ranging between 1.3 and 9.3%; the limit of detection was -0.06 μg kg -1

  4. Determination of beryllium in water using silica gel chemically modified with aminophosphonic acid

    International Nuclear Information System (INIS)

    Zajtseva, G.N.; Strelko, V.V.

    2001-01-01

    Considered are methods of Be determination based on Be isolation from the solutions using aminophosphonic acid covalently bound on silica gel surface (APA-SiO 2 ) and subsequent photometric or atomic-absorption determination of Be in eluate ( the limit of Be determination is 0.00005 mg/l or 0.00008 mg/l, respectively). APA-SiO 2 high efficiency and a possibility of beryllium ions extraction from diluted solutions by means of sorbent small weighed portions is shown. High efficiency of the sorbent both for concentration and waters purification from beryllium is shown. Methods are tested in analysis of waste water. To assess the accuracy of the proposed methods, parallel determination of beryllium in tests by means of the additions method was carried out. The given data testify to a sufficient accuracy and reproducibility of the proposed methods [ru

  5. Preparation of an efficient humidity indicating silica gel from rice ...

    Indian Academy of Sciences (India)

    Administrator

    Department of Ceramic Engineering, National Institute of Technology, Rourkela 769 008, ... An efficient humidity indicating silica gel was prepared using rice husk ash as a raw material via ... white or colourless and shows no changes of colour.

  6. Steady-state leaching of tritiated water from silica gel

    DEFF Research Database (Denmark)

    Das, H.A.; Hou, Xiaolin

    2009-01-01

    Aqueous leaching of tritium from silica gel, loaded by absorption of water vapor, makes part of reactor de-commissioning. It is found to follow the formulation of steady-state diffusion.......Aqueous leaching of tritium from silica gel, loaded by absorption of water vapor, makes part of reactor de-commissioning. It is found to follow the formulation of steady-state diffusion....

  7. New thiamine functionalized silica microparticules as a sorbent for the removal of lead, mercury and cadmium ions in aqueous media

    Directory of Open Access Journals (Sweden)

    Deniz Sabahattin

    2017-01-01

    Full Text Available The existence of heavy metal ions in aqueous media is one of the biggest environmental pollution problems and thus the removal of heavy metals is a very important procedure. In this work, a new adsorbent was synthesized by modifying 3-aminopropyl-functionalized silica gel with thiamine (vitamin B1 and characterized. The influence of the uptake conditions, such as pH, contact time, initial feed concentration and foreign metal ions, on the binding capacity of thiamine-functionalized silica gel sorbent (M3APS were investigated. Maximum obtained adsorption capacities for Pb(II, Hg(II and Cd(II were 39.4±0.2, 30.9±0.5 and 9.54±0.4 mg g-1 M3APS, respectively, at pH 5.0. The observed selectivity of M3APS for these metal ions was the following: Pb(II > Hg(II > Cd(II. Adsorption isotherm models were also applied to the adsorption process. As a result, the Langmuir isotherm model gave the best fit for the adsorption of metal ions on M3APS. The Gibbs energy change (ΔG for the adsorption of Pb(II, Hg(II and Cd(II were calculated to predict the nature of adsorption process. Having such satisfactory adsorption results, M3APS is a potential candidate adsorbent for Pb(II and Hg(II removal from aqueous media.

  8. Quaternary ammonium-functionalized silica sorbents for the solid-phase extraction of aromatic amines under normal phase conditions.

    Science.gov (United States)

    Vidal, Lorena; Robin, Orlane; Parshintsev, Jevgeni; Mikkola, Jyri-Pekka; Riekkola, Marja-Liisa

    2013-04-12

    Quaternary ammonium-functionalized silica materials were synthesized and applied for solid-phase extraction (SPE) of aromatic amines, which are classified as priority pollutants by US Environmental Protection Agency. Hexamethylenetetramine used for silica surface modification for the first time was employed as SPE sorbent under normal phase conditions. Hexaminium-functionalized silica demonstrated excellent extraction efficiencies for o-toluidine, 4-ethylaniline and quinoline (recoveries 101-107%), while for N,N-dimethylaniline and N-isopropylaniline recoveries were from low to moderate (14-46%). In addition, the suitability of 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica as SPE sorbent was tested under normal phase conditions. The recoveries achieved for the five aromatic amines ranged from 89 to 99%. The stability of the sorbent was evaluated during and after 150 extractions. Coefficients of variation between 4.5 and 10.2% proved a high stability of the synthesized sorbent. Elution was carried out using acetonitrile in the case of hexaminium-functionalized silica and water for 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica sorbent. After the extraction the analytes were separated and detected by liquid chromatography ultraviolet detection (LC-UV). The retention mechanism of the materials was primarily based on polar hydrogen bonding and π-π interactions. Comparison made with activated silica proved the quaternary ammonium-functionalized materials to offer different selectivity and better extraction efficiencies for aromatic amines. Finally, 1-alkyl-3-(propyl-3-sulfonate) imidazolium-functionalized silica sorbent was successfully tested for the extraction of wastewater and soil samples. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. Selective solid-phase extraction of Hg(II) using silica gel surface - imprinting technique

    International Nuclear Information System (INIS)

    Zheng, H.; Geng, T.; Hu, L.

    2008-01-01

    A new ion-imprinted amino-functionalized silica gel sorbent was synthesized by surface-imprinting technique for preconcentration and separation of Hg(II) prior to its determination by inductively coupled plasma optical emission spectrometry (ICP-OES). Compared to the traditional solid sorbents and non-imprinted polymer particles, the ion-imprinted polymers (IIPs) have higher adsorption capacity and selectivity for Hg(II). The maximum static adsorption capacity of the imprinted and non-imprinted sorbent for Hg(II) was 29.89 mg g -1 and 11.21 mg g -1 , respectively. The highest selectivity coefficient for Hg(II) in the presence of Zn(II) exceeded 230. The detection limit (3σ) of the method was 0.25 μg L -1 . The relative standard deviation of the method was 2.5% for eight replicate determinations of 10 μg of Hg 2+ in 200 mL-in-volume water sample. The procedure was validated by performing the analysis of the certified river sediment sample (GBW 08603, China) using the standard addition method. The developed method was also successfully applied to the determination of trace mercury in Chinese traditional medicine and water samples with satisfactory results. (authors)

  10. Silica-Silver Nanocomposites as Regenerable Sorbents for Hg0 Removal from Flue Gases.

    Science.gov (United States)

    Cao, Tiantian; Li, Zhen; Xiong, Yong; Yang, Yue; Xu, Shengming; Bisson, Teresa; Gupta, Rajender; Xu, Zhenghe

    2017-10-17

    Silica-silver nanocomposites (Ag-SBA-15) are a novel class of multifunctional materials with potential applications as sorbents, catalysts, sensors, and disinfectants. In this work, an innovative yet simple and robust method of depositing silver nanoparticles on a mesoporous silica (SBA-15) was developed. The synthesized Ag-SBA-15 was found to achieve a complete capture of Hg 0 at temperatures up to 200 °C. Silver nanoparticles on the SBA-15 were shown to be the critical active sites for the capture of Hg 0 by the Ag-Hg 0 amalgamation mechanism. An Hg 0 capture capacity as high as 13.2 mg·g -1 was achieved by Ag(10)-SBA-15, which is much higher than that achievable by existing Ag-based sorbents and comparable with that achieved by commercial activated carbon. Even after exposure to more complex simulated flue gas flow for 1 h, the Ag(10)-SBA-15 could still achieve an Hg 0 removal efficiency as high as 91.6% with a Hg 0 capture capacity of 457.3 μg·g -1 . More importantly, the spent sorbent could be effectively regenerated and reused without noticeable performance degradation over five cycles. The excellent Hg 0 removal efficiency combined with a simple synthesis procedure, strong tolerance to complex flue gas environment, great thermal stability, and outstanding regeneration capability make the Ag-SBA-15 a promising sorbent for practical applications to Hg 0 capture from coal-fired flue gases.

  11. Silica Sol-Gel Entrapment of the Enzyme Chloro peroxidase

    International Nuclear Information System (INIS)

    Le, T.; Chan, S.; Ebaid, B.; Sommerhalter, M.

    2015-01-01

    The enzyme chloro peroxidase (CPO) was immobilized in silica sol-gel beads prepared from tetramethoxysilane. The average pore diameter of the silica host structure (∼3 nm) was smaller than the globular CPO diameter (∼6 nm) and the enzyme remained entrapped after sol-gel maturation. The catalytic performance of the entrapped enzyme was assessed via the pyrogallol peroxidation reaction. Sol-gel beads loaded with 4 μg CPO per mL sol solution reached 9-12% relative activity compared to free CPO in solution. Enzyme kinetic analysis revealed a decrease in K_cat but no changes in K_M or K_I . Product release or enzyme damage might thus limit catalytic performance. Yet circular dichroism and visible absorption spectra of transparent CPO sol-gel sheets did not indicate enzyme damage. Activity decline due to methanol exposure was shown to be reversible in solution. To improve catalytic performance the sol-gel protocol was modified. The incorporation of 5, 20, or 40% methyltrimethoxysilane resulted in more brittle sol-gel beads but the catalytic performance increased to 14% relative to free CPO in solution. The use of more acidic casting buffers (ph 4.5 or 5.5 instead of 6.5) resulted in a more porous silica host reaching up to 18% relative activity

  12. The Influence of Microgravity on Silica Sol-Gel Formation

    Science.gov (United States)

    Sibille, L.; Smith, D. D.; Cronise, R.; Hunt, A. J.; Wolfe, D. B.; Snow, L. A.; Oldenberg, S.; Halas, N.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    We discuss space-flight experiments involving the growth of silica particles and gels. The effect of microgravity on the growth of silica particles via the sol-gel route is profound. In four different recipes spanning a large range of the parameter space that typically produces silica nanoparticles in unit-gravity, low-density gel structures were instead formed in microgravity. The particles that did form were generally smaller and more polydisperse than those grown on the ground. These observations suggest that microgravity reduces the particle growth rate, allowing unincorporated species to form aggregates and ultimately gel. Hence microgravity favors the formation of more rarefied structures, providing a bias towards diffusion-limited cluster-cluster aggregation. These results further suggest that in unit gravity, fluid flows and sedimentation can significantly perturb sol-gel substructures prior to gelation and these deleterious perturbations may be "frozen" into the resulting microstructure. Hence, sol-gel pores may be expected to be smaller, more uniform, and less rough when formed in microgravity.

  13. Tributyl phosphate removal from reprocessing off-gas streams using a selected sorbent

    International Nuclear Information System (INIS)

    Parker, G.B.

    1980-01-01

    Laboratory experiments used small laboratory-scale columns packed with selected sorbent materials to remove tributyl phosphate (TBP) and iodine at conditions approaching those in actual reprocessing off-gas streams. The sorbent materials for TBP removal were placed upstream of iodine sorbent materials to protect the iodine sorbent from the deleterious effects of TBP. Methyl iodide in an airstream containing 30% TBP in normal paraffin hydrocarbons (NPH) and water vapor was metered to two packed columns of sorbents simultaneously (in parallel). One column contained a segment of 8-in. x 14-in. mesh alumina sorbent for TBP removal, the other did not. The measure of the effectiveness of TBP sorbent materials for TBP removal was determined by comparing the iodine retention of the iodine sorbent materials in the two parallel columns. Results from an 18 wt % Ag substituted mordenite iodine sorbent indicated that the iodine retention capacity of the sorbent was reduced 60% by the TBP and that the column containing iodine sorbent material protected by the alumina TBP sorbent retained 30 times more iodine than the column without TBP sorbent. TBP concentration was up to 500 mg/m 3 . Similar experiments using a 7 wt % Ag impregnated silica gel indicated that the TBP vapor had little effect on the iodine retention of the silica gel material. The stoichiometric maximum amount of iodine was retained by the silica gel material. Further experiments were conducted assessing the effects of NO 2 on iodine retention of this 7 wt % Ag sorbent. After the two columns were loaded with iodine in the presence of TBP (in NPH), one column was subjected to 2 vol % NO 2 in air. From visual comparison of the two columns, it appeared that the NO 2 regenerated the silica gel iodine sorbent and that iodine was washed off the silica gel iodine sorbent leaving the sorbent in the original state

  14. Fluorescence metrology of silica sol–gels – The effect of D2O and ...

    Indian Academy of Sciences (India)

    Administrator

    industrial quality control and helping fundamental research. ... Of all the possible syntheses, sodium silicate (i.e. water glass) production of silica gel, ... fine silica gel powders used in many applications (e.g. chromatography, toothpaste etc).

  15. Crystallization of mixed rare earth (didymium) molybdates in silica gel

    Indian Academy of Sciences (India)

    Experiments on the growth of mixed rare earth (didymium—a combination of La, Nd, Pr and Sm) molybdates in silica gel medium are reported. The optimum conditions conducive for the growth of these crystals are described and discussed. Concentration programming is reported to enhance the size of crystals by two-fold; ...

  16. Tough ceramic coatings: Carbon nanotube reinforced silica sol-gel

    Science.gov (United States)

    López, A. J.; Rico, A.; Rodríguez, J.; Rams, J.

    2010-08-01

    Silica coatings reinforced with carbon nanotubes were produced via sol-gel route using two mixing techniques of the sol-gel precursors, mechanical and ultrasonic mixing, and dip-coating as deposition process on magnesium alloy substrates. Effective incorporation and distribution of 0.1 wt.% of carbon nanotubes in the amorphous silica matrix of the coatings were achieved using both techniques. Fabrication procedure determines the morphological aspects of the coating. Only mechanical mixing process produced coatings dense and free of defects. Nanoindentation technique was used to examine the influence of the fabrication process in the mechanical features of the final coatings, i.e. indentation fracture toughness, Young's modulus and hardness. A maximum toughening effect of about 24% was achieved in silica coatings reinforced with carbon nanotubes produced by the mechanical mixing route. Scanning electron microscopy investigation revealed that the toughening of these reinforced coatings was mainly due to bridging effect of the reinforcement.

  17. Poly(ethyleneimine) infused and functionalized Torlon®-silica hollow fiber sorbents for post-combustion CO2 capture

    KAUST Repository

    Li, Fuyue Stephanie

    2014-03-01

    Organic-inorganic hybrid materials functionalized with amine-containing reagents are emerging as an important class of materials for capturing carbon dioxide from flue gas. Polymeric silica hollow fiber sorbents are fabricated through the proven dry-jet/wet-quench spinning process. In our study, a new technique for functionalizing polymeric silica hollow fiber sorbents with poly(ethyleneimine), followed by a post-spinning infusion step was studied. This two step process introduces a sufficient amount of poly(ethyleneimine) to the polymeric silica hybrid material support to improve the CO2 sorption capacity due to the added amine groups. The poly(ethyleneimine) infused and functionalized hollow fiber sorbents are also characterized by a thermal gravimetric analyzer (TGA) to assess their CO2 sorption capacities. © 2014 Elsevier Ltd. All rights reserved.

  18. The increase in pH during aging of porous sol-gel silica spheres

    NARCIS (Netherlands)

    Titulaer, M.K.; Kegel, W.K.; Jansen, J.B.H.; Geus, John W.

    1994-01-01

    The increase in pH in the hydrothermal fluid is studied after hydrothermal aging of porous silica gel spheres of 1–3 mm diameter. The porous silica spheres are formed by the sol-gel process from a supersaturated silica solution. The increase of the pH of the hydrothermal solution affects the silica

  19. Study of silica sol-gel materials for sensor development

    Science.gov (United States)

    Lei, Qiong

    Silica sol-gel is a transparent, highly porous silicon oxide glass made at room temperature by sol-gel process. The name of silica sol-gel comes from the observable physical phase transition from liquid sol to solid gel during its preparation. Silica sol-gel is chemically inert, thermally stable, and photostable, it can be fabricated into different desired shapes during or after gelation, and its porous structure allows encapsulation of guest molecules either before or after gelation while still retaining their functions and sensitivities to surrounding environments. All those distinctive features make silica sol-gel ideal for sensor development. Study of guest-host interactions in silica sol-gel is important for silica-based sensor development, because it helps to tailor local environments inside sol-gel matrix so that higher guest loading, longer shelf-life, higher sensitivity and faster response of silica gel based sensors could be achieved. We focused on pore surface modification of two different types of silica sol-gel by post-grafting method, and construction of stable silica hydrogel-like thin films for sensor development. By monitoring the mobility and photostability of rhodamine 6G (R6G) molecules in silica alcogel thin films through single molecule spectroscopy (SMS), the guest-host interactions altered by post-synthesis grafting were examined. While physical confinement remains the major factor that controls mobility in modified alcogels, both R6G mobility and photostability register discernable changes after surface charges are respectively reversed and neutralized by aminopropyltriethoxysilane (APTS) and methyltriethoxysilane (MTES) grafting. The change in R6G photostability was found to be more sensitive to surface grafting than that of mobility. In addition, silica film modification by 0.4% APTS is as efficient as that by pure MTES in lowering R6G photostability, which suggests that surface charge reversal is more effective than charge neutralization

  20. Characterization of alkali silica reaction gels using Raman spectroscopy

    International Nuclear Information System (INIS)

    Balachandran, C.; Muñoz, J.F.; Arnold, T.

    2017-01-01

    The ability of Raman spectroscopy to characterize amorphous materials makes this technique ideal to study alkali silica reaction (ASR) gels. The structure of several synthetic ASR gels was thoroughly characterized using Raman Spectroscopy. The results were validated with additional techniques such as Fourier transmission infrared spectroscopy, X-ray powder diffraction and thermogravimetric analysis. The Raman spectra were found to have two broad bands in the 800 to 1200 cm −1 range and the 400 to 700 cm −1 range indicating the amorphous nature of the gel. Important information regarding the silicate polymerization was deduced from both of these spectral regions. An increase in alkali content of the gels caused a depolymerization in the silicate framework which manifested in the Raman spectra as a gradual shift of predominant peaks in both regions. The trends in silicate depolymerization were in agreement with results from a NMR spectroscopy study on similar synthetic ASR gels.

  1. Effect of gamma radiation on silica gel, (3)

    International Nuclear Information System (INIS)

    Ogura, Hajime; Nakazato, Chiyoko; Kondo, Masaharu; Sawai, Teruko; Sawai, Takeshi.

    1979-01-01

    The γ-irradiation of silica gel degassed for 24 h above 400 0 C produces visible color center (lambda sub(max) = 530 nm). The color center instantly disappears on exposure to H 2 at room temperature and irreversible adsorption of H 2 is concurrently observed. On the basis that color center is attributed to the positive hole due to substitutional impurity of Al in silica matrix, the yield of color center and H 2 adsorption have been investigated as a function of Al content in silica gel deliberatly prepared by us from silicon tetrachloride to contain Al in the range of 10 -3 -- 5w/0. Absorbance at 530 nm, A 530 , due to color center as well as the amount of H 2 adsorbed, (H 2 )sub(ads), increase with the Al content in the matrix. A 530 /(H 2 )sub(ads) is 1.0 x 10 6 (O.D. unit g/mol) in these gels. This ratio is seen almost same with two samples of gel commercially available. By assuming that 1 mol of H 2 reacts with 2 mol of positive hole, the extinction coefficient of color center at 530 nm is evaluated as 1.0 x 10 6 (g/mol.cm). (author)

  2. Bio sorption process for uranium (VI) by using algae-yeast-silica gel composite adsorbent

    International Nuclear Information System (INIS)

    Turkozu, D. A.; Aytas, S.

    2006-01-01

    Many yeast, algae, bacteria and various aquatic flora are known to be capable of concentrating metal species from dilute aqueous solution. Many researcher have found that non-living biomaterials can be used to accumulate metal ions from environment. In recent studies, mainly two process are used in biosorption experiments. These are the use of free cells and the use of immobilized cells on a solid support. A variety of inert supports have been used to immobilize biomaterials either by adsorption or physical entrapment. This uptake is often considerable and frequently selective, and occurs via a variety of mechanisms including active transport, ion exchange or complexation, and adsorption or inorganic precipitation. Biosorbent may be used as an ion exchange material. Adsorption occurs through interaction of the metal ions with functional groups that are found in the cell wall biopolymers of either living or dead organisms. In this study, the algae-yeast-silica gel composite adsorbent was tested for its ability to recover U(VI) from diluted aqueous solutions. Macro marine algae (Jania rubens.), yeast (Saccharomyces cerevisiae) and silica gel were used to prepare composite adsorbent. The ability of the composite biosorbent to adsorb uranium (VI) from aqueous solution has been studied at different optimized conditions of pH, concentration of U(VI), temperature, contact time and matrix ion effect was also investigated. The adsorption patterns of uranium on the composite biosorbent were investigated by the Langmuir, Freundlich and Dubinin-Radushkhevic isotherms. The thermodynamic parameters such as variation of enthalpy ΔH, variation of entropy ΔS and variation of Gibbs free energy ΔG were calculated. The results suggested that the macro algae-yeast-silica gel composite sorbent is suitable as a new biosorbent material for removal of uranium ions from aqueous solutions

  3. Chromatographic separation of metal cations on silica gel chemically modified with a polymeric derivative of diaza-18-crown-6

    International Nuclear Information System (INIS)

    Basyuk, V.A.

    1991-01-01

    Sorbent on the basis of γ-aminopropyl silica gel, containing chemically grafted polymer derivatives of diaza-18-crown-6, has been synthesized. Retaining of certain metal cations when acid mobile phases are used is studied. Acetate buffer solution, 0.005% aqueous solution of acetic acid and 10 mM aqueous solution of oxalic acid were used as mobile phases. Rare earth cations (including Sr 2+ ones) are weakly retained when any mobile phase is used. Retention of VO 2+ cations is the strongest one

  4. Preparation of silica by sol-gel method using formamide

    Directory of Open Access Journals (Sweden)

    R.F.S. Lenza

    2001-07-01

    Full Text Available In this work we obtained microporous and mesoporous silica gels by sol-gel processing. Tetraethylortosilicate (TEOS was used as precursor. Nitric acid and hydrofluoric acid were used as catalysts. In order to study the affect of formamide as drying additive, we used a molar ratio alkoxide/formamide of 1/1. The performance of formamide in obtaining crack-free gels was evaluated through monolithicity measurements. The structural evolution occurring in the interconnected network of the gels during thermal treatment was monitored by Fourier transform infrared spectroscopy (FTIR, shrinkage and density measurements and nitrogen gas sorption. We noted that in the presence of formamide, the Si-O-Si bonds are stronger and belong to a more cross-linked structure. The samples obtained in the presence of formamide have larger pore volume and its pore structure is in the range of mesoporosity. The samples obtained without additive are microporous. Formamide allowed the preparation of crack-free silica gels stabilized at high temperatures.

  5. Poly(ethyleneimine) infused and functionalized Torlon®-silica hollow fiber sorbents for post-combustion CO2 capture

    KAUST Repository

    Li, Fuyue Stephanie; Labreche, Ying; Lively, Ryan P.; Lee, Jong Suk; Jones, Christopher W.; Koros, William J.

    2014-01-01

    -jet/wet-quench spinning process. In our study, a new technique for functionalizing polymeric silica hollow fiber sorbents with poly(ethyleneimine), followed by a post-spinning infusion step was studied. This two step process introduces a sufficient amount of poly

  6. Epoxy-silica hybrids by nonaqueous sol-gel process

    Czech Academy of Sciences Publication Activity Database

    Ponyrko, Sergii; Kobera, Libor; Brus, Jiří; Matějka, Libor

    2013-01-01

    Roč. 54, č. 23 (2013), s. 6271-6282 ISSN 0032-3861 R&D Projects: GA ČR GAP108/12/1459 Grant - others:AV ČR(CZ) M200500903 Institutional support: RVO:61389013 Keywords : epoxy-silica hybrid * nonaqueous sol-gel process * gelation Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.766, year: 2013

  7. Hydrogen sulfide removal from hot coal gas by various mesoporous silica supported Mn2O3 sorbents

    International Nuclear Information System (INIS)

    Zhang, Z.F.; Liu, B.S.; Wang, F.; Wang, W.S.; Xia, C.; Zheng, S.; Amin, R.

    2014-01-01

    Graphical abstract: - Highlights: • Mn 2 O 3 /KIT-1 presented the best desulfurization performance at 600–850 °C. • High sulfur capacity of Mn 2 O 3 /KIT-1 correlated closely with 3-D channel of KIT-1. • Desulfurization character depended strongly on framework structure of sorbents. • High steam content suppressed greatly the occurrence of sulfidation reaction. - Abstract: A series of 50 wt% Mn 2 O 3 sorbents was prepared using various mesoporous silica, MCM-41, HMS, and KIT-1 as support. The influence of textural parameters of mesoporous silica, especially type of channel on the desulfurization performance of Mn 2 O 3 sorbents was investigated at 600–850 °C using hot coal gas containing 0.33 vol.% H 2 S. The fresh and used sorbents were characterized by means of N 2 -adsorption, x-ray diffraction (XRD), high resolution transmission microscopy (HRTEM) and H 2 temperature- programmed reduction (H 2 -TPR) techniques. The results confirmed that the manganese oxide was dispersed highly in regular pore channel of the mesoporous supports due to high surface area. Compared with the Mn 2 O 3 /diatomite, all mesoporous silica supported Mn 2 O 3 sorbents exhibited high breakthrough sulfur capacity and a sharp deactivation rate after the breakthrough point. Compared to Mn 2 O 3 /MCM-41 and Mn 2 O 3 /HMS sorbent, the Mn 2 O 3 /KIT-1 showed better desulfurization performance because of the 3D wormhole-like channel. The high sulfur capacity of the Mn 2 O 3 /KIT-1 sorbent was maintained during the eight consecutive desulfurization-regeneration cycles. The Mn 2 O 3 /KIT-1 still presented high desulfurization activity when hot coal gas contained low steam (<5%)

  8. Removal mechanism of tritium by variously pretreated silica gel

    International Nuclear Information System (INIS)

    Nakashima, M.; Tachikawa, E.; Saeki, M.; Aratono, Y.

    1981-01-01

    Removal mechanisms of HTO from variously pretreated and non-pretreated silica gel columns were investigated with pulse-loading with tritiated water vapor. With non-pretreated silica gel, the HTO physisorbed on the upper part of the column comes into contact with surface hydroxyl groups while passing downward the column, so that in each equilibration a part of the tritium is incorporated into hydroxyl groups by H/T isotopic exchange reactions. With the silica gel pretreated at a temperature below 400 0 C, most of tritium in the applied HTO is easily incorporated into surface hydroxyl groups in the upper part of the column either by H/T isotopic exchange reactions or by rehydration of the dehydrated surface (siloxyl linkage). In the pretreatment above 400 0 C, essentially all the tritium is trapped by siloxyl groups of various stabilities. The ease of rehydration of siloxyl groups by applied HTO depends on their stabilities, which, in turn, depend on the pretreatment temperature. As a general trend, treatment at higher temperature promotes annealing of the constrained siloxyl groups and thus the rate of rehydration becomes slower. (author)

  9. Silica Modified with Polyaniline as a Potential Sorbent for Matrix Solid Phase Dispersion (MSPD) and Dispersive Solid Phase Extraction (d-SPE) of Plant Samples

    Science.gov (United States)

    Sowa, Ireneusz; Wójciak-Kosior, Magdalena; Strzemski, Maciej; Sawicki, Jan; Staniak, Michał; Dresler, Sławomir; Szwerc, Wojciech; Mołdoch, Jarosław; Latalski, Michał

    2018-01-01

    Polyaniline (PANI) is one of the best known conductive polymers with multiple applications. Recently, it was also used in separation techniques, mostly as a component of composites for solid-phase microextraction (SPME). In the present paper, sorbent obtained by in situ polymerization of aniline directly on silica gel particles (Si-PANI) was used for dispersive solid phase extraction (d-SPE) and matrix solid–phase extraction (MSPD). The efficiency of both techniques was evaluated with the use of high performance liquid chromatography with diode array detection (HPLC-DAD) quantitative analysis. The quality of the sorbent was verified by Raman spectroscopy and microscopy combined with automated procedure using computer image analysis. For extraction experiments, triterpenes were chosen as model compounds. The optimal conditions were as follows: protonated Si-PANI impregnated with water, 160/1 sorbent/analyte ratio, 3 min of extraction time, 4 min of desorption time and methanolic solution of ammonia for elution of analytes. The proposed procedure was successfully used for pretreatment of plant samples. PMID:29565297

  10. Silica Modified with Polyaniline as a Potential Sorbent for Matrix Solid Phase Dispersion (MSPD and Dispersive Solid Phase Extraction (d-SPE of Plant Samples

    Directory of Open Access Journals (Sweden)

    Ireneusz Sowa

    2018-03-01

    Full Text Available Polyaniline (PANI is one of the best known conductive polymers with multiple applications. Recently, it was also used in separation techniques, mostly as a component of composites for solid-phase microextraction (SPME. In the present paper, sorbent obtained by in situ polymerization of aniline directly on silica gel particles (Si-PANI was used for dispersive solid phase extraction (d-SPE and matrix solid–phase extraction (MSPD. The efficiency of both techniques was evaluated with the use of high performance liquid chromatography with diode array detection (HPLC-DAD quantitative analysis. The quality of the sorbent was verified by Raman spectroscopy and microscopy combined with automated procedure using computer image analysis. For extraction experiments, triterpenes were chosen as model compounds. The optimal conditions were as follows: protonated Si-PANI impregnated with water, 160/1 sorbent/analyte ratio, 3 min of extraction time, 4 min of desorption time and methanolic solution of ammonia for elution of analytes. The proposed procedure was successfully used for pretreatment of plant samples.

  11. SAXS study of silica sols, gels and glasses obtained by the sol gel process

    International Nuclear Information System (INIS)

    Santos, D.I. dos; Aegerter, M.A.

    1988-01-01

    Systematic SAXS studies have been performed at the LURE Synchrotron, Orsay, using an intense beam of point like cross-section to obtain information about the sol -> humid gel -> dried gel -> silica glass transformation. The intensity curves have been analysed in term of power law in log-log plots, whose exponent is related to mass and surface fractal dimensions of the structure. It was found that almost all phases present fractal structures and for the case of basic gels, is of hierarchical nature. The aerogels are formed by a dense matrix, with a smooth surface and exhibit a very narrow auto-similarity range that gives a mass fractal dimension. (author) [pt

  12. The Effect of Various Acids to the Gelation Process to the Silica Gel Characteristic Using Organic Silica

    Science.gov (United States)

    Rahman, NA; Widiyastuti, W.; Sigit, D.; Ajiza, M.; Sujana, W.

    2018-01-01

    Bagasse ash is solid waste of cane sugar industry which contain of silica more than 51%. Some previous study of silica gel from bagasse ash have been conducted often and been applied. This study concerns about the effect of various acid used in the process of gelation to the characteristic of silica gel produced. Then, this silica gel will be used as adsorbent. As that, the silica gel must fulfill the requirements of adsorbent, as have good pores characteristics, fit in mesoporous size so that adsorbent diffusion process is not disturbed. A fitted pores size of silica gel can be prepared by managing acid concentration used. The effect of acid, organic acid (tartaric acid) and inorganic acid (hydrochloric acid), is investigated in detail. The acid is added into sodium silicate solution in that the gel is formed, the pores structures can be investigated with BET, the crystal form is analyzed with XRD and the pore structure is analyzed visually with SEM. By managing the acid concentration added, it gets the effect of acid to the pore structure of silica gel. The bigger concentration is, the bigger the pore’s size of silica gel produced.

  13. Kinetics Study of Gas Pollutant Adsorption and Thermal Desorption on Silica Gel

    Directory of Open Access Journals (Sweden)

    Rong A

    2017-06-01

    Full Text Available Silica gel is a typical porous desiccant material. Its adsorption performance for gaseous air pollutants was investigated to determine its potential contribution to reducing such pollutants. Three gaseous air pollutants, toluene, carbon dioxide, and methane, were investigated in this paper. A thermogravimetric analyzer was used to obtain the equilibrium adsorption capacity of gases on single silica gel particles. The silica gel adsorption capacity for toluene is much higher than that for carbon dioxide and methane. To understand gas pollutant thermal desorption from silica gel, the thermogravimetric analysis of toluene desorption was conducted with 609 ppm toluene vapor at 313 K, 323 K, and 333 K. The overall regeneration rate of silica gel was strongly dependent on temperature and the enthalpy of desorption. The gas pollutant adsorption performance and thermal desorption on silica gel material may be used to estimate the operating and design parameters for gas pollutant adsorption by desiccant wheels.

  14. All-silica nanofluidic devices for DNA-analysis fabricated by imprint of sol-gel silica with silicon stamp

    DEFF Research Database (Denmark)

    Mikkelsen, Morten Bo Lindholm; Letailleur, Alban A; Søndergård, Elin

    2011-01-01

    We present a simple and cheap method for fabrication of silica nanofluidic devices for single-molecule studies. By imprinting sol-gel materials with a multi-level stamp comprising micro- and nanofeatures, channels of different depth are produced in a single process step. Calcination of the imprin......We present a simple and cheap method for fabrication of silica nanofluidic devices for single-molecule studies. By imprinting sol-gel materials with a multi-level stamp comprising micro- and nanofeatures, channels of different depth are produced in a single process step. Calcination...... of the imprinted hybrid sol-gel material produces purely inorganic silica, which has very low autofluorescence and can be fusion bonded to a glass lid. Compared to top-down processing of fused silica or silicon substrates, imprint of sol-gel silica enables fabrication of high-quality nanofluidic devices without...

  15. Electrochemical redox reactions in solvated silica sol-gel glass

    International Nuclear Information System (INIS)

    Opallo, M.

    2002-01-01

    The studies of electrochemical redox reactions in solvated silica sol-gel glass were reviewed. The methodology of the experiments with emphasis on the direct preparation of the solid electrolyte and the application ultra microelectrodes was described. Generally, the level of the electrochemical signal is not much below that observed in liquid electrolyte. The current depends on time elapsed after gelation, namely the longer time, the smaller current. The differences between electrochemical behaviour of the redox couples in monoliths and thin layers were described. (author)

  16. NMR of mercury in porous coal and silica gel

    International Nuclear Information System (INIS)

    Kasperovich, V.S.; Charnaya, E.V.; Tien, C.; Wur, C.S.

    2003-01-01

    Temperature dependences of the integral intensity and NMR signals Knight shift in 199 Hg nuclei are measured for liquid and solid mercury introduced into the porous coal and silica gel. The decrease in the crystallization completion temperature and small temperature hysteresis (from 4 up to 9 K) between melting and crystallization are identified. Mercury melting temperature in pores coincided with melting temperature of the bulk mercury. NMR signal from crystalline mercury under conditions of limited geometry was observed for the first time. It is ascertained that Knight shift for mercury in the pores both in liquid and crystalline phases is lesser than for the bulk mercury [ru

  17. Solvent cleanup using base-treated silica gel solid adsorbent

    International Nuclear Information System (INIS)

    Tallent, O.K.; Mailen, J.C.; Pannell, K.D.

    1984-06-01

    A solvent cleanup method using silica gel columns treated with either sodium hydroxide (NaOH) or lithium hydroxide (LiOH) has been investigated. Its effectiveness compares favorably with that of traditional wash methods. After treatment with NaOH solution, the gels adsorb HNO 3 , dibutyl phosphate (DBP), UO 2 2+ , Pu 4+ , various metal-ion fission products, and other species from the solvent. Adsorption mechanisms include neutralization, hydrolysis, polymerization, and precipitation, depending on the species adsorbed. Sodium dibutyl phosphate, which partially distributes to the solvent from the gels, can be stripped with water; the stripping coefficient ranges from 280 to 540. Adsorption rates are diffusion controlled such that temperature effects are relatively small. Recycle of the gels is achieved either by an aqueous elution and recycle sequence or by a thermal treatment method, which may be preferable. Potential advantages of this solvent cleanup method are that (1) some operational problems are avoided and (2) the amount of NaNO 3 waste generated per metric ton of nuclear fuel reprocessed would be reduced significantly. 19 references, 6 figures, 12 tables

  18. Spherical silica particles decorated with graphene oxide nanosheets as a new sorbent in inorganic trace analysis

    International Nuclear Information System (INIS)

    Sitko, Rafal; Zawisza, Beata; Talik, Ewa; Janik, Paulina; Osoba, Grzegorz; Feist, Barbara; Malicka, Ewa

    2014-01-01

    Highlights: • Graphene oxide (GO) covalently bonded to the spherical silica. • Very stable sorbent for SPE of metal ions. • Excellent contact with solution due to the softness and flexibility of GO nanosheets. • Several adsorption–elution cycles without any loss of adsorptive properties. • High adsorption capacity due to the wrinkled structure of GO nanosheets. - Abstract: Graphene oxide (GO) is a novel material with excellent adsorptive properties. However, the very small particles of GO can cause serious problems is solid-phase extraction (SPE) such as the high pressure in SPE system and the adsorbent loss through pores of frit. These problems can be overcome by covalently binding GO nanosheets to a support. In this paper, GO was covalently bonded to spherical silica by coupling the amino groups of spherical aminosilica and the carboxyl groups of GO (GO@SiO 2 ). The successful immobilization of GO nanosheets on the aminosilica was confirmed by scanning electron microscopy and X-ray photoelectron spectroscopy. The spherical particle covered by GO with crumpled silk wave-like carbon sheets are an ideal sorbent for SPE of metal ions. The wrinkled structure of the coating results in large surface area and a high extractive capacity. The adsorption bath experiment shows that Cu(II) and Pb(II) can be quantitatively adsorbed at pH 5.5 with maximum adsorption capacity of 6.0 and 13.6 mg g −1 , respectively. Such features of GO nanosheets as softness and flexibility allow achieving excellent contact with analyzed solution in flow-rate conditions. In consequence, the metal ions can be quantitatively preconcentrated from high volume of aqueous samples with excellent flow-rate. SPE column is very stable and several adsorption–elution cycles can be performed without any loss of adsorptive properties. The GO@SiO 2 was used for analysis of various water samples by flame atomic absorption spectrometry with excellent enrichment factors (200–250) and detection

  19. Spherical silica particles decorated with graphene oxide nanosheets as a new sorbent in inorganic trace analysis

    Energy Technology Data Exchange (ETDEWEB)

    Sitko, Rafal, E-mail: rafal.sitko@us.edu.pl [University of Silesia, Institute of Chemistry, ul. Szkolna 9, 40-006 Katowice (Poland); Zawisza, Beata [University of Silesia, Institute of Chemistry, ul. Szkolna 9, 40-006 Katowice (Poland); Talik, Ewa [University of Silesia, Institute of Physics, ul. Uniwersytecka 4, 40-007 Katowice (Poland); Janik, Paulina; Osoba, Grzegorz; Feist, Barbara; Malicka, Ewa [University of Silesia, Institute of Chemistry, ul. Szkolna 9, 40-006 Katowice (Poland)

    2014-06-27

    Highlights: • Graphene oxide (GO) covalently bonded to the spherical silica. • Very stable sorbent for SPE of metal ions. • Excellent contact with solution due to the softness and flexibility of GO nanosheets. • Several adsorption–elution cycles without any loss of adsorptive properties. • High adsorption capacity due to the wrinkled structure of GO nanosheets. - Abstract: Graphene oxide (GO) is a novel material with excellent adsorptive properties. However, the very small particles of GO can cause serious problems is solid-phase extraction (SPE) such as the high pressure in SPE system and the adsorbent loss through pores of frit. These problems can be overcome by covalently binding GO nanosheets to a support. In this paper, GO was covalently bonded to spherical silica by coupling the amino groups of spherical aminosilica and the carboxyl groups of GO (GO@SiO{sub 2}). The successful immobilization of GO nanosheets on the aminosilica was confirmed by scanning electron microscopy and X-ray photoelectron spectroscopy. The spherical particle covered by GO with crumpled silk wave-like carbon sheets are an ideal sorbent for SPE of metal ions. The wrinkled structure of the coating results in large surface area and a high extractive capacity. The adsorption bath experiment shows that Cu(II) and Pb(II) can be quantitatively adsorbed at pH 5.5 with maximum adsorption capacity of 6.0 and 13.6 mg g{sup −1}, respectively. Such features of GO nanosheets as softness and flexibility allow achieving excellent contact with analyzed solution in flow-rate conditions. In consequence, the metal ions can be quantitatively preconcentrated from high volume of aqueous samples with excellent flow-rate. SPE column is very stable and several adsorption–elution cycles can be performed without any loss of adsorptive properties. The GO@SiO{sub 2} was used for analysis of various water samples by flame atomic absorption spectrometry with excellent enrichment factors (200–250) and

  20. A silica sol-gel design strategy for nanostructured metallic materials

    NARCIS (Netherlands)

    Warren, S.C.; Perkins, M.R.; Adams, A.M.; Kamperman, M.M.G.

    2012-01-01

    Batteries, fuel cells and solar cells, among many other high-current-density devices, could benefit from the precise meso- to macroscopic structure control afforded by the silica sol–gel process. The porous materials made by silica sol–gel chemistry are typically insulators, however, which has

  1. Sampling tritiated water vapor from the atmosphere by an active system using silica gel

    Energy Technology Data Exchange (ETDEWEB)

    Herranz, M. [Department of Nuclear Engineering and Fluid Mechanics, E.T.S.I. de Bilbao, University of the Basque Country (UPV/EHU), Alameda de Urquijo, s/n 48013 Bilbao (Spain); Alegria, N., E-mail: natalia.alegria@ehu.es [Department of Nuclear Engineering and Fluid Mechanics, E.T.S.I. de Bilbao, University of the Basque Country (UPV/EHU), Alameda de Urquijo, s/n 48013 Bilbao (Spain); Idoeta, R.; Legarda, F. [Department of Nuclear Engineering and Fluid Mechanics, E.T.S.I. de Bilbao, University of the Basque Country (UPV/EHU), Alameda de Urquijo, s/n 48013 Bilbao (Spain)

    2011-11-15

    Among the different methods used to collect the tritiated water vapor (HTO) contained in the atmosphere, one of the most worldwide used is its collection using an air pump, which forces the air to pass through a dry silica gel trap. The silica gel is then distilled to remove the water collected, which is measured in a liquid scintillation counting system. In this paper, an analysis of the water collection efficiency of the silica gel has been done as a function of the temperatures involved, the dimensions of the pipe driving the air into the silica gel traps, the air volume passing through the trap and the flow rates used. Among the obtained conclusions, it can be pointed out that placing the traps inside a cooled container, the amount of silica gel needed to collect all the water contained in the air passing through these traps can be estimated using a weather forecast and a psychometric chart. To do this, and as thermal equilibrium between incoming and open air should be established, a suitable design of the sampling system is proposed. - Highlights: > To recollect the atmosphere air tritiated water vapor, an active system was used. > The system is an air pump and three traps with silica gel connected by a rubber pipe. > The silica gel retention depends on the meteorological conditions and the flow rate. > The amount of water collected and the mass of silica gel need were calculated, F.

  2. Smectic liquid crystals in anisotropic colloidal silica gels

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Dennis [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Borthwick, Matthew A [Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Leheny, Robert L [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States)

    2004-05-19

    We report x-ray scattering studies of the smectic liquid crystal octylcyano-biphenol (8CB) confined by strained colloidal silica gels. The gels, comprised of aerosil particles, possess an anisotropic structure that stabilizes long-range nematic order in the liquid crystal while introducing random field effects that disrupt the smectic transition. The short-range smectic correlations that form within this environment are inconsistent with the presence of a topologically ordered state predicted for 3D random field XY systems and are quantitatively like the correlations of smectics confined by isotropic gels. Detailed analysis reveals that the quenched disorder suppresses the anisotropic scaling of the smectic correlation lengths observed in the pure liquid crystal. These results and additional measurements of the smectic-A to smectic-C transition in 4-n-pentylphenylthiol-4'-n-octyloxybenzoate (8barS5) indicate that the observed smectic behaviour is dictated by random fields coupling directly to the smectic order while fields coupling to the nematic director play a subordinate role.

  3. Regenerated silica gel as stationary phase on vacuum column chromatography to purify temulawak’s extracts

    International Nuclear Information System (INIS)

    Cahyono, Bambang; Maduwu, Ratna Dewi; Widayat,; Suzery, Meiny

    2015-01-01

    Commercial silica gel only used once by many researchers and affected high cost for purification process, also less support the green chemistry program. This research focused in regeneration silica gel that used purification of temulawak’s extracts (Curcuma xanthorrhiza Roxb) by vacuum column chromatography. Sample extracts (contains 10.1195±0.5971% of curcuminoids) was purified by vacuum column chromatography (pressure: 45 kPa, column: 100mm on length and 16mm on diameter). Ethanol 96% and acetone were compared as eluent. The amount of solvent and yield of curcuminoids used as indicator purification. The silica gel was regenerated with heating in 600°C for 8 hours The silica gels were analyzed by IR spectroscopy and X-ray diffraction. Furthermore, regenerated silica gel was used as the stationary phase in vacuum column chromatography under the same conditions with the previous purification. All the purification experiments were performed in three repetitions. Based on regression equation, y=0.132x+0.0011 (r 2 =0.9997) the yield of curcuminoids on purified products using ethanol as the eluent was improved 4.26% (to 14.3724±0.5749%) and by acetone was improved 3,03% (to 13.1450 ±0.6318%). The IR spectrum of both silica gel showed the same vibration profile and also there were three crystallinity peaks missing on its X-ray diffraction. Regenerated silica gel has the same performance with new silica gel in purification of temulawak’s extract: by ethanol has increased 4.08% (14.1947±0.7415%) and 2.93% (13.0447±0.4822) by acetone. In addition, all purification products showed similar TLC profiles. Purification using regenerated silica gel as the adsorbent on vacuum column chromatography has exactly same potential with the new silica gel

  4. Regenerated silica gel as stationary phase on vacuum column chromatography to purify temulawak’s extracts

    Energy Technology Data Exchange (ETDEWEB)

    Cahyono, Bambang; Maduwu, Ratna Dewi; Widayat,; Suzery, Meiny [Organic Chemistry Laboratory, Departement of Chemistry, Diponegoro University Jln Prof. Soedharto SH, Tembalang, Semarang 50275, Indonesia Tel / Fax: (024) 7460058 (Indonesia)

    2015-12-29

    Commercial silica gel only used once by many researchers and affected high cost for purification process, also less support the green chemistry program. This research focused in regeneration silica gel that used purification of temulawak’s extracts (Curcuma xanthorrhiza Roxb) by vacuum column chromatography. Sample extracts (contains 10.1195±0.5971% of curcuminoids) was purified by vacuum column chromatography (pressure: 45 kPa, column: 100mm on length and 16mm on diameter). Ethanol 96% and acetone were compared as eluent. The amount of solvent and yield of curcuminoids used as indicator purification. The silica gel was regenerated with heating in 600°C for 8 hours The silica gels were analyzed by IR spectroscopy and X-ray diffraction. Furthermore, regenerated silica gel was used as the stationary phase in vacuum column chromatography under the same conditions with the previous purification. All the purification experiments were performed in three repetitions. Based on regression equation, y=0.132x+0.0011 (r{sup 2}=0.9997) the yield of curcuminoids on purified products using ethanol as the eluent was improved 4.26% (to 14.3724±0.5749%) and by acetone was improved 3,03% (to 13.1450 ±0.6318%). The IR spectrum of both silica gel showed the same vibration profile and also there were three crystallinity peaks missing on its X-ray diffraction. Regenerated silica gel has the same performance with new silica gel in purification of temulawak’s extract: by ethanol has increased 4.08% (14.1947±0.7415%) and 2.93% (13.0447±0.4822) by acetone. In addition, all purification products showed similar TLC profiles. Purification using regenerated silica gel as the adsorbent on vacuum column chromatography has exactly same potential with the new silica gel.

  5. Extraction of metal ions using chemically modified silica gel: a PIXE analysis.

    Science.gov (United States)

    Jal, P K; Dutta, R K; Sudarshan, M; Saha, A; Bhattacharyya, S N; Chintalapudi, S N; K Mishra, B

    2001-08-30

    Organic ligand with carboxyhydrazide functional group was immobilised on the surface of silica gel and the metal binding capacity of the ligand-embedded silica was investigated. The functional group was covalently bonded to the silica matrix through a spacer of methylene groups by sequential reactions of silica gel with dibromobutane, malonic ester and hydrazine in different media. Surface area value of the modified silica was determined. The changes in surface area were correlated with the structural change of the silica surface due to chemical modifications. A mixture solution of metal ions [K(I),Cr(III),Co(II),Ni(II),Cu(II),Zn(II),Hg(II) and U(VI)] was treated with the ligand-embedded silica in 10(-3) M aqueous solution. The measurement of metal extraction capacity of the silica based ligand was done by multielemental analysis of the metal complexes thus formed by using Proton Induced X-ray Emission (PIXE) technique.

  6. Separation, preconcentration and determination of silver ion from water samples using silica gel modified with 2,4,6-trimorpholino-1,3,5-triazin

    International Nuclear Information System (INIS)

    Madrakian, Tayyebeh; Afkhami, Abbas; Zolfigol, Mohammad Ali; Solgi, Mohammad

    2006-01-01

    A new modified silica gel using 2,4,6-trimorpholino-1,3,5-triazin was used for separation, preconcentration and determination of silver ion in natural water by atomic absorption spectrometry (AAS). This new bonded silica gel was used as an effective sorbent for the solid-phase extraction (SPE) of silver ion from aqueous solutions. Experimental conditions for effective adsorption of trace levels of silver ion were optimized with respect to different experimental parameters in column process. Common coexisting ions did not interfere with the separation and determination of silver at pH 3.5 so that silver ion completely adsorbed on the column. The preconcentration factor is 130 (1 mL elution volume for a 130 mL sample volume). The relative standard deviation (R.S.D.) under optimum conditions is 3.03% (n = 5). The accuracy of the method was estimated by using spring and tap water samples that were spiked with different amounts of silver ion. The adsorption isotherm of silver ion was obtained. The capacity of the sorbent at optimum conditions has been found to be 384 μg of silver per gram of sorbent

  7. Sol-Gel processing of silica nanoparticles and their applications.

    Science.gov (United States)

    Singh, Lok P; Bhattacharyya, Sriman K; Kumar, Rahul; Mishra, Geetika; Sharma, Usha; Singh, Garima; Ahalawat, Saurabh

    2014-11-06

    Recently, silica nanoparticles (SNPs) have drawn widespread attention due to their applications in many emerging areas because of their tailorable morphology. During the last decade, remarkable efforts have been made on the investigations for novel processing methodologies to prepare SNPs, resulting in better control of the size, shape, porosity and significant improvements in the physio-chemical properties. A number of techniques available for preparing SNPs namely, flame spray pyrolysis, chemical vapour deposition, micro-emulsion, ball milling, sol-gel etc. have resulted, a number of publications. Among these, preparation by sol-gel has been the focus of research as the synthesis is straightforward, scalable and controllable. Therefore, this review focuses on the recent progress in the field of synthesis of SNPs exhibiting ordered mesoporous structure, their distribution pattern, morphological attributes and applications. The mesoporous silica nanoparticles (MSNPs) with good dispersion, varying morphology, narrow size distribution and homogeneous porous structure have been successfully prepared using organic and inorganic templates. The soft template assisted synthesis using surfactants for obtaining desirable shapes, pores, morphology and mechanisms proposed has been reviewed. Apart from single template, double and mixed surfactants, electrolytes, polymers etc. as templates have also been intensively discussed. The influence of reaction conditions such as temperature, pH, concentration of reagents, drying techniques, solvents, precursor, aging time etc. have also been deliberated. These MSNPs are suitable for a variety of applications viz., in the drug delivery systems, high performance liquid chromatography (HPLC), biosensors, cosmetics as well as construction materials. The applications of these SNPs have also been briefly summarized. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Exploring encapsulation mechanism of DNA and mononucleotides in sol-gel derived silica.

    Science.gov (United States)

    Kapusuz, Derya; Durucan, Caner

    2017-07-01

    The encapsulation mechanism of DNA in sol-gel derived silica has been explored in order to elucidate the effect of DNA conformation on encapsulation and to identify the nature of chemical/physical interaction of DNA with silica during and after sol-gel transition. In this respect, double stranded DNA and dAMP (2'-deoxyadenosine 5'-monophosphate) were encapsulated in silica using an alkoxide-based sol-gel route. Biomolecule-encapsulating gels have been characterized using UV-Vis, 29 Si NMR, FTIR spectroscopy and gas adsorption (BET) to investigate chemical interactions of biomolecules with the porous silica network and to examine the extent of sol-gel reactions upon encapsulation. Ethidium bromide intercalation and leach out tests showed that helix conformation of DNA was preserved after encapsulation. For both biomolecules, high water-to-alkoxide ratio promoted water-producing condensation and prevented alcoholic denaturation. NMR and FTIR analyses confirmed high hydraulic reactivity (water adsorption) for more silanol groups-containing DNA and dAMP encapsulated gels than plain silica gel. No chemical binding/interaction occurred between biomolecules and silica network. DNA and dAMP encapsulated silica gelled faster than plain silica due to basic nature of DNA or dAMP containing buffer solutions. DNA was not released from silica gels to aqueous environment up to 9 days. The chemical association between DNA/dAMP and silica host was through phosphate groups and molecular water attached to silanols, acting as a barrier around biomolecules. The helix morphology was found not to be essential for such interaction. BET analyses showed that interconnected, inkbottle-shaped mesoporous silica network was condensed around DNA and dAMP molecules.

  9. Sol-gel niobia sorbent with a positively charged octadecyl ligand providing enhanced enrichment of nucleotides and organophosphorus pesticides in capillary microextraction for online HPLC analysis.

    Science.gov (United States)

    Kesani, Sheshanka; Malik, Abdul

    2018-04-01

    A niobia-based sol-gel organic-inorganic hybrid sorbent carrying a positively charged C 18 ligand (Nb 2 O 5 -C 18 (+ve)) was synthesized to achieve enhanced enrichment capability in capillary microextraction of organophosphorus compounds (which include organophosphorus pesticides and nucleotides) before their online analysis by high-performance liquid chromatography. The sorbent was designed to simultaneously provide three different types of molecular level interactions: electrostatic, Lewis acid-base, and van der Waals interactions. To understand relative contributions of various molecular level analyte-sorbent interactions in the extraction process, two other sol-gel niobia sorbents were also created: (a) a purely inorganic sol-gel niobia sorbent (Nb 2 O 5 ) and (b) an organic-inorganic hybrid sol-gel niobia sorbent carrying an electrically neutral-bonded octadecyl ligand (Nb 2 O 5 -C 18 ). The extraction efficiency of the created sol-gel niobia sorbent (Nb 2 O 5 -C 18 (+ve)) was compared with that of analogously designed and synthesized titania-based sol-gel sorbent (TiO 2 -C 18 (+ve)), taking into consideration that titania-based sorbents present state-of-the-art extraction media for organophosphorus compounds. In capillary microextraction with high-performance liquid chromatography analysis, Nb 2 O 5 -C 18 (+ve) had shown 40-50% higher specific extraction values (a measure of extraction efficiency) over that of TiO 2 -C 18 (+ve). Compared to TiO 2 -C 18 (+ve), Nb 2 O 5 -C 18 (+ve) also provided superior analyte desorption efficiency (96 vs. 90%) during the online release of the extracted organophosphorus pesticides from the sorbent coating in the capillary microextraction capillary to the chromatographic column using reversed-phase high-performance liquid chromatography mobile phase. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Characterization of a humic gel synthesized from an activated epoxy silica gel

    International Nuclear Information System (INIS)

    Barbot, C.; Pieri, J.; Durand, J.P.; Goudard, F.; Czerwinski, K.; Vial, M.; Buckau, G.; Kim, J.I.; Moulin, V.

    2002-01-01

    Purified humic acid has been covalently bound on activated epoxy silica gel particles. Determination of physical properties and chemical properties was conducted in order to characterize the material at different stages of the preparation. FTIR spectra and the PEC of the surface bound humic acid is very similar to that of humic acid starting material. This shows that the humic acid was not deteriorated during the surface binding process. This humic gel can be used as an analogue for sediment associated humic acid, with the advantage that covalently bound humic acid does not desorb, and thus allows for simple species separation between non-complexed and humic bound metal ions in batch and column experiments

  11. Synthesis of Titania-Silica Materials by Sol-Gel

    Directory of Open Access Journals (Sweden)

    Rubia F. S. Lenza

    2002-10-01

    Full Text Available In this work TiO2-SiO2 glasses containing as much as 20 mol % of TiO2 were prepared via sol-gel process using titanium and silicon alkoxides, in the presence of chlorine, in the form of titanium tetrachloride or HCl. The gels were heat-treated until 800 °C. X-ray diffraction and Fourier transform infrared spectroscopy were used to understand the structural properties of TiO2-SiO2 oxides calcined at different temperatures and to evaluate the homogeneity of these materials. The degree of the compactness of the silica network is inferred from the frequency of the asymmetric stretching vibrations of Si-O-Si bonds. Formation of Si-O-Ti bridges, as monitored by the intensity of characteristic 945 cm-1 ¾ 960 cm-1 vibration, is particularly prominent if the method of basic two-step prehydrolysis of silicon alkoxide, addition of titanium alkoxide and completion of hydrolysis was used.

  12. Fractal dimensions of silica gels generated using reactive molecular dynamics simulations

    International Nuclear Information System (INIS)

    Bhattacharya, Sudin; Kieffer, John

    2005-01-01

    We have used molecular dynamics simulations based on a three-body potential with charge transfer to generate nanoporous silica aerogels. Care was taken to reproduce the sol-gel condensation reaction that forms the gel backbone as realistically as possible and to thereby produce credible gel structures. The self-similarity of aerogel structures was investigated by evaluating their fractal dimension from geometric correlations. For comparison, we have also generated porous silica glasses by rupturing dense silica and computed their fractal dimension. The fractal dimension of the porous silica structures was found to be process dependent. Finally, we have determined that the effect of supercritical drying on the fractal nature of condensed silica gels is not appreciable

  13. Spherical silica particles decorated with graphene oxide nanosheets as a new sorbent in inorganic trace analysis.

    Science.gov (United States)

    Sitko, Rafal; Zawisza, Beata; Talik, Ewa; Janik, Paulina; Osoba, Grzegorz; Feist, Barbara; Malicka, Ewa

    2014-06-27

    Graphene oxide (GO) is a novel material with excellent adsorptive properties. However, the very small particles of GO can cause serious problems is solid-phase extraction (SPE) such as the high pressure in SPE system and the adsorbent loss through pores of frit. These problems can be overcome by covalently binding GO nanosheets to a support. In this paper, GO was covalently bonded to spherical silica by coupling the amino groups of spherical aminosilica and the carboxyl groups of GO (GO@SiO2). The successful immobilization of GO nanosheets on the aminosilica was confirmed by scanning electron microscopy and X-ray photoelectron spectroscopy. The spherical particle covered by GO with crumpled silk wave-like carbon sheets are an ideal sorbent for SPE of metal ions. The wrinkled structure of the coating results in large surface area and a high extractive capacity. The adsorption bath experiment shows that Cu(II) and Pb(II) can be quantitatively adsorbed at pH 5.5 with maximum adsorption capacity of 6.0 and 13.6 mg g(-1), respectively. Such features of GO nanosheets as softness and flexibility allow achieving excellent contact with analyzed solution in flow-rate conditions. In consequence, the metal ions can be quantitatively preconcentrated from high volume of aqueous samples with excellent flow-rate. SPE column is very stable and several adsorption-elution cycles can be performed without any loss of adsorptive properties. The GO@SiO2 was used for analysis of various water samples by flame atomic absorption spectrometry with excellent enrichment factors (200-250) and detection limits (0.084 and 0.27 ng mL(-1) for Cu(II) and Pb(II), respectively). Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Influence of ultrasonic frequency on the regeneration of silica gel by applying high-intensity ultrasound

    International Nuclear Information System (INIS)

    Zhang Weijiang; Yao Ye; Wang Rongshun

    2010-01-01

    Ultrasonic frequency is the key parameter considered in ultrasonic applications. In order to provide a basic knowledge about the influence of ultrasonic frequency on the regeneration of silica gel assisted by power ultrasound, the experiments about silica gel regeneration under the radiation of constant-power (60 W) ultrasound with different frequencies (i.e., 23, 27, and 38 kHz) and that without ultrasound were carried out at different regeneration temperatures (i.e., 35, 45, 55, and 65 deg. C). The experimental results showed that the lower frequency was beneficial for the application of power ultrasound in the regeneration of silica gel. The fact was theoretically explained by the ultrasonic power attenuation model which indicates that the ultrasound of lower frequency will lead to more uniform energy distribution and hence achieve higher efficiency of utilization. Meanwhile, the effect of ultrasonic frequency on silica gel regeneration would be influenced by the regeneration temperature and the moisture ratio in silica gel. As investigated in this study, the effect of ultrasonic frequency on the regeneration would be more significant at the lower regeneration temperature or at the higher moisture ratio in silica gel. In addition, the mean regeneration speed model of silica gel dependent of the regeneration temperature and the ultrasonic frequency was established according to the experimental data.

  15. Analysis of separation quality of scandium-46 and titanium using silica gel column

    International Nuclear Information System (INIS)

    Muhamad Basit Febrian; Yanuar Setiadi; Duyeh Setiawan; Titin Sri Mulyati; Nana Suherman

    2015-01-01

    In this study, quality test of scandium and titanium mixture separation system using a silica gel column has been conducted. This system will be used in the separation of medical radioisotopes of 47 Sc from TiO 2 enriched targets. 20 mg of TiO 2 and 5 mg of Sc 2 O 3 dissolved using 0.5 mL of 50% HF solvent with gentle heating at 60°C - 80°C for 1 hour then 4.5 mL H 2 O was added. Sc and Ti mixture is separated by passing it through a column of silica gel. In the determination of scandium released from silica gel, Sc-46 radiotracer was used. Only 51.60 ± 4.5% of 5 mg of scandium could be retained in the silica gel column. From 51.60% of absorbed scandium in the column, 98.29 ± 3.4% were eluted with 5 mL of H 2 O eluent. During elution of scandium from silica gel column, 2.81 grams of 20 mg of titanium came apart as breakthrough. In determination of recovery of titanium from silica gel, 51.76 ± 5.5% of the 20 mg Ti can be recovered from silica gel column using 5M HCl eluent, whereas remaining Ti were eluted using 40 ml of HCl 5M. Based on those result, it can be concluded that there are still titanium portion in scandium after the separation using a silica gel column. Further purification step using fresh silica gel column, can separate escaped titanium from scandium. (author)

  16. Radiation hardening in sol-gel derived Er3+-doped silica glasses

    International Nuclear Information System (INIS)

    Hari Babu, B.; León Pichel, Mónica; Ollier, Nadège; El Hamzaoui, Hicham; Bigot, Laurent; Savelii, Inna; Bouazaoui, Mohamed; Poumellec, Bertrand; Lancry, Matthieu; Ibarra, Angel

    2015-01-01

    The aim of the present paper is to report the effect of radiation on the Er 3+ -doped sol-gel silica glasses. A possible application of these sol-gel glasses could be their use in harsh radiation environments. The sol-gel glasses are fabricated by densification of erbium salt-soaked nanoporous silica xerogels through polymeric sol-gel technique. The radiation-induced attenuation of Er 3+ -doped sol-gel silica is found to increase with erbium content. Electron paramagnetic resonance studies reveal the presence of E′ δ point defects. This happens in the sol-gel aluminum-silica glass after an exposure to γ-rays (kGy) and in sol-gel silica glass after an exposure to electrons (MGy). The concentration levels of these point defects are much lower in γ-ray irradiated sol-gel silica glasses. When the samples are co-doped with Al, the exposure to γ-ray radiation causes a possible reduction of the erbium valence from Er 3+ to Er 2+ ions. This process occurs in association with the formation of aluminum oxygen hole centers and different intrinsic point defects

  17. Sol–gel-based silver nanoparticles-doped silica – Polydiphenylamine nanocomposite for micro-solid-phase extraction

    Energy Technology Data Exchange (ETDEWEB)

    Bagheri, Habib, E-mail: bagheri@sharif.edu; Banihashemi, Solmaz

    2015-07-30

    A nanocomposite of silica-polydiphenylamine doped with silver nanoparticles (Ag–SiO{sub 2}-PDPA) was successfully synthesized by the sol–gel process. For its preparation, PDPA was mixed with butanethiol capped Ag nanoparticles (NPs) and added to the silica sol solution. The Ag NPs were stabilized as a result of their adsorption on the SiO{sub 2} spheres. The surface characteristic of nanocomposite was investigated using scanning electron microscopy (SEM). In this work the Ag–SiO{sub 2}-PDPA nanocomposite was employed as an efficient sorbent for micro-solid-phase extraction (μ-SPE) of some selected pesticides. An amount of 15 mg of the prepared sorbent was used to extract and determine the representatives from organophosphorous, organochlorine and aryloxyphenoxy propionic acids from aqueous samples. After the implementation of extraction process, the analytes were desorbed by methanol and determined using gas chromatography–mass spectrometry (GC–MS). Important parameters influencing the extraction and desorption processes such as pH of sample solution, salting out effect, type and volume of the desorption solvent, the sample loading and eluting flow rates along with the sample volume were experimentally optimized. Limits of detection (LODs) and the limits of quantification (LOQs) were in the range of 0.02–0.05 μg L{sup −1} and 0.1–0.2 μg L{sup −1}, respectively, using time scheduled selected ion monitoring (SIM) mode. The relative standard deviation percent (RSD %) with four replicates was in the range of 6–10%. The applicability of the developed method was examined by analyzing different environmental water samples and the relative recovery (RR %) values for the spiked water samples were found to be in the range of 86–103%. - Highlights: • A sol–gel-based silver nanoparticles doped silica-polydiphenylamine nanocomposite was synthesized. • The sorbent was applied to micro-solid-phase extraction of some selected pesticides in water

  18. Synthesis and characterization of silica gel from siliceous sands of southern Tunisia

    Directory of Open Access Journals (Sweden)

    Ali Sdiri

    2014-09-01

    Full Text Available The present work aimed to achieve valorization of Albian sands for the preparation of sodium silicates that are commonly used as a precursor to prepare silica gel. A siliceous sand sample was mixed with sodium carbonate and heated at a high temperature (1060 °C to prepare sodium silicates. The sodium silicates were dissolved in distilled water to obtain high quality sodium silicate solution. Hydrochloric acid was then slowly added to the hydrated sodium silicates to obtain silica gel. The collected raw siliceous sands, as well as the prepared silica gels, were characterized by different techniques, such as X-ray fluorescence (XRF, X-ray diffraction (XRD, scanning electron microscopy (SEM and thermal analysis (DSC. XRF confirmed that the detrital sand deposits of southern Tunisia contain high amounts of silica, with content ranging from 88.8% to 97.5%. The internal porosity varied between 17% and 22%, and the specific surface area was less than 5 m2/g. After the treatment described above, it was observed that the porosity of the obtained silica gel reached 57% and the specific surface area exceeded 340 m2/g. Nitrogen adsorption isotherms showed that the prepared silica gels are microporous and mesoporous materials with high adsorption capacities. These results suggest that the obtained silica gels are promising materials for numerous environmental applications.

  19. Evaluation of ionic liquids supported on silica as a sorbent for fully automated online solid-phase extraction with LC-MS determination of sulfonamides in bovine milk samples.

    Science.gov (United States)

    da Silva, Meire Ribeiro; Mauro Lanças, Fernando

    2018-03-10

    Sulfonamides are antibiotics widely used in the treatment of diseases in dairy cattle. However, their indiscriminate use for disease control may lead to their presence in tissues and milk and their determination requires a sample preparation step as part of an analytical approach. Among the several sample preparation techniques available, those based upon the use of sorptive materials have been widely employed. Recently, the application of ionic liquids immobilized on silica surfaces or polymeric materials has been evaluated for such an application. This manuscript addresses the evaluation of silica-based ionic liquid obtained by a sol-gel synthesis process by basic catalysis as sorbent for online solid-phase extraction with liquid chromatography and electrospray ionization time-of-flight mass spectrometry for sulfonamides determination. Infrared vibrational spectroscopy confirmed the presence of the ionic liquid on the silica surface, suggesting that the ionic liquid was anchored on to the silica surface. Other sorbents varying the ionic liquid alkyl chain were also synthesized and evaluated by off-line solid-phase extraction in the sulfonamide extraction. As the length of the alkyl chain increased, the amount of extracted sulfonamides decreased, possibly due to a decrease in the electrostatic interaction caused by the reduction in the polarity, as well as the presence of a hexafluorophosphate anion that increases the hydrophobic character of the material. The use of 1-butyl-3-methylimidazolium hexafluorophosphate as a selective ionic liquid sorbent enabled the isolation and sulfonamide preconcentration in bovine milk by online solid-phase extraction with liquid chromatography and electrospray ionization time-of-flight mass spectrometry. The limit of quantification for the method developed was 5-7, 5 μg/mL, with extraction recoveries ranging between 74 and 93% and intra- and interassay between 1.5-12.5 and 2.3-13.1, respectively. © 2018 WILEY-VCH Verlag Gmb

  20. Chemical modification of silica gel with synthesized Schiff base hydrazone derivative and application for preconcentration and separation of U(VI) ions from aqueous solutions

    International Nuclear Information System (INIS)

    Gamze Karayel Incili; Gul Asiye Aycik

    2014-01-01

    Schiff base hydrazone derivative (HL) sorbent was synthesized according to the literature to be used in the adsorption and preconcentration of U(VI) ions from aqueous solution and it was exposed to immobilization, and new solid support material was obtained. For this purpose, Schiff base hydrazone derivative (HL) was chemically bonded to silica gel surface immobilized 3-aminopropyl trimethoxysilane, then analyzed by Fourier transform infrared, Brunauer-Emmett-Teller, scanning electron microscopy and elemental analysis. The influence of the solution pH, amount of sorbent, contact time, temperature, foreign ion effect and initial U(VI) concentration was investigated. The maximum U(VI) uptake capacity was found to be 8.46 mg/g. (author)

  1. Thermal and Hydrothermal Treatment of Silica Gels as Solid Stationary Phases in Gas Chromatography

    Directory of Open Access Journals (Sweden)

    Ashraf Yehia El-Naggar

    2013-01-01

    Full Text Available Silica gel was prepared and treated thermally and hydrothermally and was characterized as solid stationary phase in gas chromatography. The characteristics have been evaluated in terms of polarity, selectivity, and separation efficiencies. These parameters were used to assess the outer silica surface contributions and the degree of surface deactivation brought about by different treatment techniques. The parent silica elutes the paraffinic hydrocarbons with high efficiency of separation and elutes aromatic hydrocarbons with nearly good separation and has bad separation of alcohols. The calcined silica at 500°C and 1000°C has a pronounced effect on the separation of aromatic hydrocarbons compared with the parent silica and hydrothermal treatment of silica. With respect to alcohols separation, the obtained bad separations using treated and untreated silica reflect the little effect of the thermal and hydrothermal treatment on the silica surface deactivation.

  2. Zeolite - a possible substitute of silica gel in spectrophotometric determination of uranium?

    International Nuclear Information System (INIS)

    Foeldesova, M; Dillinger, P.

    2006-01-01

    Zeolites sorption abilities differ from the ones of the silica gel, which is normally used for uranium determination by spectrophotometric method. The difference is obvious mainly in the case of zeolites chemically modified with 1 or 2 mol/L NaOH solution. Absorbances measured using these zeolites on an radioactive water samples were 4 to 4.2 times bigger than the ones with silica gel. This avoids a use of one universal calibration curve for experimental data evaluation. Within delivered experimental data only a calibration curve for silica gel was provided. Its application to zeolites caused substantial misinterpretation of the results. Calculational construction of individual calibration curves made at this work shaw, that zeolites have a potential to replace the silica gel. This possibility is necessary to confirm by more experiments. Better sorption abilities of the modified zeolites would be utilized to reduce the lower limit for uranium determination by spectrophotometric method. (authors)

  3. Uranyl adsorption kinetics within silica gel: dependence on flow velocity and concentration

    Science.gov (United States)

    Dodd, Brandon M.; Tepper, Gary

    2017-09-01

    Trace quantities of a uranyl dissolved in water were measured using a simple optical method. A dilute solution of uranium nitrate dissolved in water was forced through nanoporous silica gel at fixed and controlled water flow rates. The uranyl ions deposited and accumulated within the silica gel and the uranyl fluorescence within the silica gel was monitored as a function of time using a light emitting diode as the excitation source and a photomultiplier tube detector. It was shown that the response time of the fluorescence output signal at a particular volumetric flow rate or average liquid velocity through the silica gel can be used to quantify the concentration of uranium in water. The response time as a function of concentration decreased with increasing flow velocity.

