WorldWideScience

Sample records for 22f adsorption step

  1. One-step polymer surface modification for minimizing drug, protein, and DNA adsorption in microanalytical systems

    Larsen, Esben Kjær Unmack; Larsen, Niels Bent

    2013-01-01

    The non-specific adsorption of dissolved analytes strongly reduces the sensitivity and reliability in polymer microanalytical systems. Here, a one-step aqueous phase procedure modifies polymer material surfaces to strongly reduce their non-specific adsorption of a broad range of organic analytes ...... microanalytical systems, including polystyrene (PS), cyclic olefin copolymer (COC), liquid crystalline polymer (LCP), and polyimide (PI)....

  2. Solid-gas reaction with adsorption as the rate limiting step.

    Wróbel, Rafał; Arabczyk, Walerian

    2006-07-27

    The model of nucleation where adsorption of reactant is a rate-limiting step has been considered. Assuming the adsorption range model, a numerical simulation has been made. The dependency of bulk concentration and surface coverage versus time and thermogravimetric curves are presented. The crystallite size is suggested to be the key factor of the nucleation rate. Theoretical considerations have been compared with the experimental results of the iron nitriding reaction. PMID:16854036

  3. One-step polymer surface modification for minimizing drug, protein, and DNA adsorption in microanalytical systems.

    Larsen, Esben Kjær Unmack; Larsen, Niels B

    2013-02-21

    The non-specific adsorption of dissolved analytes strongly reduces the sensitivity and reliability in polymer microanalytical systems. Here, a one-step aqueous phase procedure modifies polymer material surfaces to strongly reduce their non-specific adsorption of a broad range of organic analytes including hydrophobic and hydrophilic drugs (0.23 8) in their pharmaceutically relevant concentration range ≤100 nM. The low adsorption is mediated by photochemical conjugation, where polyethylene glycol (PEG) polymers in aqueous solution are covalently bound to the surface by UV illumination of dissolved benzophenone and a functionalized PEG. The method can coat the interior of polymer systems made from a range of materials commonly used in microanalytical systems, including polystyrene (PS), cyclic olefin copolymer (COC), liquid crystalline polymer (LCP), and polyimide (PI). PMID:23254780

  4. Adsorption and Diffusion of O Atoms on Ag(210) Stepped Surface

    DIAO Zhao-yu; ZHANG Xue-na; WANG Ze-xin; ZHANG Jing

    2007-01-01

    The O-Ag(210) surface adsorption system was studied via the five-parameter Morse potential theory. Meanwhile, the 2O-Ag(210) system was investigated via the extended London-Eyring-Polanyi-Sato(LEPS) potential theory to learn the interaction between the adsorption states. Calculated results demonstrate that there are two stable onsurface adsorption sites(B and H) for O atoms on Ag(210) stepped surface. And the perpendicular vibrations are 30.3 and 42. 9 meV, which are close to that observed in high resolution electron energy loss spectroscopy(HREELS). Also, there exists an octahedral subsurface adsorption state with a high vibrational frequency, and the interaction between the on-surface and subsurface O species is slight. The mode at 54. 6 meV, which is close to that observed in HREELS(54-56 meV), is because of the vibration of the O atom on B site under the influence of that on H site.

  5. Some problems in adsorption and calorimetric studies of the steps of catalytic processes

    Victor E. Ostrovskii

    2004-01-01

    Principal side factors as well as technical and procedural peculiarities capable of distorting the results of measurements of adsorbed and desorbed amounts, of falsifying the nature of the processes proceeding in the systems under study, and of promoting artifacts in calorimetric and other studies of gas chemisorption on powders are considered. Modified techniques and procedures allowing the elimination of sources of side phenomena and artifacts and freeing traditional glass static adsorption apparatuses and experimental procedures from undesirable factors and peculiarities are proposed.Some available chemisorption and calorimetric data representing artifacts and also some data that are not artifacts but,due to imperfections of chemisorption techniques, show up as artifacts are presented and discussed. Several applications of the improved techniques and procedures to calorimetric and adsorption studies of the steps of catalytic processes proceeding on the basis of natural gas and of products of its processing are presented and discussed.

  6. Adsorption study of hydrogen on a stepped Pt (997) surface using low energy recoil scattering

    Information on the binding energy of hydrogen adsorbed on a stepped Pt(S)-[9(111)x(111)] surface can be obtained by bombarding this surface with low energy noble gas ions and by measuring the yield of recoil hydrogen. The angle between the incident ions and the detected recoil hydrogen particles is fixed at 300. The applied technique appears to be so sensitive that the dose of primary ions required for measuring an energy spectrum amounts to only 2x10-4 of a monolayer. By a suitable choice of the scattering geometry one may distinguish between the adsorption properties of step edges and terraces. Step edge properties are probed preferentially by directing the ion beam step-upwards at glancing incidence, whereas terrace sites are probed mainly under specular conditions (e.g. parallel to the steps). The yield of recoil hydrogen is measured at constant equilibrium hydrogen pressure as a function of the sample temperature for both geometries. The shapes of the isobars are distinctly different. For step edge sites a coverage independent binding energy of 93 kJ/mol is measured and for terrace sites we deduce an initial value of 75 kJ/mol gradually decreasing with increasing coverage to 58 kJ/mol at theta=0.45. (orig.)

  7. nanoparticles via a facile one-step solvothermal process for adsorption of bovine serum albumin

    Shen, Mao; Yu, Yujing; Fan, Guodong; Chen, Guang; Jin, Ying min; Tang, Wenyuan; Jia, Wenping

    2014-06-01

    Preparation of magnetic nanoparticles coated with chitosan (CS-coated Fe3O4 NPs) in one step by the solvothermal method in the presence of different amounts of added chitosan is reported here. The magnetic property of the obtained magnetic composite nanoparticles was confirmed by X-ray diffraction (XRD) and magnetic measurements (VSM). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) allowed the identification of spherical nanoparticles with about 150 nm in average diameter. Characterization of the products by Fourier transform infrared spectroscopy (FTIR) demonstrated that CS-coated Fe3O4 NPs were obtained. Chitosan content in the obtained nanocomposites was estimated by thermogravimetric analysis (TGA). The adsorption properties of the CS-coated Fe3O4 NPs for bovine serum albumin (BSA) were investigated under different concentrations of BSA. Compared with naked Fe3O4 nanoparticles, the CS-coated Fe3O4 NPs showed a higher BSA adsorption capacity (96.5 mg/g) and a fast adsorption rate (45 min) in aqueous solutions. This work demonstrates that the prepared magnetic nanoparticles have promising applications in enzyme and protein immobilization.

  8. Thermodynamic properties of hydrogen-water adsorption at terraces and steps of Pt(111) vicinal surface electrodes

    Gómez-Marín, Ana M.; Feliu, Juan M.

    2016-04-01

    In this work, the effect of temperature on the adsorption states of Pt(111) vicinal surface electrodes in perchloric acid is studied through a thermodynamic analysis. The method allows calculating thermodynamic properties of the interface. In this framework, the concept of the generalized isotherm and the statistical thermodynamics description are applied to calculate formal entropies, enthalpies and Gibbs energies, ΔGbari0, of the adsorption processes at two-dimensional terraces and one-dimensional steps. These values are compared with data from literature. Additionally, the effect of the step density on ΔGbari0 and on the lateral interactions between adsorbed species, ωij, at terraces and steps is also determined. Calculated ΔGbari0, entropies and enthalpies are almost temperature-independent, especially at steps, but they depend on the step orientation. In contrast, ΔGbari0 and ωij at terraces depend on the step density, following a linear tendency for terrace lengths larger than 5 atoms. However, while ΔGbari0 increases with the step density, ωij decreases. Results were explained by considering the modification in the energetic surface balance by hydrogen, Hads, and water, H2Oads, co-adsorption on the electrode, which in turn determines the whole adsorption processes on terraces and steps.

  9. Effect of two-step functionalization of Ti by chemical processes on protein adsorption

    Pisarek, M.; Roguska, A.; Andrzejczuk, M.; Marcon, L.; Szunerits, S.; Lewandowska, M.; Janik-Czachor, M.

    2011-07-01

    Titanium and its alloys are widely used for orthopedic and dental implants because of their superior mechanical properties, low modulus, excellent corrosion resistance and good biocompatibility. However, it takes several months for titanium implants and bone tissue to reach integration. Hence, there is growing interest in shortening the process of osseointegration and thereby reducing surgical restrictions. Various surface modifications have been applied to form a bioactive titanium oxide layer on the metal surface, which is known to accelerate osseointegration. The present work shows that titanium dioxide (TiO 2) layers formed on titanium substrates by etching in a solution of sodium hydroxide (NaOH) or hydrogen peroxide/phosphoric acid (H 3PO 4/H 2O 2, with a volume ratio of 1:1) are highly suitable pre-treatments for apatite-like coating deposition. Using a two-step procedure (etching in an alkaline or acidic solution followed by soaking in Hanks' medium), biomimetic calcium phosphate coatings were deposited on porous TiO 2 layers. The combined effects of surface topography and chemistry on the formation of the calcium phosphate layer are presented. The topography of the TiO 2 layers was characterized using HR-SEM and AFM techniques. The nucleation and growth of calcium phosphate (Ca-P) coatings deposited on TiO 2 porous layers from Hanks' solution was investigated using HR-SEM microscopy. AES, XPS and FTIR surface analytical techniques were used to characterize the titanium dioxide layers before and after deposition of the calcium phosphate coatings, as well as after the process of protein adsorption. To evaluate the potential use of such materials for biomedical applications, the adsorption of serum albumin, the most abundant protein in the blood, was studied on such surfaces.

  10. Elementary Steps of Syngas Reactions on Mo2C(001): Adsorption Thermochemistry and Bond Dissociation

    Medford, Andrew

    2012-02-16

    Density functional theory (DFT) and ab initio thermodynamics are applied in order to investigate the most stable surface and subsurface terminations of Mo{sub 2}C(001) as a function of chemical potential and in the presence of syngas. The Mo-terminated (001) surface is then used as a model surface to evaluate the thermochemistry and energetic barriers for key elementary steps in syngas reactions. Adsorption energy scaling relations and Broensted-Evans-Polanyi relationships are established and used to place Mo{sub 2}C into the context of transition metal surfaces. The results indicate that the surface termination is a complex function of reaction conditions and kinetics. It is predicted that the surface will be covered by either C{sub 2}H{sub 2} or O depending on conditions. Comparisons to transition metals indicate that the Mo-terminated Mo{sub 2}C(001) surface exhibits carbon reactivity similar to transition metals such as Ru and Ir, but is significantly more reactive towards oxygen.

  11. Repulsive interactions induced by specific adsorption: Anomalous step diffusivity and inadequacy of nearest-neighbor Ising model. (part I experimental)

    Al-Shakran, Mohammad; Kibler, Ludwig A.; Jacob, Timo; Ibach, Harald; Beltramo, Guillermo L.; Giesen, Margret

    2016-09-01

    This is Part I of two closely related papers, where we show that the specific adsorption of anions leads to a failure of the nearest-neighbor Ising model to describe island perimeter curvatures on Au(100) electrodes in dilute KBr, HCl and H2SO4 electrolytes and the therewith derived step diffusivity vs. step orientation. This result has major consequences for theoretical studies aiming at the understanding of growth, diffusion and degradation phenomena. Part I focuses on the experimental data. As shown theoretically in detail in Part II (doi:10.1016/j.susc.2016.03.022), a set of nearest-neighbor and next-nearest-neighbor interaction energies (ɛNN, ɛNNN) can uniquely be derived from the diffusivity of steps along and . We find strong repulsive next-nearest neighbor (NNN) interaction in KBr and HCl, whereas NNN interaction is negligibly for H2SO4. The NNN repulsive interaction energy ɛNNN therefore correlates positively with the Gibbs adsorption energy of the anions. We find furthermore that ɛNNN increases with increasing Br- and Cl- coverage. The results for ɛNN and ɛNNN are quantitatively consistent with the coverage dependence of the step line tension. We thereby establish a sound experimental base for theoretical studies on the energetics of steps in the presence of specific adsorption.

  12. One-step polymer surface modification for minimizing drug, protein, and DNA adsorption in microanalytical systems

    Larsen, Esben Kjær Unmack; Larsen, Niels Bent

    2013-01-01

    including hydrophobic and hydrophilic drugs (0.23 adsorption of even highly hydrophobic drugs (ClogP > 8) in their pharmaceutically relevant concentration range ≤100 nM. The low adsorption is mediated...

  13. Elementary Steps and Site Requirements for NOx Adsorption and Oxidation on Metal and Oxide Surfaces

    Weiss, Brian M.

    2010-01-01

    NO oxidation catalysts are used in conjunction with NOx adsorbents to remove toxic nitrogen oxides from combustion effluents that lack CO and residual hydrocarbons as reductants. Efficient NOx trapping strategies require detailed knowledge of the reaction mechanism and the structural requirements for NO oxidation and for NOx adsorption, which are investigated here by kinetic, isotopic, and spectroscopic methods. NO oxidation rates on Pt, PdO, RhO2, and Co3O4 catalysts increase linearly with O...

  14. Molecular N-2 chemisorption-specific adsorption on step defect sites on Pt surfaces

    Tripa, C. Emil; Zubkov, T.S.; Yates, John T.; Mavrikakis, Manos; Nørskov, Jens Kehlet

    1999-01-01

    Infrared reflection-absorption spectroscopy and density functional theory, within the generalized gradient approximation, were used to investigate both experimentally and theoretically N-2 chemisorption on stepped and smooth Pt surfaces. N-2 chemisorption was observed to occur only on the edge atoms of step defect sites in atop configuration by both methods. The calculated vibrational frequency of N-2 chemisorbed on Pt(112) step sites (2244 cm(-1)) is in good agreement with the frequency obse...

  15. A DFT study of water adsorption on rutile TiO2 (110) surface: The effects of surface steps.

    Zheng, Ting; Wu, Chunya; Chen, Mingjun; Zhang, Yu; Cummings, Peter T

    2016-07-28

    The associative and dissociative adsorption of water molecules at low-coverage situations on rutile TiO2 (110) surface with step defects was investigated by the density functional theory calculations. Structural optimization of the hydroxylated/hydrated configurations at step edges along the 11̄1 crystal directions and the dynamic process of water dissociation were discussed to get a better description of the water/TiO2 interface. Our results indicate that steps on the TiO2 (110) surface could be an active site for water dissociation. The results of geometry optimization suggest that the stability of hydroxylated configuration is largely dependent on the locations of the H species and the recombination of water molecules from hydroxyls is observed in the fully hydroxylated condition. However, these hydroxyls can be stabilized by the associatively absorbed water nearby by forming competitive intermolecular hydrogen bonds. The dynamics of water dissociation and hydrogen diffusion were studied by the first principles molecular dynamics simulation and our results suggest that the hydrogen released by water dissociation can be transferred among the adsorbates, such as the unsaturated oxygen atoms-H2O-hydroxyl (TiO-H2O-OH) complex at step edges, or gradually diffuses to the bulk water system in the form of hydronium (H3O(+)) at higher water coverage. PMID:27475381

  16. A DFT study of water adsorption on rutile TiO2 (110) surface: The effects of surface steps

    Zheng, Ting; Wu, Chunya; Chen, Mingjun; Zhang, Yu; Cummings, Peter T.

    2016-07-01

    The associative and dissociative adsorption of water molecules at low-coverage situations on rutile TiO2 (110) surface with step defects was investigated by the density functional theory calculations. Structural optimization of the hydroxylated/hydrated configurations at step edges along the crystal directions and the dynamic process of water dissociation were discussed to get a better description of the water/TiO2 interface. Our results indicate that steps on the TiO2 (110) surface could be an active site for water dissociation. The results of geometry optimization suggest that the stability of hydroxylated configuration is largely dependent on the locations of the H species and the recombination of water molecules from hydroxyls is observed in the fully hydroxylated condition. However, these hydroxyls can be stabilized by the associatively absorbed water nearby by forming competitive intermolecular hydrogen bonds. The dynamics of water dissociation and hydrogen diffusion were studied by the first principles molecular dynamics simulation and our results suggest that the hydrogen released by water dissociation can be transferred among the adsorbates, such as the unsaturated oxygen atoms-H2O-hydroxyl (TiO-H2O-OH) complex at step edges, or gradually diffuses to the bulk water system in the form of hydronium (H3O+) at higher water coverage.

  17. Spectroscopic study of CO adsorption on CoO-MgO solid solutions. 2. CO adsorption on isolated cobalt ions located on edges and steps

    Zecchina, A.; Spoto, G.; Borello, E.; Giamello, E.

    1984-06-07

    The room-temperature surface chemistry of diluted MgO-CoO solid solutions toward CO is totally accounted for by the selective adsorption of CO on edges and steps whereby the Mg/sup 2 +/, Co/sup 2 +/ and O/sup 2 -/ coordinately unsaturated ions primarily react as O/sub 2//sup -/Mg/sup 2 +/O and/or O/sup 2 -/Co/sup 2 +/O/sup 2 -/ triplets to form C/sub 2/O/sub 2//sup 2 -/ (ketenic-like) and ((CO/sub 2/)/sub 2/CoCO)/sup 2 -/ (carbenoid-carbonylic) species whose relative concentrations depends upon the cobalt oxide mole fraction. Besides these species, also Mg/sup 2 +/-CO (sigma-bonded) and Co/sup 2 +/(CO/sub 3/) (sigma-..pi..-bonded) complexes are contemporarily detected. The simultaneous presence in fixed ratios of both Co/sup 2 +/, Mg/sup 2 +/ and (O/sup 2 -/Mg/sup 2 +/O/sup 2 -/), (O/sup 2 -/Co/sup 2 +/O/sup 2 -/) reactive ions and groupings of ions in the same surface regions is considered as a fingerprint manifestation of the edge chemistry and has been interpreted on the basis of a simplified geometric (unrelaxed) model of the edge regions. The vibrational assignments of all the surface structures have been made on the basis of a complete set of /sup 12/CO/sup 13/CO isotopic substitution experiments.

  18. Pyridine on flat Pt(111) and stepped Pt(355)—An in situ HRXPS investigation of adsorption and thermal evolution

    Wöckel, Claudia; Eilert, Andrè; Welke, Martin; Schöppke, Matthias; Denecke, Reinhard, E-mail: denecke@uni-leipzig.de [Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Linnéstraße 2, 04103 Leipzig (Germany); Steinrück, Hans-Peter [Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 3, 91058 Erlangen (Germany)

    2016-01-07

    We investigated the adsorption and reaction of pyridine on flat Pt(111) and stepped Pt(355) surfaces via high-resolution in situ x-ray photoelectron spectroscopy. The surfaces were exposed to pyridine at temperatures between 112 and 300 K while simultaneously recording XP spectra. Subsequently, the crystals were annealed and the temperature dependencies of the N 1s and C 1s core levels were studied again in a continuous and quantitative way. Various surface species were found, namely, physisorbed, flat-lying and end-on pyridine, α-pyridyl species on the terraces and on the steps and several unidentified high temperature species. We were able to show an influence of the steps of Pt(355) by pre-adsorbing silver next to the step, which selectively suppresses the step adsorption.

  19. A one-step thermal decomposition method to prepare anatase TiO2 nanosheets with improved adsorption capacities and enhanced photocatalytic activities

    Li, Wenting; Shang, Chunli; Li, Xue

    2015-12-01

    Anatase TiO2 nanosheets (NSs) with high surface area have been prepared via a one-step thermal decomposition of titanium tetraisopropoxide (TTIP) in oleylamine (OM), and their adsorption capacities and photocatalytic activities are investigated by using methylene blue (MB) and methyl orange (MO) as model pollutants. During the synthesis procedure, only one type of surfactant, oleylamine (OM), is used as capping agents and no other solvents are added. Structure and properties of the TiO2 NSs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption analysis, UV-vis spectrum, X-ray photoelectron spectroscopy (XPS) and Photoluminescence (PL) methods. The results indicate that the TiO2 NSs possess high surface area up to 378 m2 g-1. The concentration of capping agents is found to be a key factor controlling the morphology and crystalline structure of the product. Adsorption and photodegradation experiments reveal that the prepared TiO2 NSs possess high adsorption capacities of model pollutants MB and high photocatalytic activity, showing that TiO2 NSs can be used as efficient pollutant adsorbents and photocatalytic degradation catalysts of MB in wastewater treatment.

  20. 75 FR 340 - Approval for Expansion of Subzone 22F, Abbott Molecular, Inc. (Pharmaceutical and Molecular...

    2010-01-05

    ...- 17-09); Whereas, notice inviting public comment has been given in the Federal Register (74 FR 8052... Foreign-Trade Zones Board Approval for Expansion of Subzone 22F, Abbott Molecular, Inc. (Pharmaceutical and Molecular Diagnostic Products), Chicago, IL, Area Pursuant to its authority under the...

  1. Preferential adsorption of C60 molecules to step edges of the Si(110)-16 × 2 single domain surface

    The Si(110) surface has a quite unique one-dimensional (1-D) stable structure with 16 × 2 reconstruction. Since the perfectly straight rows extend over micrometers, the 16 × 2 structure can be a superior template for 1-D nanostructures. However, controlled nanostructures using the Si(110)-16 × 2 template has not been fabricated yet. In this study, we have investigated the adsorption of C60 molecules on the Si(110)-16 × 2 surface at various surface temperatures, and found that the C60 preferable adsorption sites are substantially changed, depending on the surface temperature. The obtained results indicate that the organic 1-D nanostructure can be fabricated on the Si(110)-16 × 2 surface by controlling the surface temperature.

  2. The synthesis and characterization of monodispersed chitosan-coated Fe3O4 nanoparticles via a facile one-step solvothermal process for adsorption of bovine serum albumin.

    Shen, Mao; Yu, Yujing; Fan, Guodong; Chen, Guang; Jin, Ying Min; Tang, Wenyuan; Jia, Wenping

    2014-01-01

    Preparation of magnetic nanoparticles coated with chitosan (CS-coated Fe3O4 NPs) in one step by the solvothermal method in the presence of different amounts of added chitosan is reported here. The magnetic property of the obtained magnetic composite nanoparticles was confirmed by X-ray diffraction (XRD) and magnetic measurements (VSM). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) allowed the identification of spherical nanoparticles with about 150 nm in average diameter. Characterization of the products by Fourier transform infrared spectroscopy (FTIR) demonstrated that CS-coated Fe3O4 NPs were obtained. Chitosan content in the obtained nanocomposites was estimated by thermogravimetric analysis (TGA). The adsorption properties of the CS-coated Fe3O4 NPs for bovine serum albumin (BSA) were investigated under different concentrations of BSA. Compared with naked Fe3O4 nanoparticles, the CS-coated Fe3O4 NPs showed a higher BSA adsorption capacity (96.5 mg/g) and a fast adsorption rate (45 min) in aqueous solutions. This work demonstrates that the prepared magnetic nanoparticles have promising applications in enzyme and protein immobilization. PMID:24994954

  3. Enhancement of soil retention for phenanthrene in binary cationic gemini and nonionic surfactant mixtures: Characterizing two-step adsorption and partition processes through experimental and modeling approaches

    Highlights: • The sorption of cationic gemini surfactant at the soil/water interface was studied. • A two-step adsorption and partition model was developed. • The developed model could better simulate the sorption of ionic surfactant on soil. • Binary gemini surfactant mixtures substantially enhanced the soil retention for PHE. • The sorption of cationic gemini was inhibited by the increasing nonionic surfactant. - Abstract: The enhancement of soil retention for phenanthrene (PHE) through the addition of a binary mixture of cationic gemini (12-2-12) and nonionic surfactants (C12E10) was investigated. The maximum apparent sorption coefficient Kd* reached 4247.8 mL/g through the addition of mixed 12-2-12 gemini and C12E10 surfactants, which was markedly higher than the summed individual results in the presence of individual 12-2-12 gemini (1148.6 mL/g) or C12E10 (210.0 mL/g) surfactant. However, the sorption of 12-2-12 gemini was inhibited by the increasing C12E10 dose; and a higher initial 12-2-12 gemini dose showed a higher “desorption” rate. The present study also addressed the sorption behavior of the single 12-2-12 gemini surfactant at the soil/aqueous interface. The sorption isotherm was divided into two steps to elucidate the sorption process; and the sorption schematics were proposed to elaborate the growth of surfactant aggregates corresponding to the various steps of the sorption isotherm. Finally, a two-step adsorption and partition model (TAPM) was developed to simulate the sorption process. Analysis of the equilibrium data indicated that the sorption isotherms of 12-2-12 gemini fitted the TAPM model better. Thermodynamic calculations confirmed that the 12-2-12 gemini sorption at the soil/aqueous interface was spontaneous and exothermic from 288 to 308 K

  4. Combination of granular activated carbon adsorption and deep-bed filtration as a single advanced wastewater treatment step for organic micropollutant and phosphorus removal.

    Altmann, Johannes; Rehfeld, Daniel; Träder, Kai; Sperlich, Alexander; Jekel, Martin

    2016-04-01

    Adsorption onto granular activated carbon (GAC) is an established technology in water and advanced wastewater treatment for the removal of organic substances from the liquid phase. Besides adsorption, the removal of particulate matter by filtration and biodegradation of organic substances in GAC contactors has frequently been reported. The application of GAC as both adsorbent for organic micropollutant (OMP) removal and filter medium for solids retention in tertiary wastewater filtration represents an energy- and space saving option, but has rarely been considered because high dissolved organic carbon (DOC) and suspended solids concentrations in the influent of the GAC adsorber put a significant burden on this integrated treatment step and might result in frequent backwashing and unsatisfactory filtration efficiency. This pilot-scale study investigates the combination of GAC adsorption and deep-bed filtration with coagulation as a single advanced treatment step for simultaneous removal of OMPs and phosphorus from secondary effluent. GAC was assessed as upper filter layer in dual-media downflow filtration and as mono-media upflow filter with regard to filtration performance and OMP removal. Both filtration concepts effectively removed suspended solids and phosphorus, achieving effluent concentrations of 0.1 mg/L TP and 1 mg/L TSS, respectively. Analysis of grain size distribution and head loss within the filter bed showed that considerable head loss occurred in the topmost filter layer in downflow filtration, indicating that most particles do not penetrate deeply into the filter bed. Upflow filtration exhibited substantially lower head loss and effective utilization of the whole filter bed. Well-adsorbing OMPs (e.g. benzotriazole, carbamazepine) were removed by >80% up to throughputs of 8000-10,000 bed volumes (BV), whereas weakly to medium adsorbing OMPs (e.g. primidone, sulfamethoxazole) showed removals <80% at <5,000 BV. In addition, breakthrough behavior was

  5. Enhancement of soil retention for phenanthrene in binary cationic gemini and nonionic surfactant mixtures: Characterizing two-step adsorption and partition processes through experimental and modeling approaches

    Zhao, Shan [Institute for Energy, Environment and Sustainable Communities, University of Regina, Regina, Saskatchewan S4S 0A2 (Canada); Huang, Gordon, E-mail: gordon.huang@uregina.ca [Institute for Energy, Environment and Sustainable Communities, University of Regina, Regina, Saskatchewan S4S 0A2 (Canada); An, Chunjiang [Institute for Energy, Environment and Sustainable Communities, University of Regina, Regina, Saskatchewan S4S 0A2 (Canada); Wei, Jia [Key Laboratory of Beijing for Water Quality Science and Water Environment Recovery Engineering, Beijing University of Technology, Beijing 100124 (China); Yao, Yao [Institute for Energy, Environment and Sustainable Communities, University of Regina, Regina, Saskatchewan S4S 0A2 (Canada)

    2015-04-09

    Highlights: • The sorption of cationic gemini surfactant at the soil/water interface was studied. • A two-step adsorption and partition model was developed. • The developed model could better simulate the sorption of ionic surfactant on soil. • Binary gemini surfactant mixtures substantially enhanced the soil retention for PHE. • The sorption of cationic gemini was inhibited by the increasing nonionic surfactant. - Abstract: The enhancement of soil retention for phenanthrene (PHE) through the addition of a binary mixture of cationic gemini (12-2-12) and nonionic surfactants (C{sub 12}E{sub 10}) was investigated. The maximum apparent sorption coefficient K{sub d}{sup *} reached 4247.8 mL/g through the addition of mixed 12-2-12 gemini and C{sub 12}E{sub 10} surfactants, which was markedly higher than the summed individual results in the presence of individual 12-2-12 gemini (1148.6 mL/g) or C{sub 12}E{sub 10} (210.0 mL/g) surfactant. However, the sorption of 12-2-12 gemini was inhibited by the increasing C{sub 12}E{sub 10} dose; and a higher initial 12-2-12 gemini dose showed a higher “desorption” rate. The present study also addressed the sorption behavior of the single 12-2-12 gemini surfactant at the soil/aqueous interface. The sorption isotherm was divided into two steps to elucidate the sorption process; and the sorption schematics were proposed to elaborate the growth of surfactant aggregates corresponding to the various steps of the sorption isotherm. Finally, a two-step adsorption and partition model (TAPM) was developed to simulate the sorption process. Analysis of the equilibrium data indicated that the sorption isotherms of 12-2-12 gemini fitted the TAPM model better. Thermodynamic calculations confirmed that the 12-2-12 gemini sorption at the soil/aqueous interface was spontaneous and exothermic from 288 to 308 K.

  6. Role of steps in the dissociative adsorption of water on rutile TiO2 (110)

    Kristoffersen, Henrik Høgh; Hansen, Jonas Ørbæk; Martinez, Umberto; Wei, Y.Y.; Matthiesen, Jesper; Streber, Regine; Bechstein, Ralf; Lægsgaard, E.; Besenbacher, F.; Hammer, B.; Wendt, S.

    2013-01-01

    The water-TiO2 interaction is of paramount importance for many processes occurring on TiO2, and the rutile TiO2(110)-(1×1) surface has often been considered as a test case. Yet, no consensus has been reached whether the well-studied surface O vacancies on the terraces are the only active sites for...... water dissociation on rutile TiO2(110)-(1×1), or whether another channel for the creation of H adatoms exists. Here we use high-resolution scanning tunneling microscopy and density functional theory calculations to tackle this long-standing question. Evidence is presented that a second water...... dissociation channel exists on the surfaces of vacuum-annealed TiO2(110) crystals that is associated with the ⟨11¯1⟩ step edges. This second water dissociation channel can be suppressed by blocking of the ⟨11¯1⟩ step edges using ethanol....

  7. [Two steps elution method FI on-line adsorption and preconcentration coupled with FAAS for the determination of trace zinc].

    Wang, Zhong-yuan; Zhang, Hong-kang; Fang, Hong-da; Su, Yao-dong; Mittal, Gauri S

    2011-12-01

    A flow injection two steps elution method on-line sorption and preconcentration system coupled to flame atomic absorption spectrometry (FAAS) was developed for the determination of trace Zn in water samples. The conventional elution procedure was divided into two steps: elution procedure and detection procedure. During the elution procedure, the eluent was pumped into KR by the suction of the peristaltic pump and through PTFE tube instead of peristaltic pump tube. By the new method, the dispersion of the analyte was decreased notably, and high absorbance peak value was achieved. Because the eluent was not through the peristaltic pump tube, the peristaltic pump tube was protected from being eroded. Emptying procedure was added in order to insure the veracity and repeatability of the experiment of every time. With 60 s (sample throughput of 37 x h(-1)) of sampling at a flow rate of 6.0 mL x min(-1), an enhancement factor (EF) of 28 (higher than 9 achieved by conventional elution method) and a detection limit (3sigma) of 0.35 x L(-1) were obtained. The precision (RSD, n=11) was 2.1% at the 20 microg x L(-1) level. When 0.1% phi triethannolamine was used as masking reagent, the recovery rate was from 98.7% to 99.6%. PMID:22295800

  8. Enhancement of soil retention for phenanthrene in binary cationic gemini and nonionic surfactant mixtures: characterizing two-step adsorption and partition processes through experimental and modeling approaches.

    Zhao, Shan; Huang, Gordon; An, Chunjiang; Wei, Jia; Yao, Yao

    2015-04-01

    The enhancement of soil retention for phenanthrene (PHE) through the addition of a binary mixture of cationic gemini (12-2-12) and nonionic surfactants (C12E10) was investigated. The maximum apparent sorption coefficient Kd(*) reached 4247.8 mL/g through the addition of mixed 12-2-12 gemini and C12E10 surfactants, which was markedly higher than the summed individual results in the presence of individual 12-2-12 gemini (1148.6 mL/g) or C12E10 (210.0 mL/g) surfactant. However, the sorption of 12-2-12 gemini was inhibited by the increasing C12E10 dose; and a higher initial 12-2-12 gemini dose showed a higher "desorption" rate. The present study also addressed the sorption behavior of the single 12-2-12 gemini surfactant at the soil/aqueous interface. The sorption isotherm was divided into two steps to elucidate the sorption process; and the sorption schematics were proposed to elaborate the growth of surfactant aggregates corresponding to the various steps of the sorption isotherm. Finally, a two-step adsorption and partition model (TAPM) was developed to simulate the sorption process. Analysis of the equilibrium data indicated that the sorption isotherms of 12-2-12 gemini fitted the TAPM model better. Thermodynamic calculations confirmed that the 12-2-12 gemini sorption at the soil/aqueous interface was spontaneous and exothermic from 288 to 308K. PMID:25576782

  9. One-step synthesis of a novel N-doped microporous biochar derived from crop straws with high dye adsorption capacity.

    Lian, Fei; Cui, Guannan; Liu, Zhongqi; Duo, Lian; Zhang, Guilong; Xing, Baoshan

    2016-07-01

    N-doping is one of the most promising strategies to improve the adsorption capacity and selectivity of carbon adsorbents. Herein, synthesis, characterization and dye adsorption of a novel N-doped microporous biochar derived from direct annealing of crop straws under NH3 is presented. The resultant products exhibit high microporosity (71.5%), atomic percentage of nitrogen (8.81%), and adsorption capacity to dyes, which is about 15-20 times higher than that of original biochar. Specifically, for the sample NBC800-3 pyrolyzed at 800 °C in NH3 for 3 h, its adsorption for acid orange 7 (AO7, anionic) and methyl blue (MB, cationic) is up to 292 mg g(-1) and 436 mg g(-1), respectively, which is among the highest ever reported for carbonaceous adsorbents. The influences of N-doping and porous structure on dye adsorption of the synthesized carbons are also discussed, where electrostatic attraction, π-π electron donor-accepter interaction, and Lewis acid-base interaction mainly contribute to AO7 adsorption, and surface area (especially pore-filling) dominates MB adsorption. The N-doped biochar can be effectively regenerated and reused through direct combustion and desorption approaches. PMID:27039365

  10. Study of Fe(III) adsorption onto Dowex-Marathon resin, as a rate determining step of the U(IV) oxidation in 235U enrichment column

    The Fe(III) adsorption onto Dowex-Marathon resin was well described by pseudo-second order kinetics with a high correlation factor for all the experimental concentrations. The results were analyzed by Langmuir, Freundlich and Dubinin-Radushkevich isotherm models. The activation energy Ea (7.96 ± 0.2 kJ/mol) indicates a physisorption process as in the case of U(VI) adsorption onto the same resin. The thermodynamic parameters: ΔG deg = (-7.91) / (-13.68) kJ/mol, ΔH deg = 35.60 ± 0.89 kJ/mol and ΔS deg = 143.31 ± 3.58 J/mol K, were determined, the Fe(III) adsorption being spontaneous and endothermic. (author)

  11. A one-step carbonization route towards nitrogen-doped porous carbon hollow spheres with ultrahigh nitrogen content for CO 2 adsorption

    Wang, Yu

    2015-01-01

    © The Royal Society of Chemistry 2015. Nitrogen doped porous carbon hollow spheres (N-PCHSs) with an ultrahigh nitrogen content of 15.9 wt% and a high surface area of 775 m2 g-1 were prepared using Melamine-formaldehyde nanospheres as hard templates and nitrogen sources. The N-PCHSs were completely characterized and were found to exhibit considerable CO2 adsorption performance (4.42 mmol g-1).

  12. Structure sensitivity in adsorption

    Hammer, Bjørk; Nielsen, Ole Holm; Nørskov, Jens Kehlet

    The structure sensitivity of CO adsorption on different flat, stepped, kinked and reconstructed Pt surfaces is studied using large-scale density-functional calculations. We find an extremely strong structure sensitivity in the adsorption energy with variations up to 1 eV (or 100%) from one...... structure to the next. We propose a model to explain this behavior, and use it to discuss more generally the origin of structure sensitivity in heterogeneous catalysis....

  13. The synthesis and characterization of monodispersed chitosan-coated Fe3O4 nanoparticles via a facile one-step solvothermal process for adsorption of bovine serum albumin

    Shen, Mao; Yu, Yujing; Fan, Guodong; Chen, Guang; Jin, Ying min; Tang, Wenyuan; Jia, Wenping

    2014-01-01

    Preparation of magnetic nanoparticles coated with chitosan (CS-coated Fe3O4 NPs) in one step by the solvothermal method in the presence of different amounts of added chitosan is reported here. The magnetic property of the obtained magnetic composite nanoparticles was confirmed by X-ray diffraction (XRD) and magnetic measurements (VSM). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) allowed the identification of spherical nanoparticles with about 150 nm in averag...

  14. Specific heat, cell parameters, phase T- p diagram, and permittivity of cryolite (NH4)3Nb(O2)2F4

    Fokina, V. D.; Bovina, A. F.; Bogdanov, E. V.; Pogorel'Tsev, E. I.; Laptash, N. M.; Gorev, M. V.; Flerov, I. N.

    2011-10-01

    The temperature dependences of the specific heat, unit cell parameters, susceptibility to hydrostatic pressure, and permittivity of cryolite (NH4)3Nb(O2)2F4 have been studied. Phase transitions of nonferroelectric nature have been detected. Entropy parameters point to the relation of structure distortions to ordering processes.

  15. Invasive Streptococcus pneumoniae in Canada, 2011-2014: Characterization of new candidate 15-valent pneumococcal conjugate vaccine serotypes 22F and 33F.

    Golden, Alyssa R; Adam, Heather J; Zhanel, George G

    2016-05-17

    Emerging non-PCV-13 Streptococcus pneumoniae serotypes 22F and 33F are included in a new 15-valent pneumococcal conjugate vaccine currently undergoing clinical trials in the United States. This study assessed the antimicrobial resistance and genetic relatedness of these two emerging pneumococcal serotypes. Of the 5075 invasive pneumococcal isolates collected in Canada from 2011 to 2014, 9.8% (497/5075) were serotype 22F and 3.2% (160/5075) were serotype 33F. Despite being among the top 4 most common serotypes collected each study year, serotype 22F demonstrated ≥98% susceptibility to all antimicrobials tested except clarithromycin and few were multi-drug resistant (MDR) (0.8%, 4/497). Serotype 22F isolates were highly clonal (ST433), with two isolates showing high relatedness to MDR international clone Sweden(15A)-25 (ST63). Conversely, serotype 33F showed greater antimicrobial resistance, greater genetic diversity and a higher proportion of MDR isolates (8.8%, 14/160). The prevalence of serotype 33F increased significantly during 2011-2014 (p=0.005). PMID:27085174

  16. Population structure and drug resistance patterns of emerging non-PCV-13 Streptococcus pneumoniae serotypes 22F, 15A, and 8 isolated from adults in Ontario, Canada.

    Duvvuri, Venkata R; Deng, Xianding; Teatero, Sarah; Memari, Nader; Athey, Taryn; Fittipaldi, Nahuel; Gubbay, Jonathan B

    2016-08-01

    The introduction of pneumococcal conjugate vaccines has led to the emergence of non-vaccine serotypes, which contributed to invasive pneumococcal disease in Canada and worldwide. A significant increase in the prevalence of non-13-valent pneumococcal conjugate vaccine (PCV-13)-included serotypes 22F, 15A, and 8 was observed from 2009 to 2013 in Ontario (all p valuesStreptococcus pneumoniae population structures and dynamics, and its utility in molecular surveillance. PMID:27071529

  17. Atomic steps on single crystals

    So far, atomic steps constitute the only well investigated defect among possible structural surface defects. With Low Energy Electron Diffraction (LEED), step density, orientation, terrace width, step arrangements and other structural parameters may be measured. Steps are present on nearly all surfaces; special step configurations may be produced by proper treatment. The presence of steps affects many surface properties like surface states, work function, adsorption and catalytic activity. It is therefore important to know the existence and properties of steps on all investigated surfaces. (orig.)

  18. Next Step for STEP

    Wood, Claire [CTSI; Bremner, Brenda [CTSI

    2013-08-09

    The Siletz Tribal Energy Program (STEP), housed in the Tribe’s Planning Department, will hire a data entry coordinator to collect, enter, analyze and store all the current and future energy efficiency and renewable energy data pertaining to administrative structures the tribe owns and operates and for homes in which tribal members live. The proposed data entry coordinator will conduct an energy options analysis in collaboration with the rest of the Siletz Tribal Energy Program and Planning Department staff. An energy options analysis will result in a thorough understanding of tribal energy resources and consumption, if energy efficiency and conservation measures being implemented are having the desired effect, analysis of tribal energy loads (current and future energy consumption), and evaluation of local and commercial energy supply options. A literature search will also be conducted. In order to educate additional tribal members about renewable energy, we will send four tribal members to be trained to install and maintain solar panels, solar hot water heaters, wind turbines and/or micro-hydro.

  19. Adsorption and wetting.

    Schlangen, L.J.M.

    1995-01-01

    Adsorption and wetting are related phenomena. In order to improve knowledge of both and their relations, experiments, thermodynamics and a theoretical interpretation have been connected, starring n-alkanes.Starting from the Gibbs adsorption equation thermodynamic relations between vapour adsorption

  20. Host receptors for bacteriophage adsorption.

    Bertozzi Silva, Juliano; Storms, Zachary; Sauvageau, Dominic

    2016-02-01

    The adsorption of bacteriophages (phages) onto host cells is, in all but a few rare cases, a sine qua non condition for the onset of the infection process. Understanding the mechanisms involved and the factors affecting it is, thus, crucial for the investigation of host-phage interactions. This review provides a survey of the phage host receptors involved in recognition and adsorption and their interactions during attachment. Comprehension of the whole infection process, starting with the adsorption step, can enable and accelerate our understanding of phage ecology and the development of phage-based technologies. To assist in this effort, we have established an open-access resource--the Phage Receptor Database (PhReD)--to serve as a repository for information on known and newly identified phage receptors. PMID:26755501

  1. Role of steps in N-2 activation on Ru(0001)

    Dahl, Søren; Logadottir, Ashildur; Egeberg, Rasmus;

    1999-01-01

    Using adsorption experiments and density functional calculations we show that N-2 dissociation on the Ru(0001) surface is totally dominated by steps. The measured adsorption rate at the steps is at least 9 orders of magnitude higher than on the terraces at 500 K, and the corresponding calculated ...

  2. Adsorption and wetting.

    Schlangen, L.J.M.

    1995-01-01

    Adsorption and wetting are related phenomena. In order to improve knowledge of both and their relations, experiments, thermodynamics and a theoretical interpretation have been connected, starring n-alkanes.Starting from the Gibbs adsorption equation thermodynamic relations between vapour adsorption and wetting are derived. The surface pressure of a film, formed by vapour adsorption on a solid surface, is calculated by integrating the vapour adsorption isotherm. The surface pressure at the sat...

  3. Investigation of radiotracer adsorption

    Results of laboratory investigation of adsorption of radiotracers in several soil materials are presented. Compounds were chosen which are applied in hydrogeology for tracer determination of underground water flow parameters. Adsorption values were measured as functions of the following parameters: solution concentration, adsorption duration, concentration of hydrogen ions and ion strength of the solution. The most interesting results are: a linear dependence of adsorption on the solution concentration (observed in a wide range of concentrations), and an extended period (several tens of minutes) necessary for the adsorption system to achieve a state approaching dynamic equilibrium. (author)

  4. Effects of purge step on enrichment of low concentration oxygen-bearing coal mine methane based on proportion pressure swing adsorption%反吹过程对等比例变压吸附法分离富集低浓度含氧煤层气的影响

    李永玲; 刘应书; 杨雄; 孟宇; 张传钊

    2012-01-01

    The safety of the adsorption process for low concentration (less than 30% ) coal mine methane was analyzed and studied based on the theory of coward explosion triangle, and then a new safe method for enriching low concentration coal mine methane, called the proportion pressure swing adsorption (PPSA) , was put forward. Furthermore , the effects of purge steps on the enrichment process for low concentration coal mine methane based on proportional pressure swing adsorption were investigated experimentally. The results show that purge steps are helpful to decreasing the oxygen and methane concentration in the exhaust gas, and the oxygen and methane concentration decrease with the increase of the purge time. But the purge steps also decrease the methane concentration in the product. So purge steps can be used in the PPSA process to make the oxygen concentration of the exhaust gas in the safe range and ensure the safety of the enrichment for low concentration coal mine. But the purge time should be appropriately controlled to prevent the methane concentration in the desorption gas from reducing too much.%在Coward爆炸三角形的基础上分析研究了低浓度煤层气(甲烷浓度低于30%)吸附富集过程的安全性,提出了一种安全分离富集低浓度煤层气的方法——等比例变压吸附(PPSA)法,并且通过实验研究了用PPSA法时增加反吹过程对低浓度煤层气吸附富集效果和安全性的影响.结果表明:循环步骤中设置反吹过程有利于降低排放气中甲烷和氧气的体积分数.反吹时间越长,排放气中甲烷和氧气体积分数越低,但会使解吸气即产品气中甲烷浓度降低.为了确保低浓度煤层气吸附富集过程的安全性,可以适当地对吸附塔进行反吹,降低排放气中氧气浓度,使之处于安全范围内.但是反吹时间不宜过长,以免使解吸气中甲烷浓度降低过多,使产品气品质不满足后续设备的使用要求.

  5. Adsorption of inorganic anionic contaminants on surfactant modified minerals

    MAGDALENA TOMASEVIC-CANOVIC

    2003-11-01

    Full Text Available Organo-mineral complexes were obtained by treatment of aluminosilicate minerals (zeolite, bentonite and diatomaceous earth with a primary amine (oleylamine and an alkyl ammonium salt (stearyldimethylbenzyl ammonium chloride. The modification of the zeolite surface was carried out in two steps. The first step was treatment of the zeolite with 2 M HCl. This acid treatment of the zeolite increased its affinity for neutral molecules such as surface-active amines. The second step of the modification was the adsorption of oleylamine on the acid treated zeolite. Four types of organo-mineral complexes were prepared and their anion adsorption properties were compared to those of organo-zeolite. The adsorption of sulphate, bichromate and dihydrogenphosphate anions on the organo-mineral complexes was investigated. The anion adsorption measurements showed that the most efficient adsorbent for anion water pollutants was the primary amine modified H+-form zeolite.

  6. Stepped nozzle

    Sutton, George P.

    1998-01-01

    An insert which allows a supersonic nozzle of a rocket propulsion system to operate at two or more different nozzle area ratios. This provides an improved vehicle flight performance or increased payload. The insert has significant advantages over existing devices for increasing nozzle area ratios. The insert is temporarily fastened by a simple retaining mechanism to the aft end of the diverging segment of the nozzle and provides for a multi-step variation of nozzle area ratio. When mounted in place, the insert provides the nozzle with a low nozzle area ratio. During flight, the retaining mechanism is released and the insert ejected thereby providing a high nozzle area ratio in the diverging nozzle segment.

  7. A Simple Adsorption Experiment

    Guirado, Gonzalo; Ayllon, Jose A.

    2011-01-01

    The study of adsorption phenomenon is one of the most relevant and traditional physical chemistry experiments performed by chemistry undergraduate students in laboratory courses. In this article, we describe an easy, inexpensive, and straightforward way to experimentally determine adsorption isotherms using pieces of filter paper as the adsorbent…

  8. Adsorption dynamics of methyl violet onto granulated mesoporous carbon: Facile synthesis and adsorption kinetics.

    Kim, Yohan; Bae, Jiyeol; Park, Hosik; Suh, Jeong-Kwon; You, Young-Woo; Choi, Heechul

    2016-09-15

    A new and facile one-step synthesis method for preparing granulated mesoporous carbon (GMC) with three-dimensional spherical mesoporous symmetry is prepared to remove large molecular weight organic compounds in aqueous phase. GMC is synthesized in a single step using as-synthesized mesoporous carbon particles and organic binders through a simple and economical synthesis approach involving a simultaneous calcination and carbonization process. Characterization results obtained from SEM, XRD, as well as surface and porosity analysis indicate that the synthesized GMC has similar physical properties to those of the powdered mesoporous carbon and maintains the Brunauer-Emmett-Teller (BET) surface area and pore volume because the new synthesis method prevents the collapse of the pores during the granulation process. Batch adsorption experiments revealed GMC showed a substantial adsorption capacity (202.8 mg/g) for the removal of methyl violet as a target large molecular contaminant in aqueous phase. The mechanisms and dynamics modeling of GMC adsorption were also fully examined, which revealed that surface diffusion was rate limiting step on adsorption process of GMC. Adsorption kinetics of GMC enables 3 times faster than that of granular activated carbon in terms of surface diffusion coefficient. This is the first study, to the best of our knowledge, to synthesize GMC as an adsorbent for water purification by using facile granulation method and to investigate the adsorption kinetics and characteristics of GMC. This study introduces a new and simple method for the synthesis of GMC and reveals its adsorption characteristics for large molecular compounds in a water treatment. PMID:27262123

  9. adsorption, eosin, humic, peat

    Anshar, Andi Muhammad

    2015-01-01

    Eosin is one of the dyes commonly used in the industry and has the potential to cause pollution of the water environment. The Eosin pollution treatment methods used in this study was the adsorption method using humin fraction obtained from the peat land comes from Kalimantan. From the research data showed that the adsorption of eosin in humin result of washing with HCl / HF optimum at pH 4 and a contact time of 60 minutes with the adsorption-order rate was 8,4 x 10-3 min-1

  10. Hybrid adsorptive membrane reactor

    Tsotsis, Theodore T. (Inventor); Sahimi, Muhammad (Inventor); Fayyaz-Najafi, Babak (Inventor); Harale, Aadesh (Inventor); Park, Byoung-Gi (Inventor); Liu, Paul K. T. (Inventor)

    2011-01-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  11. Hybrid adsorptive membrane reactor

    Tsotsis, Theodore T.; Sahimi, Muhammad; Fayyaz-Najafi, Babak; Harale, Aadesh; Park, Byoung-Gi; Liu, Paul K. T.

    2011-03-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  12. Adsorption behaviour of bulgur.

    Erbaş, Mustafa; Aykın, Elif; Arslan, Sultan; Durak, Atike N

    2016-03-15

    The aim of this research was to determine the adsorption behaviour of bulgur. Three different particle sizes (2dry matter and 4.96-16.57, respectively. Constant k was between 0.85 and 0.93, and GAB equation was determined to fit very well for bulgur adsorption, because of %E values lower than 10%. Bulgur must be stored below 70% relative humidity and with less than 10 g water per 100 g of dry mater. PMID:26575716

  13. Application of stepping motor

    This book is divided into three parts, which is about practical using of stepping motor. The first part has six chapters. The contents of the first part are about stepping motor, classification of stepping motor, basic theory og stepping motor, characteristic and basic words, types and characteristic of stepping motor in hybrid type and basic control of stepping motor. The second part deals with application of stepping motor with hardware of stepping motor control, stepping motor control by microcomputer and software of stepping motor control. The last part mentions choice of stepping motor system, examples of stepping motor, measurement of stepping motor and practical cases of application of stepping motor.

  14. Adsorption and regenerative oxidation of trichlorophenol with synthetic zeolite: Ozone dosage and its influence on adsorption performance.

    Zhang, Yongjun; Prigent, Bastien; Geißen, Sven-Uwe

    2016-07-01

    Regeneration of loaded adsorbents is a key step for the sustainability of an adsorption process. In this study, ozone was applied to regenerate a synthetic zeolite for the adsorption of trichlorophenol (TCP) as an organic model pollutant. Three initial concentrations of TCP in water phase were used in adsorption tests. After the equilibrium, zeolite loaded different amounts of TCP was dried and then regenerated with ozone gas. It was found that the adsorption capacity of zeolite was increased through three regeneration cycles. However, the adsorption kinetics was compromised after the regeneration with slightly declined 2nd order reaction constants. The ozone demand for the regeneration was highly dependent on the TCP mass loaded onto the zeolite. It was estimated that the mass ratio of ozone to TCP was 1.2 ± 0.3 g O3/g TCP. PMID:27043379

  15. The Adsorption Effect of Quaternized Chitosan Derivatives on Bile Acid

    Shu Xian MENG; Ya Qing FENG; Wen Jin LI; Cai Xia YIN; Jin Ping DENG

    2006-01-01

    Three quaternized chitosan derivatives were synthesized and their adsorption performance of bile acid from aqueous solution was studied. The adsorption capacities and rates of bile acid onto quaternized chitosan derivatives were evaluated. The kinetic experimental data properly correlated with the second-order kinetic model, which indicated that the chemical sorption is the rate-limiting step. The results showed that the quaternized chitosan derivatives are favorable adsorbents for bile acid.

  16. Adsorption of semiflexible block copolymers on homogeneous surfaces

    Cerdà, Joan J.; Sintes, Tomàs; Sumithra, K.

    2005-01-01

    We present the results of extensive numerical off-lattice Monte Carlo simulations of semiflexible block-copolymer chains adsorbed onto flat homogeneous surfaces. We have compared the behavior of several chain structures, such as homopolymers, diblocks, (AαBα) block copolymers, and random heteropolymers. In all the cases studied, we have found the adsorption process to be favored with an increase of the chain rigidity. Particularly, the adsorption of diblock structures becomes a two-step proce...

  17. Phonon scattering in graphene over substrate steps

    Sevinçli, H., E-mail: haldunsevincli@iyte.edu.tr [Department of Materials Science and Engineering, Izmir Institute of Technology, Gülbahçe Kampüsü, 35430 Urla, Izmir (Turkey); Department of Micro- and Nano-technology (DTU Nanotech), Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark); Brandbyge, M., E-mail: mads.brandbyge@nanotech.dtu.dk [Department of Micro- and Nano-technology (DTU Nanotech), Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark); Center for Nanostructured Graphene(CNG), Department of Micro- and Nano-technology, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark)

    2014-10-13

    We calculate the effect on phonon transport of substrate-induced bends in graphene. We consider bending induced by an abrupt kink in the substrate, and provide results for different step-heights and substrate interaction strengths. We find that individual substrate steps reduce thermal conductance in the range between 5% and 47%. We also consider the transmission across linear kinks formed by adsorption of atomic hydrogen at the bends and find that individual kinks suppress thermal conduction substantially, especially at high temperatures. Our analysis show that substrate irregularities can be detrimental for thermal conduction even for small step heights.

  18. Phonon scattering in graphene over substrate steps

    We calculate the effect on phonon transport of substrate-induced bends in graphene. We consider bending induced by an abrupt kink in the substrate, and provide results for different step-heights and substrate interaction strengths. We find that individual substrate steps reduce thermal conductance in the range between 5% and 47%. We also consider the transmission across linear kinks formed by adsorption of atomic hydrogen at the bends and find that individual kinks suppress thermal conduction substantially, especially at high temperatures. Our analysis show that substrate irregularities can be detrimental for thermal conduction even for small step heights.