  4. Morphology studies on gas hydrates interacting with silica gel

    Energy Technology Data Exchange (ETDEWEB)

    Beltran, J.; Servio, P. [McGill Univ., Montreal, PQ (Canada). Dept. of Chemical Engineering

    2008-07-01

    Clathrate hydrates or gas hydrates are non-stoichiometric, crystalline compounds that form when small molecules come in contact with water at certain temperatures and pressures. Natural gas hydrates are found in the ocean bottom and in permafrost regions. It is thought that the amount of energy stored in natural hydrates is at least twice that of all other fossil fuels combined. In addition, trapping carbon dioxide as a hydrate in the bottom of the ocean has been suggested as an alternative means of reducing atmospheric carbon dioxide levels. Naturally occurring clathrates are found in close interaction with fine grained particles of very small mean pore diameters. Even though an increasing amount of hydrate equilibrium data for small diameter porous media has become available, the morphological behavior of hydrates subject to such conditions is yet to be explored. This paper presented a study that visually examined hydrate formation and decomposition of gas hydrates while interacting with fine grains of silica gel. The study showed still frames from high-resolution video recordings for hydrate formation and decomposition. The paper discussed the experiment including the apparatus as well as the results of hydrate formation and hydrate dissociation. This study enabled for the first time to observe clathrate morphology while hydrates interacted closely with fine grain particles with small mean pore diameters. 9 refs., 8 figs.

  5. Influence of organic solvents on interfacial water at surfaces of silica gel and partially silylated fumed silica

    International Nuclear Information System (INIS)

    Turov, V.V.; Gun'ko, V.M.; Tsapko, M.D.; Bogatyrev, V.M.; Skubiszewska-Zieba, J.; Leboda, R.; Ryczkowski, J.

    2004-01-01

    The effects of organic solvents (dimethylsulfoxide-d 6 (DMSO-d 6 ), chloroform-d, acetone-d 6 , and acetonitrile-d 3 ) on the properties of interfacial water at surfaces of silica gel Si-40 and partially silylated fumed silica A-380 were studied by means of the 1 H NMR spectroscopy with freezing-out of adsorbed water at 180 1 H NMR investigations were also analysed on the basis of the structural characteristics of silicas and quantum chemical calculations of the chemical shifts δ H and solvent effects. DMSO-d 6 and acetonitrile-d 3 are poorly miscible with water in silica gel pores in contrast to the bulk liquids. DMSO-d 6 and chloroform-d affect the structure of the interfacial water weaker than acetone-d 6 and acetonitrile-d 3 at amounts of liquids greater than the pore volume. Acetone-d 6 and acetonitrile-d 3 can displace water from pores under this condition. The chemical shift of protons in water adsorbed on silica gel is 3.5-6.5 ppm, which corresponds to the formation of two to four hydrogen bonds per molecule. Water adsorbed on partially silylated fumed silica has two 1 H NMR signals at 5 and 1.1-1.7 ppm related to different structures (droplets and small clusters) of the interfacial water

  6. Miniaturized solid-phase extraction of macrolide antibiotics in honey and bovine milk using mesoporous MCM-41 silica as sorbent.

    Science.gov (United States)

    Du, Li-Jing; Yi, Ling; Ye, Li-Hong; Chen, Yu-Bo; Cao, Jun; Peng, Li-Qing; Shi, Yu-Ting; Wang, Qiu-Yan; Hu, Yu-Han

    2018-02-16

    A simple and effective method of miniaturized solid-phase extraction (mini-SPE) was developed for the simultaneous purification and enrichment of macrolide antibiotics (MACs) (i.e. azithromycin, clarithromycin, erythromycin, lincomycin and roxithromycin) from honey and skim milk. Mesoporous MCM-41 silica was synthesized and used as sorbent in mini-SPE. Several key parameters affecting the performance of mini-SPE procedure were thoroughly investigated, including sorbent materials, amount of sorbent and elution solvents. Under the optimized condition, satisfactory linearity (r 2  > 0.99), acceptable precision (RSDs, 0.3-7.1%), high sensitivity (limit of detection in the range of 0.01-0.76 μg/kg), and good recoveries (83.21-105.34%) were obtained. With distinct advantages of simplicity, reliability and minimal sample requirement, the proposed mini-SPE procedure coupled with ultrahigh performance liquid chromatography and quadrupole time-of-flight tandem mass spectrometry could become an alternative tool to analyze the residues of MACs in complex food matrixes. Copyright © 2018 Elsevier B.V. All rights reserved.

  7. Analysis of the retention of water vapor on silica gel; Analisis de la retencion del vapor de agua en silica gel

    Energy Technology Data Exchange (ETDEWEB)

    Herranz, M.; Pinilla, J. L.; Alegria, N.; Idoeta, R.; Legarda, F.

    2011-07-01

    Among the various sampling systems tritium content in the atmosphere as water vapor, one of the most basic and, therefore, of widespread use in the environmental field, is the retention on silica gel. However, the behavior of the collection efficiency of silica gel under varying conditions of air temperature and relative humidity makes it difficult to define the amount of this necessary for proper completion of sampling, especially in situations of prolonged sampling. This paper presents partial results obtained in a study on the analysis of these efficiencies under normal conditions of sampling. (Author)

  8. Physicochemical properties of silica gel coated with a thin layer of polyaniline (PANI) and its application in non-suppressed ion chromatography.

    Science.gov (United States)

    Sowa, Ireneusz; Kocjan, Ryszard; Wójciak-Kosior, Magdalena; Swieboda, Ryszard; Zajdel, Dominika; Hajnos, Mieczysław

    2013-10-15

    Physicochemical properties of a new sorbent and its potential application in non-suppressed ion chromatography (IC) have been investigated. The sorbent was obtained in a process of covering silica gel particles with a film of polyaniline (PANI). The properties of silica modified with polyaniline such as particle size, porosity, average quantity of polyaniline covering carrier and density of sorbent were determined. In our study the following methods were used: microscopic analysis, laser diffraction technique, combustion analysis, mercury porosimetry and helium pycnometry. Column with the newly obtained packing was used for the separation of inorganic anions. Optimized chromatographic system was successfully employed for analysis of iodide and bromide in selected pharmaceutical products (Bochnia salt and Iwonicz salt) applied in chronic respiratory disease. Analysis was carried out using 0.1M solution of HCl in mixture of methanol/water (50:50v/v) as a mobile phase; the flow rate was 0.3 mL min(-1), temperature was 24°C and λ=210 nm. Validation parameters such as correlation coefficient, RSD values, recovery, detection and quantification limits were found to be satisfactory. Copyright © 2013 Elsevier B.V. All rights reserved.

  9. The Role Seemingly of Amorphous Silica Gel Layers in Chiral Separations by Planar Chromatography

    Directory of Open Access Journals (Sweden)

    Teresa Kowalska

    2007-12-01

    Full Text Available In planar chromatography, silica gel appears as the most frequently used adsorbent. Its preference as planar chromatographic stationary phase is due to its high specific surface area (ca. 700 m2 g-1 and relatively simple active sites (silanol groups, Si-OH. The high specific surface area of silica gel and a high density of coverage of its surface with the silanol active sites contribute jointly to an excellent separation performance of this adsorbent. In our experiments on chiral separation of the enantiomer pairs by planar chromatography, contradictory behavior of the silica gel layers versus the chiral compounds was observed. The migration tracks of chiral compounds in the ascending planar chromatographic mode were not vertical but bent on either side being a function of analyte chirality. This deviation of the analyte’s migration track was noticed, when using the densitometric scanner to quantify the respective chromatograms. In order to confirm the hypothesis as to the microcrystalline nature of silica gel used in liquid chromatography, it was further investigated through circular dichroism (CD and the data thereof confirmed that the ‘chromatographic’ silica gels are not amorphous but microcrystalline, contributing to the (partial horizontal enantioseparation of the antimer pairs. This paper summarizes the results of our investigation on the microcrystalline nature of silica gels used in planar chromatography and their impact on enantioseparation of the selected pairs of antimers.

  10. The role seemingly of amorphous silica gel layers in chiral separations by planar chromatography

    International Nuclear Information System (INIS)

    Sajewicz, M.; Kowalska, T.

    2007-01-01

    In planar chromatography, silica gel appears as the most frequently used adsorbent. Its preference as planar chromatographic stationary phase is due to its high specific surface area (ca. 700 m2 gl) and relatively simple active sites (silanol groups =Si-OH). The high specific surface area of silica gel and a high density of coverage of its surface with the silanol active sites contribute jointly to an excellent separation performance of this adsorbent. In our experiments on chiral separation of the enantiomer pairs by planar chromatography, contradictory behavior of the silica gel layers versus the chiral compounds was observed. The migration tracks of chiral compounds in the ascending planar chromatographic mode were not vertical but bent on either side being a function of analyte chirality. This deviation of the analytes migration track was noticed, when using the densitometric scanner to quantify the respective chromatograms. In order to confirm the hypothesis as to the microcrystalline nature of silica gel used in liquid chromatography, it was further investigated through circular dichroism (CD) and the data thereof confirmed that the chromatographic silica gels are not amorphous but microcrystalline, contributing to the (partial) horizontal enantioseparation of the antimer pairs. This paper summarizes the results of our investigation on the microcrystalline nature of silica gels used in planar chromatography and their impact on enantioseparation of the selected pairs of antimers. (author)

  11. Rice Husk Ash as a Renewable Source for the Production of Value Added Silica Gel and its Application: An Overview

    Directory of Open Access Journals (Sweden)

    Ram Prasad

    2012-06-01

    Full Text Available In recent years, silica gels have developed a lot of interest due to their extraordinary properties and their existing and potential applications in science and technology. Silica gel has a wide range of applications such as a desiccant, as a preservation tool to control humidity, as an adsorbent, as a catalyst and as a cata-lyst support. Silica gel is a rigid three-dimensional network of colloidal silica, and is classified as: aqua-gel, alco-gel, xero-gel and aero-gel. Out of all known solid porous materials, aero-gels are particularly known for their high specific surface area, high porosity, low bulk density, high thermal insulation value, ultra low dielectric constant and low index of refraction. Because of these extraordinary properties silica aero-gel has many commercial applications such as thermal window insulation, acoustic barriers, super-capacitors and catalytic supports. However, monolithic silica aero-gel has been used extensively in high energy physics in Cherenkov radiation detectors and in shock wave studies at high pressures, inertial confinement fusion (ICF radio-luminescent and micrometeorites. Silica gel can be prepared by using various sol gel precursors but the rice husk (RH is considered as the cheapest source for silica gel production. Rice husk is a waste product abundantly available in rice producing countries during milling of rice. This review article aims at summarizing the developments carried out so far in synthesis, properties, characterization and method of determination of silica, silica gel, silica aero-gel and silica xero-gel. The effect of synthesis parameters such as pH, temperature of burning the rice husk, acid leaching prior to formation of rice husk ash (RHA on the properties of final product are also described. The attention is also paid on the application of RH, RHA, sil-ica, silica aero-gel and silica xero-gel. Development of economically viable processes for getting rice husk silica with specific

  12. Synthesis of all-silica zeolites from highly concentrated gels containing hexamethonium cations

    KAUST Repository

    Liu, Xiaolong; Ravon, Ugo; Tuel, Alain

    2012-01-01

    A pure and highly crystalline all-silica EU-1 zeolite has been obtained from the crystallization of gels containing very low water contents in the presence of hexamethonium cations. Decreasing the water content in the gel down to H 2O/Si < 1

  13. Spectroscopic studies of Cu ions in sol–gel derived silica matrix

    Indian Academy of Sciences (India)

    Unknown

    Abstract. The Cu2+ ion doped silica gel matrices in monolithic shape were prepared by hydrolysis and condensation of tetraethyl orthosilicate (TEOS). The absorption, transmittance and fluorescence spectra of the gel matrices heat treated at different temperatures were monitored. The loss of water and hydroxyl group from.

  14. Grafting the sol-gel based sorbents by diazonium salts: a novel approach toward unbreakable capillary microextraction.

    Science.gov (United States)

    Bagheri, Habib; Bayat, Parisa; Piri-Moghadam, Hamed

    2013-11-29

    The present work deals with a novel approach for grafting a sol-gel based sorbent, using diazonium salts for preparation of an unbreakable capillary microextraction (CME) device in on-line combination with high performance liquid chromatography (HPLC). The use of diazonium salts modifier allowed all types of metallic and non-metallic substrates to be used without any limitation. Substrates including copper, brass, stainless steel and polytetrafluoroethylene (PTFE) were chosen to be functionalized by chemical or electrochemical reduction of 4-amino phenyl acetic acid. Then, 3-(trimethoxysilyl)propylamine (3TMSPA) was selected as the precursor and the only reagent for preparation of the desired surface chemical bonded sorbent. The presence of chemical bond between substrate, diazonium salts and 3TMSPA is more probably responsible for thermal and solvent stability and long lifetime of the prepared sorbent. Characterization of the aryl group formation on the various substrates along with the prepared sorbents was thoroughly investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetry analysis (TGA). Typically, one of the prepared sorbents, deposited on the inner surface of the copper tube, was selected for assessing the developed method. The CME device was used for on-line extraction of atrazine, ametryn and terbutryn, as model compounds, from the aquatic media. After extraction, the HPLC mobile phase was used for on-line desorption and elution of the extracted analytes from the CME loop, containing the grafted sol-gel based sorbent, through the HPLC column. Figures of merit of the developed method were also obtained in which the linearity for the analytes was in the range of 30-1000μgL(-1). The value of LOD (S/N=3) for all analytes was 10μgL(-1) and the RSD% values (n=5) were all below 9.4% at the 500μgL(-1) level. Applicability of the developed method was examined by analyzing some real water samples in

  15. Preparation and characterization of silk/silica hybrid biomaterials by sol-gel crosslinking process

    Energy Technology Data Exchange (ETDEWEB)

    Hou Aiqin, E-mail: aiqinhou@dhu.edu.c [National Engineering Research Center for Dyeing and Finishing of Textiles, Donghua University, 3H, 2999 North Renmin Road, Songjiang, Shanghai 201620 (China); Chen Huawei [National Engineering Research Center for Dyeing and Finishing of Textiles, Donghua University, 3H, 2999 North Renmin Road, Songjiang, Shanghai 201620 (China)

    2010-03-15

    The silk/silica hybrid biomaterials are synthesized by sol-gel crosslinking process. The chemical and morphological structures of silk/silica hybrids are investigated with micro-FT-IR spectra, X-ray diffraction, SEM, AFM, and DSC. The results show that the crosslinking reactions among inorganic nano-particles, fibroin and 2,4,6-tri[(2-epihydrin-3-bimethyl-ammonium)propyl]-1,3,5-triazine chloride (Tri-EBAC) take place during sol-gel process. The silk/silica hybrids form new molecular structures containing not only organic fibroin but also inorganic nano-silica particles. The inorganic particles are bounded to the fibroin through covalent bonds. The silk/silica hybrids can form excellent film with very even nanometer particles. The thermal properties of organic/inorganic hybrid are improved.

  16. Preparation and characterization of silk/silica hybrid biomaterials by sol-gel crosslinking process

    International Nuclear Information System (INIS)

    Hou Aiqin; Chen Huawei

    2010-01-01

    The silk/silica hybrid biomaterials are synthesized by sol-gel crosslinking process. The chemical and morphological structures of silk/silica hybrids are investigated with micro-FT-IR spectra, X-ray diffraction, SEM, AFM, and DSC. The results show that the crosslinking reactions among inorganic nano-particles, fibroin and 2,4,6-tri[(2-epihydrin-3-bimethyl-ammonium)propyl]-1,3,5-triazine chloride (Tri-EBAC) take place during sol-gel process. The silk/silica hybrids form new molecular structures containing not only organic fibroin but also inorganic nano-silica particles. The inorganic particles are bounded to the fibroin through covalent bonds. The silk/silica hybrids can form excellent film with very even nanometer particles. The thermal properties of organic/inorganic hybrid are improved.

  17. Radiation hardening of sol gel-derived silica fiber preforms through fictive temperature reduction.

    Science.gov (United States)

    Hari Babu, B; Lancry, Matthieu; Ollier, Nadege; El Hamzaoui, Hicham; Bouazaoui, Mohamed; Poumellec, Bertrand

    2016-09-20

    The impact of fictive temperature (Tf) on the evolution of point defects and optical attenuation in non-doped and Er3+-doped sol-gel silica glasses was studied and compared to Suprasil F300 and Infrasil 301 glasses before and after γ-irradiation. To this aim, sol-gel optical fiber preforms have been fabricated by the densification of erbium salt-soaked nanoporous silica xerogels through the polymeric sol-gel technique. These γ-irradiated fiber preforms have been characterized by FTIR, UV-vis-NIR absorption spectroscopy, electron paramagnetic resonance, and photoluminescence measurements. We showed that a decrease in the glass fictive temperature leads to a decrease in the glass disorder and strained bonds. This mainly results in a lower defect generation rate and thus less radiation-induced attenuation in the UV-vis range. Furthermore, it was found that γ-radiation "hardness" is higher in Er3+-doped sol-gel silica compared to un-doped sol-gel silica and standard synthetic silica glasses. The present work demonstrates an effective strategy to improve the radiation resistance of optical fiber preforms and glasses through glass fictive temperature reduction.

  18. Tritium isotope separation by water distillation column packed with silica-gel beads

    International Nuclear Information System (INIS)

    Fukada, Satoshi

    2004-01-01

    Tritium enrichment or depletion by water distillation was investigated using a glass column of 32cm in height packed with silica-gel beads of 3.4mm in average diameter. The total separation factor of the silica-gel distillation column, α H-T , was compared with those of an open column distillation tower and of a column packed with stainless-steel Dixon rings. Depletion of the tritium activity in the distillate was enhanced by isotopic exchange with water absorbed on silica-gel beads that have a higher affinity for HTO than for H 2 O. The value of α H-T -1 of the silica-gel distillation column was about four times larger than that of a column without any packing and about two times larger than that of the Dixon-ring column. The improvement of α H-T by the silica-gel adsorbent indicated that the height of the distillation-adsorption column becomes shorter than that of the height of conventional distillation columns. (author)

  19. Influence of organic solvents on interfacial water at surfaces of silica gel and partially silylated fumed silica

    Energy Technology Data Exchange (ETDEWEB)

    Turov, V.V.; Gun' ko, V.M.; Tsapko, M.D.; Bogatyrev, V.M.; Skubiszewska-Zieba, J.; Leboda, R.; Ryczkowski, J

    2004-05-15

    The effects of organic solvents (dimethylsulfoxide-d{sub 6} (DMSO-d{sub 6}), chloroform-d, acetone-d{sub 6}, and acetonitrile-d{sub 3}) on the properties of interfacial water at surfaces of silica gel Si-40 and partially silylated fumed silica A-380 were studied by means of the {sup 1}H NMR spectroscopy with freezing-out of adsorbed water at 180silicas and quantum chemical calculations of the chemical shifts {delta}{sub H} and solvent effects. DMSO-d{sub 6} and acetonitrile-d{sub 3} are poorly miscible with water in silica gel pores in contrast to the bulk liquids. DMSO-d{sub 6} and chloroform-d affect the structure of the interfacial water weaker than acetone-d{sub 6} and acetonitrile-d{sub 3} at amounts of liquids greater than the pore volume. Acetone-d{sub 6} and acetonitrile-d{sub 3} can displace water from pores under this condition. The chemical shift of protons in water adsorbed on silica gel is 3.5-6.5 ppm, which corresponds to the formation of two to four hydrogen bonds per molecule. Water adsorbed on partially silylated fumed silica has two {sup 1}H NMR signals at 5 and 1.1-1.7 ppm related to different structures (droplets and small clusters) of the interfacial water.

  20. Fumed and Precipitated Hydrophilic Silica Suspension Gels in Mineral Oil: Stability and Rheological Properties

    Directory of Open Access Journals (Sweden)

    Yoshiki Sugino

    2017-08-01

    Full Text Available Hydrophilic fumed silica (FS and precipitated silica (PS powders were suspended in mineral oil; increasing the silica volume fraction (φ in the suspension led to the formation of sol, pre-gel, and gel states. Gelation took place at lower φ values in the FS than the PS suspension because of the lower silanol density on the FS surface. The shear stresses and dynamic moduli of the FS and PS suspensions were measured as a function of φ. Plots of the apparent shear viscosity against shear rate depended on φ and the silica powder. The FS suspensions in the gel state exhibited shear thinning, followed by a weak shear thickening or by constant viscosity with an increasing shear rate. In contrast, the PS suspensions in the gel state showed shear thinning, irrespective of φ. The dynamic moduli of the pre-gel and gel states were dependent on the surface silanol density: at a fixed φ, the storage modulus G′ in the linear viscoelasticity region was larger for the FS than for the PS suspension. Beyond the linear region, the G′ of the PS suspensions showed strain hardening and the loss modulus G″ of the FS and PS suspensions exhibited weak strain overshoot.

  1. Styrene grafted natural rubber reinforced by in situ silica generated via sol–gel technique

    Energy Technology Data Exchange (ETDEWEB)

    Sittiphan, Torpong [Program of Petrochemistry and Polymer Sciences, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Prasassarakich, Pattarapan [Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand); Poompradub, Sirilux, E-mail: sirilux.p@chula.ac.th [Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Bangkok 10330 (Thailand)

    2014-02-15

    Highlights: • Sol–gel reaction by NR latex was the absence of use of organic solvent and base catalyst. • Well dispersed in situ formed silica particles in the rubber matrix were obtained. • In situ silica was better to improve mechanical properties of rubber vulcanizates. -- Abstract: The filling of styrene graft natural rubber (ST-GNR) with in situ formed silica was performed using the sol–gel reaction via the latex solution method. The mechanical properties of ST-GNR/NR vulcanizate were improved when using the in situ formed silica to levels higher than those obtained with the commercial ex situ formed silica filled ST-GNR/NR vulcanizates at a comparable silica content of 12 parts by weight per hundred parts of rubber. Transmission electron microscopy analysis revealed that the in situ silica particles were small (∼40 nm diameter) and well dispersed, while the commercial silica particles were larger (∼60 nm diameter) and markedly agglomerated in the rubbery matrix. The mechanical properties of the composites prepared via both the solid rubber and latex solution methods were comparable.

  2. Sorption of the organic cation metoprolol on silica gel from its aqueous solution considering the competition of inorganic cations.

    Science.gov (United States)

    Kutzner, Susann; Schaffer, Mario; Börnick, Hilmar; Licha, Tobias; Worch, Eckhard

    2014-05-01

    Systematic batch experiments with the organic monovalent cation metoprolol as sorbate and the synthetic material silica gel as sorbent were conducted with the aim of characterizing the sorption of organic cations onto charged surfaces. Sorption isotherms for metoprolol (>99% protonated in the tested pH of around 6) in competition with mono- and divalent inorganic cations (Na(+), NH4(+), Ca(2+), and Mg(2+)) were determined in order to assess their influence on cation exchange processes and to identify the role of further sorptive interactions. The obtained sorption isotherms could be described well by an exponential function (Freundlich isotherm model) with consistent exponents (about 0.8). In general, a decreasing sorption of metoprolol with increasing concentrations in inorganic cations was observed. Competing ions of the same valence showed similar effects. A significant sorption affinity of metoprolol with ion type dependent Freundlich coefficients KF,0.77 between 234.42 and 426.58 (L/kg)(0.77) could still be observed even at very high concentrations of competing inorganic cations. Additional column experiments confirm this behavior, which suggests the existence of further relevant interactions beside cation exchange. In subsequent batch experiments, the influence of mixtures with more than one competing ion and the effect of a reduced negative surface charge at a pH below the point of zero charge (pHPZC ≈ 2.5) were also investigated. Finally, the study demonstrates that cation exchange is the most relevant but not the sole mechanism for the sorption of metoprolol on silica gel. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Experimentation of netlike hydro gel nitrogen containing polymer sorbents for biological liquids purification

    International Nuclear Information System (INIS)

    Karieva, Z.M.; Karimova, N. Kh.

    2003-01-01

    The high efficiency of hydrogels synthesized earlier in comparison with Pharmacopoeia sorbents are interesting to study comprehensively for the number of the toxins of biological liquids. Taking into considerations the high electoral sorption ability of ethynilpiperidol polymers to the hydro phobic interaction it may be suggested that they have a high detoxication ability. The detoxication characteristics of studied polymers have advantages over the known sorbents. Experiences with animals showed that in identical conditions of experiment in application of netlike polymers the survival grew 90%. Synthesis and investigations of netlike hydrogels polymer materials on nitrogen containing monomers of ethynil piperidol were given in the work. (author)

  4. Radiation hardness of Ce-doped sol-gel silica fibers for high energy physics applications.

    Science.gov (United States)

    Cova, Francesca; Moretti, Federico; Fasoli, Mauro; Chiodini, Norberto; Pauwels, Kristof; Auffray, Etiennette; Lucchini, Marco Toliman; Baccaro, Stefania; Cemmi, Alessia; Bártová, Hana; Vedda, Anna

    2018-02-15

    The results of irradiation tests on Ce-doped sol-gel silica using x- and γ-rays up to 10 kGy are reported in order to investigate the radiation hardness of this material for high-energy physics applications. Sol-gel silica fibers with Ce concentrations of 0.0125 and 0.05 mol. % are characterized by means of optical absorption and attenuation length measurements before and after irradiation. The two different techniques give comparable results, evidencing the formation of a main broad radiation-induced absorption band, peaking at about 2.2 eV, related to radiation-induced color centers. The results are compared with those obtained on bulk silica. This study reveals that an improvement of the radiation hardness of Ce-doped silica fibers can be achieved by reducing Ce content inside the fiber core, paving the way for further material development.

  5. Drying kinetics and characteristics of dried gambir leaves using solar heating and silica gel dessicant

    Science.gov (United States)

    Hasibuan, R.; Hidayati, J.; Sundari, R.; Wicaksono, A. S.

    2018-02-01

    A drying combination of solar heating and silica gel dessicant has been applied to dry gambir leaves. The solar energy is captured by a collector to heat the air and the hot air is used to dry gambir leaves in a drying chamber. An exhaust fan in drying chamber assists to draw water molecules from gambir leaves accelerated by silica gel dessicant. This study has investigated the drying kinetics and drying characteristics of gambir leaves drying. In drying operation the air velocity is tuned by a PWM (pulse width modulation) controller to adjust minimum and maximum level, which is based on the rotation speed of the exhaust fan. The results show that the air velocity influenced the drying kinetics and drying characteristics of gambir leaves using solar-dessicant drying at 40 cm distance between exhaust fan and silica gel dessicant.

  6. Thermo-physical properties of silica gel for adsorption desalination cycle

    KAUST Repository

    Thu, Kyaw; Chakraborty, Anutosh; Saha, Bidyut Baran; Ng, Kim Choon

    2013-01-01

    Thermo-physical properties, surface characteristics and water vapor uptake capacity are key parameters in the selection of adsorbent for an adsorption desalination (AD) cycle. In the AD cycles, silica gel is used as adsorbent due to their high water vapor uptake capacity, reliability, repeatability and inexpensiveness as compared to other adsorbents. Three types of commercially available silica gels (Type-RD 2560,Type-A5BW and Type-A++) are investigated using a surface characteristic analyzer and their thermo-physical properties are evaluated using several analysis methods. The instrument used in this investigation employs the static volumetric method with liquid Nitrogen at 77 K as the filing fluid. The surface area of each adsorbent is studied using Brunauer-Emmett-Teller (BET) method whilst the pore size distribution (PSD) analysis is conducted with the Non-Local Density Functional Theory (NLDFT). It is observed that the Type-A++ silica gel (granular type) possesses the highest surface area of 863.6 m2/g amongst the three parent silica gels studied. It has a two-maxima or bimodal distribution pattern where the pore diameters are distributed mostly between 10 Å and 30 Å. Water vapor uptake capacity of silica gels are studied with water vapor dosage apparatus and the results show that the Type-A++ silica gel exhibits a highest equilibrium uptake at 537 cm3/g. These thermo-physical properties are essential for the design and the numerical simulation of AD cycles. © 2012 Published by Elsevier Ltd.

  7. Thermo-physical properties of silica gel for adsorption desalination cycle

    KAUST Repository

    Thu, Kyaw

    2013-02-01

    Thermo-physical properties, surface characteristics and water vapor uptake capacity are key parameters in the selection of adsorbent for an adsorption desalination (AD) cycle. In the AD cycles, silica gel is used as adsorbent due to their high water vapor uptake capacity, reliability, repeatability and inexpensiveness as compared to other adsorbents. Three types of commercially available silica gels (Type-RD 2560,Type-A5BW and Type-A++) are investigated using a surface characteristic analyzer and their thermo-physical properties are evaluated using several analysis methods. The instrument used in this investigation employs the static volumetric method with liquid Nitrogen at 77 K as the filing fluid. The surface area of each adsorbent is studied using Brunauer-Emmett-Teller (BET) method whilst the pore size distribution (PSD) analysis is conducted with the Non-Local Density Functional Theory (NLDFT). It is observed that the Type-A++ silica gel (granular type) possesses the highest surface area of 863.6 m2/g amongst the three parent silica gels studied. It has a two-maxima or bimodal distribution pattern where the pore diameters are distributed mostly between 10 Å and 30 Å. Water vapor uptake capacity of silica gels are studied with water vapor dosage apparatus and the results show that the Type-A++ silica gel exhibits a highest equilibrium uptake at 537 cm3/g. These thermo-physical properties are essential for the design and the numerical simulation of AD cycles. © 2012 Published by Elsevier Ltd.

  8. Porous Silica Sol-Gel Glasses Containing Reactive V2O5 Groups

    Science.gov (United States)

    Stiegman, Albert E.

    1995-01-01

    Porous silica sol-gel glasses into which reactive vanadium oxide functional groups incorporated exhibit number of unique characteristics. Because they bind molecules of some species both reversibly and selectively, useful as chemical sensors or indicators or as scrubbers to remove toxic or hazardous contaminants. Materials also oxidize methane gas photochemically: suggests they're useful as catalysts for conversion of methane to alcohol and for oxidation of hydrocarbons in general. By incorporating various amounts of other metals into silica sol-gel glasses, possible to synthesize new materials with broad range of new characteristics.

  9. Fabrication of mesoporous silica nanoparticles by sol gel method followed various hydrothermal temperature

    Science.gov (United States)

    Purwaningsih, Hariyati; Pratiwi, Vania Mitha; Purwana, Siti Annisa Bani; Nurdiansyah, Haniffudin; Rahmawati, Yenny; Susanti, Diah

    2018-04-01

    Rice husk is an agricultural waste that is potentially used as natural silica resources. Natural silica claimed to be safe in handling, cheap and can be generate from cheap resource. In this study mesoporous silica was synthesized using sodium silicate extracted from rice husk ash. This research's aim are to study the optimization of silica extraction from rice husk, characterizing mesoporous silica from sol-gel method and surfactant templating from rice husk and the effect of hydrothermal temperature on mesoporous silica nanoparticle (MSNp) formation. In this research, rice husk was extracted with sol-gel method and was followed by hydrothermal treatment; several of hydrothermal temperatures were 85°C, 100°C, 115°C, 130°C and 145° for 24 hours. X-ray diffraction analysis was identified of α-SiO2 phase and NaCl compound impurities. Scherer's analysis method for crystallite size have resulted 6.27-40.3 nm. FTIR results of silica from extraction and MSNp indicated Si-O-Si bonds on the sample. SEM result showed the morphology of the sample that has spherical shape and smooth surface. TEM result showed particle size ranged between 69,69-84,42 nm. BET showed that the pore size classified as mesoporous with pore diameter size is 19,29 nm.

  10. Evaluation of an ambient air sampling system for tritium (as tritiated water vapor) using silica gel adsorbent columns

    International Nuclear Information System (INIS)

    Patton, G.W.; Cooper, A.T.; Tinker, M.R.

    1995-08-01

    Ambient air samples for tritium analysis (as the tritiated water vapor [HTO] content of atmospheric moisture) are collected for the Hanford Site Surface Environmental Surveillance Project (SESP) using the solid adsorbent silica gel. The silica gel has a moisture sensitive indicator which allows for visual observation of moisture movement through a column. Despite using an established method, some silica gel columns showed a complete change in the color indicator for summertime samples suggesting that breakthrough had occurred; thus a series of tests was conducted on the sampling system in an environmental chamber. The purpose of this study was to determine the maximum practical sampling volume and overall collection efficiency for water vapor collected on silica gel columns. Another purpose was to demonstrate the use of an impinger-based system to load water vapor onto silica gel columns to provide realistic analytical spikes and blanks for the Hanford Site SESP. Breakthrough volumes (V b ) were measured and the chromatographic efficiency (expressed as the number of theoretical plates [N]) was calculated for a range of environmental conditions. Tests involved visual observations of the change in the silica gel's color indicator as a moist air stream was drawn through the column, measurement of the amount of a tritium tracer retained and then recovered from the silica gel, and gravimetric analysis for silica gel columns exposed in the environmental chamber

  11. Alkali Metal Modification of Silica Gel-Based Stationary Phase in Gas Chromatography

    Directory of Open Access Journals (Sweden)

    Ashraf Yehia El-Naggar

    2013-01-01

    Full Text Available Modification of the precipitated silica gel was done by treatment with alkali metal (NaCl before and after calcination. The silica surfaces before and after modification were confirmed by infrared spectroscopy in order to observe the strength and abundance of the acidic surface OH group bands which play an important role in the adsorption properties of polar and nonpolar solutes. The surface-modified silica gels were tested as GC solid stationary phases in terms of the separation efficiency for various groups of non-polar and polar solutes. Also, thermodynamic parameters (ΔH, ΔG, and ΔS were determined using n-hexane as a probe in order to show the adsorbate-adsorbent interaction. It was observed that the non-polar solutes could be separated Independent on the reactivity and porosity of the silica surfaces. The efficiency of the surface-modified silica gels to separate the aromatic hydrocarbons seemed to be strongly influenced by the density of the surface hydroxyls.

  12. Tetragonal zirconia quantum dots in silica matrix prepared by a modified sol-gel protocol

    Science.gov (United States)

    Verma, Surbhi; Rani, Saruchi; Kumar, Sushil

    2018-05-01

    Tetragonal zirconia quantum dots (t-ZrO2 QDs) in silica matrix with different compositions ( x)ZrO2-(100 - x)SiO2 were fabricated by a modified sol-gel protocol. Acetylacetone was added as a chelating agent to zirconium propoxide to avoid precipitation. The powders as well as thin films were given thermal treatment at 650, 875 and 1100 °C for 4 h. The silica matrix remained amorphous after thermal treatment and acted as an inert support for zirconia quantum dots. The tetragonal zirconia embedded in silica matrix transformed into monoclinic form due to thermal treatment ≥ 1100 °C. The stability of tetragonal phase of zirconia is found to enhance with increase in silica content. A homogenous dispersion of t-ZrO2 QDs in silica matrix was indicated by the mapping of Zr, Si and O elements obtained from scanning electron microscope with energy dispersive X-ray analyser. The transmission electron images confirmed the formation of tetragonal zirconia quantum dots embedded in silica. The optical band gap of zirconia QDs (3.65-5.58 eV) was found to increase with increase in zirconia content in silica. The red shift of PL emission has been exhibited with increase in zirconia content in silica.

  13. [A treatment to serious esophageal cicatrices stenosi by metal and silica gel dilator].

    Science.gov (United States)

    Li, J; Chen, X; Sun, C; Liu, H

    1999-12-01

    To find an effective method of treating the esophageal cicatricial stenosis. Six cases with esophageal cicatricial stenosis were treated by mental and silica gel dilator. The effects in all six cases were satisfactory and no any complications were finded. The method is safe, effective and of no complications, the treatment time is shorter also.

  14. Influence of p H on optical properties of nano structure sol-gel-derived silica films

    International Nuclear Information System (INIS)

    Heshmatpuor, F.; Adelkhani, H.; Nahavandi, M.; Noorbakhsh Shourabadi, M.

    2006-01-01

    Sol-gel derived silica films were fabricated by dip-coating onto glass microscope substrates. Film properties such as transmission and surface morphology were monitored as function of dip speed and sol p H. Film transmission was increased with increasing of p H in visible range. The surface morphology of films were investigated with scanning electron microscopy.

  15. Development of novel biocompatible hybrid nanocomposites based on polyurethane-silica prepared by sol gel process

    Energy Technology Data Exchange (ETDEWEB)

    Rashti, Ali [Department of Medical Nanotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Yahyaei, Hossein [Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Firoozi, Saman [Department of Tissue Engineering & Regenerative Medicine, Faculty of Advanced Technologies in Medicine, Iran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Ramezani, Sara [Department of Neuroscience, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Rahiminejad, Ali [Department of Medical Nanotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Karimi, Roya [Department of Tissue Engineering and Applied Cell Science, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Farzaneh, Khadijeh [Tehran Heart Center, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Mohseni, Mohsen [Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Ghanbari, Hossein, E-mail: hghanbari@tums.ac.ir [Department of Medical Nanotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Tehran Heart Center, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of); Medical Biomaterials Research Center, Tehran University of Medical Sciences, Tehran (Iran, Islamic Republic of)

    2016-12-01

    Due to high biocompatibility, polyurethane has found many applications, particularly in development of biomedical devices. A new nanocomposite based on thermoset polyurethane and silica nanoparticles was synthesized using sol-gel method. Sol-gel process was fulfilled in two acidic and basic conditions by using tetraethylorthosilicate (TEOS) and trimethoxyisocyanatesilane as precursors. The hybrid films characterized for mechanical and surface properties using tensile strength, contact angle, ATR-FTIR and scanning electron microscopy. Biocompatibility and cytotoxicity of the hybrids were assessed using standard MTT, LDH and TUNEL assays. The results revealed that incorporation of silica nanoparticles was significantly improved tensile strength and mechanical properties of the hybrids. Based on the contact angle results, silica nanoparticles increased hydrophilicity of the hybrids. Biocompatibility by using human lung epithelial cell line (MRC-5) demonstrated that the hybrids were significantly less cytotoxic compared to pristine polymer as tested by MTT and LDH assays. TUNEL assay revealed no signs of apoptosis in all tested samples. The results of this study demonstrated that incorporation of silica nanoparticles into polyurethane lead to the enhancement of biocompatibility, indicating that these hybrids could potentially be used in biomedical field in particular as a new coating for medical implants. - Highlights: • Nanocomposites based on polyurethane and nanosilica prepared by sol-gel method fabricated • Addition of inorganic phase improved mechanical properties. • Nanosilica prepared by sol-gel method increased hydrophilicity. • By adding nanosilica to polyurethane biocompatibility increased significantly.

  16. Moisture sensor based on evanescent wave light scattering by porous sol-gel silica coating

    Science.gov (United States)

    Tao, Shiquan; Singh, Jagdish P.; Winstead, Christopher B.

    2006-05-02

    An optical fiber moisture sensor that can be used to sense moisture present in gas phase in a wide range of concentrations is provided, as well techniques for making the same. The present invention includes a method that utilizes the light scattering phenomenon which occurs in a porous sol-gel silica by coating an optical fiber core with such silica. Thus, a porous sol-gel silica polymer coated on an optical fiber core forms the transducer of an optical fiber moisture sensor according to an embodiment. The resulting optical fiber sensor of the present invention can be used in various applications, including to sense moisture content in indoor/outdoor air, soil, concrete, and low/high temperature gas streams.

  17. Sol-gel preparation of Ag-silica nanocomposite with high electrical conductivity

    Science.gov (United States)

    Ma, Zhijun; Jiang, Yuwei; Xiao, Huisi; Jiang, Bofan; Zhang, Hao; Peng, Mingying; Dong, Guoping; Yu, Xiang; Yang, Jian

    2018-04-01

    Sol-gel derived noble-metal-silica nanocomposites are very useful in many applications. Due to relatively low price, higher conductivity, and higher chemical stability of silver (Ag) compared with copper (Cu), Ag-silica has gained much more research interest. However, it remains a significant challenge to realize high loading of Ag content in sol-gel Ag-silica composite with high structural controllability and nanoparticles' dispersity. Different from previous works by using multifunctional silicon alkoxide to anchor metal ions, here we report the synthesis of Ag-silica nanocomposite with high loading of Ag nanoparticles by employing acetonitrile bi-functionally as solvent and metal ions stabilizer. The electrical conductivity of the Ag-silica nanocomposite reached higher than 6800 S/cm. In addition, the Ag-silica nanocomposite could simultaneously possess high electrical conductivity and positive conductivity-temperature coefficient by properly controlling the loading content of Ag. Such behavior is potentially advantageous for high-temperature devices (like phosphoric acid fuel cells) and inhibiting the thermal-induced increase of devices' internal resistance. The strategy proposed here is also compatible with block-copolymer directed self-assembly of mesoporous material, spin-coating of film and electrospinning of nanofiber, making it more charming in various practical applications.

  18. Preparation of mesoporous silica microparticles by sol-gel/emulsion route for protein release.

    Science.gov (United States)

    Vlasenkova, Mariya I; Dolinina, Ekaterina S; Parfenyuk, Elena V

    2018-04-06

    Encapsulation of therapeutic proteins into particles from appropriate material can improve both stability and delivery of the drugs, and the obtained particles can serve as a platform for development of their new oral formulations. The main goal of this work was development of sol-gel/emulsion method for preparation of silica microcapsules capable of controlled release of encapsulated protein without loss of its native structure. For this purpose, the reported in literature direct sol-gel/W/O/W emulsion method of protein encapsulation was used with some modifications, because the original method did not allow to prepare silica microcapsules capable for protein release. The particles were synthesized using sodium silicate and tetraethoxysilane as silica precursors and different compositions of oil phase. In vitro kinetics of bovine serum albumin (BSA) release in buffer (pH 7.4) was studied by Fourier transform infrared (FTIR) and fluorescence spectrometry, respectively. Structural state of encapsulated BSA and after release was evaluated. It was found that the synthesis conditions influenced substantially the porous structure of the unloaded silica particles, release properties of the BSA-loaded silica particles and structural state of the encapsulated and released protein. The modified synthesis conditions made it possible to obtain the silica particles capable of controlled release of the protein during a week without loss of the protein native structure.

  19. Synthesis and Application of Iron Oxide/Silica Gel Nanocomposite for Removal of Sulfur Dyes from Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Naser Tavassoli

    2017-03-01

    Full Text Available Background & Aims of the Study: water pollution by synthetic organic dyes is mainly regarded as environmental and ecological critical issues worldwide. In this research, magnetite iron oxide/silica gel nanocomposite (termed as Fe3O4/SG was synthesized chemically and then used as an effective adsorbent for removal of sulfur dyes from aqueous solution. Materials and Methods: The various parameters such as pH, sorbent dosage, initial dye concentration, contact time and dye solution temperature were investigated in a batch system. The equilibrium data were analyzed by Langmuir and Freundlich isotherm models. Results: The experimental data fit well with pseudo-second-order kinetic model (R2≥0.998 and conformed better to Langmuir isotherm model (R2≥0.997. The maximum adsorption capacity for Fe3O4/SG obtained from the Langmuir model was 11.1mg/g. Evaluation of thermodynamic parameters proved that the adsorption process was normally feasible, spontaneous and exothermic. Conclusion: It can be concluded that the Fe3O4/SG can be considered as a cost-effective and an environmental friendly adsorbent for efficient removal of sulfur dyes from aqueous solutions.

  20. Comparison study for the CCME reference method for determination of PHC in soil by using internal and external standard methods and by using silica gel column cleanup and in-situ silica gel cleanup methods

    International Nuclear Information System (INIS)

    Wang, Z.; Fingas, M.; Sigouin, L.; Yang, C.; Hollebone, B.

    2003-01-01

    The assessment, cleanup, and remediation of hydrocarbon contaminated sites is covered in the Reference Method for Canada-Wide Standard for Petroleum Hydrocarbons-Tier 1 Method. It replaces several analytical methods used in the past by some laboratories and jurisdictions in Canada. The authors conducted two comparative evaluations to validate the Tier 1 Analytical Method. The first compared the Internal and External Standard Methods, and the second compared the Silica Gel Column Cleanup Method with the In-situ Silica Gel Cleanup Method. The Canadian Council of Ministers of the Environment (CCME) Tier 1 Method recommends and requires the External Standard Method to determine petroleum hydrocarbons (PHC) in soil samples. The Internal Method is widely used to quantify various organic and inorganic pollutants in environmental samples. The Tier 1 Method offers two options for the same extract cleanup. They are: Option A - In-situ Silica Gel Cleanup, and Option B - Silica Gel Column Cleanup. Linearity, precision, and PHC quantification results were the parameters considered for diesel and motor oil solutions, for diesel spiked soil samples, and for motor oil spiked soil samples. It was concluded that both the External and Internal Standard Methods for gas chromatograph (GC) determination of PHC in soil possess their own advantages. The PHC results obtained using the In-Situ Silica Gel Cleanup Method were lower than those obtained with the Silica Gel Column Cleanup Methods. The more efficient and effective sample cleanup method proved to be the Silica Gel Column Method. 13 refs., 7 tabs., 7 figs

  1. Thermal stability of octadecylsilane hybrid silicas prepared by grafting and sol-gel methods

    International Nuclear Information System (INIS)

    Brambilla, Rodrigo; Santos, Joao H.Z. dos; Miranda, Marcia S.L.; Frost, Ray L.

    2008-01-01

    Hybrid silicas bearing octadecylsilane groups were prepared by grafting and sol-gel (SG) methods. The effect of the preparative route on the thermal stability was evaluated by means of thermal gravimetric analysis (TGA), infrared emission spectroscopy (IRES) and, complementary, by 13 C solid-state nuclear magnetic resonance ( 13 C NMR) and matrix assisted laser deionization time of flight mass spectroscopy (MALDI-TOF-MS). Silicas prepared by the grafting route seem to be slightly more stable than those produced by the sol-gel method. This behavior seems to be associated to the preparative route, since grafting affords a liquid-like conformation, while in the case of sol-gel a highly organized crystalline chain conformation was observed

  2. Titania-Coated Silica Alone and Modified by Sodium Alginate as Sorbents for Heavy Metal Ions

    Science.gov (United States)

    Kołodyńska, D.; Gęca, M.; Skwarek, E.; Goncharuk, O.

    2018-04-01

    The novel organic-inorganic biohybrid composite adsorbent was synthesized based on nanosized silica-titania modified with alginate within the development of effective adsorbent for heavy metal ions. Effects of metal species Cu(II), Zn(II), Cd(II), and Pb(II); concentrations; pH; temperature; and adsorption onto titania-coated silica (ST20) initial or modified by sodium alginate (ST20-ALG) were studied. The equilibrium and kinetic data of metal ions adsorption were analyzed using Langmuir and Freundlich adsorption models and kinetic models: pseudo first order, pseudo second order, intraparticle kinetic model, and Elovich. The maximum sorption capacities observed were higher for the ST20-ALG composite compared to the initial ST20 oxide for all studied metal ions, namely their values for ST20-ALG were 22.44 mg g- 1 for Cu(II) adsorption, 19.95 mg g- 1 for Zn(II), 18.85 mg g- 1 for Cd(II), and 32.49 mg g- 1 for Pb(II). Structure and properties of initial silica-titania ST20 and modified by sodium alginate ST20-ALG adsorbents were analyzed using nitrogen adsorption/desorption isotherms, ATR-FTIR, SEM-EDS, and pHpzc techniques.

  3. Hydrogen sulfide removal from hot coal gas by various mesoporous silica supported Mn{sub 2}O{sub 3} sorbents

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z.F.; Liu, B.S., E-mail: bingsiliu@tju.edu.cn; Wang, F.; Wang, W.S.; Xia, C.; Zheng, S.; Amin, R.

    2014-09-15

    Graphical abstract: - Highlights: • Mn{sub 2}O{sub 3}/KIT-1 presented the best desulfurization performance at 600–850 °C. • High sulfur capacity of Mn{sub 2}O{sub 3}/KIT-1 correlated closely with 3-D channel of KIT-1. • Desulfurization character depended strongly on framework structure of sorbents. • High steam content suppressed greatly the occurrence of sulfidation reaction. - Abstract: A series of 50 wt% Mn{sub 2}O{sub 3} sorbents was prepared using various mesoporous silica, MCM-41, HMS, and KIT-1 as support. The influence of textural parameters of mesoporous silica, especially type of channel on the desulfurization performance of Mn{sub 2}O{sub 3} sorbents was investigated at 600–850 °C using hot coal gas containing 0.33 vol.% H{sub 2}S. The fresh and used sorbents were characterized by means of N{sub 2}-adsorption, x-ray diffraction (XRD), high resolution transmission microscopy (HRTEM) and H{sub 2} temperature- programmed reduction (H{sub 2}-TPR) techniques. The results confirmed that the manganese oxide was dispersed highly in regular pore channel of the mesoporous supports due to high surface area. Compared with the Mn{sub 2}O{sub 3}/diatomite, all mesoporous silica supported Mn{sub 2}O{sub 3} sorbents exhibited high breakthrough sulfur capacity and a sharp deactivation rate after the breakthrough point. Compared to Mn{sub 2}O{sub 3}/MCM-41 and Mn{sub 2}O{sub 3}/HMS sorbent, the Mn{sub 2}O{sub 3}/KIT-1 showed better desulfurization performance because of the 3D wormhole-like channel. The high sulfur capacity of the Mn{sub 2}O{sub 3}/KIT-1 sorbent was maintained during the eight consecutive desulfurization-regeneration cycles. The Mn{sub 2}O{sub 3}/KIT-1 still presented high desulfurization activity when hot coal gas contained low steam (<5%)

  4. Silica Gel Behavior Under Different EGS Chemical And Thermal Conditions: An Experimental Study

    International Nuclear Information System (INIS)

    Hunt, J.D.; Ezzedine, S.M.; Bourcier, W.; Roberts, S.

    2012-01-01

    Fractures and fracture networks are the principal pathways for migration of water and contaminants in groundwater systems, fluids in enhanced geothermal systems (EGS), oil and gas in petroleum reservoirs, carbon dioxide leakage from geological carbon sequestration, and radioactive and toxic industrial wastes from underground storage repositories. When dealing with EGS fracture networks, there are several major issues to consider, e.g., the minimization of hydraulic short circuits and losses of injected geothermal fluid to the surrounding formation, which in turn maximize heat extraction and economic production. Gel deployments to direct and control fluid flow have been extensively and successfully used in the oil industry for enhanced oil recovery. However, to the best of our knowledge, gels have not been applied to EGS to enhance heat extraction. In-situ gelling systems can either be organic or inorganic. Organic polymer gels are generally not thermostable to the typical temperatures of EGS systems. Inorganic gels, such as colloidal silica gels, however, may be ideal blocking agents for EGS systems if suitable gelation times can be achieved. In the current study, we explore colloidal silica gelation times and rheology as a function of SiO 2 concentration, pH, salt concentration, and temperature, with preliminary results in the two-phase field above 100 C. Results at 25 C show that it may be possible to choose formulations that will gel in a reasonable and predictable amount of time at the temperatures of EGS systems.

  5. Functionalizable Sol-Gel Silica Coatings for Corrosion Mitigation

    Science.gov (United States)

    Gąsiorek, Jolanta; Babiarczuk, Bartosz; Kaleta, Jerzy; Jones, Walis; Krzak, Justyna

    2018-01-01

    Corrosion is constantly a major problem of the world economy in the field of metal products, metal processing and other areas that utilise metals. Previously used compounds utilizing hexavalent chromium were amongst the most effective materials for corrosion protection but regulations have been recently introduced that forbid their use. Consequently, there is a huge drive by engineers, technologists and scientists from different disciplines focused on searching a new, more effective and environmentally-friendly means of corrosion protection. One novel group of materials with the potential to solve metal protection problems are sol-gel thin films, which are increasingly interesting as mitigation corrosion barriers. These environmentally-friendly and easy-to-obtain coatings have the promise to be an effective alternative to hexavalent chromium compounds using for anti-corrosion industrial coatings. In this review the authors present a range of different solutions for slow down the corrosion processes of metallic substrates by using the oxides and doped oxides obtained by the sol-gel method. Examples of techniques used to the sol-gel coating examinations, in terms of anti-corrosion protection, are also presented. PMID:29373540

  6. Functionalizable Sol-Gel Silica Coatings for Corrosion Mitigation

    Directory of Open Access Journals (Sweden)

    Jolanta Gąsiorek

    2018-01-01

    Full Text Available Corrosion is constantly a major problem of the world economy in the field of metal products, metal processing and other areas that utilise metals. Previously used compounds utilizing hexavalent chromium were amongst the most effective materials for corrosion protection but regulations have been recently introduced that forbid their use. Consequently, there is a huge drive by engineers, technologists and scientists from different disciplines focused on searching a new, more effective and environmentally-friendly means of corrosion protection. One novel group of materials with the potential to solve metal protection problems are sol-gel thin films, which are increasingly interesting as mitigation corrosion barriers. These environmentally-friendly and easy-to-obtain coatings have the promise to be an effective alternative to hexavalent chromium compounds using for anti-corrosion industrial coatings. In this review the authors present a range of different solutions for slow down the corrosion processes of metallic substrates by using the oxides and doped oxides obtained by the sol-gel method. Examples of techniques used to the sol-gel coating examinations, in terms of anti-corrosion protection, are also presented.

  7. Functionalizable Sol-Gel Silica Coatings for Corrosion Mitigation.

    Science.gov (United States)

    Gąsiorek, Jolanta; Szczurek, Anna; Babiarczuk, Bartosz; Kaleta, Jerzy; Jones, Walis; Krzak, Justyna

    2018-01-26

    Corrosion is constantly a major problem of the world economy in the field of metal products, metal processing and other areas that utilise metals. Previously used compounds utilizing hexavalent chromium were amongst the most effective materials for corrosion protection but regulations have been recently introduced that forbid their use. Consequently, there is a huge drive by engineers, technologists and scientists from different disciplines focused on searching a new, more effective and environmentally-friendly means of corrosion protection. One novel group of materials with the potential to solve metal protection problems are sol-gel thin films, which are increasingly interesting as mitigation corrosion barriers. These environmentally-friendly and easy-to-obtain coatings have the promise to be an effective alternative to hexavalent chromium compounds using for anti-corrosion industrial coatings. In this review the authors present a range of different solutions for slow down the corrosion processes of metallic substrates by using the oxides and doped oxides obtained by the sol-gel method. Examples of techniques used to the sol-gel coating examinations, in terms of anti-corrosion protection, are also presented.

  8. RESIDUAL TLC SILICA GEL: RECUPERATION PROCESS, CHARACTERIZATION AND APPLICATION.

    Directory of Open Access Journals (Sweden)

    Maria Alexsandra de Sousa Rios

    2017-06-01

    Full Text Available A utilização de sílica gel de forma intensiva em laboratórios químicos tem um custo elevado, e gera uma quantidade significativa de resíduos sólidos contaminados com compostos orgânicos. Nesse sentido, a busca de métodos eficazes para reduzir os impactos que este material pode causar ao meio ambiente, tem sido um fator de motivação para muitos pesquisadores, uma vez que a sua utilização tem crescido bastante no segmento de pesquisa científica. Assim, o presente trabalho apresenta o processo de recuperação, caracterização e aplicação do gel de sílica 60G, um adsorvente usado na preparação de Cromatografia de Camada Fina. De acordo com os resultados, o método proposto foi capaz de recuperar o gel de sílica residual, tornando-se possível, para ser reutilizado no processo de separação e/ou purificação de compostos orgânicos de um modo prático e com um impacto ambiental reduzido.

  9. Persistent superhydrophilicity of sol-gel derived nanoporous silica thin films

    International Nuclear Information System (INIS)

    Ganjoo, S; Azimirad, R; Akhavan, O; Moshfegh, A Z

    2009-01-01

    In this investigation, sol-gel synthesized nanoporous silica thin films, annealed at different temperatures, with long time superhydrophilic property have been studied. Two kinds of sol-gel silica thin films were fabricated by dip-coating of glass substrates in two different solutions; with low and high water. The transparent coated films were dried at 100 deg. C and then annealed in a temperature range of 200-500 deg. C. The average water contact angle of the silica films prepared with low water content and annealed at 300 deg. C measured about 5 deg. for a long time (6 months) without any UV irradiation. Instead, adding water into the sol resulted in silica films with an average water contact angle greater than 60 deg. Atomic force microscopic analysis revealed that the silica films prepared with low water had a rough surface (∼30 nm), while the films prepared with high water had a smoother surface (∼2 nm). Using x-ray photoelectron spectroscopy, we have shown that with a decrease in the surface water on the film, its hydrophilicity increases logarithmically.

  10. Nanostructural control of the release of macromolecules from silica sol–gels

    Science.gov (United States)

    Radin, Shula; Bhattacharyya, Sanjib; Ducheyne, Paul

    2013-01-01

    The therapeutic use of biological molecules such as growth factors and monoclonal antibodies is challenging in view of their limited half-life in vivo. This has elicited the interest in delivery materials that can protect these molecules until released over extended periods of time. Although previous studies have shown controlled release of biologically functional BMP-2 and TGF-β from silica sol–gels, more versatile release conditions are desirable. This study focuses on the relationship between room temperature processed silica sol–gel synthesis conditions and the nanopore size and size distribution of the sol–gels. Furthermore, the effect on release of large molecules with a size up to 70 kDa is determined. Dextran, a hydrophilic polysaccharide, was selected as a large model molecule at molecular sizes of 10, 40 and 70 kDa, as it enabled us to determine a size effect uniquely without possible confounding chemical effects arising from the various molecules used. Previously, acid catalysis was performed at a pH value of 1.8 below the isoelectric point of silica. Herein the silica synthesis was pursued using acid catalysis at either pH 1.8 or 3.05 first, followed by catalysis at higher values by adding base. This results in a mesoporous structure with an abundance of pores around 3.5 nm. The data show that all molecular sizes can be released in a controlled manner. The data also reveal a unique in vivo approach to enable release of large biological molecules: the use more labile sol–gel structures by acid catalyzing above the pH value of the isoelectric point of silica; upon immersion in a physiological fluid the pores expand to reach an average size of 3.5 nm, thereby facilitating molecular out-diffusion. PMID:23643607

  11. Polyethyleneimine-loaded bimodal porous silica as low-cost and high-capacity sorbent for CO{sub 2} capture

    Energy Technology Data Exchange (ETDEWEB)

    Witoon, Thongthai, E-mail: fengttwi@ku.ac.th [National Center of Excellence for Petroleum, Petrochemicals and Advance Material, Department of Chemical Engineering, Faculty of Engineering, Kasetsart University, Bangkok 10900 (Thailand); Center for Advanced Studies in Nanotechnology and Its Applications in Chemical Food and Agricultural Industries, Kasetsart University, Bangkok 10900 (Thailand)

    2012-11-15

    In this work, bimodal (meso-macro) porous silicas with different mesopore diameters synthesized by using rice husk ash as a low-cost silica source and chitosan as a natural template were used as a polyethyleneimine (PEI) support for CO{sub 2} capture. Unimodal porous silica supports with equivalent mesopore diameters to bimodal porous silica supports have been prepared for purpose of comparison. Effects of different PEI contents (10, 20, 30, 40 and 50 wt%) on CO{sub 2} sorption capacity have been systematically investigated. The porous silica supports and the PEI-loaded porous silica supports were characterized by N{sub 2}-sorption analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and thermal gravimetric analysis. CO{sub 2} sorption measurements of all PEI-loaded porous silica supports were performed at different adsorption temperatures (60, 75, 85, 90, 95 and 105 Degree-Sign C). At low PEI contents (10-20 wt%), the CO{sub 2} sorption of all adsorbents was found to decrease as a function of adsorption temperature, which was a characteristic of a thermodynamically-controlled regime. A transition from the thermodynamically-controlled regime to a kinetically-controlled regime was found when the PEI content was increased up to 30 wt% for PEI-loaded unimodal porous silicas and 40 wt% for PEI-loaded bimodal porous silicas. At high PEI contents (40-50 wt%), the CO{sub 2} capturing efficiency of the PEI-loaded bimodal porous silicas was found to be considerably greater than that of the PEI-loaded unimodal porous silicas, indicating that most of the amine groups of PEI molecules loaded on the unimodal porous silica supports was useless, and thus the appeared macroporosity of the bimodal porous silica supports could provide a higher effective amine density to adsorb CO{sub 2}. Highlights: Black-Right-Pointing-Pointer PEI-impregnated bimodal porous silica as low-cost sorbent for CO{sub 2} capture. Black-Right-Pointing-Pointer Macropores enhances

  12. Sol-gel Derived Warfarin - Silica Composites for Controlled Drug Release.

    Science.gov (United States)

    Dolinina, Ekaterina S; Parfenyuk, Elena V

    2017-01-01

    Warfarin, commonly used anticoagulant in clinic, has serious shortcomings due to its unsatisfactory pharmacodynamics. One of the efficient ways for the improvement of pharmacological and consumer properties of drugs is the development of optimal drug delivery systems. The aim of this work is to synthesize novel warfarin - silica composites and to study in vitro the drug release kinetics to obtain the composites with controlled release. The composites of warfarin with unmodified (UMS) and mercaptopropyl modified silica (MPMS) were synthesized by sol-gel method. The composite formation was confirmed by FTIR spectra. The concentrations of warfarin released to media with pH 1.6, 6.8 and 7.4 were measured using UV spectroscopy. The drug release profiles from the solid composites were described by a series of kinetic models which includes zero order kinetics, first order kinetics, the modified Korsmeyer-Peppas model and Hixson-Crowell model. The synthesized sol-gel composites have different kinetic behavior in the studied media. In contrast to the warfarin composite with unmodified silica, the drug release from the composite with mercaptopropyl modified silica follows zero order kinetics for 24 h irrespective to the release medium pH due to mixed mechanism (duffusion + degradation and/or disintegration of silica matrix). The obtained results showed that warfarin - silica sol-gel composites have a potential application for the development of novel oral formulation of the drug with controlled delivery. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  13. Ternary Phase-Separation Investigation of Sol-Gel Derived Silica from Ethyl Silicate 40

    Science.gov (United States)

    Wang, Shengnan; Wang, David K.; Smart, Simon; Diniz da Costa, João C.

    2015-01-01

    A ternary phase-separation investigation of the ethyl silicate 40 (ES40) sol-gel process was conducted using ethanol and water as the solvent and hydrolysing agent, respectively. This oligomeric silica precursor underwent various degrees of phase separation behaviour in solution during the sol-gel reactions as a function of temperature and H2O/Si ratios. The solution composition within the immiscible region of the ES40 phase-separated system shows that the hydrolysis and condensation reactions decreased with decreasing reaction temperature. A mesoporous structure was obtained at low temperature due to weak drying forces from slow solvent evaporation on one hand and formation of unreacted ES40 cages in the other, which reduced network shrinkage and produced larger pores. This was attributed to the concentration of the reactive sites around the phase-separated interface, which enhanced the condensation and crosslinking. Contrary to dense silica structures obtained from sol-gel reactions in the miscible region, higher microporosity was produced via a phase-separated sol-gel system by using high H2O/Si ratios. This tailoring process facilitated further condensation reactions and crosslinking of silica chains, which coupled with stiffening of the network, made it more resistant to compression and densification. PMID:26411484

  14. Gamma ray irradiation induced optical band gap variations in silica sol-gel doped sucrose

    International Nuclear Information System (INIS)

    Marzouki, F.; Farah, K.; Hamzaoui, A.H; Ben Ouada, H

    2015-01-01

    The silica xerogels doped sucrose was prepared via sol-gel process and exposed at room temperature to different doses of high energy ("6"0Co) gamma irradiation. Changes in the UV-visible and FTIR spectra of pristine and irradiated xerogels with varying of gamma doses rays show variation in the gap energy. It was found that energy gap of the investigated silica xerogels decreases with increasing the gamma irradiation doses. Thereby the irradiated samples reveal behaviour changes, from an insulator (Eg ∼5,8 eV) towards a semiconductor with (Eg ∼ 3.5 eV).

  15. Gas-phase acylation of aminopropyl-silica gel in the synthesis of some chemically bonded silica materials for analytical applications

    International Nuclear Information System (INIS)

    Basiuk, Vladimir; Khil'chevskaya, E.G.

    1991-01-01

    Gas-phase acylation of aminopropyl-silica gel with aliphatic dicarboxylic (succinic, adipic and sebacic) and 4-aminobenzoic acids is proposed as a rapid and efficient one-step method for the synthesis of carboxyalkyl- and 4-aminophenylamidopropyl-silica gels, usually used as zwitterion exchangers for liquid chromatography and matrices for multi-step syntheses of silica-bound aromatic azo reagents for the sorption and chromatographic separation of metal ions. Acylation degrees of 59-90% are achieved after 0.5 h. IR spectra of the acylation products and near-UV-visible spectra for bonded aromatic azo compounds, based on 4-aminobenzamidopropyl-silica gel, are presented. Some positive and negative aspects of the gas-phase acylation are discussed. (author). 34 refs.; 2 figs.; 2 tabs

  16. Synthesis of biocompatible hydrophobic silica-gelatin nano-hybrid by sol-gel process.

    Science.gov (United States)

    Smitha, S; Shajesh, P; Mukundan, P; Nair, T D R; Warrier, K G K

    2007-03-15

    Silica-biopolymer hybrid has been synthesised using colloidal silica as the precursor for silica and gelatin as the biopolymer counterpart. The surface modification of the hybrid material has been done with methyltrimethoxysilane leading to the formation of biocompatible hydrophobic silica-gelatin hybrid. Here we are reporting hydrophobic silica-gelatin hybrid and coating precursor for the first time. The hybrid gel has been evaluated for chemical modification, thermal degradation, hydrophobicity, particle size, transparency under the UV-visible region and morphology. FTIR spectroscopy has been used to verify the presence of CH(3) groups which introduce hydrophobicity to the SiO2-MTMS-gelatin hybrids. The hydrophobic property has also been tailored by varying the concentration of methyltrimethoxysilane. Contact angle by Wilhelmy plate method of transparent hydrophobic silica-gelatin coatings has been found to be as high as approximately 95 degrees . Oxidation of the organic group which induces the hydrophobic character occurs at 530 degrees C which indicates that the surface hydrophobicity is retained up to that temperature. Optical transmittance of SiO2-MTMS-gelatin hybrid coatings on glass substrates has been found to be close to 100% which will enable the hybrid for possible optical applications and also for preparation of transparent biocompatible hydrophobic coatings on biological substrates such as leather.

  17. Synthesis of mesoporous silica nanoparticles by sol–gel as nanocontainer for future drug delivery applications

    Energy Technology Data Exchange (ETDEWEB)

    Vazquez, N.I.; Gonzalez, Z.; Ferrari, B.; Castro, Y.

    2017-07-01

    Development of mesoporous silica nanoparticles as carriers for drug delivery systems has increased exponentially during the last decade. The present work is focused on the synthesis of silica carriers by sol–gel from tetraethyl orthosilicate (TEOS) as precursor of silica and cetyltrimethylammonium bromide (CTAB) as pore generating agent. The synthesis conditions were modified varying the molar ratio of water/TEOS, NH3/TEOS and amount of CTAB. The silica particles were characterized by scan electron microscopy techniques (FESEM), high resolution transmission electron microscopy (HR-TEM), N2 adsorption–desorption isotherms, Zeta-potential and Dynamic Light Scattering (DLS). The results show that the specific surface area and the porosity of silica particles were strongly affected by the addition of CTAB and the amount of H2O. The dispersion and stability of silica mesoporous particles is achieved in spite of the high surface reactivity. The synthesis formulation affects considerably to the particle morphology, which changes from spheres to rods when the molar ratio of H2O increases. A maximum specific surface area of 1480m2/g was obtained with pore sizes ranging 2.5–2.8nm. (Author)

  18. Synthesis of Silica Nanoparticles by Sol-Gel: Size-Dependent Properties, Surface Modification, and Applications in Silica-Polymer Nano composites-A Review

    International Nuclear Information System (INIS)

    Ismail, A.R.; Vejayakumaran, P.

    2012-01-01

    Application of silica nanoparticles as fillers in the preparation of nano composite of polymers has drawn much attention, due to the increased demand for new materials with improved thermal, mechanical, physical, and chemical properties. Recent developments in the synthesis of monodispersed, narrow-size distribution of nanoparticles by sol-gel method provide significant boost to development of silica-polymer nano composites. This paper is written by emphasizing on the synthesis of silica nanoparticles, characterization on size-dependent properties, and surface modification for the preparation of homogeneous nano composites, generally by sol-gel technique. The effect of nano silica on the properties of various types of silica-polymer composites is also summarized.

  19. Organically Modified Silica with Pyrazole-3-carbaldehyde as a New Sorbent for Solid-Liquid Extraction of Heavy Metals

    Directory of Open Access Journals (Sweden)

    Smaail Radi

    2013-12-01

    Full Text Available A new chelating matrix, SiNP, has been prepared by immobilizing 1.5-dimethyl-1H-pyrazole-3-carbaldehyde on silica gel modified with 3-aminopropyl-trimethoxysilane. This new chelating material was well characterized by elemental analysis, FT-IR spectroscopy, cross polarization magic angle spinning solid state 13C-NMR, nitrogen adsorption-desorption isotherm, BET surface area, BJH pore size, and scanning electron microscopy (SEM. The new product exhibits good chemical and thermal stability as determined by thermogravimetry curves (TGA. The new prepared material was used as an adsorbent for the solid-phase extraction (SPE of Pb(II, Cd(II, Cu(II and Zn(II from aqueous solutions using a batch method, prior to their determination by flame atomic adsorption spectrometry. The adsorption capacity was investigated using kinetics and pH effects. Common coexisting ions did not interfere with separation and determination.

  20. Synthesis and characterization of uniform silica nanoparticles on nickel substrate by spin coating and sol-gel method

    Science.gov (United States)

    Ngoc Thi Le, Hien; Jeong, Hae Kyung

    2014-01-01

    Spin coating and sol-gel methods are proposed for the preparation of silica nanoparticles on a nickel substrate using silicon tetrachloride, 2-methoxyethanol, and four different types of alkaline solutions. The effects of the type of alkaline solution, concentration of silica solution, and speed of spin coating on the properties of silica nanoparticles are investigated systematically. Uniform spherical shape of silica nanoparticles on Ni with the smallest size are obtained with sodium carbonate among the alkaline solutions after stirring at 70 °C for 6 h and spin-coating at 7000 rpm. Physical and electrochemical properties of the silica particles are investigated.

  1. Stability of inorganic mercury and methylmercury on yeast-silica gel microcolumns: field sampling capabilities

    Energy Technology Data Exchange (ETDEWEB)

    Perez-Corona, M. [Universidad Complutense de Madrid (Spain). Dept. de Quimica Analitica

    2000-11-01

    The stability of methylmercury and inorganic mercury retained on yeast-silica gel microcolumns was established and compared with the stability of these species in solution. Yeast-silica gel columns with the retained analytes were stored for two months at three different temperatures: -20 C, 4 C and room temperature. At regular time intervals, both mercury species were eluted and quantified by cold vapor atomic absorption spectrometry (CVAAS). Methylmercury was found stable in the columns over the two-month period at the three different temperatures tested while the concentration of inorganic mercury decreased after one week's storage even at -20 C. These results are of great interest since the use of these microcolumns allows the preconcentration and storage of mercury species until analysis, thus saving laboratory space and avoiding the problems associated with maintaining species integrity in aqueous solution. (orig.)

  2. Thin layer chromatography of glucose and sorbitol on Cu(II)-impregnated silica gel plates

    Energy Technology Data Exchange (ETDEWEB)

    Hadzija, O. (Ruder Boskovic Inst., Zagreb (Croatia)); Spoljar, B. (Ruder Boskovic Inst., Zagreb (Croatia)); Sesartic, L. (Inst. of Immunology, Zagreb (Croatia))

    1994-04-01

    A thin-layer chromatographic (TLC) separation of glucose and sorbitol on CU(II)-impregnated silica gel plates with n-propanol: Water (4:1) v/v as developer and potassium permanganate as detecting reagent has been worked out. The new impregnant is completely insoluble in water and thus enables the use of an aqueous developer. The R[sub f]-values are 55 and 10 for glucose and sorbitol, respectively. (orig.)

  3. Analysis of sorption into single ODS-silica gel microparticles in acetonitrile-water.

    Science.gov (United States)

    Nakatani, Kiyoharu; Kakizaki, Hiroshi

    2003-08-01

    Intraparticle mass transfer processes of Phenol Blue (PB) in single octadecylsilyl (ODS)-silica gel microparticles in acetonitrile-water were analyzed by microcapillary manipulation and microabsorption methods. An absorption maximum of PB, the sorption isotherm parameters, and the sorption rate in the microparticle system were highly dependent on the percentage of acetonitrile in solution. The results are discussed in terms of the microscopic polarity surrounding PB in the ODS phase and the relationship between the isotherm parameters and the sorption rate.

  4. Sol-gel-derived mesoporous silica films with low dielectric constants

    Energy Technology Data Exchange (ETDEWEB)

    Seraji, S.; Wu, Yun; Forbess, M.; Limmer, S.J.; Chou, T.; Cao, Guozhong [Washington Univ., Seattle, WA (United States). Dept. of Materials Science and Engineering

    2000-11-16

    Mesoporous silica films with low dielectric constants and possibly closed pores have been achieved with a multiple step sol-gel processing technique. Crack-free films with approximately 50% porosity and 0.9 {mu}m thicknesses were obtained, a tape-test revealing good adhesion between films and substrates or metal electrodes. Dielectric constants remained virtually unchanged after aging at room temperature at 56% humidity over 6 days. (orig.)

  5. Thermodynamics of the Sorption of Benzimidazoles on Octadecyl Silica Gel from Water-Methanol Eluents

    Science.gov (United States)

    Shafigulin, R. V.; Bulanova, A. V.