  19. Cu and Cd Adsorption on Carbon Aerogel and Xerogel

    Cotet L. C.

    2013-04-01

    Full Text Available Carbon aerogel (CA and xerogel (CX were proposed as new carbon adsorbent materials for Cu and Cd ions from contaminated water (synthetic water samples. These materials were prepared by a sol-gel process that involves a polycondensation of resorcinol and formaldehyde in Na2CO3 catalysis, followed by a drying step, either in supercritical conditions of CO2 to aerogel obtaining or in normal conditions to xerogel obtaining, and a pyrolytic step. Nitrogen adsorption, AFM, SEM, TEM and XRD were used for morpho-structural adsorbent investigation. Cu and Cd ions adsorption experiments were carried out in batch conditions under magnetic stirring. Adsorbent quantity and grain size influence over the adsorption efficiency were considered. Adsorption results expressed as adsorption capacities showed that prepared CA is a better adsorbent than CX. Adsorption capacities up to 14.2 mg g-1 and 8.5 mg g-1 were obtained for Cd2+ and Cu2+ adsorption on CA, respectively.

  20. Competitive Protein Adsorption - Multilayer Adsorption and Surface Induced Protein Aggregation

    Holmberg, Maria; Hou, Xiaolin

    2009-01-01

    high concentration with investigation of single protein adsorption and interdependent adsorption between two specific proteins enables us to map protein adsorption sequences during competitive protein adsorption. Our study shows that proteins can adsorb in a multilayer fashion onto the polymer surfaces......In this study, competitive adsorption of albumin and IgG (immunoglobulin G) from human serum solutions and protein mixtures onto polymer surfaces is studied by means of radioactive labeling. By using two different radiolabels (125I and 131I), albumin and IgG adsorption to polymer surfaces is...... and that the outcome of IgG adsorption is much more sensitive to surface characteristics than the outcome of albumin adsorption. Using high concentrations of protein solution and hydrophobic polymer surfaces during adsorption can induce IgG aggregation, which is observed as extremely high Ig...

  1. Liquid-liquid extraction and adsorption on solid surfaces applied to used lubricant oils recovery

    J. L. Assunção Filho; L. G. M. Moura; A.C.S. RAMOS

    2010-01-01

    In this work, the recovery of base oils from waste lubricants following the steps of solvent extraction, adsorption on solids and solvent removal by evaporation was evaluated. In the step of solvent extraction, the most efficient was 1-butanol, followed by tert-butanol, 2-propanol and ethanol; for the step of adsorption, activated carbon was the most effective solid for PAH removal, confirming the similarity of these compounds with petroleum aromatic fractions. Thus, the optimum solvent-adsor...

  2. Sticky steps inhibit step motions near equilibrium

    Akutsu, Noriko

    2012-12-01

    Using a Monte Carlo method on a lattice model of a vicinal surface with a point-contact-type step-step attraction, we show that, at low temperature and near equilibrium, there is an inhibition of the motion of macrosteps. This inhibition leads to a pinning of steps without defects, adsorbates, or impurities (self-pinning of steps). We show that this inhibition of the macrostep motion is caused by faceted steps, which are macrosteps that have a smooth side surface. The faceted steps result from discontinuities in the anisotropic surface tension (the surface free energy per area). The discontinuities are brought into the surface tension by the point-contact-type step-step attraction. The point-contact-type step-step attraction also originates “step droplets,” which are locally merged steps, at higher temperatures. We derive an analytic equation of the surface stiffness tensor for the vicinal surface around the (001) surface. Using the surface stiffness tensor, we show that step droplets roughen the vicinal surface. Contrary to what we expected, the step droplets slow down the step velocity due to the diminishment of kinks in the merged steps (smoothing of the merged steps).

  3. Regenerative adsorption distillation system

    Ng, Kim Choon

    2013-12-26

    There is provided a regenerative adsorption distillation system comprising a train of distillation effects in fluid communication with each other. The train of distillation effects comprises at least one intermediate effect between the first and last distillation effects of the train, each effect comprising a vessel and a condensing tube for flow of a fluid therein. The system further comprises a pair of adsorption-desorption beds in vapour communication with the last effect and at least one intermediate effect, wherein the beds contain an adsorbent that adsorbs vapour from the last effect and transmits desorbed vapour into at least one of the intermediate effect.

  4. A preliminary study on the adsorptive removal of Cr(VI) using seaweed, Hydrilla verticillata

    The Cr(VI) adsorption efficiency of the seaweed, Hydrilla verticillata, was studied in batches. The adsorbent was characterized using SEM, BET surface area analyzer, Malvern particle size analyzer, EDAX and FT-IR. Cr(VI) removal efficiency of the adsorbent was studied as a function of different adsorption parameters such as contact time, stirring speed, pH, adsorbent dose, particle size, adsorbate concentration, and temperature. Langmuir, Freundlich, and Temkin adsorption isotherm equations were used in the equilibrium modeling. The adsorption process followed pseudo second-order kinetics and intra-particle diffusion was found to be the rate-controlling step. Experimental data follow Langmuir adsorption isotherm. Thermodynamic parameters such as Gibbs free energy and enthalpy of the adsorption process were evaluated to find out the feasibility of the adsorption process. The negative values of Gibb's free energy and positive enthalpy values show the feasibility and endothermic nature of the process. The significance of different adsorption parameters along with their combined effect on the adsorption process has been established through a full 24 factorial design. Among the different adsorption parameters, pH has the most influential effect on the adsorption process followed by adsorbate concentration and combined effects of all the four parameters were tested. The correlation among different adsorption parameters were studied using multi-variate analysis.

  5. Adsorption process to recover hydrogen from feed gas mixtures having low hydrogen concentration

    Golden, Timothy Christopher; Weist, Jr., Edward Landis; Hufton, Jeffrey Raymond; Novosat, Paul Anthony

    2010-04-13

    A process for selectively separating hydrogen from at least one more strongly adsorbable component in a plurality of adsorption beds to produce a hydrogen-rich product gas from a low hydrogen concentration feed with a high recovery rate. Each of the plurality of adsorption beds subjected to a repetitive cycle. The process comprises an adsorption step for producing the hydrogen-rich product from a feed gas mixture comprising 5% to 50% hydrogen, at least two pressure equalization by void space gas withdrawal steps, a provide purge step resulting in a first pressure decrease, a blowdown step resulting in a second pressure decrease, a purge step, at least two pressure equalization by void space gas introduction steps, and a repressurization step. The second pressure decrease is at least 2 times greater than the first pressure decrease.

  6. Dissociative adsorption of methane on surface oxide structures of Pd-Pt alloys

    Dianat, Arezoo; Seriani, Nicola; Ciacchi, Lucio Colombi; Pompe, Wolfgang; Cuniberti, Gianaurelio; Bobeth, Manfred

    2010-01-01

    The dissociative adsorption of methane on variously oxidized Pd, Pt and Pd-Pt surfaces is investigated using density-functional theory, as a step towards understanding the combustion of methane on these materials. For Pd-Pt alloys, models of surface oxide structures are built on the basis of known oxides on Pd and Pt. The methane adsorption energy presents large variations depending on the oxide structure and composition. Adsorption is endothermic on the bare Pd(111) metal surface as well as ...

  7. Physical adsorption and molecular dynamics

    Some aspects of noble gases adsorption (except He) on graphite substracts are reviewed. Experimental results from this adsorption are analyzed and compared with molecular dynamics calculations. (L.C.)

  8. New Adsorption Methods.

    Wankat, Phillip C.

    1984-01-01

    Discusses a simple method for following the movement of a solute in an adsorption or ion exchange system. This movement is used to study a variety of operational methods, including continuous flow and pulsed flow counter-current operations and simulated counter-current systems. Effect of changing thermodynamic variables is also considered. (JM)

  9. Kinetics and isotherms of Neutral Red adsorption on peanut husk.

    Han, Runping; Han, Pan; Cai, Zhaohui; Zhao, Zhenhui; Tang, Mingsheng

    2008-01-01

    Adsorption of Neutral Red (NR) onto peanut husk in aqueous solutions was investigated at 295 K. Experiments were carried out as function of pH, adsorbent dosage, contact time, and initial concentration. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Toth isotherm models. The results indicated that the Toth and Langmuir models provided the best correlation of the experimental data. The adsorption capacity of peanut husk for the removal of NR was determined with the Langmuir and found to be 37.5 mg/g at 295 K. The adsorption kinetic data were modeled using the pseudo-first order, pseudo-second order, and intra-particle diffusion kinetic equations. It was seen that the pseudo-first order and pseudo-second order kinetic equations could describe the adsorption kinetics. The intraparticle diffusion model was also used to express the adsorption process at the two-step stage. It was implied that peanut husk may be suitable as adsorbent material for adsorption of NR from aqueous solutions. PMID:19143308

  10. Kinetics and isotherms of Neutral Red adsorption on peanut husk

    HAN Runping; HAN Pan; CAI Zhaohui; ZHAO Zhenhui; TANG Mingsheng

    2008-01-01

    Adsorption of Neutral Red (NR) onto peanut husk in aqueous solutions was investigated at 295 K. Experiments were carded out as function of pH, adsorbent dosage, contact time, and initial concentration. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Toth isotherm models. The results indicated that the Toth and Langmuir models provided the best correlation of the experimental data. The adsorption capacity of peanut husk for the removal of NR was determined with the Langmuir and found to be 37.5 mg/g at 295 K. The adsorption kinetic data were modeled using the pseudo-first order, pseudo-second order, and intra-particle diffusion kinetic equations. It was seen that the pseudo-first order and pseudo-second order kinetic equations could describe the adsorption kinetics. The intraparticle diffusion model was also used to express the adsorption process at the two-step stage. It was implied that peanut husk may be suitable as adsorbent material for adsorption of NR from aqueous solutions.

  11. Albumin adsorption on oxide thin films studied by spectroscopic ellipsometry

    Silva-Bermudez, P., E-mail: suriel21@yahoo.com [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito Exterior s/n, C.U., 04510, Mexico D.F. (Mexico); Unidad de Posgrado, Facultad de Odontologia, Universidad Nacional Autonoma de Mexico, CU, 04510, Mexico D.F. (Mexico); Rodil, S.E.; Muhl, S. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Circuito Exterior s/n, C.U., 04510, Mexico D.F. (Mexico)

    2011-12-15

    Thin films of tantalum, niobium, zirconium and titanium oxides were deposited by reactive magnetron sputtering and their wettability and surface energy, optical properties, roughness, chemical composition and microstructure were characterized using contact angle measurements, spectroscopic ellipsometry, profilometry, X-ray photoelectron spectroscopy and X-ray diffraction, respectively. The purpose of the work was to correlate the surface properties of the films to the Bovine Serum Albumin (BSA) adsorption, as a first step into the development of an initial in vitro test of the films biocompatibility, based on standardized protein adsorption essays. The films were immersed into BSA solutions with different protein concentrations and protein adsorption was monitored in situ by dynamic ellipsometry; the adsorption-rate was dependent on the solution concentration and the immersion time. The overall BSA adsorption was studied in situ using spectroscopic ellipsometry and it was found to be influenced by the wettability of the films; larger BSA adsorption occurred on the more hydrophobic surface, the ZrO{sub 2} film. On the Ta{sub 2}O{sub 5}, Nb{sub 2}O{sub 5} and TiO{sub 2} films, hydrophilic surfaces, the overall BSA adsorption increased with the surface roughness or the polar component of the surface energy.

  12. Traps for phosphorus adsorption

    Several AL2O3 supported oxides such as: NiO, CuO, Co2O3 BaO, CeO2 and ZnO were investigated for phosphorus adsorption. Zno/y-Al2O3 exhibited the highest phosphorus adsorption capacity. However, since it diminishes the activity of to the reaction mixture it should be located upstream of the NoX catalyst, i.e. 0,3% Pd-H-MOR, in order to protect it against p poisoning. The treatment procedure with citric acid was effective for the removal of more than 70% phosphorus from the adsorbent, ZnO/y-Al2O3

  13. Spectroscopic evidence for the adsorption of propene on gold nanoparticles Spectroscopic evidence for the adsorption of propene on gold nanoparticles

    Nijhuis, T.A.; Sacaliuc, E.; Beale, A.M.; van der Eerden, A.M.J.; Schouten, J.C.; Weckhuysen, B.M.

    2008-01-01

    The adsorption of propene on supported gold nanoparticles has been experimentally identified as a reaction step in the hydro-epoxidation of propene. This new finding was made possible by applying a detailed analysis of in situ measured XANES spectra. For this purpose, gold-on-silica catalysts were i

  14. The way to collisions, step by step

    2009-01-01

    While the LHC sectors cool down and reach the cryogenic operating temperature, spirits are warming up as we all eagerly await the first collisions. No reason to hurry, though. Making particles collide involves the complex manoeuvring of thousands of delicate components. The experts will make it happen using a step-by-step approach.

  15. Step-Growth Polymerization.

    Stille, J. K.

    1981-01-01

    Following a comparison of chain-growth and step-growth polymerization, focuses on the latter process by describing requirements for high molecular weight, step-growth polymerization kinetics, synthesis and molecular weight distribution of some linear step-growth polymers, and three-dimensional network step-growth polymers. (JN)

  16. Methylene blue adsorption from aqueous solution by dehydrated peanut hull

    Dyes are colour organic compounds which can colorize the other substances. These substances usually presents in the effluent water of many industries, such as textiles, leather, paper, printing and cosmetics. To observe the potential feasibility of removing colour, peanut hull as an agricultural by-product was dehydrated with sulphuric acid (DPH) and used for adsorption of methylene blue (MB) from aqueous solution. The effects of various parameters such as initial methylene blue concentrations, temperatures and particle sizes were examined and optimal experimental conditions were determined. Adsorption data were well described by the Langmuir model, although they could be modelled by the Freundlich model as well. The adsorption process followed the pseudo-second order kinetic model. The mass transfer model as intraparticle diffusion was applied to the experimental data to examine the mechanisms of rate controlling step. It was found that at the higher initial MB concentration, intraparticle diffusion is becoming significant controlling step. The thermodynamic constants of the adsorption process were also evaluated by using the Langmuir constants related to the equilibrium of adsorption at different temperatures. The results in this study indicated that dehydrated peanut hull was a good adsorbent for removing methylene blue

  17. Copper adsorption in tropical oxisols

    Silveira Maria Lucia Azevedo

    2003-01-01

    Full Text Available Cu adsorption, at concentrations between 0 to 800 mg L-1, was evaluated in surface and subsurface samples of three Brazilian soils: a heavy clayey-textured Rhodic Hapludalf (RH, a heavy clayey-textured Anionic ''Rhodic'' Acrudox (RA and a medium-textured Anionic ''Xanthic'' Acrudox (XA. After adsorption, two consecutive extractions were performed to the samples which received 100 mg L-1 copper. Surface samples adsorbed higher amounts of Cu than the subsurface, and exhibited lower Cu removed after the extractions, reinforcing the influence of the organic matter in the reactions. Cu adsorption was significant in the subsurface horizons of the Oxisols, despite the positive balance of charge, demonstrating the existence of mechanisms for specific adsorption, mainly related to the predominance of iron and aluminum oxides in the mineral fractions. In these samples, Cu was easily removed from the adsorption sites. RH demonstrated a higher capacity for the Cu adsorption in both horizons.

  18. Chromium (VI) adsorption on boehmite

    Granados-Correa, F. [Instituto Nacional de Investigaciones Nucleares, Apartado Postal 18-1027 Col., Escandon, Delegacion Miguel Hidalgo, C.P. 11801 Mexico, D.F. (Mexico)], E-mail: fgc@nuclear.inin.mx; Jimenez-Becerril, J. [Instituto Nacional de Investigaciones Nucleares, Apartado Postal 18-1027 Col., Escandon, Delegacion Miguel Hidalgo, C.P. 11801 Mexico, D.F. (Mexico)

    2009-03-15

    Boehmite was synthesized and characterized in order to study the adsorption behavior and the removal of Cr(VI) ions from aqueous solutions as a function of contact time, initial pH solution, amount of adsorbent and initial metal ion concentration, using batch technique. Adsorption data of Cr(VI) on the boehmite were analyzed according to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) adsorption models. Thermodynamic parameters for the adsorption system were determinated at 293, 303, 313 and 323 K temperatures. The kinetic values and thermodynamic parameters from the adsorption process show that the Cr(VI) ions adsorption on boehmite is an endothermic and spontaneous process. These results show that the boehmite could be considered as a potential adsorbent for chromium ions in aqueous solutions.

  19. Adsorption of dyes onto activated carbon prepared from olive stones

    Souad NAJAR-SOUISSI; Abdelmottaleb OUEDERNI; Abdelhamid RATEL

    2005-01-01

    Activated carbon was produced from olive stones(OSAC) by a physical process in two steps. The adsorption character of this activated carbon was tested on three colour dyes molecules in aqueous solution: Methylene blue(MB), Rhodamine B(RB) and Congo Red(CR). The adsorption equilibrium was studied through isotherms construction at 30℃, which were well described by Langmuir model.The adsorption capacity on the OSAC was estimated to be 303 mg/g, 217 mg/g and 167 mg/g respectively for MB, RB and CR. This activated carbon has a similar adsorption properties to that of commercial ones and show the same adsorption performances. The adsorption kinetics of the MB molecule in aqueous solution at different initial concentrations by OSAC was also studied. Kinetic experiments were well fitted by a simple intra-particle diffusion model. The measured kinetics constant was influenced by the initial concentration and we found the following correlation: Kid = 1.55 C00.51 .

  20. A REVIEW OF HEAVY METAL ADSORPTION BY MARINE ALGAE

    2000-01-01

    Accumulation of heavy metals by algae had been studied extensively for biomonitoring or bioremediation purposes. Having the advantages of low cost raw material, big adsorbing capacity, no secondary pollution, etc., algae may be used to treat industrial water containing heavy metals. The adsorption processes were carried out in two steps: rapid physical adsorption first, and then slow chemical adsorption. pH is the major factor influencing the adsorption. The Freundlich equation fitted very well the adsorption isotherms. The uptake decreased with increasing ionic strength. The principal mechanism of metallic cation sequestration involves the formation of complexes between a metal ion and functional groups on the surface or inside the porous structure of the biological material. The carboxyl groups of alginate play a major role in the complexation. Different species of algae and the algae of the same species may have different adsorption capacity. Their selection affinity for heavy metals was the major criterion for the screening of a biologic adsorbent to be used in water treatment. The surface complex formation model (SCFM) can solve the equilibrium and kinetic problems in the biosorption.

  1. Adsorption of polyhydroxyl based surfactants

    Matsson, Maria

    2005-01-01

    Adsorption on solid surfaces from solution is a fundamental property of a surfactant. It might even be the most important aspect of surfactant behavior, since it influences many applications, such as cleaning, detergency, dispersion, separation, flotation, and lubrication. Consequently, fundamental investigations of surfactant adsorption are relevant to many areas. The main aim of this thesis has been to elucidate the adsorption properties, primarily on the solid/water interface, of a particu...

  2. Adsorption and collective paramagnetism

    Selwood, Pierce W

    1962-01-01

    Adsorption and Collective Paramagnetism describes a novel method for studying chemisorption. The method is based on the change in the number of unpaired electrons in the adsorbent as chemisorption occurs. The method is applicable to almost all adsorbates, but it is restricted to ferromagnetic adsorbents such as nickel, which may be obtained in the form of very small particles, that is to say, to ferromagnetic adsorbents with a high specific surface. While almost all the data used illustratively have been published elsewhere this is the first complete review of the subject. The book is addresse

  3. Adsorption de composés organiques volatils et régénération de charbons actifs - Developpement d'outils de simulation

    Ramalingam, Shivaji Ganesan

    2012-01-01

    Organic vapors emitted from solvents used in chemical / food / pharmaceutical processes, or from hydrocarbon fuel storage stations at oil terminals, can be efficiently captured by adsorption onto activated carbon beds. The overall objective of the research program is the experimental and simulation studies of the adsorption and regeneration steps in the case of VOC removal which accounts into industrial emissions by Temperature Swing Adsorption (TSA) and Vacuum Temperature Swing Adsorption (V...

  4. Modeling two-rate adsorption kinetics: Two-site, two-species, bilayer and rearrangement adsorption processes.

    Tripathi, Sumit; Tabor, Rico F

    2016-08-15

    The adsorption kinetics of many systems show apparent two-rate processes, where there appears to be resolved fast and slow adsorption steps. Such non-standard adsorption processes cannot be accounted for by conventional modeling methods, motivating new approaches. In this work, we present four different models that can account for two-rate adsorption and are based upon physically realistic processes - two adsorbing species, two surface sites having different energies, bilayer formation and molecular rearrangement modes. Each model is tested using a range of conditions, and the characteristic behavior is explored and compared. In these models, the effects of mass transport and bulk concentration are also accounted for, making them applicable in systems which are transport-limited or attachment-limited, or intermediate between the two. The applicability of these models is demonstrated by fitting exemplar experimental data for each of the four models, selecting the model on the basis of the known physical behavior of the adsorption kinetics. These models can be applied in a wide range of systems, from stagnant adsorption in large volume water treatment to highly dynamic flow conditions relevant to printing, coating and processing applications. PMID:27209397

  5. Mass Transfer Studies on Adsorption of Phenol from Wastewater Using Lantana camara, Forest Waste

    C. R. Girish

    2016-01-01

    Full Text Available Adsorption is one of the important treatment methods for the removal of pollutants from wastewater. The determination of rate controlling step in the process is important in the design of the process. Therefore, in the present work, mass transfer studies were done to evaluate the rate-limiting step in the adsorption of phenol from aqueous solution onto Lantana camara. Different mass transfer models were used to find the rate-limiting step and also to find the values of external mass transfer coefficient and diffusion coefficient. The Biot number was found to investigate the importance of external mass transfer to intraparticle diffusion. From the various models studied and the Biot numbers obtained, it was found that the adsorption on Lantana camara was controlled by film diffusion. The sensitivity analysis was performed to study the significance of the model parameters on the adsorption process.

  6. Extremely high negative electron affinity of diamond via magnesium adsorption

    O'Donnell, Kane M.; Edmonds, Mark T.; Tadich, Anton; Thomsen, Lars; Stacey, Alastair; Schenk, Alex; Pakes, Chris I.; Ley, Lothar

    2015-01-01

    We report large negative electron affinity (NEA) on diamond (100) using magnesium adsorption on a previously oxygen-terminated surface. The measured NEA is up to $(-2.01\\pm0.05)$ eV, the largest reported negative electron affinity to date. Despite the expected close relationship between the surface chemistry of Mg and Li species on oxygen-terminated diamond, we observe differences in the adsorption properties between the two. Most importantly, a high-temperature annealing step is not required...

  7. Double-Stranded Water on Stepped Platinum Surfaces

    Kolb, Manuel J.; Farber, Rachael G.; Derouin, Jonathan; Badan, Cansin; Calle-Vallejo, Federico; Juurlink, Ludo B. F.; Killelea, Daniel R.; Koper, Marc T. M.

    2016-04-01

    The interaction of platinum with water plays a key role in (electro)catalysis. Herein, we describe a combined theoretical and experimental study that resolves the preferred adsorption structure of water wetting the Pt(111)-step type with adjacent (111) terraces. Double stranded lines wet the step edge forming water tetragons with dissimilar hydrogen bonds within and between the lines. Our results qualitatively explain experimental observations of water desorption and impact our thinking of solvation at the Pt electrochemical interface.

  8. Removal of furan and phenolic compounds from simulated biomass hydrolysates by batch adsorption and continuous fixed-bed column adsorption methods.

    Lee, Sang Cheol; Park, Sunkyu

    2016-09-01

    It has been proposed to remove all potential inhibitors and sulfuric acid in biomass hydrolysates generated from dilute-acid pretreatment of biomass, based on three steps of sugar purification process. This study focused on its first step in which furan and phenolic compounds were selectively removed from the simulated hydrolysates using activated charcoal. Batch adsorption experiments demonstrated that the affinity of activated charcoal for each component was highest in the order of vanillic acid, 4-hydroxybenzoic acid, furfural, acetic acid, sulfuric acid, and xylose. The affinity of activated charcoal for furan and phenolic compounds proved to be significantly higher than that of the other three components. Four separation strategies were conducted with a combination of batch adsorption and continuous fixed-bed column adsorption methods. It was observed that xylose loss was negligible with near complete removal of furan and phenolic compounds, when at least one fixed-bed column adsorption was implemented in the strategy. PMID:27289057

  9. Liquid-Phase Adsorption Fundamentals.

    Cooney, David O.

    1987-01-01

    Describes an experiment developed and used in the unit operations laboratory course at the University of Wyoming. Involves the liquid-phase adsorption of an organic compound from aqueous solution on activated carbon, and is relevant to adsorption processes in general. (TW)

  10. Impact of biochar produced from post-harvest residue on the adsorption behavior of diesel oil on loess soil.

    Jiang, Yu Feng; Sun, Hang; Yves, Uwamungu J; Li, Hong; Hu, Xue Fei

    2016-02-01

    The primary objective of this study was to investigate the effect of biochar, produced from wheat residue at different temperatures, on the adsorption of diesel oil by loess soil. Kinetic and equilibrium data were processed to understand the adsorption mechanism of diesel by biochar-affected loess soil; dynamic and thermodynamic adsorption experiments were conducted to characterize this adsorption. The surface features and chemical structure of biochar, modified at varying pyrolytic temperatures, were investigated using surface scanning electron microscopy and Fourier transform infrared analysis. The kinetic data showed that the adsorption of diesel oil onto loess soil could be described by a pseudo-second-order kinetic model, with the rate-controlling step being intraparticle diffusion. However, in the presence of biochar, boundary layer control and intraparticle diffusion were both involved in the adsorption. Besides, the adsorption equilibrium data were well described by the Freundlich isothermal model. The saturated adsorption capacity weakened as temperature increased, suggesting a spontaneous exothermic process. Thermodynamic parameter analysis showed that adsorption was mainly a physical process and was enhanced by chemical adsorption. The adsorption capacity of loess soil for diesel oil was weakened with increasing pH. The biochar produced by pyrolytic wheat residue increased the adsorption behavior of petroleum pollutants in loess soil. PMID:25980560

  11. Effect of effluent organic matter on the adsorption of perfluorinated compounds onto activated carbon

    Yu, Jing [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210046 (China); College of Environmental Science and Engineering, Yangzhou University, 196 West Huayang Road, Yangzhou 225127 (China); Lv, Lu, E-mail: esellu@nju.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210046 (China); Lan, Pei [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210046 (China); College of Environmental Science and Engineering, Yangzhou University, 196 West Huayang Road, Yangzhou 225127 (China); Zhang, Shujuan [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210046 (China); Pan, Bingcai, E-mail: bcpan@nju.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210046 (China); Zhang, Weiming [State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210046 (China)

    2012-07-30

    Highlights: Black-Right-Pointing-Pointer The presence of EfOM significantly reduced the adsorption capacities and rates of PFCs. Black-Right-Pointing-Pointer Low-molecular-weight EfOM compounds (<1 kDa) compete for adsorption sites of PFSs directly. Black-Right-Pointing-Pointer Large-molecular-weight EfOM compounds (>30 kDa) affect the adsorption through pore blockage or restriction effect. Black-Right-Pointing-Pointer Changes in surface properties of PAC caused by preloaded EfOM could affect PFCs adsorption. - Abstract: Effect of effluent organic matter (EfOM) on the adsorption of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) onto powdered activated carbon (PAC) was quantitatively investigated at environmentally relevant concentration levels. The adsorption of both perfluorinated compounds (PFCs) onto PAC followed pseudo-second order kinetics and fitted the Freundlich model well under the given conditions. Intraparticle diffusion was found to be the rate-controlling step in the PFC adsorption process onto PAC in the absence and presence of EfOM. The presence of EfOM, either in PFC-EfOM simultaneous adsorption onto fresh PAC or in PFC adsorption onto EfOM-preloaded PAC, significantly reduced the adsorption capacities and sorption rates of PFCs. The pH of zero point of charge was found to be 7.5 for fresh PAC and 4.2 for EfOM-preloaded PAC, suggesting that the adsorbed EfOM imparted a negative charge on PAC surface. The effect of molecular weight distribution of EfOM on the adsorption of PFCs was investigated with two EfOM fractions obtained by ultrafiltration. The low-molecular-weight compounds (<1 kDa) were found to be the major contributors to the significant reduction in PFC adsorption capacity, while large-molecular-weight compounds (>30 kDa) had much less effect on PFC adsorption capacity.

  12. Comparative study of cesium adsorption on dioctahedral and trioctahedral smectites

    Bentonites which are characterized by good rheological, mineralogical and chemical stability is considered used as sealing barriers in multibarrier Slovak system of deep geological repository for high-level radioactive waste and spent nuclear fuel. In Slovak Republic there are several significant deposits of bentonite, which are characterized by appropriate adsorption properties and meet the geotechnical requirements for this type of barriers. Study of adsorption properties of bentonites and other smectites is an essential step for developing the migration model long-lived corrosion and activation products, and fission products of uranium. Nuclear wastes contain the most important nuclear fission products, radioisotopes 134Cs and 137Cs. The present paper investigates and compares the cesium adsorption properties of Slovak and North America bentonites composed mainly of dioctahedral smectite montmorillonite (J, L, SAz-1 and STx-1) and trioctahedral smectites saponite (SapCa-2) and hectorite (SHCa-1). (author)

  13. Experimental studies on irreversibility of electrostatic adsorption of silica nanoparticles at solid-liquid interface.

    Li, Xue; Niitsoo, Olivia; Couzis, Alexander

    2014-04-15

    Adsorption of colloidal nanoparticles (NPs) at solid-liquid interface is a scientifically interesting and technologically important phenomenon due to its fundamental importance in many industrial, environmental, and biological processes, such as wastewater treatment, printing, coating of surfaces, chromatography, papermaking, or biocompatibility. The process is well understood theoretically by the random sequential adsorption (RSA) model, based on the assumption of irreversible adsorption. Irreversible adsorption is defined as a process in which, once adsorbed, a particle can neither desorb, nor to move laterally on the surface. However, published experimental data that verifies the irreversibility of particle adsorption are very limited. In this study, we demonstrate the irreversibility of electrostatically driven nanoparticle adsorption utilizing a carefully selected set of experiments. A simple method was employed by uniquely introducing Ag@SiO2 core/shell NPs to perform exchange adsorptions experiments. Stöber SiO2 NPs with a diameter of 50-80 nm were initially electrostatically adsorbed onto amino-functionalized silicon wafer substrates followed by the subsequent adsorption of Ag@SiO2 NPs. The Ag@SiO2 NPs have the same surface chemistry as the neat SiO2 NPs. For the second step the adsorption time was varied from 1 min to 1 week so as to get a thorough understanding of the process irreversibility. Surface coverage quantification has shown that the surface coverage of the initially adsorbed SiO2 NPs stays the same independent of the duration of the second step adsorption using the Ag@SiO2 core/shell NPs. This observation directly confirms the irreversibility of electrostatic adsorption of NPs. PMID:24559699

  14. Computational Abstraction Steps

    Thomsen, Lone Leth; Thomsen, Bent; Nørmark, Kurt

    2010-01-01

    In this paper we discuss computational abstraction steps as a way to create class abstractions from concrete objects, and from examples. Computational abstraction steps are regarded as symmetric counterparts to computational concretisation steps, which are well-known in terms of function calls and...... capturing concrete values, objects, or actions. As the next step, some of these are lifted to a higher level by computational means. In the object-oriented paradigm the target of such steps is classes. We hypothesise that the proposed approach primarily will be beneficial to novice programmers or during the...

  15. Step by Step Microsoft Office Visio 2003

    Lemke, Judy

    2004-01-01

    Experience learning made easy-and quickly teach yourself how to use Visio 2003, the Microsoft Office business and technical diagramming program. With STEP BY STEP, you can take just the lessons you need, or work from cover to cover. Either way, you drive the instruction-building and practicing the skills you need, just when you need them! Produce computer network diagrams, organization charts, floor plans, and moreUse templates to create new diagrams and drawings quicklyAdd text, color, and 1-D and 2-D shapesInsert graphics and pictures, such as company logosConnect shapes to create a basic f

  16. Adsorption of PTCDA on NaCl(100) and KCl(100)

    Aldahhak, H.; Schmidt, W. G.; Rauls, E.

    2013-11-01

    The adsorption of PTCDA on KCl and NaCl(100) surfaces has been investigated by means of first principles calculations. Besides a variety of adsorbate structures for single molecules and a monolayer of flat lying molecules on plain terraces, the influence of monoatomic steps and the different defect site at step edges has been studied in detail.

  17. Adsorption of Atenolol on Kaolinite

    Yingmo Hu

    2015-01-01

    Full Text Available In this study the adsorption of atenolol (AT, a β-blocker, on kaolinite, a clay mineral of low surface charge, was investigated under varying initial AT concentration, equilibrium time, solution pH, ionic strength, and temperature conditions. The results showed that the amounts of AT uptake by kaolinite were close to its cation exchange capacity value and the AT adsorption was almost instantaneous, suggesting a surface adsorption. The adsorption was exothermic and the free energy of adsorption was small negative, indicating physical adsorption. The increase in ionic strength of the solution drastically reduced AT uptake on kaolinite. A significant reduction in AT uptake was found at solution pH below 5 or above 10. The FTIR results showed band shifting and disappearance for NH bending vibration and benzene ring skeletal vibration at 3360 and 1515 cm−1 and band splitting at 1412 and 1240 cm−1 attributed to C–N valence vibration coupled with NH bending vibrations and alkyl aryl ether linkage, suggesting the participation of NH, –O–, and benzene ring for AT adsorption on kaolinite.

  18. Adsorption Desalination: A Novel Method

    Ng, Kim Choon

    2010-11-15

    The search for potable water for quenching global thirst remains a pressing concern throughout many regions of the world. The demand for new and sustainable sources and the associated technologies for producing fresh water are intrinsically linked to the solving of potable water availability and hitherto, innovative and energy efficient desalination methods seems to be the practical solutions. Quenching global thirst by adsorption desalination is a practical and inexpensive method of desalinating the saline and brackish water to produce fresh water for agriculture irrigation, industrial, and building applications. This chapter provides a general overview of the adsorption fundamentals in terms of adsorption isotherms, kinetics, and heat of adsorption. It is then being more focused on the principles of thermally driven adsorption desalination methods. The recent developments of adsorption desalination plants and the effect of operating conditions on the system performance in terms of specific daily water production and performance ratio are presented. Design of a large commercial adsorption desalination plant is also discussed herein.

  19. Adsorption of polymeric brushes: Bridging

    Johner, Albert; Joanny, Jean-François

    1992-04-01

    We study the adsorption of grafted polymer layers on a planar surface parallel to the grafting surface. The layer consists of two types of chains: nonadsorbed chains with a free end and adsorbed chains forming bridges between the two plates. In the limit of strong adsorption a dead zone exists in the vicinity of the adsorbing plate; its size increases with the adsorption strength. Two adsorption mechanisms are possible: adsorption of the last monomer only and adsorption of all the monomers. In both cases the adsorption regimes at equilibrium (when no external force acts on the plates) are discussed within the framework of the self-consistent mean-field theory. We also give scaling laws taking into account excluded volume correlations. Finally, we consider situations where a finite external force, either tangential or normal to the plates, is applied on the adsorbing plate. Pulling and tangential forces both reduce the fraction of bridges and eventually lead to rupture, whereas compressional forces favor bridging. For normal forces, force vs distance profiles between planes and crossed cylinders are given.

  20. Adsorption of Oxaliplatin by Hydroxyapatite

    Papageorgiou A.

    2007-12-01

    Full Text Available Hydroxyapatite (HAP is the main inorganic component of human skeleton. The last years a lot of interest is focused on its use as drug carrier. In this work the in vitro adsorption of the anti-cancer drug oxaliplatin, by HAP, from its aqueous solution was studied. Various initial concentrations of oxaliplatin aqueous solutions were used in order to determine the maximum adsorption capacity of HAP. Oxaliplatin's concentrations were determined through Pt determinations by atomic absorption spectrometry with flame technique, in the equilibrated solutions after shaking for 48 hours and filtering the HAP-oxaliplatin slurries. The maximum adsorption capacity was found to be 49.1 mg oxaliplatin/g HAP. In order to determine the time needed for the maximum adsorption to be achieved, six oxaliplatin - HAP slurries were prepared. The slurries had initial oxaliplatin concentrations the one that corresponds to the maximum adsorption capacity of the HAP added. The oxaliplatin determination was carried out after 0, 10, 20, 30, 40 and 48 hours in each different slurry. The maximum adsorption capacity was achieved after 20 hours. The adsorption of oxaliplatin by HAP was found to follow the Freundlich equation.

  1. Characteristic Evaluation of Graphene Oxide for Bisphenol A Adsorption in Aqueous Solution

    Thatchaphong Phatthanakittiphong

    2016-07-01

    Full Text Available This paper investigates the characteristics of graphene oxide (GO for Bisphenol A (BPA adsorption in water. Batch experiments on the influence of significant parameters were performed. While an improvement of the adsorption capacity of BPA was obtained by the increment of contact time and the initial BPA concentration, the increment of pH above 8, GO dosage, and temperature showed the reverse results. The thermodynamic study suggested that BPA adsorption on GO was an exothermic and spontaneous process. The kinetics was explained by the pseudo-second-order model which covers all steps of adsorption. The fit of the results with the Langmuir isotherm indicated the monolayer adsorption. At 298 K, the adsorption reached equilibrium within 30 min with the maximum adsorption capacity of 49.26 mg/g. The low BPA adsorption capacity of GO can be interpreted by the occurrence of oxygen-containing functional groups (OCFGs that are able to form hydrogen bonds with the surrounding OCFGs and water molecules. This effect inhibited the role of π–π interactions that are mainly responsible for the adsorption of BPA.

  2. Diabetes PSA (:30) Step By Step

    2009-10-24

    First steps to preventing diabetes. For Hispanic and Latino American audiences.  Created: 10/24/2009 by National Diabetes Education Program (NDEP), a joint program of the Centers for Disease Control and Prevention and the National Institutes of Health.   Date Released: 10/24/2009.

  3. Diabetes PSA (:60) Step By Step

    2009-10-24

    First steps to preventing diabetes. For Hispanic and Latino American audiences.  Created: 10/24/2009 by National Diabetes Education Program (NDEP), a joint program of the Centers for Disease Control and Prevention and the National Institutes of Health.   Date Released: 10/24/2009.

  4. Dynamics and adsorption of gas molecules using proton beams

    Meso sized MgO powders and single walled and multiwalled Carbon NanoTubes (CNT) were radiated by proton beams with energy of 10-35 MeV for 30 seconds, and Ar gas adsorption experiments were carried. Any significant difference in adsorption properties of Ar at 77K was measured from the MgO powders radiated 10 MeV for 30 seconds. The single walled CNT samples, however, exhibit significant changes of adsorption curves including reduction of the adsorption amount and disappearing of the second step, while multiwalled CNTs show no difference in adsorption behavior. Interestingly, all CNTs including singlewalled and multiwalled CNTs, that were radiated by proton beams with energy 35 MeV at the Bragg peak position contain much less Fe, Ni catalysts which were presumably products of the sample preparation process. Based on this result, the method on purification of CNTs is applied for the domestic patent. The fundamental mechanism on the purification, however, is not clear and needs further studies

  5. Carbon nanomaterials for gas adsorption

    Terranova, Maria Letizia

    2012-01-01

    Research in adsorption of gases by carbon nanomaterials has experienced considerable growth in recent years, with increasing interest for practical applications. Many research groups are now producing or using such materials for gas adsorption, storage, purification, and sensing. This book provides a selected overview of some of the most interesting scientific results regarding the outstanding properties of carbon nanomaterials for gas adsorption and of interest both for basic research and technological applications. Topics receiving special attention in this book include storage of H, purific

  6. Cyclic steps on ice

    Yokokawa, M.; Izumi, N.; Naito, K.; Parker, G.; Yamada, T.; Greve, R.

    2016-05-01

    Boundary waves often form at the interface between ice and fluid flowing adjacent to it, such as ripples under river ice covers, and steps on the bed of supraglacial meltwater channels. They may also be formed by wind, such as the megadunes on the Antarctic ice sheet. Spiral troughs on the polar ice caps of Mars have been interpreted to be cyclic steps formed by katabatic wind blowing over ice. Cyclic steps are relatives of upstream-migrating antidunes. Cyclic step formation on ice is not only a mechanical but also a thermodynamic process. There have been very few studies on the formation of either cyclic steps or upstream-migrating antidunes on ice. In this study, we performed flume experiments to reproduce cyclic steps on ice by flowing water, and found that trains of steps form when the Froude number is larger than unity. The features of those steps allow them to be identified as ice-bed analogs of cyclic steps in alluvial and bedrock rivers. We performed a linear stability analysis and obtained a physical explanation of the formation of upstream-migrating antidunes, i.e., precursors of cyclic steps. We compared the results of experiments with the predictions of the analysis and found the observed steps fall in the range where the analysis predicts interfacial instability. We also found that short antidune-like undulations formed as a precursor to the appearance of well-defined steps. This fact suggests that such antidune-like undulations correspond to the instability predicted by the analysis and are precursors of cyclic steps.

  7. The corrosive influence of chloride ions preference adsorption on α-Al2O3 (0 0 0 1) surface

    Graphical abstract: - Highlights: • The preference adsorption and interaction of Cl− at increasing monolayer coverage on Al2O3 in solution environment are modeling by DFT with COSMO. • A redefinition critical one plane monolayer of Cl− is 3/7, and the adsorption energy decrease in three steps, each adsorption energy step only relate to the adsorption site and the morphology. • The weaker interaction between Cl− and Al2O3 surface but stronger interactions between three Cl− make the electrons uniformly occupy on the energy levels of three ions. - Abstract: Conductor-like screening model (COSMO), Periodic DFT calculations have been performed on a Al2O3 surface to model the influence of preference adsorption and interaction of chloride ions at increasing monolayer coverage on undefective passive film on Aluminum in solution environment. The results evidence that the critical monolayer of Cl− is 3/7, which is redefined. With increasing Cl− adsorption, both the first and second Cl− move from Al(1) atop and bridge10 sites to O(5) sites, suggesting that the weaker interaction between Cl− and Al2O3 surface but stronger interactions between three ions make the electrons uniformly occupy on the energy levels of them. More calculations shows that the preference adsorption sites of Cl− are independent of the surface area of oxide, and the adsorption energy decrease in three steps, each adsorption energy step only relate to the adsorption site and the morphology. On undefective oxide film, low coverage Cl− adsorption would restrain surface breakdown to happen which is consistent with the experiment results

  8. Equilibrium models and kinetic for the adsorption of methylene blue on Co-hectorites

    The adsorption of methylene blue (MB) onto the surface of cobalt doping hectorite (Co-hectorite) was systematically studied. The physical properties of Co-hectorites were investigated, where characterizations were carried out by X-ray diffraction (XRD) and Electron Diffraction Spectrum (EDS) techniques, and morphology was examined by nitrogen adsorption. The sample with a Co content 5% (m/m) had a higher specific surface area than other Co-hectorites. The pore diameters were distributed between 2.5 and 5.0 nm. The adsorption results revealed that Co-hectorite surfaces possessed effective interactions with MB and bases, and greatest adsorption capacity achieved with Co content 5%, where the best-fit isotherm model was the Langmuir adsorption model. Kinetic studies were fitted to the pseudo-second-order kinetic model. The intraparticle diffusion was not the rate-limiting step for the whole reaction.

  9. Equilibrium isotherm and kinetics modeling of U(VI) adsorption by natural soil systems

    This research examined the adsorption capability of natural soils of different origin for U(VI) at soil-water interface and the mechanism involved. Adsorption kinetics study indicates that adsorption followed the pseudo-second order kinetics irrespective of soil types and was not solely controlled by the diffusion step rather surface complexation and ion-exchange plays major role. Study of adsorption isotherms indicates adsorption involves chemisorption and soil with high Fe and Mn content better fit to Langmuir model. The study provides a better insight for site selection for radioactive waste (uranium) disposal facilities as well as soil suitable for back fill or permeable reactive barrier to inhibit migration of U(VI). (author)

  10. Microsoft Office Word 2007 step by step

    Cox, Joyce

    2007-01-01

    Experience learning made easy-and quickly teach yourself how to create impressive documents with Word 2007. With Step By Step, you set the pace-building and practicing the skills you need, just when you need them!Apply styles and themes to your document for a polished lookAdd graphics and text effects-and see a live previewOrganize information with new SmartArt diagrams and chartsInsert references, footnotes, indexes, a table of contentsSend documents for review and manage revisionsTurn your ideas into blogs, Web pages, and moreYour all-in-one learning experience includes:Files for building sk

  11. Golgi-Cox Staining Step by Step

    Zaqout, Sami; Kaindl, Angela M.

    2016-01-01

    Golgi staining remains a key method to study neuronal morphology in vivo. Since most protocols delineating modifications of the original staining method lack details on critical steps, establishing this method in a laboratory can be time-consuming and frustrating. Here, we describe the Golgi-Cox staining in such detail that should turn the staining into an easily feasible method for all scientists working in the neuroscience field.

  12. Golgi-Cox staining step by step

    Sami eZaqout; Kaindl, Angela M.

    2016-01-01

    Golgi staining remains a key method to study neuronal morphology in vivo. Since most protocols delineating modifications of the original staining method lack details on critical steps, establishing this method in a laboratory can be time-consuming and frustrating. Here, we describe the Golgi-Cox staining in such detail that should turn the staining into an easily feasible method for all scientists working in the neuroscience field.

  13. Molecular adsorption on graphene

    Kong, Lingmei; Enders, Axel; Rahman, Talat S.; Dowben, Peter A.

    2014-11-01

    Current studies addressing the engineering of charge carrier concentration and the electronic band gap in epitaxial graphene using molecular adsorbates are reviewed. The focus here is on interactions between the graphene surface and the adsorbed molecules, including small gas molecules (H2O, H2, O2, CO, NO2, NO, and NH3), aromatic, and non-aromatic molecules (F4-TCNQ, PTCDA, TPA, Na-NH2, An-CH3, An-Br, Poly (ethylene imine) (PEI), and diazonium salts), and various biomolecules such as peptides, DNA fragments, and other derivatives. This is followed by a discussion on graphene-based gas sensor concepts. In reviewing the studies of the effects of molecular adsorption on graphene, it is evident that the strong manipulation of graphene’s electronic structure, including p- and n-doping, is not only possible with molecular adsorbates, but that this approach appears to be superior compared to these exploiting edge effects, local defects, or strain. However, graphene-based gas sensors, albeit feasible because huge adsorbate-induced variations in the relative conductivity are possible, generally suffer from the lack of chemical selectivity.

  14. Protein Adsorption in Three Dimensions

    Vogler, Erwin A.

    2011-01-01

    Recent experimental and theoretical work clarifying the physical chemistry of blood-protein adsorption from aqueous-buffer solution to various kinds of surfaces is reviewed and interpreted within the context of biomaterial applications, especially toward development of cardiovascular biomaterials. The importance of this subject in biomaterials surface science is emphasized by reducing the “protein-adsorption problem” to three core questions that require quantitative answer. An overview of the...

  15. Amphiphile Adsorption on Rigid Polyelectrolytes

    Kuhn, Paulo S.; Levin, Yan; Barbosa, Marcia C.; Ravazzolo, Ana Paula

    2007-01-01

    A theory is presented which quantitatively accounts for the cooperative adsorption of cationic surfactants to anionic polyelectrolytes. For high salt concentration we find that the critical adsorption concentration (CAC) is a bilinear function of the polyion monomer and salt concentrations, with the coefficients dependent only on the type of surfactant used. The results presented in the paper might be useful for designing more efficient gene delivery systems.

  16. Weak adsorption and prewetting transitions

    We review the theory of prewetting and wetting transitions in relation to recent studies of noble gas and H2 adsorption on alkali metal surfaces. An essential feature is that the adsorption potential have extremely small well depths. Open theoretical issues include the accuracy of the potentials, the approximations used in the statistical mechanics, and dynamic effects of the substrate. New adsorbates and substrates are discussed. (orig.)

  17. Study of Hydrogen Adsorption on Pt/WO3-ZrO2 through Pt Sites

    Sugeng Triwahyono; Aishah Abdul Jalil; Hideshi Hattori

    2007-01-01

    The rate determining step and the energy barrier involved in hydrogen adsorption on Pt/WO3ZrO2 were studied based on the assumption that the hydrogen adsorption occurs only through Pt sites.The rate of hydrogen adsorption on Pt/WO3-ZrO2 Was measured in the adsorption temperature range of 323-573 K and an initial hydrogen pressure of 50 Torr.The rates of hydrogen uptake were very high for the initial few minutes and the adsorption continued for more than 5 h below 523 K.The hydrogen uptake far exceeded the H/Pt ratio of unity for all adsorption temperatures,indicating that the adsorption of hydrogen involved the dissociative adsorption of hydrogen on Pt sites to form hydrogen atoms.the spillover of hydrogen atoms onto the surface of the WO3-ZrO2 catalyst.the diffusion of spiltover hydrogen atom over the surface of the WO3-ZrO2 catalyst,and the formation of protonic acid site originated from hydrogen atom by releasing an electron in which the electron may react with a second hydrogen atom to form a hydride near the Lewis acid site.The rate determining step was the spillover with the activation energy of 12.3 kJ/mol.The rate of hydrogen adsorption cannot be expressed by the rate equation based on the assumption that the rate determining step is the surface diffusion.The activity of Pt/WO3-ZrO2 Was examined on n-heptane isomerization in which the increase of hydrogen partial pressure provided positive-effect on the conversion of n-heptane and negative-effect on the selectivity towards iso-heptane.

  18. Statistical mechanical lattice models of endohedral and exohedral xenon adsorption in carbon nanotubes and comparison with Monte-Carlo simulations

    Adsorption of xenon in carbon nanotubes has been investigated by Kuznetsova et al. [A. Kuznetsova, J.T. Yates Jr., J. Liu, R.E. Smalley, J. Chem. Phys. 112 (2000) 9590] and Simonyan et al. [V. Simonyan, J.K. Johnson, A Kuznetsova, J.T. Yates Jr., J. Chem. Phys. 114 (2001) 4180] where endohedral adsorption isotherms show a step-like structure. A matrix method is used for calculation of the statistical mechanics of a lattice model of xenon endohedral adsorption which reproduces the isotherm structure while exohedral adsorption is treated by mean-field theory

  19. What Governs Protein Adsorption and Immobilization at a Charged Solid Surface?

    Kubiak-Ossowska, Karina; Mulheran, Paul A.

    2010-01-01

    The adsorption of hen egg white lysozyme at a model charged surface is studied using fully atomistic molecular dynamics simulations. The simulations are performed over a 90 ns time scale which is sufficient to observe rotational and translational steps in the adsorption process. Electrostatics is found to play a key role in guiding the protein to the favorable binding orientation with the N,C-terminal face against the substrate. However, full immobilization appears to only occur through the s...

  20. Cryogenic Adsorption of Low-concentration Hydrogen on 5A Molecular Sieve Bed

    LIU; Zhen-xing; YANG; Hong-guang; XIA; Ti-rui; ZHAN; Qin; YANG; Li-ling

    2013-01-01

    The separation of low-concentration hydrogen isotopes from helium is a processing step that is required for ceramic lithium breeding blanket processing.In this study,the adsorption of low-concentration hydrogen from helium carrier was measured using 5A molecular sieve fixed bed in the cryogenic condition.The adsorption performances of hydrogen on 5A molecular sieve were discussed.The effect of the different

  1. ADSORPTION OF POLYCHLORINATED BIPHENYLS BY SOILS

    Mihaela Preda; Radu Lăcătuşu; Dumitru Marian Motelică; Nicoleta Vrînceanu; Veronica Tănase

    2010-01-01

    The behavior of polychlorinated biphenyls (PCBs) in soil is determined by several factors including adsorption, mobility and degradation. Adsorption, directly or indirectly, influences the other factors. Adsorption process is generally evaluated by using adsorption isotherms representing the relationship between the quantity of substance adsorbed per unit weight and concentration of the substance in solution at equilibrium. They allow determination of the adsorption constant, which is directl...

  2. Adsorption refrigeration technology theory and application

    Wang, Ruzhu; Wu, Jingyi

    2014-01-01

    Gives readers a detailed understanding of adsorption refrigeration technology, with a focus on practical applications and environmental concerns Systematically covering the technology of adsorption refrigeration, this book provides readers with a technical understanding of the topic as well as detailed information on the state-of-the-art from leading researchers in the field. Introducing readers to background on the development of adsorption refrigeration, the authors also cover the development of adsorbents, various thermodynamic theories, the design of adsorption systems and adsorption refri

  3. Scaling properties of adsorption energies for hydrogen-containing molecules on transition-metal surfaces

    Abild-Pedersen, Frank; Greeley, Jeffrey Philip; Studt, Felix;

    2007-01-01

    Density functional theory calculations are presented for CHx, x=0,1,2,3, NHx, x=0,1,2, OHx, x=0,1, and SHx, x=0,1 adsorption on a range of close-packed and stepped transition-metal surfaces. We find that the adsorption energy of any of the molecules considered scales approximately with the adsorp...... adsorption energy of the central, C, N, O, or S atom, the scaling constant depending only on x. A model is proposed to understand this behavior. The scaling model is developed into a general framework for estimating the reaction energies for hydrogenation and dehydrogenation reactions....

  4. Role of crystal size on swing-effect and adsorption induced structure transition of ZIF-8.

    Tian, Tian; Wharmby, Michael T; Parra, José B; Ania, Conchi O; Fairen-Jimenez, David

    2016-04-19

    The flexibility and structure transition behaviour of ZIF-8 in a series of samples with different particle size has been studied using a combination of high-resolution N2 gas adsorption isotherms and, for the first time, a broad in situ PXRD and Rietveld analysis. During the stepped adsorption process, large particles showed a narrow adsorption/desorption pressure range with a shorter equilibrium time due to lower kinetic hindrance, deriving from higher amount of active sites. In situ PXRD showed that both the rotation of imidazole ring and a bend in the methyl group led to the gate opening of ZIF-8. PMID:26948119

  5. Adsorption and activation of methane and methanol on Pt(100) surface: a density functional study

    The activation of methane (CH4) and methanol (CH3OH) on Pt(100) surface has been investigated using density functional theory calculations based on plane-wave basis and pseudo-potential. We optimised CH4/Pt(100) system. The calculated adsorption energies over the top, bridge and hollow sites are small, weakly dependent on the molecular orientation. The nature of the CH4-Pt interaction was examined through the electronic structure changes. The adsorption of methyl (CH3) and hydrogen (H) and the co-adsorption of CH3+H were also calculated. From these results, we examined the dissociation of CH4 to CH3+H, and the activation energies found are in good agreement with the experimental and theoretical values. The activation of CH3OH/Pt(100) has been studied. All the sites have almost the same adsorption energy. The adsorption of oxygen (O) and the co-adsorption of CH4 and O were also examined. In addition, the formation of CH3OH assuming a one-step mechanism step via the co-adsorption of CH4+O has been studied and the barrier height was found to be high. (authors)

  6. Effect of Humic Acid on As Redox Transformation and Kinetic Adsorption onto Iron Oxide Based Adsorbent (IBA

    Hoda Fakour

    2014-10-01

    Full Text Available Due to the importance of adsorption kinetics and redox transformation of arsenic (As during the adsorption process, the present study elucidated natural organic matter (NOM effects on As adsorption-desorption kinetics and speciation transformation. The experimental procedures were conducted by examining interactions of arsenate and arsenite with different concentrations of humic acid (HA as a model representative of NOM, in the presence of iron oxide based adsorbent (IBA, as a model solid surface in three environmentally relevant conditions, including the simultaneous adsorption of both As and HA onto IBA, HA adsorption onto As-presorbed IBA, and As adsorption onto HA-presorbed IBA. Experimental adsorption-desorption data were all fitted by original and modified Lagergren pseudo-first and -second order adsorption kinetic models, respectively. Weber’s intraparticle diffusion was also used to gain insight into the mechanisms and rate controlling steps, which the results suggested that intraparticle diffusion of As species onto IBA is the main rate-controlling step. Different concentrations of HA mediated the redox transformation of As species, with a higher oxidation ability than reduction. The overall results indicated the significant effect of organic matter on the adsorption kinetics and redox transformation of As species, and consequently, the fate, transport and mobility of As in different environmentally relevant conditions.