    2018-02-01

    The standard enthalpy and entropy component of transferring benzimidazoles from water-methanol solutions to surfaces of octadecyl silica gel are determined using reversed-phase high-performance liquid chromatography (RP HPLC). The dependences between the enthalpy and polarizability of the molecules of the studied benzimidazoles, the enthalpy and the entropy factor are studied, and the influence of the quantitative composition of the water-methanol solution on the enthalpy are studied.

  6. Development of fluorocarbon/silica composites via sol/gel process

    International Nuclear Information System (INIS)

    Ferreira, Max P.; Maria, Daniel A.; Gomes, Luiza M.F.

    2009-01-01

    Fluorocarbon/silica composites have interesting physical-chemical properties, combining the great resistance to chemical products, the electric insulation, and the thermal stability of fluorine polymers with the optical, magnetic, and dielectric properties of silica. Due to the unique mechanical, thermal, and dielectric properties of fluorocarbon and silica composites, there is interest in their application in the development of fuel cells, the production of integrated circuit boards (ICB), and packages for the transportation of integrated circuits. The sol-gel process is a chemical route to prepare ceramic materials with specific properties that are hard or impossible to obtain by conventional methods. Fluorocarbon/silica composites were obtained by the sol-gel method from tetramethoxysilane - TMOS and fluorinated hydrocarbons with low molecular weight and main chains with 10 - 20 carbon atoms previously obtained from PTFE scraps irradiated with a 60 Co γ source in oxygen atmosphere with a dose of 1 MGy. Syntheses were performed in 125-mL reaction flasks in basic medium at 35 deg C and in acid medium at 60 deg C with N-N dimethylformamide as a chemical additive for drying control. After synthesis, the material was thermally treated in an oven with electronic temperature control. The monoliths obtained were characterized by Fourier transform infrared spectroscopy (FTIR), electron microprobe and by a standard nitrogen adsorption-desorption technique. (author)

  7. The carbonaceous sorbent based on the secondary silica-containing material from oil extraction industry

    Science.gov (United States)

    Starostina, I. V.; Stolyarov, D. V.; Anichina, Ya N.; Porozhnyuk, E. V.

    2018-01-01

    The object of research in this work is the silica-containing waste of oil extraction industry - the waste kieselghur (diatomite) sludge from precoat filtering units, used for the purification of vegetable oils from organic impurities. As a result of the thermal modification of the sludge, which contains up to 70% of organic impurities, a finely-dispersed low-porous carbonaceous mineral sorption material is formed. The modification of the sludge particles surface causes the substantial alteration of its physical, chemical, adsorption and structural properties - the organic matter is charred, the particle size is reduced, and on the surface of diatomite particles a carbon layer is formed, which deposits in macropores and partially occludes them. The amount of mesopores is increased, along with the specific surface of the obtained product. The optimal temperature of sludge modification is 500°C. The synthesized carbonaceous material can be used as an adsorbing agent for the purification of wastewater from heavy metal ions. The sorption capacity of Cu2+ ions amounted to 14.2 mg·g-1 and for Ni2+ ions - 17.0 mg·g-1. The obtained values exceed the sorption capacity values of the initial kieselghur, used as a filtering charge, for the researched metal ions.

  8. Sol-gel derived flexible silica aerogel as selective adsorbent for water decontamination from crude oil.

    Science.gov (United States)

    Abolghasemi Mahani, A; Motahari, S; Mohebbi, A

    2018-04-01

    Oil spills are the most important threat to the sea ecosystem. The present study is an attempt to investigate the effects of sol-gel parameters on seawater decontamination from crude oil by use of flexible silica aerogel. To this goal, methyltrimethoxysilane (MTMS) based silica aerogels were prepared by two-step acid-base catalyzed sol-gel process, involving ambient pressure drying (APD) method. To investigate the effects of sol-gel parameters, the aerogels were prepared under two different acidic and basic pH values (i.e. 4 and 8) and varied ethanol/MTMS molar ratios from 5 to 15. The adsorption capacity of the prepared aerogels was evaluated for two heavy and light commercial crude oils under multiple adsorption-desorption cycles. To reduce process time, desorption cycles were carried out by using roll milling for the first time. At optimum condition, silica aerogels are able to uptake heavy and light crude oils with the order of 16.7 and 13.7, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Immobilization of Beauveria bassiana Lipase on Silica Gel by Physical Adsorption

    Directory of Open Access Journals (Sweden)

    Vanessa Hitomi Sugahara

    2014-12-01

    Full Text Available Extracellular lipase from Beauveria bassianastrain CG481 was immobilized by using thirteen different immobilization protocols. Silica gel was chosen as the most suitable adsorbent with 94.8% of activity yield. The adsorption on silica gel did not change the optimum pH (8.5 and temperature (45ºC values of the free lipase (FL for lipolytic activity, and it showed higher activities in extreme conditions (pH 9.0 to 10.5, 60ºC. The lipase immobilized on silica gel (ILS showed enhanced stability at pH 7.0 after 120 h incubation (69.0% when compared to FL (33.3%. The thermal stability was also enhanced by immobilization at 60ºC in aqueous (64.6% and organic medium (95.1%, while FL showed only 40.6% of residual activity in aqueous medium and exhibited no activity for esterification reaction in n-heptane. The treatment of ILS with 0.8 M NaCl prevented lipase desorption while Triton X-100 (0.1% resulted the enzyme leakage. The ILS was reused for four times for esterification reaction with 80.8% of initial activity.

  10. Phase equilibria and thermodynamic modeling of ethane and propane hydrates in porous silica gels.

    Science.gov (United States)

    Seo, Yongwon; Lee, Seungmin; Cha, Inuk; Lee, Ju Dong; Lee, Huen

    2009-04-23

    In the present study, we examined the active role of porous silica gels when used as natural gas storage and transportation media. We adopted the dispersed water in silica gel pores to substantially enhance active surface for contacting and encaging gas molecules. We measured the three-phase hydrate (H)-water-rich liquid (L(W))-vapor (V) equilibria of C(2)H(6) and C(3)H(8) hydrates in 6.0, 15.0, 30.0, and 100.0 nm silica gel pores to investigate the effect of geometrical constraints on gas hydrate phase equilibria. At specified temperatures, the hydrate stability region is shifted to a higher pressure region depending on pore size when compared with those of bulk hydrates. Through application of the Gibbs-Thomson relationship to the experimental data, we determined the values for the C(2)H(6) hydrate-water and C(3)H(8) hydrate-water interfacial tensions to be 39 +/- 2 and 45 +/- 1 mJ/m(2), respectively. By using these values, the calculation values were in good agreement with the experimental ones. The overall results given in this study could also be quite useful in various fields, such as exploitation of natural gas hydrate in marine sediments and sequestration of carbon dioxide into the deep ocean.

  11. Comparison of optical properties of Eu3+ ions in the silica gel glasses obtained by different preparation techniques

    International Nuclear Information System (INIS)

    Legendziewicz, J.; Sokolnicki, J.; Keller, B.; Borzechowska, M.; Strek, W.

    1996-01-01

    Silica-gel glasses doped with Eu 3+ ions were obtained by different preparation techniques. The absorption, emission and excitation spectra of the obtained glasses were measured in the range of 77-300 K. The energy levels diagrams of Eu 3+ ions were derived. An intensity analysis of f-f transitions was performed. In particular, polymeric structure behaviour of europium compounds entrapped in silica gel glasses was temperature controlled during the preparation of glasses. Their optical properties were investigated. (author)

  12. sup(60)Co hot atom chemistry of tris(acetylacetonato) cobalt(III) adsorbed on silica gel

    International Nuclear Information System (INIS)

    Nishioji, H.; Sakai, Y.; Tominaga, T.

    1985-01-01

    The sup(60)Co hot atom reactions were studied in tris(acetylacetonato)cobalt(III) adsorbed on silica gel surface. sup(57)Fe Moessbauer spectra of tris(acetylacetonato)iron(III) in the corresponding system were also measured in order to examine the state of dispersion of complex molecules on silica gel. The retention formation processes were discussed in terms of the dependence of sup(60)Co retention on the adsorbed amount (concentration) of cobalt(III) complexes. (author)

  13. Graphene-Derivatized Silica Composite as Solid-Phase Extraction Sorbent Combined with GC–MS/MS for the Determination of Polycyclic Musks in Aqueous Samples

    Directory of Open Access Journals (Sweden)

    Cheng Li

    2018-02-01

    Full Text Available Polycyclic musks (PCMs have recently received growing attention as emerging contaminants because of their bioaccumulation and potential ecotoxicological effects. Herein, an effective method for the determination of five PCMs in aqueous samples is presented. Reduced graphene oxide-derivatized silica (rGO@silica particles were prepared from graphene oxide and aminosilica microparticles and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. PCMs were preconcentrated using rGO@silica as the solid-phase extraction sorbent and quantified by gas chromatography–tandem mass spectrometry. Several experimental parameters, such as eluent, elution volume, sorbent amount, pH, and sample volume were optimized. The correlation coefficient (R ranged from 0.9958 to 0.9992, while the limits of detection and quantitation for the five PCMs were 0.3–0.8 ng/L and 1.1–2.1 ng/L, respectively. Satisfactory recoveries were obtained for tap water (86.6–105.9% and river water samples (82.9–107.1%, with relative standard deviations <10% under optimal conditions. The developed method was applied to analyze PCMs in tap and river water samples from Beijing, China. Galaxolide (HHCB and tonalide (AHTN were the main PCM components detected in one river water sample at concentrations of 18.7 for HHCB, and 11.7 ng/L for AHTN.

  14. The influence of white and blue silica gels as adsorbents in adsorptive-distillation of ethanol-water mixture

    Science.gov (United States)

    Megawati, Jannah, Reni Ainun; Rahayuningtiyas, Indi

    2017-01-01

    This research studied the difference of white and blue silica gels when used as an adsorbent for ethanol purification that is processed via Adsorptive-Distillation (AD) at 1 atm pressure. The effect of process duration to purification process is also recorded and studied to evaluate the performance of designed AD equipment. The experiment was conducted using boiling flask covered with a heating mantle and the temperature was maintained at 78°C. The vapour flowed into the adsorbent column and was condensed using water as a cooling medium. The initial ethanol concentration was 90.8% v/v and volume was 300 mL. Experiment shows that designed AD equipment could be used to purify ethanol. The average vapour velocity was about 39.29 and 45.91 m/s for white and blue silica gels, respectively, which is considered very high. Therefore the saturated adsorption could not be obtained. Highest ethanol concentration achieved using white silica gel is about 96.671% v/v after 50 minutes. Thus AD with white silica gel showed good performance and passed azeotropic point. But AD with blue silica gel showed a different result, the adsorption of blue silica gel failed to break the azeotropic point. The outlet average water concentration for white and blue silica gels is 3.54 and 3.42 mole/L. Based on the weight ratio of adsorbed water per adsorbent, at 55th minutes of time; this ratio of blue silica gel is about 0.053 gwater/gads. The time required by the blue silica to achieve 0.5 wwater-adsorbed/wwater-initial is 45 minutes, and the average outlet water concentration is 3.42 mole/L. Meanwhile, the time required by a white silica to complete 0.5 wwater-adsorbed/wwater-initial is 35 minutes, and the average outlet water level is 3.54 mole/L. Based on the results, the blue silica as an adsorbent for AD of ethanol-water mixture is better than white silica gel.

  15. Evaluation of 137Cs sorbents for fixation in concrete

    International Nuclear Information System (INIS)

    Plodinec, M.J.

    1976-01-01

    As part of the long-term waste management program at the Savannah River Laboratory, several 137 Cs sorbents were evaluated for incorporation into concrete. The sorbents studied were: Linde AW-300, AW-500, 13-X, and SK-40; Norton Zeolon 200, 500, and 900; clinoptilolite; and vermiculite. The parameters studied were sorption kinetics, leachability, and compressive strength of the concrete. The best sorbents identified were Linde AW-500 and Norton Zeolon 900. In all tests, these two sorbents performed almost identically; sorption kinetics were acceptable; both strengthened the concrete, and both gave relatively leach-resistant concrete. Vermiculite that had been heated to collapse its lattice around 137 Cs gave the most leach-resistant concrete. However, it sorbed cesium slowly, and the resulting concrete was very weak. When silica gel was added to concrete to react with free calcium, the addition had no effect on cesium leachability

  16. Thickness controlled sol-gel silica films for plasmonic bio-sensing devices

    Energy Technology Data Exchange (ETDEWEB)

    Figus, Cristiana, E-mail: cristiana.figus@dsf.unica.it; Quochi, Francesco, E-mail: cristiana.figus@dsf.unica.it; Artizzu, Flavia, E-mail: cristiana.figus@dsf.unica.it; Saba, Michele, E-mail: cristiana.figus@dsf.unica.it; Marongiu, Daniela, E-mail: cristiana.figus@dsf.unica.it; Mura, Andrea; Bongiovanni, Giovanni [Dipartimento di Fisica - University of Cagliari, S.P. Km 0.7, I-09042 Monserrato (Canada) (Italy); Floris, Francesco; Marabelli, Franco; Patrini, Maddalena; Fornasari, Lucia [Dipartimento di Fisica - University of Pavia, Via Agostino Bassi 6, I-27100 Pavia (PV) (Italy); Pellacani, Paola; Valsesia, Andrea [Plasmore S.r.l. -Via Grazia Deledda 4, I-21020 Ranco (Vatican City State, Holy See) (Italy)

    2014-10-21

    Plasmonics has recently received considerable interest due to its potentiality in many fields as well as in nanobio-technology applications. In this regard, various strategies are required for modifying the surfaces of plasmonic nanostructures and to control their optical properties in view of interesting application such as bio-sensing, We report a simple method for depositing silica layers of controlled thickness on planar plasmonic structures. Tetraethoxysilane (TEOS) was used as silica precursor. The control of the silica layer thickness was obtained by optimizing the sol-gel method and dip-coating technique, in particular by properly tuning different parameters such as pH, solvent concentration, and withdrawal speed. The resulting films were characterized via atomic force microscopy (AFM), Fourier-transform (FT) spectroscopy, and spectroscopic ellipsometry (SE). Furthermore, by performing the analysis of surface plasmon resonances before and after the coating of the nanostructures, it was observed that the position of the resonance structures could be properly shifted by finely controlling the silica layer thickness. The effect of silica coating was assessed also in view of sensing applications, due to important advantages, such as surface protection of the plasmonic structure.

  17. Synthesis of palladium-doped silica nanofibers by sol-gel reaction and electrospinning process

    Energy Technology Data Exchange (ETDEWEB)

    San, Thiam Hui; Daud, Wan Ramli Wan; Kadhum, Abdul Amir Hassan; Mohamad, Abu Bakar; Kamarudin, Siti Kartom; Shyuan, Loh Kee; Majlan, Edy Herianto [Fuel Cell Institute, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor (Malaysia); Fuel Cell Institute, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia and Department of Chemical and Process Engineering, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor (Malaysia); Fuel Cell Institute, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor (Malaysia)

    2012-06-29

    Nanofiber is drawing great attention nowadays with their high surface area per volume and flexibility in surface functionalities that make them favorable as a proton exchange membrane in fuel cell application. In this study, incorporation of palladium nanoparticles in silica nanofibers was prepared by combination of a tetraorthosilane (TEOS) sol-gel reaction with electrospinning process. This method can prevent the nanoparticles from aggregation by direct mixing of palladium nanoparticles in silica sol. The as-produced electrospun fibers were thermally treated to remove poly(vinyl pyrrolidone) (PVP) and condensation of silanol in silica framework. PVP is chosen as fiber shaping agent because of its insulting and capping properties for various metal nanoparticles. Scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the silica fibers and Pd nanoparticles on the fibers. Spun fibers with average diameter ranged from 100nm to 400nm were obtained at optimum operating condition and distribution of Pd nanoparticles on silica fibers was investigated.

  18. Adsorption Characteristics of Water and Silica Gel System for Desalination Cycle

    KAUST Repository

    Cevallos, Oscar R.

    2012-07-01

    An adsorbent suitable for adsorption desalination cycles is essentially characterized by a hydrophilic and porous structure with high surface area where water molecules are adsorbed via hydrogen bonding mechanism. Silica gel type A++ possesses the highest surface area and exhibits the highest equilibrium uptake from all the silica gels available in the market, therefore being suitable for water desalination cycles; where adsorbent’s adsorption characteristics and water vapor uptake capacity are key parameters in the compactness of the system; translated as feasibility of water desalination through adsorption technologies. The adsorption characteristics of water vapor onto silica gel type A++ over a temperature range of 30 oC to 60 oC are investigated in this research. This is done using water vapor adsorption analyzer utilizing a constant volume and variable pressure method, namely the Hydrosorb-1000 instrument by Quantachrome. The experimental uptake data is studied using numerous isotherm models, i. e. the Langmuir, Tóth, generalized Dubinin-Astakhov (D-A), Dubinin-Astakhov based on pore size distribution (PSD) and Dubinin-Serpinski (D-Se) isotherm for the whole pressure range, and for a pressure range below 10 kPa, proper for desalination cycles; isotherms type V of the International Union of Pure and Applied Chemistry (IUPAC) classification were exhibited. It is observed that the D-A based on PSD and the D-Se isotherm models describe the best fitting of the experimental uptake data for desalination cycles within a regression error of 2% and 6% respectively. All isotherm models, except the D-A based on PSD, have failed to describe the obtained experimental uptake data; an empirical isotherm model is proposed by observing the behavior of Tóth and D-A isotherm models. The new empirical model describes the water adsorption onto silica gel type A++ within a regression error of 3%. This will aid to describe the advantages of silica gel type A++ for the design of

  19. Quaternary ammonium-functionalized MCM-48 mesoporous silica as a sorbent for the dispersive solid-phase extraction of endocrine disrupting compounds in water.

    Science.gov (United States)

    Zhang, Shijuan; Lu, Fengli; Ma, Xiaoyun; Yue, Mingbo; Li, Yanxin; Liu, Jiammin; You, Jinmao

    2018-07-06

    MCM-48 mesoporous silica was functionalized with dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, a quaternary ammonium salt with a long hydrophobic chain, to prepare a new sorbent for the dispersive solid-phase extraction (DSPE) of seven endocrine disrupting compounds (EDCs) including 4-hexylphenol, 4-octylphenol, 4-nonylphenol, bisphenol A, estrone, 17β-estradiol and estriol in water. A series of differently functionalized MCM-48 materials were also synthesized, and they served as reference materials to study the mechanism. The developed DSPE method was combined with HPLC with fluorescence detection to evaluate the adsorption performance. The results indicated that the quaternary ammonium-functionalized MCM-48 mesoporous silica can be used as ideal sorbent for EDCs in water with recoveries of higher than 95% due to the electrostatic interactions and hydrophobic effect. Hydrogen bonding and π-π interactions in other synthesized materials could lead to about 25-30% increase in recoveries, but the results for polyhydroxy compounds were still not satisfying. The quaternary ammonium-functionalized MCM-48 mesoporous silica was successfully applied to the DSPE of EDCs in real water samples. The optimum extraction conditions were sorbent amount, 15 mg; desorption time; 5 min; elution volume, 0.8 mL; sample pH 3.0; and salt addition, 5 g/L. The limits of detection were in the range of 1.2-2.6 ng/L, while the limits of quantitation were in the range of 4.3-8.3 ng/L. Copyright © 2018 Elsevier B.V. All rights reserved.

  20. Adsorption of gaseous RuO4 by various sorbents. II

    International Nuclear Information System (INIS)

    Vujisic, L.; Nikolic, R.

    1983-01-01

    Sorption of gaseous RuO 4 on impregnated Alcoa Alumina H-151, impregnated charcoal, silica gel and HEPA filter was investigated. The results obtained on various sorbents are compared and discussed in connection with possibilities to use the chosen material in air cleaning systems

  1. Silica based gel as a potential waste form for high level waste from fuel reprocessing

    International Nuclear Information System (INIS)

    Ford, C.E.; Dempster, T.J.; Melling, P.J.

    1983-10-01

    To assess the feasibility of safe disposal of high-level radioactive waste as synthetic clay, or material that would react with ground water to form clay, experiments have been carried out to determine the hydrothermal crystallisation and leaching behaviour of silica based gels fired at 900 deg C. Crystallisation rates at a pressure of 500 bars and at temperatures below 400 deg C are negligible and this more or less precludes pre-disposal production of synthetic clay on the scale required. Leaching experiments suggest that the leach rates of Cs from gels by distilled water are higher than those of boro-silicate glasses and SYNROC at the lower temperatures that would be preferred for geological storage. However, amounts of bulk dissolution of gels may be lower than those of boro-silicate glasses. The initial leaching behaviour of gels might be considerably improved by hot compaction at 900 to 1000 deg C. Consideration of likely waste form dissolution behaviour in a repository environment suggests that gels of appropriate composition might perform as well as, or better than, boro-silicate glasses. A novel hypothetical plant is described that could produce the gel waste form on the scale required on a more or less continuous basis. (author)

  2. Effect of silica and water content on the glass transition of poly(ethylene glycol) monomethylether-silica gel-lithium perchlorate ormolytes

    International Nuclear Information System (INIS)

    Korwin, Rebecca S.; Masui, Hitoshi

    2005-01-01

    The effect of silica and water content on the glass transition temperature, T g , of MPEG2000-silica-LiClO 4 ormolytes was assessed by differential scanning calorimetry (DSC). The sol-gel synthesized ormolytes consisted of various amounts of poly(ethylene glycol) monomethylether (M.W. 2000 g/mol; i.e., MPEG2000) tethered to silica gel through the hydroxyl terminus via a urethane linkage. DSC features corresponding to physisorbed and hydrogen-bonded water, as well as the glass transition of the polyether, were identified. Both silica and LiClO 4 raise the T g and suppress crystallization of the polyether component. Water plasticizes the polyether and stoichiometrically solvates and sequesters Li + , thereby, lowering T g

  3. Preparation and use of chemically modified MCM-41 and silica gel as selective adsorbents for Hg(II) ions

    International Nuclear Information System (INIS)

    Puanngam, Mahitti; Unob, Fuangfa

    2008-01-01

    Adsorbents for Hg(II) ion extraction were prepared using amorphous silica gel and ordered MCM-41. Grafting with 2-(3-(2-aminoethylthio)propylthio)ethanamine was used to functionalize the silica. The functionalized adsorbents were characterized by nitrogen adsorption, X-ray diffraction, 13 C MAS NMR spectroscopy and thermogravimetric analysis. The adsorption properties of the modified silica gel and MCM-41 were compared using batch method. The effect of pH, stirring time, ionic strength and foreign ions were studied. The extraction of Hg(II) ions occurred rapidly with the modified MCM-41 and the optimal pH range for the extraction by the modified materials was pH 4-7. Foreign ions, especially Cl - had some effect on the extraction efficiency of the modified silica gel and the modified MCM-41. The adsorption behavior of both adsorbents could be described by a Langmuir model at 298 K, and the maximum adsorption capacity of the modified silica gel and MCM-41 at pH 3 was 0.79 and 0.70 mmol g -1 , respectively. The modified MCM-41 showed a larger Langmuir constant than that of the modified silica gel, indicating a better ability for Hg(II) ion adsorption. The results indicate that the structure of the materials affects the adsorption behavior. These materials show a potential for the application as effective and selective adsorbents for Hg(II) removal from water

  4. Development of vapor deposited silica sol-gel particles for use as a bioactive materials system.

    Science.gov (United States)

    Snyder, Katherine L; Holmes, Hallie R; VanWagner, Michael J; Hartman, Natalie J; Rajachar, Rupak M

    2013-06-01

    Silica-based sol-gel and bioglass materials are used in a variety of biomedical applications including the surface modification of orthopedic implants and tissue engineering scaffolds. In this work, a simple system for vapor depositing silica sol-gel nano- and micro-particles onto substrates using nebulizer technology has been developed and characterized. Particle morphology, size distribution, and degradation can easily be controlled through key formulation and manufacturing parameters including water:alkoxide molar ratio, pH, deposition time, and substrate character. These particles can be used as a means to rapidly modify substrate surface properties, including surface hydrophobicity (contact angle changes >15°) and roughness (RMS roughness changes of up to 300 nm), creating unique surface topography. Ions (calcium and phosphate) were successfully incorporated into particles, and induced apatitie-like mineral formation upon exposure to simulated body fluid Preosteoblasts (MC3T3) cultured with these particles showed up to twice the adhesivity within 48 h when compared to controls, potentially indicating an increase in cell proliferation, with the effect likely due to both the modified substrate properties as well as the release of silica ions. This novel method has the potential to be used with implants and tissue engineering materials to influence cell behavior including attachment, proliferation, and differentiation via cell-material interactions to promote osteogenesis. Copyright © 2012 Wiley Periodicals, Inc.

  5. Reinforcement of LENRA film by in-situ generated silica produced by sol gel process

    International Nuclear Information System (INIS)

    Mahathir Mohamed; Eda Yuhana Ariffin; Dahlan Mohd; Ibrahim Abdullah

    2008-08-01

    Liquid epoxidised natural rubber acrylate (LENRA) film was reinforced with silica-siloxane structures formed in-situ via sol gel process. Combination of these two components produces organic-inorganic composites. Tetraethylorthosilicate (TEOS) was used as precursor material for silica generation. Sol gel reaction was carried out at different concentrations of TEOS i.e. between 10 and 50 phr. Instrumental analysis was carried out by dynamic mechanical analysis (DMA), thermogravimetry analysis (TGA) and FTIR. It was found that miscibility between organic and inorganic components improved with the presence of silanol groups (Si-OH) and polar solvent i.e. THF, via hydrogen bonding formation between siloxane and LENRA. In this work, the effects of TEOS composition on mechanical properties and interaction that occurs between fillers and matrix have also been studied. It was observed that increasing the concentration of TEOS improved the scratch and stress properties of the film. Morphology study by the scanning electron microscopy (SEM) showed in-situ generated silica particles were homogenous and well dispersed at low concentrations of TEOS. (Author)

  6. Synthesis and characterization of nanocomposite powders of calcium phosphate/silica-gel; Sintese e caracterizacao de pos nanoestruturados de fosfato de calcio/silica-gel

    Energy Technology Data Exchange (ETDEWEB)

    Muller, D.T.; Delima, S.A. [Universidade do Estado de Santa Catarina (UDESC), Joinville, SC (Brazil). Dept. de Engenharia Mecanica; Santos, R.B.M.; Camargo, N.H.A., E-mail: dem2nhac@joinville.udesc.b [Universidade do Estado de Santa Catarina (UDESC), Joinville, SC (Brazil). Programa de Pos Graduacao em Ciencia e Engenharia de Materiais

    2009-07-01

    In the recent years ceramics of calcium phosphate are pointed out as an outstanding material in substitution and regeneration in defects from osseous tissue, in reason of their similar mineralogical characteristics of apatite of bone structure. However, the challenge with phosphate calcium ceramics find out about the mechanical properties and the development of biomaterials similar of the bone structure, what sometimes is not so easy, about fragile materials. The aim of this work focused in synthesis and characterization nanocomposites powders of calcium phosphate/silica-gel with percentages 1, 2, 3 e 5% of nanometric silica. The method synthesis used for the compositions elaboration was dissolution-precipitation. The presented results are related with the optimization to method elaboration of nanostructured powders, the mineralogical characterization with X-ray diffraction, thermal behavior with thermal differential analysis, differential scanning calorimetry here is ADT and dilatometer. The scanning electronic microscopy was used to help of morphological characterization the nanostructured powders and the surfaces from body test recovered from the mechanical test. (author)

  7. Effect of Shear History on Rheology of Time-Dependent Colloidal Silica Gels

    Directory of Open Access Journals (Sweden)

    Paulo H. S. Santos

    2017-11-01

    Full Text Available This paper presents a rheological study describing the effects of shear on the flow curves of colloidal gels prepared with different concentrations of fumed silica (4%, 5%, 6%, and 7% and a hydrophobic solvent (Hydrocarbon fuel, JP-8. Viscosity measurements as a function of time were carried out at different shear rates (10, 50, 100, 500, and 1000 s−1, and based on this data, a new structural kinetics model was used to describe the system. Previous work has based the analysis of time dependent fluids on the viscosity of the intact material, i.e., before it is sheared, which is a condition very difficult to achieve when weak gels are tested. The simple action of loading the gel in the rheometer affects its structure and rheology, and the reproducibility of the measurements is thus seriously compromised. Changes in viscosity and viscoelastic properties of the sheared material are indicative of microstructural changes in the gel that need to be accounted for. Therefore, a more realistic method is presented in this work. In addition, microscopical images (Cryo-SEM were obtained to show how the structure of the gel is affected upon application of shear.

  8. Characterization of silica particles prepared via urease-catalyzed urea hydrolysis and activity of urease in sol–gel silica matrix

    International Nuclear Information System (INIS)

    Kato, Katsuya; Nishida, Masakazu; Ito, Kimiyasu; Tomita, Masahiro

    2012-01-01

    Highlights: ► Silica precipitation occurred via urease-catalytic reactions. ► Higher urease activity for silica synthesis enables mesostructure of silica–urease composites. ► Urease encapsulating in silica matrix retained high activity. - Abstract: Urease templated precipitation of silica synthesized by sol–gel chemistry produces a composite material allowing high urease activity. This study investigates the structural properties of the composite material that allow for the retention of the urease hydrolysis activity. Scanning (SEM) and transmission (TEM) electron microscopy reveal that the composite has a mesoporous structure composed of closely packed spherical structures ∼20–50 nm in diameter. Brunauer–Emmett–Teller (BET) analysis revealed that the surface area and pore volume of the composite prepared under the conditions of 50 mM urea and 25 °C is relatively high (324 m 2 /g and 1.0 cm 3 /g). These values are equivalent to those of usual mesoporous silica materials synthesized from the self-assembly of triblock copolymers as organic templates. In addition, after encapsulating in a sol–gel silica matrix, urease retained high activity (∼90% of the activity compared with native urease). Our results suggest a new method for synthesizing mesoporous silica materials with highly tunable pore sizes and shapes under mild conditions.

  9. Synthesis and nonlinear optical properties of zirconia-protected gold nanoparticles embedded in sol-gel derived silica glass

    Science.gov (United States)

    Le Rouge, A.; El Hamzaoui, H.; Capoen, B.; Bernard, R.; Cristini-Robbe, O.; Martinelli, G.; Cassagne, C.; Boudebs, G.; Bouazaoui, M.; Bigot, L.

    2015-05-01

    A new approach to dope a silica glass with gold nanoparticles (GNPs) is presented. It consisted in embedding zirconia-coated GNPs in a silica sol to form a doped silica gel. Then, the sol-doped nanoporous silica xerogel is densified leading to the formation of a glass monolith. The spectral position and shape of the surface plasmon resonance (SPR) reported around 520 nm remain compatible with small spherical GNPs in a silica matrix. The saturable absorption behavior of this gold/zirconia-doped silica glass has been evidenced by Z-scan technique. A second-order nonlinear absorption coefficient β of about -13.7 cm GW-1 has been obtained at a wavelength near the SPR of the GNPs.

  10. Silica Gel-Mediated Organic Reactions under Organic Solvent-Free Conditions

    Directory of Open Access Journals (Sweden)

    Satoaki Onitsuka

    2012-09-01

    Full Text Available Silica gel was found to be an excellent medium for some useful organic transformations under organic solvent-free conditions, such as (1 the Friedel-Crafts-type nitration of arenes using commercial aqueous 69% nitric acid alone at room temperature, (2 one-pot Wittig-type olefination of aldehydes with activated organic halides in the presence of tributyl- or triphenylphosphine and Hunig’s base, and (3 the Morita-Baylis-Hillman reaction of aldehydes with methyl acrylate. After the reactions, the desired products were easily obtained in good to excellent yields through simple manipulation.

  11. Fabrication of silica glass containing yellow oxynitride phosphor by the sol-gel process

    Energy Technology Data Exchange (ETDEWEB)

    Segawa, Hiroyo; Yoshimizu, Hisato; Hirosaki, Naoto; Inoue, Satoru, E-mail: SEGAWA.Hiroyo@nims.go.jp [National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

    2011-06-15

    We have prepared silica glass by the sol-gel method and studied its ability to disperse the Ca-{alpha}-SiAlON:Eu{sup 2+} phosphor for application in white light emitting diodes (LEDs). The emission color generated by irradiating doped glass with a blue LED at 450 nm depended on the concentration of SiAlON and the glass thickness, resulting in nearly white light. The luminescence efficiency of 1-mm-thick glass depended on the SiAlON concentration, and was highest at 4 wt% SiAlON.

  12. Preparation and characterisation of a sorbent suitable for technetium separation from environmental matrices

    International Nuclear Information System (INIS)

    Bartosova, A.; Rajec, P.; Reich, M.

    2003-01-01

    A sorbent based on Aliquat 336 anchored on hydrophobised silica gel support as an ion exchanger was prepared. Prepared sorbent was suitable for separation of technetium-99 from environmental matrices. The sorbent properties, sorption characteristic and distribution coefficient of 99 mTcO 4 - in various medium was studied. The chemical yield of Tc during separation process was determined using 99m Tc tracer and gamma measurement. Typical sorption recoveries of Tc for this sorbent from 0.1 M HNO 3 were more than 98 %. Typical desorption recoveries using 8 M HNO 3 were in the range 92 - 96 %. The commercial TEVA Spec resin from Eichrom Industries for comparison purpose was used as well. It was found that the prepared sorbent is suitable for separation of technetium from environmental matrices. (authors)

  13. Characteristics of supported nano-TiO{sub 2}/ZSM-5/silica gel (SNTZS): Photocatalytic degradation of phenol

    Energy Technology Data Exchange (ETDEWEB)

    Zainudin, Nor Fauziah; Abdullah, Ahmad Zuhairi [School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300 Nibong Tebal, Penang (Malaysia); Mohamed, Abdul Rahman, E-mail: chrahman@eng.usm.my [School of Chemical Engineering, Engineering Campus, Universiti Sains Malaysia, Seri Ampangan, 14300 Nibong Tebal, Penang (Malaysia)

    2010-02-15

    Photocatalytic degradation of phenol was investigated using the supported nano-TiO{sub 2}/ZSM-5/silica gel (SNTZS) as a photocatalyst in a batch reactor. The prepared photocatalyst was characterized using XRD, TEM, FT-IR and BET surface area analysis. The synthesized photocatalyst composition was developed using nano-TiO{sub 2} as the photoactive component and zeolite (ZSM-5) as the adsorbents, all supported on silica gel using colloidal silica gel binder. The optimum formulation of SNTZS catalyst was observed to be (nano-TiO{sub 2}:ZSM-5:silica gel:colloidal silica gel = 1:0.6:0.6:1) which giving about 90% degradation of 50 mg/L phenol solution in 180 min. The SNTZS exhibited higher photocatalytic activity than that of the commercial Degussa P25 which only gave 67% degradation. Its high photocatalytic activity was due to its large specific surface area (275.7 m{sup 2}/g), small particle size (8.1 nm), high crystalline quality of the synthesized catalyst and low electron-hole pairs recombination rate as ZSM-5 adsorbent was used. The SNTZS photocatalyst synthesized in this study also has been proven to have an excellent adhesion and reusability.

  14. Characteristics of supported nano-TiO2/ZSM-5/silica gel (SNTZS): Photocatalytic degradation of phenol

    International Nuclear Information System (INIS)

    Zainudin, Nor Fauziah; Abdullah, Ahmad Zuhairi; Mohamed, Abdul Rahman

    2010-01-01

    Photocatalytic degradation of phenol was investigated using the supported nano-TiO 2 /ZSM-5/silica gel (SNTZS) as a photocatalyst in a batch reactor. The prepared photocatalyst was characterized using XRD, TEM, FT-IR and BET surface area analysis. The synthesized photocatalyst composition was developed using nano-TiO 2 as the photoactive component and zeolite (ZSM-5) as the adsorbents, all supported on silica gel using colloidal silica gel binder. The optimum formulation of SNTZS catalyst was observed to be (nano-TiO 2 :ZSM-5:silica gel:colloidal silica gel = 1:0.6:0.6:1) which giving about 90% degradation of 50 mg/L phenol solution in 180 min. The SNTZS exhibited higher photocatalytic activity than that of the commercial Degussa P25 which only gave 67% degradation. Its high photocatalytic activity was due to its large specific surface area (275.7 m 2 /g), small particle size (8.1 nm), high crystalline quality of the synthesized catalyst and low electron-hole pairs recombination rate as ZSM-5 adsorbent was used. The SNTZS photocatalyst synthesized in this study also has been proven to have an excellent adhesion and reusability.

  15. Visible-light-induced hydrogen production over Pt-Eosin Y catalysts with high surface area silica gel as matrix

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaojie [State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, The Chinese Academy of Sciences, Lanzhou 730000 (China); Graduate University of the Chinese Academy of Sciences, Beijing 100101 (China); Jin, Zhiliang; Li, Shuben; Lu, Gongxuan [State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics, The Chinese Academy of Sciences, Lanzhou 730000 (China); Li, Yuexiang [Department of Chemistry, Nanchang University, Nanjing Road 245, Nanchang, 330047 (China)

    2007-03-30

    A new system for the production of hydrogen, constructed using silica gel as a matrix, Eosin Y as a photosensitizer, and Pt as a cocatalyst, has been reported. It was found that the rate of photosensitized hydrogen evolution in the presence of silica gel is enhanced about 10-fold relative to the homogeneous phase, i.e. in the absence of silica gel. The pH value of the solution and the concentration of Eosin Y have remarkable effects on the rate of hydrogen evolution. The optimal pH and concentration of Eosin Y are 7 and 3.60 x 10{sup -4} mol dm{sup -3} (E/S = 1/3) to 7.24 x 10{sup -4} mol dm{sup -3} (E/S = 1/1), respectively. Triethanolamine (TEOA) as an electron donor, the rate of hydrogen evolution and the apparent quantum efficiency in the silica gel system under visible-light irradiation ({lambda} {>=} 420 nm) can reach about 43 {mu}mol h{sup -1} and 10.4%, respectively. In addition, the roles of silica gel, Pt and TEOA, respectively; and the probable mechanism of photosensitized hydrogen evolution have been discussed. (author)

  16. Visible-light-induced hydrogen production over Pt-Eosin Y catalysts with high surface area silica gel as matrix

    Science.gov (United States)

    Zhang, Xiaojie; Jin, Zhiliang; Li, Yuexiang; Li, Shuben; Lu, Gongxuan

    A new system for the production of hydrogen, constructed using silica gel as a matrix, Eosin Y as a photosensitizer, and Pt as a cocatalyst, has been reported. It was found that the rate of photosensitized hydrogen evolution in the presence of silica gel is enhanced about 10-fold relative to the homogeneous phase, i.e. in the absence of silica gel. The pH value of the solution and the concentration of Eosin Y have remarkable effects on the rate of hydrogen evolution. The optimal pH and concentration of Eosin Y are 7 and 3.60 × 10 -4 mol dm -3 (E/S = 1/3) to 7.24 × 10 -4 mol dm -3 (E/S = 1/1), respectively. Triethanolamine (TEOA) as an electron donor, the rate of hydrogen evolution and the apparent quantum efficiency in the silica gel system under visible-light irradiation (λ ≥ 420 nm) can reach about 43 μmol h -1 and 10.4%, respectively. In addition, the roles of silica gel, Pt and TEOA, respectively; and the probable mechanism of photosensitized hydrogen evolution have been discussed.

  17. Effectiveness of silica based sol-gel microencapsulation method for odorants and flavors leading to sustainable environment.

    Science.gov (United States)

    Ashraf, Muhammad Aqeel; Khan, Aysha Masood; Ahmad, Mushtaq; Sarfraz, Maliha

    2015-01-01

    Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol-gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol-gel SiO2 is non-toxic and safe, whereas the sol-gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped active agents, thereby broadening the practical utilization of chemically unstable essential oils (EOs). Reviewing progress in the fabrication of diverse odorant and flavored sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits.

  18. Effectiveness of silica based Sol-gel microencapsulation Method for odorants and flavours leading to sustainable Environment

    Directory of Open Access Journals (Sweden)

    Muhammad Aqeel eAshraf

    2015-08-01

    Full Text Available Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol–gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol–gel SiO2 is non-toxic and safe, whereas the sol–gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped actives, thereby broadening the practical utilization of chemically unstable essential oils. Reviewing progress in the fabrication of diverse odorant and flavoured sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits.

  19. Effectiveness of silica based sol-gel microencapsulation method for odorants and flavors leading to sustainable environment

    Science.gov (United States)

    Ashraf, Muhammad Aqeel; Khan, Aysha Masood; Ahmad, Mushtaq; Sarfraz, Maliha

    2015-01-01

    Microencapsulation has become a hot topic in chemical research. Technology mainly used for control release and protection purposes. The sol-gel micro encapsulation approach for fragrance and aroma in porous silica-based materials leads to sustainable odorant and flavored materials with novel and unique beneficial properties. Sol-gel encapsulation of silica based micro particles considered economically cheap as capital investment in manufacturing is very low and environmentally friendly. Amorphous sol-gel SiO2 is non-toxic and safe, whereas the sol-gel entrapment of delicate chemicals in its inner pores results in pronounced chemical and physical stabilization of the entrapped active agents, thereby broadening the practical utilization of chemically unstable essential oils (EOs). Reviewing progress in the fabrication of diverse odorant and flavored sol-gels, shows us how different synthetic strategies are appropriate for practical application with important health and environmental benefits. PMID:26322304

  20. Synthesis of all-silica zeolites from highly concentrated gels containing hexamethonium cations

    KAUST Repository

    Liu, Xiaolong

    2012-07-01

    A pure and highly crystalline all-silica EU-1 zeolite has been obtained from the crystallization of gels containing very low water contents in the presence of hexamethonium cations. Decreasing the water content in the gel down to H 2O/Si < 1 inhibited the formation of ZSM-48, which is usually observed under more diluted standard crystallization conditions. Moreover, addition of NH 4F to the synthesis led to the formation of "half-fluorinated" ITQ-13 in which fluoride anions occupied only the center of D4R cages. In larger cages, the charge of the template was compensated by framework connectivity defects, clearly demonstrating once more the essential role of F - in the formation of D4R units. The formation of such hybrid (F,OH) is particularly interesting from a synthesis point of view, particularly for understanding the respective roles of fluoride and hydroxide anions in the crystallization process. © 2012 Elsevier Inc. All rights reserved.

  1. A pure silica ytterbium-doped sol–gel-based fiber laser

    International Nuclear Information System (INIS)

    Baz, Assaad; El Hamzaoui, Hicham; Fsaifes, Ihsan; Bouwmans, Géraud; Bouazaoui, Mohamed; Bigot, Laurent

    2013-01-01

    In this letter it is demonstrated that the sol–gel route combined with fiber fabrication by the stack and draw method can be used to realize efficient fiber lasers. More precisely, a pure silica ytterbium-doped photonic crystal fiber with a core obtained by the sol–gel polymeric technique is studied, and a laser efficiency of more than 73% is achieved for a laser emission around 1034 nm. The optical and spectroscopic properties of the monolith and fiber are investigated, together with the sensitivity of the fiber to photodarkening. The dimensions of the ytterbium-doped monolith combined with the uniform doping and refractive index that are reported make this technique particularly interesting for the realization of large-mode area fibers. (letter)

  2. Characterization of selenium doped silica glasses synthesized by sol-gel method

    International Nuclear Information System (INIS)

    Kobayashi, R.A.; Toffoli, S.M.

    2012-01-01

    Selenium is a rare element in nature. It is used in the food, pharmaceutical, and glass industries. In commercial glasses, selenium is the element responsible for most of the pink or light red color, but its effect is primarily dependent on the oxidation state of the element in the glassy matrix. Besides, selenium is highly volatile, and as high as 80 wt% may be lost in the furnace during the industrial glass elaboration. The sol– gel method yields synthesized materials of high purity and homogeneity, and uses low processing temperatures. Samples of silica glass were obtained by sol-gel method, incorporating precursors of selenium, with the main objective of reducing selenium losses during its heating. The results of optical absorption, XRD and thermal analysis (TGA, DSC) of the glasses are presented and discussed. (author)

  3. Ionic liquids as dynamic templating agents for sol-gel silica systems: synergistic anion and cation effect on the silica structured growth

    Czech Academy of Sciences Publication Activity Database

    Donato, K. Z.; Donato, Ricardo Keitel; Lavorgna, M.; Ambrosio, L.; Matějka, Libor; Mauler, R. S.; Schrekker, H. S.

    2015-01-01

    Roč. 76, č. 2 (2015), s. 414-427 ISSN 0928-0707 R&D Projects: GA ČR GAP108/12/1459 Institutional support: RVO:61389013 Keywords : silica * imidazolium ionic liquid * sol-gel Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.473, year: 2015

  4. Adsorption Characteristics of Water and Silica Gel System for Desalination Cycle

    KAUST Repository

    Cevallos, Oscar R.

    2012-01-01

    (D-Se) isotherm for the whole pressure range, and for a pressure range below 10 kPa, proper for desalination cycles; isotherms type V of the International Union of Pure and Applied Chemistry (IUPAC) classification were exhibited. It is observed that the D-A based on PSD and the D-Se isotherm models describe the best fitting of the experimental uptake data for desalination cycles within a regression error of 2% and 6% respectively. All isotherm models, except the D-A based on PSD, have failed to describe the obtained experimental uptake data; an empirical isotherm model is proposed by observing the behavior of Tóth and D-A isotherm models. The new empirical model describes the water adsorption onto silica gel type A++ within a regression error of 3%. This will aid to describe the advantages of silica gel type A++ for the design of adsorption desalination processes where reducing capital cost and footprint area are highly important parameters to take into account.

  5. Sinus lift using a nanocrystalline hydroxyapatite silica gel in severely resorbed maxillae: histological preliminary study.

    Science.gov (United States)

    Canullo, Luigi; Dellavia, Claudia

    2009-10-01

    The aim of this preliminary study was to evaluate histologically a nanocrystalline hydroxyapatite silica gel in maxillary sinus floor grafting in severely resorbed maxillae. A total of 16 consecutive patients scheduled for sinus lift were recruited during this study. Patients were randomly divided in two groups, eight patients each. In both groups, preoperative residual bone level ranged between 1 and 3 mm (mean value of 2.03 mm). No membrane was used to occlude the buccal window. Second surgery was carried out after a healing period of 3 months in Group 1 and 6 months in Group 2. Using a trephine bur, one bone specimen was harvested from each augmented sinus and underwent histological and histomorphometric analysis. Histological analysis showed significant new bone formation and remodeling of the grafted material. In the cores obtained at 6 months, regenerated bone, residual NanoBone, and bone marrow occupied respectively 48 +/- 4.63%, 28 +/- 5.33%, and 24 +/- 7.23% of the grafted volume. In the specimens taken 3 months after grafting, mean new bone was 8 +/- 3.34%, mean NanoBone was 45 +/- 5.10%, and mean bone marrow was 47 +/- 6.81% of the bioptical volume. Within the limits of this preliminary prospective study, it was concluded that grafting of maxillary sinus using nanostructured hydroxyapatite silica gel as only bone filler is a reliable procedure also in critical anatomic conditions and after early healing period.

  6. Modeling the supercritical desorption of orange essential oil from a silica-gel bed

    Directory of Open Access Journals (Sweden)

    Silva E.A.

    2000-01-01

    Full Text Available One of the most important byproducts of the orange juice industry is the oil phase. This is a mixture of terpenes, alcohols, and aldehydes, dissolved in approximately 96% limonene. To satisfactorily use oil phase as an ingredient in the food and cosmetics industries separation of the limonene is required. One possibility is to use a fixed bed of silica gel to remove the light or aroma compounds from the limonene. The aroma substances are then extracted from the bed of silica gel using supercritical carbon dioxide. This work deals with the modeling of the desorption step of the process using mass balance equations coupled with the Langmuir equilibrium isotherm. Data taken from the literature for the overall extraction curves were used together with empirical correlations to calculate the concentration profile of solute in the supercritical phase at the bed outlet. The system of equations was solved by the finite volume technique. The overall extraction curves calculated were in good agreement with the experimental ones.

  7. Silica doped with lanthanum sol–gel thin films for corrosion protection

    International Nuclear Information System (INIS)

    Abuín, M.; Serrano, A.; Llopis, J.; García, M.A.; Carmona, N.

    2012-01-01

    We present here anticorrosive silica coatings doped with lanthanum ions for the protection of metallic surfaces as an alternative to chromate (VI)-based conversion coatings. The coatings were synthesized by the sol–gel method starting from silicon alkoxides and two different lanthanum precursors: La (III) acetate hydrate and La (III) isopropoxide. Artificial corrosion tests in acid and alkaline media showed their effectiveness for the corrosion protection of AA2024 aluminum alloy sheets for coating prepared with both precursors. The X-ray absorption Near Edge Structure and X-ray Absorption Fine Structure analysis of the coatings confirmed the key role of lanthanum in the structural properties of the coating determining its anticorrosive properties. - Highlights: ► Silica sol–gel films doped with lanthanum ions were synthesized. ► Films from lanthanum-acetate and La-alkoxide were prepared for comparison purposes. ► La-acetate is an affordable chemical reactive preferred for the industry. ► Films properties were explored by scanning electron microscopy and X-Ray absorption spectroscopy. ► An alternative to anticorrosive pre-treatments for metallic surfaces is suggested.

  8. Silica doped with lanthanum sol-gel thin films for corrosion protection

    Energy Technology Data Exchange (ETDEWEB)

    Abuin, M. [Department of Materials Physics, Complutense University at Madrid, Avda. Complutense sn, 28004 Madrid (Spain); Serrano, A. [Glass and Ceramic Institute, CSIC, C. Kelsen 5, 28049 Madrid (Spain); Llopis, J. [Department of Materials Physics, Complutense University at Madrid, Avda. Complutense sn, 28004 Madrid (Spain); Garcia, M.A. [Glass and Ceramic Institute, CSIC, C. Kelsen 5, 28049 Madrid (Spain); IMDEA Nanoscience, Fco. Tomas y Valiente 7, 28049 Madrid (Spain); Carmona, N., E-mail: n.carmona@fis.ucm.es [Department of Materials Physics, Complutense University at Madrid, Avda. Complutense sn, 28004 Madrid (Spain)

    2012-06-01

    We present here anticorrosive silica coatings doped with lanthanum ions for the protection of metallic surfaces as an alternative to chromate (VI)-based conversion coatings. The coatings were synthesized by the sol-gel method starting from silicon alkoxides and two different lanthanum precursors: La (III) acetate hydrate and La (III) isopropoxide. Artificial corrosion tests in acid and alkaline media showed their effectiveness for the corrosion protection of AA2024 aluminum alloy sheets for coating prepared with both precursors. The X-ray absorption Near Edge Structure and X-ray Absorption Fine Structure analysis of the coatings confirmed the key role of lanthanum in the structural properties of the coating determining its anticorrosive properties. - Highlights: Black-Right-Pointing-Pointer Silica sol-gel films doped with lanthanum ions were synthesized. Black-Right-Pointing-Pointer Films from lanthanum-acetate and La-alkoxide were prepared for comparison purposes. Black-Right-Pointing-Pointer La-acetate is an affordable chemical reactive preferred for the industry. Black-Right-Pointing-Pointer Films properties were explored by scanning electron microscopy and X-Ray absorption spectroscopy. Black-Right-Pointing-Pointer An alternative to anticorrosive pre-treatments for metallic surfaces is suggested.

  9. Vapour-phase method in the synthesis of polymer-ibuprofen sodium-silica gel composites.

    Science.gov (United States)

    Kierys, Agnieszka; Krasucka, Patrycja; Grochowicz, Marta

    2017-11-01

    The study discusses the synthesis of polymer-silica composites comprising water soluble drug (ibuprofen sodium, IBS). The polymers selected for this study were poly(TRIM) and poly(HEMA- co -TRIM) produced in the form of permanently porous beads via the suspension-emulsion polymerization method. The acid and base set ternary composites were prepared by the saturation of the solid dispersions of drug (poly(TRIM)-IBS and/or poly(HEMA- co -TRIM)-IBS) with TEOS, and followed by their exposition to the vapour mixture of water and ammonia, or water and hydrochloric acid, at autogenous pressure. The conducted analyses reveal that the internal structure and total porosity of the resulting composites strongly depend on the catalyst which was used for silica precursor gelation. The parameters characterizing the porosity of both of the acid set composites are much lower than the parameters of the base set composites. Moreover, the basic catalyst supplied in the vapour phase does not affect the ibuprofen sodium molecules, whereas the acid one causes transformation of the ibuprofen sodium into the sodium chloride and a derivative of propanoic acid, which is poorly water soluble. The release profiles of ibuprofen sodium from composites demonstrate that there are differences in the rate and efficiency of drug desorption from them. They are mainly affected by the chemical character of the polymeric carrier but are also associated with the restricted swelling of the composites in the buffer solution after precipitation of silica gel.

  10. Vapour-phase method in the synthesis of polymer-ibuprofen sodium-silica gel composites

    Directory of Open Access Journals (Sweden)

    Agnieszka Kierys

    2017-11-01

    Full Text Available The study discusses the synthesis of polymer-silica composites comprising water soluble drug (ibuprofen sodium, IBS. The polymers selected for this study were poly(TRIM and poly(HEMA-co-TRIM produced in the form of permanently porous beads via the suspension-emulsion polymerization method. The acid and base set ternary composites were prepared by the saturation of the solid dispersions of drug (poly(TRIM-IBS and/or poly(HEMA-co-TRIM-IBS with TEOS, and followed by their exposition to the vapour mixture of water and ammonia, or water and hydrochloric acid, at autogenous pressure. The conducted analyses reveal that the internal structure and total porosity of the resulting composites strongly depend on the catalyst which was used for silica precursor gelation. The parameters characterizing the porosity of both of the acid set composites are much lower than the parameters of the base set composites. Moreover, the basic catalyst supplied in the vapour phase does not affect the ibuprofen sodium molecules, whereas the acid one causes transformation of the ibuprofen sodium into the sodium chloride and a derivative of propanoic acid, which is poorly water soluble. The release profiles of ibuprofen sodium from composites demonstrate that there are differences in the rate and efficiency of drug desorption from them. They are mainly affected by the chemical character of the polymeric carrier but are also associated with the restricted swelling of the composites in the buffer solution after precipitation of silica gel.

  11. TRUEX process solvent cleanup with solid sorbents

    International Nuclear Information System (INIS)

    Tse, Pui-Kwan; Reichley-Yinger, L.; Vandegrift, G.F.

    1989-01-01

    Solid sorbents, alumina, silica gel, and Amberlyst A-26 have been tested for the cleanup of degraded TRUEX-NPH solvent. A sodium carbonate scrub alone does not completely remove acidic degradation products from highly degraded solvent and cannot restore the stripping performance of the solvent. By following the carbonate scrub with either neutral alumina or Amberlyst A-26 anion exchange resin, the performance of the TRUEX-NPH is substantially restored. The degraded TRUEX-NPH was characterized before and after treatment by supercritical fluid chromatography. Its performance was evaluated by americium distribution ratios, phase-separation times, and lauric acid distribution coefficients. 17 refs., 2 figs., 5 tabs

  12. Fluorescent silica hybrid materials containing benzimidazole dyes obtained by sol-gel method and high pressure processing

    International Nuclear Information System (INIS)

    Hoffmann, Helena Sofia; Stefani, Valter; Benvenutti, Edilson Valmir; Costa, Tania Maria Haas; Gallas, Marcia Russman

    2011-01-01

    Research highlights: → Sol-gel technique was used to obtain silica based hybrid materials containing benzimidazole dyes. → The sol-gel catalysts, HF and NaF, produce xerogels with different optical and textural characteristics. → High pressure technique (6.0 GPa) was used to produce fluorescent and transparent silica compacts with the dyes entrapped in closed pores, maintaining their optical properties. → The excited state intramolecular proton transfer (ESIPT) mechanism of benzimidazole dyes was studied by steady-state fluorescence spectroscopy for the monoliths, powders, and compacts. - Abstract: New silica hybrid materials were obtained by incorporation of two benzimidazole dyes in the silica network by sol-gel technique, using tetraethylorthosilicate (TEOS) as inorganic precursor. Several syntheses were performed with two catalysts (HF and NaF) producing powders and monoliths with different characteristics. The dye 2-(2'-hydroxy-5'-aminophenyl)benzimidazole was dispersed and physically adsorbed in the matrix, and the dye 2'(5'-N-(3-triethoxysilyl)propylurea-2'-hydroxyphenyl)benzimidazole was silylated, becoming chemically bonded to the silica network. High pressure technique was used to produce fluorescent and transparent silica compacts with the silylated and incorporated dye, at 6.0 GPa and room temperature. The excited state intramolecular proton transfer (ESIPT) mechanism of benzimidazole dyes was studied by steady-state fluorescence spectroscopy for the monoliths, powders, and compacts. The influence of the syntheses conditions was investigated by textural analysis using nitrogen adsorption isotherms.

  13. Structural and optical studies of nano-structure silica gel doped with different rare earth elements, prepared by two different sol -gel techniques

    International Nuclear Information System (INIS)

    Battisha, I.K.; El Beyally, A.; Seliman, S.I.; El Nahrawi, A.S.

    2005-01-01

    Structural and optical characteristics of pure silica gel (silica-xerogel, SiO 2 ) and doped with different concentrations ranging from 1 up to 6% of some rare earth (REEs) ions such as, praseodymium Pr +3 ,and Europium Eu +3 , Erbium Er +3 and Holmium Ho +3 , ions, in the form of thin film and monolith materials were prepared by sol - gel technique, Using tetra-ethoxysilane as precursor materials, which are of particular interest for sol-gel integrated optics applications. Some structural and optical features of sol-gel derived monolith and thin films are analyzed and compared, namely the structure of nano-particle monolith and thin film silica-gel samples, based on X-ray diffraction (XRD). The types of structural information obtainable are compared in detail. It is show that the XRD spectra of a-cristobalite are obtained for the two type materials and even by doping with the four REEs ions. Optical measurements of monolith and thin films were also studied and compared, the normal transmission and specular reflection were measured. The refractive index were calculated and discussed

  14. Sol-gel synthesis of iron catalysers supported on silica and titanium for selectively oxidising methane to formaldehyde

    OpenAIRE

    Carlos Alberto Guerrero Fajardo; Francisco José Sánchez Castellanos; Anne Cécile Roger; Claire Courson

    2010-01-01

    Iron materials supported on silica were prepared by the sol-gel method for evaluating catalytic activity in selective o-xidation of methane to formaldehyde. Four catalysts were prepared, one corresponding to the silica support (catalyst 1S), another to the titanium support (catalyst 1T) and two more having 0.5% weight iron loads, one for the silica su-pport (catalyst 2FS) and the last one the titanium support (catalyst 2FT). The higher BET areas were 659 and 850 m2/g for catalysts 1S and 2FS,...

  15. Amperometric detector for gas chromatography based on a silica sol-gel solid electrolyte.

    Science.gov (United States)

    Steinecker, William H; Miecznikowski, Krzysztof; Kulesza, Pawel J; Sandlin, Zechariah D; Cox, James A

    2017-11-01

    An electrochemical cell comprising a silica sol-gel solid electrolyte, a working electrode that protrudes into a gas phase, and reference and counter electrodes that contact the solid electrolyte comprises an amperometric detector for gas chromatography. Under potentiostatic conditions, a current related to the concentration of an analyte in the gas phase is produced by its oxidation at the three-phase boundary among the sol-gel, working electrode, and the gas phase. The sol-gel is processed to contain an electrolyte that also serves as a humidistat to maintain a constant water activity even in the presence the gas chromatographic mobile phase. Response was demonstrated toward a diverse set of analytes, namely hydrogen, 1,2-ethandithiol, phenol, p-cresol, and thioanisole. Using flow injection amperometry of hydrogen with He as the carrier gas, 90% of the steady-state current was achieved in < 1s at a flow rate of 20mLmin -1 . A separation of 1,2-ethandithiol, phenol, p-cresol, and thioanisole at a 2.2mLmin -1 flow rate was achieved with respective detection limits (k = 3 criterion) of 4, 1, 3, and 70 ppmv when the working electrode potential was 800mV. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Role of alkyl alcohol on viscosity of silica-based chemical gels for decontamination of highly radioactive nuclear facilities

    International Nuclear Information System (INIS)

    Choi, B. S.; Yoon, S. B.; Jung, C. H.; Lee, K. W.; Moon, J. K.

    2012-01-01

    Silica-based chemical gel for the decontamination of nuclear facilities was prepared by using fumed silica as a viscosifier, a 0.5 M Ce (IV) solution dissolved in concentrated nitric acid as a chemical decontamination agent, and tripropylene glycol butyl ether (TPGBE) as a co-viscosifier. A new effective strategy for the preparation of the chemical gel was investigated by introducing the alkyl alcohols as organic solvents to effectively dissolve the co-viscosifier. The mixture solution of the co-viscosifier and alkyl alcohols was more effective in the control of viscosity than that of the co-viscosifier only in gel. Here, the alkyl alcohols played a key role as an effective dissolution solvent for the co-viscosifier in the preparation of the chemical gel, resulting in a reducing of the amount of the co-viscosifier and gel time compared with that of the chemical gel prepared without the alkyl alcohols. It was considered that the alkyl alcohols contributed to the effective dissolution of the co-viscosifier as well as the homogeneous mixing in the formation of the gel, while the co-viscosifier in an aqueous media of the chemical decontamination agent solution showed a lower solubility. The decontamination efficiency of the chemical gels prepared in this work using a multi-channel analyzer (MCA) showed a high decontamination efficiency of over ca. 94% and ca. 92% for Co-60 and Cs-137 contaminated on surface of the stainless steel 304, respectively. (authors)

  17. Preparation of Bragg mirrors on silica optical fibers and inner walls of silica capillaries by employing the sol-gel method, and titanium and silicon alkoxides

    Czech Academy of Sciences Publication Activity Database

    Bartoň, Ivo; Matějec, Vlastimil; Mrázek, Jan; Podrazký, Ondřej; Matoušek, J.

    2017-01-01

    Roč. 81, č. 3 (2017), s. 867-879 ISSN 0928-0707 R&D Projects: GA ČR GA16-10019S Grant - others:AV ČR(CZ) SAV-16-17 Program:Bilaterální spolupráce Institutional support: RVO:67985882 Keywords : Multilayered coatings * Silica and titania layersSilica and titania layers * Alkoxide sol–gel method Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering OBOR OECD: Electrical and electronic engineering Impact factor: 1.575, year: 2016

  18. Novel ion-imprinted polymer coated on nanoporous silica as a highly selective sorbent for the extraction of ultratrace quantities of gold ions from mine stone samples

    International Nuclear Information System (INIS)

    Ebrahimzadeh, H.; Moazzen, E.; Amini, M.; Sadeghi, O.

    2013-01-01

    We have developed a gold ion-imprinted polymer (GIP) by incorporating a dipyridyl ligand into an ethylene glycol dimethacrylate matrix which then was coated onto porous silica particles. The material was used for the selective extraction of ultratrace quantities of gold ion from mine stones, this followed by its quantitation by FAAS. The effects of concentration and volume of eluent, pH of the solution, flow rates of sample and eluent, and effect of potentially interfering ions, especially palladium and platinum, was investigated. The limit of detection is -1 , the precision (RSD%) is 1.03 %, and recoveries are >99 %. In order to show the high selectivity and efficiency of the new sorbent, the results were compared to those obtained with more simple sorbents possessing the same functional groups. The accuracy of the method was demonstrated by the accurate determination of gold ions in a certified reference material. To the best of our knowledge, there is no report so far on an imprint for gold ions that has such a selectivity over Pd(II) and Pt(II) ions. (author)

  19. NIFSIL - a composite sorbent for caesium - properties and application

    International Nuclear Information System (INIS)

    Rajec, P.; Orechovska, J.

    1998-01-01

    Samples of the potassium-nickel ferrocyanides K 2 NiFe(CN) 6 , KNi 1,5 Fe(CN) 6 and Ni 2 Fe(CN) 6 were prepared and their properties studied with respect to their use as sorbents for caesium. Caesium is fixed on mixed alkaline-nickel ferrocyanide without structural change. The capacity of Cs retention never reached the theoretic value corresponding to a total release of the monovalent ions of the solid. High distribution coefficients (K D in the order of 10 4 cm 3 /g) determined in batch experiments show that these sorbents have a very high affinity for caesium ions, even in the presence of competing K + , Na + and Ca 2+ ions. The sorbents have a good chemical stability in a wide pH-range (2-12). The irradiation of some sorbent samples with high energy gamma-rays ( 60 Co) of a total dose of 1.10 5 Gy caused no remarkable changes in the sorbent properties (K D , sorption capacity and kinetics, mechanical stability). The sorbents were also tested for 85 Sr and 239 Pu and the results carried out under dynamic and batch experiments have shown that sorbents are not suitable for removal of these radionuclides. Potassium nickel hexacyanoferrate incorporated in silica-gel matrix could compete with others sorbents based on insoluble hexacyanoferrates, has the advantage of good radiation stability and suitable granulometry. The sorbent was prepared on a pilot scale with a capacity about 1000 kg per year with the prospect that it could be easily upgraded to an industrial scale

  20. K3[Fe(CN)6].3H2O supported on silica gel: An efficient and selective ...

    Indian Academy of Sciences (India)

    Department of Chemistry, Payame Noor University, 19395-4697 Tehran, I. R. of IRAN e-mail: ... K3[Fe(CN)6].3H2O, Silica gel; oxime; aldehyde; ketone. 1. Introduction .... ysis, hydrogenation, etc., using organic and inorganic reagents. Besides ...

  1. Sol–gel one-pot synthesis in soft conditions of mesoporous silica materials ready for drug delivery system

    NARCIS (Netherlands)

    Tourne-Peteilh, C.; Begu, S.; Lerner, D.A.; Galarneau, A.; Lafont, U.; Devoiselle, J.M.

    2011-01-01

    The present work reveals a new and simple strategy, a one-step sol–gel procedure, to encapsulate a low water-soluble drug in silica mesostructured microparticles and to improve its release in physiological media. The synthesis of these new materials is based on the efficient solubilisation of a

  2. Hydrogen generation systems utilizing sodium silicide and sodium silica gel materials

    Science.gov (United States)

    Wallace, Andrew P.; Melack, John M.; Lefenfeld, Michael

    2015-07-14

    Systems, devices, and methods combine reactant materials and aqueous solutions to generate hydrogen. The reactant materials can sodium silicide or sodium silica gel. The hydrogen generation devices are used in fuels cells and other industrial applications. One system combines cooling, pumping, water storage, and other devices to sense and control reactions between reactant materials and aqueous solutions to generate hydrogen. Multiple inlets of varied placement geometries deliver aqueous solution to the reaction. The reactant materials and aqueous solution are churned to control the state of the reaction. The aqueous solution can be recycled and returned to the reaction. One system operates over a range of temperatures and pressures and includes a hydrogen separator, a heat removal mechanism, and state of reaction control devices. The systems, devices, and methods of generating hydrogen provide thermally stable solids, near-instant reaction with the aqueous solutions, and a non-toxic liquid by-product.

  3. Simulation of adsorber tube diameter's effect on new design silica gel-water adsorption chiller

    Science.gov (United States)

    Nasruddin, Taufan, A.; Manga, A.; Budiman, D.

    2017-03-01

    A new design of silica gel-water adsorption chiller is proposed. The design configuration is composed of two sorption chambers with compact fin tube heat exchangers as adsorber, condenser, and evaporator. Heat and mass recovery were adopted in order to increase the cooling capacity. Numerical modelling and calculation were used to show the performance of the chiller with different adsorber tube diameter. Under typical condition for hot water inlet/cooling water inlet/chilled water outlet temperatures are 90/30/7°C, respectively, the simulation results showed the best average value of COP, SCP, and cooling power are 0.19, 15.88 W/kg and 279.89 W using 3/8 inch tube.

  4. Theoretical study of simultaneous water and VOCs adsorption and desorption in a silica gel rotor

    DEFF Research Database (Denmark)

    Zhang, G.; Zhang, Y.F.; Fang, Lei

    2008-01-01

    One-dimensional partial differential equations were used to model the simultaneous water and VOC (Volatile Organic Compound) adsorption and desorption in a silica gel rotor which was recommended for indoor air cleaning. The interaction among VOCs and moisture in the adsorption and desorption...... process was neglected in the model as the concentrations of VOC pollutants in typical indoor environment were much lower than that of moisture and the adsorbed VOCs occupied only a minor portion of adsorption capacity of the rotor. Consequently VOC transfer was coupled with heat and moisture transfer only...... by the temperatures of the rotor and the air stream. The VOC transfer equations were solved by discretizing them into explicit up-wind finite differential equations. The model was validated with experimental data. The calculated results suggested that the regeneration time designed for dehumidification may...

  5. Silica-gel Catalyzed Facile Synthesis of 3,4-Dihydropyrimidinones

    International Nuclear Information System (INIS)

    Agarwal, Sameer; Aware, Umesh; Patil, Amit; Rohera, Vinita; Jain, Mukul; Patel, Pankaj; Ghate, Manjunath

    2012-01-01

    We have developed a mild and highly effective procedure for the one-pot synthesis of substituted dihydropyrimidinones in high yields using silica gel as a green, highly efficient and recyclable heterogeneous catalyst. Our approach can be applied to the preparation of a wide range of synthetic analogues for structure-activity studies. Investigations in this direction are ongoing. The pyrimidinone ring is a basic substructure of numerous biologically active alkaloids and pharmaceutical products. These cores are regarded as one of the most important groups of drug-like scaffolds. 3,4-dihydropyrimidinones above are known to exhibit variety of pharmacological activity such as calcium channel modulation, mitotic kinesin Eg5 inhibition, antiviral, anti-inflammatory, antibacterial activity, etc

  6. Hydrogen generation systems and methods utilizing sodium silicide and sodium silica gel materials

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, Andrew P.; Melack, John M.; Lefenfeld, Michael

    2017-12-19

    Systems, devices, and methods combine thermally stable reactant materials and aqueous solutions to generate hydrogen and a non-toxic liquid by-product. The reactant materials can sodium silicide or sodium silica gel. The hydrogen generation devices are used in fuels cells and other industrial applications. One system combines cooling, pumping, water storage, and other devices to sense and control reactions between reactant materials and aqueous solutions to generate hydrogen. Springs and other pressurization mechanisms pressurize and deliver an aqueous solution to the reaction. A check valve and other pressure regulation mechanisms regulate the pressure of the aqueous solution delivered to the reactant fuel material in the reactor based upon characteristics of the pressurization mechanisms and can regulate the pressure of the delivered aqueous solution as a steady decay associated with the pressurization force. The pressure regulation mechanism can also prevent hydrogen gas from deflecting the pressure regulation mechanism.

  7. Silica-gel Catalyzed Facile Synthesis of 3,4-Dihydropyrimidinones

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, Sameer; Aware, Umesh; Patil, Amit; Rohera, Vinita; Jain, Mukul; Patel, Pankaj [Zydus Research Centre, Sarkhej-Bavla N.H., Ahmedabad (India); Ghate, Manjunath [Nirma University, Ahmedabad (India)

    2012-02-15

    We have developed a mild and highly effective procedure for the one-pot synthesis of substituted dihydropyrimidinones in high yields using silica gel as a green, highly efficient and recyclable heterogeneous catalyst. Our approach can be applied to the preparation of a wide range of synthetic analogues for structure-activity studies. Investigations in this direction are ongoing. The pyrimidinone ring is a basic substructure of numerous biologically active alkaloids and pharmaceutical products. These cores are regarded as one of the most important groups of drug-like scaffolds. 3,4-dihydropyrimidinones above are known to exhibit variety of pharmacological activity such as calcium channel modulation, mitotic kinesin Eg5 inhibition, antiviral, anti-inflammatory, antibacterial activity, etc.

  8. Comparison of the surface ion density of silica gel evaluated via spectral induced polarization versus acid-base titration

    Science.gov (United States)

    Hao, Na; Moysey, Stephen M. J.; Powell, Brian A.; Ntarlagiannis, Dimitrios

    2016-12-01

    Surface complexation models are widely used with batch adsorption experiments to characterize and predict surface geochemical processes in porous media. In contrast, the spectral induced polarization (SIP) method has recently been used to non-invasively monitor in situ subsurface chemical reactions in porous media, such as ion adsorption processes on mineral surfaces. Here we compare these tools for investigating surface site density changes during pH-dependent sodium adsorption on a silica gel. Continuous SIP measurements were conducted using a lab scale column packed with silica gel. A constant inflow of 0.05 M NaCl solution was introduced to the column while the influent pH was changed from 7.0 to 10.0 over the course of the experiment. The SIP measurements indicate that the pH change caused a 38.49 ± 0.30 μS cm- 1 increase in the imaginary conductivity of the silica gel. This increase is thought to result from deprotonation of silanol groups on the silica gel surface caused by the rise in pH, followed by sorption of Na+ cations. Fitting the SIP data using the mechanistic model of Leroy et al. (Leroyet al., 2008), which is based on the triple layer model of a mineral surface, we estimated an increase in the silica gel surface site density of 26.9 × 1016 sites m- 2. We independently used a potentiometric acid-base titration data for the silica gel to calibrate the triple layer model using the software FITEQL and observed a total increase in the surface site density for sodium sorption of 11.2 × 1016 sites m- 2, which is approximately 2.4 times smaller than the value estimated using the SIP model. By simulating the SIP response based on the calibrated surface complexation model, we found a moderate association between the measured and estimated imaginary conductivity (R2 = 0.65). These results suggest that the surface complexation model used here does not capture all mechanisms contributing to polarization of the silica gel captured by the SIP data.