  7. Adsorption of lanthanum to goethite in the presence of gluconate

    Hull, Laurence C.; Sarah Pepper; Sue Clark

    2005-05-01

    Adsorption of Lanthanum to Goethite in the Presence of Gluconic Acid L. C. HULL,1 S. E. PEPPER2 AND S. B. CLARK2 1Idaho National Engineering and Environmental Laboratory, Idaho Falls, ID (hulllc@inel.gov) 2Washington State University, Pullman, WA (spepper@wsu.edu), (s_clark@wsu.edu) Lanthanide and trivalent-actinide elements in radioactive waste can pose risks to humans and ecological systems for many years. Organic complexing agents, from natural organic matter or the degradation of waste package components, can alter the mobility of these elements. We studied the effect of gluconic acid, as an analogue for cellulose degradation products, on the adsorption of lanthanum, representing lanthanide and trivalent-actinide elments, to goethite, representing natural iron minearals and degradation products of waste packages. Batch pH adsorption edge experiments were conducted with lanthanum alone, and with lanthanum and gluconate at a 1:1 mole ratio. Lanthanum concentrations studied were 0.1, 1, and 10 mM, covering a range from 10% to 1000% of the calculated available adsorption sites on goethite. In the absence of gluconate, lanthanum was primarily present in solution as free lanthanum ion. With gluconate present, free lanthanum concentration in solution decreased with increasing pH as step-wise deprotonation of the gluconate molecule increased the fraction lanthanum complexed with gluconate. Adsorption to the goethite surface was represented with the diffuse double-layer model. The number of adsorption sites and the intrinsic binding constants for the surface complexes were estimated from the pH adsorption edge data using the computer code FITEQL 4.0. Two surface reactions were used to fit the adsorption data in the absence of gluconate. A strong binding site with no proton release and a much higher concentration of weak binding sites with release of two protons per lanthanum adsorbed. The adsorption of lanthanum was not measurably affected by the presence of gluconate

  8. A New Adsorbent Composite Material Based on Metal Fiber Technology and Its Application in Adsorption Heat Exchangers

    Ursula Wittstadt

    2015-08-01

    Full Text Available In order to achieve process intensification for adsorption chillers and heat pumps, a new composite material was developed based on sintered aluminum fibers from a melt-extraction process and a dense layer of silico-aluminophosphate (SAPO-34 on the fiber surfaces. The SAPO-34 layer was obtained through a partial support transformation (PST process. Preparation of a composite sample is described and its characteristic pore size distribution and heat conductivity are presented. Water adsorption data obtained under conditions of a large pressure jump are given. In the next step, preparation of the composite was scaled up to larger samples which were fixed on a small adsorption heat exchanger. Adsorption measurements on this heat exchanger element that confirm the achieved process intensification are presented. The specific cooling power for the adsorption step per volume of composite is found to exceed 500 kW/m3 under specified conditions.

  9. Kinetically controlled growth of gallium on stepped Si (553) surface

    Kumar, Mukesh; Pasha, Syed Khalid; Govind

    2013-10-01

    Kinetically controlled growth of gallium (Ga) metal has been reported on high index stepped Si (553) surface and its thermal stability with various novel superstructural phases has been analyzed. Auger electron spectroscopy studies revealed that the adsorption of Ga at room temperature (RT) follows Frank-van der Merwe (FM) growth mode while for higher substrate temperature, Ga adsorption remains within the submonolayer range. Thermal desorption and low energy electron diffraction studies investigated the formation of thermally stable Ga-islands and the various Ga induced superstructural phase on Si (553). During room temperature adsorption, (1 1 1)7 × 7 facet of Si (553) reconstructed into (1 1 1)6 × 6 facet while during desorption process, stable (1 1 1)6 × 6 and (1 1 1)√3 × √3-R30° surface reconstructions has been observed.

  10. Kinetically controlled growth of gallium on stepped Si (553) surface

    Kinetically controlled growth of gallium (Ga) metal has been reported on high index stepped Si (553) surface and its thermal stability with various novel superstructural phases has been analyzed. Auger electron spectroscopy studies revealed that the adsorption of Ga at room temperature (RT) follows Frank–van der Merwe (FM) growth mode while for higher substrate temperature, Ga adsorption remains within the submonolayer range. Thermal desorption and low energy electron diffraction studies investigated the formation of thermally stable Ga-islands and the various Ga induced superstructural phase on Si (553). During room temperature adsorption, (1 1 1)7 × 7 facet of Si (553) reconstructed into (1 1 1)6 × 6 facet while during desorption process, stable (1 1 1)6 × 6 and (1 1 1)√3 × √3-R30° surface reconstructions has been observed.

  11. Effect of effluent organic matter on the adsorption of perfluorinated compounds onto activated carbon.

    Yu, Jing; Lv, Lu; Lan, Pei; Zhang, Shujuan; Pan, Bingcai; Zhang, Weiming

    2012-07-30

    Effect of effluent organic matter (EfOM) on the adsorption of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) onto powdered activated carbon (PAC) was quantitatively investigated at environmentally relevant concentration levels. The adsorption of both perfluorinated compounds (PFCs) onto PAC followed pseudo-second order kinetics and fitted the Freundlich model well under the given conditions. Intraparticle diffusion was found to be the rate-controlling step in the PFC adsorption process onto PAC in the absence and presence of EfOM. The presence of EfOM, either in PFC-EfOM simultaneous adsorption onto fresh PAC or in PFC adsorption onto EfOM-preloaded PAC, significantly reduced the adsorption capacities and sorption rates of PFCs. The pH of zero point of charge was found to be 7.5 for fresh PAC and 4.2 for EfOM-preloaded PAC, suggesting that the adsorbed EfOM imparted a negative charge on PAC surface. The effect of molecular weight distribution of EfOM on the adsorption of PFCs was investigated with two EfOM fractions obtained by ultrafiltration. The low-molecular-weight compounds (30kDa) had much less effect on PFC adsorption capacity. PMID:22609392

  12. Optimal working pairs for solar adsorption cooling applications

    This article suggests a detailed comparison of 7 working pairs intended for use in solar adsorption cooling systems. The performance analysis was based on two indicators: adsorption capacity and solar coefficient of performance. Based on a reformed form of the Dubinin–Astakhov equation, a 3D graph was constructed to show the adsorbate concentration in the appropriate adsorbent as a first step to determine the adsorption capacity. A MATLAB program was developed to solve the system equation to predict the solar coefficient of performance for a typical summer day in a Moroccan city Fez. It was found that maximal adsorption capacity is obtained by activated carbon fibre/methanol (0.3406 kg kg−1) followed by activated carbon/methanol (0.2565 kg kg−1) and activated carbon/ethanol (0.2008 kg kg−1). At a condenser temperature of 25 °C, with an adsorbent mass of 20 kg, and an integrated collector-reactor configuration, the couple silica gel/water for air conditioning purpose can reach an SCOP of 0.3843. Activated carbon fibre/methanol is the following more efficient couple and can be used in the different cooling applications with an SCOP ranging from 0.1726 to 0.3287. Furthermore, adequate indicators are evaluated addressing the economic, environmental and safe aspects associated with each working pair. - Highlights: • 7 working pairs intended for use in solar adsorption cooling systems are compared. • A MATLAB program is used to predict the solar coefficient of performance. • Maximal adsorption capacity is obtained by activated carbon fibre/methanol

  13. Partial oxidation of Step-Bound Water Leads to Anomalous pH Effects on Metal Electrode Step-Edges

    Schwarz, Kathleen; Yan, Yushan; Sundararaman, Ravishankar

    2016-01-01

    The design of better heterogeneous catalysts for applications such as fuel cells and electrolyzers requires a mechanistic understanding of electrocatalytic reactions and the dependence of their activity on operating conditions such as pH. A satisfactory explanation for the unexpected pH dependence of electrochemical properties of platinum surfaces has so far remained elusive, with previous explanations resorting to complex co-adsorption of multiple species and resulting in limited predictive power. This knowledge gap suggests that the fundamental properties of these catalysts are not yet understood, limiting systematic improvement. Here, we analyze the change in charge and free energies upon adsorption using density-functional theory (DFT) to establish that water adsorbs on platinum step edges across a wide voltage range, including the double-layer region, with a loss of approximately 0.2 electrons upon adsorption. We show how the change in net surface charge due to this water explains the anomalous pH variat...

  14. Implementasi Sistem Step By Step Switching Menggunakan Komponen Terintegrasi

    Suherman

    2009-01-01

    Sentral yang menggunakan sistem step by step switching telah lama ditinggalkan. Teknologi telah beralih ke sistem switching digital common control, bahkan berbasis packet switching khususnya penggunaan IP based Network. Namun demikian, teknologi switching step by step yang dahulu berbasis sistem mekanis masih dapat diperbaharui dengan memanfaatkan komponen terintegrasi (integrates cicuit, IC). Sistem switching step by step dengan komponen terintegrasi ini dapat dimanfaatkan untuk membentuk...

  15. A biological oil adsorption filter

    Pasila, A. [University of Helsinki (Finland). Dept. of Agricultural Engineering and Household Technology

    2005-12-01

    A new oil adsorption method called adsorption filtration (AF) has been developed. It is a technology where by oil residues can be cleaned from water by running it through a simple filter made from freeze treated, dried, milled and then fragmented plant material. By choosing suitable plants and fragmentation sizes it is possible to produce filters, which pass water but adsorb oil. The aim of this study was to investigate the possibilities of manufacturing oil adsorbing filter materials from reed canary grass (Phalaris arundinacea), flax (Linum usitatissimum L.) or hemp fibre (Cannabis sativa L.). The oil (80 ml) was mixed with de-ionised water (200 ml) and this mixture was filtered through 10 or 20 g adsorption filters. Fine spring harvested hemp fibre (diameter less than 1 mm) and reed canary grass fragments adsorb 2-4 g of oil per gram of adsorption material compared to 1-3 g of water. Adsorption filtration is thus a novel way of gathering spilled oil in shallow coastal waters before the oil reaches the shore. (author)

  16. Adsorptive desulfurization by activated alumina.

    Srivastav, Ankur; Srivastava, Vimal Chandra

    2009-10-30

    This study reports usage of commercial grade activated alumina (aluminum oxide) as adsorbent for the removal of sulfur from model oil (dibenthiophene (DBT) dissolved in n-hexane). Bulk density of alumina was found to be 1177.77 kg/m(3). The BET surface area of alumina was found to decrease from 143.6 to 66.4 m(2)/g after the loading of DBT at optimum conditions. The carbon-oxygen functional groups present on the surface of alumina were found to be effective in the adsorption of DBT onto alumina. Optimum adsorbent dose was found to be 20 g/l. The adsorption of DBT on alumina was found to be gradual process, and quasi-equilibrium reached in 24 h. Langmuir isotherm best represented the equilibrium adsorption data. The heat of adsorption and change in entropy for DBT adsorption onto alumina was found to be 19.5 kJ/mol and 139.2 kJ/mol K, respectively. PMID:19523762

  17. A biological oil adsorption filter

    A new oil adsorption method called adsorption filtration (AF) has been developed. It is a technology where by oil residues can be cleaned from water by running it through a simple filter made from freeze treated, dried, milled and then fragmented plant material. By choosing suitable plants and fragmentation sizes it is possible to produce filters, which pass water but adsorb oil. The aim of this study was to investigate the possibilities of manufacturing oil adsorbing filter materials from reed canary grass (Phalaris arundinacea), flax (Linum usitatissimum L.) or hemp fibre (Cannabis sativa L.). The oil (80 ml) was mixed with de-ionised water (200 ml) and this mixture was filtered through 10 or 20 g adsorption filters. Fine spring harvested hemp fibre (diameter less than 1 mm) and reed canary grass fragments adsorb 2-4 g of oil per gram of adsorption material compared to 1-3 g of water. Adsorption filtration is thus a novel way of gathering spilled oil in shallow coastal waters before the oil reaches the shore. (author)

  18. Thermodynamic Profile of Some Heavy Metal Ions Adsorption Onto Biomaterial Surfaces

    Medhat A. Shaker

    2007-01-01

    Full Text Available The adsorption of Co2+, Zn2+, Pb2+ and Hg2+ onto dried non-living biomass (NB of different Pseudomonas strains has been investigated in detail. Maximum adsorption of these cations is achieved at optimum pH values from 3.5 to 4.5 to avoid hydrolysis, polymerization and precipitation of metal cations in the treatment solutions. The experimental data obtained at different temperatures were fitted to the Langmuir model at different temperatures from 283 to 323 K. Metal ions adsorption occurs in multi detectable steps (i=A, B, C. Binding of Pb(II to NB occurs in one detectable step labeled A, where two detectable binding steps were observed for the other cations; A and B for Zn(II, A and C for Co(II, B and C for Hg(II, respectively. Site capacities, υi are found to be temperature-independent in the whole investigated temperature range. The thermodynamic parameters (∆Hi, ∆Si and ∆Gi for the adsorption processes were calculated for each binding step i and the results suggest that the nature of adsorption is endothermic and the process is spontaneous and favorable. Thermodynamic data pairs (∆Hi , ∆Si for metal binding are linearly correlated for all sites in the investigated biosorption systems.

  19. Adsorption of uranium(VI) from sulphate solutions using Amberlite IRA-402 resin: Equilibrium, kinetics and thermodynamics study

    Highlights: • Adsorption of uranium from sulphate solutions by an anion exchange resin. • The effects of pH, contact time and adsorbent dosage were investigated. • The adsorption equilibrium is well described by the Freundlich isotherm model. • The adsorption kinetics can be predicted by the pseudo second-order model. • The adsorption is a physical, spontaneous and endothermic process. - Abstract: In the present study, adsorption of uranium from sulphate solutions was evaluated using Amberlite IRA-402 resin. The variation of adsorption process was investigated in batch sorption mode. The parameters studied were pH, contact time and adsorbent dosage. Langmuir and Freundlich isotherm models were used in order to present a mathematical description of the equilibrium data at three different temperatures (25 °C, 35 °C and 45 °C). The final results confirmed that the equilibrium data tend to follow Freundlich isotherm model. The maximum adsorption capacity of Amberlite IRA-402 for uranium(VI) was evaluated to be 213 mg/g for the Langmuir model at 25 °C. The adsorption of uranium on the mentioned anion exchange resin was found to follow the pseudo-second order kinetic model, indicating that chemical adsorption was the rate limiting-step. The values of thermodynamic parameters proved that adsorption process of uranium onto Amberlite IRA-402 resin could be considered endothermic (ΔH > 0) and spontaneous (ΔG < 0)

  20. Separation of low concentration of cesium ion from wastewater by electrochemically switched ion exchange method: Experimental adsorption kinetics analysis

    Highlights: ► A continuous cesium separation and regeneration process based on ESIX could be achieved by a diaphragm-isolated reactor. ► The adsorption/desorption rate of Cs+ could be increased by applied potential. ► H3O+ played a dual role of electrolyte and competitor. ► A pseudo-first-order kinetics model could be used to describe the adsorption rate of cesium in the ESIX process. ► The ESIX of cesium consisted of ESIX step and ion diffusion step. - Abstract: A series of experiments were performed to evaluate the continuous separation of cesium based on an electrochemically switched ion exchange (ESIX) process using a diaphragm-isolated reactor with two identical nickel hexacyanoferrate/porous three-dimensional carbon felt (NiHCF/PTCF) electrodes as working electrodes. The effects of applied potential, initial concentrations and pH values of the simulation solutions on the adsorption of cesium ion were investigated. The adsorption rate of cesium ion in the ESIX process was fitted by a pseudo-first-order reaction model. The experiments revealed that the introduction of applied potential on the electrodes greatly enhanced the adsorption/desorption rate of Cs+ and increased the separation efficiency. H3O+ was found to play a dual role of electrolyte and competitor, and the adsorption rate constant showed a curve diversification with an increase in pH value. Also, it was found that the electrochemically switched adsorption process of Cs+ by NiHCF/PTCF electrodes proceeded in two main steps, i.e., an ESIX step with a fast adsorption rate and an ion diffusion step with a slow diffusion rate. Meanwhile, the NiHCF/PTCF film electrode showed adsorption selectivity for Cs+ in preference to Na+.

  1. Single-step synthesis of magnetic chitosan composites and application for chromate (Cr(VI)) removal

    杨卫春; 唐琼芝; 董舒宇; 柴立元; 王海鹰

    2016-01-01

    Magnetic chitosan composites (Fe3O4@chitosan) were synthesized in one single-step, characterized and applied in Cr(VI) removal from water. With the increase of loading proportion of chitosan, Cr(VI) adsorption capacity of Fe3O4@chitosan composites increased from 10.771 to 21.040 mg/g. The optimum adsorption capacities of Cr(VI) on Fe3O4@chitosan-3 were found in a pH range of 3.0−5.0. Kinetic study results show that the adsorption process follows pseudo-second-order model, indicating that the rate-limiting step in the adsorption of Cr(VI) involves chemisorptions. Moreover, FT-IR spectra analysis confirms that the amine and hydroxyl groups of chitosan are predominantly responsible for binding. Results from this work demonstrate that the prepared Fe3O4@chitosan composites possess great potential in Cr(VI) removal from contaminated water.

  2. Adsorption mechanism of copper and cadmium onto defatted waste biomass.

    Ogata, Fumihiko; Tominaga, Hisato; Yabutani, Hitoshi; Kawasaki, Naohito

    2011-01-01

    In this study, the amount of copper or cadmium adsorbed using waste biomass (i.e., coffee grounds (CG) and rice bran (RB)) was investigated. The amount of crude protein in defatted CG (D-CG) or RB (D-RB) was greater than that in CG or RB, respectively. The amount of copper or cadmium adsorbed using CG was greater than that using RB. Additionally, the amount of copper or cadmium adsorbed was not affected by the presence of fat in CG. Adsorption data was fitted to the Freundlich equation, and the correlation coefficients were in the range of 0.794-0.991. The main adsorption mechanism was thought to be monolayer adsorption onto the surface of the waste biomass. The adsorption rate data was fitted to the pseudo-second-order model, and the correlation coefficient average was in the range of 0.891-0.945. This result showed that the rate-limiting step may be chemisorption. Moreover, the amount of copper or cadmium desorbed from CG or RB using 0.01 mol/L or 1.00 mol/L HNO(3) was investigated. Desorption with 0.01 mol/L HNO(3) resulted in the recovery of 86-97% of the copper and cadmium, indicating that copper or cadmium that was adsorbed using waste biomass was recoverable. PMID:21701100

  3. Monomer Adsorption-Desorption Processes

    KE Jian-Hong; LIN Zhen-Quan; CHEN Xiao-Shuang

    2009-01-01

    We propose an adsorption-desorption model for a deposit growth system, in which the adsorption and desorption of particles coexist. By means of the generalized rate equation we investigate the cluster (island) size distribution in the dynamic equilibrium state. The results show that the evolution behaviour of the system depends crucially on the details of the rate kernels. The cluster size distribution can take the ecale-frse power-law form in some cases, while it grows exponentially with size in other cases.

  4. Potential Theory of Multicomponent Adsorption

    Shapiro, Alexander; Stenby, Erling Halfdan

    1998-01-01

    We developed a theory of multicomponent adsorption on the basis of the potential concept originally suggested by Polanyi. The mixture is considered as a heterogeneous substance segregated in the external field emitted by the adsorbent. The same standard equation of state, with no additional fitting...... potential theory and the spreading pressure concept is established, and problems of the theory consistency are studied. Numerical algorithms are suggested for evaluation of the segregated state of the mixture in the potential field of adsorption forces. Comparison with experimental data shows good agreement...... and high degree of predictability of the theory developed....

  5. Theoretical insight of adsorption cooling

    Chakraborty, Anutosh

    2011-06-03

    This letter proposes and presents a thermodynamic formulation to calculate the energetic performances of an adsorption cooler as a function of pore widths and volumes of solid adsorbents. The simulated results in terms of the coefficient of performance are validated with experimental data. It is found from the present analysis that the performance of an adsorption cooling device is influenced mainly by the physical characteristics of solid adsorbents, and the characteristics energy between the adsorbent-adsorbate systems. The present study confirms that there exists a special type of silicagel having optimal physical characteristics that allows us to obtain the best performance.

  6. Thermodynamical and structural insights of orange II adsorption by MgRAlNO3 layered double hydroxides

    [Mg1-x Alx(OH)2][(NO3)x, nH2O] Layered Double Hydroxide (LDH) sorbents with variable Mg/Al molar (R=(1-x)/x) ratios were investigated for adsorption of azo dye, orange II (OII) at various pH and temperature conditions. Mg2AlNO3 displays the highest adsorption capacity with 3.611 mmol of OII per gram of Mg2AlNO3 at 40 oC. Adsorption isotherms have been fitted using the Langmuir model and free energy of adsorption (ΔGo), enthalpy (ΔHo) and entropy (ΔSo) were calculated. The experimental values for ΔGo in temperature range between 10 and 40 oC were found to be negative indicating that a spontaneous process occurred. Positive calculated enthalpy values, characteristic of an endothermic process were found. Characterization of solids (PXRD, FTIR, UV-vis, TGA/DTA, adsorption isotherm BET analysis, SEM and Zetametry) before and after adsorption showed that adsorption proceeds in two steps. First, adsorption occurs at the LDH surface, followed by intercalation via anion exchange. -- Graphical Abstract: Structural and thermodynamical insight of adsorption/Intercalation of OII in MgRAl LDH Display Omitted Highlights: → The nitrate containing hydrotalcite-like compounds (MgRAlNO3 LDH) were prepared by the coprecipitation method. → Adsorption of anionic orange dye(OII) is studied on LDHs at different temperatures. → The adsorption process is well described by the Langmuir isotherm model. → Mg2AlNO3 displays the highest adsorption capacity with 3.611 mmol of OII per gram of Mg2AlNO3 at 40 oC. → Adsorption process does not occur on the surface of the LDH only but an intercalation process is also occurring concomitantly according to the thermodynamical values.

  7. Adsorption of Organics from Domestic Water Supplies.

    McGuire, Michael J.; Suffet, Irwin H.

    1978-01-01

    This article discusses the current state of the art of organics removal by adsorption. Various theoretical explanations of the adsorption process are given, along with practical results from laboratory, pilot-scale, and full-scale applications. (CS)

  8. Adsorption of Levofloxacin to Goethite

    Qin, Xiaopeng; Liu, Fei; Zhao, Long; Hou, Hong; Wang, Guangcai; Li, Fasheng; Weng, Liping

    2016-01-01

    Batch experiments were conducted to investigate the adsorption of a widely used fluoroquinolone antibiotic levofloxacin (LEV) to goethite and effects of nitrate, sulfate, small organic acids, and humic acid (HA). The concentrations of LEV and small organic acids in single systems or mixtures were

  9. Scaling Laws of Polyelectrolyte Adsorption

    Borukhov, I.; Andelman, D.; Orland, H.

    1997-01-01

    Adsorption of charged polymers (polyelectrolytes) from a semi-dilute solution to a charged surface is investigated theoretically. We obtain simple scaling laws for (i) the amount of polymer adsorbed to the surface, Gamma, and (ii) the width of the adsorbed layer D, as function of the fractional charge per monomer p and the salt concentration c_b. For strongly charged polyelectrolytes (p

  10. NO Adsorption on Pd(111)

    Garda, Graciela R.; Ferullo, Ricardo M.; Castellani, Norberto J.

    The reactive behavior of NO on Pd(111) has been studied using a semiempirical theoretical method. The adsorption sites and the related electronic structure have been considered. In particular, the dissociation process has been studied and compared with CO. Different dissociation mechanisms have been proposed and the formation of NCO species has been considered. The results follow the trends reported in the experimental literature.

  11. A Major Step Forward

    2007-01-01

    Optimism arises from the new timetable of denuclearization of the Korean Peninsula Chinese officials like to use mountain climbing to describe the six-party talks aimed at resolving the North Korean nuclear puzzle.In this sense,any step toward the peak-"the verifiable denuclearization of the Korean Peninsula in a peaceful manner"-

  12. Learning SQL in Steps

    Philip Garner

    2015-08-01

    Full Text Available Learning SQL is a common problem for many Computer Science (CS students, the steps involved are quite different to those mastered when learning procedural or object-oriented programming languages. The introduction of commercial products that include shortcuts into the learning environment can initially appear to benefit the student, however, transferring these skills to a textual environment can be difficult for many students. Computer Science students are required to build textual SQL queries because the demands of complex queries can quickly out grow the capabilities of graphical query builders available in many software packages. SQL in Steps (SiS is a graphical user interface centred around the textual translation of a query; this combination of a GUI and a clear representation of its textual meaning has the potential to improve the way in which users gain an understanding of SQL. SiS allows for an incremental and evolutionary development of queries by enabling students to build queries step by step until their goal is reached. A planned evaluation of SiS hopes to quantify the extent to which the introduction of such a user interface into the learning environment can improve the students' understanding of the language.

  13. Partial oxidation of step-bound water leads to anomalous pH effects on metal electrode step-edges.

    Schwarz, Kathleen; Xu, Bingjun; Yan, Yushan; Sundararaman, Ravishankar

    2016-06-28

    The design of better heterogeneous catalysts for applications such as fuel cells and electrolyzers requires a mechanistic understanding of electrocatalytic reactions and the dependence of their activity on operating conditions such as pH. A satisfactory explanation for the unexpected pH dependence of electrochemical properties of platinum surfaces has so far remained elusive, with previous explanations resorting to complex co-adsorption of multiple species and resulting in limited predictive power. This knowledge gap suggests that the fundamental properties of these catalysts are not yet understood, limiting systematic improvement. Here, we analyze the change in charge and free energies upon adsorption using density-functional theory (DFT) to establish that water adsorbs on platinum step edges across a wide voltage range, including the double-layer region, with a loss of approximately 0.2 electrons upon adsorption. We show how this as-yet unreported change in net surface charge due to this water explains the anomalous pH variations of the hydrogen underpotential deposition (Hupd) and the potentials of zero total charge (PZTC) observed in published experimental data. This partial oxidation of water is not limited to platinum metal step edges, and we report the charge of the water on metal step edges of commonly used catalytic metals, including copper, silver, iridium, and palladium, illustrating that this partial oxidation of water broadly influences the reactivity of metal electrodes. PMID:27250359

  14. Effect of aniline on cadmium adsorption by sulfanilic acid-grafted magnetic graphene oxide sheets.

    Hu, Xin-jiang; Liu, Yun-guo; Zeng, Guang-ming; Wang, Hui; Hu, Xi; Chen, An-wei; Wang, Ya-qin; Guo, Yi-Mming; Li, Ting-ting; Zhou, Lu; Liu, Shao-heng; Zeng, Xiao-xia

    2014-07-15

    Cd(II) has posed severe health risks worldwide. To remove this contaminant from aqueous solution, the sulfanilic acid-grafted magnetic graphene oxide sheets (MGOs/SA) were prepared and characterized. The mutual effects of Cd(II) and aniline adsorption on MGOs/SA were studied. The effects of operating parameters such as pH, ionic strength, contact time and temperature on the Cd(II) enrichment, as well as the adsorption kinetics and isotherm were also investigated. The results demonstrated that MGOs/SA could effectively remove Cd(II) and aniline from the aqueous solution and the two adsorption processes were strongly dependent on solution pH. The Cd(II) adsorption was reduced by the presence of aniline at pH5.4. The presence of Cd(II) diminished the adsorption capacity for aniline at pHadsorption at pH>7.8. The decontamination of Cd(II) by MGOs/SA was influenced by ionic strength. Besides, the adsorption process could be well described by pseudo-second-order kinetic model. The intraparticle diffusion study revealed that the intraparticle diffusion was not the only rate-limiting step for the adsorption process. Moreover, the experimental data of isotherm followed the Freundlich isotherm model. PMID:24863786

  15. Adsorption of Hg2+ from aqueous solution onto polyacrylamide/attapulgite

    Polyacrylamide/attapulgite (PAM/ATP) was prepared by the solution polymerization of acrylamide (AM) onto γ-methacryloxypropyl trimethoxy silane (KH-570)-modified attapulgite (ATP). PAM/ATP was characterized using Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The effects of contact time, adsorbent dosage, and pH of the initial solution on the adsorption capacities for Hg2+ were investigated. The adsorption process was rapid; 88% of adsorption occurred within 5 min and equilibrium was achieved at around 40 min. The equilibrium data fitted the Langmuir sorption isotherms well, and the maximum adsorption capacity of Hg2+ onto PAM/ATP was found to be 192.5 mg g-1. The adsorption kinetics of PAM/ATP fitted a pseudo-second-order kinetic model. Our results suggest that chemisorption processes could be the rate-limiting steps in the process of Hg2+ adsorption. Hg2+ adsorbed onto PAM/ATP could be effectively desorbed in hot acetic acid solution, and the adsorption capacity of the regenerated adsorbents could still be maintained at 95% by the sixth cycle.

  16. Site-Specific Scaling Relations for Hydrocarbon Adsorption on Hexagonal Transition Metal Surfaces

    Montemore, Matthew M.; Medlin, James W.

    2013-10-03

    Screening a large number of surfaces for their catalytic performance remains a challenge, leading to the need for simple models to predict adsorption properties. To facilitate rapid prediction of hydrocarbon adsorption energies, scaling relations that allow for calculation of the adsorption energy of any intermediate attached to any symmetric site on any hexagonal metal surface through a carbon atom were developed. For input, these relations require only simple electronic properties of the surface and of the gas-phase reactant molecules. Determining adsorption energies consists of up to four steps: (i) calculating the adsorption energy of methyl in the top site using density functional theory or by simple relations based on the electronic structure of the surface; (ii) using modified versions of classical scaling relations to scale between methyl in the top site and C₁ species with more metal-surface bonds (i.e., C, CH, CH₂) in sites that complete adsorbate tetravalency; (iii) using gas-phase bond energies to predict adsorption energies of longer hydrocarbons (i.e., CR, CR₂, CR₃); and (iv) expressing energetic changes upon translation of hydrocarbons to various sites in terms of the number of agostic interactions and the change in the number of carbon-metal bonds. Combining all of these relations allows accurate scaling over a wide range of adsorbates and surfaces, resulting in efficient screening of catalytic surfaces and a clear elucidation of adsorption trends. The relations are used to explain trends in methane reforming, hydrocarbon chain growth, and propane dehydrogenation.

  17. Adsorption of Hg{sup 2+} from aqueous solution onto polyacrylamide/attapulgite

    Zhao Yijiang, E-mail: cyjzhao@yahoo.com [Chemistry Department of Huaiyin Teachers College, Key Laboratory for Chemistry of Low-Dimensional Materials of Jiangsu Province, No. 111 Changjiang West Road, Huaian 223300, Jiangsu Province (China); Chen Yan [Chemistry Department of Huaiyin Teachers College, Key Laboratory for Chemistry of Low-Dimensional Materials of Jiangsu Province, No. 111 Changjiang West Road, Huaian 223300, Jiangsu Province (China); State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, No. 5 Xinmofan Road, Nanjing 210009, Jiangsu Province (China); Li Meisheng; Zhou Shouyong; Xue Ailian [Chemistry Department of Huaiyin Teachers College, Key Laboratory for Chemistry of Low-Dimensional Materials of Jiangsu Province, No. 111 Changjiang West Road, Huaian 223300, Jiangsu Province (China); Xing Weihong [State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, No. 5 Xinmofan Road, Nanjing 210009, Jiangsu Province (China)

    2009-11-15

    Polyacrylamide/attapulgite (PAM/ATP) was prepared by the solution polymerization of acrylamide (AM) onto {gamma}-methacryloxypropyl trimethoxy silane (KH-570)-modified attapulgite (ATP). PAM/ATP was characterized using Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The effects of contact time, adsorbent dosage, and pH of the initial solution on the adsorption capacities for Hg{sup 2+} were investigated. The adsorption process was rapid; 88% of adsorption occurred within 5 min and equilibrium was achieved at around 40 min. The equilibrium data fitted the Langmuir sorption isotherms well, and the maximum adsorption capacity of Hg{sup 2+} onto PAM/ATP was found to be 192.5 mg g{sup -1}. The adsorption kinetics of PAM/ATP fitted a pseudo-second-order kinetic model. Our results suggest that chemisorption processes could be the rate-limiting steps in the process of Hg{sup 2+} adsorption. Hg{sup 2+} adsorbed onto PAM/ATP could be effectively desorbed in hot acetic acid solution, and the adsorption capacity of the regenerated adsorbents could still be maintained at 95% by the sixth cycle.

  18. Removal of radionuclides from partitioning waste solutions by adsorption and catalytic oxidation methods

    Yamagishi, Isao; Yamaguchi, Isoo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Kubota, Masumitsu [Research Organization for Information Science and Technology (RIST), Tokai, Ibaraki (Japan)

    2000-09-01

    Adsorption of radionuclides with inorganic ion exchangers and catalytic oxidation of a complexant were studied for the decontamination of waste solutions generated in past partitioning tests with high-level liquid waste. Granulated ferrocyanide and titanic acid were used for adsorption of Cs and Sr, respectively, from an alkaline solution resulting from direct neutralization of an acidic waste solution. Both Na and Ba inhibited adsorption of Sr but Na did not that of Cs. These exchangers adsorbed Cs and Sr at low concentration with distribution coefficients of more than 10{sup 4}ml/g from 2M Na solution of pH11. Overall decontamination factors (DFs) of Cs and total {beta} nuclides exceeded 10{sup 5} and 10{sup 3}, respectively, at the neutralization-adsorption step of actual waste solutions free from a complexant. The DF of total {alpha} nuclides was less than 10{sup 3} for a waste solution containing diethylenetriaminepentaacetic acid (DTPA). DTPA was rapidly oxidized by nitric acid in the presence of a platinum catalyst, and radionuclides were removed as precipitates by neutralization of the resultant solution. The DF of {alpha} nuclides increased to 8x10{sup 4} by addition of the oxidation step. The DFs of Sb and Co were quite low through the adsorption step. A synthesized Ti-base exchanger (PTC) could remove Sb with the DF of more than 4x10{sup 3}. (author)

  19. Pressure swing adsorption modeling of acetone and toluene on activated carbon

    唐琳; 李立清; 邢俊东; 刘峥; 姚小龙

    2013-01-01

    A five steps pressure swing adsorption process was designed for acetone and toluene mixtures separation and recovery. Dynamic distributions of gas phase content and temperature were investigated. Based on the theory of Soret and Dufour, a non-isothermal mathematical model was developed to simulate the PSA process. Effects of heat and mass transfer coefficients were studied. The coupled Soret and Dufour effects were also evaluated. It is found that the heat transfer coefficient has little effect on mass transfer in adsorption stage. However, it has some impacts in desorption stage. The maximum value of C/C0 increases by about 25% as heat transfer coefficient decreases. The temperature variation is less than 0.05 K with the change of mass transfer coefficient, so that the effect of mass transfer coefficient on heat transfer can be ignored. It is also concluded that the Soret and Dufour coupled effects are not obvious in pressure swing adsorption compared with fixed-bed adsorption.

  20. ADSORPTION CHARACTERIZATION OF CO(II IONS ONTO CHEMICALLY TREATED QUERCUS COCCIFERA SHELL: EQUILIBRIUM, KINETIC AND THERMODYNAMIC STUDIES

    M. Hamdi Karaoglu

    2011-04-01

    Full Text Available Quercus coccifera shell (QCS, a relatively abundant and inexpensive material, is currently being investigated as an adsorbent to remove cobalt(II from water. Before the adsorption experiments, QCS was subjected to chemical treatment to provide maximum surface area. Then, the kinetics and adsorption mechanism of Co(II ions on QCS were studied using different parameters such as adsorbent dosage, initial concentration, temperature, contact time, and solution pH. The loaded metals could be desorbed effectively with dilute hydrochloric acid, nitric acid, and 0.1 M EDTA. The Langmuir and Freundlich models were used to describe the uptake of cobalt on QCS. The equilibrium adsorption data were better fitted to Langmuir adsorption isotherm model. The maximum adsorption capacity (qm of QCS for Co(II was 33 mg g-1. Various kinetic models were used to describe the adsorption process. The adsorption followed pseudo second-order kinetic model. The intraparticle diffusion was found to be the rate-limiting step in the adsorption process. The diffusion coefficients were calculated and found to be in the range of 3.11×10−6 to 168.78×10−6 cm2s-1. The negative DH* value indicated exothermic nature of the adsorption.

  1. Equilibrium, kinetic and thermodynamic studies on the adsorption of the toxins of Bacillus thuringiensis subsp. kurstaki by clay minerals

    The persistence of Bacillus thuringiensis (Bt) toxins in soil is further enhanced through association with soil particles. Such persistence may improve the effectiveness of controlling target pests, but impose a hazard to non-target organisms in soil ecosystems. In this study, the equilibrium adsorption of the Bt toxin by four clay minerals (montmorillonite, kaolinite, goethite, and silicon dioxide) was investigated, and the kinetic and thermodynamic parameters were calculated. The results showed that Bt toxin could be adsorbed easily by minerals, and the adsorption was much easier at low temperature than at high temperature at the initial concentration varying from 0 to 1000 mg L-1. The adsorption fitted well to both Langmuir and Freundlich isotherm models, but the Freundlich equation was more suitable. The pseudo-second-order (PSO) was the best application model to describe the adsorption kinetic. The adsorption process appeared to be controlled by chemical process, and the intra-particle diffusion was not the only rate-controlling step. The negative standard free energy (ΔrGmθ) values of the adsorption indicated that the adsorption of the Bt toxin by the minerals was spontaneous, and the changes of the standard enthalpy (ΔrHmθ) showed that the adsorption of the Bt toxin by montmorillonite was endothermic while the adsorption by the other three minerals was exothermic.

  2. Equilibrium, kinetic and thermodynamic studies on the adsorption of the toxins of Bacillus thuringiensis subsp. kurstaki by clay minerals

    Fu Qingling; Deng Yali; Li Huishu; Liu Jie [Key Laboratory of Subtropical Agricultural Resource and Environment, Ministry of Agriculture, Huazhong Agricultural University, Wuhan, 430070 (China); Hu Hongqing, E-mail: hqhu@mail.hzau.edu.cn [Key Laboratory of Subtropical Agricultural Resource and Environment, Ministry of Agriculture, Huazhong Agricultural University, Wuhan, 430070 (China); Chen Shouwen [Key Laboratory of Subtropical Agricultural Resource and Environment, Ministry of Agriculture, Huazhong Agricultural University, Wuhan, 430070 (China); Sa Tongmin [Department of Agricultural Chemistry, College of Agriculture, Chungbuk National University, Cheongju, 361-763 (Korea, Republic of)

    2009-02-01

    The persistence of Bacillus thuringiensis (Bt) toxins in soil is further enhanced through association with soil particles. Such persistence may improve the effectiveness of controlling target pests, but impose a hazard to non-target organisms in soil ecosystems. In this study, the equilibrium adsorption of the Bt toxin by four clay minerals (montmorillonite, kaolinite, goethite, and silicon dioxide) was investigated, and the kinetic and thermodynamic parameters were calculated. The results showed that Bt toxin could be adsorbed easily by minerals, and the adsorption was much easier at low temperature than at high temperature at the initial concentration varying from 0 to 1000 mg L{sup -1}. The adsorption fitted well to both Langmuir and Freundlich isotherm models, but the Freundlich equation was more suitable. The pseudo-second-order (PSO) was the best application model to describe the adsorption kinetic. The adsorption process appeared to be controlled by chemical process, and the intra-particle diffusion was not the only rate-controlling step. The negative standard free energy ({Delta}{sub r}G{sub m}{sup {theta}}) values of the adsorption indicated that the adsorption of the Bt toxin by the minerals was spontaneous, and the changes of the standard enthalpy ({Delta}{sub r}H{sub m}{sup {theta}}) showed that the adsorption of the Bt toxin by montmorillonite was endothermic while the adsorption by the other three minerals was exothermic.

  3. Equilibrium, kinetic and thermodynamic studies on the adsorption of the toxins of Bacillus thuringiensis subsp. kurstaki by clay minerals

    Fu, Qingling; Deng, Yali; Li, Huishu; Liu, Jie; Hu, Hongqing; Chen, Shouwen; Sa, Tongmin

    2009-02-01

    The persistence of Bacillus thuringiensis ( Bt) toxins in soil is further enhanced through association with soil particles. Such persistence may improve the effectiveness of controlling target pests, but impose a hazard to non-target organisms in soil ecosystems. In this study, the equilibrium adsorption of the Bt toxin by four clay minerals (montmorillonite, kaolinite, goethite, and silicon dioxide) was investigated, and the kinetic and thermodynamic parameters were calculated. The results showed that Bt toxin could be adsorbed easily by minerals, and the adsorption was much easier at low temperature than at high temperature at the initial concentration varying from 0 to 1000 mg L -1. The adsorption fitted well to both Langmuir and Freundlich isotherm models, but the Freundlich equation was more suitable. The pseudo-second-order (PSO) was the best application model to describe the adsorption kinetic. The adsorption process appeared to be controlled by chemical process, and the intra-particle diffusion was not the only rate-controlling step. The negative standard free energy ( ΔGmθr) values of the adsorption indicated that the adsorption of the Bt toxin by the minerals was spontaneous, and the changes of the standard enthalpy ( ΔHmθr) showed that the adsorption of the Bt toxin by montmorillonite was endothermic while the adsorption by the other three minerals was exothermic.

  4. Hybrid Vapor Compression Adsorption System: Thermal Storage Using Hybrid Vapor Compression Adsorption System

    None

    2012-01-04

    HEATS Project: UTRC is developing a new climate-control system for EVs that uses a hybrid vapor compression adsorption system with thermal energy storage. The targeted, closed system will use energy during the battery-charging step to recharge the thermal storage, and it will use minimal power to provide cooling or heating to the cabin during a drive cycle. The team will use a unique approach of absorbing a refrigerant on a metal salt, which will create a lightweight, high-energy-density refrigerant. This unique working pair can operate indefinitely as a traditional vapor compression heat pump using electrical energy, if desired. The project will deliver a hot-and-cold battery that provides comfort to the passengers using minimal power, substantially extending the driving range of EVs.

  5. Adsorption from solutions of non-electrolytes

    Kipling, J J

    1965-01-01

    Adsorption from Solutions of Non-Electrolytes provides a general discussion of the subject, which has so far been given little or no attention in current textbooks of physical chemistry. A general view of the subject is particularly needed at a time when we wish to see how far it will be possible to use theories of solutions to explain the phenomena of adsorption. The book opens with an introductory chapter on the types of interface, aspects of adsorption from solution, types of adsorption, and classification of systems. This is followed by separate chapters on experimental methods, adsorption

  6. Dye adsorption behavior of Luffa cylindrica fibers.

    Demir, H; Top, A; Balköse, D; Ulkü, S

    2008-05-01

    Using natural Luffa cylindrica fibers as adsorbent removal of methylene blue dye from aqueous solutions at different temperatures and dye concentrations was investigated in this study. Thermodynamics and kinetics of adsorption were also investigated. The adsorption isotherms could be well defined with Langmuir model instead of Freundlich model. The thermodynamic parameters of methylene blue (MB) adsorption indicated that the adsorption is exothermic and spontaneous. The average MB adsorption capacity was found out as 49 mg/g and average BET surface area of fibers was calculated as 123 m(2)/g. PMID:17919814

  7. Dye adsorption behavior of Luffa cylindrica fibers

    Using natural Luffa cylindrica fibers as adsorbent removal of methylene blue dye from aqueous solutions at different temperatures and dye concentrations was investigated in this study. Thermodynamics and kinetics of adsorption were also investigated. The adsorption isotherms could be well defined with Langmuir model instead of Freundlich model. The thermodynamic parameters of methylene blue (MB) adsorption indicated that the adsorption is exothermic and spontaneous. The average MB adsorption capacity was found out as 49 mg/g and average BET surface area of fibers was calculated as 123 m2/g

  8. Dye adsorption behavior of Luffa cylindrica fibers

    Demir, H. [Izmir Institute of Technology, Faculty of Engineering, Department of Chemical Engineering, Guelbahce Campus, 35430 Urla Izmir (Turkey)], E-mail: hasandemir@iyte.edu.tr; Top, A.; Balkoese, D.; Ulkue, S. [Izmir Institute of Technology, Faculty of Engineering, Department of Chemical Engineering, Guelbahce Campus, 35430 Urla Izmir (Turkey)

    2008-05-01

    Using natural Luffa cylindrica fibers as adsorbent removal of methylene blue dye from aqueous solutions at different temperatures and dye concentrations was investigated in this study. Thermodynamics and kinetics of adsorption were also investigated. The adsorption isotherms could be well defined with Langmuir model instead of Freundlich model. The thermodynamic parameters of methylene blue (MB) adsorption indicated that the adsorption is exothermic and spontaneous. The average MB adsorption capacity was found out as 49 mg/g and average BET surface area of fibers was calculated as 123 m{sup 2}/g.

  9. Liquid-liquid extraction and adsorption on solid surfaces applied to used lubricant oils recovery

    J. L. Assunção Filho

    2010-12-01

    Full Text Available In this work, the recovery of base oils from waste lubricants following the steps of solvent extraction, adsorption on solids and solvent removal by evaporation was evaluated. In the step of solvent extraction, the most efficient was 1-butanol, followed by tert-butanol, 2-propanol and ethanol; for the step of adsorption, activated carbon was the most effective solid for PAH removal, confirming the similarity of these compounds with petroleum aromatic fractions. Thus, the optimum solvent-adsorbent pair for the recovery of used lubricant oils through the proposed methodology was 1-butanol/activated carbon. At the end of the process, it was possible to establish a set of steps that permit the recovery of lubricant base oils with lower content of contaminants.

  10. Adsorption of branched and dendritic polymers onto flat surfaces: A Monte Carlo study

    Sommer, J.-U. [Leibniz Institute of Polymer Research Dresden e. V., 01069 Dresden (Germany); Institute for Theoretical Physics, Technische Universität Dresden, 01069 Dresden (Germany); Kłos, J. S. [Leibniz Institute of Polymer Research Dresden e. V., 01069 Dresden (Germany); Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Mironova, O. N. [Leibniz Institute of Polymer Research Dresden e. V., 01069 Dresden (Germany)

    2013-12-28

    Using Monte Carlo simulations based on the bond fluctuation model we study the adsorption of starburst dendrimers with flexible spacers onto a flat surface. The calculations are performed for various generation number G and spacer length S in a wide range of the reduced temperature τ as the measure of the interaction strength between the monomers and the surface. Our simulations indicate a two-step adsorption scenario. Below the critical point of adsorption, τ{sub c}, a weakly adsorbed state of the dendrimer is found. Here, the dendrimer retains its shape but sticks to the surface by adsorbed spacers. By lowering the temperature below a spacer-length dependent value, τ*(S) < τ{sub c}, a step-like transition into a strongly adsorbed state takes place. In the flatly adsorbed state the shape of the dendrimer is well described by a mean field model of a dendrimer in two dimensions. We also performed simulations of star-polymers which display a simple crossover-behavior in full analogy to linear chains. By analyzing the order parameter of the adsorption transition, we determine the critical point of adsorption of the dendrimers which is located close to the critical point of adsorption for star-polymers. While the order parameter for the adsorbed spacers displays a critical crossover scaling, the overall order parameter, which combines both critical and discontinuous transition effects, does not display simple scaling. The step-like transition from the weak into the strong adsorbed regime is confirmed by analyzing the shape-anisotropy of the dendrimers. We present a mean-field model based on the concept of spacer adsorption which predicts a discontinuous transition of dendrimers due to an excluded volume barrier. The latter results from an increased density of the dendrimer in the flatly adsorbed state which has to be overcome before this state is thermodynamically stable.

  11. Adsorption of Phosphate on Variable Charge Soils

    HUGUO-SONG; ZHUZU-XIANG; 等

    1992-01-01

    The study about the adsorption of phosphate on four variable charge soils and some minerals revealed that two stage adsorption appeared in the adsorption isothems of phosphate on 4 soils and there was a maximum adsorption on Al-oxide-typed surfaces between pH 3.5 to pH 5.5 as suspension pH changed from 2 to 9,but the adsorption amount of phosphate decreased continually as pH rose on Fe-oxide typed surfaces.The adsorption amount of phosphate and the maximum phosphate adsorption pH decreased in the order of yellow-red soil> lateritic red soil> red soil> paddy soil,which was coincided with the content order of amorphous Al oxide.The removement of organic matter and Fe oxide made the maximum phosphate adsorption pH rise from 4.0 to 5.0 and 4.5,respectively.The desorption curves with pH of four soils showed that phosphate desorbed least at pH 5.Generally the desorption was contrary to the adsorption with pH changing.There was a good accordance between adsorption or desorption and the concentration of Al in the suspension.The possible mechanisms of phosphate adsorption are discussed.

  12. Phosphate adsorption on lanthanum loaded biochar.

    Wang, Zhanghong; Shen, Dekui; Shen, Fei; Li, Tianyu

    2016-05-01

    To attain a low-cost and high-efficient phosphate adsorbent, lanthanum (La) loaded biochar (La-BC) prepared by a chemical precipitation method was developed. La-BC and its pristine biochar (CK-BC) were comparatively characterized using zeta potential, BET surface area, scanning electron microscopy/energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The adsorption ability and the mechanisms during adsorption process for the La-BC samples were also investigated. La loaded on the surface of biochar can be termed as La-composites (such as LaOOH, LaONO3 and La(OH)3), leading to the decrease of negative charge and surface area of biochar. La-BC exhibited the high adsorption capacity to phosphate compared to CK-BC. Adsorption isotherm and adsorption kinetic studies showed that the Langmuir isotherm and second order model could well describe the adsorption process of La-BC, indicating that the adsorption was dominated by a homogeneous and chemical process. The calculated maximum adsorption capacity was as high as 46.37 mg g(-1) (computed in P). Thermodynamic analysis revealed that the adsorption was spontaneous and endothermic. SEM, XRD, XPS and FT-IR analysis suggested that the multi-adsorption mechanisms including precipitation, ligand exchange and complexation interactions can be evidenced during the phosphate adsorption process by La-composites in La-BC. PMID:26871732

  13. Adsorption of amitraz on the clay

    Jale Gülen

    2013-01-01

    Full Text Available Amitraz (AZ that is used as acaridies was tried to extract with a clay. The experimental data were modelled as using Langmuir and Freundlich isotherms. The adsorption data fit well with Langmuir isotherm that indicated the AZ adsorption is homogeneous and monolayer. The monolayer adsorption capacity was found to be 35.02 mg/g at 20 ºC temperature. Effect of the phases contact time, the initial solution pH and the initial pesticide concentration were investigated from the point of adsorption equilibrium and yield. The adsorption kinetics were investigated by applying pseudo first order, pseudo second order and intra particle diffusion laws. Adsorption of AZ was found to be best fitted by the pseudo second order model. The intra particle diffusion also plays an important role in adsorption phenomenon.

  14. Steps and cycles

    Chadwick, Andy

    2015-01-01

    Andy Chadwick* explains how interaction between continuous trend with natural climate cycles produces the observed stepped pattern of global warming Climate-change ‘sceptics’ have made great mileage out of the current hiatus in observed global warming. Atmospheric temperatures have not really increased since the turn of the 21st Century, a fact frequently cited as incompatible with, or even disproving, global warming. These same commentators draw a discreet veil over the fact that temper...

  15. Tick Removal: A Step-by-Step Guide (For Parents)

    ... Story" 5 Things to Know About Zika & Pregnancy Tick Removal: A Step-by-Step Guide KidsHealth > For Parents > Tick Removal: A Step-by-Step Guide Print A ... isn't a freckle at all. It's a tick. What should you do? First, don't panic. ...

  16. Equation of state and adsorption dynamics of soft microgel particles at an air-water interface

    Deshmukh, O.S.; Maestro, A.; Duits, M.H.G.; Ende, van den D.T.M.; Cohen Stuart, M.A.; Mugele, F.

    2014-01-01

    Understanding the adsorption dynamics of soft microgel particles is a key step in designing such particles for potential applications as stimuli-responsive Pickering stabilizers for foams or emulsions. In this study we experimentally determine an equation of state (EOS) for poly (N-isopropylacrylami

  17. Competitive adsorption-desorption reactions of two hazardous heavy metals in contaminated soils.

    Davari, Masoud; Rahnemaie, Rasoul; Homaee, Mehdi

    2015-09-01

    Investigating the interactions of heavy metals is imperative for sustaining environment and human health. Among those, Cd is toxic for organisms at any concentration. While Ni acts as a micronutrient at very low concentration but is hazardous toxic above certain threshold value. In this study, the chemical adsorption and desorption reactions of Ni and Cd in contaminated soils were investigated in both single and binary ion systems. Both Ni and Cd experimental data demonstrated Langmuir type adsorption. In the competitive systems, an antagonistic effect was observed, implying that both ions compete for same type of adsorption sites. Adverse effect of Cd on Ni adsorption was slightly stronger than that of opposite system, consistent with adsorption isotherms in single ion systems. Variation in ionic strength indicated that Ca, a much weaker adsorbate, could also compete with Cd and Ni for adsorption on soil particles. Desorption data indicated that Cd and Ni are adsorbed very tightly such that after four successive desorption steps, less than 0.5 % of initially adsorbed ions released into the soil solution. This implies that Ca, at concentration in equilibrium with calcite mineral, cannot adequately compete with and replace adsorbed Ni and Cd ions. This adsorption behavior was led to considerable hysteresis between adsorption and desorption in both single and binary ion systems. In the binary ion systems, desorption of Cd and Ni was increased by increase in both equilibrium concentration of adsorbed ion and concentration of competitor ion. The overall results obtained in this research indicate that Cd and Ni are strongly adsorbed in calcareous soil and Ca, the major dissolved ion, insignificantly influences metal ions adsorption. Consequently, the contaminated soils by Ni and Cd can simultaneously be remediated by environmentally oriented technologies such as phytoremediation. PMID:25921756

  18. Hydrogen adsorption in carbon materials

    David, P.; Piquero, T.; Metenier, K.; Pierre, Y. [CEA Centre d' Etudes du Ripault, 37 - Tours (France); Demoment, J.; Lecas-Hardit, A. [CEA Valduc, 21 - Is-sur-Tille (France)

    2003-09-01

    The development of new technologies for energy is a necessity for both economic and environmental aspects. Hydrogen is expected to be, in the future, an important energy vector. However its storage, for mobile applications (fuel cell for automotive for example), represents a major difficulty. Several solutions have been used for demonstration (liquid hydrogen, high pressure vessel, hydride) but do not meet the requirements. Hydrogen adsorption in carbon materials also represents a potential solution which is currently discussed. (O.M.)

  19. Optimum conditions for adsorptive storage.

    Bhatia, Suresh K; Myers, Alan L

    2006-02-14

    The storage of gases in porous adsorbents, such as activated carbon and carbon nanotubes, is examined here thermodynamically from a systems viewpoint, considering the entire adsorption-desorption cycle. The results provide concrete objective criteria to guide the search for the "Holy Grail" adsorbent, for which the adsorptive delivery is maximized. It is shown that, for ambient temperature storage of hydrogen and delivery between 30 and 1.5 bar pressure, for the optimum adsorbent the adsorption enthalpy change is 15.1 kJ/mol. For carbons, for which the average enthalpy change is typically 5.8 kJ/mol, an optimum operating temperature of about 115 K is predicted. For methane, an optimum enthalpy change of 18.8 kJ/mol is found, with the optimum temperature for carbons being 254 K. It is also demonstrated that for maximum delivery of the gas the optimum adsorbent must be homogeneous, and that introduction of heterogeneity, such as by ball milling, irradiation, and other means, can only provide small increases in physisorption-related delivery for hydrogen. For methane, heterogeneity is always detrimental, at any value of average adsorption enthalpy change. These results are confirmed with the help of experimental data from the literature, as well as extensive Monte Carlo simulations conducted here using slit pore models of activated carbons as well as atomistic models of carbon nanotubes. The simulations also demonstrate that carbon nanotubes offer little or no advantage over activated carbons in terms of enhanced delivery, when used as storage media for either hydrogen or methane. PMID:16460092

  20. Investigation of adsorption performance deterioration in silica gel–water adsorption refrigeration

    Highlights: ► Adsorption deterioration of silica gel in refrigeration systems is verified. ► Possible factors to cause such deterioration are analyzed. ► Specific surface area, silanol content and adsorption capacity are tested. ► The pollution is the primary factor to decline the adsorption capacity. ► Deteriorated samples are partly restored after being processed by acid solution. - Abstract: Silica gel acts as a key role in adsorption refrigeration systems. The adsorption deterioration must greatly impact the performance of the silica gel–water adsorption refrigeration system. In order to investigate the adsorption deterioration of silica gel, many different silica gel samples were prepared according to the application surroundings of silica gel in adsorption refrigeration systems after the likely factors to cause such deterioration were analyzed. The specific surface area, silanol content, adsorption capacity and pore size distribution of those samples were tested and the corresponding adsorption isotherms were achieved. In terms of the experimental data comparisons, it could be found that there are many factors to affect the adsorption performance of silica gel, but the pollution was the primary one to decline the adsorption capacity. In addition, the adsorption performance of the deteriorated samples after being processed by acid solution was explored in order to find the possible methods to restore its adsorption performance.

  1. Adsorption and activation of methane and methanol on Pt(100) surface: a density functional study; Adsorption et activation du methane et du methanol sur la surface (100) du platine: une etude par la fonctionnelle de la densite

    Moussounda, P.S

    2006-11-15

    The activation of methane (CH{sub 4}) and methanol (CH{sub 3}OH) on Pt(100) surface has been investigated using density functional theory calculations based on plane-wave basis and pseudo-potential. We optimised CH{sub 4}/Pt(100) system. The calculated adsorption energies over the top, bridge and hollow sites are small, weakly dependent on the molecular orientation. The nature of the CH{sub 4}-Pt interaction was examined through the electronic structure changes. The adsorption of methyl (CH{sub 3}) and hydrogen (H) and the co-adsorption of CH{sub 3}+H were also calculated. From these results, we examined the dissociation of CH{sub 4} to CH{sub 3}+H, and the activation energies found are in good agreement with the experimental and theoretical values. The activation of CH{sub 3}OH/Pt(100) has been studied. All the sites have almost the same adsorption energy. The adsorption of oxygen (O) and the co-adsorption of CH{sub 4} and O were also examined. In addition, the formation of CH{sub 3}OH assuming a one-step mechanism step via the co-adsorption of CH{sub 4}+O has been studied and the barrier height was found to be high. (authors)

  2. Step Motor Control System

    ZhangShuochengt; WangDan; QiaoWeimin; JingLan

    2003-01-01

    All kinds of step motors and servomotors are widely used in CSR control system, such as many vacuum valves control that set on the HIRFL-CSR; all kinds of electric switches and knobs of ECR Ion Source; equipment of CSR Beam Diagnostics and a lot of large equipment like Inside Gun Toroid and Collector Toroid of HIRFL. A typical control system include up to 32 16-I/O Control boards, and each 16-I/O Control board can control 4 motors at the same time (including 8 Limit Switches).

  3. Linux in easy steps

    McGrath, Mike

    2011-01-01

    Linux is becoming more and more popular, but the installation can often be daunting for new users. Linux in Easy Steps to the rescue! Following this book's simple instructions, readers quickly install Linux, learn to explore the desktop, and launch great applications. This fully illustrated primer teaches important know-how, like how to climb the Linux directory tree, navigate with the File Browser, and much more. Its easy-to-understand tutorials guide readers through the OpenOffice business suite and media applications, letting them enjoy the Web, music, video, and graphics. Later chapters sh

  4. New photolithography stepping machine

    Hale, L.; Klingmann, J. [Lawrence Livermore National Lab., CA (United States); Markle, D. [Ultratech Stepper Inc. (United States)

    1995-03-08

    A joint development project to design a new photolithography steeping machine capable of 150 nanometer overlay accuracy was completed by Ultratech Stepper and the Lawrence Livermore National Laboratory. The principal result of the project is a next-generation product that will strengthen the US position in step-and-repeat photolithography. The significant challenges addressed and solved in the project are the subject of this report. Design methods and new devices that have broader application to precision machine design are presented in greater detail while project specific information serves primarily as background and motivation.

  5. Adsorption-dissolution reactions affecting the distribution and stability of CoIIEDTA in ion oxide-coated sand

    The time-variant chemical behavior of CoIIEDTA (and other metal-EDTA complexes) was investigated in suspensions of iron oxide-coated sand to identify equilibrium and kinetic reactions that control the mobility of MeII-EDTA complexes in subsurface environments. Batch experiments were conducted to evaluate the adsorption as a function of pH, concentration, and time and to quantify the rate-controlling step(s) of dissolution of the iron oxide by EDTA complexes. Ionic Co2+ exhibited typical cation-like adsorption, whereas MeIIEDTA adsorption was ligand-like, increasing with decreasing pH. Adsorption isotherms for all reactive species exhibited Langmuir behavior, with site saturation occurring at molar values of tot. The adsorption of MeIIEDTA enhanced the apparent solubility of the iron oxide phase, which destabilized the CoIIEDTA complex, liberating Co2+ and FeIIIEDTA. The dissolution rate was an order of magnitude slower at pH 6.5 than at pH 4.5 and was influenced by the re-adsorption of solubilized FeIIIEDTA. Two multireaction kinetic models were developed that each included Langmuir adsorption for Co2+ and metal-EDTA species but differed in their depiction of the dissolution mechanism (i.e., ligand-versus proton-promoted dissolution). 45 refs., 8 figs., 6 tabs

  6. SPAR-H Step-by-Step Guidance

    W. J. Galyean; A. M. Whaley; D. L. Kelly; R. L. Boring

    2011-05-01

    This guide provides step-by-step guidance on the use of the SPAR-H method for quantifying Human Failure Events (HFEs). This guide is intended to be used with the worksheets provided in: 'The SPAR-H Human Reliability Analysis Method,' NUREG/CR-6883, dated August 2005. Each step in the process of producing a Human Error Probability (HEP) is discussed. These steps are: Step-1, Categorizing the HFE as Diagnosis and/or Action; Step-2, Rate the Performance Shaping Factors; Step-3, Calculate PSF-Modified HEP; Step-4, Accounting for Dependence, and; Step-5, Minimum Value Cutoff. The discussions on dependence are extensive and include an appendix that describes insights obtained from the psychology literature.

  7. SPAR-H Step-by-Step Guidance

    This guide provides step-by-step guidance on the use of the SPAR-H method for quantifying Human Failure Events (HFEs). This guide is intended to be used with the worksheets provided in: 'The SPAR-H Human Reliability Analysis Method,' NUREG/CR-6883, dated August 2005. Each step in the process of producing a Human Error Probability (HEP) is discussed. These steps are: Step-1, Categorizing the HFE as Diagnosis and/or Action; Step-2, Rate the Performance Shaping Factors; Step-3, Calculate PSF-Modified HEP; Step-4, Accounting for Dependence, and; Step-5, Minimum Value Cutoff. The discussions on dependence are extensive and include an appendix that describes insights obtained from the psychology literature.

  8. Adsorptive desulfurization by copper species within confined space.

    Tian, Wen-Hang; Sun, Lin-Bing; Song, Xue-Lin; Liu, Xiao-Qin; Yin, Yu; He, Gu-Se

    2010-11-16

    Copper species were incorporated into SBA-15 by solid-state grinding precursor with as-prepared mesoporous silica (SPA). The obtained materials (CuAS) were well-characterized by XRD, TEM, N(2) adsorption, H(2)-TPR, IR, and TG and compared with the material derived from calcined SBA-15 (CuCS). Surprisingly, CuO up to 6.7 mmol·g(-1) can be highly dispersed on SBA-15 by use of SPA strategy. Such CuO forms a smooth layer coated on the internal walls of SBA-15, which contributes to the spatial order and results in less-blocked mesopores. However, the aggregation of CuO takes place in CuCS material containing 6.7 mmol·g(-1) copper, which generates large CuO particles of 21.4 nm outside the mesopores. We reveal that the high dispersion extent of CuO is ascribed to the abundant silanols, as well as the confined space between template and silica walls provided by as-prepared SBA-15. The SPA strategy allows template removal and precursor conversion in one step, avoids the repeated calcination in conventional modification process, and saves time and energy. We also demonstrate that the CuAS material after autoreduction exhibits much better adsorptive desulfurization capacity than CuCS. Moreover, the adsorption capacity of regenerated adsorbent can be recovered completely. PMID:20882950

  9. Graphene oxide and adsorption of chloroform: A density functional study

    Kuisma, Elena; Hansson, C. Fredrik; Lindberg, Th. Benjamin; Gillberg, Christoffer A.; Idh, Sebastian; Schröder, Elsebeth

    2016-05-01

    Chlorinated hydrocarbon compounds are of environmental concerns, since they are toxic to humans and other mammals, and are widespread, and exposure is hard to avoid. Understanding and improving methods to reduce the amount of the substances are important. We present an atomic-scale calculational study of the adsorption of chlorine-based substance chloroform (CHCl3) on graphene oxide, as a step in estimating the capacity of graphene oxide for filtering out such substances, e.g., from drinking water. The calculations are based on density functional theory, and the recently developed consistent-exchange functional for the van der Waals density-functional method is employed. We obtain values of the chloroform adsorption energy varying from roughly 0.2 to 0.4 eV per molecule. This is comparable to previously found results for chloroform adsorbed directly on clean graphene, using similar calculations. In a wet environment, like filters for drinking water, the graphene will not stay clean and will likely oxidize, and thus adsorption onto graphene oxide, rather than clean graphene, is a more relevant process to study.

  10. Contribution to the study of chemical and physical properties of mineral coals and mineral active coals. New method of determination of adsorption isotherms

    For a better understanding of the influence of factors which influence the coal activation process, this research thesis aims at following, step by step, the evolution of texture and chemical properties of a mineral coal submitted to a series of treatments which allow its progressive transformation into an active coal. The first part reports sample preparation and the study of chemical properties, notably surface functions. The second part addresses physical properties of samples: study of porosity by electronic microscopy, apparatus used to study gas adsorption, helium adsorption by solid surfaces at room temperature, study of the porous texture by gas adsorption

  11. Adsorption of goethite onto quartz and kaolinite

    Goldberg, M.C.; Weiner, Eugene R.; Boymel, P.M.

    1984-01-01

    The adsorption of colloidal goethite onto quartz and kaolinite substrates has been studied as a function of pH and NaCl concentration. Goethite adsorption was measured quantitatively by Fourier-transform infrared spectroscopy. The results indicate that adsorption onto both substrates is due primarily to coulombic forces; however, the pH dependence of adsorption is very different for the two substrates. This is explained by the fact that the surface charge on quartz is entirely pH-dependent, while kaolinite has surface faces which carry a permanent negative charge. Adsorption of goethite on to kaolinite increases markedly with increasing NaCl concentration, while adsorption onto quartz is relatively independent of NaCl concentration. This can be explained by the influence of NaCl concentration upon the development of surface charge on the substrates. A method is described for separating surface-bound goethite from free goethite.

  12. Fibrinogen adsorption on blocked surface of albumin

    Holmberg, Maria; Hou, Xiaolin

    2011-01-01

    We have investigated the adsorption of albumin and fibrinogen onto PET (polyethylene terephthalate) and glass surfaces and how pre-adsorption of albumin onto these surfaces can affect the adsorption of later added fibrinogen. For materials and devices being exposed to blood, adsorption of...... fibrinogen is often a non-wanted event, since fibrinogen is part of the clotting cascade and unspecific adsorption of fibrinogen can have an influence on the activation of platelets. Albumin is often used as blocking agent for avoiding unspecific protein adsorption onto surfaces in devices designed to handle...... biological samples, including protein solutions. It is based on the assumption that proteins adsorbs as a monolayer on surfaces and that proteins do not adsorb on top of each other. By labelling albumin and fibrinogen with two different radioactive iodine isotopes that emit gamma radiation with different...

  13. Adsorption and Desorption of Methiopyrsulfuron in Soils

    WU Chun-Xian; WANG Jin-Jun; ZHANG Su-Zhi; ZHANG Zhong-Ming

    2011-01-01

    Methiopyrsulfuron is a new low-rate sulfonylurea herbicide for weed control in wheat; however, there is a lack of published information on its behavior in soils. In this study, methiopyrsulfuron adsorption and desorption were measured in seven soils sampled from Heilongjiang, Shandong, Jiangxi, Sichuan, Anhui, and Chongqing provinces of China using a batch equilibrium method. The Freundlich equation was used to described its adsorption and desorption. Adsorption isotherms were nonlinear with the values of Kf-ads, the Freundlich empirical constant indicative of the adsorption capacity,ranging from 0.75 to 2.46, suggesting that little of this herbicide was adsorbed by any of the seven soils. Soil pH and organic matter content (OM) were the main factors influencing adsorption; adsorption was negatively correlated with pH and positively correlated with OM. Methiopyrsulfuron desorption was hysteretic on the soils with high OM content and low pH.

  14. Effect of piezoelectric material on hydrogen adsorption

    Li, Xuan [Department of Materials Science and Engineering, Michigan Technological University, 1400 Townsend Drive, Houghton, MI, 49931 (United States); Civil and Environmental Engineering School, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing, 100083 (China); Hwang, Jiann-Yang; Shi, Shangzhao; Sun, Xiang; Zhang, Zheng [Department of Materials Science and Engineering, Michigan Technological University, 1400 Townsend Drive, Houghton, MI, 49931 (United States)

    2010-09-15

    In hydrogen storage applications, the primary issue for physisorption of hydrogen onto solid-state materials is the weak interaction force between hydrogen molecules and the adsorbents. It is found that enhanced adsorption can be obtained under an external electric field, because it appears the electric field increases the hydrogen adsorption energy. Experiments were carried out to determine hydrogen adsorption on activated carbon using the piezoelectric material PMN-PT as the charge supplier under hydrogen pressure. Results indicate that more than 20% hydrogen adsorption enhancement was obtained. Parameters related to hydrogen adsorption enhancement include the amount of the charge and temperature. Higher voltage and lower temperature promote the increase of adsorption capacity but room temperature results are very encouraging. (author)

  15. Gibbs adsorption and the compressibility equation

    A new approach for deriving the equation of state is developed. It is shown that the integral in the compressibility equation is identical to the isotherm for Gibbs adsorption in radial coordinates. The Henry, Langmuir, and Frumkin adsorption isotherms are converted into equations of state. It is shown that using Henry's law gives an expression for the second virial coefficient that is identical to the result from statistical mechanics. Using the Langmuir isotherm leads to a new analytic expression for the hard-sphere equation of state which can be explicit in either pressure or density. The Frumkin isotherm results in a new equation of state for the square-well potential fluid. Conversely, new adsorption isotherms can be derived from equations of state using the compressibility equation. It is shown that the van der Waals equation gives an adsorption isotherm equation that describes both polymolecular adsorption and the unusual adsorption behavior observed for supercritical fluids. copyright 1995 American Institute of Physics

  16. Adsorption of octylamine on titanium dioxide

    Processes of adsorption and desorption of a model active substance (octylamine) on the surface of unmodified titanium dioxide (E 171) have been performed. The effects of concentration of octylamine and time of the process on the character of adsorption have been studied and the efficiency of the adsorption/desorption has been determined. The samples obtained have been studied by X-ray diffraction. The nitrogen adsorption/desorption isotherms, particle size distribution and absorption capacities of water, dibutyl phthalate and paraffin oil have been determined. The efficiency of octylamine adsorption on the surface of the titanium dioxide has been found positively correlated with the concentration of octylamine in the initial solution. The desorption of octylamine has decreased with increasing concentration of this compound adsorbed. For octylamine in low concentrations the physical adsorption has been found to dominate, which is desirable when using TiO2 in the production of pharmaceuticals.

  17. The effects of surface chemistry of mesoporous silica materials and solution pH on kinetics of molsidomine adsorption

    Adsorption kinetics of molsidomine on mesoporous silica material (UMS), the phenyl- (PhMS) and mercaptopropyl-functionalized (MMS) derivatives from solution with different pH and 298 K was studied. The adsorption kinetics was found to follow the pseudo-second-order kinetic model for all studied silica materials and pH. Effects of surface functional groups and pH on adsorption efficiency and kinetic adsorption parameters were investigated. At all studied pH, the highest molsidomine amount is adsorbed on PhMS due to π–π interactions and hydrogen bonding between surface groups of PhMS and molsidomine molecules. An increase of pH results in a decrease of the amounts of adsorbed molsidomine onto the silica materials. Furthermore, the highest adsorption rate kinetically evaluated using a pseudo-second-order model, is observed onto UMS and it strongly depends on pH. The mechanism of the adsorption process was determined from the intraparticle diffusion and Boyd kinetic film–diffusion models. The results showed that the molsidomine adsorption on the silica materials is controlled by film diffusion. Effect of pH on the diffusion parameters is discussed. - Graphical abstract: The kinetic study showed that the k2 value, the rate constant of pseudo-second order kinetic model, is the highest for molsidomine adsorption on UMS and strongly depends on pH because it is determined by availability and accessibility of the reaction sites of the adsorbents molsidomine binding. Display Omitted - Highlights: • The adsorption capacities of UMS, PhMS and MMS were dependent on the pH. • At all studied pH, the highest molsidomine amount is adsorbed on PhMS. • The highest adsorption rate, k2, is observed onto UMS and strongly depends on pH. • Film diffusion was the likely rate-limiting step in the adsorption process

  18. Diffusion barriers in the kinetics of water vapor adsorption/desorption on activated carbons

    Harding, A.W.; Foley, N.J.; Thomas, K.M. [Univ. of Newcastle upon Tyne (United Kingdom); Norman, P.R.; Francis, D.C. [CBD, Salisbury (United Kingdom)

    1998-07-07

    The adsorption of water vapor on a highly microporous coconut-shell-derived carbon and a mesoporous wood-derived carbon was studied. These carbons were chosen as they had markedly different porous structures. The adsorption and desorption characteristics of water vapor on the activated carbons were investigated over the relative pressure range p/p{degree} = 0--0.9 for temperatures in the range 285--313 K in a static water vapor system. The adsorption isotherms were analyzed using the Dubinin-Serpinski equation, and this provided an assessment of the polarity of the carbons. The kinetics of water vapor adsorption and desorption were studied with different amounts of preadsorbed water for set changes in pressure relative to the saturated vapor pressure (p/p{degree}). The adsorption kinetics for each relative pressure step were compared and used to calculate the activation energies for the vapor pressure increments. The kinetic results are discussed in relation to their relative position on the equilibrium isotherm and the adsorption mechanism of water vapor on activated carbons.

  19. Dye Removal From Textile Waste Water Through The Adsorption By Pumice Used In Stone Washing

    Körlü Aysegül Ekmekçi

    2015-09-01

    Full Text Available Because the waste production is inevitable in almost all industries, the elimination of these wastes is a requirement in terms of environmental regulations and welfare of all the creatures in the future. In this study, the use of the waste pumice stones of a denim washing mill is intended to eliminate the pollutant by a waste material and obtain economic benefits by converting it to the adsorbent. The pollutants in the effluents obtained from three different localisations of waste water treatment system of the same factory were removed through the adsorption. The experimental studies were carried out in three different steps; characterisation of adsorbent before and after adsorption; adsorption isotherm studies and biological oxygen demand (BOD, chemical oxygen demand (COD measurements. Characterisation studies showed that the waste pumice has almost the same structural properties with unused one except the existence of some organic residues coming from washing process. The results of adsorption studies conducted at the adsorbent concentrations changing from 5 to 35 g/l revealed that the decolourisation was initial dye-concentration dependent. According to the BOD and COD measurements, the supernatants obtained at the end of adsorption could be assumed as somewhat polluted and this result indicates that the organic impurities other than indigo were also removed through the adsorption.

  20. Adsorption of indium(III) ions from aqueous solution using chitosan-coated bentonite beads

    Calagui, Mary Jane C. [College of Engineering, Cagayan State University, Cagayan Valley 3500 (Philippines); School of Graduate Studies, Mapua Institute of Technology, Manila 1800 (Philippines); Senoro, Delia B. [School of Graduate Studies, Mapua Institute of Technology, Manila 1800 (Philippines); Kan, Chi-Chuan [Institute of Hot Spring Industrial, Chia Nan University of Pharmacy and Science, Tainan 71710, Taiwan (China); Salvacion, Jonathan W.L. [School of Graduate Studies, Mapua Institute of Technology, Manila 1800 (Philippines); Futalan, Cybelle Morales [Operations Department, Frontier Oil Corporation, Makati City 1229 (Philippines); Wan, Meng-Wei, E-mail: peterwan@mail.chna.edu.tw [Department of Environmental Engineering and Science, Chia Nan University of Pharmacy and Science, Tainan 71710, Taiwan (China)

    2014-07-30

    Highlights: • A more acidic pH causes a decrease in adsorption capacity. • The kinetic data follow the pseudo-second order equation. • Equilibrium data correlated well with Langmuir isotherm. • Removal of indium is a spontaneous and endothermic process. - Abstract: Batch adsorption study was utilized in evaluating the potential suitability of chitosan-coated bentonite (CCB) as an adsorbent in the removal of indium ions from aqueous solution. The percentage (%) removal and adsorption capacity of indium(III) were examined as a function of solution pH, initial concentration, adsorbent dosage and temperature. The experimental data were fitted with several isotherm models, where the equilibrium data was best described by Langmuir isotherm. The mean energy (E) value was found in the range of 1–8 kJ/mol, indicating that the governing type of adsorption of indium(III) onto CCB is essentially physical. Thermodynamic parameters, including Gibbs free energy, enthalpy, and entropy indicated that the indium(III) ions adsorption onto CCB was feasible, spontaneous and endothermic in the temperature range of 278–318 K. The kinetics was evaluated utilizing the pseudo-first order and pseudo-second order model. The adsorption kinetics of indium(III) best fits the pseudo-second order (R{sup 2} > 0.99), which implies that chemical sorption as the rate-limiting step.

  1. Adsorption of indium(III) ions from aqueous solution using chitosan-coated bentonite beads

    Highlights: • A more acidic pH causes a decrease in adsorption capacity. • The kinetic data follow the pseudo-second order equation. • Equilibrium data correlated well with Langmuir isotherm. • Removal of indium is a spontaneous and endothermic process. - Abstract: Batch adsorption study was utilized in evaluating the potential suitability of chitosan-coated bentonite (CCB) as an adsorbent in the removal of indium ions from aqueous solution. The percentage (%) removal and adsorption capacity of indium(III) were examined as a function of solution pH, initial concentration, adsorbent dosage and temperature. The experimental data were fitted with several isotherm models, where the equilibrium data was best described by Langmuir isotherm. The mean energy (E) value was found in the range of 1–8 kJ/mol, indicating that the governing type of adsorption of indium(III) onto CCB is essentially physical. Thermodynamic parameters, including Gibbs free energy, enthalpy, and entropy indicated that the indium(III) ions adsorption onto CCB was feasible, spontaneous and endothermic in the temperature range of 278–318 K. The kinetics was evaluated utilizing the pseudo-first order and pseudo-second order model. The adsorption kinetics of indium(III) best fits the pseudo-second order (R2 > 0.99), which implies that chemical sorption as the rate-limiting step

  2. Bentazone adsorption and desorption on agricultural soils

    Boivin, A.; Cherrier, R.; Schiavon, M

    2005-01-01

    Herbicide fate and transport in soils greatly depend upon adsorption-desorption processes. Batch adsorption and desorption experiments were performed with the herbicide bentazone using 13 contrasted agricultural soil samples. Bentazone was found to be weakly sorbed by the different soils, showing average Freundlich adsorption coefficients (Kf) value of 1.4 ± 2.3 mg1 - nf Lnf kg-1. Soil organic matter content did not have a significant effect on bentazone sorption (r2 = 0.12), whereas natural ...

  3. Solar heat utilization for adsorption cooling device

    Malcho Milan

    2012-04-01

    Full Text Available This article deals with possibility of solar system connection with adsorption cooling system. Waste heat from solar collectors in summer is possible to utilize in adsorption cooling systems, which desorption temperatures have to be lower than temperature of heat transport medium operation temperature. For verification of work of this system was constructed on the Department of power engineering on University of Zilina solar adsorption cooling device.

  4. Solar heat utilization for adsorption cooling device

    Malcho Milan; Patsch Marek; Pilát Peter

    2012-01-01

    This article deals with possibility of solar system connection with adsorption cooling system. Waste heat from solar collectors in summer is possible to utilize in adsorption cooling systems, which desorption temperatures have to be lower than temperature of heat transport medium operation temperature. For verification of work of this system was constructed on the Department of power engineering on University of Zilina solar adsorption cooling device.

  5. Stair-stepped Mound

    2003-01-01

    MGS MOC Release No. MOC2-429, 22 July 2003This April 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a stair-stepped mound of sedimentary rock (right of center) on the floor of a large impact crater in western Arabia Terra near 11.0oN, 4.4oW. Sedimentary rock outcrops are common in the craters of this region. The repeated thickness and uniformity of the layers that make up this mound suggest that their depositional environment was one in which cyclic or episodic events occurred over some period of time. The sediments might have been deposited in a lake, or they may have settled directly out of the atmosphere. Most of the layered material was later eroded away, leaving this circular mound and the other nearby mesas and knobs. The image is illuminated by sunlight from the lower left.

  6. Step & flash imprint lithography

    Douglas J. Resnick

    2005-02-01

    Full Text Available The escalating cost of next generation lithography (NGL is driven in part by the need for complex sources and optics. The cost for a single NGL tool could soon exceed $50 million, a prohibitive amount for many companies. As a result, several research groups are looking at alternative, low-cost methods for printing sub-100 nm features. Many of these methods are limited in their ability to do precise overlay. In 1999, Willson and Sreenivasan developed step and flash imprint lithography (S-FIL™. The use of a quartz template opens up the potential for optical alignment of the wafer and template. This paper reviews several key aspects of the S-FIL process, including template, tool, ultraviolet (UV-curable monomer, and pattern transfer. Two applications are also presented: contact holes and surface acoustic wave (SAW filters.

  7. Adsorption of Cu2+ ions on humic acids

    Cláudio Pereira Jordão

    2001-06-01

    Full Text Available Commercial samples of humic acids (Fluka AG were used to evaluate the adsorption behaviour of Cu2+ ions. The mathematical model described by Langmuir's adsorption equation was applied and the values of the maximum adsorption capacity b and those of the constant related to the bonding energy a were obtained. Aliquots of copper nitrate solutions with different copper concentrations were added to the humic acid suspensions at constant pH values (4.0 and 5.0. The Langmuir isotherms presented two distinct adsorption regions, showing that the adsorptive phenomenon occurs in two distinct steps according to the copper-humic site interaction. Samples of humic acids showed higher maximum adsorption capacity at pH 5 than at pH 4, while the constant a related to bonding energy was higher at pH 4.Amostras de ácidos húmicos de origem comercial (Fluka AG foram usadas na avaliação do comportamento de adsorção de íons Cu2+. O modelo matemático descrito pela equação de adsorção de Langmuir em sua forma linear foi aplicado, obtendo-se os valores da capacidade máxima de adsorção b e da constante relacionada à energia de ligação a. Alíquotas de soluções de nitrato de cobre contendo várias concentrações desse metal foram adicionadas às amostras de suspensões de ácidos húmicos a pH constante. As isotermas apresentaram duas regiões distintas de adsorção, tanto a pH 4 como a pH 5, mostrando que o fenômeno adsortivo ocorre em duas etapas distintas, de acordo com o tipo de interação entre os ácidos húmicos e o cobre. As amostras de ácidos húmicos mostraram maior capacidade máxima de adsorção ao pH 5 do que ao pH 4, enquanto que a constante relacionada à energia de ligação foi maior em pH 4.

  8. Direct NO decomposition over stepped transition-metal surfaces

    Falsig, Hanne; Bligaard, Thomas; Christensen, Claus H.;

    2007-01-01

    We establish the full potential energy diagram for the direct NO decomposition reaction over stepped transition-metal surfaces by combining a database of adsorption energies on stepped metal surfaces with known Bronsted-Evans-Polanyi (BEP) relations for the activation barriers of dissociation of...... diatomic molecules over stepped transition- and noble-metal surfaces. The potential energy diagram directly points to why Pd and Pt are the best direct NO decomposition catalysts among the 3d, 4d, and 5d metals. We analyze the NO decomposition reaction in terms of a Sabatier-Gibbs-type analysis, and we...... demonstrate that this type of analysis yields results that to within a surprisingly small margin of error are directly proportional to the measured direct NO decomposition over Ru, Rh, Pt, Pd, Ag, and An. We suggest that Pd, which is a better catalyst than Pt under the employed reaction conditions, is a...

  9. ADSORPTION OF POLYCHLORINATED BIPHENYLS BY SOILS

    Mihaela Preda

    2010-01-01

    Full Text Available The behavior of polychlorinated biphenyls (PCBs in soil is determined by several factors including adsorption, mobility and degradation. Adsorption, directly or indirectly, influences the other factors. Adsorption process is generally evaluated by using adsorption isotherms representing the relationship between the quantity of substance adsorbed per unit weight and concentration of the substance in solution at equilibrium. They allow determination of the adsorption constant, which is directly proportional to the adsorption of PCBs in soil. PCBs are very insoluble in water, so they tend to accumulate in the lipids. This is the reason why polychlorinated biphenyls are more strongly adsorbed in soils with higher organic matter content. To obtain the adsorption isotherm were used standard solutions of PCB 101with initial concentrations: 0.05, 0.1, 0.5, 1 and 2 g/ml. The adsorption constants were in order: 3072 ml/g for chernozem, 2943 mg/l for chromic luvisol, 998 mg/l for aluviosol and 1443 mg/l for anthrosol. The values of adsorption constants depend on the organic matter and clay content.

  10. Adsorption of phenol on wood surfaces

    Mamleeva, N. A.; Lunin, V. V.

    2016-03-01

    Adsorption of phenol on aspen and pine wood is investigated. It is shown that adsorption isotherms are described by the Langmuir model. The woods' specific surface areas and adsorption interaction constants are determined. It is found that the sorption of phenol on surfaces of aspen and pine is due to Van der Waals interactions ( S sp = 45 m2/godw for aspen and 85 m2/godw for pine). The difference between the adsorption characteristics is explained by properties of the wood samples' microstructures.

  11. Adsorption of radioactive iodide by natural zeolites

    Two natural zeolites from Iranian deposits (clinoptilolite and natrolite) were characterized and their ability for adsorption of iodide from nuclear wastewaters was evaluated. The adsorption behavior was studied on natural and modified zeolites by γ-spectrometry using 131I as radiotracer. Adsorption isotherms and distribution coefficient (Kd) were measured. The results showed that clinoptilolite is a more promising zeolite for removal of iodide compared to natrolite. Furthermore, the adsorption was higher in silver, lead and thallium forms, whereas the lowest desorption was observed in lead modified zeolite. (author)

  12. Adsorptive property of rice husk for uranium

    The adsorption experiments were researched by using the rice husk powder as the adsorbent to remove the U(VI) from aqueous solution. The affecting factors on the U(VI) removal rate such as rice husk particle size, pH, initial concentration, adsorption time, temperature and dosage of adsorbent were evaluated, kinetics and adsorption isotherm law were analyzed, and mechanisms for U(VI) removal were discussed by SEM, FT-IR and energy spectrum analysis. The results show that U(VI) removal rate increases with the decrease of the size of adsorbent, and with the increase of adsorbent dosage and temperature. The process of adsorption can be described by an equation of pseudo 2nd-order mode, and the relation coefficient is 1. The process of adsorption also fits to Freundlich isotherm (R2=0.995 4). The adsorption of uranium on rice husk changes the surface form of rice husk. Hydroxyl, carboxylic, P-O and Si-O are the main functional groups in the reaction with U(VI). The adsorption mechanism is mixture adsorption, including the physical and chemical adsorption. (authors)

  13. Adsorption analysis equilibria and kinetics

    Do, Duong D

    1998-01-01

    This book covers topics of equilibria and kinetics of adsorption in porous media. Fundamental equilibria and kinetics are dealt with for homogeneous as well as heterogeneous particles. Five chapters of the book deal with equilibria and eight chapters deal with kinetics. Single component as well as multicomponent systems are discussed. In kinetics analysis, we deal with the various mass transport processes and their interactions inside a porous particle. Conventional approaches as well as the new approach using Maxwell-Stefan equations are presented. Various methods to measure diffusivity, such

  14. A theoretical and experimental investigation on the adsorption of pentacene on the Cu(322) surface

    Matos, Jeronimo; Sauvage-Simkin, Michele; Coati, Alessandro; Garreau, Yves; Vlad, Alina; Muller, Kathrin; Bendounan, Azzedine; Kara, Abdelkader

    In this study, complementary techniques including density functional theory (DFT), grazing incidence x-ray diffraction (GIXD), and scanning tunneling microscopy (STM) are used to study the surface distortions induced by the adsorption of pentacene on the stepped Cu(322) surface. GIXD measurements are performed for the clean Cu(322) surface and at various coverages of pentacene, up to one monolayer. For the one monolayer case, reciprocal space maps from GIXD measurement suggest the reconstruction of the steps to double the step width and height, with two pentacene molecules present at each terrace. Complementary DFT calculations are carried out, with and without the self-consistent inclusion of vdW interactions, using the optB88-vdW and PBE functionals. Our investigation illustrates a prototype method for conducting future benchmarking studies to assess the accuracy of the current self-consistent vdW functionals when applied to organic molecule adsorption.

  15. Arsenate adsorption and desorption kinetics on a Fe(III)-modified montmorillonite

    Graphical abstract: Arsenate adsorption is much higher in Fe-exchanged montmorillonite (Fe-M) than in Na-exchanged montmorillonite (Na-M). The adsorption takes place in a two-step mechanism. Research highlights: → Adsorption-desorption kinetics of arsenate on a Fe(III)-modified montmorillonite is reported. → Fe(III) species are the responsible for arsenate adsorption. → The adsorption takes place in a two-step mechanism. → Adsorption and desorption studies reflect the presence of externally and internally adsorbed arsenate. → Fe(III) species in Fe-M are more efficient in binding arsenate than in ferrihydrite or goethite. - Abstract: The adsorption-desorption kinetics of arsenate on a Fe(III)-modified montmorillonite (Fe-M) was studied at different arsenate concentrations, pH and stirring rates. The synthesized solid was a porous sample with Fe(III) present as a mix of monomeric and polymeric Fe(III) species in the interlayer and on the external surface. Adsorption took place in a two-step mechanism, with an initial fast binding of arsenate to Fe(III) species at the external surface (half-lives of 1 min or shorter) followed by a slower binding to less accessible Fe(III) species in pores and the interlayer (half-lives of around 1 h). Desorption kinetics also reflected the presence of externally and internally adsorbed arsenate. At pH 6 the maximum adsorbed arsenate was 52 μmol/g, a value that is low as compared to adsorption on ferrihydrite (700 μmol/g) and goethite (192-220 μmol/g). However, since the Fe(III) content of Fe-M is much lower than that of ferrihydrite and goethite, Fe(III) species in Fe-M are more efficient in binding arsenate than in ferrihydrite or goethite (one As atom is attached every 8.95 iron atoms). This high binding efficiency indicates that Fe(III) species are well spread on montmorillonite, forming small oligomeric species or surface clusters containing just a few iron atoms.

  16. Inhibition of step movements near equilibrium for sticky steps

    Akutsu, Noriko

    2012-01-01

    Using a Monte Carlo method on a restricted solid-on-solid model with a point-contact type step-step attraction (p-RSOS model), we show that, at low temperature and near equilibrium, there is an inhibition of giant step movements and a self-pinning of steps. The origin of the inhibition of the step movements is the `step faceting', which is caused by a singularity in the anisotropic surface free energy (surface tension). We show that the singularity in the surface free energy results from the sticky steps by using a statistical-mechanical calculation. Further, from the calculation of a surface stiffness tensor, we show that `step droplets', which are locally merged steps and are caused by a singularity in the surface free energy, roughen the vicinal surface. Near equilibrium, however, the step droplets slow down the step velocity due to the diminishment of kinks in the steps. We present an equation for the transport coefficient, which reproduces the Monte Carlo results.

  17. Adsorption of Polyanion onto Large Alpha Alumina Beads with Variably Charged Surface

    Tien Duc Pham

    2014-01-01

    Full Text Available Adsorption of strong polyelectrolyte, poly(styrenesulfonate, PSS, of different molecular weights onto large α-Al2O3 beads was systematically investigated as functions of pH and NaCl concentrations. The ultraviolet (UV absorption spectra of PSS at different pH and salt concentrations confirmed that the structure of PSS is independent of pH. With the change of molecular weight from 70 kg/mol (PSS 70 to 1000 kg/mol (PSS 1000, adsorption amount of PSS increases and proton coadsorption on the surface of α-Al2O3 decreases at given pH and salt concentration. It suggests that higher molecular weight of PSS was less flat conformation than lower one. The adsorption density of PSS 70 and PSS 1000 decreases with decreasing salt concentrations, indicating that both electrostatic and nonelectrostatic interactions are involved. Experimental results of both PSS 70 and PSS 1000 adsorption isotherms onto α-Al2O3 at different pH and salt concentrations can be represented well by two-step adsorption model. The effects of molecular weight and salt concentration are explained by structure of adsorbed PSS onto α-Al2O3. The influence of added SDS on the isotherms is evaluated from the sequential adsorption. The SDS uptake onto α-Al2O3 in the presence of hemimicelles can prevent the adsorption of PSS at low concentration so that adsorption of PSS reduces with preadsorbed SDS.

  18. Adsorption of organic compounds onto activated carbons from recycled vegetables biomass.

    Mameli, Anna; Cincotti, Alberto; Lai, Nicola; Crisafulli, Carmelo; Sciré, Salvatore; Cao, Giacomo

    2004-01-01

    The removal of organic species from aqueous solution by activated carbons is investigated. The latter ones are prepared from olive husks and almond shells. A wide range of surface area values are obtained varying temperature and duration of both carbonization and activation steps. The adsorption isotherm of phenol, catechol and 2,6-dichlorophenol involving the activated carbons prepared are obtained at 25 degrees C. The corresponding behavior is quantitatively correlated using classical isotherm, whose parameters are estimated by fitting the equilibrium data. A two component isotherm (phenol/2,6-dichlorophenol) is determined in order to test activated carbon behavior during competitive adsorption. PMID:15347202

  19. Life cycle analysis of solvent reduction in pharmaceutical synthesis using continuous adsorption for palladium removal.

    Slater, C Stewart; Savelski, Mariano J; Ruiz-Felix, Marie Nydia

    2013-01-01

    The life cycle emissions associated with the reduction of wastes from an adsorption process to remove palladium complexes in drug manufacture have been evaluated. The study assessed a green improvement to a process step in an active pharmaceutical ingredient synthesis where palladium catalyst is removed from a reaction mixture. The greener process uses a continuous adsorption system, composed of a more efficient adsorbent, consuming less organic solvent and rinse water, which results in less waste disposal. The newer process is also more energy and cost efficient from an operational perspective. There is a 94% reduction in the carbon footprint of the new process when compared to the current operation. PMID:23947697

  20. Single PTCDA molecules on planar and stepped KCl and NaCl(100) surfaces

    Aldahhak, H.; Schmidt, W. G.; Rauls, E.

    2015-11-01

    First principles calculations have been employed to investigate the adsorption of single PTCDA molecules on KCl(100) and NaCl(100) surfaces. The lateral and rotational diffusion barriers as well as the electronic and the geometric aspects of single PTCDA molecules adsorbed on planar terraces as well as at defective steps have been studied in detail.

  1. BEP-relations for N2 dissociation over stepped transition metal and alloy surfaces

    Fronczek-Munter, Ture Rønved; Bligaard, Thomas; Christensen, Claus H.;

    2008-01-01

    We present density functional theory (DFT) calculations for N(2) dissociation on stepped face-centred cubic (211) surface slabs. By using the same crystal structure, the same adsorption site for atomic nitrogen, and the same transition-state bond length of N(2) over a range of pure metal surfaces...

  2. Silicoaluminophosphate nanoporous materials for carbon dioxide adsorption at low concentration

    Arevalo-Hidalgo, Ana G.

    The incorporation of extraframework Sr2+ and Ba2+ cations onto silicoaluminophosphate (SAPO-34) zeolitic materials has been proven to influence their adsorptive properties. In this study, three approaches were employed to increase the cation content and, therefore, the material adsorption capacity: a multi-step liquid-phase ion exchange (LSIE), a novel coupled partial detemplation / solid-state ion exchange (PD-SSIE) and a coupled SSIE-LSIE. The use of multi-step LSIE resulted in an increase in cation content per unit cell, but the presence of solvated species and the interaction between the in-going cation and the available sites within the structure resulted in an equilibrium limitation. On the other hand, the introduction of Sr2+ and Ba2+ cations via SSIE was found to be heavily dependent on the nature of the starting material, the temperature of the solid-state reaction, and the amount of salt used (i.e. available sites). Among the different SSIE variants, the sample prepared via PD-SSIE exhibited the best CO2 uptake capacity at moderate gas partial pressures. Finally, the preparation of Sr2+-SAPO-34 and Ba2+-SAPO-34 via SSIE-LSIE resulted in materials with superior CO2 adsorption capacity at any pressure. Furthermore, experimental and theoretical calculations studies indicated that Sr2+ and Ba2+ cations were preferentially located on Site II' extra-framework positions, which allows for the development of stronger interactions with CO2 molecules. This was confirmed by 1H and 23Na MAS NMR studies, which allowed us to elucidate the presence and location of H+ and Na+ cations. This was essential to determine the amount and location of sites available for Sr2+ and Ba2+ ion exchange.

  3. The transmission interferometric adsorption sensor

    This paper describes a high-speed adsorption sensor based on thin-film interference at the interfaces. The sensor can be used as a stand-alone instrument or in combination with a direct surface force measurement, which yields a wide range of additional information on molecular interactions on adsorbed films. The achieved mass resolution of the presented method (1-10 ng cm-2 Hz-1/2) is comparable to or better than other modern bio-sensors. The dependence of mass resolution on various factors is presented and demonstrated in a number of relevant examples. The described method is suitable for the implementation of a low-cost bio-sensor with a minimal number of optical elements. The measurement spot size is one micrometre or more and sampling rates >10 Hz are readily possible. In contrast to other bio-sensors, the signal baseline has a remarkable long-term stability since the measured signal is virtually independent of refractive index changes in the fluid medium above the sensor surface. In combination with an optical spectral correlation method, the classical computer calculations are substituted by an optical calculator and a label-free real-time imaging adsorption sensor is realized. We demonstrate sensor operation both inside the extended surface forces apparatus as well as in a stand-alone bio-sensor configuration. As a final point, we illustrate the imaging capability of this new sensor technology on a patterned bio-functionalized surface. (review article)

  4. Surfactant adsorption to soil components and soils.

    Ishiguro, Munehide; Koopal, Luuk K

    2016-05-01

    Soils are complex and widely varying mixtures of organic matter and inorganic materials; adsorption of surfactants to soils is therefore related to the soil composition. We first discuss the properties of surfactants, including the critical micelle concentration (CMC) and surfactant adsorption on water/air interfaces, the latter gives an impression of surfactant adsorption to a hydrophobic surface and illustrates the importance of the CMC for the adsorption process. Then attention is paid to the most important types of soil particles: humic and fulvic acids, silica, metal oxides and layered aluminosilicates. Information is provided on their structure, surface properties and primary (proton) charge characteristics, which are all important for surfactant binding. Subsequently, the adsorption of different types of surfactants on these individual soil components is discussed in detail, based on mainly experimental results and considering the specific (chemical) and electrostatic interactions, with hydrophobic attraction as an important component of the specific interactions. Adsorption models that can describe the features semi-quantitatively are briefly discussed. In the last part of the paper some trends of surfactant adsorption on soils are briefly discussed together with some complications that may occur and finally the consequences of surfactant adsorption for soil colloidal stability and permeability are considered. When we seek to understand the fate of surfactants in soil and aqueous environments, the hydrophobicity and charge density of the soil or soil particles, must be considered together with the structure, hydrophobicity and charge of the surfactants, because these factors affect the adsorption. The pH and ionic strength are important parameters with respect to the charge density of the particles. As surfactant adsorption influences soil structure and permeability, insight in surfactant adsorption to soil particles is useful for good soil management. PMID

  5. SPAR-H Step-by-Step Guidance

    April M. Whaley; Dana L. Kelly; Ronald L. Boring; William J. Galyean

    2012-06-01

    Step-by-step guidance was developed recently at Idaho National Laboratory for the US Nuclear Regulatory Commission on the use of the Standardized Plant Analysis Risk-Human Reliability Analysis (SPAR-H) method for quantifying Human Failure Events (HFEs). This work was done to address SPAR-H user needs, specifically requests for additional guidance on the proper application of various aspects of the methodology. This paper overviews the steps of the SPAR-H analysis process and highlights some of the most important insights gained during the development of the step-by-step directions. This supplemental guidance for analysts is applicable when plant-specific information is available, and goes beyond the general guidance provided in existing SPAR-H documentation. The steps highlighted in this paper are: Step-1, Categorizing the HFE as Diagnosis and/or Action; Step-2, Rate the Performance Shaping Factors; Step-3, Calculate PSF-Modified HEP; Step-4, Accounting for Dependence, and; Step-5, Minimum Value Cutoff.

  6. Molecular Simulation of Adsorption in Microporous Materials

    Yiannourakou M.; Ungerer P.; Leblanc B.; Rozanska X.; Saxe P.; Vidal-Gilbert S.; Gouth F.; Montel F.

    2013-01-01

    The development of industrial software, the decreasing cost of computing time, and the availability of well-tested forcefields make molecular simulation increasingly attractive for chemical engineers. We present here several applications of Monte-Carlo simulation techniques, applied to the adsorption of fluids in microporous solids such as zeolites and model carbons (pores < 2 nm). Adsorption was computed in the Grand Canonical ensemble ...

  7. Adsorption of arsenic and boron by soil

    Sakata, M.

    1986-01-01

    The author reports a study of the soil adsorption of As (trivalent) and B leached from coal ash. It has been found that the amount of adsorption is greatly affected by the pH of the solution. Maximum adsorption of As occurred from solutions with pH of about 8, while pH 8-9 resulted in maximum B adsorption. Furthermore, the As adsorption is related to the quantity of iron oxides and hydrated iron oxides in the soil, while the adsorption of B is related to the quantity of hydrated aluminium oxides and allophanes. Within the range of concentrations studied, the adsorption isotherm for As obeyed the Langmuir equation, and the B isotherm, that of Freundlich. At low concentrations, both elements conform to the Henry adsorption isotherm. The author also reports that the impact on ground water of elements such as As and B leached from coal ash can be conveniently predicted or evaluated by means of a diffusive flow model. 30 references, 14 figures, 3 tables.

  8. Study on copper adsorption on olivine

    2001-01-01

    The copper adsorption on olivine supplied by A/S Olivine production plant at Aheim in western Norway has been studied. The factors which affect the uptake of copper have been evaluated. The results reveal that the equilibrium pH in aqueous solution has the greatest influence on the copper adsorption thanks to the competitive adsorption between proton and copper ions, and the adsorption of copper to olivine increases rapidly with the pH increasing from 4 to 6. The initial copper concentration and olivine dose also possess significant effect on copper adsorption. The adsorption efficieny of copper increases with the increase of olivine dose or the decrease of initial copper concentration at the same pH. The ionic strength effect on the adsorption has also been investigated, but it owns little effect on the adsorption process of copper due to the formation of inner sphere surface complexation of copper on olivine. The experimental data show that olivine has a high acid buffer capacity and is an effective adsorbent for copper.

  9. Adsorption Kinetic of 8-Hydroxyquinoline on Malachite

    Oprea, Gabriela; Angela MICHNEA; Cristina MIHALI

    2007-01-01

    Influence of temperature and collector concentration on its adsorption rate on mineral surface was studied as regarding to the 8-hydroxyquinoline/malachite system. Theoretical equations as well as experimental data may be useful to estimate the adsorption rate and kinetics connected to the conditioning stage in mineral flotation in order to optimise the selectivity and the recovery of the desired mineral.

  10. Adsorption of ferrous ions onto montmorillonites

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

    2015-04-01

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

  11. Development of facile property calculation model for adsorption chillers based on equilibrium adsorption cycle

    Yano, Masato; Hirose, Kenji; Yoshikawa, Minoru; Thermal management technology Team

    Facile property calculation model for adsorption chillers was developed based on equilibrium adsorption cycles. Adsorption chillers are one of promising systems that can use heat energy efficiently because adsorption chillers can generate cooling energy using relatively low temperature heat energy. Properties of adsorption chillers are determined by heat source temperatures, adsorption/desorption properties of adsorbent, and kinetics such as heat transfer rate and adsorption/desorption rate etc. In our model, dependence of adsorption chiller properties on heat source temperatures was represented using approximated equilibrium adsorption cycles instead of solving conventional time-dependent differential equations for temperature changes. In addition to equilibrium cycle calculations, we calculated time constants for temperature changes as functions of heat source temperatures, which represent differences between equilibrium cycles and real cycles that stemmed from kinetic adsorption processes. We found that the present approximated equilibrium model could calculate properties of adsorption chillers (driving energies, cooling energies, and COP etc.) under various driving conditions quickly and accurately within average errors of 6% compared to experimental data.

  12. Step-step interactions on GaAs (110) nanopatterns

    Galiana, B.; Benedicto, M.; Tejedor, P. [Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Sor Juana Ines de la Cruz 3, 28049 Madrid (Spain)

    2013-01-14

    The step-step interactions on vicinal GaAs (110) surface patterns have been extracted from the quantitative analysis of the terrace width distribution (TWD). We have specifically studied the interactions in near-equilibrium faceting and kinetics-driven step bunching and meandering formed by spontaneous self-organization or through the modification of GaAs growth kinetics by atomic hydrogen. We show that the experimental TWDs determined from atomic force microscopy measurements can be accurately described by a weighed sum of a generalized Wigner distribution and several Gaussians. The results of our calculations indicate that straight facets are formed during high temperature homoepitaxy due to attractive interactions between [110] steps. At low temperatures, steady state attractive interactions in [110] step bunches are preceded by a transition regime dominated by entropic and energetic repulsions between meandering [11n]-type steps (n {>=} 2), whose population density exceeds that of the [110] bunched steps. In addition, it has been found that atomic H reduces the attractive interactions between [110] bunched steps and enhances entropic and dipole-induced energetic repulsions between H-terminated [11n] steps through the inhibition of As-As bond formation at step edges. Our analysis has evidenced a correlation between the value of the adjustable parameter that accounts in our model for the specific weight of the secondary peaks in the TWD ({beta}) and the extent of transverse meandering on the vicinal surface.

  13. Adsorption of Nile Blue A from Wastewater Using Magnetic Multi-Walled Carbon Nanotubes: Kinetics and Equilibrium Studies

    Mehrnaz Ghoochian

    2016-04-01

    Full Text Available Background: Synthetic dyes are serious pollutants and wide ranges of methods have been employed for their removal from aquatic systems. We studied the adsorption of "Nile blue A" (NBA, an anionic dye, from aqueous solution by oxidized multi-walled carbon nanotubes (MWCNTs. Methods: Scanning electron microscope and Fourier transform infrared spectroscopy were used to characterize function groups produced at MWCNTs surface. Kinetics and adsorption isotherms of NBA, the effect of temperature, pH, contact time and initial dosage of nanotubes on the adsorption capacity were also assessed. The experimental data were analyzed by Langmuir and Freundlich models. Results: Most of the dye was removed in the first 5 min and best adsorption percentage was at pH 7.0. The equilibrium reached at 45 min. The experimental data were analyzed by Langmuir and Freundlich models and the results fitted well with the Freundlich model. The adsorption kinetic data were analyzed using first-order and the pseudo-second order model and the adsorption kinetic data of NBA dye onto MWCNTs fitted the pseudo-second order model. The maximum adsorption capacity was obtained as 169.49 mg g-1. Conclusion: Freundlich model suggested that the adsorption process followed heterogeneous distribution onto MWCNTs and pseudo-second model of adsorption implied that chemical processes controlled the rate-controlling step. Oxidized MWCNTs could be used as an effective adsorbent for the removal of "Nile Blue A" dye. Oxidization of MWCNTs by nitric acid, improves the efficiency of NBA removal due to increases in functional groups and total number of adsorption sites.