  9. Silica-gel structural characterization during the initial phases of gelation and drying

    International Nuclear Information System (INIS)

    Ferreira, Max Passos

    1996-01-01

    For centuries, glasses and ceramics have been made via melting or solid state reactions at temperatures above 100 deg C. The sol-gel process offers new approaches to the synthesis of glasses and ceramics, combining control of composition and structure at the molecular level with the ability to shape materials in bulk, powder, fiber and thin-film forms. The growth of sol-gel technology research is due to the many unique features of that class of materials. Major applications include optical elements and integrated optical devices, ceramic filters, membranes, supercondutors, magnetic, catalytic and manostructured materials to antioxidant, anticorrosion coatings and composite and biomedical materials. In this work a variety of techniques like spectroscopy, Raman spectroscopy, ultraviolet-visible spectroscopy, light scattering nuclear magnetic resonance, X ray diffraction and nitrogen adsorption have been employed to investigate the initial phase of the sol-gel transition of gamma ray irradiated tetramethoxysilane (TMOS) solutions and non-irradiated TMOS solution and to get information about the structure of the silica gels obtained under different gelation conditions. Typically the tetramethoxysilane solutions were prepared using a molar ratio of TMOS to demineralized water of 1 to 16. Some experiments were made under catalysed conditions. The mixing was carried out at room temperature. The turbidity and light scattering experiments on the polycondensation of tetramethoxysilane show that exists no drastic difference in the gelling time of a gamma ray irradiated and a non-irradiated TMOS+H 2 O (1+16 M) solution. In the absence of a catalyst, the gelling time for both reactions occurs in about 3.30 h. When HNO 3 (o.03 M) was used, the gelling time observed was 3 days. Raman and ultraviolet-visible spectroscopy show no drastic difference during the initial phase at the sol-gel transition under ambient temperature/pressure and under gamma radiation. The gels heated

  10. Fabrication of silica ceramic membrane via sol-gel dip-coating method at different nitric acid amount

    Science.gov (United States)

    Kahlib, N. A. Z.; Daud, F. D. M.; Mel, M.; Hairin, A. L. N.; Azhar, A. Z. A.; Hassan, N. A.

    2018-01-01

    Fabrication of silica ceramics via the sol-gel method has offered more advantages over other methods in the fabrication of ceramic membrane, such as simple operation, high purity homogeneous, well defined-structure and complex shapes of end products. This work presents the fabrication of silica ceramic membrane via sol-gel dip-coating methods by varying nitric acid amount. The nitric acid plays an important role as catalyst in fabrication reaction which involved hydrolysis and condensation process. The tubular ceramic support, used as the substrate, was dipped into the sol of Tetrethylorthosilicate (TEOS), distilled water and ethanol with the addition of nitric acid. The fabricated silica membrane was then characterized by (Field Emission Scanning Electron Microscope) FESEM and (Fourier transform infrared spectroscopy) FTIR to determine structural and chemical properties at different amount of acids. From the XRD analysis, the fabricated silica ceramic membrane showed the existence of silicate hydrate in the final product. FESEM images indicated that the silica ceramic membrane has been deposited on the tubular ceramic support as a substrate and penetrate into the pore walls. The intensity peak of FTIR decreased with increasing of amount of acids. Hence, the 8 ml of acid has demonstrated the appropriate amount of catalyst in fabricating good physical and chemical characteristic of silica ceramic membrane.

  11. Ultra-small dye-doped silica nanoparticles via modified sol-gel technique

    Science.gov (United States)

    Riccò, R.; Nizzero, S.; Penna, E.; Meneghello, A.; Cretaio, E.; Enrichi, F.

    2018-05-01

    In modern biosensing and imaging, fluorescence-based methods constitute the most diffused approach to achieve optimal detection of analytes, both in solution and on the single-particle level. Despite the huge progresses made in recent decades in the development of plasmonic biosensors and label-free sensing techniques, fluorescent molecules remain the most commonly used contrast agents to date for commercial imaging and detection methods. However, they exhibit low stability, can be difficult to functionalise, and often result in a low signal-to-noise ratio. Thus, embedding fluorescent probes into robust and bio-compatible materials, such as silica nanoparticles, can substantially enhance the detection limit and dramatically increase the sensitivity. In this work, ultra-small fluorescent silica nanoparticles (NPs) for optical biosensing applications were doped with a fluorescent dye, using simple water-based sol-gel approaches based on the classical Stöber procedure. By systematically modulating reaction parameters, controllable size tuning of particle diameters as low as 10 nm was achieved. Particles morphology and optical response were evaluated showing a possible single-molecule behaviour, without employing microemulsion methods to achieve similar results. [Figure not available: see fulltext.

  12. 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.

  13. 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.

  14. SOL-GEL SILICA-BASED Ag–Ca–P COATINGS WITH AGRESSIVE PRETREATMENT OF TITANIUM SUBSTRATE

    Directory of Open Access Journals (Sweden)

    ELENA BORSHCHEVA

    2011-12-01

    Full Text Available The aim of the experiment was the obtaining of thin silica coatings on titanium by sol-gel method, using mechanical (SiC - paper No.180 and chemical (leaching in HF pretreatments of the titanium substrates. The solutions were based on TEOS. For the sol-gel dipping process 4 different solutions were prepared: silica, silica with AgNO3 and silica + AgNO3 with brushite (CaHPO4·2H2O or monetite (CaHPO4 powders. The solutions were aged for 7 and 14 days at laboratory temperature. After sol-gel dip-coating process the samples were dried and fired. The adhesion of fired coatings was measured by tape test according to ASTM procedure and the bioactivity of the coatings was tested using in vitro test. The surfaces of the samples after firing, tape test and in vitro test were observed with the optical and electron microscopes. The firing results showed that silica-silver coatings did not change, brushite sol-gel coatings have cracked and the monetite sol-gel coatings have cracked also, but less than brushite ones. In spite of coating´s crackings, the square’s frames made on the surfaces were without any breakdowns after tape tests and the adhesion of all coatings was very good, classified by the highest grade 5. The results of in vitro tests showed that all coatings interacted with simulated body fluid (SBF. After exposition in SBF the new layer formed on substrates. In case of 7 days aged coatings containing brushite the new layer was uniform and compact. In case of 7 days aged coatings containing monetite the new layer was formed by crystals aggregated tightly together. The monetite and brushite coatings prepared from 14 days aged sol were the same as previous ones, but they were thicker. X-ray analyses after in vitro test confirmed dellaite, titanate and hydroxyapatite phases.

  15. A new approach to the silica gel surface : characterization of different surface regions by 29Si magic angle spinning NMR relaxation parameters and consequences for quantification of silica gels by NMR: characterization of different surface regions by silicon-29 magic angle spinning NMR relaxation parameters and consequences for quantification of silica gels by NMR

    NARCIS (Netherlands)

    Pfleiderer, B.; Albert, K.; Bayer, E.; Ven, van de L.J.M.; Haan, de J.W.; Cramers, C.A.M.G.

    1990-01-01

    Native and some monofunctionally derivatized silica gels have been investigated by 29Si CP MAS NMR spectroscopy with pulse and with cross-polarization (CP) excitation. Contact time variation experiments for some native materials yield results for the siloxane (Q4)g roups which cannot be described

  16. Structure and dynamics of spin-labeled insulin entrapped in a silica matrix by the sol-gel method.

    Science.gov (United States)

    Vanea, E; Gruian, C; Rickert, C; Steinhoff, H-J; Simon, V

    2013-08-12

    The structure and conformational dynamics of insulin entrapped into a silica matrix was monitored during the sol to maturated-gel transition by electron paramagnetic resonance (EPR) spectroscopy. Insulin was successfully spin-labeled with iodoacetamide and the bifunctional nitroxide reagent HO-1944. Room temperature continuous wave (cw) EPR spectra of insulin were recorded to assess the mobility of the attached spin labels. Insulin conformation and its distribution within the silica matrix were studied using double electron-electron resonance (DEER) and low-temperature cw-EPR. A porous oxide matrix seems to form around insulin molecules with pore diameters in the order of a few nanometers. Secondary structure of the encapsulated insulin investigated by Fourier transform infrared spectroscopy proved a high structural integrity of insulin even in the dried silica matrix. The results show that silica encapsulation can be used as a powerful tool to effectively isolate and functionally preserve biomolecules during preparation, storage, and release.

  17. Phospholipid Fatty Acids as Physiological Indicators of Paracoccus denitrificans Encapsulated in Silica Sol-Gel Hydrogels

    Directory of Open Access Journals (Sweden)

    Josef Trögl

    2015-02-01

    Full Text Available The phospholipid fatty acid (PLFA content was determined in samples of Paracoccus denitrificans encapsulated in silica hydrogel films prepared from prepolymerized tetramethoxysilane (TMOS. Immediately after encapsulation the total PLFA concentration was linearly proportional to the optical density (600 nm of the input microbial suspension (R2 = 0.99. After 7 days this relationship remained linear, but with significantly decreased slope, indicating a higher extinction of bacteria in suspensions of input concentration 108 cells/mL and higher. trans-Fatty acids, indicators of cytoplasmatic membrane disturbances, were below the detection limit. The cy/pre ratio (i.e., ratio of cyclopropylated fatty acids (cy17:0 + cy19:0 to their metabolic precursors (16:1ω7 + 18:1ω7, an indicator of the transition of the culture to a stationary growth-phase, decreased depending on co-immobilization of nutrients in the order phosphate buffer > mineral medium > Luria Broth rich medium. The ratio, too, was logarithmically proportional to cell concentration. These results confirm the applicability of total PLFA as an indicator for the determination of living biomass and cy/pre ratio for determination of nutrient limitation of microorganisms encapsulated in sol-gel matrices. This may be of interest for monitoring of sol-gel encapsulated bacteria proposed as optical recognition elements in biosensor construction, as well as other biotechnological applications.

  18. New Functionalized Sol-Gel Hybrid Sorbent Coating for Stir Bar Sorptive Extraction of Selected Non-Steroidal Anti Inflammatory Drugs in Human Urine Samples

    International Nuclear Information System (INIS)

    Mashkurah Abd Rahim; Wan Aini Wan Ibrahim; Zainab Ramli; Mohd Marsin Sanagi

    2015-01-01

    A new sol-gel hybrid material, methyltrimethoxysilane-cyanopropyltriethoxysilane (MTMOS-CNPrTEOS) was successfully synthesized and used as a coating material in stir bar sorptive extraction (SBSE) of selected non-steroidal anti-inflammatory drugs (NSAIDs) in urine samples. The MTMOS-CNPrTEOS hybrid was synthesized by hydrolysis and condensation of MTMOS and CNPrTEOS in the presence of trifluoroacetic acid as catalyst via sol-gel method. Several factors influencing the synthesized sol-gel hybrid MTMOS-CNPrTEOS process such as mole ratio of MTMOS-CNPrTEOS, NaOH concentrations as etching solution, etching time, coating time and water content were investigated and optimized in this study. The optimum synthesis conditions obtained were 1:1 mol ratio of MTMOS-CNPrTEOS, 1 M NaOH as etching solution, 60 min etching time, 2 h coating time and 6 mmol water. The sol-gel hybrid MTMOS-CNPrTEOS synthesized under the optimum conditions was used to determine selected NSAIDs in human urine samples using normal stacking mode capillary electrophoresis with ultraviolet detection. MTMOS-CNPrTEOS SBSE method demonstrated good linearity (60 to 20,000 μg L -1 ) with excellent coefficient of determination (r 2 > 0.9990). The sol-gel hybrid MTMOS-CNPrTEOS SBSE method showed low limit of detection (35 - 41 μg L -1 ) with good precision (RSD < 6 %, n = 3) and excellent extraction recoveries (83.5 - 98.9 %) for the selected NSAIDs. The sol-gel hybrid MTMOS-CNPrTEOS SBSE method demonstrated good potential as an alternative sorbent in SBSE method for NSAIDs. (author)

  19. MECHANISMS CONTROLLING Ca ION RELEASE FROM SOL-GEL DERIVED IN SITU APATITE-SILICA NANOCOMPOSITE POWDER

    Directory of Open Access Journals (Sweden)

    Seyed Mohsen Latifi

    2015-03-01

    Full Text Available Ca ion release from bioactive biomaterials could play an important role in their bioactivity and osteoconductivity properties. In order to improve hydroxyapatite (HA dissolution rate, in situ apatite-silica nanocomposite powders with various silica contents were synthesized via sol-gel method and mechanisms controlling the Ca ion release from them were investigated. Obtained powders were characterized by X-ray diffraction (XRD and transmission electron spectroscopy (TEM techniques, acid dissolution test, and spectroscopy by atomic absorption spectrometer (AAS. Results indicated the possible incorporation of (SiO44- into the HA structure and tendency of amorphous silica to cover the surface of HA particles. However, 20 wt. % silica was the lowest amount that fully covered HA particles. All of the nanocomposite powders showed more Ca ion release compared with pure HA, and HA - 10 wt. % silica had the highest Ca ion release. The crystallinity, the crystallite size, and the content of HA, along with the integrity, thickness, and ion diffusion possibility through the amorphous silica layer on the surface of HA, were factors that varied due to changes in the silica content and were affected the Ca ion release from nanocomposite powders.

  20. Determination of arsenate in water by anion selective membrane electrode using polyurethane–silica gel fibrous anion exchanger composite

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Asif Ali, E-mail: asifkhan42003@yahoo.com; Shaheen, Shakeeba, E-mail: shakeebashaheen@ymail.com

    2014-01-15

    Highlights: • PU–Si gel is new anion exchanger material synthesized and characterized. • This material used as anion exchange membrane is applied for electroanalytical studies. • The method for detection and determination of AsO{sub 4}{sup 3−} in traces amounts discussed. • The results are also verified from arsenic analyzer. -- Abstract: Polyurethane (PU)–silica (Si gel) based fibrous anion exchanger composites were prepared by solid–gel polymerization of polyurethane in the presence of different amounts of silica gel. The formation of PU–Si gel fibrous anion exchanger composite was characterized by Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA-DTA), scanning electron microscopy (SEM) and elemental analysis. The membrane having a composition of 5:3 (PU:Si gel) shows best results for water content, porosity, thickness and swelling. Our studies show that the present ion selective membrane electrode is selective for arsenic, having detection limit (1 × 10{sup −8} M to 1 × 10{sup −1} M), response time (45 s) and working pH range (5–8). The selectivity coefficient values for interfering ions indicate good selectivity for arsenate (AsO{sub 4}{sup 3−}) over interfering anions. The accuracy of the detection limit results was compared by PCA-Arsenomat.

  1. In vitro⿿in vivo performance of bare and drug loaded silica gel synthesized via optimized process parameters

    Science.gov (United States)

    Chakraborty, Suparna; Biswas, Supratim

    2016-01-01

    Silica xerogel as a potential drug carrier system for the in vivo as well as in vitro delivery of andrographolide was tested. The present study aims to optimize the effective experimental parameters; volume of ethanol, volume of water and drying temperature by applying response surface methodology coupled with Box⿿Behnken experimental design. The in vitro drug release in simulated body fluid at 37 οC from the selected formulation was significantly highest (44.83 ± 0.9%) among rest of the formulations. Results indicate that sol⿿gel method is useful for entrapping andrographolide in the silica gel and for releasing the same via diffusion through the porous matrix under the in vitro/in vivo conditions. Silica gel exhibited slow matrix degradation as well as sustained release of andrographolide within the experimental time frame of 168 h. In vivo study was performed with three increasing doses [2 mg (S1), 8 mg (S2), and 16 mg (S3)] of silica. Histological fates of different organs were executed with those doses.

  2. The influence of the matrix structure on the oxidation of aniline in a silica sol-gel composite

    International Nuclear Information System (INIS)

    Widera, J.; Kijak, A.M.; Ca, D.V.; Pacey, G.E.; Taylor, R.T.; Perfect, H.; Cox, J.A.

    2005-01-01

    Mesoporous and microporous silica matrices were formed on indium tin oxide electrodes for liquid-phase voltammetry and as monoliths for solid-state voltammetry of aniline. The pore structure, which was verified by scanning probe microscopy and by surface area measurement, was directed by either control of pH during sol-gel processing or by inclusion of a templating agent. Whether aniline was included as a dopant in the sol-gel or as a component of the contacting liquid, the pore size influenced the coupling of the product of its electrochemical oxidation. With microporous silica, the dominant products were dimers and related short-chain products whereas with mesoporous silica, polymerization was suggested. As a step toward the formation of polyaniline (PANI) that is covalently anchored to the sol-gel, the electrochemistry of aniline was investigated using composites prepared from sols comprising tetraethyl orthosilicate (TEOS), 3-aminophenyl-[3-triethoxylsilyl)-propyl] urea (ormosil), and aniline in various ratios. Combinatorial chemistry identified that the optimum combination of silica precursors in terms of obtaining PANI was a 1:12 mole ratio of ormosil:TEOS

  3. An identification of the soft polyelectrolyte gel-like layer on silica colloids using atomic force and electron microscopy.

    Science.gov (United States)

    Škvarla, Jiří; Škvarla, Juraj

    2017-10-01

    A procedure is introduced for measuring the radius of spherical colloid particles from the curvature of upper parts of their central cross-sectional profiles obtained by atomic force microscopy (AFM). To minimize the possible compression and displacement of the spheres, AFM is operated in a mode rendering a constant ultralow pN force on the tip. The procedure allows us to evaluate the mean radius of nearly monodisperse submicrometer spheres of silica in their natively hydrated state in aqueous electrolyte solutions, irrespective of whether they are coagulated or not. A variation in the volume (swelling degree) of layers delimited by the AFM mean radii of these spheres in KCl solutions and their invariable mean radius in vacuum is obtained that follows a scaling power law derived in polymer physics for swellable polyelectrolyte gels and deduced previously by us from coagulation tests. This supports our former suggestion about the existence of soft polyelectrolyte gel-like layer developed spontaneously around silica surfaces and colloids. We discuss this finding in the context of recent knowledge about the structure of the silica/water interface obtained from direct surface force measurements between macroscopic silica surfaces and from particle size measurements of silica colloids and highlight its importance for colloid chemistry and condensed mattter physics. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. A BIDISPERSE MODEL TO STUDY THE HYDROLYSIS OF MALTOSE USING GLUCOAMYLASE IMMOBILIZED IN SILICA AND WRAPPED IN PECTIN GEL

    Directory of Open Access Journals (Sweden)

    L.R.B. Gonçalves

    1997-12-01

    Full Text Available In this work, a bidisperse model is built to represent the hydrolysis of maltose using immobilized glucoamylase. The experimental set is a mixed-batch reactor, maintained at 30ºC, with pectin gel spherical particles that contain enzyme immobilized in macroporous silica. The possibility of substrate adsorption on the pectin gel is also studied because this phenomenon may result in smaller values of diffusivity. Equilibrium assays are then performed for different substrates (maltose, lactose and glucose at different temperatures and pHs. These assays show that adsorption on the pectin gel is not important for the three dextrins analysed. The bidisperse model presents a good fit with the experimental data, when using previously-estimated kinetic and mass transfer parameters (Gonçalves et al., 1997. This result shows that the methodology used (wrapping the silica in pectin gel is appropriate for experimental studies with silica, since it allows a higher degree of agitation without causing shearing

  5. Gel/Space Ratio Evolution in Ternary Composite System Consisting of Portland Cement, Silica Fume, and Fly Ash.

    Science.gov (United States)

    Wu, Mengxue; Li, Chen; Yao, Wu

    2017-01-11

    In cement-based pastes, the relationship between the complex phase assemblage and mechanical properties is usually described by the "gel/space ratio" descriptor. The gel/space ratio is defined as the volume ratio of the gel to the available space in the composite system, and it has been widely studied in the cement unary system. This work determines the gel/space ratio in the cement-silica fume-fly ash ternary system (C-SF-FA system) by measuring the reaction degrees of the cement, SF, and FA. The effects that the supplementary cementitious material (SCM) replacements exert on the evolution of the gel/space ratio are discussed both theoretically and practically. The relationship between the gel/space ratio and compressive strength is then explored, and the relationship disparities for different mix proportions are analyzed in detail. The results demonstrate that the SCM replacements promote the gel/space ratio evolution only when the SCM reaction degree is higher than a certain value, which is calculated and defined as the critical reaction degree (CRD). The effects of the SCM replacements can be predicted based on the CRD, and the theological predictions agree with the test results quite well. At low gel/space ratios, disparities in the relationship between the gel/space ratio and the compressive strength are caused by porosity, which has also been studied in cement unary systems. The ratio of cement-produced gel to SCM-produced gel ( G C to G S C M ratio) is introduced for use in analyzing high gel/space ratios, in which it plays a major role in creating relationship disparities.

  6. Gel/Space Ratio Evolution in Ternary Composite System Consisting of Portland Cement, Silica Fume, and Fly Ash

    Directory of Open Access Journals (Sweden)

    Mengxue Wu

    2017-01-01

    Full Text Available In cement-based pastes, the relationship between the complex phase assemblage and mechanical properties is usually described by the “gel/space ratio” descriptor. The gel/space ratio is defined as the volume ratio of the gel to the available space in the composite system, and it has been widely studied in the cement unary system. This work determines the gel/space ratio in the cement-silica fume-fly ash ternary system (C-SF-FA system by measuring the reaction degrees of the cement, SF, and FA. The effects that the supplementary cementitious material (SCM replacements exert on the evolution of the gel/space ratio are discussed both theoretically and practically. The relationship between the gel/space ratio and compressive strength is then explored, and the relationship disparities for different mix proportions are analyzed in detail. The results demonstrate that the SCM replacements promote the gel/space ratio evolution only when the SCM reaction degree is higher than a certain value, which is calculated and defined as the critical reaction degree (CRD. The effects of the SCM replacements can be predicted based on the CRD, and the theological predictions agree with the test results quite well. At low gel/space ratios, disparities in the relationship between the gel/space ratio and the compressive strength are caused by porosity, which has also been studied in cement unary systems. The ratio of cement-produced gel to SCM-produced gel ( G C to G S C M ratio is introduced for use in analyzing high gel/space ratios, in which it plays a major role in creating relationship disparities.

  7. Immobilized humic substances and immobilized aggregates of humic substances as sorbent for solid phase extraction.

    Science.gov (United States)

    Erny, Guillaume L; Gonçalves, Bruna M; Esteves, Valdemar I

    2013-09-06

    In this work, humic substances (HS) immobilized, as a thin layer or as aggregates, on silica gel were tested as material for solid phase extraction. Some triazines (simazine, atrazine, therbutylazine, atrazine-desethyl-desisopropyl-2-hydroxy, ametryn and terbutryn), have been selected as test analytes due to their environmental importance and to span a large range of solubility and octanol/water partition coefficient (logP). The sorbent was obtained immobilizing a thin layer of HS via physisorption on a pre-coated silica gel with a cationic polymer (polybrene). While the sorbent could be used as it is, it was demonstrated that additional HS could be immobilized, via weak interactions, to form stable humic aggregates. However, while a higher quantity of HS could be immobilized, no significant differences were observed in the sorption parameters. This sorbent have been tested for solid phase extraction to concentrate triazines from aqueous matrixes. The sorbent demonstrated performances equivalent to commercial alternatives as a concentration factor between 50 and 200, depending on the type of triazines, was obtained. Moreover the low cost and the high flow rate of sample through the column allowed using high quantity of sorbent. The analytical procedure was tested with different matrixes including tap water, river water and estuarine water. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Strong visible-light emission of ZnS nanocrystals embedded in sol-gel silica xerogel

    International Nuclear Information System (INIS)

    Yang Ping; Lue, M.-K.; Song, C.-F.; Zhou, G.-J.; Ai, Z.-P.; Xu Dong; Yuan, D.-R.; Cheng, X.-F.

    2003-01-01

    ZnS nanoparticles embedded in novel porous phosphor silica xerogel have been synthesized by sol-gel processing. Their fluorescence properties have been evaluated and compared with those of the Na + -doped and un-doped silica xerogels. Stable and strong visible-light emission of the doped samples has been observed. The relative fluorescence intensities of the samples doped with ZnS nanoparticles (S 2- ions have been obtained by the water solution of NaS) are the highest among all of the doped samples. Its relative fluorescence intensity is about 7.5 times of that of the un-doped silica xerogel and about 300 times of that of pure ZnS nanoparticles. The emission wavelength of the ZnS-doped and Na + -doped samples is the same as that of the un-doped silica xerogel and ZnS nanoparticles (λ em =440-450 nm). This high efficiency luminescence of the doped silica xerogels has been assigned to the luminescence centers of ZnS nanoparticles and Na + in the porous phosphorescence silica xerogel

  9. Ternary mixed-mode silica sorbent of solid-phase extraction for determination of basic, neutral and acidic drugs in human serum.

    Science.gov (United States)

    Jin, Shupei; Qiao, Yinghua; Xing, Jun

    2018-06-01

    In this study, a ternary mixed-mode silica sorbent (TMSS) with octamethylene, carboxyl, and amino groups was prepared via Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction and a subsequent reduction of azide to primary amine. While used in solid-phase extraction (SPE), the retention behavior of TMSS towards a total of nine kinds of basic, neutral, and acidic drugs was investigated in detail. The results revealed that hydrophobic, ion-exchange interaction, and electrostatic repulsion between TMSS and the analytes were closely related to the retention behavior of TMSS. Besides, the log K ow value of the analyte was also a factor influencing the retention behavior of analytes on TMSS. The nine analytes could be retained by TMSS simultaneously and then, were eluted into two fractions according to the acid-base property of the analytes for further determinations. The acidic and neutral analytes were in one fraction, and the basic ones in the other fraction. When used to treat the human serum spiked with the nine drugs, TMSS offered higher recoveries than BakerBond CBA and comparable recoveries to Oasis WCX. It should be noted TMSS had better purifying capability for human serum than Oasis WCX. Under the optimized SPE conditions, a method of SPE hyphenated to high-performance liquid chromatography-ultraviolet detection (HPLC-UV) for determination of the basic, neutral, and acidic drugs spiked in human serum was established. For the nine drugs, the linear ranges were all between 5.0 and 1000 μg L -1 with correlation coefficients (R 2 ) above 0.9990, and the limits of detection (LODs) were in the range of 0.8-2.3 μg L -1 . The intra-day and inter-day relative standard deviations (RSDs) were less than 5.3 and 8.8%, respectively. Graphical abstract Treating drugs in human serum by SPE with ternary mixed-mode silica sorbent.

  10. A large response range reflectometric urea biosensor made from silica-gel nanoparticles.

    Science.gov (United States)

    Alqasaimeh, Muawia; Heng, Lee Yook; Ahmad, Musa; Raj, A S Santhana; Ling, Tan Ling

    2014-07-22

    A new silica-gel nanospheres (SiO2NPs) composition was formulated, followed by biochemical surface functionalization to examine its potential in urea biosensor development. The SiO2NPs were basically synthesized based on sol-gel chemistry using a modified Stober method. The SiO2NPs surfaces were modified with amine (-NH2) functional groups for urease immobilization in the presence of glutaric acid (GA) cross-linker. The chromoionophore pH-sensitive dye ETH 5294 was physically adsorbed on the functionalized SiO2NPs as pH transducer. The immobilized urease determined urea concentration reflectometrically based on the colour change of the immobilized chromoionophore as a result of the enzymatic hydrolysis of urea. The pH changes on the biosensor due to the catalytic enzyme reaction of immobilized urease were found to correlate with the urea concentrations over a linear response range of 50-500 mM (R2 = 0.96) with a detection limit of 10 mM urea. The biosensor response time was 9 min with reproducibility of less than 10% relative standard deviation (RSD). This optical urea biosensor did not show interferences by Na+, K+, Mg2+ and NH4+ ions. The biosensor performance has been validated using urine samples in comparison with a non-enzymatic method based on the use of p-dimethylaminobenzaldehyde (DMAB) reagent and demonstrated a good correlation between the two different methods (R2 = 0.996 and regression slope of 1.0307). The SiO2NPs-based reflectometric urea biosensor showed improved dynamic linear response range when compared to other nanoparticle-based optical urea biosensors.

  11. A Large Response Range Reflectometric Urea Biosensor Made from Silica-Gel Nanoparticles

    Science.gov (United States)

    Alqasaimeh, Muawia; Heng, Lee Yook; Ahmad, Musa; Raj, A.S. Santhana; Ling, Tan Ling

    2014-01-01

    A new silica-gel nanospheres (SiO2NPs) composition was formulated, followed by biochemical surface functionalization to examine its potential in urea biosensor development. The SiO2NPs were basically synthesized based on sol–gel chemistry using a modified Stober method. The SiO2NPs surfaces were modified with amine (-NH2) functional groups for urease immobilization in the presence of glutaric acid (GA) cross-linker. The chromoionophore pH-sensitive dye ETH 5294 was physically adsorbed on the functionalized SiO2NPs as pH transducer. The immobilized urease determined urea concentration reflectometrically based on the colour change of the immobilized chromoionophore as a result of the enzymatic hydrolysis of urea. The pH changes on the biosensor due to the catalytic enzyme reaction of immobilized urease were found to correlate with the urea concentrations over a linear response range of 50–500 mM (R2 = 0.96) with a detection limit of 10 mM urea. The biosensor response time was 9 min with reproducibility of less than 10% relative standard deviation (RSD). This optical urea biosensor did not show interferences by Na+, K+, Mg2+ and NH4+ ions. The biosensor performance has been validated using urine samples in comparison with a non-enzymatic method based on the use of p-dimethylaminobenzaldehyde (DMAB) reagent and demonstrated a good correlation between the two different methods (R2 = 0.996 and regression slope of 1.0307). The SiO2NPs-based reflectometric urea biosensor showed improved dynamic linear response range when compared to other nanoparticle-based optical urea biosensors. PMID:25054632

  12. Silica-gel modified with zirconium oxide as a novel 99Mo adsorbent 99mTc generators

    International Nuclear Information System (INIS)

    Salehi, H.; Mollarazi, E.; Abbasi, H.

    2010-01-01

    A new 99 Mo adsorbent has been prepared with modified silica gel with zirconium oxide (SiO 2 /ZrO 2 :Na 2 MoO 4 ) and used in technetium-99m generator. The adsorption behaviors of 99 Mo in the form of molybdate and 99m Tc in the form of pertechnetate on the new adsorbent was investigated showed that the adsorption capacity of molybdate on this generator was considerably higher than the usual generator with alumina column. Coating zirconium oxide on the surface of silica gel resulted in higher 99 Mo adsorption of this compound. 99m Tc is eluted with 0.9% NaCl, and the radionuclidic, radiochemical and chemical purities of the eluate were checked. This generator has a great potential as compared to the traditional alumina generators.

  13. Immobilization of Chlorosulfonyl-Calix[4]arene onto the surface of silica gel through the directly estrification

    Energy Technology Data Exchange (ETDEWEB)

    Taghvaei-Ganjali, Saeed, E-mail: S-taghvaei@IAU-tnb.ac.ir [Chemistry Department, Islamic Azad University, North Tehran Branch, Postal Code: 1913674711, Tehran (Iran, Islamic Republic of); Zadmard, Reza [Chemistry and Chemical Engineering Research Center of Iran, Postal Code: 1496813151, Tehran (Iran, Islamic Republic of); Saber-Tehrani, Mandana [Chemistry Department, Islamic Azad University, North Tehran Branch, Postal Code: 1913674711, Tehran (Iran, Islamic Republic of)

    2012-06-01

    For the first time Chlorosulfonyl-Calix[4]arene has been chemically bonded to silica gel through the directly estrification without silane coupling agent to prepare Chlorosulfonyl-Calix[4]arene-bonded silica gel. Sample characterization was performed by various techniques such as elemental analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), powder X-ray diffraction (XRD), N{sub 2} adsorption-desorption, thermal gravimetric analysis (TGA), {sup 29}Si CP/MAS spectroscopy and acid-base titration. All data approve the successful incorporation of organic group via covalent bond. From the comparison between sulfur content determined by elemental analysis and the number of H{sup +} determined by acid-base titration, it was shown that two ester units took place onto the new synthesized sample and two acidic sites exist on the surface.

  14. Immobilization of Chlorosulfonyl-Calix[4]arene onto the surface of silica gel through the directly estrification

    Science.gov (United States)

    Taghvaei-Ganjali, Saeed; Zadmard, Reza; Saber-Tehrani, Mandana

    2012-06-01

    For the first time Chlorosulfonyl-Calix[4]arene has been chemically bonded to silica gel through the directly estrification without silane coupling agent to prepare Chlorosulfonyl-Calix[4]arene-bonded silica gel. Sample characterization was performed by various techniques such as elemental analysis, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), powder X-ray diffraction (XRD), N2 adsorption-desorption, thermal gravimetric analysis (TGA), 29Si CP/MAS spectroscopy and acid-base titration. All data approve the successful incorporation of organic group via covalent bond. From the comparison between sulfur content determined by elemental analysis and the number of H+ determined by acid-base titration, it was shown that two ester units took place onto the new synthesized sample and two acidic sites exist on the surface.

  15. Sugarcane bagasse lignin, and silica gel and magneto-silica as drug vehicles for development of innocuous methotrexate drug against rheumatoid arthritis disease in albino rats

    Energy Technology Data Exchange (ETDEWEB)

    Wahba, Sanaa M.R. [Zoology department, Women College, Ain-Shams University,11566 Cairo (Egypt); Darwish, Atef S., E-mail: atef_mouharam@sci.asu.edu.eg [Chemistry department, Faculty of Science, Ain Shams University, Cairo (Egypt); Shehata, Iman H. [Microbiology and Immunology Department, Faculty of Medicine, Ain-Shams University, Cairo (Egypt); Abd Elhalem, Sahar S. [Zoology department, Women College, Ain-Shams University,11566 Cairo (Egypt)

    2015-03-01

    The present study clarifies co-therapy action of deliveries from their textural changes point of view. Methotrexate (MTX) was immobilized onto biodegradable lignin, silica gel and iron/silica nanocomposite. Loaded-MTX was i.p. injected into albino rats at doses of 0.25 and 0.5 mg/kg/week for 2.5 months, after which spleen, liver, testes and knee joint tissues were collected for tests. IFN-γ and IL-17A mRNA gene expressions in spleen in all biological samples were determined by RT-PCR. Physicochemical features of drug carriers were monitored by XRD, BET-PSD, SEM and TEM. Drug inflammatory-site targeting was found to be closely related to the physico-features of deliverers. The interlayered lignin of micro- and meso-pore channels directed MTX toward concealed infected cells in liver and testes tissues, while meso-structured silica flacks satisfied by gathering MTX around knee joints. The magneto-silica nanocomposite targeted MTX toward spleen tissue, which is considered as a lively factory for the production of electron rich compounds. - Highlights: • Opening the door to synthesize smart targeted drug deliveries against RA disease • Therapy action of MTX-laden lignin and Fe{sub 3}O{sub 4}/SiO{sub 2} composite toward RA disease • Procure selective targeted drug deliveries of near 100% curing against RA disease • Revolutionary clinical therapies for RA disease by inventive MTX-delivery models.

  16. Sugarcane bagasse lignin, and silica gel and magneto-silica as drug vehicles for development of innocuous methotrexate drug against rheumatoid arthritis disease in albino rats.

    Science.gov (United States)

    Wahba, Sanaa M R; Darwish, Atef S; Shehata, Iman H; Abd Elhalem, Sahar S

    2015-03-01

    The present study clarifies co-therapy action of deliveries from their textural changes point of view. Methotrexate (MTX) was immobilized onto biodegradable lignin, silica gel and iron/silica nanocomposite. Loaded-MTX was i.p. injected into albino rats at doses of 0.25 and 0.5mg/kg/week for 2.5months, after which spleen, liver, testes and knee joint tissues were collected for tests. IFN-γ and IL-17A mRNA gene expressions in spleen in all biological samples were determined by RT-PCR. Physicochemical features of drug carriers were monitored by XRD, BET-PSD, SEM and TEM. Drug inflammatory-site targeting was found to be closely related to the physico-features of deliverers. The interlayered lignin of micro- and meso-pore channels directed MTX toward concealed infected cells in liver and testes tissues, while meso-structured silica flacks satisfied by gathering MTX around knee joints. The magneto-silica nanocomposite targeted MTX toward spleen tissue, which is considered as a lively factory for the production of electron rich compounds. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Sugarcane bagasse lignin, and silica gel and magneto-silica as drug vehicles for development of innocuous methotrexate drug against rheumatoid arthritis disease in albino rats

    International Nuclear Information System (INIS)

    Wahba, Sanaa M.R.; Darwish, Atef S.; Shehata, Iman H.; Abd Elhalem, Sahar S.

    2015-01-01

    The present study clarifies co-therapy action of deliveries from their textural changes point of view. Methotrexate (MTX) was immobilized onto biodegradable lignin, silica gel and iron/silica nanocomposite. Loaded-MTX was i.p. injected into albino rats at doses of 0.25 and 0.5 mg/kg/week for 2.5 months, after which spleen, liver, testes and knee joint tissues were collected for tests. IFN-γ and IL-17A mRNA gene expressions in spleen in all biological samples were determined by RT-PCR. Physicochemical features of drug carriers were monitored by XRD, BET-PSD, SEM and TEM. Drug inflammatory-site targeting was found to be closely related to the physico-features of deliverers. The interlayered lignin of micro- and meso-pore channels directed MTX toward concealed infected cells in liver and testes tissues, while meso-structured silica flacks satisfied by gathering MTX around knee joints. The magneto-silica nanocomposite targeted MTX toward spleen tissue, which is considered as a lively factory for the production of electron rich compounds. - Highlights: • Opening the door to synthesize smart targeted drug deliveries against RA disease • Therapy action of MTX-laden lignin and Fe 3 O 4 /SiO 2 composite toward RA disease • Procure selective targeted drug deliveries of near 100% curing against RA disease • Revolutionary clinical therapies for RA disease by inventive MTX-delivery models

  18. Replication of butterfly wing and natural lotus leaf structures by nanoimprint on silica sol-gel films

    International Nuclear Information System (INIS)

    Saison, Tamar; Peroz, Christophe; Chauveau, Vanessa; Sondergard, Elin; Arribart, Herve; Berthier, Serge

    2008-01-01

    An original and low cost method for the fabrication of patterned surfaces bioinspired from butterfly wings and lotus leaves is presented. Silica-based sol-gel films are thermally imprinted from elastomeric molds to produce stable structures with superhydrophobicity values as high as 160 deg. water contact angle. The biomimetic surfaces are demonstrated to be tuned from superhydrophobic to superhydrophilic by annealing between 200 deg. C and 500 deg. C

  19. Replication of butterfly wing and natural lotus leaf structures by nanoimprint on silica sol-gel films

    Energy Technology Data Exchange (ETDEWEB)

    Saison, Tamar; Peroz, Christophe; Chauveau, Vanessa; Sondergard, Elin; Arribart, Herve [Unite mixte CNRS/Saint Gobain Saint Gobain Recherche, BP135, 93303 Aubervilliers (France); Berthier, Serge [Institut des Nanosciences de Paris, UMR 7588, CNRS, Universite Pierre et Marie Curie-Paris 6, 140 rue Lourmel, 75015 Paris (France)], E-mail: cperoz@lbl.gov

    2008-12-01

    An original and low cost method for the fabrication of patterned surfaces bioinspired from butterfly wings and lotus leaves is presented. Silica-based sol-gel films are thermally imprinted from elastomeric molds to produce stable structures with superhydrophobicity values as high as 160 deg. water contact angle. The biomimetic surfaces are demonstrated to be tuned from superhydrophobic to superhydrophilic by annealing between 200 deg. C and 500 deg. C.

  20. Influence of structure of carrier (silica gel) on texture and catalytic properties of vanadium catalysts for sulfur dioxide oxidation

    International Nuclear Information System (INIS)

    Simonova, L.G.; Fenelonov, V.B.; Dzis'ko, V.A.; Noskova, S.P.; Kryukova, G.N.; Litvak, G.S.

    1982-01-01

    The influence of initial porous structure of a carrier-silica gel on texture and catalytic properties of vanadium catalysts is considered. It is shown that low thermal stability of the carrier results not only in considerable decrease of the catalyst surface during heat treatment but also in blocking part of active component in locked pores which accounts for the activity decrease in kinetic region and formation of active component forms that can not be extracted by acid

  1. Stability of erbium and silver implanted in silica-titania sol-gel films

    International Nuclear Information System (INIS)

    Ramos, A.R.; Marques, C.; Alves, E.; Marques, A.C.; Almeida, R.M.

    2005-01-01

    We implanted silica-titania sol-gel films with 3 x 10 15 at./cm 2 , 180 keV Er + and 6 x 10 16 at./cm 2 , 140 keV Ag + ions. The energies were chosen so that the profiles of Ag and Er overlap. RBS and ERDA were used to study the behaviour of Ag, Er and H during the heat treatments used to density the films. Implantation causes H depletion at the film surface and an increase in H concentration just beneath the implanted Ag and Er profiles. The total H content decreases by 27% to 75% during implantation. During annealing the H content decreases, with an almost complete H loss after annealing for 35 min at 800 deg. C. The Ag profile remains stable up to 600 deg. C. Above 700 deg. C Ag becomes increasingly mobile. Annealing at 800 deg. C for 35 min results in a nearly constant Ag distribution in the film. The Er profile remains unchanged with heat treatment up to the maximum temperature used (800 deg. C)

  2. Single bead near-infrared random laser based on silica-gel infiltrated with Rhodamine 640

    Science.gov (United States)

    Moura, André L.; Barbosa-Silva, Renato; Dominguez, Christian T.; Pecoraro, Édison; Gomes, Anderson S. L.; de Araújo, Cid B.

    2018-04-01

    Photoluminescence properties of single bead silica-gel (SG) embedded with a laser-dye were studied aiming at the operation of near-infrared (NIR) Random Lasers (RLs). The operation of RLs in the NIR spectral region is especially important for biological applications since the optical radiation has deep tissue penetration with negligible damage. Since laser-dyes operating in the NIR have poor stability and are poor emitters, ethanol solutions of Rhodamine 640 (Rh640) infiltrated in SG beads were used. The Rh640 concentrations in ethanol varied from 10-5 to 10-2 M and the excitation at 532 nm was made by using a 7 ns pulsed laser. The proof-of-principle RL scheme herein presented was adopted in order to protect the dye-molecules from the environment and to favor formation of aggregates. The RL emission from ≈650 nm to 720 nm, beyond the typical Rh640 monomer and dimer wavelengths emissions range, was attributed to the trade-off between reabsorption and reemission processes along the light pathways inside the SG bead and the contribution of Rh640 aggregates.

  3. Experimental study on improved two-bed silica gel-water adsorption chiller

    Energy Technology Data Exchange (ETDEWEB)

    Xia Zaizhong [Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai 200030 (China)], E-mail: xzz@sjtu.edu.cn; Wang Dechang; Zhang Jincui [College of Electromechanical Engineering, Qingdao University, Qingdao 266071 (China)

    2008-06-15

    A novel silica gel-water adsorption chiller with two chambers has been built in Shanghai Jiao Tong University (SJTU). This chiller combines two single bed systems (basic system) without any vacuum valves. One adsorber, one condenser and one evaporator are housed in the same chamber to constitute one adsorption/desorption unit. In this work, the chiller is developed and improved. The improved chiller is composed of three vacuum chambers: two adsorption/desorption vacuum chambers (the same structure as the former chiller) and one heat pipe working vacuum chamber. The evaporators of these two adsorption/desorption units are combined by a heat pipe. So, no valves are installed in the chilled water sub system and one vacuum valve connects the two adsorption/desorption chambers together to improve its performance. The performance of the chiller is tested. As the results, the refrigerating capacity and the COP of the chiller are, respectively, 8.69 kW and 0.388 for the heat source temperature of 82.5 deg. C, the cooling water temperature of 30.4 deg. C and the chilled water outlet temperature of 11.9 deg. C. For a chilled water outlet temperature of 16.5 deg. C, the COP reaches 0.432, while the refrigerating capacity is near 11 kW. There is an improvement of at least 12% for the COP compared with the former chillers.

  4. Experimental study on improved two-bed silica gel-water adsorption chiller

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Zaizhong [Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai 200030 (China); Wang, Dechang; Zhang, Jincui [College of Electromechanical Engineering, Qingdao University, Qingdao 266071 (China)

    2008-06-15

    A novel silica gel-water adsorption chiller with two chambers has been built in Shanghai Jiao Tong University (SJTU). This chiller combines two single bed systems (basic system) without any vacuum valves. One adsorber, one condenser and one evaporator are housed in the same chamber to constitute one adsorption/desorption unit. In this work, the chiller is developed and improved. The improved chiller is composed of three vacuum chambers: two adsorption/desorption vacuum chambers (the same structure as the former chiller) and one heat pipe working vacuum chamber. The evaporators of these two adsorption/desorption units are combined by a heat pipe. So, no valves are installed in the chilled water sub system and one vacuum valve connects the two adsorption/desorption chambers together to improve its performance. The performance of the chiller is tested. As the results, the refrigerating capacity and the COP of the chiller are, respectively, 8.69 kW and 0.388 for the heat source temperature of 82.5 C, the cooling water temperature of 30.4 C and the chilled water outlet temperature of 11.9 C. For a chilled water outlet temperature of 16.5 C, the COP reaches 0.432, while the refrigerating capacity is near 11 kW. There is an improvement of at least 12% for the COP compared with the former chillers. (author)

  5. Spray drying of silica microparticles for sustained release application with a new sol-gel precursor.

    Science.gov (United States)

    Wang, Bifeng; Friess, Wolfgang

    2017-10-30

    A new precursor, tetrakis(2-methoxyethyl) orthosilicate (TMEOS) was used to fabricate microparticles for sustained release application, specifically for biopharmaceuticals, by spray drying. The advantages of TMEOS over the currently applied precursors are its water solubility and hydrolysis at moderate pH without the need of organic solvents or catalyzers. Thus a detrimental effect on biomolecular drug is avoided. By generating spray-dried silica particles encapsulating the high molecular weight model compound FITC-dextran 150 via the nano spray dryer Büchi-90, we demonstrated how formulation parameters affect and enable control of drug release properties. The implemented strategies to regulate release included incorporating different quantities of dextrans with varying molecular weight as well as adjusting the pH of the precursor solution to modify the internal microstructures. The addition of dextran significantly altered the released amount, while the release became faster with increasing dextran molecular weight. A sustained release over 35days could be achieved with addition of 60 kD dextran. The rate of FITC-Dextran 150 release from the dextran 60 containing particles decreased with higher precursor solution pH. In conclusion, the new precursor TMEOS presents a promising alternative sol-gel technology based carrier material for sustained release application of high molecular weight biopharmaceutical drugs. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Surface Behavior of Rhodamin and Tartrazine on Silica-Cellulose Sol-Gel Surfaces by Thin Layer Elution

    Directory of Open Access Journals (Sweden)

    Surjani Wonorahardjo

    2016-05-01

    Full Text Available Physical and chemical interactions are the principles for different types of separation systems as the equillibrium dynamics on surface plays a key-role. Surface modification is a way for selective separation at interfaces. Moreover, synthesis of gel silica by a sol-gel method is preferred due to the homogeneity and surface feature easily controlled. Cellulose can be added in situ to modified the silica features during the process. Further application for to study interaction of rhodamin and tartrazine in its surface and their solubilities in mobile phase explains the possibility for their separation. This paper devoted to evaluate the surface behavior in term of adsorption and desorption of tartrazine and rhodamin on silica-cellulose thin layer in different mobile phase. Some carrier liquids applied such as methanol, acetone, n-hexane and chloroform. The result proves tartrazine and rhodamin is separated and have different behavior in different mobile phase. The retardation factors (Rf of the mixtures suggest complexity behavior on silica-cellulose surface.

  7. Effect of silver ions on the energy transfer from host defects to Tb ions in sol–gel silica glass

    Energy Technology Data Exchange (ETDEWEB)

    Abbass, Abd Ellateef [Department of Physics, University of the Free State, Bloemfontein (South Africa); Department of Physics, Sudan University of Science and Technology (Sudan); Swart, H.C. [Department of Physics, University of the Free State, Bloemfontein (South Africa); Kroon, R.E., E-mail: KroonRE@ufs.ac.za [Department of Physics, University of the Free State, Bloemfontein (South Africa)

    2015-04-15

    Plasmonic metal structures have been suggested to enhance the luminescence from rare-earth (RE) ions, but this enhancement is not yet well understood or applied to phosphor materials. Although some reports using Ag nanoparticles (NPs) in glass have attributed enhancement of RE emission to the strong electric fields associated with Ag NPs, it has also been proposed that the enhancement is instead due to energy transfer from Ag ions to RE ions. Our work using sol–gel silica shows a third possibility, namely that enhancement of the RE (e.g. Tb) emission is due to energy transfer from defects of the host material to the Tb ions, where the addition of Ag influences the silica host defects. The oxidation state of Ag as a function of annealing temperature was investigated by x-ray diffraction, transmission electron microscopy, UV–vis measurements and x-ray photoelectron spectroscopy, while optical properties were investigated using a Cary Eclipse fluorescence spectrophotometer or by exciting samples with a 325 nm He–Cd laser. The results showed that Ag ions have a significant effect on the silica host defects, which resulted in enhancement of the green Tb emission at 544 nm for non-resonant excitation using a wavelength of 325 nm. - Highlights: • Conversion of Ag ions to metallic nanoparticles after annealing of sol–gel silica. • Addition of Ag resulted in enhanced green luminescence from Tb ions in silica. • Enhancement is attributed to the effect of added Ag on the host defects of silica.

  8. Simple and Efficient Synthesis of Iron Oxide-Coated Silica Gel Adsorbents for Arsenic Removal: Adsorption Isotherms and Kinetic Study

    Energy Technology Data Exchange (ETDEWEB)

    Arifin, Eric; Lee, Jiukyu [Interdisciplinary Program in Nanoscience and Technology, Virginia (United States); Cha, Jinmyung [Seoul National Univ., Seoul (Korea, Republic of)

    2013-08-15

    Iron oxide (ferrihydrite, hematite, and magnetite) coated silica gels were prepared using a low-cost, easily-scalable and straightforward method as the adsorbent material for arsenic removal application. Adsorption of the anionic form of arsenic oxyacids, arsenite (AsO{sup 2-}) and arsenate (AsO{sub 4}{sup -3}), onto hematite coated silica gel was fitted against non-linear 3-parameter-model Sips isotherm and 2-parameter-model Langmuir and Freundlich isotherm. Adsorption kinetics of arsenic could be well described by pseudo-second-order kinetic model and value of adsorption energy derived from non-linear Dubinin-Radushkevich isotherm suggests chemical adsorption. Although arsenic adsorption process was not affected by the presence of sulfate, chloride, and nitrate anions, as expected, bicarbonate and silicate gave moderate negative effects while the presence of phosphate anions significantly inhibited adsorption process of both arsenite and arsenate. When the actual efficiency to remove arsenic was tested against 1 L of artificial arsenic-contaminated groundwater (0.6 mg/L) in the presence competing anions, the reasonable amount (20 g) of hematite coated silica gel could reduce arsenic concentration to below the WHO permissible safety limit of drinking water of 10 μg/L without adjusting pH and temperature, which would be highly advantageous for practical field application.

  9. In situ immobilization on the silica gel surface and adsorption capacity of polymer-based azobenzene on toxic metal ions

    Science.gov (United States)

    Savchenko, Irina; Yanovska, Elina; Sternik, Dariusz; Kychkyruk, Olga; Ol'khovik, Lidiya; Polonska, Yana

    2018-03-01

    In situ immobilization of poly[(4-methacryloyloxy-(4'-carboxy)azobenzene] on silica gel surface has been performed by radical polymerization of monomer. The fact of polymer immobilization is confirmed by IR spectroscopy. TG and DSC-MS analysis showed that the mass of the immobilized polymer was 10.61%. The SEM-microphotograph-synthesized composite analysis showed that the immobilized polymer on the silica gel surface is placed in the form of fibers. It has been found that the synthesized composite exhibits the sorption ability in terms of microquantities of Cu(II), Cd(II), Pb(II), Mn(II) and Fe(III) ions in a neutral aqueous medium. The quantitative sorption of microquantities of Pb(II) and Fe(III) ions has been recorded. It has been found that immobilization of the silica gel surface leads to an increase in its sorption capacitance for Fe(III), Cu(II) and Pb(II) ions by half.

  10. Integrating nanohybrid membranes of reduced graphene oxide: chitosan: silica sol gel with fiber optic SPR for caffeine detection

    Science.gov (United States)

    Kant, Ravi; Tabassum, Rana; Gupta, Banshi D.

    2017-05-01

    Caffeine is the most popular psychoactive drug consumed in the world for improving alertness and enhancing wakefulness. However, caffeine consumption beyond limits can result in lot of physiological complications in human beings. In this work, we report a novel detection scheme for caffeine integrating nanohybrid membranes of reduced graphene oxide (rGO) in chitosan modified silica sol gel (rGO: chitosan: silica sol gel) with fiber optic surface plasmon resonance. The chemically synthesized nanohybrid membrane forming the sensing route has been dip coated over silver coated unclad central portion of an optical fiber. The sensor works on the mechanism of modification of dielectric function of sensing layer on exposure to analyte solution which is manifested in terms of red shift in resonance wavelength. The concentration of rGO in polymer network of chitosan and silica sol gel and dipping time of the silver coated probe in the solution of nanohybrid membrane have been optimized to extricate the supreme performance of the sensor. The optimized sensing probe possesses a reasonably good sensitivity and follows an exponentially declining trend within the entire investigating range of caffeine concentration. The sensor boasts of an unparalleled limit of detection value of 1.994 nM and works well in concentration range of 0-500 nM with a response time of 16 s. The impeccable sensor methodology adopted in this work combining fiber optic SPR with nanotechnology furnishes a novel perspective for caffeine determination in commercial foodstuffs and biological fluids.

  11. Solid-phase microextraction Ni-Ti fibers coated with functionalised silica particles immobilized in a sol-gel matrix.

    Science.gov (United States)

    Azenha, Manuel; Ornelas, Mariana; Fernando Silva, A

    2009-03-20

    One of the possible approaches for the development of novel solid-phase microextraction (SPME) fibers is the physical deposition of porous materials onto a support using high-temperature epoxy glue. However, a major drawback arises from decomposition of epoxy glue at temperatures below 300 degrees C and instability in some organic solvents. This limitation motivated us to explore the possibility of replacing the epoxy glue with a sol-gel film, thermally more stable and resistant to organic solvents. We found that functionalised silica particles could be successfully attached to a robust Ni-Ti wire by using a UV-curable sol-gel film. The particles were found to be more important than the sol-gel layer during the microextraction process, as shown by competitive extraction trials and by the different extraction profiles observed with differently functionalised particles. If a quality control microscopic-check aiming at the rejection of fibers exhibiting unacceptably low particle load was conducted, acceptable (6-14%) reproducibility of preparation of C(18)-silica fibers was observed, and a strong indication of the durability of the fibers was also obtained. A cyclohexyldiol-silica fiber was used, as a simple example of applicability, for the successful determination of benzaldehyde, acetophenone and dimethylphenol at trace level in spiked tap water. Recoveries: 95-109%; limits of detection: 2-7 microg/L; no competition effects within the studied range (

  12. Transition metal-free oxidation of benzylic alcohols to carbonyl compounds by hydrogen peroxide in the presence of acidic silica gel

    Directory of Open Access Journals (Sweden)

    Hossein Ghafuri

    2015-01-01

    Full Text Available Oxidation of alcohols to carbonyl compounds has become an important issue in the process industry as well as many other applications. In this method, various benzylic alcohols were successfully converted to corresponding aldehydes and ketones under transition metal-free condition using hydrogen peroxide in the presence of some amount of catalytic acidic silica gel. Silica gel is inexpensive and available. One of the most important features of this method is its short reaction time.

  13. Low-cost humic acid-bonded silica as an effective solid-phase extraction sorbent for convenient determination of aflatoxins in edible oils

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Neng-Zhi [Guangxi Zhuang Autonomous Region Center for Disease Prevention and Control, Nanning, Guangxi 530028 (China); Liu, Ping [School of Pharmaceutical Science, Guangxi Medical University, Nanning, Guangxi 530021 (China); Su, Xiao-Chuan; Liao, Yan-Hua; Lei, Ning-Sheng [Guangxi Zhuang Autonomous Region Center for Disease Prevention and Control, Nanning, Guangxi 530028 (China); Liang, Yong-Hong [School of Pharmaceutical Science, Guangxi Medical University, Nanning, Guangxi 530021 (China); Zhou, Shao-Huan; Lin, Wen-Si; Chen, Jie [Guangxi Zhuang Autonomous Region Center for Disease Prevention and Control, Nanning, Guangxi 530028 (China); Feng, Yu-Qi [Key Laboratory of Analytical Chemistry for Biology and Medicine, Ministry of Education, Department of Chemistry, Wuhan University, Wuhan 430072 (China); Tang, Yang, E-mail: tycarson2@163.com [Guangxi Zhuang Autonomous Region Center for Disease Prevention and Control, Nanning, Guangxi 530028 (China)

    2017-06-01

    Aflatoxins (AFs) are highly toxic, mutagenic, carcinogenic, and teratogenic secondary metabolites produced by the toxigenic fungi Aspergillus flavus and Aspergillus parasiticus. AFs tend to contaminate a wide range of foods which is a serious and recurring food safety problem worldwide. Currently, immunoaffinity chromatography (IAC) has become the most conventional sample clean-up method for determining AFs in foodstuffs. However, IAC method is limited in the large-scale food analysis because it requires the use of expensive disposable cartridges and the IA procedure is time-consuming. Herein, to achieve the cost-effective determination of AFs in edible oils, we developed a promising solid-phase extraction (SPE) method based on commercially available humic acid-bonded silica (HAS) sorbent, followed by high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) analysis. In HAS-SPE, AFs can be captured by the HAS sorbent with both hydrophobic and hydrophilic interactions, whereas the oil matrix was captured only with the hydrophobic interactions. The oil matrix can be sufficiently washed off with isopropanol, while the AFs were still retained on the SPE packing, thus achieving selective extraction of AFs and clean-up of oil matrices. Under the optimal conditions of HAS-SPE, satisfactory recoveries ranging from 82% to 106% for four AFs (B{sub 1}, B{sub 2}, G{sub 1}, and G{sub 2}) were achieved in various oil matrices, containing blended oil, tea oil, rapeseed oil, peanut oil, sunflower seed oil, corn oil, blended olive oil, rice oil, soybean oil, and sesame oil. Only minor matrix effects ranging from 99% to 105% for four AFs were observed. Moreover, the LODs of AFs between 0.012 and 0.035 μg/kg completely meet the regulatory levels fixed by the EU, China or other countries. The methodology was further validated for assaying the naturally contaminated peanut oils, and consistent results between the HAS-SPE and the referenced IAC were

  14. Mercury removal sorbents

    Science.gov (United States)

    Alptekin, Gokhan

    2016-03-29

    Sorbents and methods of using them for removing mercury from flue gases over a wide range of temperatures are disclosed. Sorbent materials of this invention comprise oxy- or hydroxyl-halogen (chlorides and bromides) of manganese, copper and calcium as the active phase for Hg.sup.0 oxidation, and are dispersed on a high surface porous supports. In addition to the powder activated carbons (PACs), this support material can be comprised of commercial ceramic supports such as silica (SiO.sub.2), alumina (Al.sub.2O.sub.3), zeolites and clays. The support material may also comprise of oxides of various metals such as iron, manganese, and calcium. The non-carbon sorbents of the invention can be easily injected into the flue gas and recovered in the Particulate Control Device (PCD) along with the fly ash without altering the properties of the by-product fly ash enabling its use as a cement additive. Sorbent materials of this invention effectively remove both elemental and oxidized forms of mercury from flue gases and can be used at elevated temperatures. The sorbent combines an oxidation catalyst and a sorbent in the same particle to both oxidize the mercury and then immobilize it.

  15. Deposition of GdVO4:Eu3+ nanoparticles on silica nanospheres by a simple sol gel method

    Science.gov (United States)

    Liu, Guixia; Hong, Guangyan; Wang, Jinxian; Dong, Xiangting

    2006-07-01

    The deposition and coating of GdVO4:Eu3+ nanoparticles on spherical silica was carried out using a simple sol-gel method at low temperature. The GdVO4:Eu3+-coated silica composites obtained were characterized by differential thermal analysis (DTA), thermogravimetric (TG) analysis, x-ray diffraction (XRD), Fourier-transform IR spectroscopy (FT-IR), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), photoluminescence spectra, and kinetic decay. It is found that the ~5 nm GdVO4:Eu3+ nanoparticles coating the silica spheres are crystal in the as-prepared samples and the crystallinity increases with increasing annealing temperature. The composites obtained are spherical in shape with an average size of 100 nm. The GdVO4:Eu3+ nanoparticles are linked with silica cores by a chemical bond. The photoluminescence spectra of the obtained GdVO4:Eu3+-coated silica composites are similar to those of the bulk GdVO4:Eu3+ phosphors. The strongest peak is near 617 nm, which indicates that Eu3+ is located in the low symmetry site with non-inversion centre.

  16. Thermal and Mechanical Properties of Novolac-Silica Hybrid Aerogels Prepared by Sol-Gel Polymerization in Solvent-Saturated Vapor Atmosphere

    Directory of Open Access Journals (Sweden)

    Mohamad Mehdi Seraji1, Seraji

    2015-05-01

    Full Text Available Nowadays organic–inorganic hybrid aerogel materials have attracted increasing interests due to improved thermal and mechanical properties. In the present research, initially, novolac type phenolic resin-silica hybrid gels with different solid concentrations were synthesized using sol-gel polymerization in solvent-saturatedvapor atmosphere. The hybrid gels were dried at air atmosphere through ambient drying process. This method removed the need for costly and risky supercritical drying process. The yields of the obtained hybrid aerogels increased with less shrinkage in comparison with conventional sol-gel process. The precursor of silica phase in this study was tetraethoxysilane and inexpensive novolac resin was used as a reinforcing phase. The results of FTIR analysis confirmed the simultaneous formation of silica and novolac gels in the hybrid systems. The resultant hybrid aerogels showed a nanostructure hybrid network with high porosity (above 80% and low density (below 0.25 g/cm3. Nonetheless, higher content of silica resulted in more shrinkage in the hybrid aerogel structure due to the tendency of the silica network to shrink more during gelation and drying process. The SEM images of samples exhibited a continuous network of interconnected colloidal particles formed during sol-gel polymerization with mean particle size of less than 100 nanometers. Si mapping analysis showed good distribution of silica phase throughout the hybrid structure. The results demonstrated improvements in insulation properties and thermal stability of novolac-silica aerogel with increasing the silica content. The results of compressive strength showed that the mechanical properties of samples declined with increasing the silica content.

  17. Aerogel sorbents

    Energy Technology Data Exchange (ETDEWEB)

    Begag, Redouane; Rhine, Wendell E.; Dong, Wenting

    2018-04-03

    The current invention describes methods and compositions of various sorbents based on aerogels of various silanes and their use as sorbent for carbon dioxide. Methods further provide for optimizing the compositions to increase the stability of the sorbents for prolonged use as carbon dioxide capture matrices.

  18. Determination of Benzo[α]pyrene in Edible Oil Using Tetraoxocalix[2]arene[2]triazine Bonded Silica SPE Sorbent.

    Science.gov (United States)

    Guo, Yun; Zhao, Wen-Jie; Deng, Zhi-Fen; Hongbo, Wang; Peng, Bin; Ma, Xue; Lan, Chen; Zhang, Shu-Sheng

    2018-06-01

    Benzo[α]pyrene (BaP) is a well-known carcinogen in edible oil. In this study, a method combined solid-phase extraction (SPE) with fluorescent detection was developed using tetraoxocalix[2]arene[2]triazine sorbent (SiO 2 -OCA) for the clean-up and enrichment of BaP. The interaction between SiO 2 -OCA and BaP involves a donor-acceptor complex mechanism. The experimental procedure was as follows: BaP was extracted from edible oil with DMF/H 2 O (9:1, v/v). Then, the ratio of DMF/H 2 O was adjusted to 1:2 prior to SPE. The final concentrate was analyzed using a fluorescence detector at excitation and emission wavelengths of 255 and 420 nm. The method was fully validated. The linearity was in the range of 0.1-100 μg kg -1 with a coefficient of 0.999. The limits of detection and quantification were 0.03 and 0.1 μg kg -1 , respectively. The average recoveries were in the range of 88.0-122.3%. The intraday and interday precisions were 6.8% and 9.2%, respectively. Compared with other methods, the method reported in this article shows a good detection limit, high reproducibility and recovery, and linearity over a broad concentration range. This established method was also applied to evaluate real samples. The concentration of six tested samples was below 5 μg kg -1 .

  19. Synthesis of Fluorite (CaF2 Crystal from Gypsum Waste of Phosphoric Acid Factory in Silica Gel

    Directory of Open Access Journals (Sweden)

    Mohammad Misbah Khunur

    2012-06-01

    Full Text Available This paper report the synthesis and characterization of fluorite single crystal prepared from gypsum waste of phosphoric acid production in silica gel. Instead of its high calcium, gypsum was used to recycle the waste which was massively produces in the phosphoric acid production. The gypsum waste, the raw material of CaCl2 supernatant, was dissolved in concentrated HCl and then precipitated as calcium oxalate (CaC2O4 by addition of ammonium oxalate. The CaCl2 was obtained by dissolving the CaC2O4 with HCl 3M. The crystals were grown at room temperature in silica gel and characterized by AAS, FTIR and powder XRD. The optimum crystal growth condition, which is pH of gel, CaCl2 concentration and growth time, were investigated. The result shows that at optimum condition of pH 5.80, CaCl2 concentrations of 1.2 M, and growth time of 144 hours, colorless crystals with the longest size of 3 mm, were obtained (72.57%. Characterization of the synthesized crystal by AAS indicates that the obtained crystal has high purity. Meanwhile, analysis by FTIR spectra shows a Ca–F peak at 775 cm-1, and powder-XRD analysis confirms that the obtained crystal was fluorite (CaF2. © 2012 BCREC UNDIP. All rights reservedReceived: 11st April 2012; Revised: 4th June 2012; Accepted: 13rd June 2012[How to Cite: M.M. Khunur, A. Risdianto, S. Mutrofin, Y.P. Prananto. (2012. Synthesis of Fluorite (CaF2 Crystal from Gypsum Waste of Phosphoric Acid Factory in Silica Gel. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (1: 71-77.  doi:10.9767/bcrec.7.1.3171.71-77 ][How to Link / DOI: http://dx.doi.org/10.9767/bcrec.7.1.3171.71-77 ] | View in 

  20. Low-cost humic acid-bonded silica as an effective solid-phase extraction sorbent for convenient determination of aflatoxins in edible oils.

    Science.gov (United States)

    Zhou, Neng-Zhi; Liu, Ping; Su, Xiao-Chuan; Liao, Yan-Hua; Lei, Ning-Sheng; Liang, Yong-Hong; Zhou, Shao-Huan; Lin, Wen-Si; Chen, Jie; Feng, Yu-Qi; Tang, Yang

    2017-06-01

    Aflatoxins (AFs) are highly toxic, mutagenic, carcinogenic, and teratogenic secondary metabolites produced by the toxigenic fungi Aspergillus flavus and Aspergillus parasiticus. AFs tend to contaminate a wide range of foods which is a serious and recurring food safety problem worldwide. Currently, immunoaffinity chromatography (IAC) has become the most conventional sample clean-up method for determining AFs in foodstuffs. However, IAC method is limited in the large-scale food analysis because it requires the use of expensive disposable cartridges and the IA procedure is time-consuming. Herein, to achieve the cost-effective determination of AFs in edible oils, we developed a promising solid-phase extraction (SPE) method based on commercially available humic acid-bonded silica (HAS) sorbent, followed by high performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) analysis. In HAS-SPE, AFs can be captured by the HAS sorbent with both hydrophobic and hydrophilic interactions, whereas the oil matrix was captured only with the hydrophobic interactions. The oil matrix can be sufficiently washed off with isopropanol, while the AFs were still retained on the SPE packing, thus achieving selective extraction of AFs and clean-up of oil matrices. Under the optimal conditions of HAS-SPE, satisfactory recoveries ranging from 82% to 106% for four AFs (B 1 , B 2 , G 1 , and G 2 ) were achieved in various oil matrices, containing blended oil, tea oil, rapeseed oil, peanut oil, sunflower seed oil, corn oil, blended olive oil, rice oil, soybean oil, and sesame oil. Only minor matrix effects ranging from 99% to 105% for four AFs were observed. Moreover, the LODs of AFs between 0.012 and 0.035 μg/kg completely meet the regulatory levels fixed by the EU, China or other countries. The methodology was further validated for assaying the naturally contaminated peanut oils, and consistent results between the HAS-SPE and the referenced IAC were obtained. In

  1. Open-Source-Based 3D Printing of Thin Silica Gel Layers in Planar Chromatography.

    Science.gov (United States)

    Fichou, Dimitri; Morlock, Gertrud E

    2017-02-07

    On the basis of open-source packages, 3D printing of thin silica gel layers is demonstrated as proof-of-principle for use in planar chromatography. A slurry doser was designed to replace the plastic extruder of an open-source Prusa i3 printer. The optimal parameters for 3D printing of layers were studied, and the planar chromatographic separations on these printed layers were successfully demonstrated with a mixture of dyes. The layer printing process was fast. For printing a 0.2 mm layer on a 10 cm × 10 cm format, it took less than 5 min. It was affordable, i.e., the running costs for producing such a plate were less than 0.25 Euro and the investment costs for the modified hardware were 630 Euro. This approach demonstrated not only the potential of the 3D printing environment in planar chromatography but also opened new avenues and new perspectives for tailor-made plates, not only with regard to layer materials and their combinations (gradient plates) but also with regard to different layer shapes and patterns. As such an example, separations on a printed plane layer were compared with those obtained from a printed channeled layer. For the latter, 40 channels were printed in parallel on a 10 cm × 10 cm format for the separation of 40 samples. For producing such a channeled plate, the running costs were below 0.04 Euro and the printing process took only 2 min. All modifications of the device and software were released open-source to encourage reuse and improvements and to stimulate the users to contribute to this technology. By this proof-of-principle, another asset was demonstrated to be integrated into the Office Chromatography concept, in which all relevant steps for online miniaturized planar chromatography are performed by a single device.

  2. Morphology and properties of silica/novolac hybrid xerogels synthesized using sol–gel polymerization at solvent vapor-saturated atmosphere

    International Nuclear Information System (INIS)

    Seraji, Mohamad Mehdi; Seifi, Azadeh; Bahramian, Ahmad Reza

    2015-01-01

    Highlights: • Sol–gel polymerization in vapor of solvent saturated atmosphere is developed. • Highly porous novolac–silica hybrid xerogels are successfully synthesized. • Novolac–silica hybrid gel was dried in ambient condition with low shrinkage. • Required time for preparation of gel reduced from 5 days to about 5 h. • By incorporation of silica into the novolac xerogel structure, the pore size decreases. - Abstract: Highly porous novolac–silica hybrid xerogels were successfully synthesized via the novel method of sol–gel polymerization in solvent vapor-saturated atmosphere. This method removes the need for supercritical drying and yields the hybrid xerogels with reduced shrinkage in comparison with conventional sol–gel process. Tetraethoxysilane (TEOS) was used as the precursor of silica-based inorganic phase. The chemical and structural characterization of the prepared hybrid xerogels were performed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis, respectively. Thermal and mechanical properties of the hybrid samples were investigated by differential scanning calorimetry (DSC), and compressive strength analysis. The resultant hybrid xerogels show a nanostructured colloidal hybrid network with high porosity (above 80%) and low density (below 0.25 g cm −3 ). Si mapping images shows the good distribution of silica phase throughout the hybrid structure

  3. Thermodynamics of organic molecule adsorption on sorbents modified with 5-hydroxy-6-methyluracil by inverse gas chromatography.

    Science.gov (United States)

    Gus'kov, Vladimir Yu; Gainullina, Yulia Yu; Ivanov, Sergey P; Kudasheva, Florida Kh

    2014-08-22

    The thermodynamic features of organic molecule adsorption from the gaseous phase of sorbents modified with 5-hydroxy-6-methyluracil (HMU) were studied. Molar internal energy and entropy of adsorption variation analyses showed that with every type surface, except for silica gel, layers of supramolecular structure have cavities equal in size with the ones revealed in HMU crystals by X-ray diffraction. Adsorption thermodynamics on HMU-modified sorbents depended on the amount of impregnated HMU and on the polarity, but not the porosity, of the initial sorbent. Polarity of the modified surface increased as a function of HMU quantity and initial sorbent mean pore size, but become appreciably lower if the initial surface is capable of hydrogen bonding. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Relationship between sol-gel conditions and enzyme stability: a case study with β-galactosidase/silica biocatalyst for whey hydrolysis.