  14. Faceting diagram for sticky steps

    Noriko Akutsu

    2016-03-01

    Full Text Available Faceting diagrams for the step-faceting zone, the step droplet zone, and the Gruber-Mullins-Pokrovsky-Talapov (GMPT zone for a crystal surface are obtained by using the density matrix renormalization group method to calculate the surface tension. The model based on these calculations is the restricted solid-on-solid (RSOS model with a point-contact-type step-step attraction (p-RSOS model on a square lattice. The point-contact-type step-step attraction represents the energy gain obtained by forming a bonding state with orbital overlap at the meeting point of the neighboring steps. In the step-faceting zone, disconnectedness in the surface tension leads to the formation of a faceted macrostep on a vicinal surface at equilibrium. The disconnectedness in the surface tension also causes the first-order shape transition for the equilibrium shape of a crystal droplet. The lower zone boundary line (ZBL, which separates the step-faceting zone and the step droplet zone, is obtained by the condition γ 1 = lim n → ∞ γ n / n , where γn is the step tension of the n-th merged step. The upper ZBL, which separates the GMPT zone and the step droplet zone, is obtained by the condition Aq,eff = 0 and Bq,eff = 0, where Aq,eff and Bq,eff represent the coefficients for the | q → | 2 term and the | q → | 3 term, respectively, in the | q → | -expanded form of the surface free energy f eff ( q → . Here, q → is the surface gradient relative to the (111 surface. The reason why the vicinal surface inclined in the 〈101〉 direction does not exhibit step-faceting is explained in terms of the one-dimensional spinless quasi-impenetrable attractive bosons at absolute zero.

  15. Faceting diagram for sticky steps

    Akutsu, Noriko

    2016-03-01

    Faceting diagrams for the step-faceting zone, the step droplet zone, and the Gruber-Mullins-Pokrovsky-Talapov (GMPT) zone for a crystal surface are obtained by using the density matrix renormalization group method to calculate the surface tension. The model based on these calculations is the restricted solid-on-solid (RSOS) model with a point-contact-type step-step attraction (p-RSOS model) on a square lattice. The point-contact-type step-step attraction represents the energy gain obtained by forming a bonding state with orbital overlap at the meeting point of the neighboring steps. In the step-faceting zone, disconnectedness in the surface tension leads to the formation of a faceted macrostep on a vicinal surface at equilibrium. The disconnectedness in the surface tension also causes the first-order shape transition for the equilibrium shape of a crystal droplet. The lower zone boundary line (ZBL), which separates the step-faceting zone and the step droplet zone, is obtained by the condition γ 1 = lim n → ∞ γ n / n , where γn is the step tension of the n-th merged step. The upper ZBL, which separates the GMPT zone and the step droplet zone, is obtained by the condition Aq,eff = 0 and Bq,eff = 0, where Aq,eff and Bq,eff represent the coefficients for the | q → | 2 term and the | q → | 3 term, respectively, in the | q → | -expanded form of the surface free energy f eff ( q → ) . Here, q → is the surface gradient relative to the (111) surface. The reason why the vicinal surface inclined in the direction does not exhibit step-faceting is explained in terms of the one-dimensional spinless quasi-impenetrable attractive bosons at absolute zero.

  16. Adsorption on the carbon nanotubes

    DING Yi; YANG Xiao-bao; NI Jun

    2006-01-01

    Adsorption on single walled carbon nanotubes (SWCNTs) is a subject of growing experimental and theoretical interest.The possible adsorbed patterns of atoms and molecules on the single-walled carbon nanotubes vary with the diameters and chirality of the tubes due to the confinement.The curvature of the carbon nanotube surface enlarges the distance of the adsorbate atoms and thus enhances the stability of high coverage structures of adsorbate.There exist two novel high-coverage stable structures of potassium adsorbed on SWCNTs,which are not stable on graphite.The electronic properties of SWCNTs can be modified by adsorbate atoms and metal-semiconductor and semiconductor-semi-conductor transitions can be achieved by the doping of alkali atoms.

  17. ADSORPTION OF PROTEIN ON NANOPARTICLES

    WU Qi

    1994-01-01

    The adsorption of protein on nanoparticles was studied by using dynamic light scattering to measure the hydrodynamic size of both pure protein and nanoparticles adsorbed with different amounts of protein. The thickness of the adsorbed protein layer increases as protein concentration, but decreases as the initial size of nanoparticles. After properly scaling the thickness with the initial diameter, we are able to fit all experimental data with a single master curve. Our experimental results suggest that the adsorbed proteins form a monolayeron the nanoparticle surface and the adsorbed protein molecules are attached to the particle surface at many points through a possible hydrogen-bonding. Our results also indicate that as protein concentration increases, the overall shape of the adsorbed protein molecule continuously changes from a flat layer on the particle surface to a stretched coil extended into water. During the change, the hydrodynamic volume of the adsorbed protein increases linearly with protein concentration.

  18. Adsorption and release of micronutrients by humin extracted from peat samples

    Goveia, Danielle; Melo, Camila de A.; Oliveira, Lilian K. de; Rocha, Julio Cesar [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Araraquara, SP (Brazil). Instituto de Quimica; Fraceto, Leonardo F.; Rosa, Andre Henrique, E-mail: ahrosa@sorocaba.unesp.br [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Sorocaba, SP (Brazil). Departamento de Engenharia Ambiental; Dias Filho, Newton Luiz [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Ilha Solteira, SP (Brazil). Departamento de Fisica e Quimica

    2013-05-15

    The objective of this work was to investigate the adsorption of micronutrients in humin and to verify the ability to release these elements in water. The first step was to determine the adsorption capacity of humin for several essential plant micronutrients and check the kinetic parameters. The order of adsorption was Zn < Ni < Co < Mn < Mo < Cu < Fe, whereas Zn showed maximum values of ca. 2.5 mg g-1 and Fe values of ca. 0.5 mg g-1 for systems containing 1 g of humin. Iron presented higher percentages of release (ca. 100%) and Co the lowest percentages (0.14%). The findings suggested that the use of humin enriched with micronutrients can be a promising alternative for the fertilization of agricultural soils, with the additional benefit of incorporating organic matter present in the form of humic substances into the soil and improving the agricultural productivity. (author)

  19. Kinetics of Adsorption of Cationic Surfactants at Silica-Water Interface.

    Biswas; Chattoraj

    1998-09-01

    The kinetics of adsorption of cationic surfactants (CTAB, MTAB and DTAB) at silica surface has been studied at various values of bulk surfactant concentration (Ct2), pH, ionic strength, and temperature and in presence of different electrolytes and urea. The adsorption process has been found to follow a two-step first-order kinetic rate equation with two different rate constants k1 and k2. From the variation of k1 and k2 with temperature, values of energies of activation Ea1 and Ea2 for both the kinetic steps have been evaluated. The corresponding values of enthalpies of activation (DeltaH1# and DeltaH2#), entropies of activation (DeltaS1# and DeltaS2#) have been evaluated using Eyring's equation for absolute reaction rate. It has been found that for both the kinetic steps, DeltaH1# 1# and DeltaH2# 2#, which means that activation reaction is largely entropy controlled. Again, for both kinetic steps, DeltaH# varies linearly with TavDeltaS#, and DeltaG1# and DeltaG2# vary between 70 and 88 kJ/mole of surfactant, respectively. Thus there is a entropy-enthalpy compensation effect in the adsorption process. Copyright 1998 Academic Press. PMID:9710495

  20. Separation of toxic rhodamine B from aqueous solution using an efficient low-cost material, Azolla pinnata, by adsorption method.

    Kooh, Muhammad Raziq Rahimi; Lim, Linda B L; Lim, Lee Hoon; Dahri, Muhammad Khairud

    2016-02-01

    This study investigated the potential of untreated Azolla pinnata (AP) to remove toxic rhodamine B (RB) dye. The effects of adsorbent dosage, pH, ionic strength, contact time, and concentration were studied. Experiments involving the effects of pH and ionic strength indicated that hydrophobic-hydrophobic interactions might be the dominant force of attraction for the RB-AP adsorption system. The kinetics modelling of the kinetics experiment showed that pseudo-second-order best represented the adsorption process. The Weber-Morris intraparticle diffusion model showed that intraparticle diffusion is not the rate-limiting step, while the Boyd model suggested that film diffusion might be rate-limiting. The adsorption isotherm model, Langmuir, best represented the adsorption process, and the maximum adsorption capacity was predicted to be 72.2 and 199.7 mg g(-1) at 25 and 65 °C, respectively. Thermodynamics study indicates spontaneity, endothermic and physisorption-dominant adsorption process. The adsorbents were regenerated to satisfactory level with distilled water, HNO3 and NaOH. Pre-treatment of adsorbent with oxalic acid, citric acid, NaOH, HCl and phosphoric acid was investigated but the adsorption capacity was less than the untreated AP. PMID:26797814

  1. Adsorption of Cu(II), Co(II), and Ni(II) ions by modified magnetic chitosan chelating resin

    Cross-linked magnetic chitosan-isatin Schiff's base resin (CSIS) was prepared for adsorption of metal ions. CSIS obtained was investigated by means of FTIR, 1H NMR, wide-angle X-ray diffraction (WAXRD), magnetic properties and thermogravimetric analysis (TGA). The adsorption properties of cross-linked magnetic CSIS resin toward Cu2+, Co2+ and Ni2+ ions were evaluated. Various factors affecting the uptake behavior such as contact time, temperature, pH and initial concentration of the metal ions were investigated. The kinetic parameters were evaluated utilizing the pseudo-first-order and pseudo-second-order. The equilibrium data were analyzed using the Langmuir, Freundlich, and Tempkin isotherm models. The adsorption kinetics followed the mechanism of the pseudo-second-order equation for all systems studied, evidencing chemical sorption as the rate-limiting step of adsorption mechanism and not involving a mass transfer in solution. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 103.16, 53.51, and 40.15 mg/g for Cu2+, Co2+ and Ni2+ ions, respectively. Cross-linked magnetic CSIS displayed higher adsorption capacity for Cu2+ in all pH ranges studied. The adsorption capacity of the metal ions decreased with increasing temperature. The metal ion-loaded cross-linked magnetic CSIS were regenerated with an efficiency of greater than 88% using 0.01-0.1 M ethylendiamine tetraacetic acid (EDTA).

  2. Adsorption of Cu(II), Co(II), and Ni(II) ions by modified magnetic chitosan chelating resin.

    Monier, M; Ayad, D M; Wei, Y; Sarhan, A A

    2010-05-15

    Cross-linked magnetic chitosan-isatin Schiff's base resin (CSIS) was prepared for adsorption of metal ions. CSIS obtained was investigated by means of FTIR, (1)H NMR, wide-angle X-ray diffraction (WAXRD), magnetic properties and thermogravimetric analysis (TGA). The adsorption properties of cross-linked magnetic CSIS resin toward Cu(2+), Co(2+) and Ni(2+) ions were evaluated. Various factors affecting the uptake behavior such as contact time, temperature, pH and initial concentration of the metal ions were investigated. The kinetic parameters were evaluated utilizing the pseudo-first-order and pseudo-second-order. The equilibrium data were analyzed using the Langmuir, Freundlich, and Tempkin isotherm models. The adsorption kinetics followed the mechanism of the pseudo-second-order equation for all systems studied, evidencing chemical sorption as the rate-limiting step of adsorption mechanism and not involving a mass transfer in solution. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 103.16, 53.51, and 40.15mg/g for Cu(2+), Co(2+) and Ni(2+) ions, respectively. Cross-linked magnetic CSIS displayed higher adsorption capacity for Cu(2+) in all pH ranges studied. The adsorption capacity of the metal ions decreased with increasing temperature. The metal ion-loaded cross-linked magnetic CSIS were regenerated with an efficiency of greater than 88% using 0.01-0.1M ethylendiamine tetraacetic acid (EDTA). PMID:20122793

  3. Pseudo-first order and second order kinetics study of erbium ions adsorption on activated charcoal from aqueous solutions

    The adsorption of Erbium (Er) ions on activated charcoal is carried out at temperatures 10-40 deg. C from aqueous solutions to understand the kinetics behavior. The results shows that the adsorption of erbium ions increases with the rise in temperature and the adsorption process is physical in nature and attains equilibrium in about 60 minutes. A comparison of the kinetics models on the overall adsorption rate indicates that the Er/AC system is best described by the pseudo second order rate model than the pseudo first order model. The applicability of the Waber and Morris equation to the adsorption data, confirms that the intra-particle diffusion is not only the main rate determining step through out the adsorption process, but the boundary layer diffusion is also play significant role in rate determination. The Waber and Morris equation best suited to the adsorption process in the whole range is in the form of: qt = k/sub i,d/ t/sup 0.5/ + C, where ki,d is the intra-particle diffusion rate constant (g.g/sup -1/. min/sup -0.5/) and C is the constant related to boundary layer diffusion. Both these parameters were determined from the slopes and intercepts of straight lines of plots of qt vs. t/sup 0.5/ respectively. The value of C is proportional to the extent of boundary layer thickness. (author)

  4. Preparation, characterization and dye adsorption properties of γ-Fe2O3/SiO2/chitosan composite

    A γ-Fe2O3/SiO2/chitosan composite was prepared by water-in-oil emulsification, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Effects of various factors, including adsorbent dosage, initial dye concentration, solution pH, and competing anions, on the adsorption of methyl orange from aqueous solutions by the resulting composite were studied by batch adsorption experiments. The adsorption kinetics was found to follow the pseudo-second-order kinetic model, and intraparticle diffusion was related to the adsorption, but not as a sole rate-controlling step. The equilibrium adsorption data were well described by the Freundlich isotherm model. Evaluation of the thermodynamic parameters ΔG°, ΔH°, and ΔS° revealed that the adsorption process was naturally feasible, spontaneous, and exothermic. The composite was proven to be efficient, suitable and promising for the removal of methyl orange from aqueous solutions since it has a relatively higher adsorption capacity than other low-cost adsorbents.

  5. Adsorption of organic matter contained in industrial phosphoric acid onto bentonite: Batch contact time and kinetic study

    The soluble organic matter present in industrial phosphoric acid can strongly affect the uranium recovery during its solvent extraction by forming stable foams and emulsions. The removal of these organics is an important step both for the production of decontaminated fertilizers and the successful recovery of uranium. The equilibrium isotherms of organic matter adsorption onto bentonite show that the data correlated well with freundlich's model and that the adsorption is physical in nature. the maximum monomolecular capacity (Qo) according to the Langmuir model is 153 mg/g for an initial organic matter concentration of 251.5 mg/1, at 30 oC. The operating parameters (agitation speed, solid/liquid ratio, temperature, particle size and initial organic matter concentration) influenced the rate of adsorption. The adsorption isotherm of uranium onto bentonite exhibits and anomalous shape similar to the Z-type isotherm reported by Giles et al

  6. Adsorption and Step Elution of Urokinase Using, Affinity Chromatography -Comparison of Data with Rate Model Simulation

    MohammadRezaAboudzadehRovais; JiawenZhu; BinWu

    2004-01-01

    A non-equilibrium chromatographic rate model was employed to simulate the affinity chromatography of urokinase. The chromatography process was developed to a yield of high purity product of urokinase from crude materials. The affinity gel used in the process was prepared by an epichlorohydrin-activation method using epichlorohydrin activated Sepharose 4B as a matrix and p-aminobenzamidine as a ligand. The chromatographic process were numerically simulated and analyzed with the aid of VERSE-LC computer simulator. Considering the basic principles, rate model with the back mixing in column inlet was utilized in simulating and studying the effect of the column inlet pattern on other parameters. Comparison of the simulation results with the experimental data showed that the rate model can be used to describe the affinity chromatography of urokinase in a fixed bed column with satisfactory accuracy.

  7. Adsorption of hydrocarbons in chalk reservoirs

    Madsen, L.

    1996-12-31

    The present work is a study on the wettability of hydrocarbon bearing chalk reservoirs. Wettability is a major factor that influences flow, location and distribution of oil and water in the reservoir. The wettability of the hydrocarbon reservoirs depends on how and to what extent the organic compounds are adsorbed onto the surfaces of calcite, quartz and clay. Organic compounds such as carboxylic acids are found in formation waters from various hydrocarbon reservoirs and in crude oils. In the present investigation the wetting behaviour of chalk is studied by the adsorption of the carboxylic acids onto synthetic calcite, kaolinite, quartz, {alpha}-alumina, and chalk dispersed in an aqueous phase and an organic phase. In the aqueous phase the results clearly demonstrate the differences between the adsorption behaviour of benzoic acid and hexanoic acid onto the surfaces of oxide minerals and carbonates. With NaCl concentration of 0.1 M and with pH {approx_equal} 6 the maximum adsorption of benzoic acid decreases in the order: quartz, {alpha}-alumina, kaolinite. For synthetic calcite and chalk no detectable adsorption was obtaind. In the organic phase the order is reversed. The maximum adsorption of benzoic acid onto the different surfaces decreases in the order: synthetic calcite, chalk, kaolinite and quartz. Also a marked difference in adsorption behaviour between probes with different functional groups onto synthetic calcite from organic phase is observed. The maximum adsorption decreases in the order: benzoic acid, benzyl alcohol and benzylamine. (au) 54 refs.

  8. Adsorption of Iminodiacetic Acid Resin for Lutetium

    熊春华; 姚彩萍; 王惠君

    2004-01-01

    The adsorption behavior and mechanism of a novel chelate resin,iminodiacetic acid resin(IDAAR) for Lu(Ⅲ) were investigated.The statically saturated adsorption capacity is 210.8 mg·g-1 at 298 K in HAc-NaAc medium.The Lu(Ⅲ) adsorbed on IDAAR can be eluted by 0.5 mol·L-1 HCl and the elution percentage reaches 96.5%.The resin can be regenerated and reused without obvious decrease in adsorption capacity.The apparent adsorption rate constant is k298=2.0×10-5 s-1.The adsorption behavior of IDAAR for Lu(Ⅲ) obeys the Freundlich isotherm.The thermodynamic adsorption parameters,enthalpy change ΔH,free energy change ΔG and entropy change ΔS of IDAAR for Lu(Ⅲ) are 13.1 kJ·mol-1,-1.37 kJ·mol-1 and 48.4 J·mol-1·K-1,respectively.The apparent activation energy is Ea=31.3 kJ·mol-1.The molar coordination ratio of the functional group of IDAAR to Lu(Ⅲ) is about 3∶1.The adsorption mechanism of IDAAR for Lu(Ⅲ) was examined by chemical method and IR spectrometry.

  9. Arsenic Adsorption Equilibrium Concentration and Adsorption Rate of Activated Carbon Coated with Ferric-Aluminum Hydroxides

    Zhang, M.; Sugita, H.; Oguma, T.; Hara, J.; Takahashi, S.

    2015-12-01

    In some areas of developing countries, ground or well water contaminated with arsenic has been reluctantly used as drinking water. It is highly desirable that effective and inexpensive arsenic removal agents should be developed and provided to reduce the potential health risk. Previous studies demonstrated that activated carbon coated with ferric-aluminum hydroxides (Fe-Al-C) has high adsorptive potential for removal of arsenic. In this study, a series of experiments using Fe-Al-C were carried to discuss adsorption equilibrium time, adsorption equilibrium concentration and adsorption rate of arsenic for Fe-Al-C. Fe-Al-C used in this study was provided by Astec Co., Ltd. Powder reagent of disodium hydrogen arsenate heptahydrate was dissolved into ion-exchanged water. The solution was then further diluted with ion-exchanged water to be 1 and 10 mg/L as arsenic concentration. The pH of the solution was adjusted to be around 7 by adding HCl and/or NaOH. The solution was used as artificial arsenic contaminated water in two types of experiments (arsenic adsorption equilibrium and arsenic adsorption rate tests). The results of the arsenic equilibrium tests were showed that a time period of about 3 days to reach apparent adsorption equilibrium for arsenic. The apparent adsorption equilibrium concentration and adsorbed amount of arsenic on Fe-Al-C adsorbent could be estimated by application of various adsorption isotherms, but the distribution coefficient of arsenic between solid and liquid varies with experimental conditions such as initial concentration of arsenic and addition concentration of adsorbent. An adsorption rate equation that takes into account the reduction in the number of effective adsorption sites on the adsorbent caused by the arsenic adsorption reaction was derived based on the data obtained from the arsenic adsorption rate tests.

  10. Reconstruction of steps on the Cu(111) surface induced by sulfur

    A rich menagerie of structures is identified at 5 K following adsorption of low coverages (≤0.05 monolayers) of S on Cu(111) at room temperature. This paper emphasizes the reconstructions at the steps. The A-type close-packed step has 1 row of S atoms along its lower edge, where S atoms occupy alternating pseudo-fourfold-hollow (p4fh) sites. Additionally, there are 2 rows of S atoms of equal density on the upper edge, bridging a row of extra Cu atoms, together creating an extended chain. The B-type close-packed step exhibits an even more complex reconstruction, in which triangle-shaped groups of Cu atoms shift out of their original sites and form a base for S adsorption at (mostly) 4fh sites. We propose a mechanism by which these triangles could generate Cu–S complexes and short chains like those observed on the terraces

  11. HTSC-Josephson step contacts

    In this work the properties of josephson step contacts are investigated. After a short introduction into Josephson step contacts the structure, properties and the Josphson contacts of YBa2Cu3O7-x high-Tc superconductors is presented. The fabrication of HTSC step contacts and the microstructure is discussed. The electric properties of these contacts are measured together with the Josephson emission and the magnetic field dependence. The temperature dependence of the stationary transport properties is given. (WL)

  12. Annular purpura and step aerobics.

    Allan, S J; Humphreys, F; Buxton, P K

    1994-09-01

    Step aerobic classes are at present one of the most popular forms of exercise undertaken by young adults. To date no dermatological abnormalities have been described in people regularly performing step aerobics. We describe a case in which a healthy young woman developed an extensive pigmented purpuric eruption 4 weeks after commencing regular step aerobic classes. The eruption resolved completely 8 weeks after regular exercise was ceased. PMID:7955503

  13. Adsorption of UO22+ from aqueous solution onto copolymers of styrene and maleic anhydride

    The copolymers of styrene and maleic anhydride resin (PSt/MA) was synthesized by free radical polymerization and characterized by means of FTIR. It is shown that the PSt/MA copolymer has rather strong coordination ability to UO22+ ions by chelation with the carboxylate group, and the microstructures of the U(VI)-PSt/MA complexes can be well controlled. The influence factors on UO22+ ions were also investigated and described in detail, such as contact time, solid/liquid ratio, pH value, ethanol content, and initial concentration. It was found that the maximum adsorption quantity of UO22+ was 831 mg/g. Experiments show that PSt/MA can recover UO22+ ions with high adsorption selectively from a simulated industry solution containing Ca2+ and Mg2+ as impurities. The adsorption kinetic data were best described by the pseudo-second-order equation, indicating that the chemical adsorption was the rate-limiting step. And there are very good correlation coefficients of linearized equations for Langmuir model, which indicated that the sorption isotherm of the PSt/MA for UO22+ can be fitted to the Langmuir model. After five times of repeated tests for the hydrogel it still remained its excellent adsorption. (author)

  14. Adsorption of methyl orange from aqueous solution onto calcined Lapindo volcanic mud

    In this study, calcined Lapindo volcanic mud (LVM) was used as an adsorbent to remove an anionic dye, methyl orange (MO), from an aqueous solution by the batch adsorption technique. Various conditions were evaluated, including initial dye concentration, adsorbent dosage, contact time, solution pH, and temperature. The adsorption kinetics and equilibrium isotherms of the LVM were studied using pseudo-first-order and -second-order kinetic equations, as well as the Freundlich and Langmuir models. The experimental data obtained with LVM fits best to the Langmuir isotherm model and exhibited a maximum adsorption capacity (qmax) of 333.3 mg g-1; the data followed the second-order equation. The intraparticle diffusion studies revealed that the adsorption rates were not controlled only by the diffusion step. The thermodynamic parameters, such as the changes in enthalpy, entropy, and Gibbs free energy, showed that the adsorption is endothermic, random and spontaneous at high temperature. The results indicate that LVM adsorbs MO efficiently and could be utilized as a low-cost alternative adsorbent for the removal of anionic dyes in wastewater treatment.

  15. The surface modification of stainless steel and the correlation between the surface properties and protein adsorption.

    Kang, Chan-Koo; Lee, Yoon-Sik

    2007-07-01

    Protein adsorption on a biomaterial surface is of great importance as it usually induces unfavorable biological cascades, with the result that much surface modification research has had to be performed in an effort to prevent this. In this study, we developed surface modification methods for stainless steel, which is a representative metal for biomedical device. The stainless steels were first smoothened to different extents by electropolishing, in order to obtain a rough or smooth surface. On these two kinds of substrates, we introduced epoxide groups to the metal surface by silanization with 3-glycidoxypropyltrimethoxysilane (GPTS). Then, various polymers such as poly(ethylene glycol) (PEG), poly(tetrahydrofuran glycol) (PTG), poly(propylene glycol) (PPG) and poly(dimethylsiloxane) (PDMS) were grafted on the silanized stainless steels. Each surface modification step was confirmed by various analytical methods. Contact angle measurement revealed that the surface hydrophilicity was controllable by polymer grafting. Root-mean-square (RMS) data of atomic force microscopy showed that surface roughness was dramatically changed by electropolishing. Based on these results, the correlation between surface properties and protein adsorption was investigated. In the protein adsorption study, we observed that all of the polymer-grafted stainless steels exhibited lower protein adsorption, when compared with bare stainless steel. Moreover, a hydrophilic and smooth surface was found to be the best of choice for decreasing the protein adsorption. PMID:17277988

  16. Effect of temperature and kinetic modelling of lignosulfonate adsorption onto powdered eggshell in batch systems

    Muhammad Ali Zulfikar

    2013-06-01

    Full Text Available The sorption of lignosulfonate onto powdered eggshell under the influence of temperature has been studied. The rate of adsorption onto eggshell was investigated under a variety of adsorbent dosages. The kinetic data from these investigations were correlated to a number of adsorption models in an attempt to elucidate the mechanism of the adsorption processes. Thermodynamic parameter data indicated that the lignosulfonate sorption process was non-spontaneous and endothermic under the experimental conditions, with the Gibbs free energy (Go in the range of 1.83-1.07 kJ mol-1, enthalpy (Ho andentropy (So of 5.66 kJ mol-1 and 12.82 J mol-1, respectively and the activation energy of 18.17 kJ mol-1. The adsorption mechanism was found to follow a pseudo-second-order model, with the kinetic constants in the range of 0.689–1.430 g mg-1 min-1. Both the intra-particle diffusion and Boyd kinetic models indicated that boundary layer/film diffusion was the main rate determining step in lignosulfonate adsorption process.

  17. Removal and recovery of hazardous triphenylmethane dye, Methyl Violet through adsorption over granulated waste materials

    Bottom Ash a power plant waste material and De-Oiled Soya, an agricultural waste product have been successfully used for the removal and recovery of a hazardous triphenylmethane dye-Methyl Violet, from wastewaters. The characterization of each adsorbent has been carried out by I.R. and D.T.A. curves. Batch adsorption studies have been made by measuring effects of pH, sieve size, amount of adsorbent, contact time, temperature, concentration of the adsorbate solution, etc. Kinetic studies have been used to determine the nature of rate controlling step of the processes and confirm the applicability of the first order rate expression in the ongoing adsorption process. Various thermodynamic parameters have also been calculated by applying the linear forms of Langmuir and Freundlich adsorption isotherms. The linear nature of adsorption isotherms obtained shows the dependence of the processes on the Freundlich and Langmuir isotherm models. Furthermore, to ascertain the adsorption processes to be particle diffusion or film diffusion mechanism, Boyd and Reichenberg's expressions have been applied. For both the adsorbents, column operations have been carried out for the bulk removal of the dye. The adsorbed dye has been recovered by eluting hydrochloric acid of pH 3 through exhausted columns

  18. Simulation studies of the dissociation of H 2 on stepped surfaces

    Kaukonen, H.-P.; Nieminen, R. M.

    1991-05-01

    We have simulated the dissociation reaction of H 2 on stepped ideal honeycomb, square and hexagonal surfaces with a simple kinetic model based on the idea proposed by Poelsema and Comsa [Scattering of Thermal Energy Atoms from Disordered Surfaces, Springer Tracts in Modern Physics 115 (Springer, Berlin, 1989)] that dissociation on a stepped Pt(111) surface occurs exclusively on step sites. The observed sticking coefficient sH 2 of H 2 consists of two competing channels: (1) physisorbed molecules incident on terrace sites diffusing to the step, and (2) direct dissociation of molecules incident on or near a step site. The results support this picture qualitatively and indicate that the behaviour of the system can be separated depending on surface temperature into three domains in each of which a different mechanism dominates. (1) T T2: direct adsorption near a step site. Of the three surfaces structures studied the honeycomb structure corresponds most closely to the observed H 2 dissociation.

  19. Adsorption of Cadmium By Silica Chitosan

    Moftah Ali; Ani Mulyasuryani; Akhmad Sabarudin

    2013-01-01

    The adsorption process depends on initial concentration of Cd2+ and ratio of  chitosan in adsorbent. The present study deals with the competitive adsorption of Cd2+ ion onto silica graft with chitosan. Batch adsorption experiments were performed at five different initial Cd2+ concentrations (5, 10, 15, 20 and 25 ppm), on five different proportion from silica to chitosan (100%, 95%, 85%, 75% and 65%) as adsorbent at pH 5. In the recovery process, the high recovery at 0.5 mg and observed the re...

  20. Adsorption of gases on heterogeneous surfaces

    Rudzinski, W

    1991-01-01

    All real solid surfaces are heterogeneous to a greater or lesser extent and this book provides a broad yet detailed survey of the present state of gas adsorption. Coverage is comprehensive and extends from basic principles to computer simulation of adsorption. Underlying concepts are clarified and the strengths and weaknesses of the various methods described are discussed.Key Features* Adsorption isotherm equations for various types of heterogeneous solid surfaces* Methods of determining the nature of surface heterogeneity and porosity from experimental data* Studies of pha

  1. ADSORPTION RATE CONSTANTS OF EOSIN IN HUMIN

    Anshar, Andi Muhammad

    2015-01-01

    Eosin is one of the dyes commonly used in the industry and has the potential to cause pollution of the water environment. The Eosin pollution treatment methods used in this study was the adsorption method using humin fraction obtained from the peat land comes from Kalimantan. From the research data showed that the adsorption of eosin in humin result of washing with HCl / HF optimum at pH 4 and a contact time of 60 minutes with the adsorption-order rate was 8,4 x 10-3 min-1

  2. Preface, Soil Science: A step-by-step analysis

    This book provides step-by-step procedures for soil professionals, without a lot of background theory. Chapters are targeted toward agricultural and environmental consultants, producers, students, teachers, government, and industry. Applied soil scientists gave input through a survey, which guided t...

  3. HTML5 in easy steps

    McGrath, Mike

    2011-01-01

    Without doubt HTML5 is the future of the web and HTML5 in easy steps demonstrates all you can achieve NOW in the latest browsers - all described in easy to follow steps. HTML5 in easy steps instructs you how to employ the latest development for web page design with HyperText Markup Language (HTML5). Modern web browsers have united to support exciting new features of the HTML5 standard that allows easy creation of stunning web pages and engaging interactive applications. HTML5 in easy steps contains examples and screenshots that illustrate each feature of HTML5, describing how to incorporate me

  4. Application of ultrasonic backscattering for level measurement and process monitoring of expanded-bed adsorption columns.

    Thelen, T V; Mairal, A P; Thorsen, C S; Ramirez, W F

    1997-01-01

    Expanded-bed adsorption is a newly commercialized technique for the purification of proteins from cellular debris in downstream processing. An expanded bed presents the possibility of protein recovery in a single step, eliminating the often costly clarification processing steps such as ultrafiltration, centrifugation, and precipitation. A major obstacle to the successful commercialization of this technology is the inability to accurately monitor and control the bed height in these systems. Fluctuations in the feedstock viscosity are common during normal operation and tend to make the operation and control of expanded beds for biological applications complex and difficult. We develop a level measurement technique based upon ultrasonics. It is shown that this technique has great promise for bed-height measurement in expanded-bed adsorption systems. Furthermore, the bed-height measurement can be used in feedback control strategies for bed-height regulation. The proposed ultrasonic sensor is also capable of monitoring for plugging and bubbling in the column. PMID:9336988

  5. Analysis of Modified Starch Adsorption Kinetics on Cellulose Fibers via the Modified Langmuir Adsorption Theory

    Zakrajšek, N.; Knez, S.; Ravnjak, D.; Golob, J.

    2009-01-01

    The kinetics of starch adsorption on cellulose fibers is one of the most important criteria regarding the efficient application of papermaking additives due to the continuous nature of paper production and the concomitant need to determine optimum residence times. This study presents an analysis of the kinetics of modified starch adsorption onto cellulose fibers via the application of the modified Langmuir adsorption theory (i.e. the collision theory). A model based on this theory was used to...

  6. Molecular Simulation of Hydrogen Adsorption Density in Single-Walled Carbon Nanotubes and Multilayer Adsorption Mechanism

    Lianquan GUO; Changxiang MA; Shuai WANG; He MA; Xin LI

    2005-01-01

    The adsorption of hydrogen onto single-walled carbon nanotubes (SWCNTs) was studied by molecular dynamics (MD)sim.lation. It was found that the hydrogen molecules distribute regularly inside and outside of the tube. Density distribution was computed for H2 molecule. Theoretical analysis of the result showed the multilayer adsorption mechanism of SWCNTs. The storage of H2 in SWCNTs is computed, which provides essential theoretical reference for further study of hydrogen adsorption in SWCNTs.

  7. Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test

    Nam, Sangchul; Namkoong, Wan [Department of Environmental Engineering, Konkuk University, Hwayang-Dong, Gwangjin-Gu, Seoul 143-701 (Korea, Republic of); Kang, Jeong-Hee; Park, Jin-Kyu [Department of Environmental Engineering, Anyang University, Anyang 5-Dong, Manan-Gu, Anyang-Si, Gyeonggi-Do 430-714 (Korea, Republic of); Lee, Namhoon, E-mail: nhlee@anyang.ac.kr [Department of Environmental Engineering, Anyang University, Anyang 5-Dong, Manan-Gu, Anyang-Si, Gyeonggi-Do 430-714 (Korea, Republic of)

    2013-10-15

    Highlights: • Equilibrium test was attempted to evaluate adsorption characteristics of siloxane. • L2 had higher removal efficiency in carbon compared to noncarbon adsorbents. • Total adsorption capacity of siloxane was 300 mg/g by coal activated carbon. • Adsorption characteristics rely on size of siloxane molecule and adsorbent pore. • Conversion of siloxane was caused by adsorption of noncarbon adsorbents. - Abstract: Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane.

  8. Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test

    Highlights: • Equilibrium test was attempted to evaluate adsorption characteristics of siloxane. • L2 had higher removal efficiency in carbon compared to noncarbon adsorbents. • Total adsorption capacity of siloxane was 300 mg/g by coal activated carbon. • Adsorption characteristics rely on size of siloxane molecule and adsorbent pore. • Conversion of siloxane was caused by adsorption of noncarbon adsorbents. - Abstract: Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane

  9. The cost-effective synthesis of furan- and thienyl-based microporous polyaminals for adsorption of gases and organic vapors.

    Li, Guiyang; Zhang, Biao; Yan, Jun; Wang, Zhonggang

    2016-01-21

    This work reveals that furfural and 2-thenaldehyde can readily react with melamine via "one-step" polycondensation to yield hyper-cross-linked sulfur-, nitrogen- and oxygen-rich microporous polyaminals with promising applications in adsorption of gases and toxic organic vapors. PMID:26611445

  10. Adsorption Isotherms and Surface Reaction Kinetics

    Lobo, L. S.; Bernardo, C. A.

    1974-01-01

    Explains an error that occurs in calculating the conditions for a maximum value of a rate expression for a bimolecular reaction. The rate expression is derived using the Langmuir adsorption isotherm to relate gas pressures and corresponding surface coverages. (GS)

  11. Adsorption of molecular hydrogen on nanostructered surfaces

    Were investigated the effect of the structural characteristics of model nanoporous environments on the adsorption of molecular hydrogen. The adsorption properties of the target nanostructures (graphene and ZnO sheets, carbon foams, metal-organic frameworks) are evaluated in a broad range of thermodynamic conditions. The study is carried out within the density functional theory for quantum fluids at finite temperature (QLDFT), which allows to account for the many-body and quantum delocalization effects in a single theoretical framework. The exchange-correlation (excess) functional is derived from the empirical equation of state of the homogeneous system. We focus on the evaluation of hydrogen storage capacities of the substrates and on the emergence of quantum effects triggered by the confinement imposed by the host structure. The approach provides accurate estimates of the hydrogen storage capacities for realistic adsorptive media. The relation between the microscopic structure of the hydrogen fluid and the calculated adsorption properties is also addressed. (full text)

  12. Mechanism of adsorption of cations onto rocks

    Adsorption behavior of cations onto granite was investigated. The distribution coefficient (Kd) of Sr2+ and Ba2+ onto granite was determined in the solution of which pH was ranged from 3.5 to 11.3 and ionic strength was set at 10-2 and 10-1. The Kd values were found to increase with increasing pH and with deceasing ionic strength. The obtained data were successfully analyzed by applying an electrical double layer model. The optimum parameter values of the double layer electrostatics and adsorption reactions were obtained, and the mechanism of adsorption of cations onto granite was discussed. Feldspar was found to play an important role in their adsorption. (author)

  13. Adsorption of plant phenols by polystyrene resins

    Akiyoshi Fukushima

    2014-02-01

    Full Text Available Adsorption of nine plant phenols by nine polystyrene ion-exchange resins was investigated in an experimental model system. The phenols were adsorbed by Amberlite CG-120 more efficiently than any other acidically charged resins tested in this study. They were also taken up by anion exchangers. Among them Dowex 1-X8 was found to show the strongest effect on the adsorption of the phenolic constituents applied. A comparison of the efficiency of plant phenol adsorption between two different types of the synthetic polymers revealed that the basically charged polystyrenes had more prefarable affinities for phenols than cation exchangers. For example, the ratio of the efficiency between Amberlite CG-120 and Dowex 1-X8 was roughly calculated to be 3:7 under the present experimental conditions. The adsorption rate of the test phenols was raised mostly by increasing the amount of the resins added, if they were mixed with effective polymers in the incubation model system.

  14. Argon adsorption and the lunar atmosphere

    Bernatowicz, T. J.; Podosek, F. A.

    1991-01-01

    The results of Ar adsorption experiments on a terrestrial labradorite and lunar rock 15415 crushed in vacuo are reported. The experiments were designed to test lunar atmosphere simulation models for the behavior of Ar on the lunar surface, as determined from the Apollo 17 mass spectrometer results. These models (Hodges, 1980, 1982) used a single adsorption potential to characterize the surfaces of lunar soil grains, with the result that high (6-7 kcal/mol) heats of adsorption were inferred. The present experimental results show that very high adsorption potentials are indeed associated with fresh mineral surfaces, but that these energetic surfaces occupy only small fractions of the total surface area. Nonetheless, these small fractions of surface, if they can be maintained in the lunar regolith in steady-state condition, could be sufficient to account for the Apollo 17 mass spectrometer observations.

  15. Selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation.

    Miao, Guang; Ye, Feiyan; Wu, Luoming; Ren, Xiaoling; Xiao, Jing; Li, Zhong; Wang, Haihui

    2015-12-30

    This study investigates selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation. The TiO2/SiO2 adsorbents were prepared and then characterized by N2 adsorption, X-ray diffraction and X-ray photoelectron spectroscopy. Adsorption isotherms, selectivity and kinetics of TiO2/SiO2 were measured in a UV built-in batch reactor. It was concluded that (a) with the employment of UV-irradiation, high organosulfur uptake of 5.12 mg/g was achieved on the optimized 0.3TiO2/0.7SiO2 adsorbent at low sulfur concentration of 15 ppmw-S, and its adsorption selectivity over naphthalene was up to 325.5; (b) highly dispersed TiO2 served as the photocatalytic sites for DBT oxidation, while SiO2 acted as the selective adsorption sites for the corresponding oxidized DBT using TiO2 as a promoter, the two types of active sites worked cooperatively to achieve the high adsorption selectivity of TiO2/SiO2; (c) The kinetic rate-determining step for the UV photocatalysis-assisted adsorptive desulfurization (PADS) over TiO2/SiO2 was DBT oxidation; (d) consecutive adsorption-regeneration cycles suggested that the 0.3TiO2/0.7SiO2 adsorbent can be regenerated by acetonitrile washing followed with oxidative air treatment. This work demonstrated an effective PADS approach to greatly enhance adsorption capacity and selectivity of thiophenic compounds at low concentrations for deep desulfurization under ambient conditions. PMID:26223016

  16. Impacts of coagulation on the adsorption of organic micropollutants onto powdered activated carbon in treated domestic wastewater.

    Altmann, Johannes; Zietzschmann, Frederik; Geiling, Eva-Linde; Ruhl, Aki Sebastian; Sperlich, Alexander; Jekel, Martin

    2015-04-01

    The application of powdered activated carbon (PAC) as an advanced wastewater treatment step for the removal of organic micropollutants (OMP) necessitates complete separation of the PAC particles, e.g. by coagulation. In this study, potential positive or negative indirect or direct effects of coagulation on the adsorption of OMPs onto PAC in treated wastewater were investigated. Although the concentration of dissolved organic matter (DOM) was significantly reduced by coagulation, the selective removal of mainly larger DOM components such as biopolymers and humic substances did not improve subsequent OMP adsorption onto PAC, demonstrating that coagulation has minor effects on DOM constituents that are relevant for direct competition or pore blocking. The combination of coagulation and adsorption yielded the sum of the individual removals, as adsorption predominantly affected smaller compounds. While the formation of flocs led to visible incorporation of PAC particles, no significant mass transfer limitations impeded the OMP adsorption. As a result, the dosing sequence of coagulant and PAC is not critical for efficient adsorption of OMPs onto PAC. The relationships between adsorptive OMP removal and corresponding reduction of UV absorption at 254 nm (UVA254) as a promising surrogate correlation for the real-time monitoring and PAC adjustment were affected by coagulation, leading to individual correlations depending on the water composition. Correcting for UVA254 reduction by coagulation produces adsorptive UVA254 removal, which correlates highly with OMP removal for different WWTP effluents and varying coagulant doses and can be applied in combined adsorption/coagulation processes to predict OMP removal and control PAC dosing. PMID:25582393

  17. Adsorption performances and refrigeration application of adsorption working pair of CaCl2-NH3

    WANG; Liwei; WANG; Ruzhu; WU; Jingyi; WANG; Kai

    2004-01-01

    The adsorption performance of CaCl2-NH3 is studied under the condition of different expansion spaces for adsorbent, andthe relationships between adsorption performance of CaCl2-NH3 and the phenomena of swelling and agglomeration during adsorption are researched. It is found that the performance stability is related to the ratio of expansion space to the volume of adsorbent ras, and the performance attenuation is serious in the case of large ras. Severe adsorption hysteresis exists in the process of adsorption and desorption at the same evaporating and condensing temperatures, which is related to the stability constant of chemical reaction. This phenomenon cannot be explained by the theory of physical adsorption. Moderate agglomeration will be beneficial to the formation of ammoniate complex; the magnitude of expansion space will affect adsorption performance. Analysis shows that the activated energy needed in the process of adsorption for the sample with ras of 2:1 is less than that for the sample with ras of 3:1.The refrigeration performance of CaCl2-NH3 is predicted from experiments. The cooling capacity of one adsorption cycle is about 945.4 kJ/kg for the adsorbent with an ras of 2:1 at the evaporating temperature of 0℃.

  18. PREPARATION OF ACTIVATED CARBON FIBER AND THEIR XENON ADSORPTION PROPERTIES (Ⅱ)-XENON ADSORPTION PROPERTIES

    2002-01-01

    The adsorption of xenon from air has an interest in the monitoring of nuclear explosion oraccident, or in the treatment of nuclear waste gas. In this paper, the pore structure of several series ofactivated carbon fibers has been characterized. The adsorption properties of xenon on theseactivated carbon fibers under different temperatures have been studied in details. The results showthat the xenon adsorption amount on activated carbon fibers do not increase with specific surfacearea of adsorbents, but are closely related to their pore size distribution. Pores whose radius equal toor narrow than 0.4nm would be more advantageous to the adsorption of xenon.

  19. Selective adsorption of tannins onto hide collagen fibres

    廖学品; 陆忠兵; 石碧

    2003-01-01

    Hide collagen of animals is used to prepare adsorbent material and its adsorption properties to tannins are investigated. It is indicated that the collagen fibres has excellent adsorption selectivity and high adsorption capacity to tannins. The adsorption rate of tannins is more than 90% whilst less than 10% of functional components are retained by the adsorbent. The adsorption mechanism of tannins onto hide collagen fibres is hydrogen-bonding association. Freundlich model can be used to describe the adsorption isotherms, and the pseudo-second-order rate model can be used to describe adsorption kinetics.

  20. ADSORPTION OF LDL ON THE MODIFIED CHITOSAN

    LIUManying; ZHAOLirui; 等

    2000-01-01

    In this paper,the selective adsorption of LDL on chitosan modified with PEG and Asp.was studied.The adsorption rate of LDL and HDL on the double modified chitosan was 57% and 12% respoectively,The results shown that the double modified chitosan can be used a adsorbent for selective binding to LDL,this work may help to develop functional columns for hemoperfusion.

  1. Adsorption Kinetic of 8-Hydroxyquinoline on Malachite

    Gabriela OPREA

    2007-01-01

    Full Text Available Influence of temperature and collector concentration on its adsorption rate on mineral surface was studied as regarding to the 8-hydroxyquinoline/malachite system. Theoretical equations as well as experimental data may be useful to estimate the adsorption rate and kinetics connected to the conditioning stage in mineral flotation in order to optimise the selectivity and the recovery of the desired mineral.

  2. Defluoridation of drinking water using adsorption processes

    Highlights: ► Comprehensive and critical literature review on various adsorbents used for defluoridation. ► pH, temperature, kinetics and co-existing anions effects on F adsorption. ► Choice of adsorbents for various circumstances. ► Adsorption thermodynamics and mechanisms. ► Future research on efficient, low cost adsorbents which are easily regenerated. -- Abstract: Excessive intake of fluoride (F), mainly through drinking water, is a serious health hazard affecting humans worldwide. There are several methods used for the defluoridation of drinking water, of which adsorption processes are generally considered attractive because of their effectiveness, convenience, ease of operation, simplicity of design, and for economic and environmental reasons. In this paper, we present a comprehensive and a critical literature review on various adsorbents used for defluoridation, their relative effectiveness, mechanisms and thermodynamics of adsorption, and suggestions are made on choice of adsorbents for various circumstances. Effects of pH, temperature, kinetics and co-existing anions on F adsorption are also reviewed. Because the adsorption is very weak in extremely low or high pHs, depending on the adsorbent, acids or alkalis are used to desorb F and regenerate the adsorbents. However, adsorption capacity generally decreases with repeated use of the regenerated adsorbent. Future research needs to explore highly efficient, low cost adsorbents that can be easily regenerated for reuse over several cycles of operations without significant loss of adsorptive capacity and which have good hydraulic conductivity to prevent filter clogging during the fixed-bed treatment process

  3. Adsorption of fucoidan and chitosan sulfate on chitosan modified PET films monitored by QCM-D

    Indest, Tea; Laine, Janne; Johansson, Leena Sisko; Stana-Kleinschek, Karin; Strnad, Simona; Dworczak, Renate; Ribitsch, Volker

    2012-01-01

    The adsorption behavior of fucoidan as well as chitosan derivatives (chitosan sulfate) on poly(ethylene terephthalate) (PET) model film surface was studied using the quartz crystal microbalance technique. These systems were chosen for this study due to their promising biocompatible properties. Moreover, fucoidan and chitosan sulfate have promising anticoagulant properties and represent an alternative to heparin treatment of vascular grafts. As a first step, PET foils were activated by alkalin...

  4. Understanding the Optimal Adsorption Energies for Catalyst Screening in Heterogeneous Catalysis

    Yang, Bo; Burch, Robbie; Hardacre, Christopher; Headdock, Gareth; Hu, P

    2014-01-01

    The fundamental understanding of the activity in heterogeneous catalysis has long been the major subject in chemistry. This paper shows the development of a two-step model to understand this activity. Using the theory of chemical potential kinetics with Bronsted-Evans-Polanyi relations, the general adsorption energy window is determined from volcano curves, using which the best catalysts can be searched. Significant insights into the reasons for catalytic activity are obtained.

  5. Kinetic studies of zinc ions removal from aqueous solution by adsorption on natural zeolite

    Zendelska, Afrodita; Golomeova, Mirjana; Blažev, Krsto; Krstev, Boris; Golomeov, Blagoj; Krstev, Aleksandar

    2014-01-01

    The kinetics of zinc adsorption onto natural zeolite (clinoptilolite) were studied with respect to initial metal ion concentration, adsorbent mass and initial pH value. In order to select the main rate-determining step in the overall uptake mechanism, a series of experiments were performed under batch conditions from single ion solutions. Data obtained from the kinetic experiments are interpreted in terms of Pseudo-second order kinetic model, Weber and Morris model and mod...

  6. Adsorption properties of nitrobenzene in wastewater with silica aerogels

    2010-01-01

    The adsorption properties of nitrobenzene from wastewater by hydrophobic silica aerogels were investigated.The effects of adsorption intensity by pH value,adsorption temperature,adsorption time and the amount of the silica aerogels were studied.The adsorption principle and mechanism of silica aerogels adsorbing nitrobenzene were discussed along with the Freundlich equation.The results showed that the adsorption intensity of the hydrophobic silica aerogels could reach 68.76% at better adsorption conditions of adsorption temperature 25°C,pH value 8.35,the amount of SiO2 aerogels dosage 3.33 g/L,and adsorption time of 30 min,and that the adsorption properties were related to the hydrophobility of aerogels,surface area of organic solution,structure of aerogels.

  7. Graphene oxide and adsorption of chloroform: a density functional study

    Kuisma, Elena; Lindberg, Th Benjamin; Gillberg, Christoffer A; Idh, Sebastian; Schroder, Elsebeth

    2016-01-01

    Chlorinated hydrocarbon compounds are of environmental concerns, since they are toxic to humans and other mammals, are widespread, and exposure is hard to avoid. Understanding and improving methods to reduce the amount of the substances is important. We present an atomic-scale calculational study of the adsorption of chlorine-based substance chloroform (CHCl3) on graphene oxide, as a step in estimating the capacity of graphene oxide for filtering out such substances, e.g., from drinking water. The calculations are based on density functional theory (DFT), and the recently developed consistent-exchange functional for the van der Waals density-functional method (vdW-DF-cx) is employed. We obtain values of the chloroform adsorption energy varying from roughly 0.2 to 0.4 eV per molecule. This is comparable to previously found results for chloroform adsorbed directly on clean graphene, using similar calculations. In a wet environment, like filters for drinking water, the graphene will not stay clean and will likel...

  8. Nitrate Adsorption on Clay Kaolin: Batch Tests

    Morteza Mohsenipour

    2015-01-01

    Full Text Available Soils possessing kaolin, gibbsite, goethite, and hematite particles have been found to have a natural capacity to attenuate pollution in aqueous phase. On the other hand, the hydroxyl group in soil increases anion exchange capacity under a low pH condition. The main objective of this paper was to evaluate effects of kaolin on nitrate reduction under acidic condition. In order to analyze the kaolin adsorption behaviour under various conditions, four different concentrations of nitrate, 45, 112.5, 225, and 450 mgNO3-/L, with a constant pH equal to 2, constant temperature equal to 25°C, and exposure period varying from 0 to 150 minutes were considered. The capacity of nitrate adsorption on kaolin has also been studied involving two well-known adsorption isotherm models, namely, Freundlich and Longmuir. The results revealed that approximately 25% of the nitrate present in the solution was adsorbed on clay kaolin. The laboratory experimental data revealed that Freundlich adsorption isotherm model was more accurate than Longmuir adsorption model in predicting of nitrate adsorption. Furthermore, the retardation factor of nitrate pollution in saturated zone has been found to be approximately 4 in presence of kaolin, which indicated that kaolin can be used for natural scavenger of pollution in the environment.

  9. Modeling of Experimental Adsorption Isotherm Data

    Xunjun Chen

    2015-01-01

    Full Text Available Adsorption is considered to be one of the most effective technologies widely used in global environmental protection areas. Modeling of experimental adsorption isotherm data is an essential way for predicting the mechanisms of adsorption, which will lead to an improvement in the area of adsorption science. In this paper, we employed three isotherm models, namely: Langmuir, Freundlich, and Dubinin-Radushkevich to correlate four sets of experimental adsorption isotherm data, which were obtained by batch tests in lab. The linearized and non-linearized isotherm models were compared and discussed. In order to determine the best fit isotherm model, the correlation coefficient (r2 and standard errors (S.E. for each parameter were used to evaluate the data. The modeling results showed that non-linear Langmuir model could fit the data better than others, with relatively higher r2 values and smaller S.E. The linear Langmuir model had the highest value of r2, however, the maximum adsorption capacities estimated from linear Langmuir model were deviated from the experimental data.

  10. Adsorption of xenon and krypton on shales

    Parameters for the adsorption of Xe and Kr on shales and related samples have been measured by a method that uses a mass spectrometer as a manometer. The gas partial pressures used were 10-11 atm or less; the corresponding adsorption coverages are only small fractions of a monolayer, and Henry's Law behavior is expected and observed. Heats of adsorption in the range 2 to 7 kcal/mol were observed. Henry constants of the order of magnitude 1 cm3 STP g-1 atm-1 at 0 to 250C are obtained by extrapolation. Adsorption properties are variable by sample, but the general range suggests that shales might be sufficiently good adsorbents that equilibrium adsorption with modern air may account for a nontrivial fraction of the atmospheric inventory of Xe (perhaps even Kr). It seems doubtful, however, that this effect can account for the deficiency of atmospheric Xe in comparison with the planetary gas patterns observed in meteorites. If gas is adsorbed on interior surfaces in shale clays and can communicate with sample exteriors only through very narrow channels, and thus only very slowly, equilibrium adsorption may make substantial contributions to experimentally observed 'trapped' gases without the need for any further trapping mechanism. (author)

  11. Adsorption dynamics of gases and vapors on the nanoporous metal organic framework material Ni2(4,4'-bipyridine)3(NO3)4: guest modification of host sorption behavior.

    Fletcher, A J; Cussen, E J; Prior, T J; Rosseinsky, M J; Kepert, C J; Thomas, K M

    2001-10-17

    This study combines measurements of the thermodynamics and kinetics of guest sorption with powder X-ray diffraction measurements of the nanoporous metal organic framework adsorbent (host) at different adsorptive (guest) loadings. The adsorption characteristics of nitrogen, argon, carbon dioxide, nitrous oxide and ethanol and methanol vapors on Ni2(4,4'-bipyridine)3(NO3)4 were studied over a range of temperatures as a function of pressure. Isotherm steps were observed for both carbon dioxide and nitrous oxide adsorption at approximately 10-20% of the total pore volume and at approximately 70% of total pore volume for methanol adsorption. The adsorption kinetics obey a linear driving force (LDF) mass transfer model for adsorption at low surface coverage. At high surface coverage, both methanol and ethanol adsorption follow a combined barrier resistance/diffusion model. The rates of adsorption in the region of both the carbon dioxide and methanol isotherm steps were significantly slower than those observed either before or after the step. X-ray diffraction studies at various methanol loadings showed that the host structure disordered initially but underwent a structural change in the region of the isotherm step. These isotherm steps are ascribed to discrete structural changes in the host adsorbent that are induced by adsorption on different sites. Isotherm steps were not observed for ethanol adsorption, which followed a Langmuir isotherm. Previous X-ray crystallography studies have shown that all the sites are equivalent for ethanol adsorption on Ni2(4,4'-bipyridine)3(NO3)4, with the host structure undergoing a scissoring motion and the space group remaining unchanged during adsorption. The activation energies and preexponential factors for methanol and ethanol adsorption were calculated for each pressure increment at which the linear driving force model was obeyed. There was a good correlation between activation energy and ln(preexponential factor), indicating a

  12. Separation of galactoglucomannans, lignin, and lignin-carbohydrate complexes from hot-water-extracted Norway spruce by cross-flow filtration and adsorption chromatography

    Niklas Westerberg; Hampus Sunner; Mikaela Helander; Gunnar Henriksson; Martin Lawoko; Anders Rasmuson

    2012-01-01

    A simple method to simultaneously recover polymeric carbohydrates, mainly galactoglucomannans (GGM), lignin, and lignin-carbohydrate complex (LCC) from hot-water-extracted Norway spruce wood is presented. The isolation method consists of cross-flow filtration, where high and low molecular mass species are removed, followed by fixed-bed adsorption on a hydrophobic polymeric resin (XAD-16) to remove lignins and lignans. In the second step of fixed-bed adsorption, a phenylic reversed-phase analy...

  13. Adsorption of Cr (III) from aqueous solution by groundnut shell

    Tasrina Rabia Choudhury; Mustafa, A. I.

    2012-01-01

    Adsorption and de-sorption of chromium (III) ions on groundnut shell from aqueous solutions have been studied using batch adsorption techniques with respect to the influence of contact time, pH, adsorbent dose, initial chromium concentration and particle size. Appropriate adsorption isotherm and kinetic parameters of chromium (III) adsorption on groundnut shell have also been determined. The results of this study showed that adsorption of chromium (III) by groundnut shell reached to equilibr...

  14. Adsorption of mercury ions by mercapto-functionalized amorphous silica

    Perez-Quintanilla, Damian; Hierro, Isabel del; Fajardo, Mariano; Sierra, Isabel [Universidad Rey Juan Carlos, Departamento de Tecnologia Quimica y Ambiental, E.S.C.E.T, Mostoles, Madrid (Spain); Carrillo-Hermosilla, Fernando [Universidad de Castilla-La Mancha, Departamento de Quimica Inorganica, Organica y Bioquimica, Facultad de Quimicas, Ciudad Real (Spain)

    2006-02-01

    Amorphous silicas have been functionalized by two different methods. In the heterogeneous route the silylating agent, 3-chloropropyltriethoxysilane, was initially immobilized onto the silica surface to give the chlorinated silica Cl-Sil. In a second reaction, multifunctionalized N,S donor compounds were incorporated to obtain the functionalized silicas, which are denoted as L-Sil-Het (where L=mercaptothiazoline, mercaptopyridine or mercaptobenzothiazole). In the homogeneous route, the functionalization was achieved through a one-step reaction between the silica and an organic ligand containing the chelating functions; this gave the modified silicas denoted as L-Sil-Hom. The functionalized silicas were characterized by elemental analysis, IR spectroscopy and thermogravimetry. These materials were employed as adsorbents for mercury cations from aqueous and acetone solutions at room temperature. The results indicate that, in all cases, mercury adsorption was higher in the modified silicas prepared by the homogeneous method. (orig.)

  15. Fluoride and lead adsorption on carbon nanotubes

    WANG Shuguang; LI Yanhui

    2004-01-01

    The properties and applications of CNT have been studied extensively since Iijima discovered them in 1991[1,2]. They have exceptional mechanical properties and unique electrical property, highly chemical stability and large specific surface area. Thus far, they have widely potential applications in many fields. They can be used as reinforcing materials in composites[3], field emissions[4], hydrogen storage[5], nanoelectronic components[6], catalyst supports[7], adsorption material and so on. However, the study on the potential application of CNT, environmental protection field in particular, was hardly begun.Long[8] et al. reported that CNT had a significantly higher dioxin removal efficiency than that of activated carbon. The Langmuir adsorption constant is 2.7 × 1052, 1.3 × 1018 respectively. The results indicated that CNT is potential candidate for the removal of micro-organic pollutants. However, the reports on the CNT used as fluoride and heavy metal adsorbent are seldom.In this paper, A novel material, alumina supported on carbon nanotubes (Al2O3/CNT), was prepared from carbon nanotubes and Al(NO3)3. X-ray diffraction (XRD) spectra demonstrate that alumina is amorphous, and scanning electron microscope (SEM) images show that CNT and alumina are homogeneously mixed. Furthermore, the fluoride adsorption behavior on the surface of Al2O3/CNT has been investigated and compared with other adsorbents. The results indicate that Al2O3/CNT has a high adsorption capacity, with a saturation adsorption capacity of 39.4 mg/g. It is also found that the adsorption capacity of Al2O3/CNT is 3.0~4.5 times that of γ-Al2O3while almost equal to that of IRA-410 polymeric resin at 25 ℃. The adsorption isotherms of fluoride on Al2O3/CNT is fit the Freundlich equation well, optimal pH ranging from 5.0 to 9.0.Also in this paper, a novel material, modified carbon nanotubes (CNT), was prepared from carbon nanotubes and HNO3 under boiling condition. Infrared spectroscopy (IR

  16. New Adsorption Cycles for Carbon Dioxide Capture and Concentration

    James Ritter; Armin Ebner; Steven Reynolds Hai Du; Amal Mehrotra

    2008-07-31

    The objective of this three-year project was to study new pressure swing adsorption (PSA) cycles for CO{sub 2} capture and concentration at high temperature. The heavy reflux (HR) PSA concept and the use of a hydrotalcite like (HTlc) adsorbent that captures CO{sub 2} reversibly at high temperatures simply by changing the pressure were two key features of these new PSA cycles. Through the completion or initiation of nine tasks, a bench-scale experimental and theoretical program has been carried out to complement and extend the process simulation study that was carried out during Phase I (DE-FG26-03NT41799). This final report covers the entire project from August 1, 2005 to July 31, 2008. This program included the study of PSA cycles for CO{sub 2} capture by both rigorous numerical simulation and equilibrium theory analysis. The insight gained from these studies was invaluable toward the applicability of PSA for CO{sub 2} capture, whether done at ambient or high temperature. The rigorous numerical simulation studies showed that it is indeed possible to capture and concentrate CO{sub 2} by PSA. Over a wide range of conditions it was possible to achieve greater than 90% CO{sub 2} purity and/or greater than 90% CO{sub 2} recovery, depending on the particular heavy reflux (HR) PSA cycle under consideration. Three HR PSA cycles were identified as viable candidates for further study experimentally. The equilibrium theory analysis, which represents the upper thermodynamic limit of the performance of PSA process, further validated the use of certain HR PSA cycles for CO{sub 2} capture and concentration. A new graphical approach for complex PSA cycle scheduling was also developed during the course of this program. This new methodology involves a priori specifying the cycle steps, their sequence, and the number of beds, and then following a systematic procedure that requires filling in a 2-D grid based on a few simple rules, some heuristics and some experience. It has been

  17. Two-step electroweak baryogenesis

    Inoue, Satoru; Ovanesyan, Grigory; Ramsey-Musolf, Michael J.

    2016-01-01

    We analyze electroweak baryogenesis during a two-step electroweak symmetry-breaking transition, wherein the baryon asymmetry is generated during the first step and preserved during the second. Focusing on the dynamics of C P violation required for asymmetry generation, we discuss general considerations for successful two-step baryogenesis. Using a concrete model realization, we illustrate in detail the viability of this scenario and the implications for present and future electric dipole moment (EDM) searches. We find that C P violation associated with a partially excluded sector may yield the observed baryon asymmetry while evading present and future EDM constraints.

  18. Two-Step Electroweak Baryogenesis

    Inoue, Satoru; Ramsey-Musolf, Michael J

    2016-01-01

    We analyze electroweak baryogenesis during a two-step electroweak symmetry breaking transition, wherein the baryon asymmetry is generated during the first step and preserved during the second. Focusing on the dynamics of CP-violation required for asymmetry generation, we discuss general considerations for successful two-step baryogenesis. Using a concrete model realization, we illustrate in detail the viability of this scenario and the implications for present and future electric dipole moment (EDM) searches. We find that CP-violation associated with a partially excluded sector may yield the observed baryon asymmetry while evading present and future EDM constraints.

  19. A review of the thermodynamics of protein association to ligands, protein adsorption, and adsorption isotherms

    Mollerup, Jørgen

    2008-01-01

    The application of thermodynamic models in the development of chromatographic separation processes is discussed. The paper analyses the thermodynamic principles of protein adsorption. It can be modeled either as a reversible association between the adsorbate and the ligands or as a steady...... adsorption is discussed. Hydrophobic and reversed phase chromatography are useful techniques for measuring solute activity coefficients at infinite dilution....

  20. Adsorption properties of a natural zeolite-water pair for use in adsorption cooling cycles

    Solmus, ismail; Yamali, Cemil; Baker, Derek; Caglar, Ahmet [Department of Mechanical Engineering, Middle East Technical University, 06531 Ankara (Turkey); Kaftanoglu, Bilgin [Department of Manufacturing Engineering, Atilim University, 06836 Ankara (Turkey)

    2010-06-15

    The equilibrium adsorption capacity of water on a natural zeolite has been experimentally determined at different zeolite temperatures and water vapor pressures for use in an adsorption cooling system. The Dubinin-Astakhov adsorption equilibrium model is fitted to experimental data with an acceptable error limit. Separate correlations are obtained for adsorption and desorption processes as well as a single correlation to model both processes. The isosteric heat of adsorption of water on zeolite has been calculated using the Clausius-Clapeyron equation as a function of adsorption capacity. The cyclic adsorption capacity swing for different condenser, evaporator and adsorbent temperatures is compared with that for the following adsorbent-refrigerant pairs: activated carbon-methanol; silica gel-water; and, zeolite 13X-water. Experimental results show that the maximum adsorption capacity of natural zeolite is nearly 0.12 kg{sub w}/kg{sub ad} for zeolite temperatures and water vapor pressures in the range 40-150 C and 0.87-7.38 kPa. (author)

  1. Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test.

    Nam, Sangchul; Namkoong, Wan; Kang, Jeong-Hee; Park, Jin-Kyu; Lee, Namhoon

    2013-10-01

    Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane. PMID:23684695

  2. Microcystin-LR Adsorption by Activated Carbon.

    Pendleton, Phillip; Schumann, Russell; Wong, Shiaw Hui

    2001-08-01

    We use a selection of wood-based and coconut-based activated carbons to investigate the factors controlling the removal of the hepatotoxin microcystin-LR (m-LR) from aqueous solutions. The wood carbons contain both micropores and mesopores. The coconut carbons contain micropores only. Confirming previously published observations, we also find that the wood-based carbons adsorb more microcystin than the coconut-based carbons. From a combination of a judicious modification of a wood-based carbon's surface chemistry and of the solution chemistry, we demonstrate that both surface and solution chemistry play minor roles in the adsorption process, with the adsorbent surface chemistry exhibiting less influence than the solution chemistry. Conformational changes at low solution pH probably contribute to the observed increase in adsorption by both classes of adsorbent. At the solution pH of 2.5, the coconut-based carbons exhibit a 400% increased affinity for m-LR compared with 100% increases for the wood-based carbons. In an analysis of the thermodynamics of adsorption, using multiple temperature adsorption chromatography methods, we indicate that m-LR adsorption is an entropy-driven process for each of the carbons, except the most hydrophilic and mesoporous carbon, B1. In this case, exothermic enthalpy contributions to adsorption also exist. From our overall observations, since m-LR contains molecular dimensions in the secondary micropore width range, we demonstrate that it is important to consider both the secondary micropore and the mesopore volumes for the adsorption of m-LR from aqueous solutions. Copyright 2001 Academic Press. PMID:11446779

  3. The primary steps of photosynthesis

    The two important initial steps of photosynthesis-electron transfer and energy transfer occur with great speed and efficiency. New techniques in laser optics and genetic engineering age helping us to understand why. (author). 24 refs. 8 figs

  4. 7 Steps to Aging Well

    ... Issue Past Issues Special Section 7 Steps to Aging Well Past Issues / Winter 2007 Table of Contents ... Exercise: A Guide from the National Institute on Aging is a publication from NIA that has strength, ...

  5. 7 Steps to Aging Well

    ... Past Issues Special Section 7 Steps to Aging Well Past Issues / Winter 2007 Table of Contents For ... the risk of death from automobile crashes as well as recreational and on-the-job injuries. What ...

  6. Creating single-atom Pt-ceria catalysts by surface step decoration

    Dvořák, Filip; Farnesi Camellone, Matteo; Tovt, Andrii; Tran, Nguyen-Dung; Negreiros, Fabio R.; Vorokhta, Mykhailo; Skála, Tomáš; Matolínová, Iva; Mysliveček, Josef; Matolín, Vladimír; Fabris, Stefano

    2016-02-01

    Single-atom catalysts maximize the utilization of supported precious metals by exposing every single metal atom to reactants. To avoid sintering and deactivation at realistic reaction conditions, single metal atoms are stabilized by specific adsorption sites on catalyst substrates. Here we show by combining photoelectron spectroscopy, scanning tunnelling microscopy and density functional theory calculations that Pt single atoms on ceria are stabilized by the most ubiquitous defects on solid surfaces--monoatomic step edges. Pt segregation at steps leads to stable dispersions of single Pt2+ ions in planar PtO4 moieties incorporating excess O atoms and contributing to oxygen storage capacity of ceria. We experimentally control the step density on our samples, to maximize the coverage of monodispersed Pt2+ and demonstrate that step engineering and step decoration represent effective strategies for understanding and design of new single-atom catalysts.

  7. Step sites in syngas catalysis

    Rostrup-Nielsen, J.; Nørskov, Jens Kehlet

    2006-01-01

    Step sites play an important role in many catalytic reactions. This paper reviews recent results on metal catalysts for syngas reactions with emphasis on steam reforming. Modern characterization techniques (STEM, HREM...) and theoretical calculations (DFT) has allowed a more quantitative...... explanation of the impact of step sites on catalyst activity and side reactions such as carbon formation. This leads to a discussion of principles for catalyst promotion....

  8. SYNTHESIS AND CHARACTERIZATIONOF ORGANIC FUNCTIONALIZED MESOPOROUS SILICA AND EVALUATE THEIR ADSORPTIVE BEHAVIOR FOR REMOVAL OF METHYLENE BLUE FROM AQUEOUS SOLUTION

    Sameer H. Kareem

    2014-01-01

    Full Text Available Three Mesoporous Silica (MPS with different functional groups were prepared by one-step synthesis based on the simultaneous hydrolysis and condensation of tetraethoxy silane with organo-silane in the presence of template surfactant Polydimethylsiloxane-Polyethyleneoxide (PDMS-PEO. The prepared materials were characterized by Fourier Transform Infrared Spectroscopy (FTIR, Thermogravimetric Analysis (TGA and nitrogen adsorption-desorption experiments. The results indicate that the preparation of methyl and phenyl functionalized silica were successful. The adsorption behavior of methylene blue from aqueous systems onto these mesoporous silica has been studied. Batch experiments were carried out to measure the adsorption as a function of contact time, initial concentration (2.5-20 mg L-1 and temperature (288, 298, 308 and 318 K. The equilibrium of the process was achieved within (30-60 min. The adsorption of methylene blue on the mesoporous silica increases with increasing temperature which indicating an endothermic process. Adsorption isotherms were fitted with the Langmuir, Freundlich models. The kinetic data were analyzed using pseudo-first- order and pseudo-second-order models and intraparticle diffusion. The adsorption kinetics of methylene blue on mesoporous silica matched well with pseudo-second order kinetic model.

  9. Adsorption of acid and basic dyes by sludge-based activated carbon:Isotherm and kinetic studies

    李鑫; 王广智; 李伟光; 王萍; 宿程远

    2015-01-01

    A batch experiment was conducted to investigate the adsorption of an acid dye (Acid Orange 51) and a basic dye (Safranine) from aqueous solutions by the sludge-based activated carbon (SBAC). The results show that the adsorption of Acid Orange 51 decreases at high pH values, whereas the uptake of Safranine is higher in neutral and alkaline solutions than that in acidic conditions. The adsorption time needed for Safranine to reach equilibrium is shorter than that for Acid Orange 51. The uptakes of the dyes both increase with temperature increasing, indicating that the adsorption process of the dyes onto SBAC is endothermic. The equilibrium data of the dyes are both best represented by the Redlich−Peterson model. At 25 °C, the maximum adsorption capacities of SBAC for Acid Orange 51 and Safranine are 248.70 mg/g and 525.84 mg/g, respectively. The Elovich model is found to best describe the adsorption process of both dyes, indicating that the rate-limiting step involves the chemisorption. It can be concluded that SBAC is a promising material for the removal of Acid Orange 51 and Safranine from aqueous solutions.

  10. Comparative analysis of tropaeolin adsorption onto raw and acid-treated kaolinite: optimization by Response Surface Methodology.

    de Sales, Priscila F; Magriotis, Zuy M; Rossi, Marco A L S; Resende, Ricardo F; Nunes, Cleiton A

    2015-03-15

    The comparative adsorption of Tropaeolin (TP) onto raw kaolinite (RK) and kaolinite submitted to acid treatment (AK) was studied. RK and AK were characterized by zeta potential and energy dispersive X-ray spectroscopy (EDS). The adsorption was investigated using Composite Central Design (CCD) and the parameters evaluated were initial TP solution concentration, quantity of adsorbent and the pH of the solution. The optimized parameters were: initial TP solution concentration of 75 mg L(-1), pH 4 and 0.12 g adsorbent. Kinetic data were evaluated by pseudo-first order, pseudo-second order and Avrami models. The equilibrium adsorption was analyzed by Langmuir, Freundlich and Sips isotherms. The kinetic data were best fitted to the pseudo-second order model. The Sips isotherm model gives the better correlation to predict the adsorption equilibrium. The maximum adsorption capacities were 18.3 mg g(-1) and 23.2 mg g(-1) for RK and AK, respectively. The calculated thermodynamic parameters showed that the process was spontaneous, endothermic and involving the disorganization of the adsorption system for both adsorbents. The desorption step showed that the AK sample was more suitable as an adsorbent. PMID:25559496

  11. Adsorption of Zn2+ ions onto NaA and NaX zeolites: Kinetic, equilibrium and thermodynamic studies

    The adsorption of Zn2+ onto NaA and NaX zeolites was investigated. The samples were synthesized according to a hydrothermal crystallization using aluminium isopropoxide (Al[OCH(CH3)2]3) as a new alumina source. The effects of pH, initial concentration, solid/liquid ratio and temperature were studied in batch experiments. The Freundlich and the Langmuir models were applied and the adsorption equilibrium followed Langmuir adsorption isotherm. The uptake distribution coefficient (Kd) indicated that the Zn2+ removal was the highest at minimum concentration. Thermodynamic parameters were calculated. The negative values of standard enthalpy of adsorption revealed the exothermic nature of the adsorption process whereas the negative activation entropies reflected that no significant change occurs in the internal structure of the zeolites solid matrix during the sorption of Zn2+. The negative values of Gibbs free energy were indicative of the spontaneity of the adsorption process. Analysis of the kinetic and rate data revealed that the pseudo second-order sorption mechanism is predominant and the intra particle diffusion was the determining step for the sorption of zinc ions. The obtained optimal parameters have been applied to wastewater from the industrial zone (Algeria) in order to remove the contained zinc effluents.

  12. Adsorption of zinc on manganite (γ-MnOOH):particle concentration effect and adsorption reversibility

    QIN Yan-wen; PAN Gang; ZHANG Ming-ming; LI Xian-liang

    2004-01-01

    The adsorption and desorption processes of Zn(Ⅱ) on γ-MnOOH as a function of particle concentrations (Cp) were studied. An obvious Cp effect was observed in this adsorption system. The degree of adsorption hysteresis increased greatly with the increasing of Cp, indicating that the extent of the real metastable-equilibrium states deviating from the ideal equilibrium state was enhanced with the increasing of Cp. The Cp-reversibility relationship confirmed the metastable-equilibrium adsorption (MEA) inequality (Pan, 1998a), which was the core formulation of the MEA theory. Because the MEA inequality was based on the basic hypothesis of MEA theory that adsorption density Г is not a state variable, the Cp-reversibility relationship gave indirect evidence to the basic hypothesis of MEA theory.

  13. The influence of a small amount of active sites on the adsorption kinetics of nitrogen on ruthenium

    Recently, Dahl et al. [S. Dahl, A. Logadottir, R.C. Egeberg, J.H. Larsen, I. Chorkendorff, E. Toernqvist, J.K. Norskov, Phys. Rev. Lett. 83 (1999) 1814; S. Dahl, E. Toernqvist, I. Chorkendorff, J. Catal. 192 (2000) 381] have proposed very interesting hypothesis that the rate of dissociation and adsorption of nitrogen on Ru(0 0 0 1) facet is totally dominated by the presence of a small amount of step sites on Ru(0 0 0 1) terraces. Following this idea, a kinetic model, based on applying the Statistical Rate Theory approach, was developed in order to explain if such mechanism is able to explain the observed features of the system N2/Ru(0 0 0 1). As a result, it was stated that the activation barrier for adsorption on the active (step) sites is equal to 36 kJ/mol; in turn, the adsorption energy of nitrogen atoms on the active sites is 43 kJ/mol. It implies that the rate of adsorption via the active sites is much faster than direct adsorption on the three-fold hollow sites; moreover, the occupation of the active sites is always close to zero at the investigated temperatures, so they are not blocked and may act as an indirect channel for adsorption. Thus, the rate of nitrogen adsorption on Ru(0 0 0 1) surface is governed by the rate of diffusion of nitrogen atoms from the active sites into the three-fold hollow sites. The analysis of thermodesorption spectra revealed an important role of repulsive interactions between the N atoms adsorbed on the hollow sites, the associated interaction parameter between nearest neighbors was estimated to be 5 kJ/mol. The presence of small amount of gold on Ru(0 0 0 1), apart of blocking the active sites, seems to remove the repulsion between nitrogen atoms

  14. Petroleum coke adsorption as a water management option for oil sands process-affected water

    Water is integral to both operational and environmental aspects of the oil sands industry. A water treatment option based on the use of petroleum coke (PC), a by-product of bitumen upgrading, was examined as an opportunity to reduce site oil sands process-affected water (OSPW) inventories and net raw water demand. Changes in OSPW quality when treated with PC included increments in pH levels and concentrations of vanadium, molybdenum, and sulphate. Constituents that decreased in concentration after PC adsorption included total acid-extractable organics (TAO), bicarbonate, calcium, barium, magnesium, and strontium. Changes in naphthenic acids (NAs) speciation were observed after PC adsorption. A battery of bioassays was used to measure the OSPW toxicity. The results indicated that untreated OSPW was toxic towards Vibrio fischeri and rainbow trout. However, OSPW treated with PC at appropriate dosages was not acutely toxic towards these test organisms. Removal of TAO was found to be an adsorption process, fitting the Langmuir and Langmuir–Freundlich isotherm models. For TAO concentrations of 60 mg/L, adsorption capacities ranged between 0.1 and 0.46 mg/g. This study demonstrates that freshly produced PC from fluid cokers provides an effective treatment of OSPW in terms of key constituents' removal and toxicity reduction. - Highlights: ► Treatment of oil sands process-affected water (OSPW) using petroleum coke (PC) adsorption was investigated. ► PC was effective at adsorbing naphthenic acids with higher cyclicity. ► OSPW treated with PC at appropriate dosages was not toxic towards Vibrio fisheri and rainbow trout. ► The adsorption of organic acids fitted the Langmuir and Langmuir–Freundlich isotherm models. ► PC has the potential to be an effective adsorbent to treat OSPW either directly or as a pretreatment step.

  15. Petroleum coke adsorption as a water management option for oil sands process-affected water

    Zubot, Warren [Syncrude Canada Ltd., Research and Development, Edmonton, Alberta, Canada T6N 1H4 (Canada); MacKinnon, Michael D. [OSPM Solutions Ltd., Hamilton, Ontario, Canada L8H 6X2 (Canada); Chelme-Ayala, Pamela; Smith, Daniel W. [University of Alberta, Department of Civil and Environmental Engineering, Edmonton, Alberta, Canada T6G 2W2 (Canada); Gamal El-Din, Mohamed, E-mail: mgamalel-din@ualberta.ca [University of Alberta, Department of Civil and Environmental Engineering, Edmonton, Alberta, Canada T6G 2W2 (Canada)

    2012-06-15

    Water is integral to both operational and environmental aspects of the oil sands industry. A water treatment option based on the use of petroleum coke (PC), a by-product of bitumen upgrading, was examined as an opportunity to reduce site oil sands process-affected water (OSPW) inventories and net raw water demand. Changes in OSPW quality when treated with PC included increments in pH levels and concentrations of vanadium, molybdenum, and sulphate. Constituents that decreased in concentration after PC adsorption included total acid-extractable organics (TAO), bicarbonate, calcium, barium, magnesium, and strontium. Changes in naphthenic acids (NAs) speciation were observed after PC adsorption. A battery of bioassays was used to measure the OSPW toxicity. The results indicated that untreated OSPW was toxic towards Vibrio fischeri and rainbow trout. However, OSPW treated with PC at appropriate dosages was not acutely toxic towards these test organisms. Removal of TAO was found to be an adsorption process, fitting the Langmuir and Langmuir-Freundlich isotherm models. For TAO concentrations of 60 mg/L, adsorption capacities ranged between 0.1 and 0.46 mg/g. This study demonstrates that freshly produced PC from fluid cokers provides an effective treatment of OSPW in terms of key constituents' removal and toxicity reduction. - Highlights: Black-Right-Pointing-Pointer Treatment of oil sands process-affected water (OSPW) using petroleum coke (PC) adsorption was investigated. Black-Right-Pointing-Pointer PC was effective at adsorbing naphthenic acids with higher cyclicity. Black-Right-Pointing-Pointer OSPW treated with PC at appropriate dosages was not toxic towards Vibrio fisheri and rainbow trout. Black-Right-Pointing-Pointer The adsorption of organic acids fitted the Langmuir and Langmuir-Freundlich isotherm models. Black-Right-Pointing-Pointer PC has the potential to be an effective adsorbent to treat OSPW either directly or as a pretreatment step.

  16. Removal of Cr(VI) from aqueous solutions by adsorption on MnO2.

    Gheju, Marius; Balcu, Ionel; Mosoarca, Giannin

    2016-06-01

    Adsorption of Cr(VI) on MnO2 was investigated with respect to effect of pH, temperature, ionic strength, initial Cr(VI) concentration, co-presence of different anions (HCO3(-), SO4(2-), H2PO4(-), NO3(-) and Cl(-)) and of low molecular weight natural organic materials (LMWNOM) (acetate, oxalate and citrate). The process was rapid during the first 3-5min, reaching equilibrium after one hour. Adsorption decreased with increasing pH, temperature and Cr(VI) initial concentration, and increased with increasing ionic strength. Co-presence of phosphate, sulfate, bicarbonate, citrate and oxalate hindered Cr(VI) adsorption, whereas nitrate, chloride and acetate did not exert any notable influence. The overall order of Cr(VI) adsorption suppression due to co-presence of anions and LMWNOM was H2PO4(-)>HCO3(-)>SO4(2-), and oxalate>citrate, respectively. Highest experimental equilibrium sorption capacity (0.83mgg(-1)) was obtained at 20°C and pH 5.9, while lowest (0.18mgg(-1)) was noticed in the co-presence of H2PO4(-), at 20°C and pH 6.9. Adsorption kinetics was successfully fitted by pseudo-second-order model. Mechanisms for both specific and non-specific adsorption are likely to be involved, while rate-controlling step involved both intra-particle and film diffusion processes. Cr(VI) was strongly bound to MnO2, which makes risks of its subsequent liberation into the environment to be low. PMID:26947189

  17. Adsorption of glyphosate on variable-charge, volcanic ash-derived soils.

    Cáceres-Jensen, L; Gan, J; Báez, M; Fuentes, R; Escudey, M

    2009-01-01

    Glyphosate (N-phosphonometylglycine) is widely used due to its broad spectrum of activity and nonselective mode of action. In Chile it is the most used herbicide, but its adsorption behavior in the abundant and widespread variable charge soils is not well understood. In this study, three volcanic ash-derived soils were selected, including Andisols (Nueva Braunau and Diguillin) and Ultisols (Collipulli), to evaluate the adsorption kinetics, equilibrium isotherms, and the effect of pH in glyphosate adsorption. The influence of glyphosate on soil phosphorus retention was also studied. Glyphosate was rapidly and strongly adsorbed on the selected soils, and adsorption isotherms were well described by the Freundlich relationship with strong nonlinearity (n(fads) Andisol soils without the addition of glyphosate had similar mean K(ads) values for Nueva Braunau (5.68) and Diguillin (7.38). Collipulli had a mean K(ads) value of 31.58. During the successive desorption steps, glyphosate at the highest level increased K(ads) values for phosphate in the Andisol soils but had little effect in the Ultisol soil. This different behavior was probably due to the irreversible occupation of some adsorption sites by glyphosate in the Ultisol soil attributed to the dominant Kaolinite mineral. Results from this study suggest that in the two types of volcanic soils, different mechanisms are involved in glyphosate and phosphate adsorption and that long-term use of glyphosate may impose different effects on the retention and availability of phosphorus. Volcanic ash-derived soils have a particular environmental behavior in relation to the retention of organic contaminants, representing an environmental substrate that may become highly polluted over time due to intensive agronomic uses. PMID:19465720

  18. Conceptual adsorption models and open issues pertaining to performance assessment

    Recently several articles have been published that question the appropriateness of the distribution coefficient, Rd, concept to quantify radionuclide migration. Several distinct issues surrounding the modeling of nuclide retardation. The first section defines adsorption terminology and discusses various adsorption processes. The next section describes five commonly used adsorption conceptual models, specifically emphasizing what attributes that affect adsorption are explicitly accommodated in each model. I also review efforts to incorporate each adsorption model into performance assessment transport computer codes. The five adsorption conceptual models are (1) the constant Rd model, (2) the parametric Rd model, (3) isotherm adsorption models, (4) mass action adsorption models, and (5) surface-complexation with electrostatics models. The final section discusses the adequacy of the distribution ratio concept, the adequacy of transport calculations that rely on constant retardation factors and the status of incorporating sophisticated adsorption models into transport codes. 86 refs., 1 fig., 1 tab

  19. Conceptual adsorption models and open issues pertaining to performance assessment

    Recently several articles have been published that question the appropriateness of the distribution coefficient, Rd, concept to quantify radionuclide migration. Several distinct issues are raised by various critics. In this paper I provide some perspective on issues surrounding the modeling of nuclide retardation. The first section defines adsorption terminology and discusses various adsorption processes. The next section describes five commonly used adsorption conceptual models, specifically emphasizing what attributes that affect adsorption are explicitly accommodated in each model. I also review efforts to incorporate each adsorption model into performance assessment transport computer codes. The five adsorption conceptual models are (1) the constant Rd model, (2) the parametric Rd model, (3) isotherm adsorption models, (4) mass-action adsorption models, and (5) surface-complexation with electrostatics models. The final section discusses the adequacy of the distribution ratio concept, the adequacy of transport calculations that rely on constant retardation factors and the status of incorporating sophisticated adsorption models into transport codes

  20. Competitive adsorption of heavy metal ions on peat

    LIU Zhi-rong; ZHOU Li-min; WEI Peng; ZENG Kai; WEN Chuan-xi; LAN Hui-hua

    2008-01-01

    The uptake capacities, and the adsorption kinetics, of copper, Cu(Ⅱ), nickel, Ni(Ⅱ), and cadmium, Cd(Ⅱ), on peat have been studied under static conditions. The results show that the adsorption rates are rapid: equilibrium is reached in twenty minutes. The adsorption of copper, nickel and cadmium is pH dependent over the pH range from 2 to 6. The adsorption kinetics can be excellently described by the Elovich kinetic equation. The adsorption isotherm fits a Langmuir model very well. The adsorption capacifies follow the order Cu2+>Ni2+>Cd2+ in single-component systems and the competitive adsorption capacities fall in the decreasing order Cu2+> Ni2+>Cd2+ in multi-component systems. The adsorption capacities of these three heavy metal ions on peat are consistent with their observed competitive adsorption capacities.

  1. Site blocking and CO/sulfur site exchange processes on stepped Pt surfaces

    The influence of preadsorbed sulfur on the adsorption of CO on Pt(355) and Pt(322) is investigated systematically for sulfur precoverages between 0.02 and 0.30 ML by in situ x-ray photoelectron spectroscopy of the C 1s and S 2p core levels. The two surfaces have the same nominal terrace width of 5 atomic rows, but different step orientation. For both, at low temperatures (130 and 150 K), S preferentially adsorbs at the steps and passivates them for CO adsorption. The required S precoverage is significantly smaller for Pt(322), because of the lower number of steps as a result of the S-induced double-step formation. Upon heating, population of step sites with CO occurs due to irreversible CO/S site exchange. At low S precoverages, the characteristic transition temperatures of 165 K for Pt(355) and 245 K for Pt(322) are significantly different, indicating a higher activation barrier for the CO/S site exchange process for Pt(322). For medium to high S precoverages the transition temperature stays unchanged for Pt(322) but increases for Pt(355). The observed behavior is attributed to a kinetic passivation of the steps by sulfur at low temperatures, which is lifted upon heating.

  2. Adsorption of Strontium by Vermiculite and Montmorillonite

    The adsorption of Sr2+ by vermiculite and montmorillonite and the effects of experimental conditions were investigated. The results show that more than 96.8% and 98.5% of the total Sr2+ can be adsorbed by the vermiculite and montmorillonite from pH=8 Sr2+ solution of 20 MBq/L (C0) at room temperature, respectively. The equilibrium of adsorption by vermiculite and montmorillonite was achieved within 2 h and 15 min severally, and the optimum pH both ranged from 3 to 10. More than 82.7% and 98.7% Sr2+ can be desorbed by 2 mol/L HNO3 solution from the vermiculite and montmorillonite. The adsorption rate of Sr2+ by vermiculite and montmorillonite will decrease in presence of coexistent Ca2+, while modified by [Ag(NH3)2]+ and 1 mol/L HCl can improve the adsorption abilities of vermiculite for Sr2+, but decreased by high temperature.As for montmorillonite, modified by [Cu(NH3)4]2+ can improve adsorption, however, by [Ag(NH3)2]+ and high temperature can decrease. Additionally, the modified vermiculite and montmorillonite were analyzed by X-ray diffractometer system (XRD). The results show that the spectra of the modified vermiculite or montmorillonite are different from that of the original one. (authors)

  3. Adsorption of iodine on silver wire

    It is an important process in which iodine is adsorbed on silver wire during the preparation of 125I seed sources. In this paper, a technique of adsorption of iodine on silver wire was studied. The influence of several factors, such as the type of reagent for halogenation, the time for halogenation, the time for adsorption, pH value, ion concentration, carrier iodine and so on, on the utilization rate of 131I was investigated, and the effectiveness of our proposed technique for adsorption of iodine on silver wire was confirmed. The procedure is summarized as follows: silver wire acidification: using 4 mol/L HNO3 as halogenation agent, stirring acidified for 20 min; silver wire halogenation: used 2 mol/L NaClO3 as halogenated agent, halogenation for 3 h; adsorption of iodine on silver wire: room temperature, pH value for the reaction is about 3, the time for adsorption is 30 min, carrier iodine is 27.5 μg. Original radioactivity of reaction solution was determined based on radioactivity of source-core that user required. (authors)

  4. Membrane potential generated by ion adsorption.

    Tamagawa, Hirohisa; Morita, Sachi

    2014-01-01

    It has been widely acknowledged that the Goldman-Hodgkin-Katz (GHK) equation fully explains membrane potential behavior. The fundamental facet of the GHK equation lies in its consideration of permeability of membrane to ions, when the membrane serves as a separator for separating two electrolytic solutions. The GHK equation describes that: variation of membrane permeability to ion in accordance with ion species results in the variation of the membrane potential. However, nonzero potential was observed even across the impermeable membrane (or separator) separating two electrolytic solutions. It gave rise to a question concerning the validity of the GHK equation for explaining the membrane potential generation. In this work, an alternative theory was proposed. It is the adsorption theory. The adsorption theory attributes the membrane potential generation to the ion adsorption onto the membrane (or separator) surface not to the ion passage through the membrane (or separator). The computationally obtained potential behavior based on the adsorption theory was in good agreement with the experimentally observed potential whether the membrane (or separator) was permeable to ions or not. It was strongly speculated that the membrane potential origin could lie primarily in the ion adsorption on the membrane (or separator) rather than the membrane permeability to ions. It might be necessary to reconsider the origin of membrane potential which has been so far believed explicable by the GHK equation. PMID:24957176

  5. Membrane Potential Generated by Ion Adsorption

    Hirohisa Tamagawa

    2014-06-01

    Full Text Available It has been widely acknowledged that the Goldman-Hodgkin-Katz (GHK equation fully explains membrane potential behavior. The fundamental facet of the GHK equation lies in its consideration of permeability of membrane to ions, when the membrane serves as a separator for separating two electrolytic solutions. The GHK equation describes that: variation of membrane permeability to ion in accordance with ion species results in the variation of the membrane potential. However, nonzero potential was observed even across the impermeable membrane (or separator separating two electrolytic solutions. It gave rise to a question concerning the validity of the GHK equation for explaining the membrane potential generation. In this work, an alternative theory was proposed. It is the adsorption theory. The adsorption theory attributes the membrane potential generation to the ion adsorption onto the membrane (or separator surface not to the ion passage through the membrane (or separator. The computationally obtained potential behavior based on the adsorption theory was in good agreement with the experimentally observed potential whether the membrane (or separator was permeable to ions or not. It was strongly speculated that the membrane potential origin could lie primarily in the ion adsorption on the membrane (or separator rather than the membrane permeability to ions. It might be necessary to reconsider the origin of membrane potential which has been so far believed explicable by the GHK equation.

  6. Dynamic adsorption of radon on activated carbon

    The adsorption of 222Rn from air onto activated carbon was studied over the range 0 to 550C. A sharp pulse of radon was injected into an air stream that flowed through a bed of activated carbon. The radon concentration in the exit from the column was continuously monitored using a zinc sulfide α-scintillation flow cell. Elution curves were analyzed to determine the dynamic adsorption coefficient and the number of theoretical stages. Five types of activated carbon were tested and the dynamic adsorption coefficient was found to increase linearly with surface area in the range 1000 to 1300 m2g-1. The adsorptive capacity of activated carbon was reduced by up to 30% if the entering gas was saturated with water vapor and the bed was initially dry. If the bed was allowed to equilibrate with saturated air, the adsorptive capacity was too low to be of practical use. The minimum height equivalent to a theoretical stage (HETS) was about four times the particle diameter and occurred at superficial velocities within the range 0.002 to 0.02 m s-1. For superficial velocities above 0.05 m s-1, the HETS was determined by the rate of mass transfer. The application of these results to the design of activated carbon systems for radon retention is discussed

  7. Adsorption of Cadmium By Silica Chitosan

    Moftah Ali

    2013-03-01

    Full Text Available The adsorption process depends on initial concentration of Cd2+ and ratio of  chitosan in adsorbent. The present study deals with the competitive adsorption of Cd2+ ion onto silica graft with chitosan. Batch adsorption experiments were performed at five different initial Cd2+ concentrations (5, 10, 15, 20 and 25 ppm, on five different proportion from silica to chitosan (100%, 95%, 85%, 75% and 65% as adsorbent at pH 5. In the recovery process, the high recovery at 0.5 mg and observed the recovery decrease with increasing the initial concentration of Cd2+, and the low recovery at 0.25 mg from Cd2+. In this study, the adsorption capacity of Cd2+ in regard to the ratio of silica and chitosan hybrid adsorbents are examined in detail. The aim of this study to explore effects of initial concentrations of Cd2+, and the ratio of silica to chitosan on the adsorption and recovery of Cd2+.

  8. Adsorption behavior of heavy metals on biomaterials.

    Minamisawa, Mayumi; Minamisawa, Hiroaki; Yoshida, Shoichiro; Takai, Nobuharu

    2004-09-01

    We have investigated adsorption of Cd(II) and Pb(II) at pH 2-6.7 onto the biomaterials chitosan, coffee, green tea, tea, yuzu, aloe, and Japanese coarse tea, and onto the inorganic adsorbents, activated carbon and zeolite. High adsorptive capabilities were observed for all of the biomaterials at pH 4 and 6.7. In the adsorption of Cd(II), blend coffee, tea, green tea, and coarse tea have comparable loading capacities to activated carbon and zeolite. Although activated carbon, zeolite, and chitosan are utilized in a variety of fields such as wastewater treatment, chemical and metallurgical engineering, and analytical chemistry, these adsorbents are costly. On the other hand, processing of the test biomaterials was inexpensive, and all the biomaterials except for chitosan were able to adsorb large amounts of Pb(II) and Cd(II) ions after a convenient pretreatment of washing with water followed by drying. The high adsorption capability of the biomaterials prepared from plant materials is promising in the development of a novel, low-cost adsorbent. From these results, it is concluded that heavy metal removal using biomaterials would be an effective method for the economic treatment of wastewater. The proposed adsorption method was applied to the determination of amounts of Cd(II) and Pb(II) in water samples. PMID:15373400

  9. Transoral Robotic Surgery: Step-by-Step Radical Tonsillectomy

    Jose Granell

    2014-01-01

    Full Text Available Introduction. Transoral robotic surgery (TORS radical tonsillectomy is an emerging minimally invasive surgical procedure for the treatment of cancer of the tonsil. The detailed surgical technique and claims for its reproducibility have been previously published. Case Presentation. We present a patient with a T2N2bM0 epidermoid carcinoma of the tonsil to illustrate step by step the surgical procedure for TORS radical tonsillectomy. Neck dissection and TORS were staged. No surgical reconstruction of the defect was required. No tracheostomy was necessary. The patient could eat without any feeding tube and was on full oral diet on the fifth postoperative day. Discussion. The transoral approach offers the benefits of minimally invasive surgery to patients with cancer of the tonsil. The excellent exposure and high precision provided by robotic instrumentation allow the surgeon to closely follow and accomplish the surgical steps, which is the best warranty for safety and effectiveness.

  10. Monte Carlo Simulations of the Adsorption of Anisotropic Noninteracting Molecules on the (111) Surface of a FCC Crystal

    Filimonov, S. N.; Hervieu, Yu. Yu.

    2016-04-01

    We present results of computer Monte Carlo simulations of the formation of adsorption layers composed of noninteracting molecules of benzene, anthracene, and pentacene on the Ag(111) surface. The dependences of the chemical potential of the molecules on the density of the molecular layer (surface coverage) are obtained. By means of the thermodynamic integration method the configurational entropy of the molecular layer is evaluated as a function of surface coverage. It is shown that the substitution of benzene by pentacene results in a more than twofold decrease of the maximum entropy of the molecular layer. The presence of steps on the substrate surface also leads to a decrease of the molecular layer entropy. If the distance between the steps is comparable to the linear size of the molecule, the molecules in dense adsorption layers orient preferentially parallel to the step edges.

  11. Step by step installation guide of a digital preservation infrastructure

    Birello, Giancarlo; Fucile, Ivano; Giovanetti, Valter; Perin, Anna; Minuzzo, Tiziano

    2012-01-01

    The Ceris-CNR project of digital preservation infrastructure has been committed by Bess (Social Science Electronic Library of Piemonte) for years 2011-2012 sponsored by Compagnia di San Paolo of Turin. Ceris-CNR role is to handle all the post-scan of the digitalization, for this purpose it has deployed the software and server platforms of the repository and also the web portal for the presentation, research and consulting. This report is a guide of step by step followed to build the dig...

  12. Microsoft Windows Sharepoint Services 3.0 Step by Step

    Londer, Olga; Bleeker, Todd; Coventry, Penelope

    2007-01-01

    Experience learning made easy-and quickly teach yourself how to use Windows SharePoint Services to enable effective team collaboration. With Step By Step, you set the pace-building and practicing the skills you need, just when you need them! Build your own SharePoint site with easy-to-use templatesCreate lists and libraries to store informationAdd discussion boards, wikis, and blogsSet up Document and Meeting Workspaces for easy collaborationShare calendars, contacts, and data from Microsoft Office programsCustomize your pages with Web Parts Your all-in-one learning experience includes: Fi

  13. Writing a Simulation Scenario: A Step-By-Step Guide.

    Bambini, Deborah

    2016-02-01

    Simulation is becoming a widely used method of helping nurses learn and maintain competency in the clinical area for both staff educators in clinical settings and nursing faculty in academic settings. Designing an effective simulation experience requires thoughtful planning, knowledge of educational principles, and knowledge of best practices in both simulation and clinical practice. An evidence-based strategy for writing a simulation scenario for nurses and other health care providers in any setting is described. A step-by-step process is outlined that incorporates best practices. Examples and suggestions are provided to help readers create quality simulation experiences. PMID:26909455

  14. Partial return yoke for MICE step IV and final step

    This paper reports on the progress of the design and construction of a retro-fitted return yoke for the international Muon Ionization Cooling Experiment (MICE). MICE is a proof-of-principle experiment aiming to demonstrate ionization cooling experimentally. In earlier studies we outlined how a partial return yoke can be used to mitigate stray magnetic field in the experimental hall; we report on the progress of the construction of the partial return yoke for MICE Step IV. We also discuss an extension of the Partial Return Yoke for the final step of MICE; we show simulation results of the expected performance.

  15. Linear, Step by Step Managerial Performance, versus Exponential Performance

    George MOLDOVEANU

    2011-04-01

    Full Text Available The paper proposes the transition from the potential management concept, which its authors approached by determining its dimension (Roşca, Moldoveanu, 2009b, to the linear, step by step performance concept, as an objective result of management process. In this way, we “answer” the theorists and practitioners, who support exponential management performance. The authors, as detractors of the exponential performance, are influenced by the current crisis (Roşca, Moldoveanu, 2009a, by the lack of organizational excellence in many companies, particularly in Romanian ones and also reaching “the finality” in the evolved companies, developed into an uncontrollable speed.

  16. Microsoft Office SharePoint Designer 2007 Step by Step

    Coventry, Penelope

    2008-01-01

    The smart way to learn Office SharePoint Designer 2007-one step at a time! Work at your own pace through the easy numbered steps, practice files on CD, helpful hints, and troubleshooting tips to master the fundamentals of building customized SharePoint sites and applications. You'll learn how to work with Windows® SharePoint Services 3.0 and Office SharePoint Server 2007 to create Web pages complete with Cascading Style Sheets, Lists, Libraries, and customized Web parts. Then, make your site really work for you by adding data sources, including databases, XML data and Web services, and RSS fe

  17. Information marketing business entrepreneur's step-by-step startup guide

    magazine, Entrepreneur

    2012-01-01

    A six-figure income from information? Yes! It sounds easy because it is. You've got information that millions of others are looking for and now you can learn how to package, price and sell it.The experts at Entrepreneur take you step by step, jumpstarting your thinking about your area of expertise and showing you how to convert it into a high-demand information product. Following the example set by today's most successful information marketers, you learn the ins and outs of running your own information marketing business using proven strategies and effective marketing techniques.

  18. Microsoft® Office Access™ 2007 Step by Step

    Lambert, Steve; Lambert, Joan

    2009-01-01

    Experience learning made easy-and quickly teach yourself how to build database solutions with Access 2007. With Step By Step, you set the pace-building and practicing the skills you need, just when you need them! Build databases from scratch or from templatesExchange data with other databases and Office documentsCreate forms to simplify data entryUse filters and queries to find and analyze informationDesign rich reports that help make your data meaningfulHelp prevent data corruption and unauthorized access Your all-in-one learning experience includes: Files for building skills and practic

  19. Partial Return Yoke for MICE Step IV and Final Step

    Witte, Holger [Brookhaven; Plate, Stephen [Brookhaven; Berg, J.Scott [Brookhaven; Tarrant, Jason [Rutherford; Bross, Alan [Fermilab

    2015-06-01

    This paper reports on the progress of the design and construction of a retro-fitted return yoke for the international Muon Ionization Cooling Experiment (MICE). MICE is a proof-of-principle experiment aiming to demonstrate ionization cooling experimentally. In earlier studies we outlined how a partial return yoke can be used to mitigate stray magnetic field in the experimental hall; we report on the progress of the construction of the partial return yoke for MICE Step IV. We also discuss an extension of the Partial Return Yoke for the final step of MICE; we show simulation results of the expected performance.

  20. Partial return yoke for MICE step IV and final step

    Witte, H. [Brookhaven National Lab. (BNL), Upton, NY (United States); Plate, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Berg, J. S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tarrant, J. [Science and Technology Facilities Council (STFC), Oxford (United Kingdom). Rutherford Appleton Lab. (RAL); Bross, A. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2015-05-03

    This paper reports on the progress of the design and construction of a retro-fitted return yoke for the international Muon Ionization Cooling Experiment (MICE). MICE is a proof-of-principle experiment aiming to demonstrate ionization cooling experimentally. In earlier studies we outlined how a partial return yoke can be used to mitigate stray magnetic field in the experimental hall; we report on the progress of the construction of the partial return yoke for MICE Step IV. We also discuss an extension of the Partial Return Yoke for the final step of MICE; we show simulation results of the expected performance.

  1. Selective adsorption of cationic dyes from aqueous solution by polyoxometalate-based metal-organic framework composite

    Liu, Xiaoxia; Gong, Wenpeng; Luo, Jing; Zou, Chentao; Yang, Yun; Yang, Shuijin

    2016-01-01

    A novel environmental friendly adsorbent H6P2W18O62/MOF-5 was synthesized by a simple one-step reaction under solvothermal conditions and characterized by XRD, FTIR, thermogravimetric analyses (TGA) and N2 adsorption-desorption isotherms. The removal rate of H6P2W18O62/MOF-5 was quite greater (85%) than that of MOF-5 (almost zero), showing that the adsorption performance of porous MOF-5 can be improved through the modification of H6P2W18O62. Further study revealed that H6P2W18O62/MOF-5 exhibited a fast adsorption rate and selective adsorption ability towards the cationic dyes in aqueous solution. The removal rate was up to 97% for cationic dyes methylene blue (MB) and 68% for rhodamine B(Rhb) within 10 min. However, anionicdye methyl orange(MO) can only reach to 10%. The influences including initial concentration, contact time, initial solution pH and temperature of MB adsorption onto H6P2W18O62/MOF-5 were investigated in detail. The kinetic study indicated that the adsorption of MB onto H6P2W18O62/MOF-5 followed the pseudo second-order model well. The isotherm obtained from experimental data fitted the Langmuir model, yielding maximum adsorption capacity of 51.81 mg/g. The thermodynamic parameters analysis illustrated that the MB adsorption onto H6P2W18O62 immobilized MOF-5 was spontaneous and endothermic process. Besides, these results implied that designing a novel material polyoxometalate-based metal-organic frameworks is great potential for removing cationic organic pollutants and even extended to improve other specific application.

  2. Relationship between carbon microstructure, adsorption energy and hydrogen adsorption capacity at different temperatures

    Various microporous materials such as activated carbons, nano-tubes, synthetic microporous carbons as well as metal organic framework materials are being considered for hydrogen storage applications by means of physical adsorption. To develop materials of practical significance for hydrogen storage it is important to understand the relationships between pore sizes, adsorption energies and adsorption capacities. The pore size distribution (PSD) characterization is traditionally obtained from the analysis of nitrogen adsorption isotherms measured at 77 K. However, a portion of the pores accessible to H2 may not be accessible to N2 at this temperature. Therefore, it was recently proposed to use the DFT analysis of H2 adsorption isotherms to characterize pore structure of materials considered for hydrogen storage applications. In present work, adsorption isotherms of H2 and N2 at cryogenic temperatures are used for the characterization of carbon materials. Adsorption measurements were performed with Autosorb 1 MP (Quantachrome Instruments, Boynton Beach, Florida, USA). As an example, Fig 1 compares PSDs calculated for the activated carbon sample (F400, Calgon Carbon) using combined H2 and N2 data, and using N2 isotherm only. The nitrogen derived PSD does not include certain amount of micropores which are accessible to H2 but not to N2 molecules. Obviously, the difference in the calculated PSDs by the two methods will depend on the actual content of small micropores in a given sample. Carbon adsorption properties can also be characterized by the isosteric heat of adsorption, Qst, related to the adsorption energy and dependent on the carbon pore/surface structure. Fig 2 shows Qst data calculated using the Clausius-Clapeyron equation from H2 isotherms measured at 77 K and 87 K for the carbon molecular sieve CMS 5A (Takeda), oxidized single wall nano-tubes (SWNT), and graphitized carbon black (Supelco). The Qst values decrease with increasing pore sizes. The highest Qst is

  3. Density Functional Theory Study of the Adsorption of Hydrazine on the Perfect and Defective Copper (100), (110), and (111) Surfaces

    Tafreshi, S. S.; Roldan, A.; de Leeuw, N. H.

    2014-01-01

    We have calculated the adsorption of the reducing agent hydrazine (N2H4) on copper surfaces using density functional theory calculations with a correction for the long-range interactions (DFT-D2). We have modeled the perfect and a number of defective Cu(100), (110), and (111) surfaces, which are found in the experimentally produced structures of copper nanoparticles. We have studied adsorption of hydrazine at three types of defects in the surfaces, i.e., monatomic steps, Cu adatoms, and Cu va...

  4. Trends in Atomic Adsorption on Titanium Carbide and Nitride

    Vojvodic, Aleksandra; Ruberto, Carlo; Lundqvist, Bengt I.

    2005-01-01

    Extensive density-functional calculations on atomic chemisorption of H, B, C, N, O, F, Al, Si, P, S, and Cl on the polar TiC(111) and TiN(111) yield similar adsorption trends for the two surfaces: (i) pyramid-like adsorption-energy trends along the adatom periods; (ii) strongest adsorption for O, C, N, S, and F; (iii) large adsorption variety; (iv) record-high adsorption energy for O (8.4-8.8 eV). However, a stronger adsorption on TiN is found for elements on the left of the periodic table an...

  5. Adsorption of uranium by sulfonamide type polymers

    The preferential adsorption of uranium ions was investigated with a series of poly (styrenesulfonamide)s. Among the poly (styrenesulfonamide) derivatives, those having carboxyl groups, derived from iminodiacetic acid (PSt-Imi), β-alanine (PSt-Ala), glycine (PSt-Gly), and sarcosine (PSt-Sar) were qualified for further discussion. However, it was found that the amount of adsorption of uranium ions by PSt-Imi decreased as magnesium ion or calcium ion was added to the artificial seawater. The inhibitory effect of the latter was larger than that of the former. The adsorption isotherm of uranium on PSt-Imi followed Freundlich's formula and the slope was estimated to be unity. (author)

  6. Adsorption on smooth electrodes: A radiotracer study

    Adsorption on solids is a complicated process and in most cases, occurs as the early stage of other more complicated processes, i.e. chemical reactions, electrooxidation, electroreduction. The research reported here combines the electroanalytical method, cyclic voltammetry, and the use of radio-labeled isotopes, soft beta emitters, to study adsorption processes at smooth electrodes. The in-situ radiotracer method is highly anion (molecule) specific and provides information on the structure and composition of the electric double layer. The emphasis of this research was on studying adsorption processes at smooth electrodes of copper, gold, and platinum. The application of the radiotracer method to these smooth surfaces have led to direct in-situ measurements from which surface coverage was determined; anions and molecules were identified; and weak interactions of adsorbates with the surface of the electrodes were readily monitored. 179 refs

  7. Novel nano bearings constructed by physical adsorption

    Zhang, Yongbin

    2015-09-01

    The paper proposes a novel nano bearing formed by the physical adsorption of the confined fluid to the solid wall. The bearing is formed between two parallel smooth solid plane walls sliding against one another, where conventional hydrodynamic lubrication theory predicted no lubricating effect. In this bearing, the stationary solid wall is divided into two subzones which respectively have different interaction strengths with the lubricating fluid. It leads to different physical adsorption and slip properties of the lubricating fluid at the stationary solid wall respectively in these two subzones. It was found that a significant load-carrying capacity of the bearing can be generated for low lubricating film thicknesses, because of the strong physical adsorption and non-continuum effects of the lubricating film.