    Science.gov (United States)

    Escobar, Sindy; Bernal, Claudia; Mesa, Monica

    2015-01-01

    The sol-gel process has been very useful for preparing active and stable biocatalysts, with the possibility of being reused. Especially those based on silica are well known. However, the study of the enzyme behavior during this process is not well understood until now and more, if the surfactant is involved in the synthesis mixture. This work is devoted to the encapsulation of β-galactosidase from Bacillus circulans in silica by sol-gel process, assisted by non-ionic Triton X-100 surfactant. The correlation between enzyme activity results for the β-galactosidase in three different environments (soluble in buffered aqueous reference solution, in the silica sol, and entrapment on the silica matrix) explains the enzyme behavior under stress conditions offered by the silica sol composition and gelation conditions. A stable β-galactosidase/silica biocatalyst is obtained using sodium silicate, which is a cheap source of silica, in the presence of non-ionic Triton X-100, which avoids the enzyme deactivation, even at 40 °C. The obtained biocatalyst is used in the whey hydrolysis for obtaining high value products from this waste. The preservation of the enzyme stability, which is one of the most important challenges on the enzyme immobilization through the silica sol-gel, is achieved in this study.

  5. Durable zinc oxide-containing sorbents for coal gas desulfurization

    Science.gov (United States)

    Siriwardane, Ranjani V.

    1996-01-01

    Durable zinc-oxide containing sorbent pellets for removing hydrogen sulfide from a gas stream at an elevated temperature are made up to contain titania as a diluent, high-surface-area silica gel, and a binder. These materials are mixed, moistened, and formed into pellets, which are then dried and calcined. The resulting pellets undergo repeated cycles of sulfidation and regeneration without loss of reactivity and without mechanical degradation. Regeneration of the pellets is carried out by contacting the bed with an oxidizing gas mixture.

  6. Preparation and characterization of quercetin-loaded silica microspheres stabilized by combined multiple emulsion and sol-gel processes

    Directory of Open Access Journals (Sweden)

    Kim Young Ho

    2015-01-01

    Full Text Available Despite exhibiting a wide spectrum of cosmeceutical properties, flavonoids and related compounds have some limitations related to their stability and solubility in distilledwater. In this project, we prepared silica microspheres using a novel method that uses polyol-in-oil-in-water (P/O/W emulsion and sol-gel methods as techniques for stabilizing quercetin. A stable microsphere suspension was successfully preparedusing a mixed solvent system comprising a polyol-phase medium for performing the sol-gel processing of tetraethyl orthosilicate (TEOS as an inorganic precursor with outer water phase. The morphology of the microsphere was evaluated using a scanning electron microscope (SEM, which showed a characteristic spherical particle shape with a smooth surface. Furthermore, SEM/EDSanalysis of a representative microsphere demonstrated that the inner structure of the silica microspheres was filled with quercetin. The mean diameter of the microsphere was in the range 20.6-35.0 μm, and the encapsulation efficiency ranged from 17.8% to 27.5%. The free and encapsulated quercetin samples were incubated in separateaqueous solutions at 25 and 42°C for 28 days. The residualcontent of the quercetin encapsulated by silica microspheres was 82% at 42°C. In contrast, that of the free quercetin stored at 42°C decreased to ~24%.

  7. Octadecyl functionalized core-shell magnetic silica nanoparticle as a powerful nanocomposite sorbent to extract urinary volatile organic metabolites.

    Science.gov (United States)

    Qiao, Zheng; Perestrelo, Rosa; Reyes-Gallardo, Emilia M; Lucena, R; Cárdenas, S; Rodrigues, João; Câmara, José S

    2015-05-08

    In this present study, magnetic Fe3O4@SiO2 nanoparticles (MNPs) functionalized with octadecyl groups (Fe3O4@SiO2-C18 NPs) were synthesized, characterized and employed, for the first time, as powerful nanosorbent to extract endogenous volatile organic metabolites (EVOMs) namely, hexanal, heptanal, decanal, benzaldehyde, 4-heptanone, 5-methyl-2-furfural and phenol, described as potential biomarkers of cancer, from human urine. By using co-precipitation, surface modification methods, the carbon-ferromagnetic nanocomposite was synthesized and characterized by infrared spectrum (IR) and transmission electron microscopy (TEM). By coupling with gas chromatography-mass spectrometry (GC-qMS), a reliable, sensitive and cost-effective method was validated. To test the extraction efficiency of the carbon-ferromagnetic nanocomposite toward urinary EVOMs experimental variables affecting the extraction performance, including nanosorbent amount, adsorption time, elution time, and nature of elution solvent, were investigated in detail. The extraction process was performed by dispersing Fe3O4@SiO2-C18 NPs into working solution containing targeted VOMs, and into urine samples, and then eluted with an adequate organic solvent. The eluate was collected, concentrated and analyzed by GC-qMS. Under the optimized conditions, the LODs and LOQs achieved were in the range of 9.7-57.3 and 32.4-190.9ng/mL, respectively. Calibration curves were linear (r(2)≥0. 988) over the concentration ranges from 0.25 to 250ng/mL. In addition, a satisfying reproducibility was achieved by evaluating the intra- and inter-day precisions with relative standard deviations (RSDs) less than 3 and 11%, respectively. The method also afforded satisfactory results in terms of the matrix effect (72.8-96.1%) and recoveries (accuracy) higher than 75.1% for most of the studied EVOMs. The Fe3O4@SiO2-C18 NPs-based sorbent extraction combined with GC-qMS revealed that the new nanosorbent had a strong ability to retain the

  8. Synthesis of nanocrystalline LaF3 doped silica glasses by hydrofluoric acid catalyzed sol–gel process

    International Nuclear Information System (INIS)

    Nagayama, Shuhei; Kajihara, Koichi; Kanamura, Kiyoshi

    2012-01-01

    Highlights: ► Silica glasses doped by LaF 3 nanocrystals are obtained by HF-catalyzed sol–gel method. ► The processing time (∼1 week) is much shorter than that of previous studies. ► The uptake of SiF groups in the glass matrix greatly reduces the SiOH concentration. ► Effects of sintering conditions and properties of Er 3+ -doped samples are presented. - Abstract: Silica glasses doped with LaF 3 nanocrystals were prepared by HF-catalyzed sol–gel method. HF was used both as fluorine source and as catalyst of the sol–gel reaction, making it possible to shorten the processing time with reducing the concentration of SiOH groups to ∼10 18 cm −3 . The resultant glasses are transparent at visible spectral range, and the optical loss at the ultraviolet absorption edge is dominated by the Rayleigh scattering from LaF 3 crystallites. The size of LaF 3 crystallites increases with an increase in the sintering temperature and time, and is smaller than ∼40 nm in samples showing good visible transparency. Green upconversion photoluminescence is observed in an Er 3+ -doped sample under excitation at 980 nm.

  9. Surface-enhanced Raman scattering of amorphous silica gel adsorbed on gold substrates for optical fiber sensors

    Science.gov (United States)

    Degioanni, S.; Jurdyc, A. M.; Cheap, A.; Champagnon, B.; Bessueille, F.; Coulm, J.; Bois, L.; Vouagner, D.

    2015-10-01

    Two kinds of gold substrates are used to produce surface-enhanced Raman scattering (SERS) of amorphous silica obtained via the sol-gel route using tetraethoxysilane Si(OC2H5)4 (TEOS) solution. The first substrate consists of a gold nanometric film elaborated on a glass slide by sputter deposition, controlling the desired gold thickness and sputtering current intensity. The second substrate consists of an array of micrometer-sized gold inverted pyramidal pits able to confine surface plasmon (SP) enhancing electric field, which results in a distribution of electromagnetic energy inside the cavities. These substrates are optically characterized to observe SPR with, respectively, extinction and reflectance spectrometries. Once coated with thin layers of amorphous silica (SiO2) gel, these samples show Raman amplification of amorphous SiO2 bands. This enhancement can occur in SERS sensors using amorphous SiO2 gel as shells, spacers, protective coatings, or waveguides, and represents particularly a potential interest in the field of Raman distributed sensors, which use the amorphous SiO2 core of optical fibers as a transducer to make temperature measurements.

  10. Removal of Heavy Metals from Aqueous Solution Using Novel Nanoengineered Sorbents: Self-Assembled Carbamoylphosphonic Acids on Mesoporous Silica

    International Nuclear Information System (INIS)

    Yantasee, Wassana; Lin, Yuehe; Fryxell, Glen E.; Busche, Brad J.; Birnbaum, Jerome C.

    2003-01-01

    Self-assembled monolayers of carbamoylphosphonic acids (acetamide phosphonic acid and propionamide phosphonic acid) on mesoporous silica supports were studied as potential absorbents for heavy and transition metal ions in aqueous wastes. The adsorption capacity, selectivity, and kinetics of the materials in sequestering metal ions, including Cd2+, Co2+, Cu2+, Cr3+, Pb2+, Ni2+, Zn2+, and Mn2+, were measured in batch experiments with excess sodium ion. The solution pH ranged from 2.2 to 5.5. The kinetics study shows that the adsorption reached equilibrium in seconds, indicating that there is little resistance to mass transfer, intraparticle diffusion, and surface chemical reaction. The competitive adsorption study found the phosphonic acid-SAMMS to have an affinity for divalent metal ions in decreasing order of Pb2+ > Cu2+ > Mn2+ > Cd2+ > Zn2+ > Co2+ > Ni2+. The measured Cd2+ adsorption isotherm was of the Langmuirian type and had a saturation binding capacity of 0.32 mmol/g

  11. Adjustable rheology of fumed silica dispersion in urethane prepolymers: Composition-dependent sol and gel behaviors and energy-mediated shear responses

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Zhong, E-mail: 11329038@zju.edu.cn; Song, Yihu, E-mail: s-yh0411@zju.edu.cn; Wang, Xiang, E-mail: 11229036@zju.edu.cn; Zheng, Qiang, E-mail: zhengqiang@zju.edu.cn [MOE Key Laboratory of Macromolecule Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2015-07-15

    Variation of colloidal and interfacial interactions leads to a microstructural diversity in fumed silica dispersions exhibiting absolutely different sol- or gel-like rheological responses. In this study, fumed silicas with different surface areas (200–400 m{sup 2}/g) and surface characteristics (hydrophilic or hydrophobic) are dispersed into moisture-cured polyurethane. The microstructures investigated using transmission electron microscope are associated perfectly with three different rheological behaviors: (i) Sols with well-dispersed silica aggregates, (ii) weak gels with agglomerate-linked networks, and (iii) strong gels with concentrated networks of large agglomerates. Though sols and gels are well distinguished by shear thickening or sustained thinning response through steady shear flow test, it is interesting that the sols and weak gels exhibit a uniform modulus plateau-softening-hardening-softening response with increasing dynamic strain at frequency 10 rad s{sup −1} while the strong gels show a sustained softening beyond the linear regime. Furthermore, the onset of softening and hardening can be normalized: The two softening are isoenergetic at mechanical energies of 0.3 J m{sup −3} and 10 kJ m{sup −3}. On the other hand, the hardening is initiated by a critical strain of 60%. The mechanisms involved in the generation of the sol- and the gel-like dispersions and their structural evolutions during shear are thoroughly clarified in relation to the polyols, the characteristic and content of silica and the curing catalysts.

  12. Determination of Copper in Different Ethanolic Matrices Using a Chloropropyl Silica Gel Modified with a Nanostructured Cubic Octa(3-aminopropyloctasilsesquioxane

    Directory of Open Access Journals (Sweden)

    Devaney Ribeiro Do Carmo

    2013-01-01

    Full Text Available The chloropropyl silica gel was modified with octa(3-aminopropyloctasilsesquioxane and characterized by Fourier transform infrared (FTIR spectroscopy, nuclear magnetic resonance (NMR, spectroscopies, and surface and area porosity. The specific sorption capacity of metallic ions (Cu2+ and Ni2+ increases in the following solvent order: water < ethanol 42% < ethanol < ketone. The high values of the constant (K in the order of 103 L mol−1 suggested the high adsorbent capacity of the modified silica (SGAPC for Cu2+ and Ni2+. SGAPC was applied to a separation column and shows recoveries of around 100% of copper in samples of sugar cane spirit, vodka, ginger brandy, and ethanol fuel.

  13. Defect-induced luminescence in sol-gel silica samples doped with Co(II) at different concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Jimenez-Sandoval, S. [Centro de Investigacion y Estudios Avanzados, Queretaro, Apdo. Postal 1-798, Queretaro, Qro. 76001 (Mexico); Estevez, M. [Fisica Aplicada y Tecnologia Avanzada, UNAM, Apdo. Postal 1-1010, Queretaro, Qro. 76000 (Mexico); Pacheco, S. [Instituto Mexicano del Petroleo, Av. 100 metros (Mexico); Vargas, S. [Fisica Aplicada y Tecnologia Avanzada, UNAM, Apdo. Postal 1-1010, Queretaro, Qro. 76000 (Mexico); Rodriguez, R. [Fisica Aplicada y Tecnologia Avanzada, UNAM, Apdo. Postal 1-1010, Queretaro, Qro. 76000 (Mexico)], E-mail: rogelior@servidor.unam.mx

    2007-12-20

    The defect-induced luminescence properties of silica samples prepared by the sol-gel method and doped with Co(II) are reported. Silica monoliths doped with different concentrations of Co(II) were laser irradiated (He-Ne 632.8 nm) producing fluorescence. However, this fluorescence is exponentially reduced with the irradiation time, to practically disappear. The rate the fluorescence decays can be well modeled with a double exponential function of the irradiation time, containing two different relaxation times; a baseline is also required to take into account some residual fluorescence. The characteristic times involved in this luminescence quenching process are in the range of seconds. This luminescence suppression can be associated to the local heating produced by the laser irradiation when focused in a small area (2 {mu}m in diameter) on the sample. This heating process reduces physical (grain boundaries, surface states) and chemical (oxygen vacancies produced by the dopant) defects in the sample.

  14. Determination of picomolar beryllium levels in seawater with inductively coupled plasma mass spectrometry following silica-gel preconcentration

    Energy Technology Data Exchange (ETDEWEB)

    Tazoe, Hirofumi, E-mail: tazoe@cc.hirosaki-u.ac.jp [Department of Radiation Chemistry, Institute of Radiation Emergency Mediation, Hirosaki University, 66-1 Hon-cho, Hirosaki, Aomori 036-8564 (Japan); College of Humanities and Sciences, Nihon University, 3-25-40, Sakurajosui, Setagaya-ku, Tokyo 156-8550 (Japan); Yamagata, Takeyasu [College of Humanities and Sciences, Nihon University, 3-25-40, Sakurajosui, Setagaya-ku, Tokyo 156-8550 (Japan); Obata, Hajime [Atmosphere and Ocean Research Institute, The Tokyo University, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8564 (Japan); Nagai, Hisao [College of Humanities and Sciences, Nihon University, 3-25-40, Sakurajosui, Setagaya-ku, Tokyo 156-8550 (Japan)

    2014-12-10

    Highlights: • We developesd the simplest and robust SPE method for ultra low picomolar level beryllium in seawater. • Just silica gel column can quantitatively adsorb beryllium in neutral pH condition containing natural seawater. • EDTA solution can eliminate seawater matrixes retaining Be in the column, which optimize to ICP-MS detemination. • Accurate and precise Be data have been obtained for natural seawater from North Pacific Ocean. - Abstract: A robust and rapid method for the determination of natural levels of beryllium (Be) in seawater was developed to facilitate mapping Be concentrations in the ocean. A solid-phase extraction method using a silica gel column was applied for preconcentration and purification of Be in seawater prior to determination of Be concentrations with inductively coupled plasma mass spectrometry (ICP-MS). Be was quantitatively adsorbed onto silica gel from solutions with pH values ranging from 6.3 to 9, including natural seawater. The chelating agent ethylenediamine tetraacetic acid was used to remove other ions in the seawater matrix (Na, Mg, and Ca) that interfere with the ICP-MS analysis. The reproducibility of the method was 3% based on triplicate analyses of natural seawater samples, and the detection limit was 0.4 pmol kg{sup −1} for 250 mL of seawater, which is sufficient for the analysis of seawater in the open ocean. The method was then used to determine the vertical profile of Be in the eastern North Pacific Ocean, which was found to be a recycled-type profile in which the Be concentration increased with depth from the surface (7.2 pmol kg{sup −1} at <200 m) to deep water (29.2 pmol kg{sup −1} from 3500 m to the bottom)

  15. Determination of picomolar beryllium levels in seawater with inductively coupled plasma mass spectrometry following silica-gel preconcentration

    International Nuclear Information System (INIS)

    Tazoe, Hirofumi; Yamagata, Takeyasu; Obata, Hajime; Nagai, Hisao

    2014-01-01

    Highlights: • We developesd the simplest and robust SPE method for ultra low picomolar level beryllium in seawater. • Just silica gel column can quantitatively adsorb beryllium in neutral pH condition containing natural seawater. • EDTA solution can eliminate seawater matrixes retaining Be in the column, which optimize to ICP-MS detemination. • Accurate and precise Be data have been obtained for natural seawater from North Pacific Ocean. - Abstract: A robust and rapid method for the determination of natural levels of beryllium (Be) in seawater was developed to facilitate mapping Be concentrations in the ocean. A solid-phase extraction method using a silica gel column was applied for preconcentration and purification of Be in seawater prior to determination of Be concentrations with inductively coupled plasma mass spectrometry (ICP-MS). Be was quantitatively adsorbed onto silica gel from solutions with pH values ranging from 6.3 to 9, including natural seawater. The chelating agent ethylenediamine tetraacetic acid was used to remove other ions in the seawater matrix (Na, Mg, and Ca) that interfere with the ICP-MS analysis. The reproducibility of the method was 3% based on triplicate analyses of natural seawater samples, and the detection limit was 0.4 pmol kg −1 for 250 mL of seawater, which is sufficient for the analysis of seawater in the open ocean. The method was then used to determine the vertical profile of Be in the eastern North Pacific Ocean, which was found to be a recycled-type profile in which the Be concentration increased with depth from the surface (7.2 pmol kg −1 at <200 m) to deep water (29.2 pmol kg −1 from 3500 m to the bottom)

  16. Qualitative infrared spectral analysis of products adsorbed by silica gel from ditolylmethane coolant and their adsorption isotherm

    International Nuclear Information System (INIS)

    Ermakov, V.A.; Benderskaya, O.S.

    1987-01-01

    The IR-spectral analysis has been applied to study the products adsorbed from ditolylmethane first-circuit coolant, as well as from still bottoms after coolant distillation on silicagel of various makes. The qualitative study of desorbate IR-spectra has shown that they refer to the classes of arylaldehydes, diarylketones and carbonic acids. Under actual conditions first-circuit reactor coolant also has a wide set of products of its radiolysis, therefore the spectrum of coolant oxidaton products must be wider. It is noted that adsorption on silica gel, ASK of oxygen-bearing compounds which are present in ditolyl methane coolant has 2 stages

  17. Evaluation of bi-functionalized mesoporous silicas as reversed phase/cation-exchange mixed-mode sorbents for multi-residue solid phase extraction of veterinary drug residues in meat samples.

    Science.gov (United States)

    Casado, Natalia; Pérez-Quintanilla, Damián; Morante-Zarcero, Sonia; Sierra, Isabel

    2017-04-01

    A SBA-15 type mesoporous silica was synthesized and bi-functionalized with octadecylsilane (C18) or octylsilane (C8), and sulfonic acid (SO 3 - ) groups in order to obtain materials with reversed-phase/strong cation-exchange mixed-mode retention mechanism. The resulting hybrid materials (SBA-15-C18-SO 3 - and SBA-15-C8-SO 3 - ) were comprehensively characterized. They showed high surface area, high pore volume and controlled porous size. Elemental analysis of the materials revealed differences in the amount of C18 and C8. SBA-15-C18-SO 3 - contained 0.19mmol/g of C18, while SBA-15-C8-SO 3 - presented 0.54mmol/g of C8. The SO 3 - groups anchored to the silica surface of the pore walls were 0.20 and 0.09mmol/g, respectively. The bi-functionalized materials were evaluated as SPE sorbents for the multi-residue extraction of 26 veterinary drug residues in meat samples using ultra-high-performance liquid chromatography coupled to mass spectrometry detector (UHPLC-MS/MS). Different sorbent amounts (100 and 200mg) and organic solvents were tested to optimize the extraction procedure. Both silicas showed big extraction potential and were successful in the extraction of the target analytes. The mixed-mode retention mechanism was confirmed by comparing both silicas with SBA-15 mesoporous silica mono-functionalized with C18 and C8. Best results were achieved with 200mg of SBA-15-C18-SO 3 - obtaining recoveries higher than 70% for the majority of analytes. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Iodine, krypton and xenon retention efficiencies of silver impregnated silica gel media with different silver loadings and under different test conditions

    Energy Technology Data Exchange (ETDEWEB)

    Motes, B G; Fernandez, S J; Tkachyk, J W

    1983-02-01

    The purpose of an independent study conducted by Exxon Nuclear Idaho, Co. (ENICO) was to evaluate a silver impregnated silica gel adsorption medium associated with a radioiodine air sampler developed at Brookhaven National Laboratory (BNL). Specifically, ENICO's responsibility was to evaluate the iodine and noble gas retention efficiencies of the adsorption medium. The evaluation was comprised of a four-phase program: 1) test assemblies capable of challenging the silver silica gel filled adsorber canister with radioiodine species or noble gases at flow rates up to 10 scfm and relative humidities up to 83% were constructed; 2) more than 45 kgs of the 4 and 8% silver impregnated silica gel were prepared and characterized for particle size distribution, bulk silver content, bulk density, and silver content by particle size; 3) iodine species retention efficiencies of the silver silica gel were determined; and 4 krypton and xenon retention efficiencies were measured. The iodine species retention efficiencies were greater than 90% under most conditions. A combination of flow rates >5 scfm and 4% silver loaded silica gel reduced the methyl iodide retention efficiency to less than 90%. The retention efficiencies for both krypton and xenon were on the order of 8 x 10{sup -2}% and were not affected greatly by any test variable except test duration. A reduced retention efficiency with increased test durations indicates adsorption equilibrium may be established within five minutes. (author)

  19. Iodine, krypton and xenon retention efficiencies of silver impregnated silica gel media with different silver loadings and under different test conditions

    International Nuclear Information System (INIS)

    Motes, B.G.; Fernandez, S.J.; Tkachyk, J.W.

    1983-02-01

    The purpose of an independent study conducted by Exxon Nuclear Idaho, Co. (ENICO) was to evaluate a silver impregnated silica gel adsorption medium associated with a radioiodine air sampler developed at Brookhaven National Laboratory (BNL). Specifically, ENICO's responsibility was to evaluate the iodine and noble gas retention efficiencies of the adsorption medium. The evaluation was comprised of a four-phase program: 1) test assemblies capable of challenging the silver silica gel filled adsorber canister with radioiodine species or noble gases at flow rates up to 10 scfm and relative humidities up to 83% were constructed; 2) more than 45 kgs of the 4 and 8% silver impregnated silica gel were prepared and characterized for particle size distribution, bulk silver content, bulk density, and silver content by particle size; 3) iodine species retention efficiencies of the silver silica gel were determined; and 4 krypton and xenon retention efficiencies were measured. The iodine species retention efficiencies were greater than 90% under most conditions. A combination of flow rates >5 scfm and 4% silver loaded silica gel reduced the methyl iodide retention efficiency to less than 90%. The retention efficiencies for both krypton and xenon were on the order of 8 x 10 -2 % and were not affected greatly by any test variable except test duration. A reduced retention efficiency with increased test durations indicates adsorption equilibrium may be established within five minutes. (author)

  20. Preparation of silane-functionalized silica films via two-step dip coating sol–gel and evaluation of their superhydrophobic properties

    International Nuclear Information System (INIS)

    Ramezani, Maedeh; Vaezi, Mohammad Reza; Kazemzadeh, Asghar

    2014-01-01

    Highlights: • Superhydrophobic silica film was prepared by sol–gel process. • The surfaces exhibited superhydrophobicity with water contact angle greater than 150°. • AFM images showed the roughness increases with increasing the percentage of silylation agent. • Before and after modification, the particle size of silica was lower than 50 nm. - Graphical abstract: Schematic illustration of the surface modification of the silica nanoparticle by iso-OTMS on the glass substrate. - Abstract: In this paper, we study the two-step dip coating via a sol–gel process to prepare superhydrophobic silica films on the glass substrate. The water repellency of the silica films was controlled by surface silylation method using isooctyltrimethoxysilane (iso-OTMS) as a surface modifying agent. Silica alcosol was synthesized by keeping the molar ratio of ethyltriethoxysilane (ETES) precursor, ethanol (EtOH) solvent, water (H 2 O) was kept constant at 1:36:6.6 respectively, with 6 M NH 4 OH throughout the experiment and the percentages of hydrophobic agent in hexane bath was varied from 0 to 15 vol.%. The static water contact angle values of the silica films increased from 108° to 160° with an increase in the vol.% of iso-OTMS. At 15 vol%. of iso-OTMS, the silica film shows static water contact angle as high as 160°. The superhydrophobic silica films are thermally stable up to 440 °C and above this temperature, the silica films lose superhydrophobicity. By controlling the primer particle size of SiO 2 about 26 nm, leading to decrease the final size of silica nanoparticles after modification of nanoparticles by isooctyltrimethoxysilane about 42 nm. The films are transparent and have uniform size on the surface. The silica films have been characterized by atomic force microscopy (AFM), fourier transform infrared spectroscopy (FT-IR), transparency, contact angle measurement (CA), Zeta-potential, Thermal stability by TG–DTA analysis

  1. Sorbent suppliers

    International Nuclear Information System (INIS)

    Vedder, M.

    1994-01-01

    Sorbents are used to absorb or contain spilled and leaking chemicals, oils, lubricants and other process fluids. They are commonly used around the base of machinery in industrial applications, and in remediating oil spills on land and water. Sorbents are made from biodegradable, inorganic or synthetic materials. Organic materials include corn cobs, wood pulp, paper fiber and cotton. Inorganic materials include clay, perlite, expanded silicates and expanded mica. Synthetic sorbents are made from petroleum- or plastic-based materials such as polyurethane, polyethylene or polypropylene. Sorbents are available in a variety of forms, including pads, rolls, booms, pillows and loose particulate

  2. Experimental study of the synthesis and characterisation of silica nanoparticles via the sol-gel method

    International Nuclear Information System (INIS)

    Tabatabaei, S; Shukohfar, A; Aghababazadeh, R; Mirhabibi, A

    2006-01-01

    Silica nano-particles were synthesised by chemical methods from tetraethylorthosilicate (TEOS), ethanol (C 2 H 5 OH) and deionized water in the presence of ammonia as catalyst at room temperature. The morphology and structure of colloidal silica particles formed depend on the molar ratio of reagents. The formation of silica particles has been investigated using different solvents: ethanol and ethanol-glycerol. The nature and morphology of particles was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD)

  3. Catalytic activity of acid and base with different concentration on sol-gel kinetics of silica by ultrasonic method.

    Science.gov (United States)

    Das, R K; Das, M

    2015-09-01

    The effects of both acid (acetic acid) and base (ammonia) catalysts in varying on the sol-gel synthesis of SiO2 nanoparticles using tetra ethyl ortho silicate (TEOS) as a precursor was determined by ultrasonic method. The ultrasonic velocity was received by pulsar receiver. The ultrasonic velocity in the sol and the parameter ΔT (time difference between the original pulse and first back wall echo of the sol) was varied with time of gelation. The graphs of ln[ln1/ΔT] vs ln(t), indicate two region - nonlinear region and a linear region. The time corresponds to the point at which the non-linear region change to linear region is considered as gel time for the respective solutions. Gelation time is found to be dependent on the concentration and types of catalyst and is found from the graphs based on Avrami equation. The rate of condensation is found to be faster for base catalyst. The gelation process was also characterized by viscosity measurement. Normal sol-gel process was also carried out along with the ultrasonic one to compare the effectiveness of ultrasonic. The silica gel was calcined and the powdered sample was characterized with scanning electron microscopy, energy dispersive spectra, X-ray diffractogram, and FTIR spectroscopy. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Silica-gel structural characterization during the initial phases of gelation and drying; Caracterizacao estrutural de geis de silica durante as etapas iniciais de gelacao e secagem

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Max Passos

    1997-12-31

    For centuries, glasses and ceramics have been made via melting or solid state reactions at temperatures above 100 deg C. The sol-gel process offers new approaches to the synthesis of glasses and ceramics, combining control of composition and structure at the molecular level with the ability to shape materials in bulk, powder, fiber and thin-film forms. The growth of sol-gel technology research is due to the many unique features of that class of materials. Major applications include optical elements and integrated optical devices, ceramic filters, membranes, supercondutors, magnetic, catalytic and manostructured materials to antioxidant, anticorrosion coatings and composite and biomedical materials. In this work a variety of techniques like spectroscopy, Raman spectroscopy, ultraviolet-visible spectroscopy, light scattering nuclear magnetic resonance, X ray diffraction and nitrogen adsorption have been employed to investigate the initial phase of the sol-gel transition of gamma ray irradiated tetramethoxysilane (TMOS) solutions and non-irradiated TMOS solution and to get information about the structure of the silica gels obtained under different gelation conditions. Typically the tetramethoxysilane solutions were prepared using a molar ratio of TMOS to demineralized water of 1 to 16. Some experiments were made under catalysed conditions. The mixing was carried out at room temperature. The turbidity and light scattering experiments on the polycondensation of tetramethoxysilane show that exists no drastic difference in the gelling time of a gamma ray irradiated and a non-irradiated TMOS+H{sub 2}O (1+16 M) solution. In the absence of a catalyst, the gelling time for both reactions occurs in about 3.30 h. When HNO{sub 3} (o.03 M) was used, the gelling time observed was 3 days. Raman and ultraviolet-visible spectroscopy show no drastic difference during the initial phase at the sol-gel transition under ambient temperature/pressure and under gamma radiation. The gels

  5. Silica-gel structural characterization during the initial phases of gelation and drying; Caracterizacao estrutural de geis de silica durante as etapas iniciais de gelacao e secagem

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Max Passos

    1996-12-31

    For centuries, glasses and ceramics have been made via melting or solid state reactions at temperatures above 100 deg C. The sol-gel process offers new approaches to the synthesis of glasses and ceramics, combining control of composition and structure at the molecular level with the ability to shape materials in bulk, powder, fiber and thin-film forms. The growth of sol-gel technology research is due to the many unique features of that class of materials. Major applications include optical elements and integrated optical devices, ceramic filters, membranes, supercondutors, magnetic, catalytic and manostructured materials to antioxidant, anticorrosion coatings and composite and biomedical materials. In this work a variety of techniques like spectroscopy, Raman spectroscopy, ultraviolet-visible spectroscopy, light scattering nuclear magnetic resonance, X ray diffraction and nitrogen adsorption have been employed to investigate the initial phase of the sol-gel transition of gamma ray irradiated tetramethoxysilane (TMOS) solutions and non-irradiated TMOS solution and to get information about the structure of the silica gels obtained under different gelation conditions. Typically the tetramethoxysilane solutions were prepared using a molar ratio of TMOS to demineralized water of 1 to 16. Some experiments were made under catalysed conditions. The mixing was carried out at room temperature. The turbidity and light scattering experiments on the polycondensation of tetramethoxysilane show that exists no drastic difference in the gelling time of a gamma ray irradiated and a non-irradiated TMOS+H{sub 2}O (1+16 M) solution. In the absence of a catalyst, the gelling time for both reactions occurs in about 3.30 h. When HNO{sub 3} (o.03 M) was used, the gelling time observed was 3 days. Raman and ultraviolet-visible spectroscopy show no drastic difference during the initial phase at the sol-gel transition under ambient temperature/pressure and under gamma radiation. The gels

  6. Silica Gel Coated Spherical Micro resonator for Ultra-High Sensitivity Detection of Ammonia Gas Concentration in Air.

    Science.gov (United States)

    Mallik, Arun Kumar; Farrell, Gerald; Liu, Dejun; Kavungal, Vishnu; Wu, Qiang; Semenova, Yuliya

    2018-01-26

    A silica gel coated microsphere resonator is proposed and experimentally demonstrated for measurements of ammonia (NH 3 ) concentration in air with ultra-high sensitivity. The optical properties of the porous silica gel layer change when it is exposed to low (parts per million (ppm)) and even ultra-low (parts per billion (ppb)) concentrations of ammonia vapor, leading to a spectral shift of the WGM resonances in the transmission spectrum of the fiber taper. The experimentally demonstrated sensitivity of the proposed sensor to ammonia is estimated as 34.46 pm/ppm in the low ammonia concentrations range from 4 ppm to 30 ppm using an optical spectrum analyser (OSA), and as 800 pm/ppm in the ultra-low range of ammonia concentrations from 2.5 ppb to 12 ppb using the frequency detuning method, resulting in the lowest detection limit (by two orders of magnitude) reported to date equal to 0.16 ppb of ammonia in air. In addition, the sensor exhibits excellent selectivity to ammonia and very fast response and recovery times measured at 1.5 and 3.6 seconds, respectively. Other attractive features of the proposed sensor are its compact nature, simplicity of fabrication.

  7. Performance comparison of a silica gel-water and activated carbon-methanol two beds adsorption chillers

    Directory of Open Access Journals (Sweden)

    Szelągowski Adam

    2017-01-01

    Full Text Available The aim of the study is to compare the efficiency of adsorption refrigerating equipment working with different working pairs. Adsorption cooling devices can operate with a relatively low temperature of heat sources while consuming only a small amount of electricity for the operation of auxiliary equipment. Refrigerants used in adsorption devices are substances that do not have a negative impact on the environment. All that makes that adsorption refrigeration seems to be a good solution for utilizing renewable and waste heat sources for cold production. To carry out the experiment the adsorption cooling device has been developed and researched in Institute of Heat Engineering at Warsaw University of Technology. The test bench consisted of two cylindrical adsorbers, condenser, evaporator, oil heater and two oil coolers. In order to perform the correct action it has been developed and implemented special control algorithm device, allowed to keep the temperature in the evaporator at a preset level. The unit tested for two sorption pairs: activated carbon – methanol, and silica gel – water. For activated carbon - methanol working pair it was obtained energy efficiency rating (EER equals to 0.14 and specific cooling power (SPC of 16 W/kg. For silica gel - water EER of refrigeration unit was 0.25 and SPC was equal to 208 W/kg.

  8. Novel Approach for Enhanced Scandium and Titanium Leaching Efficiency from Bauxite Residue with Suppressed Silica Gel Formation.

    Science.gov (United States)

    Alkan, Gözde; Yagmurlu, Bengi; Cakmakoglu, Seckin; Hertel, Tobias; Kaya, Şerif; Gronen, Lars; Stopic, Srecko; Friedrich, Bernd

    2018-04-04

    The need of light weight alloys for future transportation industry puts Sc and Ti under a sudden demand. While these metals can bring unique and desired properties to alloys, lack of reliable sources brought forth a supply problem which can be solved by valorization of the secondary resources. Bauxite residue (red mud), with considerable Ti and Sc content, is a promising resource for secure supply of these metals. Due to drawbacks of the direct leaching route from bauxite residue, such as silica gel formation and low selectivity towards these valuable metals, a novel leaching process based on oxidative leaching conditions, aiming more efficient and selective leaching but also considering environmental aspects via lower acid consumption, was investigated in this study. Combination of hydrogen peroxide (H 2 O 2 ) and sulfuric acid (H 2 SO 4 ) was utilized as the leaching solution, where various acid concentrations, solid-to-liquid ratios, leaching temperatures and times were examined in a comparative manner. Leaching with 2.5 M H 2 O 2 : 2.5 M H 2 SO 4 mixture at 90 °C for 30 min was observed to be the best leaching conditions with suppressed silica gel formation and the highest reported leaching efficiency with high S/L ratio for Sc and Ti; 68% and 91%; respectively.

  9. Catechol functionalized aminopropyl silica gel: synthesis, characterization and preconcentrative separation of uranium(VI) from thorium(IV)

    International Nuclear Information System (INIS)

    Metilda, P.; Mary Gladis, J.; Prasada Rao, T.P.

    2005-01-01

    A novel solid phase extractant is prepared by chemically immobilizing catechol with diazotized aminopropyl silica gel. The resulting catechol functionalized silica gel (CASG) was characterized by FTIR, and microanalysis and was used for selective enrichment of uranium(VI) from other inorganic ions. The optimum pH range for maximum sorption of uranium(VI) and thorium(IV) was found to be in the range 3.5-6.0. The above actinides were eluted with 10 cm 3 of 1.0 mol dm -3 HCl and determined by using an Arsenazo III spectrophotometric procedure. The calibration graph was rectilinear over the uranium(VI) concentration in the range 2-100 μg dm -3 with a relative standard deviation of 2.15% (for 25 μg of uranium(VI) present in 1.0 dm 3 of sample). The validation of the developed preconcentration procedure was carried out by analyzing marine sediment (MESS-3, NRC, Canada) and soil (IAEA soil-7, Austria) reference materials. The developed preconcentration method enables a simple instruments like a spectrophotometer gave comparable values of uranium(VI) to that of standard inductively coupled plasma-mass spectrometric values during the analysis of real soil and sediment samples. (orig.)

  10. Catechol functionalized aminopropyl silica gel: synthesis, characterization and preconcentrative separation of uranium(VI) from thorium(IV)

    Energy Technology Data Exchange (ETDEWEB)

    Metilda, P.; Mary Gladis, J.; Prasada Rao, T.P. [Regional Research Lab. (CSIR), Trivandrum (India)

    2005-07-01

    A novel solid phase extractant is prepared by chemically immobilizing catechol with diazotized aminopropyl silica gel. The resulting catechol functionalized silica gel (CASG) was characterized by FTIR, and microanalysis and was used for selective enrichment of uranium(VI) from other inorganic ions. The optimum pH range for maximum sorption of uranium(VI) and thorium(IV) was found to be in the range 3.5-6.0. The above actinides were eluted with 10 cm{sup 3} of 1.0 mol dm{sup -3} HCl and determined by using an Arsenazo III spectrophotometric procedure. The calibration graph was rectilinear over the uranium(VI) concentration in the range 2-100 {mu}g dm{sup -3} with a relative standard deviation of 2.15% (for 25 {mu}g of uranium(VI) present in 1.0 dm{sup 3} of sample). The validation of the developed preconcentration procedure was carried out by analyzing marine sediment (MESS-3, NRC, Canada) and soil (IAEA soil-7, Austria) reference materials. The developed preconcentration method enables a simple instruments like a spectrophotometer gave comparable values of uranium(VI) to that of standard inductively coupled plasma-mass spectrometric values during the analysis of real soil and sediment samples. (orig.)

  11. Removal of lindane from an aqueous solution by using aminopropyl silica gel-immobilized calix[6]arene.

    Science.gov (United States)

    Tor, Ali; Aydin, Mehmet Emin; Aydin, Senar; Tabakci, Mustafa; Beduk, Fatma

    2013-11-15

    An aminopropyl silica gel-immobilized calix[6]arene (C[6]APS) has been used for the removal of lindane from an aqueous solution in batch sorption technique. The C[6]APS was synthesized with p-tert-butylcalix[6]arene hexacarboxylate derivative and aminopropyl silica gel in the presence of N,N'-diisopropyl carbodiimide coupling reagent. The sorption study was carried out as functions of solution pH, contact time, initial lindane concentration, C[6]APS dosage and ionic strength of solution. The matrix effect of natural water samples on the sorption efficiency of C[6]APS was also investigated. Maximum lindane removal was obtained at a wide pH range of 2-8 and sorption equilibrium was achieved in 2h. The isotherm analysis indicated that the sorption data can be represented by both Langmuir and Freundlich isotherm models. Increasing ionic strength of the solutions increased the sorption efficiency and matrix of natural water samples had no effect on the sorption of lindane. By using multilinear regression model, regression equation was also developed to explain the effects of the experimental variables. Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Ceria nanoparticles vis-à-vis cerium nitrate as corrosion inhibitors for silica-alumina hybrid sol-gel coating

    Energy Technology Data Exchange (ETDEWEB)

    Lakshmi, R.V. [Surface Engineering Division, Council of Scientific and Industrial Research – National Aerospace Laboratories, HAL Airport Road, Kodihalli, Bengaluru 560017 (India); Aruna, S.T., E-mail: staruna194@gmail.com [Surface Engineering Division, Council of Scientific and Industrial Research – National Aerospace Laboratories, HAL Airport Road, Kodihalli, Bengaluru 560017 (India); Sampath, S. [Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bengaluru 560012 (India)

    2017-01-30

    Highlights: • Corrosion protection efficiency comparison of ceria nanoparticles and cerium nitrate. • Silica-alumina hybrid coating exhibited good barrier protection. • Detailed XPS study confirm the hybrid structure and presence of Ce species in coating. • Loss of cerium ions not prevalent in ceria doped coating unlike that of cerium nitrate. • Ceria increased the coating integrity, corrosion inhibition and barrier protection. - Abstract: The present work provides a comparative study on the corrosion protection efficiency of defect free sol-gel hybrid coating containing ceria nanoparticles and cerium nitrate ions as corrosion inhibitors. Less explored organically modified alumina-silica hybrid sol-gel coatings are synthesized from 3-glycidoxypropyltrimethoxysilane and aluminium-tri-sec-butoxide. The microemulsion derived nanoparticles and the hybrid coatings are characterized and compared with coatings containing cerium nitrate. Corrosion inhibiting capability is assessed using electrochemical impedance spectroscopy. Scanning Kelvin probe measurements are also conducted on the coatings for identifying the apparent corrosion prone regions. Detailed X-ray photoelectron spectroscopy (XPS) analysis is carried out to comprehend the bonding and corrosion protection rendered by the hybrid coatings.

  13. Examination of the concrete from an old Portuguese dam: Texture and composition of alkali-silica gel

    International Nuclear Information System (INIS)

    Fernandes, Isabel; Noronha, Fernando; Teles, Madalena

    2007-01-01

    Exudations and pop-outs were identified in the interior galleries of a large dam built in the 1960s. The samples collected were examined by a Scanning Electron Microscope. A dense material with a smooth surface and drying shrinkage cracks or a spongy texture were observed in the samples. The semi-quantitative composition was obtained by energy dispersive spectrometry (EDS) and it was concluded that this material corresponds to alkali-silica gel, composed of SiO 2 -Na 2 O-K 2 O-CaO. A viscous white product in contact with an aggregate particle in a cone sampled from a pop-out was observed through use of the scanning electron microscope and it has characteristics similar to the gel present in the exudations and cavities. Reference is made to the potential alkali reactivity of the aggregate present in the concrete. The texture and composition of the products probably resulting from an alkali-silica reaction are presented, set out in ternary diagrams, and discussed

  14. Submicrometric gratings fabrication from photosensitive organo-silica-hafnia thin films elaborated by sol-gel processing

    Energy Technology Data Exchange (ETDEWEB)

    Franc, Janyce [Universite de Lyon, F-42023 Saint-Etienne (France); CNRS, UMR 5516, Laboratoire Hubert Curien, 42023 Saint-Etienne (France); Universite de Saint-Etienne, Jean-Monnet, F-42023 Saint-Etienne (France); Barnier, Vincent, E-mail: barnier@emse.fr [Ecole Nationale Superieure des Mines, SMS-EMSE, CNRS:UMR 5146, LCG, F-42023 Saint-Etienne (France); Vocanson, Francis, E-mail: francis.vocanson@univ-st-etienne.fr [Universite de Lyon, F-42023 Saint-Etienne (France); CNRS, UMR 5516, Laboratoire Hubert Curien, 42023 Saint-Etienne (France); Universite de Saint-Etienne, Jean-Monnet, F-42023 Saint-Etienne (France); Gamet, Emilie; Lesage, Maryline [Universite de Lyon, F-42023 Saint-Etienne (France); CNRS, UMR 5516, Laboratoire Hubert Curien, 42023 Saint-Etienne (France); Universite de Saint-Etienne, Jean-Monnet, F-42023 Saint-Etienne (France); Jamon, Damien [Universite de Lyon, F-42023 Saint-Etienne (France); Laboratoire Claude Chappe, Telecom Saint-Etienne, 42000 Saint-Etienne Cedex 2 (France); Universite de Saint-Etienne, Jean-Monnet, F-42023 Saint-Etienne (France); Jourlin, Yves [Universite de Lyon, F-42023 Saint-Etienne (France); CNRS, UMR 5516, Laboratoire Hubert Curien, 42023 Saint-Etienne (France); Universite de Saint-Etienne, Jean-Monnet, F-42023 Saint-Etienne (France)

    2012-07-31

    The aim of this study is the elaboration of a high index sol-gel material in order to prepare submicrometric grating. The gratings were obtained after few seconds of UV exposure in one step using an organically modified silica-hafnia matrix. The chemical composition of thin films after UV and annealing treatments were studied using Fourier Transform Infrared Spectroscopy and X-Ray Photoelectron Spectroscopy. The study of optical properties revealed that the annealed films are transparent from 200 to 1000 nm and have a refractive index from 1.550 to 1.701 depending on the hafnium concentration. - Highlights: Black-Right-Pointing-Pointer Silica-hafnia matrix with high refractive index was prepared using sol-gel process. Black-Right-Pointing-Pointer Organic and inorganic networks formation of thin films was investigated. Black-Right-Pointing-Pointer Optical properties are influenced by annealing treatment and initial hafnium amount. Black-Right-Pointing-Pointer The use of high Si:Hf molar ratio can lead to a loss transmittance below 300 nm. Black-Right-Pointing-Pointer Submicrometric grating period can be prepared using a holographic method.

  15. Disiloxanes and Functionalized Silica Gels: One Route, Two Complementary Outcomes-Guanidinium and Pyridinium Ion-Exchangers.

    Directory of Open Access Journals (Sweden)

    Łukasz Tabisz

    Full Text Available Five novel disiloxane compounds comprising guanidinium and pyridinium moieties were obtained with high yields and purity. The verified synthetic pathways were then applied for modification of pre-functionalized silica gel, producing materials with the analogous organic side-chains. These halide-containing compounds and materials were then compared as to their ion-exchange properties: two disiloxanes proved to be effective in leaching different anions (nitrate, benzoate and ascorbate from solid to organic phase, and pyridinium-functionalized silica gels showed selectivity towards perchlorate ion, removing it from methanolic solutions with preference to other singly charged anions. The results presented demonstrate that both compounds and materials containing silicon-carbon bonds can be produced using the same methodology, but offer strikingly different application opportunities. Comparison of their properties provides additional insight into the binding mode of different anions and hints at how the transition from a flexible siloxane bridge to immobilization on solid surface influences anion-binding selectivity. Additionally, one of the siloxane dipodands was found to form a crystalline and poorly soluble nitrate salt (1.316 g/L, water, although it was miscible with a wide range of solvents as a hydrochloride. A possible explanation is given with the help of semi-empirical calculations. A simple, time- and cost-efficient automated potentiometric titration methodology was used as a viable analytical tool for studying ion-exchange processes for both compounds and materials, in addition to standard NMR, FT-IR and ESI-MS methods.

  16. Synthesis and electron paramagnetic resonance study of a nitroxide free radical covalently bonded on aminopropyl-silica gel

    International Nuclear Information System (INIS)

    Tudose, Madalina; Constantinescu, Titus; Balaban, Alexandru T.; Ionita, Petre

    2008-01-01

    A solid spin-labeled material was obtained starting from 2-chloro-3,5-dinitro-N-(4-(2,2,6,6-tetramethyl-piperidine-1-oxyl) -benzamide) and aminopropyl-silica gel. Stability tests showed that even after several months the spin-labeled material had the same properties as immediately after synthesis. EPR properties of the TEMPO-derivatized silica were studied as a function of solvent polarity and temperature. Rotational correlation times were calculated from EPR spectra and correlated with solvent characteristics and temperature. Polar solvents induce a fast motion of the spin-label, clearly seen in the EPR spectra by the apparition of the well-known TEMPO radical triplet. The solid spin-labeled (dry) sample showed a high interspin interaction, which can be disrupted not only by different (liquid) solvents, but also by absorption of different solids, like cyclodextrins, dendrimers or polyethyleneglycols. Also, changes induced by the temperature were studied in the case of toluene wet sample. From 150 to 370 K, the spectrum is changing from a slow motion spectrum type to a fast motion regime. The preparative procedures to obtain the spin-labeled silica as well as some of its parameters are described

  17. Synthesis and electron paramagnetic resonance study of a nitroxide free radical covalently bonded on aminopropyl-silica gel

    Energy Technology Data Exchange (ETDEWEB)

    Tudose, Madalina; Constantinescu, Titus [Institute of Physical Chemistry, Spl. Independentei 202, 060021 Bucharest (Romania); Balaban, Alexandru T. [Texas A and M University at Galveston, Marine Sciences Department, Galveston, TX 77551 (United States); Ionita, Petre [Institute of Physical Chemistry, Spl. Independentei 202, 060021 Bucharest (Romania)], E-mail: pionita@icf.ro

    2008-01-30

    A solid spin-labeled material was obtained starting from 2-chloro-3,5-dinitro-N-(4-(2,2,6,6-tetramethyl-piperidine-1-oxyl) -benzamide) and aminopropyl-silica gel. Stability tests showed that even after several months the spin-labeled material had the same properties as immediately after synthesis. EPR properties of the TEMPO-derivatized silica were studied as a function of solvent polarity and temperature. Rotational correlation times were calculated from EPR spectra and correlated with solvent characteristics and temperature. Polar solvents induce a fast motion of the spin-label, clearly seen in the EPR spectra by the apparition of the well-known TEMPO radical triplet. The solid spin-labeled (dry) sample showed a high interspin interaction, which can be disrupted not only by different (liquid) solvents, but also by absorption of different solids, like cyclodextrins, dendrimers or polyethyleneglycols. Also, changes induced by the temperature were studied in the case of toluene wet sample. From 150 to 370 K, the spectrum is changing from a slow motion spectrum type to a fast motion regime. The preparative procedures to obtain the spin-labeled silica as well as some of its parameters are described.

  18. Fabrication of Mesoporous Silica/Alumina Hybrid Membrane Film Nanocomposites using Template Sol-Gel Synthesis of Amphiphilic Triphenylene

    Science.gov (United States)

    Lintang, H. O.; Jalani, M. A.; Yuliati, L.; Salleh, M. M.

    2017-05-01

    Herein we reported that by introducing a one-dimensional (1D) substrate with a porous structure such as anodic aluminum oxide (AAO) membrane, mesoporous silica/alumina hybrid nanocomposites were successfully fabricated by using amphiphilic triphenylene (TPC10TEG) as a template in sol-gel synthesis (TPC10TEG/silicahex). For the optical study of the nanocomposites, TPC10TEG/silicahex showed absorption peak at 264 nm due to the ordered and long-range π-π stacking of the disc-like aromatic triphenylene core. Moreover, the hexagonal arrangement of TPC10TEG/silicahex was proven based on their diffraction peaks of d 100 and d 200 at 2θ = 2.52° and 5.04° and images of transmission electron microscopy (TEM), respectively. For fabrication of mesoporous silica/alumina hybrid membrane, TPC10TEG/silicahex was drop-casted onto AAO membrane for penetration into the porous structure via gravity. X-ray diffraction (XRD) analysis on the resulted hybrid nanocomposites showed that the diffraction peaks of d 100 and d 200 of TPC10TEG/silicahex were still preserved, indicating that the hexagonal arrangements of mesoporous silica were maintained even on AAO substrate. The morphology study on the hybrid nanocomposites using TEM, scanning electron microscope (SEM) and field emission scanning electron microscope (FE-SEM) showed the successful filling of most AAO channels with the TPC10TEG/silicahex nanocomposites.

  19. Mesoporous silica based MCM-41 as solid-phase extraction sorbent combined with micro-liquid chromatography-quadrupole-mass spectrometry for the analysis of pharmaceuticals in waters.

    Science.gov (United States)

    Dahane, S; Martínez Galera, M; Marchionni, M E; Socías Viciana, M M; Derdour, A; Gil García, M D

    2016-05-15

    This paper reports the first application of the silica based mesoporous material MCM-41 as a sorbent in solid phase extraction, to pre-concentrate pharmaceuticals of very different polarity (atenolol, nadolol, pindolol, timolol, bisoprolol, metoprolol, betaxolol, ketoprofen, naproxen, ibuprofen, diclofenac, tolfenamic acid, flufenamic acid and meclofenamic acid) in surface waters. The analytes were extracted from 100mL water samples at pH 2.0 (containing 10(-3) mol/L of sodium chloride) by passing the solution through a cartridge filled with 100 mg of MCM-41. Following elution, the pharmaceuticals were determined by micro-liquid chromatography and triple quadrupole-mass spectrometry. Two selected reaction monitoring transitions were monitored per compound, the most intense one being used for quantification and the second one for confirmation. Matrix effect was found in real waters for most analytes and was overcome using the standard addition method, which compared favorably with the matrix matched calibration method. The detection limits in solvent (acetonitrile:water 10:90, v/v) ranged from 0.01 to 1.48 μg/L and in real water extracts from 0.10 to 3.85 μg/L (0.001-0.0385 μg/L in the water samples). The quantitation limits in solvent were in the range 0.02-4.93 μg/L, whereas in real water extracts were between 0.45 and 10.00 μg/L (0.0045 and 0.1000 μg/L in the water samples). When ultrapure water samples were spiked at two concentration levels of each pharmaceutical (0.1 and 0.2 μg/L) and quantified using solvent based calibration graphs, recoveries were near 100%. However, recoveries for most pharmaceuticals were comparable or better than de described above, when river water samples (spiked at the same concentration levels) were quantified by the standard addition method and slightly worse using the matrix matched calibration method. Five real samples (two rivers, one dam and two fountain water samples) were analyzed by the developed method, atenolol

  20. Development and characterization of colloidal silica-based slow-release permanganate gel (SRP-G): laboratory investigations.

    Science.gov (United States)

    Lee, Eung Seok; Gupta, Neha

    2014-08-01

    Slow-release permanganate (MnO4(-)) gel (SRP-G) is a hyper-saline KMnO4 solution that can be used for treating large, dilute, or deep plumes of chlorinated solvents in groundwater. Ideally, the SRP-G injected into aquifers will slowly gelate to form MnO4(-) gel in situ, and the gel will slowly releases MnO4(-). Objectives of this study were to develop SRP-G using colloidal silica as gelling solution, characterize its gelation and release kinetics, and delineate its dynamics in a saturated sandy media. The SRP-G exhibited a two-phase increase in viscosity: a lag phase characterized by little increase in viscosity followed by a short gelation phase. Gelation lag times of SRP-G solutions increased (from 0.5h to 13d) with decreasing KMnO4 concentrations (from 25 to 8 g L(-1)). Permanganate release from gelated SRP-G increased with increasing KMnO4 concentrations, and was characterized as asymptotic release with initial peak (0.9-2.2 mg min(-1)) followed by more attenuated release. Gelation lag times of SRP-G flowing in sands (linear velocity=2.1md(-1)) increased (1, 3, and 6h) with decreasing KMnO4 concentrations (25.0, 23.0, and 22.9 g L(-1)). Permanganate release from gelated SRP-Gs continued for up to 3d and was characterized as asymptotic release with an initial peak release (∼1.2 g min(-1)) followed by more attenuated release over 70h. Dilution of SRP-G by dispersion in porous media affects gelation and release kinetics. Increasing the silica concentration in the SRP-G may facilitate gelation and extend the duration of MnO4(-) release from emplaced SRP-G in porous media. Copyright © 2014. Published by Elsevier Ltd.

  1. A new nano-sorbent for fast and efficient removal of heavy metals from aqueous solutions based on modification of magnetic mesoporous silica nanospheres

    Science.gov (United States)

    Vojoudi, Hossein; Badiei, Alireza; Bahar, Shahriyar; Mohammadi Ziarani, Ghodsi; Faridbod, Farnoush; Ganjali, Mohammad Reza

    2017-11-01

    In the present study, a new and efficient nanosorbent for the fast removal of heavy metal ions was prepared. The proposed nanosorbent was fabricated using Fe3O4 magnetic core shelled by mesoporous silica, and cetyltrimethylammonium bromide (CTAB) as surfactant template through a sol-gel process. The magnetic nanomaterial was further modified with bis(3-triethoxysilylpropyl)tetrasulfide (MSCMNPs-S4). The final nanosphers were characterized by FT-IR, XRD, TGA, BET, SEM, TEM, DLS, VSM, EDX, and UV-Vis. The potential of the resultant mesoporous magnetite nanomaterials was investigated as a convenient and effective adsorbent for the removal of toxic heavy metal ions from aqueous solutions in a batch system. The effect of essential parameters on the removal efficiency including initial pH of sample solution, adsorbent amount, metal ion concentration, contact time and type and quantity of the eluent on the adsorption characteristics of the MSCMNPs-S4 were studied. Under the optimized conditions, the proposed nanosorbent exhibited high adsorption capacity of 303.03, 256.41 and 270.27 mg g-1 and maximum removal percentages of 98.8%, 96.4%, 95.7% for Hg(II), Pd(II) and Pb(II) ions, respectively. The mechanism of the adsorbtion was found to be in good agreement with the Langmuir isotherm model. Furthermore, the reusability investigation indicated that the MSCMNPs-S4 could be used frequently at least for five cycles without any significant loss in its performance.

  2. The use of silica gel prepared by sol-gel method and polyurethane foam as microbial carriers in the continuous degradation of phenol.

    Science.gov (United States)

    Brányik, T; Kuncová, G; Páca, J

    2000-08-01

    A mixed microbial culture was immobilized by entrapment into silica gel (SG) and entrapment/ adsorption on polyurethane foam (PU) and ceramic foam. The phenol degradation performance of the SG biocatalyst was studied in a packed-bed reactor (PBR), packed-bed reactor with ceramic foam (PBRC) and fluidized-bed reactor (FBR). In continuous experiments the maximum degradation rate of phenol (q(s)max) decreased in the order: PBRC (598 mg l(-1) h(-1)) > PBR (PU, 471 mg l(-1)h(-1)) > PBR(SG, 394 mg l(-1) h(-1)) > FBR (PU, 161 mg l(-1) h(-1)) > FBR (SG, 91 mg l(-1) h(-1)). The long-term use of the SG biocatalyst in continuous phenol degradation resulted in the formation of a 100-200 microm thick layer with a high cell density on the surface of the gel particles. The abrasion of the surface layer in the FBR contributed to the poor degradation performance of this reactor configuration. Coating the ceramic foam with a layer of cells immobilized in colloidal SiO2 enhanced the phenol degradation efficiency during the first 3 days of the PBRC operation, in comparison with untreated ceramic packing.

  3. Processing, adhesion and electrical properties of silicon steel having non-oriented grains coated with silica and alumina sol-gel

    International Nuclear Information System (INIS)

    Vasconcelos, D.C.L.; Orefice, R.L.; Vasconcelos, W.L.

    2007-01-01

    Silicon steels having non-oriented grains are usually coated with a series of inorganic or organic films to be used in electrical applications. However, the commercially available coatings have several disadvantages that include poor adhesion to the substrates, low values of electrical resistance and degradation at higher temperatures. In this work, silica and alumina sol-gel films were deposited onto silicon steel in order to evaluate the possibility of replacing the commercially available coatings by these sol-gel derived materials. Silica and alumina sol-gel coatings were prepared by dipping silicon steel samples into hydrolyzed silicon or aluminum alkoxides. Samples coated with sol-gel films were studied by scanning electron microscopy, energy dispersive spectroscopy and infrared spectroscopy. Adhesion between silicon steel and sol-gel films was measured by using several standard adhesion tests. Electrical properties were evaluated by the Franklin method. Results showed that homogeneous sol-gel films can be deposited onto silicon steel. Thicknesses of the films could be easily managed by altering the speed of deposition. The structure of the films could also be tailored by introducing additives, such as nitric acid and N,N-dimethyl formamide. Adhesion tests revealed a high level of adhesion between coatings and metal. The Franklin test showed that sol-gel films can produce coated samples with electrical resistances suitable for electrical applications. Electrical properties of the coated samples could also be manipulated by altering the structure of the sol-gel films or by changing the thickness of them

  4. Extraction of Silica from Cassava Periderm using Modified Sol-Gel ...

    African Journals Online (AJOL)

    Akorede

    6School of Chemical and Metallurgical Engineering, Faculty of Engineering and the Built ... glycol as capping agent in modified sol-gel method for ..... Effect of Organic Acid Treatment on the Properties of ... Journal of Analytical and Applied.

  5. Diffusion structural analysis study of titania films deposited by sol-gel technique on silica glass

    Czech Academy of Sciences Publication Activity Database

    Balek, V.; Mitsuhashi, T.; Bountseva, I.M.; Haneda, H.; Málek, Z.; Šubrt, Jan

    2003-01-01

    Roč. 26, 1-3 (2003), s. 185-189 ISSN 0928-0707. [International Workshop on Glasses, Ceramics, Hybrids and Nanocomposites from Gels /11./. Abano Terme, 16.09.2001-21.09.2001] Institutional research plan: CEZ:AV0Z4032918 Keywords : titania film * diffusion structural analysis * sol-gel Subject RIV: CA - Inorganic Chemistry Impact factor: 1.546, year: 2003

  6. Magnetic properties of cobalt ferrite-silica nanocomposites prepared by a sol-gel autocombustion technique

    DEFF Research Database (Denmark)

    Cannas, C.; Musinu, A.; Piccaluga, G.

    2006-01-01

    The magnetic properties of cobalt ferrite-silica nanocomposites with different concentrations (15, 30, and 50 wt %) and sizes (7, 16, and 28 nm) of ferrite particles have been studied by static magnetization measurements and Mossbauer spectroscopy. The results indicate a superparamagnetic behavio...

  7. Novos sorventes baseados em poli (metiloctilsiloxano sobre sílica para uso em extração em fase sólida New sorbents based on poly(methyloctylsiloxane immobilized on silica for use in solid-phase extraction

    Directory of Open Access Journals (Sweden)

    Sonia C. N. Queiroz

    2006-07-01

    Full Text Available This paper presents an easy and practical procedure to obtain silica-based C-8 type sorbents for use in solid-phase extraction. The materials are prepared by depositing poly(methyloctylsiloxane, PMOS, on the silica support. Two different treatments for immobilization were used: thermal treatment or gamma irradiation. Suitable recoveries were obtained after pre-concentration of dilute solutions, at the ng/L level, of a mixture of pesticides, indicating the good performance of the materials.

  8. Double-Layer Surface Modification of Polyamide Denture Base Material by Functionalized Sol-Gel Based Silica for Adhesion Improvement.

    Science.gov (United States)

    Hafezeqoran, Ali; Koodaryan, Roodabeh

    2017-09-21

    Limited surface treatments have been proposed to improve the bond strength between autopolymerizing resin and polyamide denture base materials. Still, the bond strength of autopolymerizing resins to nylon polymer is not strong enough to repair the fractured denture effectively. This study aimed to introduce a novel method to improve the adhesion of autopolymerizing resin to polyamide polymer by a double layer deposition of sol-gel silica and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (AE-APTMS). The silica sol was synthesized by acid-catalyzed hydrolysis of tetraethylorthosilicate (TEOS) as silica precursors. Polyamide specimens were dipped in TEOS-derived sol (TS group, n = 28), and exposed to ultraviolet (UV) light under O 2 flow for 30 minutes. UV-treated specimens were immersed in AE-APTMS solution and left for 24 hours at room temperature. The other specimens were either immersed in AE-APTMS solution (AP group, n = 28) or left untreated (NT group, n = 28). Surface characterization was investigated by fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM). Two autopolymerizing resins (subgroups G and T, n = 14) were bonded to the specimens, thermocycled, and then tested for shear bond strength with a universal testing machine. Data were analyzed with one-way ANOVA followed by Tukey's HSD (α = 0.05). FTIR spectra of treated surfaces confirmed the chemical modification and appearance of functional groups on the polymer. One-way ANOVA revealed significant differences in shear bond strength among the study groups. Tukey's HSD showed that TS T and TS G groups had significantly higher shear bond strength than control groups (p = 0.001 and p < 0.001, respectively). Moreover, bond strength values of AP T were statistically significant compared to controls (p = 0.017). Amino functionalized TEOS-derived silica coating is a simple and cost-effective method for improving the bond strength between the autopolymerizing resin and polyamide

  9. Comparison of Analytical and Numerical Model of Adsorber/desorber of Silica Gel-Water Adsorption Heat Pump

    Directory of Open Access Journals (Sweden)

    Katarzyna Zwarycz-Makles

    2017-03-01

    Full Text Available In the paper comparison of an analytical and a numerical model of silica gel/water adsorber/desorber was presented. Adsorber/desorber as a part of the two–bed single–stage adsorption heat pump was discussed. The adsorption heat pump under consideration consists of an evaporator, two adsorber/desorber columns and a condenser. During operation of assumed adsorption heat pump only heat and mass transfer was taken into account. The both presented mathematical models were created to describe the temperature, heat and concentration changes in the adsorber/desorber and consequently to describe the performance of the adsorption heat pump. Adsorption equilibrium was described by the Dubinin-Astachov model. Adsorption and desorption process dynamics was described by application of the linear driving force model (LDF. In the analysis temperatures of evaporation and condensation were constant.

  10. Extraction chromatography of indium (III) on silica gel impregnated with high molecular weight carboxylic acid and its analytical applications

    International Nuclear Information System (INIS)

    Majumdar, P.S.; Ray, U.S.

    1991-01-01

    Indium(III) was separated by extraction chromatography with Versatic 10 as a stationary phase on a column of silica gel from acetic acid and sodium acetate solution (pH 4.5-6.0). The optimum condition for extraction was studied based on the critical study of the relevant factors as effects of pH, flow rate on extraction and elution. Role of stripping agents on the elution was studied. The separation of indium from a number of elements was carried out. Indium(III) was separated from Alsup(III), Gasup(III), Tlsup(III), Zrsup(IV) and trivalent lanthanides which interfere under the recommended extraction condition by exploiting the differences in their stripping behaviour. (author). 7 refs., 1 tab., 1 fig

  11. Development of novel hybrid materials based on poly(2-aminophenyl disulfide)/silica gel: Preparation, characterization and electrochemical studies

    Science.gov (United States)

    Benyakhou, S.; Belmokhtar, A.; Zehhaf, A.; Benyoucef, A.

    2017-12-01

    Hydrochloric acid functionalized silica gel (SiO2) has been successfully used for the grafting of poly(2-Aminophenyl disulfide) (poly(2APhS)) moieties through in-situ polymerization in the presence of ammonium peroxodisulfate (APS) as oxidant. The organic-inorganic hybrid (poly(2APhS)/SiO2 with different amounts of SiO2: 0.5 g, 1.5 g and 2 g) were thoroughly characterized through powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and ultraviolet spectroscopy (UV) measurements. The results confirm the successful formation of the poly(2APhS)/SiO2 composite. The surface morphology of the samples was characterized by transmission electron microscopy (TEM). The obtained images show the formation of poly(2APhS) on surface of silica gel. Although the incorporation of SiO2 nanoparticles reduces the electric conductivity of the poly(2APhS), the resulting samples still keep high conductivities, ranging between 8.2 × 10-4 to 1.1 × 10-6 S cm-1. The electrochemical properties of the composite were characterized by the cyclic voltammetry. The comparison between the different samples shows that the electrochemical activity is significantly depending on the amount of added SiO2. There is a clear and good electroactivity for poly(2APhS)/SiO2 with amounts of SiO2: 0.5 g and 1.5 g, respectively, compared to that observed in materials nanocomposite with amounts of SiO2: 2.0 g. However, that effect may be explained by a decrease of polymer in surface area with increase amount of SiO2 nanoparticle.

  12. [Separation of purines, pyrimidines, pterins and flavonoids on magnolol-bonded silica gel stationary phase by high performance liquid chromatography].

    Science.gov (United States)

    Chen, Hong; Li, Laishen; Zhang, Yang; Zhou, Rendan

    2012-10-01

    A new magnolol-bonded silica gel stationary phase (MSP) was used to separate the basic drugs including four purines, eight pyrimidines, four pterins and five flavonoids as polar representative samples by high performance liquid chromatography (HPLC). To clarify the separation mechanism, a commercial ODS column was also tested under the same chromatographic conditions. The high selectivities and fast baseline separations of the above drugs were achieved by using simple mobile phases on MSP. Although there is no end-caped treatment, the peak shapes of basic drugs containing nitrogen such as purines, pyrimidines and pterins were rather symmetrical on MSP, which indicated the the magnolol as ligand with multi-sites could shield the side effect of residual silanol groups on the surface of silica gel. Although somewhat different in the separation resolution, it was found that the elution orders of some drugs were generally similar on both MSP and ODS. The hydrophobic interaction should play a significant role in the separations of the above basic drugs, which was attributed to their reversed-phase property in the nature. However, MSP could provide the additional sites for many polar solutes, which was a rational explanation for the high selectivity of MSP. For example, in the separation of purines, pyrimidines and pterins on MSP, hydrogen-bonding and dipole-dipole interactions played leading roles besides hydrophobic interaction. Some solute molecules (such as mercaptopurine, vitexicarpin) and MSP can form the strong pi-pi stacking in the separation process. All enhanced the retention and improved the separation selectivity of MSP, which facilitated the separation of the basic drugs.

  13. Determination of palladium in various samples by atomic absorption spectrometry after preconcentration with dimethylglyoxime on silica gel

    International Nuclear Information System (INIS)

    Tokalioglu, Serife; Oymak, Tuelay; Kartal, Senol

    2004-01-01

    A preconcentration method based on the adsorption of palladium-dimethylglyoxime (DMG) complex on silica gel for the determination of palladium at trace levels by atomic absorption spectrometry (AAS) has been developed. The retained palladium as Pd(DMG) 2 complex was eluted with 1 mol l -1 HCl in acetone. The effect of some analytical parameters such as pH, amount of reagent and the sample volume on the recovery of palladium was examined in synthetic solutions containing street dust matrix. The influence of some matrix ions on the recovery of palladium was investigated by using the developed method when the elements were present both individually and together. The results showed that 2500 μg ml -1 Na + , K + , Mg 2+ , Al 3+ and Fe 3+ ; 5000 μg ml -1 Ca 2+ ; 500 μg ml -1 Pb 2+ ; 125 μg ml -1 Zn 2+ ; 50 μg ml -1 Cu 2+ and 25 μg ml -1 Ni 2+ did not interfere with the palladium signal. At the optimum conditions determined experimentally, the recovery for palladium was found to be 95.3±1.2% at the 95% confidence level. The relative standard deviation and limit of detection (3s/b) of the method were found to be 1.7% and 1.2 μg l -1 , respectively. In order to determine the adsorption behaviour of silica gel, the adsorption isotherm of palladium was studied and the binding equilibrium constant and adsorption capacity were calculated to be 0.38 l mg -1 and 4.06 mg g -1 , respectively. The determination of palladium in various samples was performed by using both flame AAS and graphite furnace AAS. The proposed method was successfully applied for the determination of palladium in the street dust, anode slime, rock and catalytic converter samples

  14. Effects of ionizing radiations on the optical properties of ionic copper-activated sol-gel silica glasses

    Science.gov (United States)

    Al Helou, Nissrine; El Hamzaoui, Hicham; Capoen, Bruno; Ouerdane, Youcef; Boukenter, Aziz; Girard, Sylvain; Bouazaoui, Mohamed

    2018-01-01

    Studying the impact of radiations on doped silica glasses is essential for several technological applications. Herein, bulk silica glasses, activated with various concentrations of luminescent monovalent copper (Cu+), have been prepared using the sol-gel technique. Thereafter, these glasses were subjected to X- or γ-rays irradiation at 1 MGy(SiO2) accumulated dose. The effect of these ionizing radiations on the optical properties of these glasses, as a function of the Cu-doping content, were investigated using optical absorption and photoluminescence spectroscopies. Before any irradiation, the glass with the lowest copper concentration exhibits blue and green luminescence bands under UV excitation, suggesting that Cu+ ions occupy both cubic and tetragonal symmetry sites. However, at higher Cu-doping level, only the green emission band exists. Moreover, we showed that the hydroxyl content decreases with increasing copper doping concentration. Both X and γ radiation exposures induced visible absorption due to HC1 color centers in the highly Cu-doped glasses. In the case of the lower Cu-doped glass, the Cu+ sites with a cubic symmetry are transformed into sites with tetragonal symmetry.