  8. Adsorption on Highly Ordered Porous Alumina

    Mistura, Giampaolo; Bruschi, Lorenzo; Lee, Woo

    2016-04-01

    Porous anodic aluminum oxide (AAO) is characterized by a regular arrangement of the pores with a narrow pore size distribution over extended areas, uniform pore depth, and solid pore walls without micropores. Thanks to significant improvements in anodization techniques, structural engineering of AAO allows to accurately tailor the pore morphology. These features make porous AAO an excellent substrate to study adsorption phenomena. In this paper, we review recent experiments involving the adsorption in porous AAO. Particular attention will be devoted to adsorption in straight and structured pores with a closed end which shed new light on fundamental issues like the origin of hysteresis in closed end pores and the nature of evaporation from ink-bottle pores. The results will be compared to those obtained in other synthetic materials like porous silicon and silica.

  9. The Adsorption of Polyelectrolytes on Hydroxyapatite Crystals.

    Tsortos; Nancollas

    1999-01-01

    The adsorption of two polyelectrolytes, poly-L-Glutamate and poly-L-Aspartate, on hydroxyapatite (HAP) crystals was studied both experimentally and theoretically. Langmuir adsorption isotherms were obtained for both these molecules, with binding constants K = 6 x 10(6) and 3 x 10(6) M-1, respectively, at 37.0 degreesC, pH 7.4, and 0.15 M ionic strength. A theoretical analysis of the data, based on a model proposed by Hesselink, suggested a "train-loop" type of adsorption with non-electrostatic energy terms 3.51 and 4.76 (kT) for poly-L-Glu and poly-L-Asp, respectively. Copyright 1999 Academic Press. PMID:9878142

  10. Thermodynamic cycles of adsorption desalination system

    Highlights: ► Thermodynamic cycles of adsorption desalination (AD) system have been identified all possible evaporator temperature scenarios. ► Temperature of evaporator determines the cycle. ► Higher evaporator temperature leads to higher water production if no cooling is required. -- Abstract: The potential to use waste heat to co-generate cooling and fresh water from saline water using adsorption on silica is attracting increasing attention. A variety of different thermodynamic cycles of such an adsorption desalination (AD) system arise as the temperature of the saline water evaporator is varied relative to temperature of the water used to cool the adsorbent as it adsorbs the evaporated water. In this paper, all these possible thermodynamic cycles are enumerated and analysed to determine their relative performances in terms of specific energy consumption and fresh water productivity.

  11. Adsorption of aluminium by stream particulates.

    Tipping, E; Ohnstad, M; Woof, C

    1989-01-01

    An experimental study was made of the adsorption of aluminium by fine particulates from Whitray Beck, a hill stream in NW England. Adsorption increased with Al(3) activity, pH and concentration of particles, and could be quantitatively described by the empirical equation: [Formula: see text] [particles] where square brackets indicate concentrations, curly brackets, activities, and alpha, beta and gamma are constants with values of 5.14x10(-10) (mol litre(-1))(2.015) (g particles litre(-1))(-1), 0.457, and 1.472, respectively. For the experimental data, the equation gave a correlation ratio of 0.99. The equation accounts reasonably well for the adsorption of Al by particulates from seven other streams. In applying the equation, it must be borne in mind that the desorption kinetics of Al depend on pH, and rapid reversibility (or=10%) of total monomeric Al. PMID:15092454

  12. Hydrophobic nano-carrier for lysozyme adsorption

    CANAN ALTUNBAS; FULDEN ZEYNEP URAL; MURAT UYGUN; NESIBE AVCIBASI; UGUR AVCIBASI; DENIZ AKTAS UYGUN; SINAN AKGÖL

    2016-04-01

    In this work, poly(HEMA–APH) nanoparticles were synthesized by surfactant-free emulsion polymerization technique.Magnetic behaviour was introduced by simple addition of Fe$_3$O$_4$ into the polymerization medium.Characterization of the nanoparticle was carried out by FTIR, ESR, SEM, AFM and EDX analyses. These synthesized magnetic nanoparticles were used for adsorption of lysozyme. For this purpose, adsorption conditions wereoptimized and maximum lysozyme binding capacity was found to be 278.8 mg g$^{−1}$ polymer in pH 7.0 phosphate buffer at 25$^{\\circ}$C. Desorption and reusability properties of the nanoparticles were investigated and lysozyme adsorption efficiency did not change significantly at the end of the 10 successive reuses.

  13. Heavy metal adsorption by sulphide mineral surfaces

    Jean, Gilles E.; Bancroft, G. Michael

    1986-07-01

    The adsorption of aqueous Hg 2+, Pb 2+, Zn 2+ and Cd 2+ complexes on a variety of sulphide minerals has been studied as a function of the solution pH and also as a function of the nature of the ligands in solution. Sulphide minerals are excellent scavengers for these heavy metals. The adsorption is strongly pH dependent, i.e. there is a critical pH at which the adsorption increases dramatically. The pH dependence is related to the hydrolysis of the metal ions. Indirect evidence suggests that the hydrolyzed species are adsorbed directly on the sulphide groups, probably as a monolayer. The results also suggest the presence of MCI n2- n species physisorbed on the adsorbed monolayer. A positive identification of the adsorbed species was not possible using ESCA/XPS.

  14. Efficient adsorption refrigerators integrated with heat pipes

    Wang, R.Z. [Institute of Refrigeration and Cryogenics, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200030 (China)

    2008-03-15

    Several novel ideas to use heat pipes in adsorption water chiller or ice maker are presented in this paper. Experimental results have shown that the adsorption refrigerators are very efficient. The first example of such systems is a small scale silica gel-water adsorption water chiller with cooling power rated as 10 kW; the system could be powered by 60-100 C hot water, a cooling COP = 0.4 has been achieved when driven by 85 C hot water. This adsorption chiller has been used for solar powered air conditioner and also as the chiller for CCHP system. The second example is a silica gel-water adsorption room air conditioner powered by 80 C hot water. The system is very compact and is suggested for potential applications of micro CCHP system based on fuel cells. The system has a COP of over 0.3 and cooling power of about 1 kW. The third example is the use of split heat pipes to heat or cool the adsorber for making ice in fishing boats. The application of these technologies avoids the corrosion of adsorber at the heating phase by exhausted gases and at the cooling phase by seawater, and also has the advantage of high heat transfer performance. With such arrangement and careful considerations of the arrangement of wicks in heat pipes, and also the use of composite adsorbent (calcium chloride and activated carbon)-ammonia adsorption pair, the system test has shown the specific refrigeration power for more than 730 W/kg at -15 C. (author)

  15. Multilayer adsorption mechanism of coal surface adsorption to three oxygen molecule

    WANG Xue-feng; LI Zhi-gang; WANG Xin-yang; SUN Yan-qiu

    2008-01-01

    Compared chemical bonds change situation of coal surface and oxygen mole-cules before and after coal surface adsorption to three oxygen molecules, after adsorption each oxygen molecule's chemical bond got longer, but had not broken, the coal surface's chemical bonds changed a little. It proves that the coal surface adsorption to five oxygen molecules is the physical adsorption and is the multilayer adsorption according to the op-timized geometry structure. The oxygen molecule's bond length that adsorbed by the side chain of coal surface changes most from 1.258 2×10-10 m to 1.316 8×10-10 m, which indi-cates this oxygen molecular to be the liveliest. The analysis of charge population reveals that how many electrons shift in the atom is directly proportional to the change of chemical bonds. The more electrons shift in the atom, the more molecule chemical bond changes. In the adsorption state, which is composed of coal surface and five oxygen molecules, the vibration frequency of oxygen molecules drops off, and the adsorption energy reached by calculation is 202.11 kJ/mol.

  16. Multilayer adsorption mechanism of coal surface adsorption to three oxygen molecule

    WANG Xue-feng; LI Zhi-gang; WANG Xin-yang; SUN Yan-qiu

    2008-01-01

    Compared chemical bonds change situation of coal surface and oxygen mole-cules before and after coal surface adsorption to three oxygen molecules,after adsorption each oxygen molecule's chemical bond got longer,but had not broken,the coal surface's chemical bonds changed a little.It proves that the coal surface adsorption to five oxygen molecules is the physical adsorption and is the multilayer adsorption according to the optimized geometry structure.The oxygen molecule's bond length that adsorbed by the side chain of coal surface changes most from 1.258 2×10 10 m to 1.316 8×10 10 m,which indicates this oxygen molecular to be the liveliest.The analysis of charge population reveals that how many electrons shift in the atom is directly proportional to the change of chemical bonds.The more electrons shift in the atom,the more molecule chemical bond changes.In the adsorption state,which is composed of coal surface and five oxygen molecules,the vibration frequency of oxygen molecules drops off,and the adsorption energy reached by calculation is 202.11 kJ/mol.

  17. Publishing Ethical Research: A Step-by-Step Overview

    Wester, Kelly L.

    2011-01-01

    To publish ethical research, one must conduct research responsibly, making ethical choices from the inception of the research idea and throughout the research process. Conducting and publishing ethical research is important because of the impact the results will have on the counseling profession. Steps to consider are discussed.

  18. Step by step parallel programming method for molecular dynamics code

    Parallel programming for a numerical simulation program of molecular dynamics is carried out with a step-by-step programming technique using the two phase method. As a result, within the range of a certain computing parameters, it is found to obtain parallel performance by using the level of parallel programming which decomposes the calculation according to indices of do-loops into each processor on the vector parallel computer VPP500 and the scalar parallel computer Paragon. It is also found that VPP500 shows parallel performance in wider range computing parameters. The reason is that the time cost of the program parts, which can not be reduced by the do-loop level of the parallel programming, can be reduced to the negligible level by the vectorization. After that, the time consuming parts of the program are concentrated on less parts that can be accelerated by the do-loop level of the parallel programming. This report shows the step-by-step parallel programming method and the parallel performance of the molecular dynamics code on VPP500 and Paragon. (author)

  19. Cataloging Books Step by Step. CSLA Guide No. 5.

    Smith, Ruth S.

    Designed as a beginning, how-to guide, this handbook lists 20 short steps to cataloging library materials for a church or synagogue library. The guide opens with a history and a brief explanation of the Dewey Decimal System, with special attention given to the divisions and subdivisions that fall under the category "Religion." Several references…

  20. A simple method to prepare magnetic modified beer yeast and its application for cationic dye adsorption.

    Yu, Jun-Xia; Wang, Li-Yan; Chi, Ru-An; Zhang, Yue-Fei; Xu, Zhi-Gao; Guo, Jia

    2013-01-01

    The purpose of this research is to use a simple method to prepare magnetic modified biomass with good adsorption performances for cationic ions. The magnetic modified biomass was prepared by two steps: (1) preparation of pyromellitic dianhydride (PMDA) modified biomass in N, N-dimethylacetamide solution and (2) preparation of magnetic PMDA modified biomass by a situ co-precipitation method under the assistance of ultrasound irradiation in ammonia water. The adsorption potential of the as-prepared magnetic modified biomass was analyzed by using cationic dyes: methylene blue and basic magenta as model dyes. Optical micrograph and x-ray diffraction analyses showed that Fe(3)O(4) particles were precipitated on the modified biomass surface. The as-prepared biosorbent could be recycled easily by using an applied magnetic field. Titration analysis showed that the total concentration of the functional groups on the magnetic PMDA modified biomass was calculated to be 0.75 mmol g(-1) by using the first derivative method. The adsorption capacities (q(m)) of the magnetic PMDA modified biomass for methylene blue and basic magenta were 609.0 and 520.9 mg g(-1), respectively, according to the Langmuir equation. Kinetics experiment showed that adsorption could be completed within 150 min for both dyes. The desorption experiment showed that the magnetic sorbent could be used repeatedly after regeneration. The as-prepared magnetic modified sorbent had a potential in the dyeing industry wastewater treatment. PMID:22529003

  1. Thermodynamic study of physical adsorption of oxygen on the cleavage face of lamellar crystals

    Adsorption isotherms of oxygen on the cleavage face of nine lamellar halides (NiCl2, CoBr2, CdCl2, CoI2, CdBr2, FeI2, MnI2, CaI2, PbI2) have been determined. Uniform adsorbents have been prepared by sublimation in a rapid current of inert gas. On these adsorbents, the adsorption isotherms show three steps corresponding to the formation of three successive ad-layers. At sufficiently low temperatures the ad-layers are formed during two-dimensional condensations, which are first order transitions. The analysis of the thermodynamic data derived from the adsorption isotherms, especially the entropy of the ad-layers and their critical temperature of two-dimensional condensation, suggest that the first oxygen layer is solid while the next ones are liquid. As for rare gases we observe that surface relief has an outstanding effect on the structure of the first layer. Adsorption isotherms of oxygen and argon on exfoliated graphite have also been determined. Beyond the first, the ad-layers of oxygen are liquid while these of argon are solid. (author)

  2. Adsorption of quantum dots onto polymer and Gemini surfactant films: a quartz crystal microbalance study.

    Alejo, T; Merchán, M D; Velázquez, M M

    2014-08-26

    We used quartz crystal microbalance with dissipation to study the mechanical properties, the kinetics of adsorption, and the amount of CdSe quantum dots (QDs) adsorbed onto a SiO2 sensor, referred as bare sensor, onto the sensor modified with a film of the polymer poly(maleic anhydride-alt-1-octadecene), PMAO, or with a film of the Gemini surfactant ethyl-bis(dimethyl octadecyl ammonium bromide), abbreviated as 18-2-18. Results showed that when the sensor is coated with polymer or surfactant molecules, the coverage increases compared with that obtained for the bare sensor. On the other hand, rheological properties and kinetics of adsorption of QDs are driven by QD nanoparticles. Thus, the QD films present elastic behavior, and the elasticity values are independent of the molecule used as coating and similar to the elasticity value obtained for QDs films on the bare sensor. The QD adsorption is a two-step mechanism in which the fastest process is attributed to the QD adsorption onto the solid substrate and the slowest one is ascribed to rearrangement movements of the nanoparticles adsorbed at the surface. PMID:25093530

  3. Studies on fluoride adsorption of iron-impregnated granular ceramics from aqueous solution

    This study evaluated the effectiveness of iron-impregnated granular ceramics in removing fluoride from aqueous solution. Kanuma mud, zeolite, starch and FeSO4.7H2O/Fe2O3 mixed to prepare granular ceramic at room temperature by granulation procedure with the mass ratio of 4:3:2:1. Both the adsorbents were characterized by SEM, EDS and BET surface area. The various experimental parameters investigated for fluoride adsorption from aqueous solution were: contact time, initial pH, initial fluoride concentration and temperature. The GC (FeSO4.7H2O) is more effective for fluoride removal than GC (Fe2O3) in adsorption capacity. The optimum pH for fluoride removal on GC (FeSO4.7H2O) and GC (Fe2O3) was 7.0 and 4.0, respectively. The experimental data fitted reasonably well to both Langmuir and Freundlich isotherm models for these two adsorbents. The two adsorption process followed pseudo-second-order kinetics with intra-particle diffusion as the rate determining step. The calculated thermodynamic parameters showed that both of the adsorption processes were thermodynamically favorable, spontaneous and endothermic in nature.

  4. Abatement of VOCs with Alternate Adsorption and Plasma-Assisted Regeneration: A Review

    Sharmin Sultana

    2015-04-01

    Full Text Available Energy consumption is an important concern for the removal of volatile organic compounds (VOCs from waste air with non-thermal plasma (NTP. Although the combination of NTP with heterogeneous catalysis has shown to reduce the formation of unwanted by-products and improve the energy efficiency of the process, further optimization of these hybrid systems is still necessary to evolve to a competitive air purification technology. A newly developed innovative technique, i.e., the cyclic operation of VOC adsorption and NTP-assisted regeneration has attracted growing interest of researchers due to the optimized energy consumption and cost-effectiveness. This paper reviews this new technique for the abatement of VOCs as well as for regeneration of adsorbents. In the first part, a comparison of the energy consumption between sequential and continuous treatment is given. Next, studies dealing with adsorption followed by NTP oxidation are reviewed. Particular attention is paid to the adsorption mechanisms and the regeneration of catalysts with in-plasma and post-plasma processes. Finally, the influence of critical process parameters on the adsorption and regeneration steps is summarized.

  5. Noble gas adsorption in two-dimensional zeolites: a combined experimental and density functional theory study

    Wang, Mengen; Zhong, Jianqiang; Boscoboinik, Jorge Anibal; Lu, Deyu

    Zeolites are important industrial catalysts with porous three-dimensional structures. The catalytically active sites are located inside the pores, thus rendering them inaccessible for surface science measurements. We synthesized a two-dimensional (2D) zeolite model system, consisting of an (alumino)silicate bilayer weakly bound to a Ru (0001) surface. The 2D zeolite is suitable for surface science studies; it allows a detailed characterization of the atomic structure of the active site and interrogation of the model system during the catalytic reaction. As an initial step, we use Ar adsorption to obtain a better understanding of the atomic structure of the 2D zeolite. In addition, atomic level studies of rare gas adsorption and separation by zeolite are important for its potential application in nuclear waste sequestration. Experimental studies found that Ar atoms can be trapped inside the 2D-zeolite, raising an interesting question on whether Ar atoms are trapped inside the hexagonal prism nano-cages or at the interface between the (alumino)silicate bilayer and Ru(0001), or both. DFT calculations using van der Waals density functionals were carried out to determine the preferred Ar adsorption sites and the corresponding adsorption energies. This research used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704.

  6. Protein diffusion and long-term adsorption states at charged solid surfaces.

    Kubiak-Ossowska, Karina; Mulheran, Paul A

    2012-11-01

    The diffusion pathways of lysozyme adsorbed to a model charged ionic surface are studied using fully atomistic steered molecular dynamics simulation. The simulations start from existing protein adsorption trajectories, where it has been found that one particular residue, Arg128 at the N,C-terminal face, plays a crucial role in anchoring the lysozyme to the surface [Langmuir 2010 , 26 , 15954 - 15965]. We first investigate the desorption pathway for the protein by pulling the Arg128 side chain away from the surface in the normal direction, and its subsequent readsorption, before studying diffusion pathways by pulling the Arg128 side chain parallel to the surface. We find that the orientation of this side chain plays a decisive role in the diffusion process. Initially, it is oriented normal to the surface, aligning in the electrostatic field of the surface during the adsorption process, but after resorption it lies parallel to the surface, being unable to return to its original orientation due to geometric constraints arising from structured water layers at the surface. Diffusion from this alternative adsorption state has a lower energy barrier of ∼0.9 eV, associated with breaking hydrogen bonds along the pathway, in reasonable agreement with the barrier inferred from previous experimental observation of lysozyme surface clustering. These results show the importance of studying protein diffusion alongside adsorption to gain full insight into the formation of protein clusters and films, essential steps in the future development of functionalized surfaces. PMID:23062108

  7. Dissociative adsorption of methane on surface oxide structures of Pd-Pt alloys

    Dianat, Arezoo; Ciacchi, Lucio Colombi; Pompe, Wolfgang; Cuniberti, Gianaurelio; Bobeth, Manfred; 10.1021/jp905689t

    2010-01-01

    The dissociative adsorption of methane on variously oxidized Pd, Pt and Pd-Pt surfaces is investigated using density-functional theory, as a step towards understanding the combustion of methane on these materials. For Pd-Pt alloys, models of surface oxide structures are built on the basis of known oxides on Pd and Pt. The methane adsorption energy presents large variations depending on the oxide structure and composition. Adsorption is endothermic on the bare Pd(111) metal surface as well as on stable thin layer oxide structures such as the ($\\sqrt{5}\\times\\sqrt{5}$) surface oxide on Pd(100) and the PtO$_2$-like oxide on Pt(111). Instead, large adsorption energies are obtained for the (100) surface of bulk PdO, for metastable mixed Pd$_{1-x}$Pt$_x$O$_{4/3}$ oxide layers on Pt(100), and for Pd-Pt(111) surfaces covered with one oxygen monolayer. In the latter case, we find a net thermodynamic preference for a direct conversion of methane to methanol, which remains adsorbed on the oxidized metal substrates via w...

  8. Piezoelectric step-motion actuator

    Mentesana; Charles P.

    2006-10-10

    A step-motion actuator using piezoelectric material to launch a flight mass which, in turn, actuates a drive pawl to progressively engage and drive a toothed wheel or rod to accomplish stepped motion. Thus, the piezoelectric material converts electrical energy into kinetic energy of the mass, and the drive pawl and toothed wheel or rod convert the kinetic energy of the mass into the desired rotary or linear stepped motion. A compression frame may be secured about the piezoelectric element and adapted to pre-compress the piezoelectric material so as to reduce tensile loads thereon. A return spring may be used to return the mass to its resting position against the compression frame or piezoelectric material following launch. Alternative embodiment are possible, including an alternative first embodiment wherein two masses are launched in substantially different directions, and an alternative second embodiment wherein the mass is eliminated in favor of the piezoelectric material launching itself.

  9. Simultaneous metal adsorption on tannin resins

    Vegetable tannin sorbent is evaluated as ion exchange resin using a multitracer study on the adsorption behavior of various elements. Lisiloma latisiliqua L. tannins, polycondensated into spherical pellets were chosen as sorbent resin material. Sorption evaluation of Ce, Cu(II), U(VI), Eu, Fe(III), Th, Nd as representatives of different classes of metal ions were done at different pH values. The distribution ratio of the studied elements was calculated from laboratory experiments. Tannic ion exchange material shows excellent ability for actinides and rare earth elements adsorption from waters. Using radiotracers, the number of catechins subunits involve in each tannin-metal complex was determined. (author)

  10. Adsorption Properties of Chalk Reservoir Materials

    Okhrimenko, Denis

    Understanding adsorption energetics and wetting properties of calcium carbonate surfaces is essential for developing remediation strategies for aquifers, improving oil recovery, minimising risk in CO2 storage and optimising industrial processes. This PhD was focussed on comparing the vapour....../gas adsorption properties of synthetic calcium carbonate phases (calcite, vaterite and aragonite) with chalk, which is composed of biogenic calcite (>98%). In combination with data from nanotechniques, the results demonstrate the complexity of chalk behavior and the role of nanoscale clay particles. The results...

  11. Adsorption on mixtures of ion exchangers

    A theoretical study has been made of adsorption on mixtures of ion exchangers. The effect of variables such as the concentration of the ion being adsorbed, the concentration of the supporting electrolyte, loading, the values of the capacities and equilibrium constants for the various exchange processes, and the fraction of each adsorber in the mixture on the observed distribution coefficient has been investigated. A computer program has been written to facilitate the calculation of distribution coefficients for the adsorption of an ion on a given mixture of ion exchangers under a specified set of conditions

  12. Nicotine adsorption on single wall carbon nanotubes

    Girao, Eduardo C. [Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, Campus do Pici, 60455-900 Fortaleza, Ceara (Brazil); Fagan, Solange B.; Zanella, Ivana [Area de Ciencias Tecnologicas, Centro Universitario Franciscano - UNIFRA, 97010-032 Santa Maria, RS (Brazil); Filho, Antonio G. Souza, E-mail: agsf@fisica.ufc.br [Departamento de Fisica, Universidade Federal do Ceara, Caixa Postal 6030, Campus do Pici, 60455-900 Fortaleza, Ceara (Brazil)

    2010-12-15

    This work reports a theoretical study of nicotine molecules interacting with single wall carbon nanotubes (SWCNTs) through ab initio calculations within the framework of density functional theory (DFT). Different adsorption sites for nicotine on the surface of pristine and defective (8,0) SWCNTs were analyzed and the total energy curves, as a function of molecular position relative to the SWCNT surface, were evaluated. The nicotine adsorption process is found to be energetically favorable and the molecule-nanotube interaction is intermediated by the tri-coordinated nitrogen atom from the nicotine. It is also predicted the possibility of a chemical bonding between nicotine and SWCNT through the di-coordinated nitrogen.

  13. Adsorption Behavior of Plutonium on Clay

    LONG; Hao-qi; BAO; Liang-jin; SONG; Zhi-xin; WANG; Bo

    2013-01-01

    In this study,the adsorption distribution ratios of Pu in the Longdong clays were measured with batch method under hypoxic conditions,and the influence of the liquid-solid ratio and pH on the adsorption distribution ratio also was discussed.The initial concentration of Pu is about 1×10-10 mol/L,and the solution pH value was adjusted with NaOH or HClO4.The temperature of experiments was(30±

  14. Adsorption of amylase enzyme on ultrafiltration membranes

    Beier, Søren; Enevoldsen, Ann Dorrit; Kontogeorgis, Georgios;

    2007-01-01

    A method to measure the static adsorption on membrane surfaces has been developed and described. The static adsorption of an amylase-F has been measured on two different ultrafiltration membranes, both with a cut-off value of 10 kDa (a PES membrane and the ETNA10PP membrane, which is a surface-mo...... cake-layer thickness, which is independent of the membrane type. At higher concentrations of enzyme, concentration polarization effects can not be neglected. Therefore stagnant film theory and the osmotic pressure model can describe the dependency between flux and bulk concentration....

  15. Adsorption Properties of the Cu(115) Surface

    Godowski, P. J.; Groso, A.; Hoffmann, S. V.; Onsgaard, Jens

    2010-01-01

    curve has been confirmed as a very convenient and precise procedure. The adsorbed state of CO at 130 K has been identified by registration of core levels obtained by the use synchrotron radiation photoelectron spectroscopy. The characteristics of the main is and satellite peaks have been analyzed in...... context of substrate geometry and compared with the ones of other copper planes. There are no indications of dissociative adsorption of CO, only residual carbon and oxygen were found after adsorbate desorption around 220 K. CO molecules show a strong tendency to "on top" adsorption in sites far from the...

  16. Step-by-step phacoemulsification training program for ophthalmology residents

    Wang Yulan

    2013-01-01

    Full Text Available Aims: The aim was to analyze the learning curve of phacoemulsification (phaco performed by residents without experience in performing extra-capsular cataract extraction (ECCE in a step-by-step training program (SBSTP. Materials and Methods: Consecutive surgical records of phaco performed from March 2009 to Sept 2011 by four residents without previous ECCE experience were retrospectively reviewed. The completion rate of the first 30 procedures by each resident was calculated. The main intraoperative phaco parameter records for the first 30 surgeries by each resident were compared with those for their last 30 surgeries. Intraoperative complications in the residents′ procedures were also recorded and analyzed. Results: A total of 1013 surgeries were performed by residents. The completion rate for the first 30 phaco procedures was 79.2 μ 5.8%. The main reasons for halting the procedure were as follows: Anterior capsule tear, inability to crack the nucleus, and posterior capsular rupture during phaco or cortex removal. Cumulative dissipated energy of phaco power used during the surgeries was significantly less in the last 30 cases compared with the first 30 cases (30.10 μ 17.58 vs. 55.41 μ 37.59, P = 0.021. Posterior capsular rupture rate was 2.5 μ 1.2% in total (10.8 μ 4.2% in the first 30 cases and 1.7 μ 1.9% in the last 30 cases, P = 0.008; a statistically significant difference. Conclusion:The step-by-step training program might be a necessary process for a resident to transit from dependence to a self-supported operator. It is also an essential middle step between wet lab training to performing the entire phaco procedure on the patient both effectively and safely.

  17. Web design in easy steps

    McManus, Sean

    2011-01-01

    There are millions of websites on the Internet, but most of them fail to make a lasting impression on readers and web surfers. Creating a site that is both appealing and financially remunerative can seem challenging, but this invaluable tool makes the process both simple and fun. As with every book in the popular series of computer books, this one walks readers through every step of the process. From design planning to search engine promotion, each step of the process is thoroughly explained in clear, jargon-free English. Full-color graphics, including numerous screenshots, add further support

  18. Office 2010 in easy steps

    Price, Michael

    2011-01-01

    In easy-to-understand, jargon-free language, Office 2010 in Easy Steps makes the task of learning this new version of Office easy and painless. Covering all the key features, this guide makes it simple to get up and running in no time. Here readers will learn the basics, as well as to master the updated customizable Ribbon, grasp the new Backstage full-screen options, learn how to use the new image and illustration tools, understand new Office web applications, and more. Office 2010 in Easy Steps combs through the new features and covers in detail all the ones that readers will use time and ti

  19. Optimization and Control of Pressure Swing Adsorption Processes Under Uncertainty

    Khajuria, Harish

    2012-03-21

    The real-time periodic performance of a pressure swing adsorption (PSA) system strongly depends on the choice of key decision variables and operational considerations such as processing steps and column pressure temporal profiles, making its design and operation a challenging task. This work presents a detailed optimization-based approach for simultaneously incorporating PSA design, operational, and control aspects under the effect of time variant and invariant disturbances. It is applied to a two-bed, six-step PSA system represented by a rigorous mathematical model, where the key optimization objective is to maximize the expected H2 recovery while achieving a closed loop product H2 purity of 99.99%, for separating 70% H2, 30% CH4 feed. The benefits over sequential design and control approach are shown in terms of closed-loop recovery improvement of more than 3%, while the incorporation of explicit/multiparametric model predictive controllers improves the closed loop performance. © 2012 American Institute of Chemical Engineers (AIChE).

  20. Assessing the adsorption properties of shales

    Pini, Ronny

    2015-04-01

    Physical adsorption refers to the trapping of fluid molecules at near liquid-like densities in the pores of a given adsorbent material. Fine-grained rocks, such as shales, contain a significant amount of nanopores that can significantly contribute to their storage capacity. As a matter of fact, the current ability to extract natural gas that is adsorbed in the rock's matrix is limited, and current technology focuses primarily on the free gas in the fractures (either natural or stimulated), thus leading to recovery efficiencies that are very low. Shales constitute also a great portion of so-called cap-rocks above potential CO2 sequestration sites; hereby, the adsorption process may limit the CO2 mobility within the cap-rock, thus minimizing the impact of leakage on the whole operation. Whether it is an unconventional reservoir or a cap-rock, understanding and quantifying the mechanisms of adsorption in these natural materials is key to improve the engineering design of subsurface operations. Results will be presented from a laboratory study that combines conventional techniques for the measurement of adsorption isotherms with novel methods that allows for the imaging of adsorption using x-rays. Various nanoporous materials are considered, thus including rocks, such as shales and coals, pure clay minerals (a major component in mudrocks) and engineered adsorbents with well-defined nanopore structures, such as zeolites. Supercritical CO2 adsorption isotherms have been measured with a Rubotherm Magnetic Suspension balance by covering the pressure range 0.1-20~MPa. A medical x-ray CT scanner has been used to identify three-dimensional patterns of the adsorption properties of a packed-bed of adsorbent, thus enabling to assess the spatial variability of the adsorption isotherm in heterogeneous materials. The data are analyzed by using thermodynamically rigorous measures of adsorption, such as the net- and excess adsorbed amounts and a recently developed methodology is

  1. Adsorption of doxorubicin on poly(methyl methacrylate)-chitosan-heparin-coated activated carbon beads.

    Miao, Jianjun; Zhang, Fuming; Takieddin, Majde; Mousa, Shaker; Linhardt, Robert J

    2012-03-01

    Extracorporeal filter cartridges, filled with an activated carbon bead (ACB) adsorbent, have been used for removal of overdosed cancer drugs from the blood. Coatings on adsorbent matrices, poly(methyl methacrylate) (PMMA)/activated carbon bead and PMMA/chitosan/heparin/ACB composites, were tested to improve their biocompatibility and blood compatibility. PMMA coating on ACBs was accomplished in a straightforward manner using a PMMA solution in ethyl acetate. A one-step hybrid coating of ACBs with PMMA-anticoagulant heparin required the use of acetone and water co-solvents. Multilayer coatings with three components, PMMA, chitosan, and heparin, involved three steps: PMMA was first coated on ACBs; chitosan was then coated on the PMMA-coated surface; and finally, heparin was covalently attached to the chitosan coating. Surface morphologies were studied by scanning electron microscopy. X-ray photoelectron spectroscopy confirmed the -SO(3)(-) group. Adsorption, of a chemotherapy drug (doxorubicin) from both water and phosphate-buffered saline, by the coated ACBs was examined. The adsorption isotherm curves were fitted using the Freundlich model. The current adsorption system might find potential applications in the removal of high-dose regional chemotherapy drugs while maintaining high efficiency, biocompatibility, and blood compatibility. PMID:22313019

  2. Application of the sanderson polar covalence model to energetics of CO adsorption

    Frese, Karl W.

    1988-08-01

    The model of polar covalence developed by R.T. Sanderson was used to calculate energies of chemisorption of CO g on metal surfaces. Internal energies of adsorption were calculated for four stereochemical possibilities including linear, two site bridge bonded, and dissociated CO on fourteen first, second, and third row transition metals. The influence of surface steps, other defects, and CO-CO interactions were not calculated, although the influence of steps on certain metals is discussed. The effect of metal site coordination number was also calculated. Higher coordination numbers, are generally associated with longer bond lengths and smaller heats of adsorption. Very good agreement, less than 3 kcal mol -1 difference between experiment and calculation, was observed for molecularly adsorbed CO. The enthalpy and Gibbs energy of dissociative adsorption at 298 K were calculated for seventeen transition metals and Si. CO dissociation is thermodynamically allowed on Mn, Cr, Fe, Ni, Re, W and Si at both 10 -10 Torr and 1 atm CO. Dissociation is forbidden on Ru, Rh, Ir, Ag, Pd, Au, and Pt at both pressures. Dissociation is forbidden at 10 -10 Torr, but allowed at 1 atm CO on Co, Cu, Mo, and Os.

  3. Investigation on Adsorption of Lithospermum erythrorhizon onto Fungal Cell Wall Polysaccharides

    孟琴; 薛莲

    2003-01-01

    A culture of Lithosperrnum erythrorhizon adsorbed on fungal cell wall polysaccharides, a novel bioadsorbent made from fungal cell wall, has been established in this paper. Three steps were involved in this immobilization. The first step was preparation of suspended plant cells from tightly aggregated plant cell clumps. The disassembled ratio of 0.715g·g-1 (the disassembled cells over total cells) was obtained under optimum condition for the enzymatic reaction. Then, the adsorption of plant cells onto fungal cell wall polysaccharides was conducted and the saturated capacity of 12g cell per gram of carrier was obtained in adsorption immobilization. Finally, the culture of cells adsorbed on fungal cell wall polysaccharides was compared with that of cells entrapped in alginate or suspension cell culture. While exposed to in situ liquid paraffin extraction coupled with cell culture, the shikonin productivity of immobilized cells by adsorption was 10.67g·L-1, which was 1.8 times of that in suspension culture and 1.5 times of that entrapped in alginate.

  4. The Calculation of Adsorption Isotherms from Chromatographic Peak Shapes

    Neumann, M. G.

    1976-01-01

    Discusses the relationship between adsorption isotherms and elution peak shapes in gas chromatography, and describes a laboratory experiment which involves the adsorption of hexane, cyclohexane, and benzene on alumina at different temperatures. (MLH)

  5. Removal of Pyrethrin from Aqueous Effluents by Adsorptive Micellar Flocculation

    Pardon K. Kuipa

    2015-01-01

    Full Text Available The equilibrium adsorption of pyrethrin onto aggregates formed by the flocculation of micelles of the surfactant sodium dodecyl sulphate (SDS with aluminium sulphate is reported. The experimental results were analysed using different adsorption isotherms (Langmuir, Freundlich, Redlich-Peterson, Sips, Radke-Prausnitz, Temkin, linear equilibrium, and the Dubin-Radushkevich isotherms. The Freundlich and linear equilibrium isotherms best describe the adsorption of pyrethrin onto SDS micellar flocs, with the Freundlich adsorption constant, KF, and the mass distribution coefficient, KD, of 64.266 ((mg/g(L/mg1/n and 119.65 L/g, respectively. Applicability of the Freundlich adsorption model suggests that heterogeneous surface adsorption affects the adsorption. The mean free energy value estimated using the Dubinin-Radushkevich isotherm was 0.136 kJ/mol indicating that physisorption may be predominant in the adsorption process.

  6. Research on the chemical adsorption precursor state of CaCl2-NH3 for adsorption refrigeration

    WANG; Liwei; WANG; Ruzhu; WU; Jingyi; WANG; Kai

    2005-01-01

    As a type of chemical adsorption working pair, the physical adsorption occurs first for CaCl2-NH3 because the effective reaction distance for van der Waals force is longer than that for chemical reaction force, and this physical adsorption state is named the precursor state of chemical adsorption. In order to get the different precursor states of CaCl2-NH3, the different distances between NH3 gas and Ca2+ are realized by the control of different phenomena of swelling and agglomeration in the process of adsorption. When the serious swelling exists while the agglomeration does not exist in the process of adsorption, experimental results show that the activated energy consumed by adsorption reaction increases for the reason of longer distance between Ca2+ and NH3, and at the same time the performance attenuation occurs in the repeated adsorption cycles. When the agglomeration occurs in the process of adsorption, the activated energy for the transition from precursor state to chemical adsorption decreases because the distance between NH3 gas and Ca2+ is shortened by the limited expansion space of adsorbent, and at the same time the performance attenuation does not occur. The adsorption refrigeration isobars are researched by the precursor state of chemical adsorption; results also show that the precursor state is a key factor for isobaric adsorption performance while the distribution of Ca2+ does not influence the permeation of NH3 gas in adsorbent.

  7. Initial steps of aerosol growth

    O. Kulmala

    2004-09-01

    Full Text Available The formation and growth of atmospheric aerosols depend on several steps, namely nucleation, initial steps of growth and subsequent – mainly condensational – growth. This work focuses on the initial steps of growth, meaning the growth right after nucleation, where the interplay of curvature effects and thermodynamics has a significant role on the growth kinetics. More specifically, we investigate how ion clusters and aerosol particles grow from 1.5 nm to 20 nm in atmospheric conditions using experimental data obtained by air ion and aerosol spectrometers. The measurements have been performed at a boreal forest site in Finland. The observed trend that the growth rate seems to increase as a function of size can be used to investigate possible growth mechanisms. Such a growth rate is consistent with a recently suggested nano-Köhler mechanism, in which growth is activated at a certain size with respect to condensation of organic vapors. The results also imply that charge-enhance growth associated with ion-mediated nucleation plays only a minor role in the initial steps of growth, since it would imply a clear decrease of the growth rate with size. Finally, further evidence was obtained on the earlier suggestion that atmospheric nucleation and the subsequent growth of fresh nuclei are likely to be uncoupled phenomena via different participating vapors.

  8. Initial steps of aerosol growth

    M. Kulmala

    2004-01-01

    Full Text Available The formation and growth of atmospheric aerosols depend on several steps, namely nucleation, initial steps of growth and subsequent – mainly condensational – growth. This work focuses on the initial steps of growth, meaning the growth right after nucleation, where the interplay of curvature effects and thermodynamics has a significant role on the growth kinetics. More specifically, we investigate how ion clusters and aerosol particles grow from 1.5 nm to 20 nm (diameter in atmospheric conditions using experimental data obtained by air ion and aerosol spectrometers. The measurements have been performed at a boreal forest site in Finland. The observed trend that the growth rate seems to increase as a function of size can be used to investigate possible growth mechanisms. Such a growth rate is consistent with a recently suggested nano-Köhler mechanism, in which growth is activated at a certain size with respect to condensation of organic vapors. The results also imply that charge-enhanced growth associated with ion-mediated nucleation plays only a minor role in the initial steps of growth, since it would imply a clear decrease of the growth rate with size. Finally, further evidence was obtained on the earlier suggestion that atmospheric nucleation and the subsequent growth of fresh nuclei are likely to be uncoupled phenomena via different participating vapors.

  9. Initial steps of aerosol growth

    Kulmala, M.; Laakso, L.; Lehtinen, K. E. J.; Riipinen, I.; Dal Maso, M.; Anttila, T.; Kerminen, V.-M.; Hõrrak, U.; Vana, M.; Tammet, H.

    2004-12-01

    The formation and growth of atmospheric aerosols depend on several steps, namely nucleation, initial steps of growth and subsequent - mainly condensational - growth. This work focuses on the initial steps of growth, meaning the growth right after nucleation, where the interplay of curvature effects and thermodynamics has a significant role on the growth kinetics. More specifically, we investigate how ion clusters and aerosol particles grow from 1.5 nm to 20 nm (diameter) in atmospheric conditions using experimental data obtained by air ion and aerosol spectrometers. The measurements have been performed at a boreal forest site in Finland. The observed trend that the growth rate seems to increase as a function of size can be used to investigate possible growth mechanisms. Such a growth rate is consistent with a recently suggested nano-Köhler mechanism, in which growth is activated at a certain size with respect to condensation of organic vapors. The results also imply that charge-enhanced growth associated with ion-mediated nucleation plays only a minor role in the initial steps of growth, since it would imply a clear decrease of the growth rate with size. Finally, further evidence was obtained on the earlier suggestion that atmospheric nucleation and the subsequent growth of fresh nuclei are likely to be uncoupled phenomena via different participating vapors.

  10. Theoretical and experimental studies of the recovery of volatile organic compounds from waste air streams in the thermal swing adsorption system with closed-loop regeneration of adsorbent

    Highlights: • The TSA process for VOCs recovery from the waste air was studied. • The closed-loop adsorbent regeneration method was used. • A mathematical model was developed to simulate the TSA process. • The toluene–Sorbonorit 4 activated carbon system was studied. • We proved that toluene can be recovered in moderate condensation temperature range. - Abstract: The cyclic thermal swing adsorption (TSA) process for volatile organic compounds (VOCs) recovery from the waste air is studied theoretically and experimentally. Toluene is chosen as the volatile organic compound. Activated carbon Sorbonorit 4 is used as an adsorbent. The TSA cycle is operated in three steps: an adsorption step with cold feed, a desorption step with hot purge gas and a cooling step with cold inert gas. The desorption and cooling are affected by nitrogen circulated through a heater, an adsorber and a condenser. A nonequilibrium, nonisothermal mathematical model is developed to simulate temperature and concentration breakthrough curves for both adsorption and desorption steps. The computer simulation results are compared with the experimental data. A bench scale fixed bed adsorption unit was used for the experimental study. It is shown that the theoretical model predicts the experimental results well. The computer simulation results are used to study the effect of the purge gas and condensation temperature on the process efficiency

  11. Modeling adsorption of liquid mixtures on porous materials

    Monsalvo, Matias Alfonso; Shapiro, Alexander

    2009-01-01

    of the MPTA onto liquids has been tested on experimental binary and ternary adsorption data. We show that, for the set of experimental data considered in this work, the MPTA model is capable of correlating binary adsorption equilibria. Based on binary adsorption data, the theory can then predict...... ternary adsorption equilibria. Good agreement with the theoretical predictions is achieved in most of the cases. Some limitations of the model are also discussed....

  12. Textural Characterization and Energetics of Porous Solids by Adsorption Calorimetry

    Vanessa Silenia Garcia-Cuello; Moreno-Pirajan, Juan C.; Liliana Giraldo

    2011-01-01

    An adsorption microcalorimeter was designed and built in our laboratory and used for the determination of differential adsorption heats in different samples of porous solids: activated carbon granules, activated carbon pellets, an activated carbon monolith and a zeolite sample. This work shows the relationship between adsorption heat and the pore size of different porous solids using adsorption of NH 3 , CO and N 2 O. The result shows that the thermal effect can be related with textural prope...

  13. Adsorption of copper ions from aqueous solutions on natural zeolite

    Zendelska, Afrodita; Golomeova, Mirjana; Blažev, Krsto; Krstev, Boris; Golomeov, Blagoj; Krstev, Aleksandar

    2015-01-01

    The adsorption of copper ions from synthetic aqueous solutions on natural zeolite (clinoptilolite) was examined. In order to determine the rate of adsorption and the copper uptake at equilibrium, a series of experiments were performed under batch conditions from single ion solutions. Equilibrium data were evaluated based on adsorption (Langmuir and Freundlich) isotherms. The adsorption kinetics is reasonably fast. In the first 20 min of the experiment, approximately 80% of Cu2+ io...

  14. Adsorption of microcystins and anatoxin-a on nanofiltration membranes

    Ribau Teixeira, Margarida; Rosa, Maria João

    2011-01-01

    This work pretends to study the adsorption of microcystin-LR (MC-LR) and anatoxin-a (ATX-a) on nanofiltration membranes and to understand the adsorption behaviour with the solution chemistry (background natural organic matter (NOM) and in the presence of ATX-a). Results demonstrate that MC-LR adsorption increases with water recovery due to the increase in MC-LR feed concentration. MC-LR adsorption is governed by hydrophobic interactions established between the membrane surface and...

  15. Theoretical study of adsorption of lithium atom on carbon nanotube

    Senami, Masato; Ikeda, Yuji; Fukushima, Akinori; Tachibana, Akitomo

    2011-01-01

    We investigate the adsorption of lithium atoms on the surface of the (12,0) single wall carbon nanotube (SWCNT) by using ab initio quantum chemical calculations. The adsorption of one lithium atom on the inside of this SWCNT is favored compared to the outside. We check this feature by charge transfer and regional chemical potential density. The adsorption of multiple lithium atoms on the interior of the SWCNT is studied in terms of adsorption energy and charge transfer. We show that repulsive...

  16. RADICAL FLOW IN POROUS MEDIA WITH DISPERSION AND ADSORPTION

    LIU Ci-qun; GUO Bai-qi; SONG Fu-quan; WANG Jin-ying

    2004-01-01

    The radical transport of chemical concentration in porous media with dispersion and adsorption was studied in this paper. Using Langmuir's adsorption model, the numerical equation of concentration transport was derived. The flows with and without adsorption were simulated and analyzed.Comparison of the obtained solution with the known analytical solution for flow without adsorption shows the presented numerical method is correct and effective, which can be used in reservoir engineering.

  17. Water adsorption in hydrophilic zeolites: experiment and simulation

    Castillo, Juan Manuel; Silvestre Albero, Joaquín; Rodríguez Reinoso, Francisco; Vlugt, Thijs. J. H.; Calero, Sofía

    2013-01-01

    We have measured experimental adsorption isotherms of water in zeolite LTA4A, and studied the regeneration process by performing subsequent adsorption cycles after degassing at different temperatures. We observed incomplete desorption at low temperatures, and cation rearrangement at successive adsorption cycles. We also developed a new molecular simulation force field able to reproduce experimental adsorption isotherms in the range of temperatures between 273 K and 374 K. Small deviations obs...

  18. Adsorption component of the disjoining pressure in thin liquid films

    Tsekov, R.

    2011-01-01

    The disjoining pressure isotherm in foam films is theoretically studied and an important contribution of adsorption is discovered. On the basis of the interfacial thermodynamics an adsorption disjoining pressure component is derived, which is repulsive and exponentially decaying by the film thickness. Expressions for its magnitude and decay length are derived in terms of well-known thermodynamic characteristics such as the partial Gibbs elasticity and adsorption length. Several adsorption iso...

  19. 2-Step IMAT and 2-Step IMRT in three dimensions

    In two dimensions, 2-Step Intensity Modulated Arc Therapy (2-Step IMAT) and 2-Step Intensity Modulated Radiation Therapy (IMRT) were shown to be powerful methods for the optimization of plans with organs at risk (OAR) (partially) surrounded by a target volume (PTV). In three dimensions, some additional boundary conditions have to be considered to establish 2-Step IMAT as an optimization method. A further aim was to create rules for ad hoc adaptations of an IMRT plan to a daily changing PTV-OAR constellation. As a test model, a cylindrically symmetric PTV-OAR combination was used. The centrally placed OAR can adapt arbitrary diameters with different gap widths toward the PTV. Along the rotation axis the OAR diameter can vary, the OAR can even vanish at some axis positions, leaving a circular PTV. The width and weight of the second segment were the free parameters to optimize. The objective function f to minimize was the root of the integral of the squared difference of the dose in the target volume and a reference dose. For the problem, two local minima exist. Therefore, as a secondary criteria, the magnitude of hot and cold spots were taken into account. As a result, the solution with a larger segment width was recommended. From plane to plane for varying radii of PTV and OAR and for different gaps between them, different sets of weights and widths were optimal. Because only one weight for one segment shall be used for all planes (respectively leaf pairs), a strategy for complex three-dimensional (3-D) cases was established to choose a global weight. In a second step, a suitable segment width was chosen, minimizing f for this global weight. The concept was demonstrated in a planning study for a cylindrically symmetric example with a large range of different radii of an OAR along the patient axis. The method is discussed for some classes of tumor/organ at risk combinations. Noncylindrically symmetric cases were treated exemplarily. The product of width and weight of

  20. Adsorption of organic substances to activated carbon

    Adsorption systems using activated carbon as an almost universal adsorbent for organic substances are widely applied for purifying exhaust air. The possibilities, limits and measures for an optimum design of activated carbon processes are given from the point of view of the plant designed and under the aspects of the present laws for environmental control. (orig.)

  1. Adsorption Kinetics in Nanoscale Porous Coordination Polymers

    Nune, Satish K.; Thallapally, Praveen K.; McGrail, Benard Peter; Annapureddy, Harsha V. R.; Dang, Liem X.; Mei, Donghai; Karri, Naveen; Alvine, Kyle J.; Olszta, Matthew J.; Arey, Bruce W.; Dohnalkova, Alice

    2015-10-07

    Nanoscale porous coordination polymers were synthesized using simple wet chemical method. The effect of various polymer surfactants on colloidal stability and shape selectivity was investigated. Our results suggest that the nanoparticles exhibited significantly improved adsorption kinetics compared to bulk crystals due to decreased diffusion path lengths and preferred crystal plane interaction.

  2. Adsorption and desorption of cellulose derivatives.

    Hoogendam, C.W.

    1998-01-01

    Cellulose derivatives, in particular carboxymethyl cellulose (CMC) are used in many (industrial) applications. The aim of this work is to obtain insight into the adsorption mechanism of cellulose derivatives on solid-liquid interfaces.In chapter 1 of this thesis we discuss some appl

  3. Adsorption Phenomena at Organic-Inorganic Interfaces

    Bachmann, M.; Janke, W.

    2007-01-01

    The qualitative solvent- and temperature-dependent conformational behavior of a peptide in the proximity of solid substrates with different adsorption properties is investigated by means of a simple lattice model. The resulting pseudophase diagrams exhibit a complex structure, which can be understood by analysing the minima of the free-energy landscape in dependence of appropriate system parameters.

  4. Radiotracer technique in adsorption study. Pt.7

    The kinetics of adsorption of iodide ions on chromium (IV) oxide has been studied as a function of concentration (10-7-10-2M), temperature (293-328 K) and pH value (3.2-11.2) of the adsorptive solution employing the radiotracer technique. The kinetics of adsorption of iodide ions follows the first order rate law and obeys the Freundlich isotherm. Exposure of the activated oxide adsorbent to neutrons and γ-radiation from a (Ra-Be) neutron source having an integral neutron flux of 3.85 x 106 neutrons/cm2/s and associated with a nominal γ-dose of ca 172 rads/h results in a nominal increase in the rate of uptake for 24 h irradiation and thereafter decreases substantially when the irradiation time is increased to 60 h. The kinetics of desorption of preadsorbed iodide ions on oxide surface in water as well as in potassium iodide solution also follows first order rate law, and amount released increases with the increase of temperature (303-323 K). The adsorption is deduced to be of the ''activated'' type. (author)

  5. Theoretical study of cisplatin adsorption on silica

    Simonetti, S., E-mail: ssimonet@uns.edu.ar [Departamento de Fisica and IFISUR, Universidad Nacional del Sur-CONICET, Av. Alem 1253, 8000 Bahia Blanca (Argentina); Departamentos de Ciencias Basicas e Ingenieria Mecanica, Universidad Tecnologica Nacional, 11 de Abril 461, 8000 Bahia Blanca (Argentina); Company, A. Diaz; Brizuela, G.; Juan, A. [Departamento de Fisica and IFISUR, Universidad Nacional del Sur-CONICET, Av. Alem 1253, 8000 Bahia Blanca (Argentina)

    2011-11-15

    The adsorption of cisplatin and its complexes, cis-[PtCl(NH{sub 3}){sub 2}]{sup +} and cis-[Pt(NH{sub 3}){sub 2}]{sup 2+}, on a SiO{sub 2}(1 1 1) hydrated surface has been studied by the Atom Superposition and Electron Delocalization method. The adiabatic energy curves for the adsorption of the drug and its products on the delivery system were considered. The electronic structure and bonding analysis were also performed. The molecule-surface interactions are formed at expenses of the OH surface bonds. The more important interactions are the Cl-H bond for cis-[PtCl{sub 2}(NH{sub 3}){sub 2}] and cis-[PtCl(NH{sub 3}){sub 2}]{sup +} adsorptions, and the Pt-O interaction for cis-[Pt(NH{sub 3}){sub 2}]{sup 2+} adsorption. The Cl p orbitals and Pt s, p y d orbitals of the molecule and its complexes, and the s H orbital and, the s and p orbitals of the O atoms of the hydrated surface are the main contribution to the surface bonds.

  6. Exhaustively sampling peptide adsorption with metadynamics.

    Deighan, Michael; Pfaendtner, Jim

    2013-06-25

    Simulating the adsorption of a peptide or protein and obtaining quantitative estimates of thermodynamic observables remains challenging for many reasons. One reason is the dearth of molecular scale experimental data available for validating such computational models. We also lack simulation methodologies that effectively address the dual challenges of simulating protein adsorption: overcoming strong surface binding and sampling conformational changes. Unbiased classical simulations do not address either of these challenges. Previous attempts that apply enhanced sampling generally focus on only one of the two issues, leaving the other to chance or brute force computing. To improve our ability to accurately resolve adsorbed protein orientation and conformational states, we have applied the Parallel Tempering Metadynamics in the Well-Tempered Ensemble (PTMetaD-WTE) method to several explicitly solvated protein/surface systems. We simulated the adsorption behavior of two peptides, LKα14 and LKβ15, onto two self-assembled monolayer (SAM) surfaces with carboxyl and methyl terminal functionalities. PTMetaD-WTE proved effective at achieving rapid convergence of the simulations, whose results elucidated different aspects of peptide adsorption including: binding free energies, side chain orientations, and preferred conformations. We investigated how specific molecular features of the surface/protein interface change the shape of the multidimensional peptide binding free energy landscape. Additionally, we compared our enhanced sampling technique with umbrella sampling and also evaluated three commonly used molecular dynamics force fields. PMID:23706011

  7. Adsorption of metals by immobilized tannins

    Simultaneous adsorption of thorium, europium, cerium, and neodymium by immobilized tannic was studied at different ph values. Tannic materials have excellent ability to adsorb selectively thorium at pH 5. The rest of the elements could be isolated in group at pH 7

  8. Adsorption of Nitrogen on Organized Mesoporous Alumina

    Čejka, Jiří; Veselá, Lenka; Rathouský, Jiří; Zukal, Arnošt

    Amsterdam : Elsevier, 2002 - (Sayari, A.; Jaroniec, M.), s. 429-436 - ( Studies in Surface Science and Catalysis.. 141). [International Symposium on Nanoporous Materials /3./. Ottawa (CA), 12.06.2002-15.06.2002] R&D Projects: GA MŠk ME 404 Institutional research plan: CEZ:AV0Z4040901 Keywords : alumina * nitrogen * adsorption Subject RIV: CF - Physical ; Theoretical Chemistry

  9. BSA adsorption on bimodal PEO brushes

    Bosker, W.T.E.; Iakovlev, P.A.; Norde, W.; Cohen Stuart, M.A.