  15. Trivalent chromium removal from aqueous solutions by a sol–gel synthesized silica adsorbent functionalized with sulphonic acid groups

    Energy Technology Data Exchange (ETDEWEB)

    Gomez-Gonzalez, Sergio Efrain [Departamento de Ingeniería Química, Universidad de Guadalajara, Blvd. Marcelino García Barragán # 1421, esq. Calzada Olímpica, C.P. 44430 Guadalajara, Jalisco (Mexico); Carbajal-Arizaga, Gregorio Guadalupe [Departamento de Química, CUCEI, Universidad de Guadalajara, Blvd. Marcelino García Barragán # 1421, esq. Calzada Olímpica, C.P. 44430 Guadalajara, Jalisco (Mexico); Manriquez-Gonzalez, Ricardo [Departamento de Madera, Celulosa y Papel, CUCEI, Universidad de Guadalajara, Km 15.5, carretera Guadalajara-Nogales, Las Agujas, C.P. 45020 Zapopan, Jalisco (Mexico); De la Cruz-Hernandez, Wencel [Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, Km 107 carretera Tijuana-Ensenada, C.P. 22830 Ensenada, Baja California (Mexico); Gomez-Salazar, Sergio, E-mail: sergio.gomez@cucei.udg.mx [Departamento de Ingeniería Química, Universidad de Guadalajara, Blvd. Marcelino García Barragán # 1421, esq. Calzada Olímpica, C.P. 44430 Guadalajara, Jalisco (Mexico)

    2014-11-15

    Highlights: • Corpuscular sulphonic acid-functionalized silica holds improved uptake of chromium. • Mesopores on adsorbent facilitate (CH{sub 3}COO){sub 2}Cr{sup +} ion uptake on sulphonate sites. • Formation of chromium acetate sulphonate complex proposed from XPS results. • Fixed bed chromium uptake results suggest potential industrial use. - Abstract: A high capacity hybrid silica adsorbent was synthesized via sol–gel processing with sulphonic acid groups as trivalent chromium complex ions chelators from aqueous solutions. The synthesis included co-condensation of tetraethoxysilane (TEOS) with 3-(mercaptopropyl)trimethoxysilane (MPS), and oxidation of thiol to sulphonic acid groups. Chromium uptake kinetic, batch and fixed-bed experiments were performed to assess the removal of this metal from aqueous solutions. {sup 13}C, {sup 29}Si CPMAS NMR, FTIR, XPS were used to characterize the adsorbent structure and the nature of chromium complexes on the adsorbent surface. Chromium maximum uptake was obtained at pH 3 (72.8 mg/g). Elemental analysis results showed ligand density of 1.48 mmol sulphonic groups/g. About 407 mL of Cr(III) solution (311 mg/L) were treated to breakthrough point reaching ≤0.06 mg/L at the effluent. These results comply with USEPA regulation for chromium concentration in drinking water (≤0.1 mg/L). The adsorbent shows potential to be used in chromium separations to the industrial level.

  16. Occlusion of chromophore oxides by Sol-Gel methods: Application to the synthesis of hematite-silica red pigments

    Directory of Open Access Journals (Sweden)

    Vicent, J. B.

    2000-02-01

    Full Text Available Heteromorphic pigments present the chromophore particle occluded in an encapsulating matrix which is thermally stable and insoluble in glazes. The occluded chromophore compound is also insoluble in the host matrix. In this work the mechanisms of formation of this type of pigments are analyzed and the occlusion of hematite into silica matrix is discussed. The formation of this hematite-silica red pigment follows a sintering-coarsening mechanism, and, consequently, the control of both hematite particles nucleation and their crystal growth results to be decisive to obtain a good coloring effectiveness.

    En los pigmentos heteromórficos la partícula de cromóforo es ocluida en una matriz encapsuladora estable tanto termicamente como frente a los vidriados. El compuesto cromóforo ocluido y la matriz no coloreada son insolubles. En este trabajo se analiza los diferentes mecanismos de formación de estos pigmentos heteromórficos y se estudia la oclusión de hematita en sílice mediante métodos sol-gel acuoso. El pigmento sigue un mecanismo de sinterización-crecimiento cristalino por lo que es muy importante controlar el momento de nucleación y la velocidad de crecimiento de las partículas de hematita en el seno de la matriz.

  17. Trivalent chromium removal from aqueous solutions by a sol–gel synthesized silica adsorbent functionalized with sulphonic acid groups

    International Nuclear Information System (INIS)

    Gomez-Gonzalez, Sergio Efrain; Carbajal-Arizaga, Gregorio Guadalupe; Manriquez-Gonzalez, Ricardo; De la Cruz-Hernandez, Wencel; Gomez-Salazar, Sergio

    2014-01-01

    Highlights: • Corpuscular sulphonic acid-functionalized silica holds improved uptake of chromium. • Mesopores on adsorbent facilitate (CH 3 COO) 2 Cr + ion uptake on sulphonate sites. • Formation of chromium acetate sulphonate complex proposed from XPS results. • Fixed bed chromium uptake results suggest potential industrial use. - Abstract: A high capacity hybrid silica adsorbent was synthesized via sol–gel processing with sulphonic acid groups as trivalent chromium complex ions chelators from aqueous solutions. The synthesis included co-condensation of tetraethoxysilane (TEOS) with 3-(mercaptopropyl)trimethoxysilane (MPS), and oxidation of thiol to sulphonic acid groups. Chromium uptake kinetic, batch and fixed-bed experiments were performed to assess the removal of this metal from aqueous solutions. 13 C, 29 Si CPMAS NMR, FTIR, XPS were used to characterize the adsorbent structure and the nature of chromium complexes on the adsorbent surface. Chromium maximum uptake was obtained at pH 3 (72.8 mg/g). Elemental analysis results showed ligand density of 1.48 mmol sulphonic groups/g. About 407 mL of Cr(III) solution (311 mg/L) were treated to breakthrough point reaching ≤0.06 mg/L at the effluent. These results comply with USEPA regulation for chromium concentration in drinking water (≤0.1 mg/L). The adsorbent shows potential to be used in chromium separations to the industrial level

  18. Silica-Based Sol-Gel Coating on Magnesium Alloy with Green Inhibitors

    Directory of Open Access Journals (Sweden)

    Vinod Upadhyay

    2017-06-01

    Full Text Available In this work, the performances of several natural organic inhibitors were investigated in a sol-gel system (applied on the magnesium alloy Mg AZ31B substrate. The inhibitors were quinaldic acid (QDA, betaine (BET, dopamine hydrochloride (DOP, and diazolidinyl urea (DZU. Thin, uniform, and defect-free sol-gel coatings were prepared with and without organic inhibitors, and applied on the Mg AZ31B substrate. SEM and EDX were performed to analyze the coating surface properties, the adhesion to the substrate, and the thickness. Electrochemical measurements, including electrochemical impedance spectroscopy (EIS and anodic potentiodynamic polarization scan (PDS, were performed on the coated samples to characterize the coatings’ protective properties. Also, hydrogen evolution measurement—an easy method to measure magnesium corrosion—was performed in order to characterize the efficiency of coating protection on the magnesium substrate. Moreover, scanning vibrating electrode technique (SVET measurements were performed to examine the efficiency of the coatings loaded with inhibitors in preventing and containing corrosion events in defect areas. From the testing results it was observed that the formulated sol-gel coatings provided a good barrier to the substrate, affording some protection even without the presence of inhibitors. Finally, when the inhibitors’ performances were compared, the QDA-doped sol-gel was able to contain the corrosion event at the defect.

  19. Influence of sol-gel conditions on the final structure of silica-based precursors

    Czech Academy of Sciences Publication Activity Database

    Perchacz, Magdalena; Beneš, Hynek; Kobera, Libor; Walterová, Zuzana

    2015-01-01

    Roč. 75, č. 3 (2015), s. 649-663 ISSN 0928-0707 R&D Projects: GA ČR(CZ) GA14-05146S Institutional support: RVO:61389013 Keywords : sol–gel * (3-glycidyloxypropyl) trimethoxysilane * alkoxysilane Subject RIV: CA - Inorganic Chemistry Impact factor: 1.473, year: 2015

  20. Construction and evaluation of As(V) selective electrodes based on iron oxyhydroxide embedded in silica gel membrane

    International Nuclear Information System (INIS)

    Rodriguez, J.A.; Barrado, E.; Vega, M.; Prieto, F.; Lima, J.L.F.C.

    2005-01-01

    Two As(V) selective electrodes (with and without inner reference solution) have been developed using selective membranes based on iron oxyhydroxide embedded on silica gel mixed with ultrapure graphite at a 2/98 (w/w) ratio. The active component of the membrane was synthesised by means of the sol-gel technique and characterized by X-ray and FTIR spectroscopy. This compound shows a great affinity towards As(V) ions adsorbing 408 mg g -1 . Using 1 mol l -1 phosphate buffer (at a 1/1, v/v ratio) to adjust the pH and the ionic strength to 7 and 0.5 mol l -1 , respectively, the calibration curve is linear from 1.0 x 10 -1 to 1.0 x 10 -6 mol l -1 As(V), with a practical detection limit of 4 x 10 -7 mol l -1 (0.03 mg l -1 ) and a slope close to 30 mV decade -1 . The effect of potentially interfering ions was investigated. The accuracy and precision of the procedure have been tested on arsenic-free drinking water samples spiked with known amounts of arsenic and on groundwater samples containing high levels of arsenic. Total arsenic in these samples was determined after oxidation of As(III) with iodine at pH 7. The results of total As were comparable to those generated by ET-AAS

  1. Sol-gel synthesis of iron catalysers supported on silica and titanium for selectively oxidising methane to formaldehyde

    Directory of Open Access Journals (Sweden)

    Carlos Alberto Guerrero Fajardo

    2008-01-01

    Full Text Available Iron materials supported on silica were prepared by the sol-gel method for evaluating catalytic activity in selective o-xidation of methane to formaldehyde. Four catalysts were prepared, one corresponding to the silica support (catalyst 1S, another to the titanium support (catalyst 1T and two more having 0.5% weight iron loads, one for the silica su-pport (catalyst 2FS and the last one the titanium support (catalyst 2FT. The higher BET areas were 659 and 850 m2/g for catalysts 1S and 2FS, respectively while catalysts 1T and 2FT displayed areas of 65 and 54 m2/g, respec-tively. Scanning and transmission electronic microscopy displayed an amorphous structure in the silica-supported materials while titanium-supported materials displayed dense materials having defined structure. X-ray diffraction confirmed the silica’s amorphous structure in 1S and 2FS catalysts and displayed the 1T and 2FT catalysts’ anatase structure. The programmed temperature reduction for the 1S and 2FS catalysts did not display reducible species, while displaying hydrogen consumption peaks related to Fe3O4 reduction to α-Fe via FexO route for 1T and 2FT ca-talysts. The electronic spectroscopy X-ray photo confirmed the Fe(III specie as having 710.6 e.V binding energy for both 2FS and 2FT catalysts. Catalytic activity was carried out at atmospheric pressure in a quartz reactor, reaction mixture as CH4/O2/N2 =7.5/1/4 at 400-800°C temperature range. The reaction products were analysed by gas chromatography on Hayesep R and T columns using 5Å molecular screening. The best response for selective oxida-tion of methane to formaldehyde was displayed by the 2FS catalyst with 3.4% mol methane conversion at 650°C, 11.9% mol formaldehyde selectivity and 0.0211 g HCHO/Kg catalyst yield.

  2. Silica gel-Supported Palladium Catalyst for the Acyl Sonogashira Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Hossain, Shahin; Park, Jihoon; Park, Minkyu; Jin, Myungjong [Inha Univ., Incheon (Korea, Republic of)

    2013-06-15

    We have demonstrated an efficient and eco-friendly procedure for the synthesis of ynones using silica supported thiol-palladium complex as a recyclable catalyst under copper free mild reaction conditions. The material was synthesized by post grafting of 3-mercaptopropyltrimethoxysilane on amorphous silica and subsequently Pd(II) attached onto thiol groups. This synthetic method has notable advantages because it involves easily available, less costly and produces an easily recyclable catalyst in high yields of the products. The mild reaction conditions encouraged us to further extension for the development of novel multicomponent reactions. Thus we have explained the three component synthesis of pyrazoles in one-pot fashion with good yields. Specifically, this simple procedure for the ynone synthesis and this approach to synthesize N-containing heterocycles may be valuable tool in future. The acyl Sonogashira reaction between acyl chlorides and terminal alkynes is one of the most useful method for the preparation of ynones which are important intermediates to prepare versatile pharmaceutically and biologically active heterocyclic compounds such as pyrroles, pyrazoles, furans, furanones, isoxazoles, pyrimidines, quinolines, indolizidinones.

  3. Silica gel-Supported Palladium Catalyst for the Acyl Sonogashira Reaction

    International Nuclear Information System (INIS)

    Hossain, Shahin; Park, Jihoon; Park, Minkyu; Jin, Myungjong

    2013-01-01

    We have demonstrated an efficient and eco-friendly procedure for the synthesis of ynones using silica supported thiol-palladium complex as a recyclable catalyst under copper free mild reaction conditions. The material was synthesized by post grafting of 3-mercaptopropyltrimethoxysilane on amorphous silica and subsequently Pd(II) attached onto thiol groups. This synthetic method has notable advantages because it involves easily available, less costly and produces an easily recyclable catalyst in high yields of the products. The mild reaction conditions encouraged us to further extension for the development of novel multicomponent reactions. Thus we have explained the three component synthesis of pyrazoles in one-pot fashion with good yields. Specifically, this simple procedure for the ynone synthesis and this approach to synthesize N-containing heterocycles may be valuable tool in future. The acyl Sonogashira reaction between acyl chlorides and terminal alkynes is one of the most useful method for the preparation of ynones which are important intermediates to prepare versatile pharmaceutically and biologically active heterocyclic compounds such as pyrroles, pyrazoles, furans, furanones, isoxazoles, pyrimidines, quinolines, indolizidinones

  4. Cleanup of Savannah River Plant solvent using solid sorbents

    International Nuclear Information System (INIS)

    Mailen, J.C.; Tallent, O.K.

    1985-04-01

    The degradation products produced in Purex solvent by exposure to nitric acid and radiation can be divided into two groups: those which are removed by scrubbing with sodium carbonate solutions and those which are not; these latter materials are called secondary degradation products. This study investigated the use of solid sorbents for removal of the secondary degradation products from first-cycle Savannah River Plant solvent that had been previously washed with sodium carbonate solution. Silica gel, activated charcoal, macroreticular resin, attapulgite clay and activated alumina were the sorbents investigated in preliminary testing. Activated alumina was found to be most effective for improving phase separation of the solvent from sodium carbonate solutions and for increasing the interfacial tension. The activated alumina was also the sorbent most useful for removing complexants which retain plutonium at low acidity, but it was less effective in removing anionic surfactants and ruthenium. We found that the capacity of the activated alumina was greatly improved by drying the solvent before treatment

  5. ADSORPSI ION SIANIDA DALAM LARUTAN MENGGUNAKAN ADSORBEN HIBRIDA AMINOPROPIL SILIKA GEL DARI SEKAM PADI TERIMPREGNASI ALUMINIUM (Adsorption of Cyanide Ions in Solution Using a Hybrid Adsorbent Aminopropyl Silica Gel from Rice Husks of Impregnated With

    Directory of Open Access Journals (Sweden)

    Amaria Amaria

    2012-03-01

    aminopropil silica gel from rice husk that has been impregnated with aluminum (APSG-Al and silica gel impregnated with aluminum (SG-Al of rice husk silica gel as the material for the adsorption of cyanide ions in solution. The interaction between the adsorbent with cyanide ions in solution performed in a batch system. The parameters examined in this study were the influence of medium pH, the effect of interaction time and the effect of initial concentration of cyanide ion adsorption ability of adsorbent hybrid amino silica gel impregnated with aluminum. Quantitative Analysis of cyanide ions left in the filtrate was tested by means of ion selective electrode. The effect of interaction time data were analyzed with kinetic model, the data of the influence of cyanide ion concentration was analyzed by Langmuir adsorption isotherm model and Freundlich. The results showed that the infrared spectroscopic identification results show APSG-Al adsorbent has silanol groups (Si-OH, siloxil (Si-O-Si, primary amine group, NH2. The result of XRD analysis of the price of 2θ at 65.51 indicates that the aluminum impregnated with the silica in the form of alumina Al2O3. The result of adsorption of cyanide by the hybrid silica gel impregnated with aluminum aminopropil (APSG-Al showed maximum adsorption occurred at pH 5 was 67.62%, silica gel impregnated with aluminum was 51,11%. Study the kinetics of the effect of interaction time showed that the adsorbent APSG-Al and SG-Al-Al has the adsorption rate constant k1 is 2.7, 10-3and 1.9,10-3 min-1, respectively. Adsorption equilibrium data showed that the adsorbent APSG-Al and SG-Al tend to follow the adsorption isotherm model Freundlich.

  6. Adsorption of H[Ru(III) Cl2(H2EDTA)] complex on modified silica gel surface with [3-(2-aminoethyl)aminopropyl] trimethoxysilane in ethanol solutions

    International Nuclear Information System (INIS)

    Lazarin, Angelica Machi; Sernaglia, Rosana Lazara

    1999-01-01

    Silica gel was functionalized with [3-(2-aminoethyl) aminopropyl] trimethoxysilane group (SF-AEATS) and the characterization by chemical analysis (N) and infrared spectroscopy confirmed the functionalization. The capacity of the modified silica to adsorb the complex Ru (III) EDTA from ethanolic solution was studied. The selectivity coefficients of the complex formed on the support obtained was τn), 2,07 x 10 4 L/mol and the average number of ligand bonded by one metal ion on the support (n) was ∼1. (author)

  7. Tetramethylguanidine covalently bonded onto silica gel as catalyst for the addition of nitromethane to cyclopentenone

    International Nuclear Information System (INIS)

    Oliveira, Edimar de; Torres, Jocilene D.; Silva, Carlos C.; Luz, Afranio A.M.; Bakuzis, Peter; Prado, Alexandre G.S.

    2006-01-01

    A catalyst based on silica chemically modified with tetramethylguanidine (TMG) was synthesized by the co-condensation of tetraethyl orthosilicate with a new silylant agent derived from the reaction between the TMG molecule and (3-chloropropyl)trimethoxysilane. A neutral n-dodecylamine template was used to organize the polymerization of the inorganic-organic catalyst. Thermogravimetry showed that the number of active pendant groups in the catalyst was 1.35 mmol g -1 , with a surface area of 811±75 m 2 g -1 . Infrared spectroscopy and 13 C and 29 Si nuclear magnetic resonance data are in agreement with the proposed structure. This material has been used to catalyse the addition of nitromethane to cyclopentenone. The catalytic efficiency was followed and the nitromethylcyclopentanone conversion presented a yield of 98% at 3 h of reaction. The catalyst was recovered and reused 14 times, maintaining about 98% of its catalytic efficiency. (author)

  8. Tetramethylguanidine covalently bonded onto silica gel as catalyst for the addition of nitromethane to cyclopentenone

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Edimar de; Torres, Jocilene D.; Silva, Carlos C.; Luz, Afranio A.M.; Bakuzis, Peter; Prado, Alexandre G.S. [Brasilia Univ., DF (Brazil). Inst. de Quimica]. E-mail: agspradus@gmail.com

    2006-09-15

    A catalyst based on silica chemically modified with tetramethylguanidine (TMG) was synthesized by the co-condensation of tetraethyl orthosilicate with a new silylant agent derived from the reaction between the TMG molecule and (3-chloropropyl)trimethoxysilane. A neutral n-dodecylamine template was used to organize the polymerization of the inorganic-organic catalyst. Thermogravimetry showed that the number of active pendant groups in the catalyst was 1.35 mmol g{sup -1}, with a surface area of 811{+-}75 m{sup 2} g{sup -1}. Infrared spectroscopy and {sup 13}C and {sup 29}Si nuclear magnetic resonance data are in agreement with the proposed structure. This material has been used to catalyse the addition of nitromethane to cyclopentenone. The catalytic efficiency was followed and the nitromethylcyclopentanone conversion presented a yield of 98% at 3 h of reaction. The catalyst was recovered and reused 14 times, maintaining about 98% of its catalytic efficiency. (author)

  9. Microstructure investigation on micropore formation in microporous silica materials prepared via a catalytic sol-gel process by small angle X-ray scattering.

    Science.gov (United States)

    Shimizu, Wataru; Hokka, Junsuke; Sato, Takaaki; Usami, Hisanao; Murakami, Yasushi

    2011-08-04

    The so-called sol-gel technique has been shown to be a template-free, efficient way to create functional porous silica materials having uniform micropores. This appears to be closely linked with a postulation that the formation of weakly branched polymer-like aggregates in a precursor solution is a key to the uniform micropore generation. However, how such a polymer-like structure can precisely be controlled, and further, how the generated low-fractal dimension solution structure is imprinted on the solid silica materials still remain elusive. Here we present fabrication of microporous silica from tetramethyl orthosilicate (TMOS) using a recently developed catalytic sol-gel process based on a nonionic hydroxyacetone (HA) catalyst. Small angle X-ray scattering (SAXS), nitrogen adsorption porosimetry, and transmission electron microscope (TEM) allowed us to observe the whole structural evolution, ranging from polymer-like aggregates in the precursor solution to agglomeration with heat treatment and microporous morphology of silica powders after drying and hydrolysis. Using the HA catalyst with short chain monohydric alcohols (methanol or ethanol) in the precursor solution, polymer-like aggregates having microscopic correlation length (or mesh-size) micropores with diameters 2 nm) in the solid product due to apertures between the particle-like aggregates. The data demonstrate that the extremely fine porous silica architecture comes essentially from a gaussian polymer-like nature of the silica aggregates in the precursor having the microscopic mesh-size and their successful imprint on the solid product. The result offers a general but significantly efficient route to creating precisely designed fine porous silica materials under mild condition that serve as low refractive index and efficient thermal insulation materials in their practical applications.

  10. Protic ionic liquid as additive on lipase immobilization using silica sol-gel.

    Science.gov (United States)

    de Souza, Ranyere Lucena; de Faria, Emanuelle Lima Pache; Figueiredo, Renan Tavares; Freitas, Lisiane dos Santos; Iglesias, Miguel; Mattedi, Silvana; Zanin, Gisella Maria; dos Santos, Onélia Aparecida Andreo; Coutinho, João A P; Lima, Álvaro Silva; Soares, Cleide Mara Faria

    2013-03-05

    Ionic liquids (ILs) have evolved as a new type of non-aqueous solvents for biocatalysis, mainly due to their unique and tunable physical properties. A number of recent review papers have described a variety of enzymatic reactions conducted in IL solutions, on the other hand, to improve the enzyme's activity and stability in ILs; major methods being explored include the enzyme immobilization (on solid support, sol-gel, etc.), protic ionic liquids used as an additive process. The immobilization of the lipase from Burkholderia cepacia by the sol-gel technique using protic ionic liquids (PIL) as additives to protect against inactivation of the lipase due to release of alcohol and shrinkage of the gel during the sol-gel process was investigated in this study. The influence of various factors such as the length of the alkyl chain of protic ionic liquids (monoethanolamine-based) and a concentration range between 0.5 and 3.0% (w/v) were evaluated. The resulting hydrophobic matrices and immobilized lipases were characterised with regard to specific surface area, adsorption-desorption isotherms, pore volume (V(p)) and size (d(p)) according to nitrogen adsorption and scanning electron microscopy (SEM), physico-chemical properties (thermogravimetric - TG, differential scanning calorimetry - DSC and Fourier transform infrared spectroscopy - FTIR) and the potential for ethyl ester and emulsifier production. The total activity yields (Y(a)) for matrices of immobilized lipase employing protic ionic liquids as additives always resulted in higher values compared with the sample absent the protic ionic liquids, which represents 35-fold increase in recovery of enzymatic activity using the more hydrophobic protic ionic liquids. Compared with arrays of the immobilized biocatalyst without additive, in general, the immobilized biocatalyst in the presence of protic ionic liquids showed increased values of surface area (143-245 m(2) g(-1)) and pore size (19-38 Å). Immobilization with

  11. Development of a bi-functional silica monolith for electro-osmotic pumping and DNA clean-up/extraction using gel-supported reagents in a microfluidic device.

    Science.gov (United States)

    Oakley, Jennifer A; Shaw, Kirsty J; Docker, Peter T; Dyer, Charlotte E; Greenman, John; Greenway, Gillian M; Haswell, Stephen J

    2009-06-07

    A silica monolith used to support both electro-osmotic pumping (EOP) and the extraction/elution of DNA coupled with gel-supported reagents is described. The benefits of the combined EOP extraction/elution system were illustrated by combining DNA extraction and gene amplification using the polymerase chain reaction (PCR) process. All the reagents necessary for both processes were supported within pre-loaded gels that allow the reagents to be stored at 4 degrees C for up to four weeks in the microfluidic device. When carrying out an analysis the crude sample only needed to be hydrodynamically introduced into the device which was connected to an external computer controlled power supply via platinum wire electrodes. DNA was extracted with 65% efficiency after loading lysed cells onto a silica monolith. Ethanol contained within an agarose gel matrix was then used to wash unwanted debris away from the sample by EOP (100 V cm(-1) for 5 min). The retained DNA was subsequently eluted from the monolith by water contained in a second agarose gel, again by EOP using an electric field of 100 V cm(-1) for 5 min, and transferred into the PCR reagent containing gel. The eluted DNA in solution was successfully amplified by PCR, confirming that the concept of a complete self-contained microfluidic device could be realised for DNA sample clean up and amplification, using a simple pumping and on-chip reagent storage methodology.

  12. Novos sensores quimicos preparados com silica gel modificada com o ion piridinio

    OpenAIRE

    Lilian de Lourdes Lorencetti Prado

    1995-01-01

    Resumo: A sílica gel, com área superficial específica de 500 m.g e diâmetro médio de poros de 6 nm, foi organofuncionalizada com o íon piridínio. Reagiu-se a sílica com 3-cloropropiltrimetoxisilano e piridina, usando como solvente o CCI4. A quantidade de íons cloreto disponíveis para reações de troca iônica foi de 0,36 mmol.g. O espectro na região de infravermelho da sílica modificada (daqui para frente designada como SiPyCI) confirmou a presença dos grupos funcionais na superfície da mesma, ...

  13. Remaining Sites Verification Package for the 100-F-44:4, Discovery Pipeline in Silica Gel Pit. Attachment to Waste Site Reclassification Form 2008-030

    International Nuclear Information System (INIS)

    Capron, J.M.

    2008-01-01

    The 100-F-44:4, Discovery Pipeline in Silica Gel Pit subsite is located in the 100-FR-1 Operable Unit of the Hanford Site, near the location of the former 110-F Gas Storage Tanks structure. The 100-F-44:4 subsite is a steel pipe discovered October 17, 2004, during trenching to locate the 118-F-4 Silica Gel Pit. Based on visual inspection and confirmatory investigation sampling data, the 100-F-44:4 subsite is a piece of non-hazardous electrical conduit debris. The 100-F-44:4 subsite supports unrestricted future use of shallow zone soil and is protective of groundwater and the Columbia River. No residual contamination exists within the deep zone. Therefore, no deep zone institutional controls are required

  14. Designing photobioreactors based on living cells immobilized in silica gel for carbon dioxide mitigation.

    Science.gov (United States)

    Rooke, Joanna C; Léonard, Alexandre; Meunier, Christophe F; Su, Bao-Lian

    2011-09-19

    Atmospheric carbon dioxide levels have been rising since the industrial revolution, with the most dramatic increase occurring since the end of World War II. Carbon dioxide is widely regarded as one of the major factors contributing to the greenhouse effect, which is of major concern in today's society because it leads to global warming. Photosynthesis is Nature's tool for combating elevated carbon dioxide levels. In essence, photosynthesis allows a cell to harvest solar energy and convert it into chemical energy through the assimilation of carbon dioxide and water. Therefore photosynthesis is regarded as an ideal way to harness the abundance of solar energy that reaches Earth and convert anthropologically generated carbon dioxide into useful carbohydrates, providing a much more sustainable energy source. This Minireview aims to tackle the idea of immobilizing photosynthetic unicellular organisms within inert silica frameworks, providing protection both to the fragile cells and to the external ecosystem, and to use this resultant living hybrid material in a photobioreactor. The viability and activity of various unicellular organisms are summarized alongside design issues of a photobioreactor based on living hybrid materials. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Binding of Sr from milk by solid phase extraction with cryptand C222 sorbed on silica gel, cation exchange, chelating or adsorbent resins for simplified 90Sr analysis

    International Nuclear Information System (INIS)

    Tait, David; Wiechen, Arnold; Haase, Gerhard

    1995-01-01

    Several commercially available resins have been found to bind the bicyclic polyether cryptand C222 from aqueous acetonitrile solutions. The presence of C222 on some of these resins strongly improved their affinity for Sr, so that relatively small amounts of such resins sorbed Sr from milk. The resins investigated were silica gel, polyacrylic acid crosslinked with divinylbenzene (DVB), polystyrene crosslinked with divinylbenzene (PS-DVB) and PS-DVB containing sulphonate, aminomethylphosphonate, iminodiacetate and mercapto groups. The resins for which binding of C222 resulted in the largest improvement in Sr sorption from milk were PS-DVB containing mercapto groups (Chelite S) and silica gel (Si 60). Thus, 2 ml wet volume of either Chelite S containing 133 μmol of C222, or silica gel Si-60 containing 143 μmol of C222 sorbed 90 and 48%, respectively, of the Sr from 100-ml milk samples. As the sorption of Sr from milk by these systems is relatively slow, contact times of 24-36 h are required to attain these results. The Chelite S-C222 system separates Sr effectively from Cs and Ca. Under the conditions described here some 6% of the natural 40 K in milk sorbs with Sr to the resin. Ba behaves similarly to Sr. 90 Sr/ 90 Y sorbed on the silica gel Si-60-C222 system can be measured directly and efficiently by liquid scintillation counting. If adequate specificity can be attained this system might provide a very simple method of determining 90 Sr in milk

  16. Epoxy-silica nanocomposite interphase control using task-specific ionic liquids via hydrolytic and non-hydrolytic sol-gel processes

    Czech Academy of Sciences Publication Activity Database

    Donato, Ricardo Keitel; Perchacz, Magdalena; Ponyrko, Sergii; Donato, Katarzyna Zawada; Schrekker, H. S.; Beneš, Hynek; Matějka, Libor

    2015-01-01

    Roč. 5, č. 111 (2015), s. 91330-91339 ISSN 2046-2069 R&D Projects: GA ČR(CZ) GA14-05146S; GA ČR GAP108/12/1459 Institutional support: RVO:61389013 Keywords : epoxy-silica nanocomposite * sol-gel processes * ionic liquids Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.289, year: 2015

  17. Performance Evaluation of a Continuous Operation Adsorption Chiller Powered by Solar Energy Using Silica Gel and Water as the Working Pair

    OpenAIRE

    Hassan, Hassan

    2014-01-01

    In the present study, dynamic analysis and performance evaluation of a solar-powered continuous operation adsorption chiller are introduced. The adsorption chiller uses silica gel and water as the working pair. The developed mathematical model represents the heat and mass transfer within the reactor coupled with the energy balance of the collector plate and the glass cover. Moreover, a non-equilibrium adsorption kinetic model is taken into account by using the linear driving force equation. T...

  18. External and Intraparticle Diffusion of Coumarin 102 with Surfactant in the ODS-silica Gel/water System by Single Microparticle Injection and Confocal Fluorescence Microspectroscopy

    OpenAIRE

    NAKATANI, Kiyoharu; MATSUTA, Emi

    2015-01-01

    The release mechanism of coumarin 102 from a single ODS-silica gel microparticle into the water phase in the presence of Triton X-100 was investigated by confocal fluorescence microspectroscopy combined with the single microparticle injection technique. The release rate significantly depended on the Triton X-100 concentration in the water phase and was not limited by diffusion in the pores of the microparticle. The release rate constant was inversely proportional to the microparticle radius s...

  19. Determination of lead, iron and nickel in water and vegetable samples after preconcentration with aspergillus niger loaded on silica gel

    Energy Technology Data Exchange (ETDEWEB)

    Baytak, Sitki [Harran University, Arts and Science Faculty, Department of Chemistry, Sanliurfa (Turkey); Kocyigit, Abdurrahim [Harran University, Faculty of Medicine, Department of Biochemistry, Sanliurfa (Turkey); Rehber Tuerker, Ali [Gazi University, Arts and Science Faculty, Department of Chemistry, Ankara (Turkey)

    2007-12-15

    A method for the determination of Fe(III), Pb(II), and Ni(II) by flame atomic absorption spectrometry (FAAS) after preconcentrating on a column containing Aspergillus niger loaded on silica gel 60 (Biosorbent) is described. The effect of experimental parameters such as pH, flow rate of sample solution, and volume of sample solution were investigated on the recovery of the analytes. The effect of interfering ions on the recovery of the analytes has also been investigated. Recoveries of Fe(III), Pb(II), and Ni(II) were (98 {+-} 2), (98 {+-} 3), (99 {+-} 2)% at the 95% confidence level, respectively. For the analytes, 50-fold preconcentration was obtained. The analytical detection limits for Fe(III), Pb(II), and Ni(II) were 1.7, 5.2, and 1.6 ng/mL, respectively. The proposed method was applied to the determination of trace metals in various water and vegetable samples. The analytes have been determined with relative error lower than 7%. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  20. Characteristics and Laser Performance of Yb3+-Doped Silica Large Mode Area Fibers Prepared by Sol–Gel Method

    Directory of Open Access Journals (Sweden)

    Shikai Wang

    2013-12-01

    Full Text Available Large-size 0.1 Yb2O3–1.0 Al2O3–98.9 SiO2 (mol% core glass was prepared by the sol–gel method. Its optical properties were evaluated. Both large mode area double cladding fiber (LMA DCF with core diameter of 48 µm and large mode area photonic crystal fiber (LMA PCF with core diameter of 90 µm were prepared from this core glass. Transmission loss at 1200 nm is 0.41 dB/m. Refractive index fluctuation is less than 2 × 10−4. Pumped by 976 nm laser diode LD pigtailed with silica fiber (NA 0.22, the slope efficiency of 54% and “light-to-light” conversion efficiency of 51% were realized in large mode area double cladding fiber, and 81 W laser power with a slope efficiency of 70.8% was achieved in the corresponding large mode area photonic crystal fiber.

  1. Cobalt(II phthalocyanine bonded to 3-n-propylimidazole immobilized on silica gel surface: preparation and electrochemical properties

    Directory of Open Access Journals (Sweden)

    Fujiwara Sergio T.

    1999-01-01

    Full Text Available Co-Phthalocyanine complex was immobilized on 3-n-propylimidazole groups grafted on a porous SiO2 surface (specific surface area S BET = 500 m² g-1 and efficiently electrocatalyzed the oxalic acid oxidation on a carbon paste electrode surface made of this material. Intermolecular interactions of the complex species which can normally interfere in the redox process practically are not observed in the present case because of a low average surface density, delta = 4.7 x 10-13 mol cm-2 (delta = Nf/S BET, where Nf is the amount of adsorbed Co-phtalocyanine per gram of modified silica gel of the complex species material prepared. The linear response of the electrode to oxalic acid concentration, between 6.5 x 10-4 and 3.2 x 10-3 mol L-1, associated with its high chemical stability makes the covalently immobilized Co-phtalocyanine complex material very attractive in preparing a new class of chemical sensors.

  2. Optical Degradation of Colloidal Eu-Complex Embedded in Silica Glass Film Using Reprecipitation and Sol-Gel Methods.

    Science.gov (United States)

    Fukuda, Takeshi; Kurabayashi, Tomokazu; Yamaki, Tatsuki

    2016-04-01

    A reprecipitation method has been investigated for fabricating colloidal nanoparticles using Eu-complex. Herein, we investigated optical degradation characteristics of (1,10-phenanthroline)tris [4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionato]europium(III) colloidal nanoparticles, which were embedded into a silica glass film fabricated by a conventional sol-gel process. At first, we tried several types of good solvents for the reprecipitation method, and dimethyl sulfoxide (DMSO) is found to be a suitable solvent for realizing the small diameter and the high long-term stability against the ultraviolet irradiation even though the boing point of DMSO is higher than that of water used as a poor solvent. By optimizing the good solvent and the concentration of Eu-complex, the relative photoluminescence intensity of 0.96 was achieved even though the ultraviolet light was continuously irradiated for 90 min. In addition, the average diameter of 106 nm was achieved when DMSO was used as a good solvent, resulting in the high transmittance at a visible wavelength region. Therefore, we can achieve the transparent emissive thin film with a center wavelength of 612 nm, and the optical degradation was drastically reduced by forming nanoparticles.

  3. Simultaneous preconcentration of cadmium and lead in water samples with silica gel and determination by flame atomic absorption spectrometry.

    Science.gov (United States)

    Xu, Hongbo; Wu, Yun; Wang, Jian; Shang, Xuewei; Jiang, Xiaojun

    2013-12-01

    A new method that utilizes pretreated silica gel as an adsorbent has been developed for simultaneous preconcentration of trace Cd(II) and Pb(II) prior to the measurement by flame atomic absorption spectrometry. The effects of pH, the shaking time, the elution condition and the coexisting ions on the separation/preconcentration conditions of analytes were investigated. Under optimized conditions, the static adsorption capacity of Cd(II) and Pb(II) were 45.5 and 27.1mg/g, the relative standard deviations were 3.2% and 1.7% (for n = 11), and the limits of detection obtained were 4.25 and 0.60 ng/mL, respectively. The method was validated by analyzing the certified reference materials GBW 07304a (stream sediment) and successfully applied to the analysis of various treated wastewater samples with satisfactory results. Copyright © 2013 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

  4. Adsorption of Pb(II) using silica gel composite from rice husk ash modified 3-aminopropyltriethoxysilane (APTES)-activated carbon from coconut shell

    Science.gov (United States)

    Yusmaniar, Purwanto, Agung; Putri, Elfriyana Awalita; Rosyidah, Dzakiyyatur

    2017-03-01

    Silica gel modified by 3-aminopropyltriethoxysilane (APTES) was synthesized from rice husk ash combined with activated carbon from coconut shell yielded the composite adsorbent. The composite was characterized by Fourier Transform Infra Red spectroscopy (FT-IR), Electron Dispersive X-Ray (EDX), Surface Area Analyzer (SAA) and adsorption test by Atomic Absorption Spectrometry (AAS). This composite adsorbent has been used moderately for the removal of lead ions from metal solutions and compared with silica gel modified APTES and activated carbon. The adsorption experiments of Pb -ions by adsorbents were performed at different pH and contact time with the same metal solutions concentration, volume solution, and adsorbent dosage. The optimum pH for the adsorption was found to be 5.0 and the equilibrium was achieved for Pb with 20 min of contact time. Pb ions adsorption by composite silica gel modified APTES-activated carbon followed by Langmuir isotherm model with qmax value of 46.9483 mg/g that proved an adsorbent mechanism consistent to the mechanism of monolayer formation.

  5. Investigations of the uptake of transuranic radionuclides by humic and fulvic acids chemically immobilized on silica gel and their competitive release by complexing agents

    International Nuclear Information System (INIS)

    Bulman, R.A.; Szabo, G.; Clayton, R.F.; Clayton, C.R.

    1998-01-01

    The chemistry of the interactions of transuranic elements (TUs) with humic substances needs to be understood so that humate-mediated movement of transuranic radionuclides through the environment can be predicted. This paper reports the chemical immobilization on silica gel of humic and fulvic acids and evaluates the potential of these new materials for the retention of Pu and Am. In addition to the preparation of the foregoing immobilized humic substances, other low molecular weight metal-binding ligands have also been immobilized on silica gel to investigate the binding sites for transuranic elements (TUs) in humic substances. The X-ray photoelectron spectra (XPS) of Th(IV) complexed by humic acid and the immobilized humic acid are similar thus it appears that immobilization of humic acid does not generate any configurational changes in the Th(IV)-binding sites of the macromolecule. A variety of chelating agents partly mobilize these TUs sorbed on the solid phases. A batch method was used to determine the distribution coefficients (R d ) of Pu and Am between the silica gels and aqueous solutions of phosphate and citrate. The effects of the immobilized ligands, the anions and pH in the solution on sorption were assessed. Distributed coefficients (R d ) for the uptake of Pu and Am by these prepared solid phases are, in some cases, of a similar order of magnitude as those determined for soil and particles suspended in terrestrial surface waters

  6. Obtaining of Sol-Gel Ketorolac-Silica Nanoparticles: Characterization and Drug Release Kinetics

    International Nuclear Information System (INIS)

    Goerne, T.M.L.; Garcia, M.G.L.; Grada, G.R.; Perez, I.O.; Goerne, T.M.L.; Garcia, M.G.L.; Grada, G.R.; Perez, I.O.; Lemus, M.A.A.; Goerne, T.M.L.; Loez, E.G.

    2013-01-01

    Nonsteroidal anti-inflammatory drugs (NSAIDs) are among most commonly prescribed medications worldwide. NSAIDs play an important role due to their pronounced analgesic potency, anti-inflammatory effects, and lesser side effects compared to opioids. However, adverse effects including gastrointestinal and cardiovascular effects seriously complicate their prolonged use. In the present work we prepare SiO 2 -based nanoparticles with ketorolac, for controlled release proposes. The nano materials were prepared by the sol-gel technology at acidic conditions and two different water/alcoxide ratios were used. FTIR spectroscopy was performed in order to characterize the solids and drug-SiO 2 interactions. Thermal analysis and nitrogen adsorption isotherms showed thermal stability of the drug and confirmed the presence of particles with high surface area. Transmission electron micrographs of the samples showed the nano size particles (20 nm) forming aggregates. Drug release profiles were collected by means of UV-Vis spectroscopy and kinetic analysis was developed. Release data were fitted and 1:8 sample showed a sustained release over ten hours; 90% of the drug was delivered at the end of the time.

  7. Tantala-based sol-gel coating for capillary microextraction on-line coupled to high-performance liquid chromatography.

    Science.gov (United States)

    Tran, MinhPhuong; Turner, Erica B; Segro, Scott S; Fang, Li; Seyyal, Emre; Malik, Abdul

    2017-11-03

    A sol-gel organic-inorganic hybrid sorbent, consisting of chemically integrated tantalum (V) ethoxide (TaEO) and polypropylene glycol methacrylate (PPGM), was developed for capillary microextraction (CME). The sol-gel sorbent was synthesized within a fused silica capillary through hydrolytic polycondensation of TaEO and chemical incorporation of PPGM into the evolving sol-gel tantala network. A part of the organic-inorganic hybrid sol-gel network evolving in the vicinity of the capillary walls had favorable conditions to get chemically bonded to the silanol groups on the capillary surface forming a surface-bonded coating. The newly developed sol-gel sorbent was employed to isolate and enrich a variety of analytes from aqueous samples for on-line analysis by high-performance liquid chromatography (HPLC) equipped with a UV detector. CME was performed on aqueous samples containing trace concentrations of analytes representing polycyclic aromatic hydrocarbons, ketones, alcohols, amines, nucleosides, and nucleotides. This sol-gel hybrid coating provided efficient extraction with CME-HPLC detection limits ranging from 4.41pM to 28.19 pM. Due to direct chemical bonding between the sol-gel sorbent coating and the fused silica capillary inner surface, this sol-gel sorbent exhibited enhanced solvent stability. The sol-gel tantala-based sorbent also exhibited excellent pH stability over a wide pH range (pH 0-pH 14). Furthermore, it displayed great performance reproducibility in CME-HPLC providing run-to-run HPLC peak area relative standard deviation (RSD) values between 0.23% and 3.83%. The capillary-to-capillary RSD (n=3), characterizing capillary preparation method reproducibility, ranged from 0.24% to 4.11%. The results show great performance consistency and application potential for the sol-gel tantala-PPGM sorbent in various fields including biomedical, pharmaceutical, and environmental areas. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Alkali passivation mechanism of sol-gel derived TiO2-SiO2 films coated on soda-lime-silica glass substrates

    Energy Technology Data Exchange (ETDEWEB)

    Matsuda, A; Matsuno, Y; Katayama, S; Tsuno, T [Nippon Steel Glass Co. Ltd., Tokyo (Japan); Toge, N; Minami, T [University of Osaka Prefecture, Osaka (Japan). College of Engineering

    1992-09-01

    TiO2-SiO2 films prepared by the sol-gel method serves as an effective alkali passivation layer on a soda-lime-silica glass substrate and the film is superior to a sol-gel derived pure SiO2 film from the view point of weathering resistance improvement. To clarify the reason, alkali passivation mechanism of sol-gel derived TiO2-SiO2 glass films with different TiO2 contents coated on a soda-lime-silica glass substrate was studied by SIMS (secondary ion mass spectroscopy) and XPS (X-ray photoelectron spectroscopy) analyses, and compared with the results of a sol-gel derived pure SiO2 film. As a result, the following conclusions were obtained: An increase in TiO2 content in the TiO2 SiO2 film increases the sodium concentration in the film, which was induced by sodium migration from the glass substrate during the heat-treatment. Because of the presence of sodium the TiO2 -SiO2 films serve not as a barrier but as an effective getter of alkali ions and thereby effectively improve the weathering resistance Of the glass substrate. 10 refs., 6 figs.

  9. Characterization and enhanced nonlinear optical limiting response in carbon nanodots dispersed in solid-state hybrid organically modified silica gel glasses

    Science.gov (United States)

    Huang, Li; Zheng, Chan; Guo, Qiaohang; Huang, Dongdong; Wu, Xiukai; Chen, Ling

    2018-02-01

    Freely dispersed carbon nanodots (CNDs) were introduced into a 3-glycidoxy-propyltrimethoxysilane modified silicate gel glass (i.e. an organically modified silica or ORMOSIL) by a highly efficient and simple sol-gel process, which could be easily extended to prepare functional molecules/nanoparticles solid state optoelectronic devices. Scanning electron microscope imaging, Fourier transform infrared spectroscopy, pore structure measurements, ultraviolet-visible spectroscopy, and fluorescence spectroscopy were used to investigate the surface characteristics, structure, texture, and linear optical properties of the CND/SiO2 ORMOSIL gel glasses. Images and UV/Vis spectra confirmed the successful dispersion of CNDs in the ORMOSIL gel glass. The surface characteristics and pore structure of the host SiO2 matrix were markedly changed through the introduction of the CNDs. The linear optical properties of the guest CNDs were also affected by the sol-gel procedure. The nonlinear optical (NLO) properties of the CNDs were investigated by a nanosecond open-aperture Z-scan technique at 532 nm both in liquid and solid matrices. We found that the NLO response of the CNDs was considerably improved after their incorporation into the ORMOSIL gel glasses. Possible enhancement mechanisms were also explored. The nonlinear extinction coefficient gradually increased while the optical limiting (OL) threshold decreased as the CND doping level was increased. This result suggests that the NLO and OL properties of the composite gel glasses can be optimized by tuning the concentration of CNDs in the gel glass matrix. Our findings show that CND/SiO2 ORMOSIL gel glasses are promising candidates for optical limiters to protect sensitive instruments and human eyes from damage caused by high power lasers.

  10. Sol–gel derived silica/chitosan/Fe3O4 nanocomposite for direct electrochemistry and hydrogen peroxide biosensing

    International Nuclear Information System (INIS)

    Satvekar, R K; Rohiwal, S S; Tiwari, A P; Raut, A V; Tiwale, B M; Pawar, S H

    2015-01-01

    A novel strategy to fabricate hydrogen peroxide third generation biosensor has been developed from sol–gel of silica/chitosan (SC) organic–inorganic hybrid material assimilated with iron oxide magnetic nanoparticles (Fe 3 O 4 ). The large surface area of Fe 3 O 4 and porous morphology of the SC composite facilitates a high loading of horseradish peroxidase (HRP). Moreover, the entrapped enzyme preserves its conformation and biofunctionality. The fabrication of hydrogen peroxide biosensor has been carried out by drop casting of the SC/F/HRP nanocomposite on glassy carbon electrode (GCE) for study of direct electrochemistry. The x-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) confirms the phase purity and particle size of as-synthesized Fe 3 O 4 nanoparticles, respectively. The nanocomposite was characterized by UV–vis spectroscopy, fluorescence spectroscopy and Fourier transform infrared (FTIR) for the characteristic structure and conformation of enzyme. The surface topographies of the nanocomposite thin films were investigated by scanning electron microscopy (SEM). Dynamic light scattering (DLS) was used to determine the particle size distribution. The electrostatic interactions of the SC composite with Fe 3 O 4 nanoparticles were studied by the zeta potential measurement. Electrochemical impedance spectroscopy (EIS) of the SC/F/HRP/GCE electrode displays Fe 3 O 4 nanoparticles as an excellent candidate for electron transfer. The SC/F/HRP/GCE exhibited a pair of well-defined quasi reversible cyclic voltammetry peaks due to the redox couple of HRP-heme Fe (III)/Fe (II) in pH 7.0 potassium phosphate buffer. The biosensor was employed to detect H 2 O 2 with linear range of 5 μM to 40 μM and detection limit of 5 μM. The sensor displays excellent selectivity, sensitivity, good reproducibility and long term stability. (paper)

  11. Immunohistochemical characterization of nanocrystalline hydroxyapatite silica gel (NanoBone(r)) osteogenesis: a study on biopsies from human jaws.

    Science.gov (United States)

    Götz, Werner; Gerber, Thomas; Michel, Barbara; Lossdörfer, Stefan; Henkel, Kai-Olaf; Heinemann, Friedhelm

    2008-10-01

    Bone substitute biomaterials may be osteogenic, osteoconductive or osteoinductive. To test for these probable characteristics in a new nanoporous grafting material consisting of nanocrystalline hydroxyapatite embedded in a porous silica gel matrix (NanoBone(s)), applied in humans, we studied biopsies from 12 patients before dental implantation following various orofacial augmentation techniques with healing times of between 3.5 and 12 months. Sections from decalcified specimens were investigated using histology, histochemistry [periodic acid Schiff, alcian blue staining and tartrate-resistant acid phosphatase (TRAP)] and immunohistochemistry, with markers for osteogenesis, bone remodelling, resorption and vessel walls (alkaline phosphatase, bone morphogenetic protein-2, collagen type I, ED1, osteocalcin, osteopontin, runx2 and Von-Willebrand factor). Histologically, four specific stages of graft transformation into lamellar bone could be characterized. During early stages of healing, bone matrix proteins were absorbed by NanoBone(s) granules, forming a proteinaceous matrix, which was invaded by small vessels and cells. We assume that the deposition of these molecules promotes early osteogenesis in and around NanoBone(s) and supports the concomitant degradation probably by osteoclast-like cells. TRAP-positive osteoclast-like cells were localized directly on the granular surfaces. Runx2-immunoreactive pre-osteoblasts, which are probably involved in direct osteogenesis forming woven bone that is later transformed into lamellar bone, were attracted. Graft resorption and bone apposition around the graft granules appear concomitantly. We postulate that NanoBone(s) has osteoconductive and biomimetic properties and is integrated into the host's physiological bone turnover at a very early stage.

  12. Nonhydrolytic sol-gel approach to facile creation of surface-bonded zirconia organic-inorganic hybrid coatings for sample preparation. Ι. Capillary microextraction of catecholamine neurotransmitters.

    Science.gov (United States)

    Alhendal, Abdullah; Mengis, Stephanie; Matthews, Jacob; Malik, Abdul

    2016-10-14

    Nonhydrolytic sol-gel (NHSG) route was used for the creation of novel zirconia-polypropylene oxide (ZrO 2 -PPO) sol-gel hybrid sorbents in the form of surface coatings for the extraction and preconcentration of catecholamine neurotransmitters and molecules structurally related to their deaminated metabolites. In comparison to other sorbents made of inorganic transition metal oxides, the presented hybrid organic-inorganic sorbents facilitated reversible sorption properties that allowed for efficient desorption of the extracted analytes by LC-MS compatible mobile phases. The presented sol-gel hybrid sorbents effectively overcame the major drawbacks of traditional silica- or polymer-based sorbents by providing superior pH stability (pH range: 0-14), and a variety of intermolecular interactions. Nonaqueous sol-gel treatment of PPO with ZrCl 4 was employed for the derivatization of the terminal hydroxyl groups on PPO, providing zirconium trichloride-containing end groups characterized by enhanced sol-gel reactivity. NHSG ZrO 2 -PPO sorbent provided excellent microextraction performance for catecholamines, low detection limits (5.6-9.6pM), high run-to-run reproducibility (RSD 0.6-5.1%), high desorption efficiency (95.0-99.5%) and high enrichment factors (∼1480-2650) for dopamine and epinephrine, respectively, extracted from synthetic urine samples. The presented sol-gel sorbents provided effective alternative to conventional extraction media providing unique physicochemical characteristics and excellent extraction capability. Copyright © 2016 Elsevier B.V. All rights reserved.

  13. Application of a hybrid ordered mesoporous silica as sorbent for solid-phase multi-residue extraction of veterinary drugs in meat by ultra-high-performance liquid chromatography coupled to ion-trap tandem mass spectrometry.

    Science.gov (United States)

    Casado, Natalia; Morante-Zarcero, Sonia; Pérez-Quintanilla, Damián; Sierra, Isabel

    2016-08-12

    A quick, sensitive and selective analytical reversed-phase multi-residue method using ultra-high performance liquid chromatography coupled to an ion-trap mass spectrometry detector (UHPLC-IT-MS/MS) operating in both positive and negative ion mode was developed for the simultaneous determination of 23 veterinary drug residues (β-blockers, β-agonists and Non-Steroidal Anti-inflammatory Drugs (NSAIDs)) in meat samples. The sample treatment involved a liquid-solid extraction followed by a solid-phase extraction (SPE) procedure. SBA-15 type mesoporous silica was synthetized and modified with octadecylsilane, and the resulting hybrid material (denoted as SBA-15-C18) was applied and evaluated as SPE sorbent in the purification of samples. The materials were comprehensively characterized, and they showed a high surface area, high pore volume and a homogeneous distribution of the pores. Chromatographic conditions and extraction procedure were optimized, and the method was validated according to the Commission Decision 2002/657/EC. The method detection limits (MDLs) and the method quantification limits (MQLs) were determined for all the analytes in meat samples and found to range between 0.01-18.75μg/kg and 0.02-62.50μg/kg, respectively. Recoveries for 15 of the target analytes ranged from 71 to 98%. In addition, for comparative purpose SBA-15-C18 was evaluated towards commercial C18 amorphous silica. Results revealed that SBA-15-C18 was clearly more successful in the multi-residue extraction of the 23 mentioned analytes with higher recovery values. The method was successfully tested to analyze prepacked preparations of mince bovine meat. Traces of propranolol, ketoprofen and diclofenac were detected in some samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Sol-gel approach to the novel organic-inorganic hybrid composite films with ternary europium complex covalently bonded with silica matrix

    International Nuclear Information System (INIS)

    Dong Dewen; Yang Yongsheng; Jiang Bingzheng

    2006-01-01

    Novel organic-inorganic hybrid composite films with ternary lanthanide complex covalently bonded with silica matrix were prepared in situ via co-ordination of N-(3-propyltriethoxysilane)-4-carboxyphthalimide (TAT) and 1,10-phenanthroline (Phen) with europium ion (Eu 3+ ) during a sol-gel approach and characterized by the means of spectrofluorimeter, phosphorimeter and infrared spectrophotometer (FTIR). The resulting transparent films showed improved photophysical properties, i.e. increased luminescence intensity and longer luminescence lifetime, compared with the corresponding binary composite films without Phen. All the results revealed that the intense luminescence of the composite film was attributed to the efficient energy transfer from ligands, especially Phen, to chelated Eu 3+ and the reduced non-radiation through the rigid silica matrix and 'site isolation'

  15. A novel sol–gel process to facilely synthesize Ni{sub 3}Fe nanoalloy nanoparticles supported with carbon and silica

    Energy Technology Data Exchange (ETDEWEB)

    Xu, L.Q. [Institute of Materials Engineering, Nanjing National Laboratory of Microstructures, Jiangsu Provincial Laboratory for Nanotechnology and School of Physics, Nanjing University, Nanjing 210093 (China); School of Physics and Information Technology, Ningxia Teachers University, Guyuan, Ningxia 756000 (China); Chen, L.Y.; Huang, H.F.; Xie, R.; Xia, W.B.; Wei, J.; Zhong, W. [Institute of Materials Engineering, Nanjing National Laboratory of Microstructures, Jiangsu Provincial Laboratory for Nanotechnology and School of Physics, Nanjing University, Nanjing 210093 (China); Tang, S.L., E-mail: tangsl@nju.edu.cn [Institute of Materials Engineering, Nanjing National Laboratory of Microstructures, Jiangsu Provincial Laboratory for Nanotechnology and School of Physics, Nanjing University, Nanjing 210093 (China); Du, Y.W. [Institute of Materials Engineering, Nanjing National Laboratory of Microstructures, Jiangsu Provincial Laboratory for Nanotechnology and School of Physics, Nanjing University, Nanjing 210093 (China)

    2014-04-01

    Graphical abstract: The TEM and HRTEM images and the magnetization curves taken in both zero-field-cooled (ZFC) and field-cooled (FC) modes of Ni{sub 3}Fe nanoparticles calcined at 300 °C for 2 h under Ar flowing. Display Omitted - Highlights: • Ultrafine Ni{sub 3}Fe nanoalloy nanoparticles were synthesized via a modified novel sol–gel process. • The prepared Ni{sub 3}Fe nanoalloy nanoparticles have a narrow size distribution. • The Ni{sub 3}Fe nanoparticles exhibit superparamagnetic behaviors at room temperature. - Abstract: In this paper, we present a modified novel silica sol–gel process and explored the possibility, for the first time, to synthesize binary nanoalloy nanoparticles. We successfully prepared ultrafine Ni{sub 3}Fe nanoparticles supported with carbon and silica via this simple one-pot reaction without H{sub 2} reduction. X-ray diffraction (XRD) and selected area electron diffraction (SAED) investigations of the Ni{sub 3}Fe nanoparticles show that the nanoparticles have a face-centered-cubic (fcc) crystal structure. The TEM images show that grain sizes of Ni{sub 3}Fe nanoparticles have a narrow size distribution. Moreover, the grain size of the nanoparticles is not very sensitive to the elevated annealing temperature. The Ni{sub 3}Fe nanoparticles exhibit typical superparamagnetic behavior at room temperature, and the blocking temperatures (T{sub B}) are determined by the temperature-dependent magnetization (M–T curves) measurements. This novel silica sol–gel method is expected to have broad applications in synthesizing nanoalloy nanoparticles.

  16. Heavy metal adsorptivity of calcium-alginate-modified diethylenetriamine-silica gel and its application to a flow analytical system using flame atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Mori, Masanobu; Suzuki, Toshinobu; Sugita, Tsuyoshi; Nagai, Daisuke; Hirayama, Kazuo; Onozato, Makoto; Itabashi, Hideyuki

    2014-01-01

    Highlights: • Calcium-alginate-modified dien-silica gel adsorbed multivalent metal ions. • Metal ions adsorbed on CaAD were eluted using low acidic concentrations. • Flow system with CaAD-packed column enriched metal concentrations up to 50-fold. - Abstract: This study aimed to evaluate the heavy metal adsorptivity of calcium-alginate-modified diethylenetriamine-silica gel (CaAD) and incorporate this biosorbent into a flow analytical system for heavy metal ions using flame atomic absorption spectrometry (FAAS). The biosorbent was synthesized by electrostatically coating calcium alginate onto diethylenetriamine (dien)-silica gel. Copper ion adsorption tests by a batch method showed that CaAD exhibited a higher adsorption rate compared with other biosorbents despite its low maximum adsorption capacity. Next, CaAD was packed into a 1 mL microcolumn, which was connected to a flow analytical system equipped with an FAAS instrument. The flow system quantitatively adsorbed heavy metals and enriched their concentrations. This quantitative adsorption was achieved for pH 3–4 solutions containing 1.0 × 10 −6 M of heavy metal ions at a flow rate of 5.0 mL min −1 . Furthermore, the metal ions were successfully desorbed from CaAD at low nitric acid concentrations (0.05–0.15 M) than from the polyaminecarboxylic acid chelating resin (Chelex 100). Therefore, CaAD may be considered as a biosorbent that quickly adsorbs and easily desorbs analyte metal ions. In addition, the flow system enhanced the concentrations of heavy metals such as Cu 2+ , Zn 2+ , and Pb 2+ by 50-fold. This new enrichment system successfully performed the separation and determination of Cu 2+ (5.0 × 10 −8 M) and Zn 2+ (5.7 × 10 −8 M) in a river water sample and Pb 2+ (3.8 × 10 −9 M) in a ground water sample

  17. Recovery evaluation of organophosphorus pesticides from bee pollen by matrix solid-phase dispersion extraction using sorbents based on silica and titania

    International Nuclear Information System (INIS)

    Torres-Perea, C; Muñoz-Rodríguez, D; Carrera-Figueiras, C; Medina-Peralta, S; Moguel-Ordóñez, Y B

    2013-01-01

    This work focused on the evaluation of the recovery of organophosphorus pesticides from bee pollen after matrix solid phase-dispersion extraction (MSPD). Materials based on silica, titania and titania modified with polivylnylimidazole or polyestirene were used as adsorbents for the extraction of pesticides. Small amounts of fortified pollen (0.1 g, at 1 micro-g/g of pesticides), adsorbent (0.4 g) and solvent elution (1 mL de acetonitrile – ACN) were used in the extractions. For recovery evaluation, pollen extracts were analyzed by gas chromatography coupled with mass spectrometry.

  18. External and Intraparticle Diffusion of Coumarin 102 with Surfactant in the ODS-silica Gel/water System by Single Microparticle Injection and Confocal Fluorescence Microspectroscopy.

    Science.gov (United States)

    Nakatani, Kiyoharu; Matsuta, Emi

    2015-01-01

    The release mechanism of coumarin 102 from a single ODS-silica gel microparticle into the water phase in the presence of Triton X-100 was investigated by confocal fluorescence microspectroscopy combined with the single microparticle injection technique. The release rate significantly depended on the Triton X-100 concentration in the water phase and was not limited by diffusion in the pores of the microparticle. The release rate constant was inversely proportional to the microparticle radius squared, indicating that the rate-determining step is the external diffusion between the microparticle and the water phase.

  19. External and intraparticle diffusion of coumarin 102 with surfactant in the ODS-silica gel/water system by single microparticle injection and confocal fluorescence microspectroscopy

    International Nuclear Information System (INIS)

    Nakatani, Kiyoharu; Matsuta, Emi

    2015-01-01

    The release mechanism of coumarin 102 from a single ODS-silica gel microparticle into the water phase in the presence of Triton X-100 was investigated by confocal fluorescence microspectroscopy combined with the single microparticle injection technique. The release rate significantly depended on the Triton X-100 concentration in the water phase and was not limited by diffusion in the pores of the microparticle. The release rate constant was inversely proportional to the microparticle radius squared, indicating that the rate-determining step is the external diffusion between the microparticle and the water phase. (author)

  20. Two schemes for production of biosurfactant from Pseudomonas aeruginosa MR01: Applying residues from soybean oil industry and silica sol-gel immobilized cells.

    Science.gov (United States)

    Bagheri Lotfabad, Tayebe; Ebadipour, Negisa; Roostaazad, Reza; Partovi, Maryam; Bahmaei, Manochehr

    2017-04-01

    Rhamnolipids are the most common biosurfactants and P. aeruginosa strains are the most frequently studied microorganisms for the production of rhamnolipids. Eco-friendly advantages and promising applications of rhamnolipids in various industries are the major reasons for pursuing the economic production of these biosurfactants. This study shows that cultivation of P. aeruginosa MR01 in medium contained inexpensive soybean oil refinery wastes which exhibited similar levels and homologues of rhamnolipids. Mass spectrometry indicated that the Rha-C10-C10 and Rha-Rha-C10-C10 constitute the main rhamnolipids in different cultures of MR01 including one of oil carbon source analogues. Moreover, rhamnolipid mixtures extracted from different cultures showed critical micelle concentrations (CMC) in the range of ≃24 to ≃36mg/l with capability to reduce the surface tension of aqueous solution from 72 to ≃27-32mN/m. However, the sol-gel technique using tetraethyl orthosilicate (TEOS) was used as a gentler method in order to entrap the P. aeruginosa MR01 cells in mold silica gels. Immobilized cells can be utilized several times in consecutive fermentation batches as well as in flow fermentation processes. In this way, reusability of the cells may lead to a more economical fermentation process. Approximately 90% of cell viability was retained during the silica sol-gel immobilization and ≃84% of viability of immobilized cells was preserved for 365days of immobilization and storage of the cells in phosphate buffer at 4°C and 25°C. Moreover, mold gels showed good mechanical stability during the seven successive fermentation batches and the entrapped cells were able to efficiently preserve their biosurfactant-producing potential. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Effect of the size of silica nanoparticles on wettability and surface chemistry of sol–gel superhydrophobic and oleophobic nanocomposite coatings

    Energy Technology Data Exchange (ETDEWEB)

    Lakshmi, R.V., E-mail: lakshmi_rv@nal.res.in; Bera, Parthasarathi; Anandan, C.; Basu, Bharathibai J.

    2014-11-30

    Highlights: • Superhydrophobic coatings from Cab-O-Sil EH5 and M5 particles in MTEOS sol. • Particle size of Cab-O-Sil influenced its optimum concentration in coating. • FAS-13 modification improved the oleophobicity of the coating. • Coating surface exhibited porous structure with nanovoids and microscale bumps. • Coatings with Cab-O-Sil EH5 retained water repelling property for a long time. - Abstract: Superhydrophobic sol–gel nanocomposite coatings have been fabricated by incorporating silica nanoparticles with different particle sizes separately in an acid-catalyzed sol of methyltriethoxysilane (MTEOS). Water contact angle (WCA) of the coatings increased with increase in the concentration of silica nanoparticles in both the cases. The coatings became superhydrophobic at an optimum silica concentration. The water repellency was further improved by the addition of fluoroalkylsilane (FAS). The optimum silica concentration was found to depend on the size of silica nanoparticles and FAS content and the coatings exhibited WCA of about 160° and water sliding angle (WSA) of <2°. FAS addition also improved the oleophobicity of the coatings. The coatings exhibited oil-repellency with a lubricant oil contact angle of 126° and ethylene glycol contact angle of 153.3°. Surface morphology of the coatings analyzed using field emission scanning electron microscopy (FESEM) showed a rough surface with microscale bumps and nanoscale pores. XPS was used to study the surface composition of the coatings. The superhydrophobic property of the coatings was due to the synergistic effect of surface chemistry and surface microstructure and can be explained using Cassie-Baxter model.

  2. Coating of Zircaloy sheaths with silica glass using the Sol-Gel technique for protection against oxidation

    International Nuclear Information System (INIS)

    De Sanctis, O.; Pellegri, N.; Gomez, L.

    1990-01-01

    With the aim of improving corrosion resistance of Zircaloy, a few Zircaloy sheaths were covered with vitreous silica. Deposition was made by dip coating in tetraetilortosilicate (TEOS) solutions and later densification treatment at 500 degrees C. Oxidation tests were performed and compared with sheaths not covered with silica. As a result, an effective increase in the resistance to dry oxidation was found in sheaths which had been protected. The coating-Zircaloy interface was studied using XPS (scanner). (Author). 6 refs., 3 figs

  3. An optimized procedure for preconcentration, determination and on-line recovery of palladium using highly selective diphenyldiketone-monothiosemicarbazone modified silica gel

    International Nuclear Information System (INIS)

    Sharma, R.K.; Pandey, Amit; Gulati, Shikha; Adholeya, Alok

    2012-01-01

    Highlights: ► Diphenyldiketone-monothiosemicarbazone modified silica gel. ► Highly selective, efficient and reusable chelating resin. ► Solid phase extraction system for on-line separation and preconcentration of Pd(II) ions. ► Application in catalytic converter and spiked tap water samples for on-line recovery of Pd(II) ions. - Abstract: A novel, highly selective, efficient and reusable chelating resin, diphenyldiketone-monothiosemicarbazone modified silica gel, was prepared and applied for the on-line separation and preconcentration of Pd(II) ions in catalytic converter and spiked tap water samples. Several parameters like effect of pH, sample volume, flow rate, type of eluent, and influence of various ionic interferences, etc. were evaluated for effective adsorption of palladium at trace levels. The resin was found to be highly selective for Pd(II) ions in the pH range 4–5 with a very high sorption capacity of 0.73 mmol/g and preconcentration factor of 335. The present environment friendly procedure has also been applied for large-scale extraction by employing the use of newly designed reactor in which on-line separation and preconcentration of Pd can be carried out easily and efficiently in short duration of time.

  4. Silica-gel Particles Loaded with an Ionic Liquid for Separation of Zr(IV Prior to Its Determination by ICP-OES

    Directory of Open Access Journals (Sweden)

    Hadi M. Marwani

    2016-06-01

    Full Text Available A new ionic liquid loaded silica gel amine (SG-APTMS-N,N-EPANTf2 was developed, as an adsorptive material, for selective adsorption and determination of zirconium, Zr(IV, without the need for a chelating intermediate. Based on a selectivity study, the SG-APTMS-N,N-EPANTf2 phase showed a perfect selectivity towards Zr(IV at pH 4 as compared to other metallic ions, including gold [Au(III], copper [Cu(II], cobalt [Co(II], chromium [Cr(III], lead [Pb(II], selenium [Se(IV] and mercury [Hg(II] ions. The influence of pH, Zr(IV concentration, contact time and interfering ions on SG-APTMS-N,N-EPANTf2 uptake for Zr(IV was evaluated. The presence of incorporated donor atoms in newly synthesized SG-APTMS-N,N-EPANTf2 phase played a significant role in enhancing its uptake capacity of Zr(IV by 78.64% in contrast to silica gel (activated. The equilibrium and kinetic information of Zr(IV adsorption onto SG-APTMS-N,N-EPANTf2 were best expressed by Langmuir and pseudo second-order kinetic models, respectively. General co-existing cations did not interfere with the extraction and detection of Zr(IV. Finally, the analytical efficiency of the newly developed method was also confirmed by implementing it for the determination of Zr(IV in several water samples.

  5. Experimental study and thermodynamic modelling of methane clathrate hydrate dissociation conditions in silica gel porous media in the presence of methanol aqueous solution

    International Nuclear Information System (INIS)

    Hashemi, Hamed; Javanmardi, Jafar; Zarifi, Mojdeh; Eslamimanesh, Ali; Mohammadi, Amir H.

    2012-01-01

    Highlights: ► Phase equilibria of hydrates of methane in confined silica gel pores are reported. ► Dissociation data in the presences of methanol aqueous solution are also measured. ► A thermodynamic model is developed for prediction of the obtained data. ► Acceptable agreement is found between the obtained data and the predicted results. - Abstract: In this work, the phase equilibria of clathrate hydrates of methane in the presence of pure water and 0.035 mass fraction of methanol aqueous solution in confined silica gel pores with (10 and 15) nm mean diameters are measured and reported. A thermodynamic model is also developed for prediction of the obtained experimental hydrate dissociation data. The Valderrama–Patel–Teja (VPT-EoS) equation of state (EoS) accompanied with the non-density dependent (NDD) mixing rules coupled with a previously developed activity model are applied to evaluate the fugacity of the species present and the activity coefficient of water in methanol aqueous solution. Acceptable agreement between the reported data and the predicted results using the proposed model and an existing method reported in the literature demonstrates the reliability of the presented model.

  6. Fabrication and Properties of Silica Gel/Calcium Sulfate/Strontium-doped β-tricalcium Phosphate Composite Porous Scaffolds for Bone Tissue Engineering

    Directory of Open Access Journals (Sweden)

    QIN Xiao-su

    2018-03-01

    Full Text Available The calcium sulfate/strontium-doped β-tricalcium phosphate composite spherical pellets was fabricated, using the calcium sulfate/strontium-doped β-TCP as raw material, and through the stirring spray drying method, and then composite spherical pellets were combined with silica gel, porous silica gel/calcium sulfate/strontium-doped β-tricalcium phosphate scaffold was obtained by stacking aggregation method in the mould. The XRD, SEM and FT-IR, etc are employed to examine the chemical composition, composite morphology and structure characteristics, and the degradability, porosity, mechanical properties and cytotoxicity of the scaffolds materials were studied. The results reveal that the composite porous scaffolds have irregular pore structure with pore size between 0.2-1.0mm, and they have a large number of micropores on each of the composite spherical pellets, with the aperture between 50-200μm. Moreover, the porosity of the composite scaffolds is about 62%, which can meet the requirements of scaffolds for bone tissue engineering in porosity; the cytotoxicity tests show the composite scaffolds have no cytotoxic effect and it has good degradation. Therefore, it has good application prospect in bone tissue engineering of the bone defect repair of non-bearing site.

  7. Performance Evaluation of a Continuous Operation Adsorption Chiller Powered by Solar Energy Using Silica Gel and Water as the Working Pair

    Directory of Open Access Journals (Sweden)

    Hassan Zohair Hassan

    2014-10-01

    Full Text Available In the present study, dynamic analysis and performance evaluation of a solar-powered continuous operation adsorption chiller are introduced. The adsorption chiller uses silica gel and water as the working pair. The developed mathematical model represents the heat and mass transfer within the reactor coupled with the energy balance of the collector plate and the glass cover. Moreover, a non-equilibrium adsorption kinetic model is taken into account by using the linear driving force equation. The variation of solar radiation, wind speed, and atmospheric temperature along a complete cycle are considered for a more realistic simulation. Based on the case studied  and the baseline parameters, the chiller is found to acquire a coefficient of performance of 0.402. The average thermal efficiency of the solar collector is estimated to be 62.96% and the average total efficiency  approaches a value of 50.91%. Other performance parameters obtained are 363.8 W and 1.82 W/kg for the cooling capacity and the specific cooling power of the chiller, respectively. Furthermore, every 1 kg of silica gel inside the adsorption reactor produces a daily chilled water mass of 3 kg at a temperature of 10 ◦C. In addition, the cooling system harnesses 25.35% of the total available solar radiation and converts it to a cooling effect.

  8. Preparation and characterization of hydrated salts/silica composite as shape-stabilized phase change material via sol–gel process

    International Nuclear Information System (INIS)

    Wu, Yuping; Wang, Tao

    2014-01-01

    Highlights: • A mixture of hydrated salts were adopted as phase change materials. • Phase segregation of the hydrated salts was inhibited. • Subcooling was slightly mitigated. • Thermal cycling performance was greatly improved after PVP coating. - Abstract: A novel shape-stabilized phase change material composite was prepared by impregnating the mixture of hydrated salts (Na 2 SO 4 ·10H 2 O–Na 2 HPO 4 ·12H 2 O) into porous silica matrix obtained by sol–gel process and further coated with polyvinylpyrrolidone (PVP) to improve the thermal cycling performance. The chemical compatibility, morphology and phase change properties were investigated by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), hot-stage polarizing optical microscope (HS-POM) and differential scanning calorimetry (DSC). Confined in the silica matrix, phase segregation of the hydrated salts was inhibited and subcooling was slightly mitigated. No leakage was observed during the solid–liquid phase transition even when the mass ratio of hydrated salts to silica was as high as 70:30. Results showed that the melting enthalpy of the composite can reach 106.2 kJ/kg with the melting temperature at 30.13 °C and there was no significant enthalpy loss after 30 thermal cycles

  9. Improvement in ionic conductivity of self-supported P(MMA-AN-VAc) gel electrolyte by fumed silica for lithium ion batteries

    International Nuclear Information System (INIS)

    Liao Youhao; Rao Mumin; Li Weishan; Tan Chunlin; Yi Jin; Chen Lang

    2009-01-01

    Fumed silica was used as a dopant in the preparation of poly(methyl methacrylate-acrylonitrile-vinyl acetate) (P(MMA-AN-VAc)) to improve the ionic conductivity of the P(MMA-AN-VAc)-based gel polymer electrolyte (GPE). The performance of the P(MMA-AN-VAc) membrane and its GPE for lithium ion battery use were studied by XRD, SEM, TGA, LSV, CA, EIS, and charge/discharge test. It is found that the doping of fumed silica in the P(MMA-AN-VAc) changes the membrane from semi-crystal to amorphous state and the pore structure of the membrane. By the doping of 10 wt.% fumed silica in the membrane, the porosity of the membrane increases with the pore dispersed more uniformly and interconnected and having higher electrolyte uptake, resulting in the improvement in ionic conductivity of the GPE from 3.48 x 10 -3 to 5.13 x 10 -3 S cm -1 at ambient temperature. On the other hand, the thermal stability of the membrane, the electrochemical stability of the GPE, and the cyclic performance of the battery are also improved.

  10. Spectrophotometric Determination of Iron(II after Solid Phase Extraction of Its 2,2′ Bipyridine Complex on Silica Gel-Polyethylene Glycol

    Directory of Open Access Journals (Sweden)

    Nahid Pourreza

    2013-01-01

    Full Text Available A new solid phase extraction procedure was developed for preconcentration of iron(II using silica gel-polyethylene glycol (silica-PEG as an adsorbent. The method is based on retention of iron(II as 2,2′ bipyridine complex on silica-PEG. The retained complex is eluted by 1.0 mol L−1 of sulfuric acid-acetone mixture (1:2 and its absorbance is measured at 518 nm, spectrophotometrically. The effects of different parameters such as pH, concentration of the reagent, eluting reagent, sample volume, amount of adsorbent, and interfering ions were investigated. The calibration graph was linear in the range of 1–60 ng mL−1 of iron(II. The limit of detection based on 3Sb was 0.57 ng mL−1 and relative standard deviations (R.S.D for ten replicate measurements of 12 and 42 ng mL−1 of iron(II were 2.4 and 1.7%, respectively. The method was applied to the determination of of iron(II in water, multivitamin tablet, and spinach samples.

  11. Study on solid phase extraction and graphite furnace atomic absorption spectrometry for the determination of nickel, silver, cobalt, copper, cadmium and lead with MCI GEL CHP 20Y as sorbent

    International Nuclear Information System (INIS)

    Yang Guangyu; Fen Weibo; Lei Chun; Xiao Weilie; Sun Handong

    2009-01-01

    A solid phase extraction and graphite furnace atomic absorption spectrometry (GFAAS) for the determination of nickel, silver, cobalt, copper, cadmium and lead with MCI GEL CHP 20Y as sorbent was studied. Trace amounts of chromium, nickel, silver, cobalt, copper, cadmium and lead were reacted with 2-(2-quinolinil-azo)-4-methyl-1,3-dihydroxidobenzene (QAMDHB) followed by adsorption onto MCI GEL CHP 20Y solid phase extraction column, and 1.0 mol L -1 HNO 3 was used as eluent. The metal ions in 300 mL solution can be concentrated to 1.0 mL, representing an enrichment factor of 300 was achieved. The recoveries of analytes at pH 8.0 with 1.0 g of resin were greater than 95% without interference from alkaline, earth alkaline and some metal ions. When detected with graphite furnace atomic absorption spectrometry, the detection limits in the original samples were 1.4 ng L -1 for Cr(III), 1.0 ng L -1 for Ni(II), 0.85 ng L -1 for Ag(I), 1.2 ng L -1 for Co(II), 1.0 ng L -1 for Cu(II), 1.2 ng L -1 for Cd(II) and 1.3 ng L -1 for Pb(II). The validation of the procedure was performed by the analysis of the certified standard reference materials, and the presented procedure was applied to the determination of analytes in biological, water and soil samples with good results (recoveries range from 89 to 104%, and R.S.D.% lower than 3.2%. The results agreed with the standard value or reference method)

  12. Effect of Organic Solvents in Preparation of Silica-Based Chemical Gel Decontaminates for Decontamination of Nuclear Facilities

    International Nuclear Information System (INIS)

    Yoon, Suk Bon; Jung, Chong Hun; Kim, Chang Ki; Choi, Byung Seon; Lee, Kune Woo; Moon, Jei Kwon

    2011-01-01

    Decontamination of nuclear facilities is necessary to reduce the radiation field during normal operations and decommissioning of complex equipment such as stainless steel components, other iron-based steel and alloys, metal surfaces, structural materials and so on. Chemical decontamination technology in particular is a highly effective method to remove the radioactive contamination through a chemical dissolution or a redox reaction. However, this method has the serious drawback due to the generation of large amounts of the radioactive liquid wastes. Recently, a few literatures have been reported for the preparation of the chemical gel decontaminants to reduce the amount of the radioactive liquid wastes and to enhance the decontamination efficiency through increasing the contact time between the gels and the radioactive contaminants. In the preparation of the chemical gels, the control of the viscosity highly depends on the amount of a coviscosifier used among the components of the chemical gels consisted of a viscosifier, a coviscosifier, and a chemical decontaminant. In this works, a new effective method for the preparation of the chemical gel was investigated by introducing the organic solvents. The mixture solution of the coviscosifier and organic solvent was more effective in the control of the viscosity compared with that of the coviscosifier only in gels. Furthermore, the decontamination efficiency of the chemical gels measured by using the multi-channel analyzer (MCA) showed the high decontamination factor for Co-60 and Cs-137 contaminated on the surface of the stainless steel 304

  13. IR-spectroscopical investigations on the glass structure of porous and sintered compacts of colloidal silica gels

    Science.gov (United States)

    Clasen, Rolf; Hornfeck, M.; Theiss, Wolfgang

    1991-08-01

    The forming and sintering of fumed silica powders is an interesting route for the preparation of large, very pure or doped silica glasses with a precise geometry. The processing from the shaping of a porous compact to the sintering of transparent silica glass can be successfully investigated with optical spectroscopy. As only the dielectric function DF (a dielectric function is the square root of the complex refractive index) characterizes the material, the vibrational bands were calculated from reflectance measurements. In compacts of fine particles, the topology cannot be neglected. Therefore, the models describing topological effects are briefly reviewed. With these model calculations it could be proven that new bands in the compacts and the significant shifts in the reflectance spectra during sintering are mainly caused by topological effects and that changes in the glass structure play only a secondary role.

  14. Syntheses, characterization and adsorption properties for Pb{sup 2+} of silica-gel functionalized by dendrimer-like polyamidoamine and 5-sulfosalicylic acid

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xiongzhi, E-mail: 2004046@glut.edu.cn; Luo, Liangliang; Chen, Ziyan; Liang, Kailing

    2016-02-28

    Graphical abstract: SEM images of APSG, PAMAM-1.0SSASG, PAMAM-2.0SSASG, PAMAM-3.0SSASG and PAMAM-4.0SSASG. - Highlights: • Silica-gel adsorbents PAMAM-n.0SSASG (n = 1–4) with dendrimer-like polyamidoamine and 5-sulfosalicylic acid as functional groups were prepared. • The generation increase of grafted PAMAM changed the pore diameter distribution of adsorbent and adsorption/desorption property of PAMAM-4.0SSASG for Pb{sup 2+} was the best of four adsorbents. • The priority of adsorption property of PAMAM-4.0SSASG was explained by steric hindrance effect of PAMAM on adsorption/desorption, and selective adsorption of 5-sulfosalicylic acid with Pb{sup 2+}. • Pb{sup 2+} in standard reference sample and sea water sample were preconcentrated with PAMAM-4.0SSASG as adsorbent and determined by GFAAS. - Abstract: Silica-gel adsorbents PAMAM-n.0SSASG (n = 1–4) with dendrimer-like polyamidoamine (PAMAM) and 5-sulfosalicylic acid as functional groups were prepared and characterized with FTIR, SEM, TG, elemental analysis and porous structure analysis. Micro-column enrichment and measurement of Pb{sup 2+} with graphite furnace atomic absorption spectroscopy (GFAAS) was studied with PAMAM-n.0SSASG (n = 1–4) as adsorbent. It was emphasized to investigate the relationship between dynamic adsorption/desorption rates, adsorption capacities, and grafting percentage of PAMAM onto silica-gel surface. Experiments showed that the generation increase of grafted PAMAM changed the pore diameter distribution of adsorbent and obviously improved adsorption/desorption property for Pb{sup 2+}. Adsorption capacity of PAMAM-n.0SSASG (n = 1–4) was 14.04, 17.43, 20.07 and 25.05 mg g{sup −1} for Pb{sup 2+} respectively. An enrichment factor of 200 was obtained with PAMAM-4.0SSASG as adsorbent and with 2000 mL Pb{sup 2+} solution (1.0 ng mL{sup −1}). The priority of adsorption property of PAMAM-4.0SSASG was explained by steric hindrance effect of PAMAM on adsorption/desorption, and

  15. Microwave studies on the dielectric properties of Sm3+ and Sm3+/CdTe doped sol-gel silica glasses

    International Nuclear Information System (INIS)

    Mathew, Siby; Rejikumar, P.R.; Yohannan, Jaimon; Mathew, K.T.; Unnikrishnan, N.V.

    2008-01-01

    Complex permittivity and conductivity studies of Samarium and Samarium/semiconductor cadmium telluride sol-gel silica glass samples were done. We use cavity perturbation technique at S band frequencies using TE 10p Mode. Structural evolution of the matrix on annealing is discussed based on FTIR analysis/XRD power diffraction. In cavity perturbation technique dielectric parameters like complex permittivity and conductivity are determined by measuring changes in resonant frequency due to small perturbation inside the cavity produced by the introduction of the samples. The addition of the semiconductor along with the samarium was found to lower the permittivity, loss factor and conductivity. Variations of permittivity values with annealing temperature find applications in IC Technology, optic fibre communication, etc. The Sm 3+ /CdTe doped glasses can also be used in the fabrication of new and improved materials for microwave electronic circuits and in electromagnetic shielding devices

  16. Chromatographic studies on thermal and radiolytic degradation of n-dodecane-HNO3 two components system and its purification employing silica gel treatment

    International Nuclear Information System (INIS)

    Kadam, Prashant; Kaushik, C.P.; Ozarde, P.D.; Bindu, M.; Tripathi, S.C.; Jambunathan, U.; Pandit, G.G.

    2005-01-01

    This paper describes the studies carried out to examine the extent of degradation of n-dodecane at elevated temperature for different time periods and the effect of gamma radiolysis at different absorbed dose, in n-dodecane- nitric acid two components system. The studies also involved the identification of the degradation products formed during above process using GC-MS. A large number of degradation products were observed. Formation of degradation products increases with absorbed dose and time of heating. Further purification of degraded dodecane was carried out with silica gel crystals as an adsorbent. Treated dodecane samples were subjected to GC/GC-MS analysis, to confirm the extent of removal degradation products. (author)

  17. Extraction of lanthanides ions (III) from aqueous solution by sodium salt of the N(4-amino-benzoate)-propyl-silica gel

    International Nuclear Information System (INIS)

    Retamero, R.C.

    1991-01-01

    The silica gel 60 of specific superficial area 486 m 2 .g -1 was modified chemically with the ligand 4-amino benzoate of sodium in water-ethanol environment (l:L). The adsorptions of metallic ions were from water solutions at approximately 2 x 10 -3 M of chloride of Pr(III), Nd(III), Eu(III) and Ho(III). In these experiments we could see that the system gets the equilibrium of adsorption rapidly and that the pH of the environment has a great influence on the process of adsorption, being that the number of metal mols adsorpted in the matrix varied between 10,00 and 17,00 x 10 -5 mols. g -1 with a pH of approximately 5 for all the lanthanides, where the adsorption curves reach equilibrium. (author)

  18. Synthesis of xanthate functionalized silica gel and its application for the preconcentration and separation of uranium(VI) from inorganic components

    International Nuclear Information System (INIS)

    Gopi Krishna, P.; Naidu, G.R.K.; Rao, K.S.

    2005-01-01

    A new chelating solid extractant prepared by the chemical immobilization of xanthate on silica gel was characterized by Fourier transform infra red spectrometry (FTIR), thermogravimetric analysis (TGA) and microanalysis and used for the preconcentration and separation of uranyl ion prior to its determination by Arsenazo-III. The effect of pH, weight of the solid extractant, volume of the aqueous phase and the interference of neutral electrolytes, cations and anions on the determination of uranium, have been studied in detail to optimize the conditions for trace determination of uranium(VI). The accuracy of the developed procedure was tested by analyzing marine sediment (MESS-3) and soil (IAEA-SOIL-7) reference materials. The results obtained on analysis of soil and sediment samples are comparable to standard ICP-MS values. (author)

  19. Contribution to the study of the structure and properties of silica gel (1962); Contribution a l'etude de la structure et des proprietes des gels de silice (1962)

    Energy Technology Data Exchange (ETDEWEB)

    Fraissard, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-04-15

    The study of the texture of two types of silica gels, xerogels and aerogels, shows that the latter evolve differently on heating. By I.R. spectrography it has been possible to establish that this is due to the existence, in these solids, of a microstructure undetectable by X-rays and which depends on the preparation conditions initially. By using both chemical (thermogravimetry, hydrolysis of diborane) and physical (I.R. spectrography and wide-band N.M.R.) methods we have been able to determine the state of the water of constitution of these gels (water molecules and hydroxyls) and to show that the density, the distribution and the mobility of the protons of this water are very different. For example, the relaxation time T{sub 1} of the protons of a xerogel is about 1 second whilst that of the protons in an aerogel is of the order of a microsecond. Finally, it has been possible by using high resolution N.M.R. to propose a mechanism for the adsorption of formic acid on two types of gel thereby explaining, with the help of previous results, the differences in specificity of these two solids in the decomposition reaction of this acid. (author) [French] L'etude de la texture de deux types de gels de silice, les xerogels et les aerogels, montre que ceux-ci evoluent differemment en fonction de la temperature. La spectrographie I.R a permis de preciser que ceci est du a l'existence, dans ces solides, d'une microstructure indecelable aux rayons X, et fonction des conditions initiales de preparation. Par des methodes chimiques (thermogravimetrie, hydrolyse du diborane) et physiques (spectrographie I.R et R.M.N. large bande), nous avons pu determiner l'etat de l'eau de constitution de ces gels (molecules d'eau et hydroxyles) et montrer que la densite, la repartition et la mobilite des protons de cette eau sont tres differentes. Ainsi le temps de relaxation T{sub 1} des protons d'un xerogel est de l'ordre de la seconde, celui des protons d'un aerogel de l'ordre de la

  20. Selective solid phase extraction and pre-concentration of heavy metals from seawater by physically and chemically immobilized 4-amino-3-hydroxy-2-(2-chlorobenzene)-azo-1-naphtalene sulfonic acid silica gel

    International Nuclear Information System (INIS)

    Mahmoud, M.E.; Soayed, A.A.; Hafez, O.F.

    2003-01-01

    4-Amino-3-hydroxy-2 - (2-chlorobenzene)-azo-l-naphthalene sulfonic acid (AHCANSA) was used as a chelating modifier to improve the reactivity of the silica gel surface in terms of selective binding and extraction of heavy metal ions. The surface cover-age values were found to be 0.488 and 0.473 mmol g -1 for the newly modified physically adsorbed silica gel phase (I) and chemically immobilized-AHCANSA phase (II), respectively. The modified silica gel phases (I, II) were tested for stability in different acidic buffer solutions (pH 1-6) and found to be highly resistant to hydrolysis and leaching by buffer solutions above pH 2. The application of these two phases as solid extractors for a series of mono-, di-, and tri-valent metal ions from aqueous solutions was also performed with different controlling factors such as the pH value of metal ion solutions and equilibrium shaking time. The mmol g -1 metal capacity values determined by silica gel phases (I, II) were found to confirm high affinity and selectivity characters for binding with heavy metal ions such as Cr 3+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ and Pb 2+ in a range of 0.250-0.483. The tested alkali and alkaline earth metals, Na + , K + , Mg 2+ and Ca 2+ , were found to exhibit little interaction and binding ability with the modified silica gel phases. The selectivity characters incorporated into the modified silica gel phases were further utilized and applied in solid phase extraction and pre-concentration of trace concentration levels (∼1.0 μg mL -1 and 2.00-2.50 ng mL -1 ) from real seawater samples. The percentage recovery values determined for Cr 3+ , Cu 2+ , Zn 2+ , Cd 2+ and Pb 2+ were found to be in the range of 95.2-98.1 ± 2.0-5.0 %, and the pre-concentration recovery values for the same tested heavy metal ions were found to be in the range of 92.5-97.1 ± 3.0-6.0 % for the two newly modified silica gel phases with a pre-concentration factor of 500. Refs. 25 (author)

  1. {sup 5}D{sub 3}{yields}{sup 7}F{sub J} emission of Tb doped sol-gel silica

    Energy Technology Data Exchange (ETDEWEB)

    Seed Ahmed, H.A.A.; Ntwaeaborwa, O.M.; Gusowski, M.A. [Department of Physics, University of the Free State, IB51, Box 339, Bloemfontein 9300 (South Africa); Botha, J.R. [Department of Physics, Nelson Mandela Metropolitan University, Box 77000, Port Elizabeth 6031 (South Africa); Kroon, R.E., E-mail: KroonRE@ufs.ac.za [Department of Physics, University of the Free State, IB51, Box 339, Bloemfontein 9300 (South Africa)

    2012-05-15

    Amorphous silica samples doped with 0.1 and 1 mol% of terbium (Tb) were synthesized by the sol-gel method. In addition to the green light associated with {sup 5}D{sub 4}{yields}{sup 7}F{sub J} transitions of Tb{sup 3+}, the sample containing 0.1 mol% also emitted blue light as a result of {sup 5}D{sub 3}{yields}{sup 7}F{sub J} transitions during photoluminescence (PL) measurements. As a result of concentration quenching this blue emission was not observed for the samples doped with the higher concentration (1 mol%). However the blue {sup 5}D{sub 3} {yields}{sup 7}F{sub J} emission was observed in the 1 mol% doped samples during cathodoluminescence (CL) measurements. Since a rough calculation indicated that the excitation rate in the CL system where the blue emission is observed may be similar to a laser PL system under conditions where the blue emission is not observed, the difference is attributed to the nature of the excitation sources. It is suggested that during the CL excitation incident electrons can reduce non-luminescent Tb{sup 4+} ions in the silica, substituting for Si{sup 4+} ions, to the excited (Tb{sup 3+}) Low-Asterisk state and that these are responsible for the blue emission, which does not occur during PL excitation.

  2. Photocatalytic removal of Congo red dye using MCM-48/Ni2O3 composite synthesized based on silica gel extracted from rice husk ash; fabrication and application.

    Science.gov (United States)

    Shaban, Mohamed; Abukhadra, Mostafa R; Hamd, Ahmed; Amin, Ragab R; Abdel Khalek, Ahmed

    2017-12-15

    MCM-48 mesoporous silica was successfully synthesized from silica gel extracted from rice husk ash and loaded by nickel oxide (Ni 2 O 3 ). The resulted composite was characterized using X-ray diffraction, scanning electron microscope, and UV-vis spectrophotometer. The role of MCM-48 as catalyst support in enhancing the photocatalytic properties of nickel oxide was evaluated through the photocatalytic degradation of Congo red dye under visible light source. MCM-48 as catalyst support for Ni 2 O 3 shows considerable enhancement in the adsorption capacity by 17% and 29% higher than the adsorption capacity of MCM-48 and Ni 2 O 3 , respectively. Additionally, the photocatalytic degradation percentage increased by about 64% relative to the degradation percentage using Ni 2 O 3 as a single component. The adsorption mechanism of MCM-48/Ni 2 O 3 is chemisorption process of multilayer form. The using of MCM-48 as catalyst support for Ni 2 O 3 enhanced the adsorption capacity and the photocatalytic degradation through increasing the surface area and prevents the nickel oxide particles from agglomeration. This was done through fixing nickel oxide particles throughout the porous structure which providing more exposed active adsorption sites and active photocatalyst sites for the incident photons. Based on the obtained results, supporting of nickel oxide particles onto MCM-48 are promising active centers for the degradation of Congo red dye molecules. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Sol-gel electrospinning preparation of hybrid carbon silica nanofibers for extracting organophosphorus pesticides prior to analyzing them by gas chromatography-ion mobility spectrometry.

    Science.gov (United States)

    Jafari, Mohammad T; Saraji, Mohammad; Kermani, Mansoure

    2018-07-13

    Carbon-silica hybrid nanofibers as high performance coatings for solid-phase microextraction fibers were used for analyzing some pesticides by using gas chromatography-corona discharge ion mobility spectrometry. To that end, the fibers were prepared by carbonizing sol-gel based on electrospun polyacrylonitrile and tetraethyl orthosilicate nanofibers as carbon and silica precursors, respectively. Different parameters affecting the electrospinning and the extraction processes including spinning distance, voltage, feeding rate, stirring rate, salt concentration, temperature and extraction time were optimized by response surface methodology. The method involved deionized water samples spiked with pesticides at different concentration levels. The calibration curves were linear in the ranges of 0.1-20 and 0.05-20 μg L -1 with determination coefficients (R 2 ) of 0.9976 and 0.9928 for malathion and chlorpyrifos, respectively. The limits of detection of 0.032 and 0.019 μg L -1 and the limits of quantification of 0.1 and 0.05 μg L -1 were found for malathion and chlorpyrifos, respectively. Acceptable reproducibility values were obtained with relative standard deviations (RSD, n = 3) lower than 6 and 15%, for intra-day and inter-day precision, respectively. Finally, the relative recoveries of the proposed method were calculated in the range of 80-111% for real samples. Copyright © 2018 Elsevier B.V. All rights reserved.

  4. Recent applications of ionic liquids in the sol-gel process for polymer-silica nanocomposites with ionic interfaces

    Czech Academy of Sciences Publication Activity Database

    Donato, K. Z.; Matějka, Libor; Mauler, R. S.; Donato, R. K.

    2017-01-01

    Roč. 1, č. 1 (2017), s. 1-25, č. článku 5. E-ISSN 2504-5377 Institutional support: RVO:61389013 Keywords : ionic liquids * sol-gel * ionic interfaces Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science

  5. Composites with Photosensitive 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin Entrapped into Silica Gels

    Czech Academy of Sciences Publication Activity Database

    Rychtáriková, Renata; Šabata, Stanislav; Hetflejš, Jiří; Kuncová, Gabriela

    2012-01-01

    Roč. 61, č. 1 (2012), s. 119-125 ISSN 0928-0707 R&D Projects: GA MŠk ME 892 Institutional research plan: CEZ:AV0Z40720504 Keywords : sol-gel * photosensitizer * immobilization Subject RIV: CC - Organic Chemistry Impact factor: 1.660, year: 2012

  6. Bifunctional ferromagnetic Eu-Gd-Bi-codoped hybrid organo-silica red emitting phosphors synthesized by a modified Pechini sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Abo-Naf, S.M., E-mail: sm.abo-naf@nrc.sci.eg [Glass Research Department, National Research Centre (NRC), El-Buhouth Str., Dokki, 12622 Cairo (Egypt); Abdel-Hameed, S.A.M.; Marzouk, M.A. [Glass Research Department, National Research Centre (NRC), El-Buhouth Str., Dokki, 12622 Cairo (Egypt); Hamdy, Y.M. [Spectroscopy Department, National Research Centre (NRC), El-Buhouth Str., Dokki, 12622 Cairo (Egypt)

    2017-06-15

    Red phosphor, composed of Eu-Gd-Bi-codoped hybrid organo-silica glass, has been synthesized via a modified Pechini sol-gel process. The synthesized hybrid glass was analyzed with powder X-ray diffraction (XRD), differential thermal analysis coupled with thermogravimetry (DTA-TG) and Fourier transform infrared (FTIR) spectroscopy. XRD and DTA-TG confirmed its amorphous structure up to 1000 °C. Magnetic behavior of the produced phosphor was investigated using vibrating specimen magnetometer (VSM) and the obtained results revealed its unsaturated ferromagnetic behavior. Photoluminescence (PL) properties of the obtained phosphor have been investigated under near-UV excitation at 395 nm. The influence of calcination temperature on the PL intensity and its decay behavior as well as on the ferromagnetic characteristics has been studied to determine the optimal reaction temperature of the phosphor. The PL emission spectra show the characteristic emission bands of Eu{sup 3+} ions in the wavelength range from 580 to 700 nm. These emission spectra have been dominated by the electric dipole {sup 5}D{sub 0}→{sup 7}F{sub 2} transition of the Eu{sup 3+} peaked at 610–620 nm producing the red light emission of the phosphors. It was found that the phosphor performance, expressed by its PL intensity and life time, could be significantly improved by increasing of the heat treatment temperature up to 900 °C. Also, calcination at 900 °C for 6 h greatly increased both of the magnetization and retentivity, while decreased the coercivity value. The organic phenomenon of metal citrate-ethylene glycol chelation and its degradation by calcination were well followed by FTIR spectroscopy. The obtained results are promising and could afford a basis for designing of efficient red phosphors for displays, lighting and bifunctional biosensors for biomedical applications. - Highlights: • Eu-Gd-Bi-codoped hybrid organo-silica phosphor was synthesized by sol-gel method. • Inorganic Eu-Gd-Bi-silica

  7. Effects of crown ethers in nanocomposite silica-gel electrolytes on the performance of quasi-solid-state dye-sensitized solar cells

    KAUST Repository

    Huang, Kuan-Chieh

    2010-04-01

    The effects of crown ethers (CEs) on the performance of quasi-solid-state dye-sensitized solar cells (DSSCs) have been investigated. Nanocomposite silica was used to form gel matrices in the electrolytes, which contained lithium iodide (LiI) and iodine (I2) in 3-methoxypropionitrile (MPN) solvent. Three types of CEs, 12-crown-4 (12-C-4), 15-crown-5 (15-C-5), and 18-crown-6 (18-C-6) were used as additives to the gel electrolytes. DSSCs containing CEs showed enhancements in solar-to-electricity conversion efficiencies (η), with reference to the one without them. The crown ether, 15-C-5, with a size of cavity matching with the size of Li+ in the electrolyte rendered for its DSSC the best performance with an η of 3.60%, under 100 mW/cm2 illumination, as compared to 2.44% for the cell without any CE. Enhancements in the photovoltaic parameters of the cells with the CEs were explained based on the binding abilities of the CEs with lithium ions (Li+) in the electrolyte. Linear sweep voltammetry (LSV) measurements and electrochemical impedance spectra were used to substantiate the explanations. © 2009 Elsevier B.V. All rights reserved.

  8. Improved Mobility Control for Carbon Dioxide (CO{sub 2}) Enhanced Oil Recovery Using Silica-Polymer-Initiator (SPI) Gels

    Energy Technology Data Exchange (ETDEWEB)

    Oglesby, Kenneth

    2014-01-31

    SPI gels are multi-component silicate based gels for improving (areal and vertical) conformance in oilfield enhanced recovery operations, including water-floods and carbon dioxide (CO{sub 2}) floods, as well as other applications. SPI mixtures are like-water when pumped, but form light up to very thick, paste-like gels in contact with CO{sub 2}. When formed they are 3 to 10 times stronger than any gelled polyacrylamide gel now available, however, they are not as strong as cement or epoxy, allowing them to be washed / jetted out of the wellbore without drilling. This DOE funded project allowed 8 SPI field treatments to be performed in 6 wells (5 injection wells and 1 production well) in 2 different fields with different operators, in 2 different basins (Gulf Coast and Permian) and in 2 different rock types (sandstone and dolomite). Field A was in a central Mississippi sandstone that injected CO{sub 2} as an immiscible process. Field B was in the west Texas San Andres dolomite formation with a mature water-alternating-gas miscible CO{sub 2} flood. Field A treatments are now over 1 year old while Field B treatments have only 4 months data available under variable WAG conditions. Both fields had other operational events and well work occurring before/ during / after the treatments making definitive evaluation difficult. Laboratory static beaker and dynamic sand pack tests were performed with Ottawa sand and both fields’ core material, brines and crude oils to improve SPI chemistry, optimize SPI formulations, ensure SPI mix compatibility with field rocks and fluids, optimize SPI treatment field treatment volumes and methods, and ensure that strong gels set in the reservoir. Field quality control procedures were designed and utilized. Pre-treatment well (surface) injectivities ranged from 0.39 to 7.9 MMCF/psi. The SPI treatment volumes ranged from 20.7 cubic meters (m{sup 3}, 5460 gallons/ 130 bbls) to 691 m{sup 3} (182,658 gallons/ 4349 bbls). Various size and types

  9. Purification of an Immunoadjuvant Saponin Fraction from Quillaja brasiliensis Leaves by Reversed-Phase Silica Gel Chromatography.

    Science.gov (United States)

    Yendo, Anna C A; de Costa, Fernanda; Kauffmann, Carla; Fleck, Juliane D; Gosmann, Grace; Fett-Neto, Arthur G

    2017-01-01

    Saponins include a large variety of molecules that find several applications in pharmacology. The use of Quillaja saponaria saponins as immunological adjuvants in vaccines is of interest due to their capacity to stimulate both humoral and cellular responses. The congener species Q. brasiliensis has saponins with chemical similarities and adjuvant activity comparable to that of Q. saponaria fraction Quil-A ® , with additional advantages of showing lower toxicity and reduced hemolytic activity. Here we describe in detail the methods for preparing the aqueous extract from Q. brasiliensis leaves, as well as the purification of the bioactive saponin fraction QB-90 using silica reversed-phase chromatography.

  10. Functionalisation of mesoporous silica gel with 2-[(phosphonomethyl)-amino]acetic acid functional groups. Characterisation and application

    Energy Technology Data Exchange (ETDEWEB)

    Caldarola, Dario [Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Australian Centre for Research on Separation Sciences (ACROSS), University of Tasmania, Hobart, Tasmania 7001 (Australia); Mitev, Dimitar P. [Australian Centre for Research on Separation Sciences (ACROSS), University of Tasmania, Hobart, Tasmania 7001 (Australia); Marlin, Lucile [Ecole Nationale Superieure des Ingenieurs en Arts Chimiques et Technologiquesm, Toulouse (France); Irish Separation Science Cluster, Dublin City University, Dublin (Ireland); Nesterenko, Ekaterina P. [Irish Separation Science Cluster, Dublin City University, Dublin (Ireland); Paull, Brett [Australian Centre for Research on Separation Sciences (ACROSS), University of Tasmania, Hobart, Tasmania 7001 (Australia); Onida, Barbara [Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); CR-INSTM for Materials with Controlled Porosity (Italy); Bruzzoniti, Maria Concetta; Carlo, Rosa Maria De; Sarzanini, Corrado [Analytical Chemistry Department, University of Torino, Via P. Giuria 5, 10125 Torino (Italy); Nesterenko, Pavel N., E-mail: Pavel.Nesterenko@utas.edu.au [Australian Centre for Research on Separation Sciences (ACROSS), University of Tasmania, Hobart, Tasmania 7001 (Australia)

    2014-01-01

    A new complexing adsorbent was prepared by chemical modification of mesoporous silica Kieselgel 60 (d{sub p} = 37–63 μm, average pore size 6 nm, specific surface area 425 m{sup 2} g{sup −1}) with 3-glycidoxypropyltrimethoxysilane and 2-[(phosphonomethyl)amino]acetic acid (PMA), commonly known as glyphosate. The prepared adsorbent was fully characterised using elemental analysis, thermal gravimetric analysis (TGA), acid–base potentiometric titration, Fourier Transform Infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption isotherms at 77 K (BET), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The concentration of bonded PMA groups calculated from the nitrogen content was 0.38 mmol per gram. The adsorption of transition metal ions on PMA functionalised silica (HEPMAS) was studied from aqueous solutions having different pH and the following selectivity was established, Zn(II) < Co(II) < Cd(II) < Mn(II) < Ni(II) < Cu(II). The calculated values of distribution coefficients D for the adsorption of ecotoxic metal ions on HEPMAS are 5.0 × 10{sup 4}, 4.9 × 10{sup 5} and 2.6 × 10{sup 4} for Zn(II), Pb(II) and Cd(II), respectively.

  11. Functionalisation of mesoporous silica gel with 2-[(phosphonomethyl)-amino]acetic acid functional groups. Characterisation and application

    Science.gov (United States)

    Caldarola, Dario; Mitev, Dimitar P.; Marlin, Lucile; Nesterenko, Ekaterina P.; Paull, Brett; Onida, Barbara; Bruzzoniti, Maria Concetta; Carlo, Rosa Maria De; Sarzanini, Corrado; Nesterenko, Pavel N.

    2014-01-01

    A new complexing adsorbent was prepared by chemical modification of mesoporous silica Kieselgel 60 (dp = 37-63 μm, average pore size 6 nm, specific surface area 425 m2 g-1) with 3-glycidoxypropyltrimethoxysilane and 2-[(phosphonomethyl)amino]acetic acid (PMA), commonly known as glyphosate. The prepared adsorbent was fully characterised using elemental analysis, thermal gravimetric analysis (TGA), acid-base potentiometric titration, Fourier Transform Infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption isotherms at 77 K (BET), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). The concentration of bonded PMA groups calculated from the nitrogen content was 0.38 mmol per gram. The adsorption of transition metal ions on PMA functionalised silica (HEPMAS) was studied from aqueous solutions having different pH and the following selectivity was established, Zn(II) < Co(II) < Cd(II) < Mn(II) < Ni(II) < Cu(II). The calculated values of distribution coefficients D for the adsorption of ecotoxic metal ions on HEPMAS are 5.0 × 104, 4.9 × 105 and 2.6 × 104 for Zn(II), Pb(II) and Cd(II), respectively.

  12. Sol-gel silica-based nanocomposites containing a high PEG amount: Chemical characterization and study of biological properties

    Energy Technology Data Exchange (ETDEWEB)

    Catauro, Michelina; Bollino, Flavia [Department of Industrial and Information Engineering, Second University of Naples, Via Roma 29, 81031 Aversa (CE) (Italy); Gloria, Antonio [Institute of Polymers, Composites and Biomaterials - National Research Council of Italy, V.le J. F. Kennedy 54 - Mostra d’Oltremare Pad. 20, 80125 Naples (Italy)

    2016-05-18

    The objective of the present study was to synthesize and to characterize Silica/polyethylene glycol (SiO{sub 2}/PEG) organic-inorganic hybrid materials containing a high polymer amount (60 and 70 wt%) for biomedical applications. Scanning electron microscopy (SEM) showed that the samples are homogeneous on the nanometer scale, confirming that they are nanocomposites. Fourier transform infrared spectroscopy (FT-IR) proved that the materials are class I hybrids because the two phases (SiO{sub 2} and PEG) interact by hydrogen bonds. To evaluate the possibility of using them in the biomedical field, the bioactivity and biocompatibility of the synthesized hybrids have been ascertained. The formation of a hydroxyapatite layer was observed on the hybrid surface by SEM/EDX and FTIR after soaking in simulated body fluid (SBF). Moreover, their biocompatibility was assessed by performing WST-8 cytotoxicity assay in vitro.

  13. Sol-gel silica-based nanocomposites containing a high PEG amount: Chemical characterization and study of biological properties

    Science.gov (United States)

    Catauro, Michelina; Bollino, Flavia; Gloria, Antonio

    2016-05-01

    The objective of the present study was to synthesize and to characterize Silica/polyethylene glycol (SiO2/PEG) organic-inorganic hybrid materials containing a high polymer amount (60 and 70 wt%) for biomedical applications. Scanning electron microscopy (SEM) showed that the samples are homogeneous on the nanometer scale, confirming that they are nanocomposites. Fourier transform infrared spectroscopy (FT-IR) proved that the materials are class I hybrids because the two phases (SiO2 and PEG) interact by hydrogen bonds. To evaluate the possibility of using them in the biomedical field, the bioactivity and biocompatibility of the synthesized hybrids have been ascertained. The formation of a hydroxyapatite layer was observed on the hybrid surface by SEM/EDX and FTIR after soaking in simulated body fluid (SBF). Moreover, their biocompatibility was assessed by performing WST-8 cytotoxicity assay in vitro.

  14. Sol-gel silica-based nanocomposites containing a high PEG amount: Chemical characterization and study of biological properties

    International Nuclear Information System (INIS)

    Catauro, Michelina; Bollino, Flavia; Gloria, Antonio

    2016-01-01

    The objective of the present study was to synthesize and to characterize Silica/polyethylene glycol (SiO 2 /PEG) organic-inorganic hybrid materials containing a high polymer amount (60 and 70 wt%) for biomedical applications. Scanning electron microscopy (SEM) showed that the samples are homogeneous on the nanometer scale, confirming that they are nanocomposites. Fourier transform infrared spectroscopy (FT-IR) proved that the materials are class I hybrids because the two phases (SiO 2 and PEG) interact by hydrogen bonds. To evaluate the possibility of using them in the biomedical field, the bioactivity and biocompatibility of the synthesized hybrids have been ascertained. The formation of a hydroxyapatite layer was observed on the hybrid surface by SEM/EDX and FTIR after soaking in simulated body fluid (SBF). Moreover, their biocompatibility was assessed by performing WST-8 cytotoxicity assay in vitro.

  15. Vapor-Liquid Sol-Gel Approach to Fabricating Highly Durable and Robust Superhydrophobic Polydimethylsiloxane@Silica Surface on Polyester Textile for Oil-Water Separation.

    Science.gov (United States)

    Su, Xiaojing; Li, Hongqiang; Lai, Xuejun; Zhang, Lin; Wang, Jing; Liao, Xiaofeng; Zeng, Xingrong

    2017-08-23

    Large-scale fabrication of superhydrophobic surfaces with excellent durability by simple techniques has been of considerable interest for its urgent practical application in oil-water separation in recent years. Herein, we proposed a facile vapor-liquid sol-gel approach to fabricating highly durable and robust superhydrophobic polydimethylsiloxane@silica surfaces on the cross-structure polyester textiles. Scanning electron microscopy and Fourier transform infrared spectroscopy demonstrated that the silica generated from the hydrolysis-condensation of tetraethyl orthosilicate (TEOS) gradually aggregated at microscale driven by the extreme nonpolar dihydroxyl-terminated polydimethylsiloxane (PDMS(OH)). This led to construction of hierarchical roughness and micronano structures of the superhydrophobic textile surface. The as-fabricated superhydrophobic textile possessed outstanding durability in deionized water, various solvents, strong acid/base solutions, and boiling/ice water. Remarkably, the polyester textile still retained great water repellency and even after ultrasonic treatment for 18 h, 96 laundering cycles, and 600 abrasion cycles, exhibiting excellent mechanical robustness. Importantly, the superhydrophobic polyester textile was further applied for oil-water separation as absorption materials and/or filter pipes, presenting high separation efficiency and great reusability. Our method to construct superhydrophobic textiles is simple but highly efficient; no special equipment, chemicals, or atmosphere is required. Additionally, no fluorinated slianes and organic solvents are involved, which is very beneficial for environment safety and protection. Our findings conceivably stand out as a new tool to fabricate organic-inorganic superhydrophobic surfaces with strong durability and robustness for practical applications in oil spill accidents and industrial sewage emission.

  16. Bench-scale studies on capture of mercury on mineral non-carbon based sorbents

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yang [Huazhong Univ. of Science and Technology, Wuhan (China). State Key Lab. of Coal Combustion; Utah Univ., Salt Lake City, UT (United States). Dept. of Chemical Engineering; Wendt, Jost O.L. [Utah Univ., Salt Lake City, UT (United States). Dept. of Chemical Engineering; Zhang, Junying; Zheng, Chuguang [Huazhong Univ. of Science and Technology, Wuhan (China). State Key Lab. of Coal Combustion

    2013-07-01

    A new high-temperature, mineral non-carbon based dispersed sorbent derived from paper recycling products has been shown to capture mercury at high temperatures in excess of 600 C. The sorbent is consisted of kaolinite/calcite/lime mixtures. Experiments have been conducted on chemi-sorption of elemental mercury in air on a packed bed. The sorption occurs at temperatures between 600 and 1,100 C and requires activation of the minerals contained within the sorbents. Mercury capture is dominated by temperature and capture on sorbents over long time scales. The capture shows a maximum effectiveness at 1,000 C and increases monotonically with temperature. The presence of oxygen is also the required. Freshly activated sorbent is the most effective, and deactivation of sorbents occurs at high temperatures with long pre-exposure times. This activation is suspected to involve a solid-solid reaction between intimately mixed calcium oxide and silica that are both contained within the sorbent. Deactivation occurs at temperatures higher than 1,000 C, and this is due to melting of the substrate and pore closure. The situation in packed beds is complicated because the bed also shrinks, thus allowing channeling and by-passing, and consequent ambiguities in determining sorbent saturation. Sorbent A had significantly greater capacity for mercury sorption than did Sorbent B, for all temperatures and exposure time examined. The effect of SiO{sub 2} on poor Sorbent B is much larger than sorbent A.

  17. The selective cleanup of complex matrices and simultaneous separation of benzo[a]pyrene by solid-phase extraction with MgO microspheres as sorbents.

    Science.gov (United States)

    Jin, Jing; Li, Yun; Zhang, Zhiping; Su, Fan; Qi, Peipei; Lu, Xianbo; Chen, Jiping

    2011-12-23

    A new method for the selective cleanup of complex matrices and simultaneous separation of benzo[a]pyrene (BaP) was developed in this study. This method was based on solid-phase extraction (SPE) using magnesium oxide microspheres as sorbents, and it eliminated interferences from various impurities, such as lipids, sulphur, pigments, halobenzenes, polychlorodibenzo-p-dioxins and polychlorodibenzofurans. Several parameters, including the volume of rinsing and eluting solvents, the type of loading solvents and SPE sorbents, were optimized systematically. The capability for impurity removal was verified by gel permeation chromatography, gas chromatography, and liquid chromatography. Compared to commercial sorbents (silica gel, florisil and alumina), MgO microspheres exhibited excellent performance in the selective isolation of BaP and removal of impurities. The proposed method was applied to detect BaP in complex samples (sediments, soils, fish, and porcine liver). The limit of quantification (LOQ) was 1.04 ngL(-1), and the resulting regression coefficient (r(2)) was greater than 0.999 over a broad concentration range (9.5-7600 ngL(-1)). In contrast to traditional methods, the proposed method can give rise to higher recovery (85.1-100.8%) and better selectivity with simpler operation and less consumption of organic solvents (20-40 mL). Copyright © 2011 Elsevier B.V. All rights reserved.

  18. Desulfurization sorbent regeneration

    Science.gov (United States)

    Jalan, V.M.; Frost, D.G.

    1982-07-07

    A spent solid sorbent resulting from the removal of hydrogen sulfide from a fuel gas flow is regenerated with a steam-air mixture. The mixture of steam and air may also include additional nitrogen or carbon dioxide. The gas mixture contacts the spent sorbent containing metal sulfide at a temperature above 500/sup 0/C to regenerate the sulfide to metal oxide or carbonate. Various metal species including the period four transition metals and the lanthanides are suitable sorbents that may be regenerated by this method. In addition, the introduction of carbon dioxide gas permits carbonates such as those of strontium, barium and calcium to be regenerated. The steam permits regeneration of spent sorbent without formation of metal sulfate. Moreover, the regeneration will proceed with low oxygen concentrations and will occur without the increase in temperature to minimize the risk of sintering and densification of the sorbent. This method may be used for high-temperature fuel cells.

  19. Structural and optical characterization of oxygenated CdTe/Sm3+ in sol-gel silica glasses

    International Nuclear Information System (INIS)

    Mathew, Siby; Rejikumar, P.R.; Adiyodi, Amrutha K.; Jyothy, P.V.; Unnikrishnan, N.V.

    2008-01-01

    Oxygenated cadmium telluride co-doped with rare earth element samarium is prepared by sol-gel method. Sample is air annealed at 200, 500 and 800 deg. C. The absorption and fluorescence spectra are analysed using Judd-Ofelt analysis to obtain J-O parameters. X-ray spectroscopy analysis shows the presence of thermally grown CdTeO 3 phase developed at the expense of CdTe phase on heat treatment for samples annealed at 800 deg. C. The FT-IR spectrum of the sample is taken at different annealing temperatures and the assignments of the absorption bands are compiled which shows the gradual evolution of the rigid glassy network formed. Enhanced fluorescence from air annealed Co-doped samples are also investigated

  20. Investigation of bioactivity, biocompatibility and thermal behavior of sol–gel silica glass containing a high PEG percentage

    Energy Technology Data Exchange (ETDEWEB)

    Catauro, M., E-mail: michelina.catauro@unina2.it [Department of Industrial and Information Engineering, Second University of Naples, Via Roma 29, 81031 Aversa (Italy); Renella, R.A.; Papale, F. [Department of Industrial and Information Engineering, Second University of Naples, Via Roma 29, 81031 Aversa (Italy); Vecchio Ciprioti, S. [Department of Basic and Applied Science for Engineering, Sapienza University of Rome, Via del Castro Laurenziano 7, Building RM017, I-00161 Rome (Italy)

    2016-04-01

    SiO{sub 2}/PEG organic–inorganic hybrid materials, which contain 60 or 70 weight percentage of PEG, were synthesized by the sol–gel technique. The materials were characterized and subjected to various tests to assess their application in the biomedical field. The evaluation of their morphology by scanning electron microscopy (SEM) confirms the homogeneity of the samples on the nanometer scale. Fourier transform infrared spectroscopy (FT-IR) indicated that the two components of the hybrids (SiO{sub 2} and PEG) are linked by hydrogen bonds. This feature makes them class I hybrids. Simultaneous thermogravimetry/differential thermal analysis (TG/DTA) was used to investigate their thermal behavior and to establish the best temperatures for their pre-treatment. The fundamental properties that a material must have to be used in the biomedical field are biocompatibility and bioactivity. The formation of a hydroxyapatite layer was observed on the hybrid surface by SEM/EDX and FTIR after soaking in simulated body fluid. This indicates that the materials are able to bond to bone tissue. Moreover, the biocompatibility of SiO{sub 2}/PEG hybrids was assessed by performing WST-8 cytotoxicity tests on fibroblast cell NIH 3T3 after 24 h of exposure. The cytotoxicity tests highlight that the cell viability is affected by the polymer percentage. The results showed that the synthesized materials were bioactive and biocompatible. Therefore, the results obtained are encouraging for the use of the obtained hybrids in dental or orthopedic applications. - Highlights: • SiO{sub 2}/PEG hybrid biomaterials synthesized by sol–gel method at high PEG percentage • Chemical, thermal and morphological characterization of hybrid materials • Biological characterizations with WST-8 cytotoxicity tests • Bioactivity characterizations of hybrid materials with high PEG percentage.

  1. Electrochemical and electrocatalytic studies of toluidine blue immobilized on a silica gel surface coated with niobium oxide

    Directory of Open Access Journals (Sweden)

    Santos Antonio S.

    2002-01-01

    Full Text Available The electrochemical behavior of toluidine blue (TB adsorbed on a silica surface modified with niobium oxide (SN was investigated using a modified carbon paste electrode. The presence of SN gave the electrode high stability, avoiding the leaching out of the mediator from the electrode surface. The formal potential (E0' of the adsorbed TB was --113 mV vs. SCE, indicating a shift of almost 100 mV towards more positive potential values, compared to TB dissolved in aqueous solution or adsorbed on carbon paste. The stability and formal potential remained constant upon changing the solution pH in the range 5 to 8. In these solution pH values the electrocatalytic activity remained almost constant with a sensitivity of 1.2 10-4 A L mol-1 cm-2 and a K Mapp of 4.9 10-5 mol L-1. A linear response range for NADH concentration between 2.0 10-4 and 4.0 10-3 mol L-1 at pH 7.0, with a detection limit of 3.4 10-5 mol L-1 was observed for the sensor. A response time of 2 s and a precision of 1.0 %, expressed as relative standard deviation for 10 replicates, were observed for the sensor developed.

  2. Metal Oxide Thin Films Grafted on Silica Gel Surfaces: Recent Advances on the Analytical Application of these Materials

    Directory of Open Access Journals (Sweden)

    Gushikem Yoshitaka

    2001-01-01

    Full Text Available In the highly dispersed MxOy monolayer film on a porous SiO2 surface, denoted as SiO2/MxOy, the Si-O-M covalent bond formed on the SiO2 surface restricts the mobility of the attached oxide resulting in coordinatively unsaturated metal oxides (LAS in addition to the Brønsted acid sites (BAS. The BAS arise from the MOH and SiOH groups, the latter due to the unreacted silanol groups. As the attached oxides are strongly immobilized on the surface, they are also thermally very stable. The amphoteric character of most of the attached oxides allows the immobilization of various chemical species, acid or bases, resulting in a wide application of these surface modified materials. In this work many of the recent applications of these MxOy coated silica surfaces are described, such as selective adsorbents, in preconcentration processes, as new packing material for use in HPLC, support for immobilization of enzymes, amperometric electrodes, sensors and biosensors

  3. Mesoporous Silica Gel-Based Mixed Matrix Membranes for Improving Mass Transfer in Forward Osmosis: Effect of Pore Size of Filler.

    Science.gov (United States)

    Lee, Jian-Yuan; Wang, Yining; Tang, Chuyang Y; Huo, Fengwei

    2015-11-23

    The efficiency of forward osmosis (FO) process is generally limited by the internal concentration polarization (ICP) of solutes inside its porous substrate. In this study, mesoporous silica gel (SG) with nominal pore size ranging from 4-30 nm was used as fillers to prepare SG-based mixed matrix substrates. The resulting mixed matrix membranes had significantly reduced structural parameter and enhanced membrane water permeability as a result of the improved surface porosity of the substrates. An optimal filler pore size of ~9 nm was observed. This is in direct contrast to the case of thin film nanocomposite membranes, where microporous nanoparticle fillers are loaded to the membrane rejection layer and are designed in such a way that these fillers are able to retain solutes while allowing water to permeate through them. In the current study, the mesoporous fillers are designed as channels to both water and solute molecules. FO performance was enhanced at increasing filler pore size up to 9 nm due to the lower hydraulic resistance of the fillers. Nevertheless, further increasing filler pore size to 30 nm was accompanied with reduced FO efficiency, which can be attributed to the intrusion of polymer dope into the filler pores.

  4. Electrochemical properties of the hexacyanoferrate(II)–ruthenium(III) complex immobilized on silica gel surface chemically modified with zirconium(IV) oxide

    International Nuclear Information System (INIS)

    Panice, Lucimara B.; Oliveira, Elisangela A. de; Filho, Ricardo A.D. Molin; Oliveira, Daniela P. de; Lazarin, Angélica M.; Andreotti, Elza I.S.; Sernaglia, Rosana L.; Gushikem, Yoshitaka

    2014-01-01

    Highlights: • The cyano-bridged mixed valence ruthenium composite material was synthesized. • This newly synthesized compound was incorporated into a carbon paste electrode. • The electrode did not show significant changes in response after six months of use. • The modified electrode is very stable and reproducible. • The electrode sensor was successfully applied for ascorbic acid determination. - Abstract: The chemically modified silica gel with zirconium(IV) oxide was used to immobilize the [Fe(CN) 6 ] 4− complex ion initially. The reaction of this material with [Ru(edta)H 2 O] − complex ion formed the immobilized cyano-bridged mixed valence ruthenium complex, (≡Zr) 5 [(edta)RuNCFe(CN) 5 ]. This material was incorporated into a carbon paste electrode and, its electrochemical properties were investigated. However, for an ascorbic acid solution, an enhancement of the anodic peak current was detected due to electrocatalytic oxidation. The electrode presented the same response for at least 150 successive measurements, with a good repeatability. The modified electrode is very stable and reproducible. The sensor was applied for ascorbic acid determination in pharmaceutical preparation with success

  5. Detection of volatile organic compounds using an optical fiber sensor coated with a sol-gel silica layer containing immobilized Nile red

    Science.gov (United States)

    Liu, Dejun; Lian, Xiaokang; Mallik, Arun Kumar; Han, Wei; Wei, Fangfang; Yuan, Jinhui; Yu, Chongxiu; Farrell, Gerald; Semenova, Yuliya; Wu, Qiang

    2017-04-01

    A simple volatile organic compound (VOC) sensor based on a tapered small core singlemode fiber (SCSMF) structure is reported. The tapered SCSMF fiber structure with a waist diameter of 7.0 μm is fabricated using a customized microheater brushing technique. Silica based material containing immobilized Nile red was prepared by a sol-gel method and was used as a coating applied to the surface of the tapered fiber structure. Different coating thicknesses created by a 2-pass and 4-pass coating process are investigated. The experiments demonstrate that both sensors show a linear response at different gas concentrations to all three tested VOCs (methanol, ethanol and acetone). The sensor with a thicker coating shows better sensitivities but longer response and recovery times. The best measurement resolutions for the 4-pass coating sensor are estimated to be 2.3 ppm, 1.5 ppm and 3.1 ppm for methanol, ethanol and acetone, respectively. The fastest response and recovery time of 1 min and 5 min are demonstrated by the sensor in the case of methanol.

  6. Synthesis and characterization of organically modified silica gel with 4-amino-5-(4-pyridyl)-4h-1 ,2,4-triazole-3-thiol (APTT)

    International Nuclear Information System (INIS)

    Magossi, M.S.; Carmo, D.R. do

    2014-01-01

    This work object the preparation and characterization of a silica gel (SG) organically with a triazole compound, 4-amino-5-(4-pyridyl)-4H-1,2,4-triazole-3- thiol (APTT). The prepared organofunctionalized material (SGAPTT) was preliminarily characterized by spectroscopic techniques such as: Spectroscopy in the Region of Infrared (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy X-ray (EDX). The vibrational spectrum (FTIR) showed characteristic bands of the starting materials, such as bands at ∼ 1120cm"-"1 related to the asymmetric stretching Si-O-Si (νSi-O-Si) as well as the bands between 1350 and 1650 cm"-"1 assigned vibrations and deformations of the ring APTT. The SGAPTT material was tested as support for adsorption of cupric ions in aqueous solution, ethanol and 42% ethanol. The maximum amount of copper (II) adsorbed (Nf "m"a"x".) was 22.0 × 10"-"5 mol g"-"1, 31.4 × 10-5 mol g-1 and 47.17 × 10"-"5 mol g"-"1 to aqueous media, 42% ethanol and 99% ethanol respectively. (author)

  7. LABORATORY TESTS ON INSECTICIDAL EFFECTIVENESS OF DISODIUM OCTABORATE TETRAHYDRATE, DIATOMACEOUS EARTH AND AMORPHOUS SILICA GEL AGAINST Sitophilus oryzae (L. AND THEIR EFFECT ON WHEAT BULK DENSITY

    Directory of Open Access Journals (Sweden)

    Zlatko Korunić

    2017-01-01

    Full Text Available We examined insecticide effectiveness of three different inert dusts: disodium octaborate tetrahydrate (DOT and diatomaceous earth (DE Celatom® Mn 51 applied as powder and suspension, and silica gel Sipernat® 50 S applied as powder against Sitophilus oryzae (L. and their reduction of grain bulk density. Sipernat® 50 S was the most effective dust with a very fast initial effectiveness. DE and DOT generated similar effectiveness against S. oryzae. DOT generated low initial effectiveness but after prolonged exposure time of 8 and especially after 21 days, the mortality was very high (100%, similar to the effectiveness of DE. The similar order of dusts was obtained in the reduction of wheat bulk density. Applied at dose of 200 and 500 ppm, the lowest bulk density difference in regard to bulk density of untreated wheat had DOT (-1.1 and -1.9 kg hl-1, respectively, followed by Celatom® Mn 51 (-3.5 and -4.3 kg hl-1, respectively and Sipernat® 50 S (-5.2 and -5.5 kg hl-1, respectively. Due to the effect on wheat bulk density DOT belongs to the group with the least negative effect on bulk density and therefore, it is a promising dust to control stored grain insect pests.

  8. Experimental Results and Model Calculations of a Hybrid Adsorption-Compression Heat Pump Based on a Roots Compressor and Silica Gel-Water Sorption

    Energy Technology Data Exchange (ETDEWEB)

    Van der Pal, M.; De Boer, R.; Wemmers, A.K.; Smeding, S.F.; Veldhuis, J.B.J.; Lycklama a Nijeholt, J.A.

    2013-10-15

    Thermally driven sorption systems can provide significant energy savings, especially in industrial applications. The driving temperature for operation of such systems limits the operating window and can be a barrier for market-introduction. By adding a compressor, the sorption cycle can be run using lower waste heat temperatures. ECN has recently started the development of such a hybrid heat pump. The final goal is to develop a hybrid heat pump for upgrading lower (<100C) temperature industrial waste heat to above pinch temperatures. The paper presents the first measurements and model calculations of a hybrid heat pump system using a water-silica gel system combined with a Roots type compressor. From the measurements can be seen that the effect of the compressor is dependent on where in the cycle it is placed. When placed between the evaporator and the sorption reactor, it has a considerable larger effect compared to the compressor placed between the sorption reactor and the condenser. The latter hardly improves the performance compared to purely heat-driven operation. This shows the importance of studying the interaction between all components of the system. The model, which shows reasonable correlation with the measurements, could proof to be a valuable tool to determine the optimal hybrid heat pump configuration.

  9. Graft shrinkage and survival rate of implants after sinus floor elevation using a nanocrystalline hydroxyapatite embedded in silica gel matrix: a 1-year prospective study.

    Science.gov (United States)

    El Hage, Marc; Abi Najm, Semaan; Bischof, Mvark; Nedir, Rabah; Carrel, Jean-Pierre; Bernard, Jean-Pierre

    2012-06-01

    The aims of this study were (1) to evaluate the vertical shrinkage percentage of nanocrystalline hydroxyapatite embedded in silica gel used for maxillary sinus floor elevation (SFE) and (2) to determine the survival rate of the implants 1 year after placement in the healed grafted sinuses. Eleven maxillary sinuses were augmented in eight patients with NanoBone. After a healing period averaging 14.42 months, 19 implants were placed and followed up with clinical and radiographic evaluation. Panoramic radiographs were taken immediately after SFE and at 12 months after grafting. Measurements of changes in height were made by a computerized measuring technique using an image editing software. The mean graft height shrinkage percentage at 12 months after surgery was 8.84% (±5.32). One implant was lost before loading. All the 18 remaining osseointegrated implants received the prosthetic rehabilitation and were controlled after 3 months of functional loading. The implant survival rate at the 1-year interval was 94.74%. A 100% NanoBone alloplastic graft used in lateral SFE procedures presented limited height shrinkage. Implants placed in these grafted sinuses showed survival rates similar to those found in published data. These results should be interpreted cautiously considering the study's reduced sample size.

  10. Isolation of two new prenylated flavonoids from Sinopodophyllum emodi fruit by silica gel column and high-speed counter-current chromatography.

    Science.gov (United States)

    Sun, Yanjun; Sun, Yinshi; Chen, Hui; Hao, Zhiyou; Wang, Junmin; Guan, Yanbin; Zhang, Yanli; Feng, Weisheng; Zheng, Xiaoke

    2014-10-15

    Two new prenylated flavonoids, sinoflavonoids A-B, were isolated from the dried fruits of Sinopodophyllum emodi by silica gel column chromatography (SGCC) and high-speed counter-current chromatography (HSCCC). The 95% ethanol extract was partitioned with petroleum ether, dichloromethane, ethyl acetate, and n-butanol in water, respectively. The ethyl acetate fraction was pre-separated by SGCC with a petroleum ether-acetone gradient. The eluates containing target compounds were further separated by HSCCC with n-hexane-ethyl acetate-methanol-water (4:6:4:4, v/v). Finally, 17.3mg of sinoflavonoid A and 25.9mg of sinoflavonoid B were obtained from 100mg of the pretreated concentrate. The purities of sinoflavonoid A and sinoflavonoid B were 98.47% and 99.38%, respectively, as determined by HPLC. Their structures were elucidated on the basis of spectroscopic evidences (HR-ESI-MS, (1)H-NMR, (13)C-NMR, HSQC, HMBC). The separation procedures proved to be efficient, especially for trace prenylated flavonoids. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. 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.

  12. 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.

  13. Quasi-homogenous approximation for description of the properties of dispersed systems. The basic approaches to model hardening processes in nanodispersed silica systems. Part 4. The Main Approaches to Modeling the Kinetics of the Sol-Gel Transition

    Directory of Open Access Journals (Sweden)

    KUDRYAVTSEV Pavel Gennadievich

    2015-08-01

    Full Text Available The paper deals with possibilities to use quasi-homogenous approximation for description of properties of dispersed systems. The authors applied statistical polymer method based on consideration of average structures of all possible macromolecules of the same weight. The equations which allow evaluating many additive parameters of macromolecules and the systems with them were deduced. Statistical polymer method makes it possible to model branched, cross-linked macromolecules and the systems with them which are in equilibrium or non-equilibrium state. Fractal analysis of statistical polymer allows modeling different types of random fractal and other objects examined with the methods of fractal theory. The method of fractal polymer can be applied not only to polymers but also to composites, gels, associates in polar liquids and other packaged systems. There is also a description of the states of colloid solutions of silica oxide from the point of view of statistical physics. This approach is based on the idea that colloid solution of silica dioxide – sol of silica dioxide – consists of enormous number of interacting particles which are always in move. The paper is devoted to the research of ideal system of colliding but not interacting particles of sol. The analysis of behavior of silica sol was performed according to distribution Maxwell-Boltzmann and free path length was calculated. Using this data the number of the particles which can overcome the potential barrier in collision was calculated. To model kinetics of sol-gel transition different approaches were studied.

  14. Solid-phase extraction method for preconcentration of trace amounts of some metal ions in environmental samples using silica gel modified by 2,4,6-trimorpholino-1,3,5-triazin

    International Nuclear Information System (INIS)

    Madrakian, Tayyebeh; Zolfigol, Mohammad Ali; Solgi, Mohammad

    2008-01-01

    A method was proposed for the preconcentration of some transition elements at trace levels using a column packed with silica gel modified by a synthetic ligand. Metal ions were adsorbed on 2,4,6-trimorpholino-1,3,5-triazin modified silica gel, then analytes retained on the adsorbent were eluted by 1 mol L -1 hydrochloric acid and determined by flame atomic absorption spectrometry (FAAS). The influences of some experimental parameters including pH of the sample solution, weight of adsorbent, type, concentration and volume of eluent, flow rates of the sample solution and eluent, and sample volume on the preconcentration efficiency have been investigated. The influences of some matrix elements were also examined. The method also was used for simultaneous preconcentration of these elements and the method was successfully applied to the preconcentration and determination of them. The detection limits of the method for Ni 2+ , Co 2+ , Cd 2+ and Zn 2+ were 0.29, 0.20, 0.23 and, 0.30 ng mL -1 , respectively. The application of this modified silica gel to preconcentration of investigated cation from tap water, lake water, urine and apple leaves gave high accuracy and precision (relative standard deviation (R.S.D.) <3%)

  15. Sorbent Scoping Studies

    International Nuclear Information System (INIS)

    Chancellor, Christopher John

    2016-01-01

    The Los Alamos National Laboratory-Carlsbad Operations (LANL-CO) office was tasked by the DOE CBFO, Office of the Manager to perform a review of the acceptable knowledge (AK) to identify the oxidizers and sorbents in transuranic (TRU) waste streams, to conduct scoping studies on the oxidizers and sorbents identified in AK review to inform the Quality Level 1 (QL1) testing, and to conduct a series of QL1 tests to provide the scientific data to support a basis of knowledge document for determining the criteria for (1) accepting waste at the Waste Isolation Pilot Plant (WIPP) without treatment, (2) determining waste that will require treatment, and (3) if treatment is required, how the treatment must be performed. The purpose of this report is to present the results of the AK review of sorbents present in active waste streams, provide a technical analysis of the sorbent list, report the results of the scoping studies for the fastest-burning organic sorbent, and provide the list of organic and inorganic sorbents to be used in the development of a Test Plan for Preparation and Testing of Sorbents Mixed with Oxidizer found in Transuranic Waste (DWT-TP-001). The companion report, DWT-RPT-001, Oxidizer Scoping Studies, has similar information for oxidizers identified during the AK review of TRU waste streams. The results of the oxidizer and sorbent scoping studies will be used to inform the QL1 test plan. The QL1 test results will support the development of a basis of knowledge document that will evaluate oxidizing chemicals and sorbents in TRU waste and provide guidance for treatment.

  16. Sorbent Scoping Studies

    Energy Technology Data Exchange (ETDEWEB)

    Chancellor, Christopher John [Los Alamos National Lab. (LANL), Carlsbad, NM (United States). Difficult Waste Team

    2016-11-14

    The Los Alamos National Laboratory–Carlsbad Operations (LANL-CO) office was tasked by the DOE CBFO, Office of the Manager to perform a review of the acceptable knowledge (AK) to identify the oxidizers and sorbents in transuranic (TRU) waste streams, to conduct scoping studies on the oxidizers and sorbents identified in AK review to inform the Quality Level 1 (QL1) testing, and to conduct a series of QL1 tests to provide the scientific data to support a basis of knowledge document for determining the criteria for (1) accepting waste at the Waste Isolation Pilot Plant (WIPP) without treatment, (2) determining waste that will require treatment, and (3) if treatment is required, how the treatment must be performed. The purpose of this report is to present the results of the AK review of sorbents present in active waste streams, provide a technical analysis of the sorbent list, report the results of the scoping studies for the fastest-burning organic sorbent, and provide the list of organic and inorganic sorbents to be used in the development of a Test Plan for Preparation and Testing of Sorbents Mixed with Oxidizer found in Transuranic Waste (DWT-TP-001). The companion report, DWT-RPT-001, Oxidizer Scoping Studies, has similar information for oxidizers identified during the AK review of TRU waste streams. The results of the oxidizer and sorbent scoping studies will be used to inform the QL1 test plan. The QL1 test results will support the development of a basis of knowledge document that will evaluate oxidizing chemicals and sorbents in TRU waste and provide guidance for treatment.

  17. Silica-Immobilized Enzyme Reactors

    Science.gov (United States)

    2007-08-01

    Silica-IMERs 14 implicated in neurological disorders such as Schizophrenia and Parkinson’s disease.[86] Drug discovery for targets that can alter the...primarily the activation of prodrugs and proantibiotics for cancer treatments or antibiotic therapy , respectively.[87] Nitrobenzene nitroreductase was...BuChE) Monolith disks* Packed Silica Biosilica Epoxide- Silica Silica-gel Enzyme Human AChE Human AChE Human AChE Equine BuChE Human

  18. Engineering and characterization of mesoporous silica-coated magnetic particles for mercury removal from industrial effluents

    International Nuclear Information System (INIS)

    Dong Jie; Xu Zhenghe; Wang Feng

    2008-01-01

    Mesoporous silica coatings were synthesized on dense liquid silica-coated magnetite particles using cetyl-trimethyl-ammonium chloride (CTAC) as molecular templates, followed by sol-gel process. A specific surface area of the synthesized particles as high as 150 m 2 /g was obtained. After functionalization with mercapto-propyl-trimethoxy-silane (MPTS) through silanation reaction, the particles exhibited high affinity of mercury in aqueous solutions. Atomic force microscopy (AFM), zeta potential measurement, thermal gravimetric analysis (TGA), analytical transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and atomic absorption spectroscopy (AAS) were used to characterize the synthesis processes, surface functionalization, and mercury adsorption on the synthesized magnetite particles. The loading capacity of the particles for mercury was determined to be as high as 14 mg/g at pH 2. A unique feature of strong magnetism of the synthesized nanocomposite particles makes the subsequent separation of the magnetic sorbents from complex multiphase suspensions convenient and effective

  19. Engineering and characterization of mesoporous silica-coated magnetic particles for mercury removal from industrial effluents

    Science.gov (United States)

    Dong, Jie; Xu, Zhenghe; Wang, Feng

    2008-03-01

    Mesoporous silica coatings were synthesized on dense liquid silica-coated magnetite particles using cetyl-trimethyl-ammonium chloride (CTAC) as molecular templates, followed by sol-gel process. A specific surface area of the synthesized particles as high as 150 m 2/g was obtained. After functionalization with mercapto-propyl-trimethoxy-silane (MPTS) through silanation reaction, the particles exhibited high affinity of mercury in aqueous solutions. Atomic force microscopy (AFM), zeta potential measurement, thermal gravimetric analysis (TGA), analytical transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and atomic absorption spectroscopy (AAS) were used to characterize the synthesis processes, surface functionalization, and mercury adsorption on the synthesized magnetite particles. The loading capacity of the particles for mercury was determined to be as high as 14 mg/g at pH 2. A unique feature of strong magnetism of the synthesized nanocomposite particles makes the subsequent separation of the magnetic sorbents from complex multiphase suspensions convenient and effective.

  20. The Influence of Lyophilized EmuGel Silica Microspheres on the Physicomechanical Properties, In Vitro Bioactivity and Biodegradation of a Novel Ciprofloxacin-Loaded PCL/PAA Scaffold

    Directory of Open Access Journals (Sweden)

    Mostafa Mabrouk

    2016-06-01

    Full Text Available A new composite poly(caprolactone (PCL and poly(acrylic acid (PAA (PCL:PAA 1:5 scaffold was synthesized via dispersion of PCL particles into a PAA network. Silica microspheres (Si (2–12 μm were then prepared by a lyophilized micro-emulsion/sol-gel (Emugel system using varying weight ratios. The model drug ciprofloxacin (CFX was used for in situ incorporation into the scaffold. The physicochemical and thermal integrity, morphology and porosity of the system was analyzed by X-Ray Diffraction (XRD, Attenuated Total Refelctance Fourier Transform Infrared (ATR-FTIR, Differential Scanning Calorimetry (DSC, SEM, surface area analysis and liquid displacement, respectively. The mechanical properties of the scaffold were measured by textural analysis and in vitro bioactivity, biodegradation and pH variations were evaluated by XRD, FTIR and SEM after immersion in Simulated Body Fluid (SBF. The in vitro and in vivo studies of the prepared scaffold were considered as future aspects for this study. CFX release was determined in phosphate buffer saline (PBS (pH 7.4; 37 °C. The incorporation of the Si microspheres and CFX into the scaffold was confirmed by XRD, FTIR, DSC and SEM, and the scaffold microstructure was dependent on the concentration of Si microspheres and the presence of CFX. The system displayed enhanced mechanical properties (4.5–14.73 MPa, in vitro bioactivity, biodegradation and controlled CFX release. Therefore, the PCL/PAA scaffolds loaded with Si microspheres and CFX with a porosity of up to 87% may be promising for bone tissue engineering.

  1. Study of the influence of humic acids (in solution or bound to a silica gel) on the migration of europium in a porous medium. Comparison with inorganic colloids

    International Nuclear Information System (INIS)

    Fleury, Ch.

    1998-01-01

    After having been reprocessed, radioactive wastes are stored in conditions which depend on the toxicity of the radioelements. In particular, for the actinides, the packaging has to be sure for several thousands years. In the case of a defective storage, phenomena which favour or diminish the migration of radioelements in the environment have to be identified. In water, organic or inorganic colloids able to bind radioelements can migrate. Among these colloids, are found the humic acids (HA), macromolecules (poly-electrolytes and poly-dispersed) known for their affinity towards some radioelements. These HA are either present on a soluble state or bound to mineral supports. Humic acids have then been studied in these two states and their influence on the europium migration in dynamical system have been observed (ion exchange and affinity chromatography). When HA are bound by covalent bonds to silica gel, they strongly retain the radioelement, whatever be the conditions of pH, flow rate or ionic strength, and either if phosphate ions are present. The study of HA in solution has shown that, on the one hand the formation of a Eu-HA complex alters the adsorption of the radioelement on sand and that the influence of the humic acids on the europium retention is superior to those of the inorganic colloids (silicon oxide, bentonite). On the other hand, the study has revealed that a solution containing HA desorbs almost entirely the europium beforehand bound to the sand. This desorption depends on the pH and on the flow rate but not on the presence of competitive ions as for instance phosphate ions. (O.M.)

  2. Synthesis and physical properties of TEOS-based silica aerogels prepared by two step (acid-base) sol-gel process

    International Nuclear Information System (INIS)

    Venkateswara Rao, A.; Bhagat, S.D.

    2004-01-01

    The experimental results on the synthesis and physical properties of tetra-ethoxy-silane- (TEOS) based silica aerogels produced by two step (acid-base) sol-gel process, are reported. The oxalic acid (A) and NH 4 OH (B) concentrations were varied from 0 to 0.1 M and from 0.4 to 3 M, respectively. Monolithic and transparent aerogels have been obtained for the values of A=0.001 M and B=1 M. The effect of time interval (t) before the base catalyst (NH 4 OH) addition to the acidic sol was studied from 0 to 72 h. The time interval at t=24 h of NH 4 OH addition was found to be the best, in terms of low volume shrinkage, high optical transmission and monolithicity. The molar ratio of EtOH/TEOS (S) was varied from 3 to 7.5. Monolithic and transparent aerogels were obtained for an S value of 6.9. Also, the effects of molar ratio of acidic water, i.e., H 2 O/TEOS (W1) and basic water, i.e., H 2 O/TEOS (W2) on the physical properties of the aerogels have been studied. Highly transparent (about 90%) and monolithic aerogels with lower volume shrinkage ( 2 O):basic (H 2 O). The results are discussed by taking into consideration the hydrolysis and poly-condensation reactions. The aerogels were characterized by scanning electron microscopy (SEM), optical transmission, bulk density, volume shrinkage and porosity measurements. (authors)

  3. Sorption of radionuclides on inorganic sorbents

    International Nuclear Information System (INIS)

    Rajec, P.; Matel, L.

    1995-01-01

    The sorption of cesium, strontium, plutonium and americium from water solution on natural zeolite, clay minerals, synthetic zeolites and ferrocyanides in silica gel matrix was studied. The same experiments but with synthetic zeolites irradiated by the dose 100 kGy proved no change in sorption properties. 1 tab., 4 refs

  4. Sorption of agrochemical model compounds by sorbent materials containing beta-cyclodextrin.

    Science.gov (United States)

    Wilson, Lee D; Mohamed, Mohamed H; Guo, Rui; Pratt, Dawn Y; Kwon, Jae Hyuck; Mahmud, Sarker T

    2010-04-01

    Polymeric sorbent materials that incorporate beta-cyclodextrin (CD) have been prepared and their sorption behavior toward two model agrochemical contaminant compounds, p-nitrophenol (PNP) and methyl chloride examined. The sorption of PNP was studied in aqueous solution using ultraviolet-visible (UV-Vis) spectroscopy, whereas the sorption of methyl chloride from the gas phase was studied using a Langmuir adsorption method. The sorption results for PNP in solution were compared between granular activated carbon (GAC), modified GAC, CD copolymers, and CD-based mesoporous silica hybrid materials. Nitrogen porosimetry at 77 K was used to estimate the surface area and pore structure properties of the sorbent materials. The sorbents displayed variable surface areas as follows: copolymers (36.2-157 m(2)/g), CD-silica materials (307-906 m(2)/g), surface modified GAC (657 m(2)/g), and granular activated carbon (approximately 10(3) m(2)/g). The sorption capacities for PNP and methyl chloride with the different sorbents are listed in descending order as follows: GAC > copolymers > surface modified GAC > CD-silica hybrid materials. In general, the differences in the sorption properties of the sorbents were related to the following: (i) surface area of the sorbent, (ii) CD content and accessibility, (iii) and the chemical nature of the sorbent material.

  5. Multifunctional silver nanoparticle-doped silica for solid-phase extraction and surface-enhanced Raman scattering detection

    Science.gov (United States)

    Markina, Natalia E.; Markin, Alexey V.; Zakharevich, Andrey M.; Gorin, Dmitry A.; Rusanova, Tatiana Yu.; Goryacheva, Irina Yu.

    2016-12-01

    Multifunctional silica gel with embedded silver nanoparticles (SiO2-AgNP) is proposed for application as sorbent for solid-phase extraction (SPE) and simultaneously as substrate for surface-enhanced Raman spectroscopy (SERS) due to their high sorption properties and ability to enhance Raman signal (SERS-active sorbents). SiO2-AgNP was synthesized via alkaline hydrolysis of tetraethyl orthosilicate with simultaneous reduction of silver ions to silver nanoparticles (AgNP) within the SiO2 bulk. Synthesis of AgNP directly to the SiO2 matrix enables to exclude any additional stabilizers for the nanoparticles that educes signal-to-noise ratio during SERS measurement. Apart from Raman spectroscopy, obtained sorbents were also characterized by scanning electron microscopy and UV-visible diffuse reflectance spectroscopy. The influence of AgNO3 concentration used during the SiO2-AgNP synthesis on its gelling time, color, diffuse reflectance spectra, and enhancement of Raman signal was investigated. A Raman enhancement factor of SiO2-AgNP with optimal composition was around 105. Finally, the sorbents were applied for SPE and subsequent SERS detection of model compounds (rhodamine 6G and folic acid). It was found that SPE enables to decrease detectable concentrations by two orders. Therefore, SPE combined with SERS has high potential for further analytical investigations.

  6. Multifunctional silver nanoparticle-doped silica for solid-phase extraction and surface-enhanced Raman scattering detection

    Energy Technology Data Exchange (ETDEWEB)

    Markina, Natalia E.; Markin, Alexey V., E-mail: av-markin@mail.ru; Zakharevich, Andrey M.; Gorin, Dmitry A.; Rusanova, Tatiana Yu.; Goryacheva, Irina Yu. [Saratov State University (Russian Federation)

    2016-12-15

    Multifunctional silica gel with embedded silver nanoparticles (SiO{sub 2}–AgNP) is proposed for application as sorbent for solid-phase extraction (SPE) and simultaneously as substrate for surface-enhanced Raman spectroscopy (SERS) due to their high sorption properties and ability to enhance Raman signal (SERS-active sorbents). SiO{sub 2}–AgNP was synthesized via alkaline hydrolysis of tetraethyl orthosilicate with simultaneous reduction of silver ions to silver nanoparticles (AgNP) within the SiO{sub 2} bulk. Synthesis of AgNP directly to the SiO{sub 2} matrix enables to exclude any additional stabilizers for the nanoparticles that educes signal-to-noise ratio during SERS measurement. Apart from Raman spectroscopy, obtained sorbents were also characterized by scanning electron microscopy and UV-visible diffuse reflectance spectroscopy. The influence of AgNO{sub 3} concentration used during the SiO{sub 2}–AgNP synthesis on its gelling time, color, diffuse reflectance spectra, and enhancement of Raman signal was investigated. A Raman enhancement factor of SiO{sub 2}–AgNP with optimal composition was around 10{sup 5}. Finally, the sorbents were applied for SPE and subsequent SERS detection of model compounds (rhodamine 6G and folic acid). It was found that SPE enables to decrease detectable concentrations by two orders. Therefore, SPE combined with SERS has high potential for further analytical investigations.

  7. ANALISA DAYA SERAP SILIKA GEL BERBAHAN DASAR ABU SEKAM PADI

    Directory of Open Access Journals (Sweden)

    Hendriwan Fahmi

    2016-08-01

    Full Text Available Rice husk ash Silica Gel is aproduct which call be used in preventing the humidity by absorbing the water ion on the water andonthe air. This absorbing isbased onthe size, the composition and the total amount ofpolluter which contained on the Silica Gel. The purpose of making this silica gel is to seehow much thiskind of Silica Gel can absorb and compare it to the synthetic one,and also processing rise husk ashto be something useful, Ion water can be absorbed much more by using this natural silica gel if it is compared to the synthetic silica gel. This is because of its capable inabsorbing more –OHand O from water and air. Afterdoing a research with column method, silica gel was beingput in 50 ml water. Fromthis research, natural silica can absorb much more water (0.0010 gr/ml, 0.285 % water level ofweigh in comparing with synthetic one (0.008gr/ml with 0.248 %water level ofweight andsintering (0,007 gr/ml 0.253%water level and non-sintering silica gel contains 39.22 % weight of silica, 30.93 %weight of sintering silica gel, and 33.40 % of the synthetic. More silica and water level, means more total amount of absorbing. This silica gel application is considered with capability ofabsorbing andthe level of the water.

  8. 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...

  9. Space-filling polyhedral sorbents

    Energy Technology Data Exchange (ETDEWEB)

    Haaland, Peter

    2016-06-21

    Solid sorbents, systems, and methods for pumping, storage, and purification of gases are disclosed. They derive from the dynamics of porous and free convection for specific gas/sorbent combinations and use space filling polyhedral microliths with facial aplanarities to produce sorbent arrays with interpenetrating interstitial manifolds of voids.

  10. Silica gel modified with N-(3-propyl)-O-phenylenediamine: functionalization, metal sorption equilibrium studies and application to metal enrichment prior to determination by flame atomic absorption spectrometry.

    Science.gov (United States)

    Akl, Magda Ali Abd-elAziz; Kenawy, Ibraheim Mohamed; Lasheen, Rabab Ramadan

    2005-08-01

    The use of the chemically modified silica gel N-(3-propyl)-O-phenylenediamine (SiG-NPPDA) adsorbent, for the preconcentration and separation of trace heavy metals, was described. SiG-NPPDA sorbs quantitatively (90-100% recovery) trace amounts of nine heavy metals, viz., Cd(II), Zn(II), Fe(III), Cu(II), Pb(II), Mn(II), Cr(III), Co(II) and Ni(II) at pH 7-8. The sorption capacity varies from 350 to 450 micromol g(-1). Desorption was found to be quantitative with 1-2 M HNO3 or 0.05 M Na2EDTA. The distribution coefficient, Kd and the percentage concentration of the investigated metal ions on the adsorbent at equilibrium, C(M,eqm)% (Recovery, R%), were studied as a function of experimental parameters. The logarithmic values of the distribution coefficient, log Kd, ranges between 4.0 and 6.4. Some foreign ions caused little interference in the preconcentration and determination of the investigated nine metals by flame atomic absorption spectrometry (AAS). The adsorbent and its formed metal chelates were characterized by IR (absorbance and/or reflectance), potentiometric titrations and thermogravimetric analysis (TGA and DTG). The mode of chelation between the SiG-NPPDA adsorbent and the investigated metal ions is proposed to be due to the reaction of the investigated metal ions with the two nitrogen atoms of the SiG-NPPDA adsorbent. The present adsorbent coupled with flame AAS has been used to enrich and determine the nine metal ions in natural aqueous systems and in certified reference materials (RSD < or = 5%). The copper, iron, manganese and zinc present in some pharmaceutical vitamin samples were also preconcentrated on SiG-NPPDA adsorbent and determined by flame AAS (RSD < or = 4.2%). Nanogram concentrations (0.07-0.14 ng ml(-1)) of Cd(II), Zn(II), Fe(III), Pb(II), Cr(III), Mn(II), Cu(II), Co(II) and Ni(II) can be determined reliably with a preconcentration factor of 100.

  11. Synthesis and characterization of organically modified silica gel with 4-amino-5-(4-pyridyl)-4h-1 ,2,4-triazole-3-thiol (APTT); Sintese e caracterizacao da silica gel organofuncionalizada com 4-amino-5-(4-piridil)-4h-1,2,4-triazol-3-tiol (APTT)

    Energy Technology Data Exchange (ETDEWEB)

    Magossi, M.S.; Carmo, D.R. do, E-mail: maiaramagossi@gmail.com [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Ilha Solteira, SP (Brazil). Faculdade de Engenharia

    2014-07-01

    This work object the preparation and characterization of a silica gel (SG) organically with a triazole compound, 4-amino-5-(4-pyridyl)-4H-1,2,4-triazole-3- thiol (APTT). The prepared organofunctionalized material (SGAPTT) was preliminarily characterized by spectroscopic techniques such as: Spectroscopy in the Region of Infrared (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy X-ray (EDX). The vibrational spectrum (FTIR) showed characteristic bands of the starting materials, such as bands at ∼ 1120cm{sup -1} related to the asymmetric stretching Si-O-Si (νSi-O-Si) as well as the bands between 1350 and 1650 cm{sup -1} assigned vibrations and deformations of the ring APTT. The SGAPTT material was tested as support for adsorption of cupric ions in aqueous solution, ethanol and 42% ethanol. The maximum amount of copper (II) adsorbed (Nf {sup max.}) was 22.0 × 10{sup -5} mol g{sup -1}, 31.4 × 10-5 mol g-1 and 47.17 × 10{sup -5} mol g{sup -1} to aqueous media, 42% ethanol and 99% ethanol respectively. (author)

  12. Natural gels in the Yucca Mountain Area, Nevada, USA

    International Nuclear Information System (INIS)

    Levy, S.S.

    1991-01-01

    Relict gels at Yucca Mountain include pore- and fracture-fillings of silica and zeolite related to diagenetic and hydrothermal alternation of vitric tuffs. Water-rich free gels in fractures at Rainier Mesa consist of smectite with or without silica-rich gel fragments. Gels are being studied for their potential role in transport of radionuclides from a nuclear-waste repository

  13. PROCEEDINGS: MULTIPOLLUTANT SORBENT REACTIVITY ...

    Science.gov (United States)

    The report is a compilation of technical papers and visual aids presented by representatives of industry, academia, and government agencies at a workshop on multipollutant sorbent reactivity that was held at EPA's Environmental Research Center in Research Triangle Park, NC, on July 19-20, 1994. There were 16 technical presentations in three sessions, and a panel discussion between six research experts. The workshop was a forum for the exchange of ideas and information on the use of sorbents to control air emissions of acid gases (sulfur dioxide, nitrogen oxides, and hydrogen chloride); mercury and dioxins; and toxic metals, primarily from fossil fuel combustion. A secondary purpose for conducting the workshop was to help guide EPA's research planning activities. A general theme of the workshop was that a strategy of controlling many pollutants with a single system rather than systems to control individual pollutants should be a research goal. Some research needs cited were: hazardous air pollutant removal by flue gas desulfurization systems, dioxin formation and control, mercury control, waste minimization, impact of ash recycling on metals partitioning, impact of urea and sorbents on other pollutants, high temperature filtration, impact of coal cleaning on metals partitioning, and modeling dispersion of sorbents in flue gas. information

  14. Design of engineered sorbent barriers

    International Nuclear Information System (INIS)

    Jones, E.O.; Freeman, H.D.

    1988-08-01

    A sorbent barrier uses sorbent material such as activated carbon or natural zeolites to prevent the migration of radionuclides from a low-level waste site to the aquifer. The sorbent barrier retards the movement of radioactive contaminants, thereby providing time for the radionuclides to decay. Sorbent barriers can be a simple, effective, and inexpensive method for reducing the migration of radionuclides to the environment. Designing a sorbent barrier consists of using soil and sorbent material properties and site conditions as input to a model which will determine the necessary sorbent barrier thickness to meet contaminant limits. The paper will cover the following areas: techniques for measuring sorption properties of barrier materials and underlying soils, use of a radionuclide transport model to determine the required barrier thickness and performance under a variety of site conditions, and cost estimates for applying the barrier. 8 refs., 6 figs., 1 tab

  15. Design of engineered sorbent barriers

    International Nuclear Information System (INIS)

    Jones, E.O.; Freeman, H.D.

    1988-01-01

    A sorbent barrier uses sorbent material such as activated carbon or natural zeolites to prevent the migration of radionuclides from a low-level waste site to the aquifer. The sorbent barrier retards the movement of radioactive contaminants, thereby providing time for the radionuclides to decay. Sorbent barriers can be a simple, effective, and inexpensive method for reducing the migration of radionuclides to the environment. Designing a sorbent barrier consists of using soil and sorbent material properties and site conditions as input to a model which will determine the necessary sorbent barrier thickness to meet contaminant limits. The paper covers the following areas: techniques for measuring sorption properties of barrier materials and underlying soils, use of a radionuclide transport model to determine the required barrier thickness and performance under a variety of site conditions, and cost estimates for applying the barrier

  16. Ionic liquid-silica precursors via solvent-free sol-gel process and their application in epoxy-amine network: a theoretical/experimental study

    Czech Academy of Sciences Publication Activity Database

    Perchacz, Magdalena; Donato, R. K.; Seixas, L.; Zhigunov, Alexander; Konefal, Rafal; Serkis-Rodzen, Magdalena; Beneš, Hynek

    2017-01-01

    Roč. 9, č. 19 (2017), s. 16474-16487 ISSN 1944-8244 R&D Projects: GA ČR(CZ) GA17-08273S; GA MŠk(CZ) LO1507 Institutional support: RVO:61389013 Keywords : 3D POSS structures * epoxy-silica hybrid material * IL-silica precursor Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science Impact factor: 7.504, year: 2016

  17. New solid phase extractors for selective separation and preconcentration of mercury (II) based on silica gel immobilized aliphatic amines 2-thiophenecarboxaldehyde Schiff's bases

    International Nuclear Information System (INIS)

    Soliman, Ezzat M.; Saleh, Mohamed B.; Ahmed, Salwa A.

    2004-01-01

    2-Thiophenecarboxaldhyde is chemically bonded to silica gel surface immobilized monoamine, ethylenediamine and diethylenetriamine by a simple Schiff's base reaction to produce three new SP-extractors, phases (I-III). The selectivity properties of these phases toward Hg(II) uptake as well as eight other metal ions: Ca(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) were extensively studied and evaluated as a function of pH of metal ion solution and equilibrium shaking time by the batch equilibrium technique. The data obtained clearly indicate that the new SP-extractors have the highest affinity for retention of Hg(II) ion. Their Hg(II) uptake in mmol g -1 and distribution coefficient as log K d values are always higher than the uptake of any other metal ion along the range of pH used (pH 1.0-10.0). The uptake of Hg(II) using phase I was 2.0 mmol g -1 (log K d 6.6) at pH 1.0 and 2.0. 1.8 mmol g -1 (log K d 4.25), 1.6 mmol g -1 (log K d 3.90) and 1.08 mmol g -1 (log K d 3.37) at pH 3.0, 5.0 and 8.0, respectively. Selective separation of Hg(II) from the other eight coexisting metal ions under investigation was achieved successfully using phase I at pH 2.0 either under static or dynamic conditions. Hg(II) was completely retained while Ca(II), Co(II) and Cd(II) ions were not retained. Ni(II), Cu(II), Zn(II), Pb(II) and Fe(III) showed very low percentage retention values to be 0.74, 0.97, 3.5 and 6.3%, respectively. Moreover, the high recovery values (95.5 ± 0.5, 95.8 ± 0.5 and 99.0% ± 1.0) of percolating two liters of doubly distilled water, drinking tap water and Nile river water spiked with 5 ng/l of Hg(II) over 100 mg of phase I packed in a minicolumn and used as a thin layer enrichment bed demonstrate the accuracy and validity of the new SP-extractors for preconcentration of the ultratrace amount of spiked Hg(II) prior to the determination by borohydride generation atomic absorption spectrometry (AAS) with no matrix interference. The detection

  18. Utilization of Snail (Achatina fulica Shell Waste for Synthesis of Calcium Tartrate Tetrahydrate (CaC4H4O6.4H2O Single Crystals in Silica Gel

    Directory of Open Access Journals (Sweden)

    Imam Sakdi

    2012-01-01

    Full Text Available Snail (Achatina fulica shell waste is massively produced by many home industries in Indonesia, especially in East Java. The snail shell is known for high calcium; therefore it is potential to be used as calcium source of supernatant in the synthesis of piezoeletric material, such as single crystal of calcium tartrate tetrahydrate (CaTT. The aim of this research is to study the synthesis and characterization of CaTT or CaC4H4O6.4H2O from snail shell waste in silica gel. Supernatant solution of CaCl2 was prepared from CaO, which previously made by calcinating the shell at 1000°C, and then reacted with HCl 1,5M. Synthesis of CaTT was conducted in a single-tube reaction at room temperature in which silica gel was used as growth medium with gelling time of 10 days and growth time of 2 weeks. The pH of gel and CaCl2 concentration were varied, 3.00; 3.50; 4.00; 4.50; 5.00; and 0.27; 0.36; 0.45; 0.54 M respectively, in order to obtain optimum condition of the synthesis, which is indicated from crystal yields. The synthesized crystals were characterized by atomic adsorption spectrophotometry (AAS, infrared spectroscopy (IR and powder X-ray diffraction (XRD. Experimental data shows that optimum condition was obtained at pH of 3.50 and [CaCl2] of 0.45M with yield of 69.37%. The obtained single crystal has clear color and octahedral-like shape with size ranged between 4 – 9 mm. Analysis data by FTIR and powder XRD confirmed that the obtained crystal was CaTT single crystals with crystal system of orthorhombic.

  19. Polymer-silica hybrids for separation of CO2 and catalysis of organic reactions

    Science.gov (United States)

    Silva Mojica, Ernesto

    Porous materials comprising polymeric and inorganic segments have attracted interest from the scientific community due to their unique properties and functionalities. The physical and chemical characteristics of these materials can be effectively exploited for adsorption applications. This dissertation covers the experimental techniques for fabrication of poly(vinyl alcohol) (PVA) and silica (SiO2) porous supports, and their functionalization with polyamines for developing adsorbents with potential applications in separation of CO2 and catalysis of organic reactions. The supports were synthesized by processes involving (i) covalent cross-linking of PVA, (ii) hydrolysis and poly-condensation of silica precursors (i,e,. sol-gel synthesis), and formation of porous structures via (iii) direct templating and (iv) phase inversion techniques. Their physical structure was controlled by the proper combination of the preparation procedures, which resulted in micro-structured porous materials in the form of micro-particles, membranes, and pellets. Their adsorption characteristics were tailored by functionalization with polyethyleneimine (PEI), and their physicochemical properties were characterized by vibrational spectroscopy (FTIR, UV-vis), microscopy (SEM), calorimetry (TGA, DSC), and adsorption techniques (BET, step-switch adsorption). Spectroscopic investigations of the interfacial cross-linking reactions of PEI and PVA with glutaraldehyde (GA) revealed that PEI catalyzes the cross-linking reactions of PVA in absence of external acid catalysts. In-situ IR spectroscopy coupled with a focal plane array (FPA) image detector allowed the characterization of a gradient interface on a PEI/PVA composite membrane and the investigation of the cross-linking reactions as a function of time and position. The results served as a basis to postulate possible intermediates, and propose the reaction mechanisms. The formulation of amine-functionalized CO2 capture sorbents was based on the

  20. Novel nanoporous sorbent for solid-phase extraction in petroleum fingerprinting

    Science.gov (United States)

    Alayande, S. Oluwagbemiga; Hlengilizwe, Nyoni; Dare, E. Olugbenga; Msagati, Titus A. M.; Akinlabi, A. Kehinde; Aiyedun, P. O.

    2016-04-01

    Sample preparation is crucial in the analysis of petroleum and its derivatives. In this study, developing affordable sorbent for petroleum fingerprinting analysis using polymer waste such expanded polystyrene was explored. The potential of electrospun expanded polystyrene (EPS) as a sorbent for the solid-phase extraction (SPE) technique was investigated, and its efficiency was compared with commercial cartridges such as alumina, silica and alumina/silica hybrid commercial for petroleum fingerprinting analysis. The chromatograms showed that the packed electrospun EPS fibre demonstrated excellent properties for SPE applications relative to the hybrid cartridges.

  1. Sorbents for mercury removal from flue gas

    Energy Technology Data Exchange (ETDEWEB)

    Granite, Evan J.; Hargis, Richard A.; Pennline, Henry W.

    1998-01-01

    A review of the various promoters and sorbents examined for the removal of mercury from flue gas is presented. Commercial sorbent processes are described along with the chemistry of the various sorbent-mercury interactions. Novel sorbents for removing mercury from flue gas are suggested. Since activated carbons are expensive, alternate sorbents and/or improved activated carbons are needed. Because of their lower cost, sorbent development work can focus on base metal oxides and halides. Additionally, the long-term sequestration of the mercury on the sorbent needs to be addressed. Contacting methods between the flue gas and the sorbent also merit investigation.

  2. Fumed silica. Fumed silica

    Energy Technology Data Exchange (ETDEWEB)

    Sukawa, T.; Shirono, H. (Nippon Aerosil Co. Ltd., Tokyo (Japan))

    1991-10-18

    The fumed silica is explained in particulate superfineness, high purity, high dispersiveness and other remarkable characteristics, and wide application. The fumed silica, being presently produced, is 7 to 40nm in average primary particulate diameter and 50 to 380m{sup 2}/g in specific surface area. On the surface, there coexist hydrophilic silanol group (Si-OH) and hydrophobic siloxane group (Si-O-Si). There are many characteristics, mutually different between the fumed silica, made hydrophobic by the surface treatment, and untreated hydrophilic silica. The treated silica, if added to the liquid product, serves as agent to heighten the viscosity, prevent the sedimentation and disperse the particles. The highest effect is given to heighten the viscosity in a region of 4 to 9 in pH in water and alcohol. As filling agent to strengthen the elastomer and polymer, and powder product, it gives an effect to prevent the consolidation and improve the fluidity. As for its other applications, utilization is made of particulate superfineness, high purity, thermal insulation properties and adsorption characteristics. 2 to 3 patents are published for it as raw material of quartz glass. 38 refs., 16 figs., 4 tabs.

  3. Effects of crown ethers in nanocomposite silica-gel electrolytes on the performance of quasi-solid-state dye-sensitized solar cells

    KAUST Repository

    Huang, Kuan-Chieh; Vittal, R.; Ho, Kuo-Chuan

    2010-01-01

    I) and iodine (I2) in 3-methoxypropionitrile (MPN) solvent. Three types of CEs, 12-crown-4 (12-C-4), 15-crown-5 (15-C-5), and 18-crown-6 (18-C-6) were used as additives to the gel electrolytes. DSSCs containing CEs showed enhancements in solar

  4. High efficiency nanocomposite sorbents for CO2 capture based on amine-functionalized mesoporous capsules

    KAUST Repository

    Qi, Genggeng; Wang, Yanbing; Estevez, Luis; Duan, Xiaonan; Anako, Nkechi; Park, Ah-Hyung Alissa; Li, Wen; Jones, Christopher W.; Giannelis, Emmanuel P.

    2011-01-01

    A novel high efficiency nanocomposite sorbent for CO2 capture has been developed based on oligomeric amine (polyethylenimine, PEI, and tetraethylenepentamine, TEPA) functionalized mesoporous silica capsules. The newly synthesized sorbents exhibit extraordinary capture capacity up to 7.9 mmol g-1 under simulated flue gas conditions (pre-humidified 10% CO 2). The CO2 capture kinetics were found to be fast and reached 90% of the total capacities within the first few minutes. The effects of the mesoporous capsule features such as particle size and shell thickness on CO2 capture capacity were investigated. Larger particle size, higher interior void volume and thinner mesoporous shell thickness all improved the CO2 capacity of the sorbents. PEI impregnated sorbents showed good reversibility and stability during cyclic adsorption-regeneration tests (50 cycles). © 2011 The Royal Society of Chemistry.

  5. Sol-Gel Glasses

    Science.gov (United States)

    Mukherjee, S. P.

    1985-01-01

    Multicomponent homogeneous, ultrapure noncrystalline gels/gel derived glasses are promising batch materials for the containerless glass melting experiments in microgravity. Hence, ultrapure, homogeneous gel precursors could be used to: (1) investigate the effect of the container induced nucleation on the glass forming ability of marginally glass forming compositions; and (2) investigate the influence of gravity on the phase separation and coarsening behavior of gel derived glasses in the liquid-liquid immiscibility zone of the nonsilicate systems having a high density phase. The structure and crystallization behavior of gels in the SiO2-GeO2 as a function of gel chemistry and thermal treatment were investigated. As are the chemical principles involved in the distribution of a second network former in silica gel matrix being investigated. The procedures for synthesizing noncrystalline gels/gel-monoliths in the SiO2-GeO2, GeO2-PbO systems were developed. Preliminary investigations on the levitation and thermal treatment of germania silicate gel-monoliths in the Pressure Facility Acoustic Levitator were done.

  6. Potential of sub- and supercritical CO_2 reaction media for sol-gel deposition of silica-based molecular sieve membranes

    International Nuclear Information System (INIS)

    Durand, Veronique; Duchateau, Maxime; Drobek, Martin; Julbe, Anne; Hertz, Audrey; Ruiz, Jean-Christophe; Sarrade, Stephane

    2014-01-01

    A new eco-friendly method recently developed in our group has been further investigated for the preparation of gas selective silica-based molecular sieve membranes on/in macroporous tubular ceramic supports without any intermediate layer. The synthesis protocol under sub- and supercritical conditions was based on an 'On-Stream Supercritical Fluid Deposition method' (OS-SFD) applying supercritical carbon dioxide (scCO_2) as an attractive 'green' solvent with easily adjustable properties enabling a controlled solubilisation/reaction of precursors and their transport to the ceramic support. Parameters influencing the final membrane characteristics such as permeates flow rate, calcination treatment and deposition steps have been examined for a selected reaction mixture, transmembrane pressure and defined deposition temperatures. On-line monitoring of the membrane formation process (deposition signature curve) was used in this process. Membrane characteristics are discussed in correlation with their gas permeation properties. The optimized crack-free silica membranes prepared at 50 C have a compact microstructure but a thermal stability limited to 400 C. A second deposition run allowed a recovery of the molecular sieving behaviour with a thermally activated transport for He up to 350 C. These promising results demonstrate the potential of this novel method for the preparation of uniform molecular sieve membranes deposited directly on macroporous supports with virtually zero waste. (authors)

  7. Sorbents based on xerogels of zirconium, aluminum and manganese oxyhydroxides

    Directory of Open Access Journals (Sweden)

    R.V. Smotraiev

    2016-05-01

    Full Text Available The actual problem of water supply in the world and in Ukraine, in particular, is a high level of pollution in water resources and an insufficient level of drinking water purification. With industrial wastewater, a significant amount of pollutants falls into water bodies, including suspended particles, sulfates, iron compounds, heavy metals, etc. Aim: The aim of this work is to determine the impact of aluminum and manganese ions additives on surface and sorption properties of zirconium oxyhydroxide based sorbents during their production process. Materials and Methods: The sorbents based on xerogels of zirconium, aluminum and manganese oxyhydroxides were prepared by sol-gel method during the hydrolysis of metal chlorides (zirconium oxychloride ZrOCl2, aluminum chloride AlCl3 and manganese chloride MnCl2 with carbamide. Results: The surface and sorption properties of sorbents based on xerogels of zirconium, aluminum and manganese oxyhydroxides were investigated. X-ray amorphous structure and evolved hydroxyl-hydrate cover mainly characterize the obtained xerogels. The composite sorbents based on xerogels of zirconium oxyhydroxide doped with aluminum oxyhydroxide (aS = 537 m2/g and manganese oxyhydroxide (aS = 356 m2/g have more developed specific surface area than single-component xerogels of zirconium oxyhydroxide (aS = 236 m2/g and aluminum oxyhydroxide (aS = 327 m2/g. The sorbent based on the xerogel of zirconium and manganese oxyhydroxides have the maximum SO42--ions sorption capacity. It absorbs 1.5 times more SO42–-ions than the industrial anion exchanger AN-221. The sorbents based on xerogels of zirconium oxyhydroxide has the sorption capacity of Fe3+-ions that is 1.5…2 times greater than the capacity of the industrial cation exchanger KU-2-8. The Na+-ions absorption capacity is 1.47…1.56 mmol/g for each sorbent. Conclusions: Based on these data it can be concluded that the proposed method is effective for sorbents production based on

  8. Characteristic of New Solid-Phase Extraction Sorbent: Activated Carbon Prepared from Rice Husks under Base Treated Condition

    Directory of Open Access Journals (Sweden)

    Afrida Kurnia Putri

    2012-10-01

    Full Text Available A characterization of activated carbon (ACs prepared from rice husks (RHs under base treated condition as a new sorbent for solid-phase extraction (SPE to extract 4-nonylphenol isomers (4-NPs in water samples has been done. The ACs prepared from RHs usually exhibits low specific surface area due to its high ash content, but in case of its application for SPE, there are other factors need to be considered, such as the existence of functional groups inside the sorbent, that can enhance interaction of non-polar sorbent with analyte in the water matrices. In this case, silanol groups from ash content may affect the extraction efficiency for 4-NPs. The ACs made from RHs were chemically impregnated with ZnCl2 and carbonized at 800oC. To investigate the role of silica, three types of ACs were prepared, i.e., untreated ACs (AC–Si, contain silica, base treated ACs (AC–B–Si, remain some silica inside, and ACs made by base treated RHs (AC–B, no silica, the surface area obtained from these treatments were 1352 m2/g, 1666 m2/g, and 1712m2/g respectively.  ACs made by base treatment has the highest surface area (related to BET, which indicat that silica removal process promotes the formation of open pore system on ACs and enhances the surface area of ACs. However, extraction efficiency measured by GC-MS in SPE process showed the reversal trends (i.e., AC–Si= 32.08%, AC–B–Si= 82.63%, AC–B=51.78%, among them the AC–B–Si sorbent reveal the best performance in SPE process. It is indicated that although silica usually exhibits low specific surface area, but control presence of silica as a polar functional group has a positive influence in the interaction between non-polar sorbent and 4-NPs.

  9. Synthesis and Gas Transport Properties of Hyperbranched Polyimide–Silica Hybrid/Composite Membranes

    Directory of Open Access Journals (Sweden)

    Masako Miki

    2013-12-01

    Full Text Available Hyperbranched polyimide–silica hybrids (HBPI–silica HBDs and hyperbranched polyimide–silica composites (HBPI–silica CPTs were prepared, and their general and gas transport properties were investigated to clarify the effect of silica sources and preparation methods. HBPI–silica HBDs and HBPI–silica CPTs were synthesized by two-step polymerization of A2 + B3 monomer system via polyamic acid as precursor, followed by hybridizing or blending silica sources. Silica components were incorporated by the sol-gel reaction with tetramethoxysilane (TMOS or the addition of colloidal silica. In HBPI-silica HBDs, the aggregation of silica components is controlled because of the high affinity of HBPI and silica caused by the formation of covalent bonds between HBPI and silica. Consequently, HBPI-silica HBDs had good film formability, transparency, and mechanical properties compared with HBPI-silica CPTs. HBPI-silica HBD and CPT membranes prepared via the sol-gel reaction with TMOS showed specific gas permeabilities and permselectivities for CO2/CH4 separation, that is, both CO2 permeability and CO2/CH4 selectivity increased with increasing silica content. This result suggests that gas transport can occur through a molecular sieving effect of the porous silica network derived from the sol-gel reaction and/or through the narrow interfacial region between the silica networks and the organic matrix.

  10. Novel sorbents for environmental remediation

    Science.gov (United States)

    Manariotis, Ioannis D.; Karapanagioti, Hrissi K.; Werner, David

    2014-05-01

    Nowadays, one of the major environmental problems is the pollution of aquatic systems and soil by persistent pollutants. Persistent pollutants have been found widespread in sediments, surface waters, and drinking water supplies. The removal of pollutants can be accomplished prior to their discharge to receiving bodies or by immobilizing them onto soil. Sorption is the most commonly applied process, and activated carbons have been widely used. Rapid progress in nanotechnology and a new focus on biomass-based instead of non-renewable starting materials have produced a wide range of novel engineered sorbents including biosorbents, biochars, carbon-based nanoparticles, bio-nano hybrid materials, and iron-impregnated activated carbons. Sorbent materials have been used in environmental remediation processes and especially in agricultural soil, sediments and contaminated soil, water treatment, and industrial wastewater treatment. Furthermore, sorbents may enhance the synergistic action of other processes, such as volatilization and biodegradation. Novel sorbents have been employed for the removal or immobilization of persistent pollutants such as and include heavy metals (As, Cr, Cu, Pb, Cd, and Hg), halogenated organic compounds, endocrine disrupting chemicals, metalloids and non-metallic elements, and other organic pollutants. The development and evaluation of novel sorbents requires a multidisciplinary approach encompassing environmental, nanotechnology, physical, analytical, and surface chemistry. The necessary evaluations encompass not only the efficiency of these materials to remove pollutants from surface waters and groundwater, industrial wastewater, polluted soils and sediments, etc., but also the potential side-effects of their environmental applications. The aim of this work is to present the results of the use of biochar and impregnated carbon sorbents for the removal of organic pollutants and metals. Furthermore, the new findings from the forthcoming session

  11. Flame retardant and hydrophobic properties of novel sol-gel derived phytic acid/silica hybrid organic-inorganic coatings for silk fabric

    Science.gov (United States)

    Cheng, Xian-Wei; Liang, Cheng-Xi; Guan, Jin-Ping; Yang, Xu-Hong; Tang, Ren-Cheng

    2018-01-01

    In this work, a novel phosphorus-rich hybrid organic-inorganic silica coating for improving the flame retardancy of silk fabric was prepared using naturally occurring phytic acid as phosphorus precursor and catalyst for the hydrolysis of tetraethoxysilane. In addition, three silane coupling agents, namely 3-aminopropyldimethoxymethylsilane, 3-chloropropyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane, were added in the hybrid sol as cross-linkers with the aim of developing hydrophobic coatings and improving the washing durability of the treated silk fabric. The condensation degree of the hybrid sol was characterized by solid-state 29Si nuclear magnetic resonance spectroscopy. The flammability and thermal degradation properties of the treated silk fabrics were determined in terms of limiting oxygen index, vertical burning, pyrolysis combustion flow calorimetry and thermogravimetric analyses. The surface morphology and hydrophobicity of the treated silk fabrics were evaluated by scanning electron microscopy, atomic force microscopy and water contact angle tests. The flammability tests revealed that the silicon sol could endow silk fabric with excellent flame retardancy when doped with phytic acid, and the treated silk fabrics self-extinguished immediately when the ignition source was removed. The silk fabrics treated with the modified hybrid sols exhibited hydrophobic surface and also better durability to washing.

  12. Micelle swelling agent derived cavities for increasing hydrophobic organic compound removal efficiency by mesoporous micelle@silica hybrid materials

    KAUST Repository

    Shi, Yifeng; Li, Bin; Wang, Peng; Dua, Rubal; Zhao, Dongyuan

    2012-01-01

    Mesoporous micelle@silica hybrid materials with 2D hexagonal mesostructures were synthesized as reusable sorbents for hydrophobic organic compounds (HOCs) removal by a facile one-step aqueous solution synthesis using 3-(trimethoxysily)propyl

  13. Solid-phase extraction of copper(II) in water and food samples using silica gel modified with bis(3-aminopropyl)amine and determination by flame atomic absorption spectrometry.

    Science.gov (United States)

    Cagirdi, Duygu; Altundag, Hüseyin; Imamoglu, Mustafa; Tuzen, Mustafa

    2014-01-01

    A simple and selective separation and preconcentration method was developed for the determination of Cu(ll) ions. This method is based on adsorption of Cu(ll) ions from aqueous solution on a bis(3-aminopropyl)amine modified silica gel column and flame atomic absorption spectrometric determination after desorption. Various analytical parameters such as pH, type of eluent solution and its volume, flow rate of sample and eluent, and sample volume were optimized. Effects of some cation, anion, and transition metal ions on the recoveries of Cu(ll) ions were also investigated. Cu(ll) ions were quantitatively recovered at pH 6; 5.0 mL of 2 M HCI was used as the eluent. The preconcentration factor was found to be 150. The LOD was 0.12 microg/L for Cu(ll). The accuracy of the method was confirmed by analysis of Tea Leaves (INCT-TL-1) and Fish Protein (DORM-3) certified reference materials. The optimized method was applied to various water and food samples for the determination of Cu(ll).

  14. Preparative separation of α- and β-santalenes and (Z)-α- and (Z)-β-santalols using silver nitrate-impregnated silica gel medium pressure liquid chromatography and analysis of sandalwood oil.

    Science.gov (United States)

    Daramwar, Pankaj P; Srivastava, Prabhakar Lal; Priyadarshini, Balaraman; Thulasiram, Hirekodathakallu V

    2012-10-07

    The major sesquiterpene constituents of East-Indian sandalwood oil (Z)-α- and (Z)-β-santalols have shown to be responsible for most of the biological activities and organoleptic properties of sandalwood oil. The work reported here describes the strategic use of medium pressure liquid chromatography (MPLC) for the separation of both α- and β-santalenes and (Z)-α- and (Z)-β-santalols. Silver nitrate impregnated silica gel was used as the stationary phase in MPLC for quantitative separation of α- and β-santalenes and (Z)-α- and (Z)-β-santalols with mobile phases hexane and dichloromethane, respectively. The purities of α-santalene and (Z)-α-santalol obtained were >96%; however, β-santalene and (Z)-β-santalol were obtained with their respective inseparable epi-isomers. Limits of quantification (LoQ) relative to the FID detector were measured for important sesquiterpene alcohols of heartwood oil of S. album using serial dilutions of the standard stock solutions and demonstrated that the quality of the commercial sandalwood oil can be assessed for the content of individual sesquiterpene alcohols regulated by Australian Standard (AS2112-2003), International Organization for Standardization ISO 3518:2002 (E) and European Union (E. U.).

  15. Resolution and isolation of enantiomers of (±)-isoxsuprine using thin silica gel layers impregnated with L-glutamic acid, comparison of separation of its diastereomers prepared with chiral derivatizing reagents having L-amino acids as chiral auxiliaries.

    Science.gov (United States)

    Bhushan, Ravi; Nagar, Hariom

    2015-03-01

    Thin silica gel layers impregnated with optically pure l-glutamic acid were used for direct resolution of enantiomers of (±)-isoxsuprine in their native form. Three chiral derivatizing reagents, based on DFDNB moiety, were synthesized having l-alanine, l-valine and S-benzyl-l-cysteine as chiral auxiliaries. These were used to prepare diastereomers under microwave irradiation and conventional heating. The diastereomers were separated by reversed-phase high-performance liquid chromatography on a C18 column with detection at 340 nm using gradient elution with mobile phase containing aqueous trifluoroacetic acid and acetonitrile in different compositions and by thin-layer chromatography (TLC) on reversed phase (RP) C18 plates. Diastereomers prepared with enantiomerically pure (+)-isoxsuprine were used as standards for the determination of the elution order of diastereomers of (±)-isoxsuprine. The elution order in the experimental study of RP-TLC and RP-HPLC supported the developed optimized structures of diastereomers based on density functional theory. The limit of detection was 0.1-0.09 µg/mL in TLC while it was in the range of 22-23 pg/mL in HPLC and 11-13 ng/mL in RP-TLC for each enantiomer. The conditions of derivatization and chromatographic separation were optimized. The method was validated for accuracy, precision, limit of detection and limit of quantification. Copyright © 2014 John Wiley & Sons, Ltd.

  16. Reactivity improvement of Ca(OH)2 sorbent using diatomaceous earth (DE) from Aceh Province

    Science.gov (United States)

    Mariana, M.; Mahidin, M.; Mulana, F.; Agam, T.; Hafdiansyah, F.

    2018-04-01

    In this study, the diatomaceous earth (DE) from Aceh Province was used to increase the reactivity of Ca(OH)2sorbent. The high silica (SiO2) content of about 97% in the diatomaceous earth allows the increasing reactivity of Ca(OH)2sorbent by forming calcium silicate hydrate (CSH). The CSH improved the porosity characteristic of the sorbent. The improvement process was performed by mixing Ca(OH)2sorbent, diatomaceous earth and water in a beaker glass at the Ca(OH)2/DE weight ratio of 1:10 for 2 hand then dried at 120 °C for 24 h. The dried sorbent was calcined at 500 °C and 800 °C for 2 h. The activated sorbent was characterized using Scanning Electron Microscopy (SEM) for the morphological properties; X- Ray Diffraction (XRD) for the materials characteristics. The adsorption capacity of thesorbent was tested by methylene blue adsorption. The results showed that the Ca(OH)2/DEsorbent had a higher porosity than the Ca(OH)2 adsorbent.The results also showed that Ca(OH)2/DE which was calcined at higher temperature of 800 °C had a higher adsorption capacity compared to Ca(OH)2/DE which was calcined at lower temperature of 500 °C.

  17. Release of iodine radionuclides from gas media in a system of selective block sorbents

    International Nuclear Information System (INIS)

    Moskvin, L.N.; Miroshnikov, V.S.; Mel'nikov, V.A.; Chetverikov, V.V.

    1979-01-01

    A scheme of extracting iodine radionuclides from gas flows in a system of selective sorbents has been developed. The method provides separation of three forms of iodine: the aerosol component, the elementary iodine and organic-iodine compounds. Aerosols are trapped by a mechanical filter made of porous polytetrafluoroethylene with pores of no more than 1 μm. Silver-based sorbents for the elementary iodine are made by sintering the granular polytetrafluoroethylene (the size of granules is 0.1-0.5 mm) with of finely dispersed solver (5% mass). Organic iodine compounds are extracted by a silica sorbent impregnated with silver nitrate. The efficiency of sorbents was tested in gas flows with a known content of 131 I in the form of elementary iodine and methyl iodide. The results of experiments show that the efficiency of sorption of elementary iodine by a metallic-silver sorbent and of methyl iodide by a SiO 2 /AgNO 3 sorbent constitutes no less than 99% at a flow rate of up to 200 l/h. The iodine has been extracted at a flow rate of 100 l/h during 100 hours and for that time the efficiency of the iodine sorbtion has not changed. The suggested variant of extracting iodine radionuclides from gaseous media can be used both for fast control of iodine content in gas blowoffs and for researches aimed at studying the distribution of iodine forms in steam-and-gas media depending on nuclear plant operating conditions

  18. Synthesis of sol–gel silica particles in reverse micelles with mixed-solvent polar cores: tailoring nanoreactor structure and properties

    Energy Technology Data Exchange (ETDEWEB)

    Bürglová, Kristýna; Hlaváč, Jan [Institute of Molecular and Translational Medicine, Faculty of Medicine and Dentistry (Czech Republic); Bartlett, John R., E-mail: jbartlett@usc.edu.au [University of the Sunshine Coast, Faculty of Science, Health, Education and Engineering (Australia)

    2015-07-15

    In this paper, we describe a new approach for producing metal oxide nano- and microparticles via sol–gel processing in confined media (sodium bis(2-ethylhexyl)sulfosuccinate reverse micelles), in which the chemical and physical properties of the polar aqueous core of the reverse micelles are modulated by the inclusion of a second polar co-solvent. The co-solvents were selected for their capacity to solubilise compounds with low water solubility and included dimethylsulfoxide, dimethylformamide, ethylene glycol, n-propanol, dimethylacetamide and N-methylpyrrolidone. A broad range of processing conditions across the sodium bis(2-ethylhexyl)sulfosuccinate/cyclohexane/water phase diagram were identified that are suitable for preparing particles with dimensions <50 to >500 nm. In contrast, only a relatively narrow range of processing conditions were suitable for preparing such particles in the absence of the co-solvents, highlighting the role of the co-solvent in modulating the properties of the polar core of the reverse micelles. A mechanism is proposed that links the interactions between the various reactive sites on the polar head group of the surfactant and the co-solvent to the nucleation and growth of the particles.

  19. Antimony (V) oxide adsorbed on a silica-zirconia mixed oxide obtained by the sol-gel processing method: preparation and acid properties

    International Nuclear Information System (INIS)

    Zaitseva, Galina; Gushikem, Yoshitaka

    2002-01-01

    The preparation, degree of dispersion, thermal stability and Lewis and Broensted acidity of antimony (V) oxide adsorbed on Si O 2 /Zr O 2 mixed oxide, previously prepared by the sol-gel processing method, are described herein. The samples Si O 2 /Zr O 2 /Sb 2 O 5 , with compositions (in wt %): (a) Zr= 8.1 and Sb= 6.3; (b) Zr= 14.9 and Sb= 11.4, were prepared. Scanning electron microscopy images connected to a X-ray energy dispersive spectrometer showed that both metals, Zr and Sb, were highly dispersed in the matrices. The X-ray diffraction patterns of Si O 2 /Zr O 2 /Sb 2 O 5 heated at different temperatures showed that, up to 1023 K, the matrix was amorphous. At 1273 K a crystalline phase of Zr O 2 (baddeleyite) was observed and raising the temperature to 1573 K, crystalline phases of Si O 2 (cristobalite) and presumably of Zr O 2 /Sb 2 O 5 were observed. Using pyridine as a molecular probe, Broensted acid sites on the Si O 2 /Zr O 2 /Sb 2 O 5 matrix, heat treated up to 523 K, were shown to be very stable. (author)

  20. Antimony (V Oxide Adsorbed on a Silica-Zirconia Mixed Oxide Obtained by the Sol-Gel Processing Method: Preparation and Acid Properties

    Directory of Open Access Journals (Sweden)

    Zaitseva Galina

    2002-01-01

    Full Text Available The preparation, degree of dispersion, thermal stability and Lewis and Brphinsted acidity of antimony (V oxide adsorbed on SiO2/ZrO2 mixed oxide, previously prepared by the sol-gel processing method, are described herein. The samples SiO2/ZrO2/Sb2O5, with compositions (in wt %: (a Zr= 8.1 and Sb= 6.3; (b Zr= 14.9 and Sb= 11.4, were prepared. Scanning electron microscopy images connected to a X-ray energy dispersive spectrometer showed that both metals, Zr and Sb, were highly dispersed in the matrices. The X-ray diffraction patterns of SiO2/ZrO2/Sb2O5 heated at different temperatures showed that, up to 1023 K, the matrix was amorphous. At 1273 K a crystalline phase of ZrO2 (baddeleyite was observed and raising the temperature to 1573 K, crystalline phases of SiO2 (cristobalite and presumably of ZrO2/Sb2O5 were observed. Using pyridine as a molecular probe, Brphinsted acid sites on the SiO2/ZrO2/Sb2O5 matrix, heat treated up to 523 K, were shown to be very stable.

  1. Preparation and characterization of rice hull silica products

    International Nuclear Information System (INIS)

    Quirit, Leni L.; Llaguno, Elma C.; Pagdanganan, Fernando C.; Hernandez, Karen N.

    2008-01-01

    Rice hull is an abundant agricultural waste material which could be a renewable energy source when combusted. The combustion residue (called rice hull ash or RHA) contains a significant amount (20% of the hull) of potentially high grade silica. Silica gels prepared from rice hull were found to have properties comparable to two commercial desiccant silica gels (Blue Merck and FNG-A) in terms of chemical and amorphous structure, surface area, desiccant characteristics, microstructure and heats of adsorption. These properties were determined from water vapor adsorption measurements, electron microscopy, and from infrared and x-ray diffraction spectra. The acid treated rice hull gels were found to have fewer elemental impurities detected by qualitative x-ray fluorescence, compared to the commercial gels. Thermogravimetric analysis (TGA) data showed that this technique can also be used to indirectly compare impurity levels in the samples, in terms of the amorphous to crystalline phase transition. Using an improved acid treatment method, a silica gel sample was prepared from rice hull and compared to three commercial chromatographic silica gels using quantitative elemental x-ray fluorescence analysis. Elemental levels in the rice hull gel were within the range of levels or close to the detection limits of corresponding elements in the chromatographic gels. Water vapor adsorption, x-ray diffraction, infrared spectroscopy and scanning electron microscopy showed that the rice hull gel was similar to the commercial chromatographic silica gel Davison 12. Zeolites are crystalline aluminosilicates used as molecular sieves for purification and catalytic purposes. Zeolites X and Y were synthesized from rice hull silica gel and aluminum hydroxide. For comparison, controls were synthesized from commercial silica gel. The samples and controls exhibited characteristics infrared peaks corresponding to the vibrations of the TO 4 (T=Si, Al) of the zeolite framework. The x

  2. Gel electrophoresis of inorganic cations

    International Nuclear Information System (INIS)

    Schoenhofer, F.; Grass, F.

    1978-01-01

    In order to be able to separate the largest possible amounts of substance, polyacryl amide gel (PAA) and silica gel are used as carrier for the electrophoresis. Milligramme quantities can easily be separated on PAA gel plates. Electrophoretic ion focussing considerably improves it. Separations of Sr/Y and lanthanoids were carried out. The behaviour of the readily soluble complexing agent acids on silica gel thin layers was minutely investigated and an interpretation of the focussing effect was derived. The conditions for separating radionuclides were optimized. A further improved separation can be achieved by a time sequence combination of normal electrophoresis and ion focussing. Selective isolation methods are advantageous to determine radionuclide traces in environmental samples. The selective adsorption on preformed deposits was transferred to electrophoresis. After pre-investigations on silica gel layers, strontium and barium could also be retained on PAA gel and radium on strontium sulphate in PAA, whereas the disturbing calcium can easily pass through. Cesium can also be retained by prussian blue in the electrophoresis. (orig.) [de

  3. Optimizing the Electron-Withdrawing Character on Benzenesulfonyl Moiety Attached to a Glyco-Conjugate to Impart Sensitive and Selective Sensing of Cyanide in HEPES Buffer and on Cellulose Paper and Silica Gel Strips.

    Science.gov (United States)

    Areti, Sivaiah; Bandaru, Sateesh; Yarramala, Deepthi S; Rao, Chebrolu Pulla

    2015-12-15

    Dansyl-derivatized, triazole-linked, glucopyranosyl conjugates, (5F)LOH, (2F)LOH, (1F)LOH, and (0F)LOH were synthesized and characterized. While the (5F)LOH acts as a molecular probe for CN(-), (2F)LOH, (1F)LOH, and (0F)LOH acts as control molecules. The reactivity of CN(-) toward (5F)LOH has been elicited through the changes observed in NMR, ESI MS, emission, and absorption spectroscopy. The conjugate (5F)LOH releases a fluorescent product upon reaction by CN(-) in aqueous acetonitrile medium by exhibiting an ∼125-fold fluorescence enhancement even in the presence of other anions. Fluorescence switch-on behavior has been clearly demonstrated on the basis of the nucleophilic substitution reaction of CN(-) on (5F)LOH. A minimum detection limit of (2.3 ± 0.3) × 10(-7) M (6 ± 1 ppb) was shown by (5F)LOH for CN(-) in solution. All the other anions studied showed no change in the fluorescence emission. The utility of (5F)LOH has been demonstrated by showing its reactivity toward CN(-) on a thin layer of silica gel as well as on Whatman No. 1 cellulose filter paper strips. The role of glucose moiety and the penta-fluorobenzenesulfonyl reactive center present in (5F)LOH in the selectivity of CN(-) over other anions has been demonstrated by fluorescence, absorption and thermodynamics study. Similar studies carried out with the control molecules showed no selectivity for CN(-). The mechanistic aspects of the reactivity of CN(-) toward (5F)LOH were supported by DFT computational study.

  4. Silica chemically bonded N-propyl kriptofix 21 and 22 with immobilized palladium nanoparticles for solid phase extraction and preconcentration of some metal ions

    Energy Technology Data Exchange (ETDEWEB)

    Ghaedi, Mehrorang, E-mail: m_ghaedi@mail.yu.ac.ir [Chemistry Department, Yasouj University, Yasouj, 75914-353 (Iran, Islamic Republic of); Niknam, Khodabakhsh, E-mail: niknam@pgu.ac.ir [Chemistry Department, Faculty of Sciences, Persian Gulf University, Bushehr, 75169 (Iran, Islamic Republic of); Zamani, Saeed; Abasi Larki, Habib [Chemistry Department, Islamic Azad University, Omidiyeh Branch, Omidiyeh (Iran, Islamic Republic of); Roosta, Mostafa [Chemistry Department, Yasouj University, Yasouj, 75914-353 (Iran, Islamic Republic of); Soylak, Mustafa [Chemistry Department, University of Erciyes, 38039 Kayseri (Turkey)

    2013-08-01

    Silica gel chemically bonded N-propyl kriptofix 21 (SBNPK 21) and N-propyl kriptofix 22 (SBNPK 22) and subsequently immobilized with palladium nanoparticles (PNP-SBNPK 21 and PNP-SBNPK 22) to produce two new complexing lipophilic materials. Then these novel sorbents were applied for the enrichment of some metal ions and their subsequent determination by flame atomic absorption spectroscopy (FAAS). The influences of the variables including pH, amount of solid phase, sample flow rate, eluent conditions and sample volume on the metal ion recoveries were investigated. The detection limit of proposed method was in the interval 2.1–2.3 and 1.7–2.8 ng mL{sup −1} for PNP-SBNPK 21 and PNP-SBNPK 22 respectively, while the preconcentration factor was 80 for two sorbents. The relative standard deviations of recoveries were between 1.23–1.31 and 1.28–1.49 for PNP-SBNPK 21 and PNP-SBNPK 22 respectively. The method has high sorption-preconcentration efficiency even in the presence of various interfering ions. Due to the reasonable selectivity of proposed method, the relative standard deviation of recoveries of all understudied metal ions in some complicated matrices was less than 3.0%. Highlights: • Highly selective sorbents for solid phase extraction were synthesized. • The method has been successfully applied for the determination of trace metals ions. • Excellent properties of the sorbent have been illustrated in detail.

  5. Using colloidal silica as isolator, diverter and blocking agent for subsurface geological applications

    Science.gov (United States)

    Bourcier, William L.; Roberts, Sarah K.; Roberts, Jeffery J.; Ezzedine, Souheil M.; Hunt, Jonathan D.

    2018-03-06

    A system for blocking fast flow paths in geological formations includes preparing a solution of colloidal silica having a nonviscous phase and a solid gel phase. The solution of colloidal silica is injected into the geological formations while the solution of colloidal silica is in the nonviscous phase. The solution of colloidal silica is directed into the fast flow paths and reaches the solid gel phase in the fast flow paths thereby blocking flow of fluid in the fast paths.

  6. Comprehensive Study of the Impact of Steam on Polyethyleneimine on Silica for CO2 Capture

    Energy Technology Data Exchange (ETDEWEB)

    Hammache, Sonia; Hoffman, James S.; Gray, McMahan L.; Fauth, Daniel J.; Howard, Bret H.; Pennline, Henry W.

    2013-11-21

    An amine sorbent, prepared by impregnation of polyethyleneimine on silica, was tested for steam stability. The stability of the sorbent was investigated in a fixed bed reactor using multiple steam cycles of 90 vol % H2O/He at 105 °C, and the gas effluent was monitored with a mass spectrometer. CO2 uptake of sorbent was found to decrease with repeated exposure to steam. Characterization of the spent sorbent using N2 physisorption, SEM, and thermogravimetric analysis (TGA) showed that the decrease in CO2 loading can possibly be attributed to a reagglomeration of the amine in the pores of the silica. No support effect was found in this study. The commercial SiO2 used, Cariact G10, was found to be stable under the conditions used. While it was found that subjecting the sorbent to several steam cycles decreased its CO2 uptake, a continuous exposure of the sorbent to steam did not have a significant performance impact. Finally, a silanated sorbent, consisting of a mixture of PEI and aminopropyl-triethoxysilane on SiO2 support, was also investigated for steam stability. Similarly to the nonsilanated sorbent, the CO2 loading of this sorbent decreased upon steam exposure, although a mechanism for this change has not been postulated at this time.

  7. Polymeric supported sorbents for decreasing hazardous metal ions content in wet process phosphoric acid

    International Nuclear Information System (INIS)

    El-Zahhar, A.A.; El-Naggar, H.A.; Ahmed, M.

    2005-01-01

    Procedure for preparation of polymeric supported silica, and their usage for decreasing hazardous metal ion content in wet process phosphoric acid was developed. The procedure is based firstly on extraction silica from rice straw by alkaline treatment , secondly supporting the produced silica on binding polyacrylonitrile (PAN). The produced polymer based sorbent was used for decreasing hazardous metal ions (especially iron) present as inorganic impurities in crud Egyptian phosphoric acid (green acid). Different factors affecting the sorption equilibrium ( contact time, temperature , sorbent mass and batch factor ) were studied. Studying the sorption isotherm revealed that the adsorption data could favorably fit the Langmuir adsorption isotherm. In the dynamic study , the sorption capacity at (Cξ/Cο = 50%) was found to be 28.5 mg/g and the loaded column could be regenerated using 50ml of 0.15 M HNO 3 . The regenerated column could undergo sorption regeneration cycles up to four cycles without significant decrease in the sorption capacity , weight loss or change in the physical properties of the sorbent

  8. High capacity carbon dioxide sorbent

    Science.gov (United States)

    Dietz, Steven Dean; Alptekin, Gokhan; Jayaraman, Ambalavanan

    2015-09-01

    The present invention provides a sorbent for the removal of carbon dioxide from gas streams, comprising: a CO.sub.2 capacity of at least 9 weight percent when measured at 22.degree. C. and 1 atmosphere; an H.sub.2O capacity of at most 15 weight percent when measured at 25.degree. C. and 1 atmosphere; and an isosteric heat of adsorption of from 5 to 8.5 kilocalories per mole of CO.sub.2. The invention also provides a carbon sorbent in a powder, a granular or a pellet form for the removal of carbon dioxide from gas streams, comprising: a carbon content of at least 90 weight percent; a nitrogen content of at least 1 weight percent; an oxygen content of at most 3 weight percent; a BET surface area from 50 to 2600 m.sup.2/g; and a DFT micropore volume from 0.04 to 0.8 cc/g.

  9. Decontamination formulation with sorbent additive

    Science.gov (United States)

    Tucker; Mark D. , Comstock; Robert H.

    2007-10-16

    A decontamination formulation and method of making that neutralizes the adverse health effects of both chemical and biological compounds, especially chemical warfare (CW) and biological warfare (BW) agents, and toxic industrial chemicals. The formulation provides solubilizing compounds that serve to effectively render the chemical and biological compounds, particularly CW and BW compounds, susceptible to attack, and at least one reactive compound that serves to attack (and detoxify or kill) the compound. The formulation includes at least one solubilizing agent, a reactive compound, a bleaching activator, a sorbent additive, and water. The highly adsorbent, water-soluble sorbent additive (e.g., sorbitol or mannitol) is used to "dry out" one or more liquid ingredients, such as the liquid bleaching activator (e.g., propylene glycol diacetate or glycerol diacetate) and convert the activator into a dry, free-flowing powder that has an extended shelf life, and is more convenient to handle and mix in the field.

  10. Silica Nephropathy

    Directory of Open Access Journals (Sweden)

    N Ghahramani

    2010-06-01

    Full Text Available Occupational exposure to heavy metals, organic solvents and silica is associated with a variety of renal manifestations. Improved understanding of occupational renal disease provides insight into environmental renal disease, improving knowledge of disease pathogenesis. Silica (SiO2 is an abundant mineral found in sand, rock, and soil. Workers exposed to silica include sandblasters, miners, quarry workers, masons, ceramic workers and glass manufacturers. New cases of silicosis per year have been estimated in the US to be 3600–7300. Exposure to silica has been associated with tubulointerstitial disease, immune-mediated multisystem disease, chronic kidney disease and end-stage renal disease. A rare syndrome of painful, nodular skin lesions has been described in dialysis patients with excessive levels of silicon. Balkan endemic nephropathy is postulated to be due to chronic intoxication with drinking water polluted by silicates released during soil erosion. The mechanism of silica nephrotoxicity is thought to be through direct nephrotoxicity, as well as silica-induced autoimmune diseases such as scleroderma and systemic lupus erythematosus. The renal histopathology varies from focal to crescentic and necrotizing glomerulonephritis with aneurysm formation suggestive of polyarteritis nodosa. The treatment for silica nephrotoxicity is non-specific and depends on the mechanism and stage of the disease. It is quite clear that further research is needed, particularly to elucidate the pathogenesis of silica nephropathy. Considering the importance of diagnosing exposure-related renal disease at early stages, it is imperative to obtain a thorough occupational history in all patients with renal disease, with particular emphasis on exposure to silica, heavy metals, and solvents.

  11. Preparation of Silica Modified with 2-Mercaptoimidazole and its SorptionProperties of Chromium(III

    Directory of Open Access Journals (Sweden)

    Harry Budiman

    2009-01-01

    Full Text Available Modified silica gel was prepared to remove the heavy metal of chromium(III from water sample. Silica gel was used as supporting material and the 2-mercaptoimidazole was immobilized onto surface silica so that the silica would have selective properties to adsorb the heavy metal chromium(III through the formation of coordination compound between the 2-mercaptoimidazole and chromium(III. The characterization of modified silica gel was carried out by analyzing the Fourier Transform Infrared Spectrum of this material in order to ensure the immobilization of 2-mercaptoimidazole onto the surface. The effect of pH solution, initial concentration of chromium(III, and interaction time were investigated in batch mode to find the adsorption properties of chromium(III onto modified silica. The condition optimum of these parameters was applied to determine the removal percentage of chromium(III in water sample using the modified silica gel

  12. Air cleaning using regenerative silica gel wheel

    DEFF Research Database (Denmark)

    Fang, Lei

    2011-01-01

    This paper discussed the necessity of indoor air cleaning and the state of the art information on gas-phase air cleaning technology. The performance and problems of oxidation and sorption air cleaning technology were summarized and analysed based on the literature studies. Eventually, based...... on an experimental study, a technology called clean air heat pump is proposed as a practical approach for indoor air cleaning....

  13. Sol-gel materials for optofluidics - process and applications

    DEFF Research Database (Denmark)

    Mikkelsen, Morten Bo Lindholm

    2011-01-01

    This Ph.D. thesis is concerned with the use of sol-gel materials in optofluidic applications and the physics of DNA molecules in nanoconfinement. The bottom-up formation of solid material, which is provided by the sol-gel process, enables control of the chemical composition and porosity...... of the material. At early stages of gelation, thin gel coatings can be structured by nanoimprint lithography, and purely inorganic silica materials can be obtained by subsequent thermal annealing. The sol-gel process thus constitutes a unique method for nanofabrication of silica materials of special properties....... In this work, sol-gel silica is introduced as a new material class for the fabrication of lab-on-a-chip devices for DNA analysis. An imprint process with a rigid, non-permeable stamp was developed, which enabled fabrication of micro- and nanofluidic silica channels in a single process step without use of any...

  14. Sorbent Nanotechnologies for Water Cleaning

    Science.gov (United States)

    Ahmed, Snober

    Despite decades of regulatory efforts to mitigate water pollution, many chemicals, particularly heavy metals, still present risks to human health. In addition to direct exposure, certain metals such as mercury threaten public health due to its persistence, bioaccumulation and bioamplification throughout the food chain. A number of U.S. Federal and State regulations have been established to reduce the levels of mercury in water. Activated carbon (AC) has been widely explored for the removal of mercury. However, AC suffers from many limitations inherent to its chemical properties, and it becomes increasingly challenging to meet current and future regulations by simply modifying AC to enhance its performance. Recently, the performance of nanosorbents have been studied in order to removal pollutants. Nanosorbents utilize the ultra-high reactive surface of nanoparticles for rapid, effective and even permanent sequestration of heavy metals from water and air, thus showed promising results as compared to AC. The goal of this thesis research is to develop nanomaterial-based sorbents for the removal of mercury from water. It describes the development of a new solid-support assisted growth of selenium nanoparticles, their use for water remediation, and the development of a new nanoselenium-based sorbent sponge for fast and efficient mercury removal. The nanoselenium sorbent not only shows irreversible interaction with mercury but also exhibits remarkable properties by overcoming the limitations of AC. The nanoselenium sponge was shown to remove mercury to undetectable levels within one minute. This new sponge technology would have an impact on inspiring new stringent regulations and lowering costs to help industries meet regulatory requirements, which will ultimately help improve air and water quality, aquatic life and public health.

  15. Sorbent Structural Impacts Due to Humidity on Carbon Dioxide Removal Sorbents for Advanced Exploration Systems

    Science.gov (United States)

    Watson, David; Knox, James C.; West, Phillip; Stanley, Christine M.; Bush, Richard

    2015-01-01

    The Life Support Systems Project (LSSP) under the Advanced Exploration Systems (AES) program builds upon the work performed under the AES Atmosphere Resource Recovery and Environmental Monitoring (ARREM) project focusing on the numerous technology development areas. The CO2 removal and associated air drying development efforts are focused on improving the current state-of-the-art system on the International Space Station (ISS) utilizing fixed beds of sorbent pellets by seeking more robust pelletized sorbents, evaluating structured sorbents, and examining alternate bed configurations to improve system efficiency and reliability. A component of the CO2 removal effort encompasses structural stability testing of existing and emerging sorbents. Testing will be performed on dry sorbents and sorbents that have been conditioned to three humidity levels. This paper describes the sorbent structural stability screening efforts in support of the LSS Project within the AES Program.

  16. On shear rheology of gel propellants

    Energy Technology Data Exchange (ETDEWEB)

    Rahimi, Shai; Peretz, Arie [RAFAEL, MANOR Propulsion and Explosive Systems Division, Haifa (Israel); Natan, Benveniste [Faculty of Aerospace Engineering, Technion - Israel Institute of Technology, Haifa (Israel)

    2007-04-15

    Selected fuel, oxidizer and simulant gels were prepared and rheologically characterized using a rotational rheometer. For fuel gelation both organic and inorganic gellants were utilized, whereas oxidizers and simulants were gelled with addition of silica and polysaccharides, respectively. The generalized Herschel-Bulkley constitutive model was found to most adequately represent the gels studied. Hydrazine-based fuels, gelled with polysaccharides, were characterized as shear-thinning pseudoplastic fluids with low shear yield stress, whereas inhibited red-fuming nitric acid (IRFNA) and hydrogen peroxide oxidizers, gelled with silica, were characterized as yield thixotropic fluids with significant shear yield stress. Creep tests were conducted on two rheological types of gels with different gellant content and the results were fitted by Burgers-Kelvin viscoelastic constitutive model. The effect of temperature on the rheological properties of gel propellant simulants was also investigated. A general rheological classification of gel propellants and simulants is proposed. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  17. Effect of cerium oxide doping on the performance of CaO-based sorbents during calcium looping cycles.

    Science.gov (United States)

    Wang, Shengping; Fan, Shasha; Fan, Lijing; Zhao, Yujun; Ma, Xinbin

    2015-04-21

    A series of CaO-based sorbents were synthesized through a sol-gel method and doped with different amounts of CeO2. The sorbent with a Ca/Ce molar ratio of 15:1 showed an excellent absorption capacity (0.59 gCO2/g sorbent) and a remarkable cycle durability (up to 18 cycles). The admirable capture performance of CaCe-15 was ascribed to its special morphology formed by the doping of CeO2 and the well-distributed CeO2 particles. The sorbents doped with CeO2 possessed a loose shell-connected cross-linking structure, which was beneficial for the contact between CaO and CO2. CaO and CeO2 were dispersed homogeneously, and the existence of CeO2 also decreased the grain size of CaO. The well-dispersed CeO2, which could act as a barrier, effectively prevented the CaO crystallite from growing and sintering, thus the sorbent exhibited outstanding stability. The doping of CeO2 also improved the carbonation rate of the sorbent, resulting in a high capacity in a short period of time.

  18. Sorbents for the oxidation and removal of mercur

    Science.gov (United States)

    Olson, Edwin S.; Holmes, Michael J.; Pavlish, John Henry

    2017-09-12

    A promoted activated carbon sorbent is described that is highly effective for the removal of mercury from flue gas streams. The sorbent comprises a new modified carbon form containing reactive forms of halogen and halides. Optional components may be added to increase reactivity and mercury capacity. These may be added directly with the sorbent, or to the flue gas to enhance sorbent performance and/or mercury capture. Mercury removal efficiencies obtained exceed conventional methods. The sorbent can be regenerated and reused. Sorbent treatment and preparation methods are also described. New methods for in-flight preparation, introduction, and control of the active sorbent into the mercury contaminated gas stream are described.

  19. Sorbents for the oxidation and removal of mercury

    Science.gov (United States)

    Olson, Edwin S [Grand Forks, ND; Holmes, Michael J [Thompson, ND; Pavlish, John H [East Grand Forks, MN

    2008-10-14

    A promoted activated carbon sorbent is described that is highly effective for the removal of mercury from flue gas streams. The sorbent comprises a new modified carbon form containing reactive forms of halogen and halides. Optional components may be added to increase reactivity and mercury capacity. These may be added directly with the sorbent, or to the flue gas to enhance sorbent performance and/or mercury capture. Mercury removal efficiencies obtained exceed conventional methods. The sorbent can be regenerated and reused. Sorbent treatment and preparation methods are also described. New methods for in-flight preparation, introduction, and control of the active sorbent into the mercury contaminated gas stream are described.

  20. Sorbents for the oxidation and removal of mercury

    Science.gov (United States)

    Olson, Edwin S [Grand Forks, ND; Holmes, Michael J [Thompson, ND; Pavlish, John H [East Grand Forks, MN

    2012-05-01

    A promoted activated carbon sorbent is described that is highly effective for the removal of mercury from flue gas streams. The sorbent comprises a new modified carbon form containing reactive forms of halogen and halides. Optional components may be added to increase reactivity and mercury capacity. These may be added directly with the sorbent, or to the flue gas to enhance sorbent performance and/or mercury capture. Mercury removal efficiencies obtained exceed conventional methods. The sorbent can be regenerated and reused. Sorbent treatment and preparation methods are also described. New methods for in-flight preparation, introduction, and control of the active