    2005-01-01

    BSA adsorption onto bimodal PEO brushes at a solid surface was measured using optical reflectometry. Bimodal brushes consist of long (N=770) and short (N=48) PEO chains and were prepared on PS surfaces, applying mixtures of PS 29-PEO48 and PS37-PEO770 block copolymers and using the Langmuir-Blodgett

  10. BSA adsorption on bimodal PEO brushes

    Bosker, WTE; Iakovlev, PA; Norde, W; Stuart, MAC

    2005-01-01

    BSA adsorption onto bimodal PEO brushes at a solid surface was measured using optical reflectometry. Bimodal brushes consist of long (N = 770) and short (N = 48) PEO chains and were prepared on PS surfaces, applying mixtures of PS29-PEO48 and PS37-PEO770 block copolymers and using the Langmuir-Blodg

  11. Characterization and ciprofloxacin adsorption properties of activated carbons prepared from biomass wastes by H3PO4 activation.

    Sun, Yuanyuan; Li, Hong; Li, Guangci; Gao, Baoyu; Yue, Qinyan; Li, Xuebing

    2016-10-01

    As biomass wastes, Arundo donax Linn and pomelo peel were used as precursors for activated carbons (ALAC and PPAC) preparation by phosphoric acid activation. The pore structure and surface acidic functional groups of both carbons were characterized by nitrogen adsorption/desorption experiment, NH3-temperature-programmed desorption (NH3-TPD) and Fourier transform infrared spectroscopy (FTIR). A batch of experiments was carried out to investigate the adsorption performances of ciprofloxacin under different conditions. Results showed that PPAC exhibited larger surface area (1252m(2)/g) and larger portion of mesoporous, while ALAC was typical of microporous materials. Results from NH3-TPD suggested that ALAC was characteristic of more acidic functional group than PPAC. The maximum monolayer adsorption capability was 244mg/g for ALAC and 400mg/L for PPAC. Kinetics studies showed intra-particle diffusion was not the unique rate-controlling step. Boundary layer resistance existed between adsorbent and adsorbate. PMID:27034157

  12. Insights on finite size effects in Ab-initio study of CO adsorption and dissociation on Fe 110 surface

    Chakrabarty, Aurab; Mousseau, Normand; Becquart, Charlotte S; Mellouhi, Fadwa El

    2016-01-01

    Adsorption and dissociation of hydrocarbons on metallic surfaces represent crucial steps to carburization of metal. Here, we use density functional theory total energy calculations with the climbing-image nudged elastic band method to estimate the adsorption energies and dissociation barriers for different CO coverages with surface supercells of different sizes. For the absorption of CO, the contribution from van der Waals interaction in the computation of adsorption parameters is found important in small systems with high CO-coverages. The dissociation process involves carbon insertion into the Fe surface causing a lattice deformation that requires a larger surface system for unrestricted relaxation. We show that, in larger surface systems associated with dilute CO-coverages, the dissociation barrier is significantly decreased. The elastic deformation of the surface is generic and can potentially applicable for all similar metal-hydrocarbon reactions and therefore a dilute coverage is necessary for the simul...

  13. Adsorption characteristics and heat of adsorption measurements of R-134a on activated carbon

    Saha, Bidyut B. [Mechanical Engineering Department, National University of Singapore, 10 Kent Ridge Crescent (Singapore); Habib, Khairul; Koyama, Shigeru [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga-shi, Fukuoka 816-8580 (Japan); El-Sharkawy, Ibrahim I. [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga-shi, Fukuoka 816-8580 (Japan); Mechanical Power Engineering Department, Faculty of Engineering, Mansoura University, El-Mansoura (Egypt)

    2009-11-15

    This paper presents adsorption isotherms of R-134a (HFC-134a) on highly porous pitch based activated carbon (Maxsorb III) in the temperature range of 5-70 C and pressures up to 12 bar, using desorption method. The experimental data have been fitted with the Dubinin-Astakhov (D-A) isotherm equation. The adsorption isotherms of R-134a on Maxsorb III obtained from the present study are compared with the adsorption isotherm results of R-134a on similar type of adsorbents obtained by other researchers and they are found to be fairly consistent. The isosteric heat of adsorption of the assorted adsorbent-refrigerant pair has also been extracted from the present experimental data. (author)

  14. Water adsorption on the Be(0001) surface:from monomer to trimer adsorption

    Ning Hua; Tao Xiang-Ming; Tan Ming-Qiu

    2012-01-01

    In this paper,the density functional theory has been used to perform a comparative theoretical study of water monomer,dimer,trimer,and bilayer adsorptions on the Be(0001) surface. In our calculations,the adsorbed water molecules are energetically favoured adsorbed on the atop sites,and the dimer adsorption is found to be the most stable with a peak adsorption energy of ~ 437 meV.Further analyses have revealed that the essential bonding interaction between the water monomer and the metal substrate is the hybridization of the water 3a1-like molecular orbital with the (s,pz) orbitals of the surface beryllium atoms.While in the case of the water dimer adsorption,the lb1-like orbital of the H2O molecule plays a dominant role.

  15. The adsorption of HCl on volcanic ash

    Gutiérrez, Xochilt; Schiavi, Federica; Keppler, Hans

    2016-03-01

    Understanding the interaction between volcanic gases and ash is important to derive gas compositions from ash leachates and to constrain the environmental impact of eruptions. Volcanic HCl could potentially damage the ozone layer, but it is unclear what fraction of HCl actually reaches the stratosphere. The adsorption of HCl on volcanic ash was therefore studied from -76 to +150 °C to simulate the behavior of HCl in the dilute parts of a volcanic plume. Finely ground synthetic glasses of andesitic, dacitic, and rhyolitic composition as well as a natural obsidian from Vulcano (Italy) served as proxies for fresh natural ash. HCl adsorption is an irreversible process and appears to increase with the total alkali content of the glass. Adsorption kinetics follow a first order law with rate constants of 2.13 ṡ10-6 s-1 to 1.80 ṡ10-4 s-1 in the temperature range investigated. For dacitic composition, the temperature and pressure dependence of adsorption can be described by the equation ln ⁡ c = 1.26 + 0.27 ln ⁡ p - 715.3 / T, where c is the surface concentration of adsorbed HCl in mg/m2, T is temperature in Kelvin, and p is the partial pressure of HCl in mbar. A comparison of this model with a large data set for the composition of volcanic ash suggests that adsorption of HCl from the gas phase at relatively low temperatures can quantitatively account for the majority of the observed Cl concentrations. The model implies that adsorption of HCl on ash increases with temperature, probably because of the increasing number of accessible adsorption sites. This temperature dependence is opposite to that observed for SO2, so that HCl and SO2 are fractionated by the adsorption process and the fractionation factor changes by four orders of magnitude over a temperature range of 250 K. The assumption of equal adsorption of different species is therefore not appropriate for deriving volcanic gas compositions from analyses of adsorbates on ash. However, with the experimental

  16. Monte Carlo Simulation for the Adsorption of Symmetric Triblock Copolymers

    彭昌军; 李健康; 刘洪来; 胡英

    2004-01-01

    The adsorption behavior of symmetric triblock copolymers, Am/2BnAm/2, from a nonselective solvent at solid-liquid interface has been studied by Monte Carlo simulations on a simple lattice model. Either segment A or segment B is attractive, while the other is non-attractive to the surface. Influences of the adsorption energy,bulk concentration, chain composition and chain length on the microstructure of adsorbed layers are presented.The results show that the total surface coverage and the adsorption amount increases monotonically as the bulk concentration increases. The larger the adsorption energy and the higher the fraction of adsorbing segments, the higher the total surface coverage is exhibited. The product of surface coverage and the proportion of non-attractive segments are nearly independent of the chain length, and the logarithm of the adsorption amount is a linear function of the reciprocal of the reduced temperature. When the adsorption energy is larger, the adsorption amount exhibits a maximum as the fraction of adsorbing segment increases. The adsorption isotherms of copolymers with different length of non-attractive segments can be mapped onto a single curve under given adsorption energy. The adsorption layer thickness decreases as the adsorption energy and the fraction of adsorbing segments increases, but it increhses as the length of non-attractive segments increases. The tails mainly govern the adsorption layer thickness.

  17. Visualizing Gas Adsorption on Porous Solids: Four Simple, Effective Demonstrations

    Cheung, Ocean

    2014-01-01

    Gas adsorption on porous solids is a topic that is often discussed in an undergraduate chemistry or chemical engineering course. The idea of porosity and gas adsorption on a porous solid is usually discussed with adsorption isotherms recorded using commercially available equipment. This discussion can be rather abstract and can be difficult for…

  18. Ordering kinetics in model systems with inhibited interfacial adsorption

    Willart, J.-F.; Mouritsen, Ole G.; Naudts, J.; Descamps, M.

    1992-01-01

    The ordering kinetics in two-dimensional Ising-like spin moels with inhibited interfacial adsorption are studied by computer-simulation calculations. The inhibited interfacial adsorption is modeled by a particular interfacial adsorption condition on the structure of the domain wall between...

  19. Influence of adsorption properties on radionuclide transport in fractured rock

    Most models predicting radionuclide transport in fractured rock include mechanisms of advection, dispersion, radioactive decay, and equilibrium adsorption between the solid and liquid phases. Recently, nonequilibrium adsorption has been given a great deal of attention. In this paper, the authors have successfully derived the analytical solutions to transport equations for a single fracture under various conditions covering no sorption, nonequilibrium adsorption, and equilibrium sorption

  20. Polyglycidyl methacrylate based immunoaffinity cryogels for insulin adsorption

    Immunoaffinity chromatography (IAC) is a kind of bioaffinity chromatography which used antibodies or antibody-related molecules as the stationary phase. IAC is used by many applications for analytical, clinical and diagnostic purposes, particularly preferring in analytical purposes on one-step separation and purification of target compounds. Moreover, immunoaffinity chromatography is used in antibody enrichment and separation of cells. IAC columns are usually applied in the antibody experiments due to powerful and selective binding of antibodies and/or their target antigens. Antigen or antibody molecules could be immobilized to the solid support. Therefore, target antibody or cell is purified. Specific bioligands can be immobilized directly on glycidyl based polymeric material with simple acid–base catalyst. In this study, polyglycidyl methacrylate based therefore cryogels were prepared and anti-insulin antibodies were immobilized on porous surface of cryogels. Swelling test, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and scanning electron microscopy (SEM) were conducted to characterize cryogels developed. To optimize separation conditions, effects of pH, initial insulin concentration, flow rate, salt concentration, contact time and temperature on insulin adsorption capacity were examined. The results indicated that the immunoaffinity cryogel developed here could be classified as good alternative with prominent properties such as high reusability and cost-friendly adsorbent and would be one of the primary reports for immunoaffinity purification of insulin molecules in not only lab-scale but also for industrial purposes. - Highlights: • Polyglycidyl methacrylate based cryogels developed as stationary phase • Immunoaffinity cryogels for reusable and cost-friendly insulin adsorption • Increase in worldwide prevalence of diabetes, type 1 or 2 • An exponential increase in the demand on insulin market • Guiding researchers for not

  1. Polyglycidyl methacrylate based immunoaffinity cryogels for insulin adsorption

    Memmedova, Türkan; Armutcu, Canan; Uzun, Lokman, E-mail: lokman@hacettepe.edu.tr; Denizli, Adil

    2015-07-01

    Immunoaffinity chromatography (IAC) is a kind of bioaffinity chromatography which used antibodies or antibody-related molecules as the stationary phase. IAC is used by many applications for analytical, clinical and diagnostic purposes, particularly preferring in analytical purposes on one-step separation and purification of target compounds. Moreover, immunoaffinity chromatography is used in antibody enrichment and separation of cells. IAC columns are usually applied in the antibody experiments due to powerful and selective binding of antibodies and/or their target antigens. Antigen or antibody molecules could be immobilized to the solid support. Therefore, target antibody or cell is purified. Specific bioligands can be immobilized directly on glycidyl based polymeric material with simple acid–base catalyst. In this study, polyglycidyl methacrylate based therefore cryogels were prepared and anti-insulin antibodies were immobilized on porous surface of cryogels. Swelling test, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and scanning electron microscopy (SEM) were conducted to characterize cryogels developed. To optimize separation conditions, effects of pH, initial insulin concentration, flow rate, salt concentration, contact time and temperature on insulin adsorption capacity were examined. The results indicated that the immunoaffinity cryogel developed here could be classified as good alternative with prominent properties such as high reusability and cost-friendly adsorbent and would be one of the primary reports for immunoaffinity purification of insulin molecules in not only lab-scale but also for industrial purposes. - Highlights: • Polyglycidyl methacrylate based cryogels developed as stationary phase • Immunoaffinity cryogels for reusable and cost-friendly insulin adsorption • Increase in worldwide prevalence of diabetes, type 1 or 2 • An exponential increase in the demand on insulin market • Guiding researchers for not

  2. Adsorption Model for Off-Gas Separation

    Veronica J. Rutledge

    2011-03-01

    The absence of industrial scale nuclear fuel reprocessing in the U.S. has precluded the necessary driver for developing the advanced simulation capability now prevalent in so many other countries. Thus, it is essential to model complex series of unit operations to simulate, understand, and predict inherent transient behavior and feedback loops. A capability of accurately simulating the dynamic behavior of advanced fuel cycle separation processes will provide substantial cost savings and many technical benefits. The specific fuel cycle separation process discussed in this report is the off-gas treatment system. The off-gas separation consists of a series of scrubbers and adsorption beds to capture constituents of interest. Dynamic models are being developed to simulate each unit operation involved so each unit operation can be used as a stand-alone model and in series with multiple others. Currently, an adsorption model has been developed in gPROMS software. Inputs include gas stream constituents, sorbent, and column properties, equilibrium and kinetic data, and inlet conditions. It models dispersed plug flow in a packed bed under non-isothermal and non-isobaric conditions for a multiple component gas stream. The simulation outputs component concentrations along the column length as a function of time from which the breakthrough data is obtained. It also outputs temperature along the column length as a function of time and pressure drop along the column length. Experimental data will be input into the adsorption model to develop a model specific for iodine adsorption on silver mordenite as well as model(s) specific for krypton and xenon adsorption. The model will be validated with experimental breakthrough curves. Another future off-gas modeling goal is to develop a model for the unit operation absorption. The off-gas models will be made available via the server or web for evaluation by customers.

  3. Adsorption Model for Off-Gas Separation

    The absence of industrial scale nuclear fuel reprocessing in the U.S. has precluded the necessary driver for developing the advanced simulation capability now prevalent in so many other countries. Thus, it is essential to model complex series of unit operations to simulate, understand, and predict inherent transient behavior and feedback loops. A capability of accurately simulating the dynamic behavior of advanced fuel cycle separation processes will provide substantial cost savings and many technical benefits. The specific fuel cycle separation process discussed in this report is the off-gas treatment system. The off-gas separation consists of a series of scrubbers and adsorption beds to capture constituents of interest. Dynamic models are being developed to simulate each unit operation involved so each unit operation can be used as a stand-alone model and in series with multiple others. Currently, an adsorption model has been developed in gPROMS software. Inputs include gas stream constituents, sorbent, and column properties, equilibrium and kinetic data, and inlet conditions. It models dispersed plug flow in a packed bed under non-isothermal and non-isobaric conditions for a multiple component gas stream. The simulation outputs component concentrations along the column length as a function of time from which the breakthrough data is obtained. It also outputs temperature along the column length as a function of time and pressure drop along the column length. Experimental data will be input into the adsorption model to develop a model specific for iodine adsorption on silver mordenite as well as model(s) specific for krypton and xenon adsorption. The model will be validated with experimental breakthrough curves. Another future off-gas modeling goal is to develop a model for the unit operation absorption. The off-gas models will be made available via the server or web for evaluation by customers.

  4. 300 Area Uranium Leach and Adsorption Project

    The objective of this study was to measure the leaching and adsorption characteristics of uranium in six near-surface sediment samples collected from the 300 Area of the Hanford Site. Scanning electron micrographs of the samples showed that the uranium contamination in the sediments is most likely present as co-precipitates and/or discrete uranium particles. Molecular probe techniques also confirm the presence of crystalline discrete uranium bearing phases. In all cases, the uranium is present as oxidized uranium (uranyl [U(VI)]). Results from the column leach tests showed that uranium leaching did not follow a constant solubility paradigm. Four of the five contaminated sediments showed a large near instantaneous release of a few percent of the total uranium followed by a slower continual release. Steady-state uranium leachate concentrations were never measured and leaching characteristics and trends were not consistent among the samples. Dissolution kinetics were slow, and the measured leach curves most likely represent a slow kinetically controlled desorption or dissolution paradigm. Batch adsorption experiments were performed to investigate the effect of pH and uranium and carbonate solution concentrations on uranium adsorption onto the uncontaminated sediment. Uranium adsorption Kd values ranged from 0 to > 100 ml/g depending on which solution parameter was being adjusted. Results of the experiments showed that carbonate solution concentration has the greatest impact on uranium adsorption in the 300 Area. Solution pH was shown to be important in laboratory tests; however, the sediment will dominate the field pH and minimize its overall effect in the 300 Area sediments. Results also showed that uranium sorption onto the background sediment is linear up to uranium concentrations of 3 mg/L, well above the values found in the upper unconfined aquifer. Therefore, the linear Kd model is defensible in predicting the fate of uranium in the 300 Area aquifer

  5. One step synthesis of polyacrylamide functionalized graphene and its application in Pb(II) removal

    Highlights: • PAM-g-graphene is synthesized by the co-irradiation between GO and AM monomers. • PAM graft on GO has led to the exfoliation of GO into individual sheets. • The γ-ray induced reduction of GO. • PAM-g-graphene exhibits high adsorption capacities toward Pb(II) ions. • PAM-g-graphene provides a new idea for heavy metal pollutants’ removal in water. - Abstract: Polyacrylamide grafted graphene (PAM-g-graphene) from graphite oxide (GO) was successfully prepared by γ-ray irradiation with acrylamide monomers in aqueous at room temperature in this paper. Our strategy involves the PAM chains graft on the surface and between the layers of GO by in situ radical polymerization which led to the exfoliation of GO into individual sheets. Results show that the degree of grafting of PAM-g-graphene samples is 24.2%, and the thickness is measured to be 2.59 nm. Moreover, the as-prepared PAM-g-graphene with some amino from PAM and little oxygen functional groups exhibit superior adsorption of Pb(II) ions. The adsorption processes reach equilibrium in just 30 min and the adsorption isotherms are described well by Langmuir and Freundlich classical isotherms models. The determined adsorption capacity of PAM-g-graphene is 819.67 mg g−1 (pH 6) for Pb(II), which is 20 times and 8 times capacities of that for graphene nanosheets and carbon nanotubes according to reports, respectively. This chemically modified graphene synthesized by this fast one-step approach, featuring a good versatility and adaptability, excellent adsorption capacity and rapid extraction, may provide a new idea for the global problem of heavy metal pollutants’ removal in water

  6. One step synthesis of polyacrylamide functionalized graphene and its application in Pb(II) removal

    Xu, Zhiwei; Zhang, Yaoyao; Qian, Xiaoming; Shi, Jie; Chen, Lei; Li, Baodong; Niu, Jiarong; Liu, Liangsen, E-mail: 83019163@163.com

    2014-10-15

    Highlights: • PAM-g-graphene is synthesized by the co-irradiation between GO and AM monomers. • PAM graft on GO has led to the exfoliation of GO into individual sheets. • The γ-ray induced reduction of GO. • PAM-g-graphene exhibits high adsorption capacities toward Pb(II) ions. • PAM-g-graphene provides a new idea for heavy metal pollutants’ removal in water. - Abstract: Polyacrylamide grafted graphene (PAM-g-graphene) from graphite oxide (GO) was successfully prepared by γ-ray irradiation with acrylamide monomers in aqueous at room temperature in this paper. Our strategy involves the PAM chains graft on the surface and between the layers of GO by in situ radical polymerization which led to the exfoliation of GO into individual sheets. Results show that the degree of grafting of PAM-g-graphene samples is 24.2%, and the thickness is measured to be 2.59 nm. Moreover, the as-prepared PAM-g-graphene with some amino from PAM and little oxygen functional groups exhibit superior adsorption of Pb(II) ions. The adsorption processes reach equilibrium in just 30 min and the adsorption isotherms are described well by Langmuir and Freundlich classical isotherms models. The determined adsorption capacity of PAM-g-graphene is 819.67 mg g{sup −1} (pH 6) for Pb(II), which is 20 times and 8 times capacities of that for graphene nanosheets and carbon nanotubes according to reports, respectively. This chemically modified graphene synthesized by this fast one-step approach, featuring a good versatility and adaptability, excellent adsorption capacity and rapid extraction, may provide a new idea for the global problem of heavy metal pollutants’ removal in water.

  7. Synthesis and uranium adsorption performance of a novel modified lignin-based adsorbent

    The modified lignin-based adsorbent containing the strong-base and weak-base group, was prepared by two-step chemical modification of acid-precipitation lignin, which is low-cost, and abundant renewable natural polymers: (1) introduced weak-base group by mannich reaction; (2)introduced strong-base group by O-alkylatio reaction.The adsorbent was characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and Elementary Analysis(EA), which demonstrated amino group was successfully introduced into the lignin. In order to assess the possibility of adsorption effect, the adsorption experiments of uranium on lignin-based adsorbent, were carried out in the static mode at room temperature. The removal rate of uranium of the wastewatere could reach 93%, under such conditions as pH value 2, uranium concentration 6 mg/L, and adsorbent dosage 10 g/L, etc. (authors)

  8. Synthesis and uranium adsorption performance of a novel modified lignin-based adsorbent

    The modified lignin-based adsorbent containing the strong-base and weak-base group, was prepared by two-step chemical modification of acid-precipitation lignin, which is a low-cost and abundant renewable natural polymer: 1) weak-base group introduced by Mannich reaction; 2) strong-base group introduced by O-alkylation reaction. The adsorbent was characterized by Fourier transform infrared spectroscopy (FT-IR) and elementary analysis (EA), which demonstrated amino group was successfully introduced into the lignin. In order to assess the adsorption effect, the uranium adsorption experiments of lignin-based adsorbent were carried out in the static mode at room temperature. The removal rate of uranium from the wastewater could reach 93% under such conditions as pH value 2, uranium concentration 6 mg/L, adsorbent dosage 10 g/L etc. (authors)

  9. Kinetics of oxygen adsorption on ZnS nanoparticles synthesized by precipitation process

    Ahmadi Reza

    2016-06-01

    Full Text Available ZnS nanoparticles were synthesized through a one-step precipitation process. Effect of time and temperature on the formation reaction was investigated. The synthesized samples were characterized by X-ray diffraction (XRD, ultraviolet (UV visible absorption and photoluminescence (PL spectrophotometry. Based on XRD and UV-Vis data, the particles produced at 70 °C had a mean particle size of about 5 nm. Increasing time and temperature of the synthesis reaction resulted in photoluminescence intensification. PL spectroscopy helped understanding the adsorption kinetics of oxygen on ZnS nanoparticles during the precipitation synthesis process. Fabrication of ZnS structures with appropriate oxygen adsorption capacity was suggested as a means of PL emission intensity control.

  10. Porosity and adsorption properties of activated carbon derived from palm oil waste

    Activated carbon have extensively been used as adsorbents in industry for the removal of pollutant species from gases for the purpose of purification and recovery of chemicals. The adsorption properties of the carbons depend very much on the porosity and type of pore presents which can be generated and controlled during synthesis and activation steps. This paper reports the effect of chemical activation by ZnCl3, KOH and nh4OH on the porosity of carbon produced from palm oil industry waste. Type of pores will further be validated by the SEM micrograph. The amount of gas adsorbed, the adsorption capacities can also be estimated based on the BET experiments data. The applicability of the produced carbon materials for the removal and exchange of hazardous incinerator gas is discussed. (Author)

  11. Synthesis and uranium adsorption performance of a novel modified lign in-based adsorbent

    A novel modified lignin-based adsorbent containing the strong-base and weak-base group was prepared by two-steps chemical modification method using acid-precipitation lignin, which is low-cost and abundant renewable natural polymers: (1) introduced weak-base group by Mannich reaction; (2)introduced strong-base group by O-alkylation reaction. The adsorbent was characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and Elementary Analysis (EA). The results indicated that two kinds of amino group were successfully introduced into the lignin structure. In order to assess its adsorption effect for uranyl, the adsorption experiments were carried out in the static mode at room temperature using a low-concentration uranium aqueous solution. The removal rate of uranium could reach 93%, under such conditions as pH value 2, uranium concentration 1-10 mg/L, and adsorbent dosage 10 g/L etc. (authors)

  12. Improving catalytic selectivity through control of adsorption orientation

    Pang, Simon H.

    monolayer formed by 1,2-benzenedithiol, we determined that hydrodeoxygenation selectively occurred on catalyst particle steps and edges from an upright structure, whereas decarbonylation occurred on particle terraces from a flat-lying structure. Control of furfural adsorption orientation was also achieved through the use of NiCu bimetallic catalysts. The aromatic furan ring was repelled from surface Cu, leading to an upright structure. However, under hydrogenation conditions, Ni tended to be near the surface of thin films and catalysts, leading to less dramatic selectivity enhancement. The presence of a 1-octadecanethiol monolayer kinetically stabilized the surface termination, allowing Cu to remain at the surface.

  13. Adsorption of ammonium dinitramide (ADN) from aqueous solutions. 1. Adsorption on powdered activated charcoal.

    Santhosh, G; Venkatachalam, S; Ninan, K N; Sadhana, R; Alwan, S; Abarna, V; Joseph, M A

    2003-03-17

    Investigations on the adsorption of ammonium dinitramide (NH(4)N(NO(2))(2)) (ADN) from aqueous solutions on powdered activated charcoal (PAC) were carried out in order to find out an effective and easier method of separating ADN from aqueous solutions. The effectiveness of PAC in the selective adsorption of ADN from aqueous solutions of ADN (ADN-F) and ADN in presence of sulfate (SO(4)(2-)) and nitrate (NO(3)(-)) ions (ADN-PS) was examined and compared using batch and column methods. The adsorption process follows both Langmuir and Freundlich adsorption isotherms and the isotherm parameters for the models were determined. The observed data favor the formation of monolayer adsorption. The adsorption capacities were found to be 63.3, 119, 105.3 and 82 mg of ADN per g of PAC for ADN-F (batch), ADN-PS (batch), ADN-F (column) and ADN-PS (column), respectively. Break-through curves for ADN-F and ADN-PS were obtained for the optimization of separation of ADN from aqueous solutions. Elution curves were generated for the desorption of ADN from PAC using hot water as eluent. PMID:12628781

  14. Phosphate adsorption on aluminum-coordinated functionalized macroporous–mesoporous silica: Surface structure and adsorption behavior

    Graphical abstract: - Highlights: • Al-coordinated functionalized macroporous–mesoporous silica for phosphate removal. • It had the maximum adsorption capacity of 23.59 mg P/g. • Over 95% of the final adsorption capacity reached in the first 1 min. - Abstract: In this study, Al(III)-coordinated diamino-functionalized macroporous–mesoporous silica was synthesized and characterized by X-ray diffraction, N2 adsorption–desorption, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy. Because of well-defined and interconnecting macroporous–mesoporous networks, the resulting adsorbent (MM-SBA) exhibited a significantly better phosphate adsorption performance and faster removal rate, as compared with the mesoporous adsorbent (M-SBA). Based on the Freundlich and Langmuir models, the phosphate adsorption capacity and the maximum adsorption capacity of MM-SBA were 7.99 mg P/g and 23.59 mg P/g, respectively. In the kinetic study of MM-SBA, over 95% of its final adsorption capacity reached in the first 1 min; whereas that of M-SBA was less than 79%

  15. Phosphate adsorption on aluminum-coordinated functionalized macroporous–mesoporous silica: Surface structure and adsorption behavior

    Huang, Weiya [Department of Chemistry, Jinan University, Guangzhou 510632 (China); Department of Materials Science and Engineering, Taizhou University, Linhai 317000 (China); Li, Dan [Environmetal Engineering, School of Engineering and Information Technology, Murdoch University, Murdoch, Western Australia 6150 (Australia); Zhu, Yi; Xu, Kai; Li, Jianqiang [Department of Chemistry, Jinan University, Guangzhou 510632 (China); Han, Boping [Institute of Hydrobiology, Jinan University, Guangzhou 510460 (China); Zhang, Yuanming, E-mail: tzhangym@jnu.edu.cn [Department of Chemistry, Jinan University, Guangzhou 510632 (China)

    2013-12-15

    Graphical abstract: - Highlights: • Al-coordinated functionalized macroporous–mesoporous silica for phosphate removal. • It had the maximum adsorption capacity of 23.59 mg P/g. • Over 95% of the final adsorption capacity reached in the first 1 min. - Abstract: In this study, Al(III)-coordinated diamino-functionalized macroporous–mesoporous silica was synthesized and characterized by X-ray diffraction, N{sub 2} adsorption–desorption, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy. Because of well-defined and interconnecting macroporous–mesoporous networks, the resulting adsorbent (MM-SBA) exhibited a significantly better phosphate adsorption performance and faster removal rate, as compared with the mesoporous adsorbent (M-SBA). Based on the Freundlich and Langmuir models, the phosphate adsorption capacity and the maximum adsorption capacity of MM-SBA were 7.99 mg P/g and 23.59 mg P/g, respectively. In the kinetic study of MM-SBA, over 95% of its final adsorption capacity reached in the first 1 min; whereas that of M-SBA was less than 79%.

  16. The dissimilar twins a comparative, site-selective in situ study of CO adsorption and desorption on Pt(3 2 2) and Pt(3 5 5)

    Tränkenschuh, B.; Papp, C.; Fuhrmann, T.; Denecke, R.; Steinrück, H.-P.

    2007-02-01

    The adsorption and desorption of CO on stepped Pt(3 2 2) = Pt(S)-[5(1 1 1) × (1 0 0)] and Pt(3 5 5) = Pt(S)-[5(1 1 1) × (1 1 1)] were investigated using in situ high-resolution X-ray photoelectron spectroscopy at BESSY II, which allows to clearly distinguish between different step and terrace adsorption sites. For the two surfaces, with the same nominal terrace width of five atomic rows, but different step orientation, significant differences are observed. While for Pt(3 5 5) CO adsorption at steps only occurs at on-top sites, on Pt(3 2 2) both step on-top and bridge sites are occupied, albeit with a significantly lower coverage (0.07 vs. 0.13 ML at 200 K). On both surfaces terrace sites are only occupied when the step sites are almost saturated confirming the enhanced binding energy at step sites. CO adsorbed at the (1 1 1) steps on Pt(3 5 5) is more strongly bound than on the (1 0 0) steps on Pt(3 2 2), which is attributed to the different electronic and geometric structure of the steps. The relative occupation of terrace and step sites at a given coverage remains the same between 120 and 290 K on Pt(3 5 5) K, but shows major changes on Pt(3 2 2), between step on-top and bridge sites as well as terrace on-top and bridge sites. On Pt(3 5 5) a smaller CO terrace coverage is found (0.36 vs. 0.40 ML on Pt(3 2 2) at 200 K), mainly due to the lower occupation of terrace bridge sites. For Pt(3 2 2), an ordered adsorbate phase is deduced from a c(4 × 2)-like LEED pattern, which indicates adsorbate order beyond the extension of a single terrace. A model for this structure is proposed.

  17. Stepping Out: An Overview of the STEP Curriculum. Secondary Transition and Employment Project: STEP.

    Baumgart, Diane; Anderson, Jane

    The guide, developed by the Secondary Transition and Employment Project (STEP) in Idaho, provides an overview of its sequential vocational curriculum intended to help students with mild, moderate, and severe handicaps to: (1) identify their vocational preferences and aptitudes; (2) use community resources to find out about jobs; (3) observe and…

  18. The computational study of adsorption of carbon monoxide on pristine and Ge-doped (6,0 zigzag models of BNNTs

    Mahdi Rezaei Sameti

    2014-07-01

    Full Text Available The aim of this research is studying the effects of Ge-doped on CO adsorption on the outer and inner surfaces of (6, 0 zigzag model of boron nitride nanotube (BNNTs by using DFT theory. For this purpose, eight models of CO adsorption on the surfaces of BNNTs are considered. At first step, all structures were optimized at B3LYP and 6-31G (d standard base set and then the electronic structure, adsorption energy, HOMO - LUMO orbitals, gap energy, quantum molecular descriptors, and NQR parameters were determined. The bond lengths neighborhood sites of Ge-doped of BNNTs at all models were increased and the bond angles decreased. The small ad-sorption energy value and large interaction distance show that the adsorption of CO on BNNTs is weakly physical adsorption due to weak Van der Waals interaction. Our calculated results show that the adsorption of CO on the surface of undoped models is more favorable than Ge-doped models. The NQR parameters of the first layer in all the models are larger than those other layers.

  19. Effect of copper stress on growth characteristics and fermentation properties of Saccharomyces cerevisiae and the pathway of copper adsorption during wine fermentation.

    Sun, Xiangyu; Liu, Lingling; Zhao, Yu; Ma, Tingting; Zhao, Fang; Huang, Weidong; Zhan, Jicheng

    2016-02-01

    The effect of copper stress on the fermentation performance of Saccharomyces cerevisiae and its copper adsorption pathway during alcoholic fermentation were investigated in this study. At the limits imposed by the regulations of the European Union and South African (⩽ 20 mg/l), copper had no effect on the cell growth of S. cerevisiae, but its fermentation performance was inhibited to a certain extent. Therefore, the regulated limit should be further reduced (⩽ 12.8 mg/l). Under 9.6-19.2 mg/l copper stress, S. cerevisiae could absorb copper; the copper removal ratio and the unit strain adsorption were 60-81% and 2.72-9.65 mg/g, respectively. S. cerevisiae has a non-biological adsorption of copper, but compared with biological (living yeast) adsorption, the non-biological adsorption was very low. The copper adsorption way of S. cerevisiae was primarily via biological (living yeast) adsorption, which was a two-step process. PMID:26304318

  20. Improvement of soluble coffee aroma using an integrated process of supercritical CO2 extraction with selective removal of the pungent volatiles by adsorption on activates carbon

    S. Lucas

    2006-06-01

    Full Text Available In this paper a two-step integrated process consisting of CO2 supercritical extraction of volatile coffee compounds (the most valuable from roasted and milled coffee, and a subsequent step of selective removal of pungent volatiles by adsorption on activated carbon is presented. Some experiments were carried out with key compounds from roasted coffee aroma in order to study the adsorption step: ethyl acetate as a desirable compound and furfural as a pungent component. Operational parameters such as adsorption pressure and temperature and CO2 flowrate were optimized. Experiments were conducted at adsorption pressures of 12-17 MPa, adsorption temperatures of 35-50ºC and a solvent flow rate of 3-5 kg/h. In all cases, the solute concentration and the activated particle size were kept constant. Results show that low pressures (12 MPa, low temperatures (35ºC and low CO2 flowrates (3 kg/h are suitable for removing the undesirable pungent and smell components (e.g. furfural and retaining the desirable aroma compounds (e.g. ethyl acetate. The later operation with real roasted coffee has corroborated the previous results obtained with the key compounds.

  1. Tungsten oxide – fly ash oxide composites in adsorption and photocatalysis

    Visa, Maria, E-mail: maria.visa@unitbv.ro; Bogatu, Cristina, E-mail: cristina.bogatu@unitbv.ro; Duta, Anca, E-mail: a.duta@unitbv.ro

    2015-05-30

    Highlights: • A novel fly ash – WO{sub 3} composite was synthesized via mild hydrothermal treatment. • Simultaneous dyes and copper adsorption efficiently runs on the composite. • In situ tandem systems (TiO{sub 2}–WO{sub 3}) supports the high photocatalytic activity. • The processes kinetics mainly depend on the dye’s structure and flexibility. • Thermodynamics depend on the copper–dye/copper–dye-substrate interactions. - Abstract: A novel composite based on tungsten oxide and fly ash was hydrothermally synthetized to be used as substrate in the advanced treatment of wastewaters with complex load resulted from the textile industry. The proposed treatment consists of one single step process combining photocatalysis and adsorption. The composite’s crystalline structure was investigated by X-ray diffraction and FTIR, while atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to analyze the morphology. The adsorption capacity and photocatalytic properties of the material were tested on mono- and multi-pollutants systems containing two dyes (Bemacid Blau – BB and Bemacid Rot – BR) and one heavy metal ion-Cu{sup 2+}, and the optimized process conditions were identified. The results indicate better removal efficiencies using the novel composite material in the combined adsorption and photocatalysis, as compared to the separated processes. Dyes removal was significantly enhanced in the photocatalytic process by adding hydrogen peroxide and the mechanism was presented and discussed. The pseudo second order kinetics model best fitted the experimental data, both in the adsorption and in the combined processes. The kinetic parameters were calculated and correlated with the properties of the composite substrate.

  2. Synthesis of Fe3O4/Polyacrylonitrile Composite Electrospun Nanofiber Mat for Effective Adsorption of Tetracycline.

    Liu, Qing; Zhong, Lu-Bin; Zhao, Quan-Bao; Frear, Craig; Zheng, Yu-Ming

    2015-07-15

    Novel Fe3O4/polyacrylonitrile (PAN) composite nanofibers (NFs) were prepared by a simple two-step process, an electrospinning and solvothermal method. Characterization by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) demonstrated formation of a uniform nanoparticles coating (about 20 nm in thickness) on the PAN nanofiber backbone. The coating was constructed by well-crystallized cubic phase Fe3O4 nanoparticles as examined by X-ray diffraction spectroscopy (XRD). The coating doubled the specific surface area of NFs, from 8.4 to 17.8 m2 g(-1), as confirmed by nitrogen sorption isotherm analysis. To evaluate the feasibility of Fe3O4/PAN composite NFs as a potential adsorbent for antibiotic removal, batch adsorption experiments were conducted using tetracycline (TC) as the model antibiotic molecule. The results showed that Fe3O4/PAN composite NFs were effective in removing TC with no impactful loss of Fe in the pH regime of environmental interest (5-8). The adsorption of TC onto Fe3O4/PAN composite NFs better fitted the pseudo-second-order kinetics model, and the maximum adsorption capacity calculated from Langmuir isotherm model was 257.07 mg g(-1) at pH 6. The composite NFs also exhibited good regenerability over repeated adsorption/desorption cycles. Surface complexation between TC and the composite NFs contributed most to the adsorption as elucidated by X-ray photoelectron spectroscopy (XPS). This highly effective and novel adsorbent can be easily modularized and separated, promising its huge potential in drinking and wastewater treatment for antibiotic removal. PMID:26079116

  3. Tungsten oxide – fly ash oxide composites in adsorption and photocatalysis

    Highlights: • A novel fly ash – WO3 composite was synthesized via mild hydrothermal treatment. • Simultaneous dyes and copper adsorption efficiently runs on the composite. • In situ tandem systems (TiO2–WO3) supports the high photocatalytic activity. • The processes kinetics mainly depend on the dye’s structure and flexibility. • Thermodynamics depend on the copper–dye/copper–dye-substrate interactions. - Abstract: A novel composite based on tungsten oxide and fly ash was hydrothermally synthetized to be used as substrate in the advanced treatment of wastewaters with complex load resulted from the textile industry. The proposed treatment consists of one single step process combining photocatalysis and adsorption. The composite’s crystalline structure was investigated by X-ray diffraction and FTIR, while atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to analyze the morphology. The adsorption capacity and photocatalytic properties of the material were tested on mono- and multi-pollutants systems containing two dyes (Bemacid Blau – BB and Bemacid Rot – BR) and one heavy metal ion-Cu2+, and the optimized process conditions were identified. The results indicate better removal efficiencies using the novel composite material in the combined adsorption and photocatalysis, as compared to the separated processes. Dyes removal was significantly enhanced in the photocatalytic process by adding hydrogen peroxide and the mechanism was presented and discussed. The pseudo second order kinetics model best fitted the experimental data, both in the adsorption and in the combined processes. The kinetic parameters were calculated and correlated with the properties of the composite substrate

  4. Peripheral DSA with automated stepping

    Peripheral digital angiography can now be applied with automated stepping to evaluate the complete lower extremity, with one single injection of contrast medium. In general, good-quality images have been obtained. In some cases, a stationary run had to be carried out with a digital subtraction angiographic (DSA) technique. The authors report a further improvement of this method: it allows angiographic evaluation of the complete lower extremity with DSA technique after a single contrast medium injection of 60 mL. Altogether, 25 examinations were evaluated and compared with results of the nonsubtracted technique. With the DSA-technique, additional series could be reduced to only those where significant differences in flow between the extremities necessitated different timing, as known from conventional angiography as well. In conclusion, the use of DSA technique with automated stepping may totally replace conventional angiography of the peripheral arteries

  5. The mass transfer dynamics of gaseous methyl-iodide adsorption by silver-exchanged sodium mordenite

    The adsorption of methyl iodide onto hydrogen-reduced silver-exchange mordenite was studied. The removal of organic iodides from off-gas streams is an important step in controlling the release of radioactive iodine to the environment during the treatment of radioactive wastes or the processing of some irradiated materials. Nine well accepted mass transfer models were evaluated for their ability to adequately explain the observed CH3I uptake behavior onto the Ag-Z. Linear and multidimensional regression techniques were utilized in the estimation of the diffusion constants and other model parameters which then permitted the selection of an appropriate mass transfer model. To date, only bulk loading data exist for the adsorption of CH3I onto Ag-Z. Hence this is believed to be the first study to quantify the controlling mass transfer mechanisms of this process. It can be concluded from the analysis of the experimental data obtained by the single-pellet type experiments and for the process conditions used in this study that the overall mass transfer rate associated with the adsorption of CH3I onto Ag-Z is affected by both micropore and macropore diffusion. The macropore diffusion rate was significantly faster than the micropore diffusion, resulting in a two-step adsorption behavior which was adequately modeled by a bimodal pore distribution model. The micropore diffusivity was determined to be on the order of 2 x 10-14 cm2/s. The system was also shown to be isothermal under all conditions of this study. Two other conclusions were also obtained. First, the gas film resistance to mass transfer for the 1/16 and 1/8-in.-diam Ag-Z pellets can be ignored under the conditions used in this study. Finally, it was shown that by decreasing the water vapor content of the feed gas, the chemical reaction rate appeared to become the initial rate-limiting factor for the mass transfer. 75 refs

  6. Practical design of stepped columns

    Girao Coelho, A.M.; Simao, P.D.; Bijlaard, F.S.K.

    2012-01-01

    This paper deals with buckling aspects of the design of stepped columns in heavy mill buildings. In these structures, columns have to carry significant axial loads that usually act eccentrically and strength reducing bending moments due to lateral loads. A simple physical model for buckling behaviour analysis is proposed and formulated using the differential equations of equilibrium. The exact solution of the governing equations is found by using symbolic computation. Effective buckling lengt...

  7. Visual Basic in easy steps

    McGrath, Mike

    2011-01-01

    Visual Basic in Easy Steps begins by describing the installation process, then introduces form controls, application properties, the programming language, and problem-solving techniques. It illustrates how to build and deploy a complete Windows application and how to create macros for Microsoft Office and web pages for Internet Explorer. By the end of this book, readers will have gained a sound understanding of Visual Basic - even without previous knowledge of programming languate - and be able to create their own interactive applications.

  8. Kyoto Protocol one step closer

    Showstack, Randy

    The European Union (EU) could soon decide to ratify the Kyoto Protocol on climate change, following a 4 March meeting of the European Commissions environment council to approve the treaty.European Commission President Romani Prodi said the council's move enables the 15 EU member states to take the steps toward simultaneous ratification together with the commission before 1 June."I urge our partners both in the developed and in the developing countries to also ratify the Kyoto Protocol soon," he said.

  9. First Steps for New Government

    2006-01-01

    The formation of a unity government brings hopes of peace and stability to war-torn Iraq, though violence continues Thirty-eight months after the war on Iraq began, and after five months of wrangling over cabinet posts, a new national government led by Nuri al-Maliki was sworn in, marking a great step in the country's post-war reconstruction but one on a road that appears to be growing ever longer and rockier.

  10. Phase stepping in Lau interferometry

    Ángel-Toro, Luciano; Tebaldi, Myrian; Henao, Rodrigo

    1999-01-01

    The implementation of phase shifting interferometry to analyze the Lau interferometric fringe patterns is proposed. The fundamentals of this application are theoretically discussed and the basis of the phase map interpretation is outlined. The three steps algorithm is used to depict the phase maps of lens-like test objects and an application for measuring focal lengths of lenses is reported. Experimental results are presented. q1999 Elsevier Science B.V. All rights reserved.

  11. In-induced stable ordering of stepped Si(553) surface

    Highlights: • Control growth of In on step Si(553) & thermal stability of novel superstructure. • Influence of temperature on growth modes (SK,VB) under different growth conditions. • In-induced superstructure: (8 × 2), (8 × 4), mixed (553)-7 × 1 + (111)√3 × √3R30° phases. - Abstract: The growth mechanism and adsorbate-induced surface morphology of metal atoms on semiconducting surfaces crucially determines the electronic and physicochemical properties of these metal/semiconductor systems. In this study, we investigate the kinetically controlled growth of indium (In) atoms on the high index stepped Si(553)-7 × 7 surface and the thermal stability of various novel In-induced superstructural phases formed during adsorption/desorption process. Auger electron spectroscopy analysis reveals that In adsorption at room temperature (RT) and at 350 °C, with a controlled incident flux of 0.0016 ML/s, proceeds in the Stranski–Krastanov growth mode where two dimensional (2D)/three dimensional (3D) islands are formed on top of two complete monolayers. At higher substrate temperature up to 450 °C, the growth of In atoms occurs in the form of islands on the bare Si(553) surface, and In coverage is limited to the sub-monolayer regime. During the thermal desorption of the RT grown In/Si(553) system, the In clusters rearrange themselves and an unusual “cluster to layer” transformation occurs on top of the stable monolayer. In situ low energy electron diffraction analysis during adsorption and desorption shows the development of various coverage and temperature dependent In-induced superstructural phases on Si(553) surface, such as: (8 × 2) after annealing at 520 °C with coverage 0.5 ML, (8 × 4) after annealing at 580 °C (∼1 ML coverage) and (553)-7 × 1 + (111)-√3 × √3-R30° at 0.3 ML (630 °C). These adsorbate-induced superstructural phases could potentially be utilized as templates for pattern assisted growth of various exotic 1D/2D structures for

  12. In-induced stable ordering of stepped Si(553) surface

    Chauhan, Amit Kumar Singh [Physics of Energy Harvesting, (CSIR-NPL) , Dr. K.S. KrishnanRoad, New Delhi -110012 (India); Department of Physics, JMI, New Delhi 110025 (India); Niazi, Asad; Nair, Lekha [Department of Physics, JMI, New Delhi 110025 (India); Gupta, Govind, E-mail: govind@nplindia.org [Physics of Energy Harvesting, (CSIR-NPL) , Dr. K.S. KrishnanRoad, New Delhi -110012 (India)

    2015-05-15

    Highlights: • Control growth of In on step Si(553) & thermal stability of novel superstructure. • Influence of temperature on growth modes (SK,VB) under different growth conditions. • In-induced superstructure: (8 × 2), (8 × 4), mixed (553)-7 × 1 + (111)√3 × √3R30° phases. - Abstract: The growth mechanism and adsorbate-induced surface morphology of metal atoms on semiconducting surfaces crucially determines the electronic and physicochemical properties of these metal/semiconductor systems. In this study, we investigate the kinetically controlled growth of indium (In) atoms on the high index stepped Si(553)-7 × 7 surface and the thermal stability of various novel In-induced superstructural phases formed during adsorption/desorption process. Auger electron spectroscopy analysis reveals that In adsorption at room temperature (RT) and at 350 °C, with a controlled incident flux of 0.0016 ML/s, proceeds in the Stranski–Krastanov growth mode where two dimensional (2D)/three dimensional (3D) islands are formed on top of two complete monolayers. At higher substrate temperature up to 450 °C, the growth of In atoms occurs in the form of islands on the bare Si(553) surface, and In coverage is limited to the sub-monolayer regime. During the thermal desorption of the RT grown In/Si(553) system, the In clusters rearrange themselves and an unusual “cluster to layer” transformation occurs on top of the stable monolayer. In situ low energy electron diffraction analysis during adsorption and desorption shows the development of various coverage and temperature dependent In-induced superstructural phases on Si(553) surface, such as: (8 × 2) after annealing at 520 °C with coverage 0.5 ML, (8 × 4) after annealing at 580 °C (∼1 ML coverage) and (553)-7 × 1 + (111)-√3 × √3-R30° at 0.3 ML (630 °C). These adsorbate-induced superstructural phases could potentially be utilized as templates for pattern assisted growth of various exotic 1D/2D structures for

  13. Adsorption of Cu(II), Co(II), and Ni(II) ions by modified magnetic chitosan chelating resin

    Monier, M., E-mail: monierchem@yahoo.com [Department of Chemistry, Drexel University, Philadelphia, PA (United States); Chemistry Department, Faculty of Science, Mansoura University, Mansoura (Egypt); Ayad, D.M. [Chemistry Department, Faculty of Science, Mansoura University, Mansoura (Egypt); Wei, Y., E-mail: weiyen@drexel.edu [Department of Chemistry, Drexel University, Philadelphia, PA (United States); Sarhan, A.A. [Chemistry Department, Faculty of Science, Mansoura University, Mansoura (Egypt)

    2010-05-15

    Cross-linked magnetic chitosan-isatin Schiff's base resin (CSIS) was prepared for adsorption of metal ions. CSIS obtained was investigated by means of FTIR, {sup 1}H NMR, wide-angle X-ray diffraction (WAXRD), magnetic properties and thermogravimetric analysis (TGA). The adsorption properties of cross-linked magnetic CSIS resin toward Cu{sup 2+}, Co{sup 2+} and Ni{sup 2+} ions were evaluated. Various factors affecting the uptake behavior such as contact time, temperature, pH and initial concentration of the metal ions were investigated. The kinetic parameters were evaluated utilizing the pseudo-first-order and pseudo-second-order. The equilibrium data were analyzed using the Langmuir, Freundlich, and Tempkin isotherm models. The adsorption kinetics followed the mechanism of the pseudo-second-order equation for all systems studied, evidencing chemical sorption as the rate-limiting step of adsorption mechanism and not involving a mass transfer in solution. The best interpretation for the equilibrium data was given by Langmuir isotherm, and the maximum adsorption capacities were 103.16, 53.51, and 40.15 mg/g for Cu{sup 2+}, Co{sup 2+} and Ni{sup 2+} ions, respectively. Cross-linked magnetic CSIS displayed higher adsorption capacity for Cu{sup 2+} in all pH ranges studied. The adsorption capacity of the metal ions decreased with increasing temperature. The metal ion-loaded cross-linked magnetic CSIS were regenerated with an efficiency of greater than 88% using 0.01-0.1 M ethylendiamine tetraacetic acid (EDTA).

  14. Intensification of adsorption process by using the pyrolytic char from waste tires to remove chromium(Ⅵ) from wastewater

    ZHOU Jie; YANG Yong-rong

    2004-01-01

    Pyrolysis has the potential of transforming waste into valuable recyclable products. Pyrolytic char(PC) is one of the most important products from the pyrolysis of used tires. One of the most significant applications for pyrolytic char recovered is used for the removal of Cr(Ⅵ) in the wastewater effluent to control waste by waste. The surface chemistry properties of surface element distribution / concentration and chemical structure were examined for the pyrolytic char and the commercial activated carbon(CAC) respectively. The results showed that surfaces of PC possesses a large amount of ester and hydrocarbon graft, whereas there are mainly carbon functional components of C-OH, C=O and COOH on the surface of CAC. Therefore the surface electronegativity of PC is lower than that of CAC in the water. The repulsive interactions between the surfaces of PC and the negatively charged Cr(Ⅵ) ion are weaker than that of CAC, which results in an intensification of the adsorption process by the utilization of PC. The adsorption isotherms of Cr(Ⅵ) ion on the two kinds of carbons were determined experimentally. The larger adsorption amount on the PC in the case of Cr(Ⅵ) may be attributed mainly to its special surface micro-chemical environment. The mechanism of the removal Cr(Ⅵ) from aqueous solution was assumed to be the integration of adsorption and redox reaction. The adsorption was the rate-controlled step for Cr(Ⅵ) removal. The adsorption of Cr(Ⅵ) has been identified as pseudo-second- order kinetics. The rate constants of adsorption have been evaluated.

  15. Using mathematical models to understand the effect of nanoscale roughness on protein adsorption for improving medical devices

    Ercan B

    2013-09-01

    Full Text Available Batur Ercan,1 Dongwoo Khang,2 Joseph Carpenter,3 Thomas J Webster1 1Department of Chemical Engineering, Northeastern University, Boston, MA, USA; 2School of Materials Science and Engineering and Center for PRC and RIGET, Gyeongsang National University, Jinju, South Korea; 3School of Medicine, Stanford University, Stanford, CA, USA Abstract: Surface roughness and energy significantly influence protein adsorption on to biomaterials, which, in turn, controls select cellular adhesion to determine the success and longevity of an implant. To understand these relationships at a fundamental level, a model was originally proposed by Khang et al to correlate nanoscale surface properties (specifically, nanoscale roughness and energy to protein adsorption, which explained the greater cellular responses on nanostructured surfaces commonly reported in the literature today. To test this model for different surfaces from what was previously used to develop that model, in this study we synthesized highly ordered poly(lactic-co-glycolic acid surfaces of identical chemistry but altered nanoscale surface roughness and energy using poly(dimethylsiloxane molds of polystyrene beads. Fibronectin and collagen type IV adsorption studies showed a linear adsorption behavior as the surface nanoroughness increased. This supported the general trends observed by Khang et al. However, when fitting such data to the mathematical model established by Khang et al, a strong correlation did not result. Thus, this study demonstrated that the equation proposed by Khang et al to predict protein adsorption should be modified to accommodate for additional nanoscale surface property contributions (ie, surface charge to make the model more accurate. In summary, results from this study provided an important step in developing future mathematical models that can correlate surface properties (such as nanoscale roughness and surface energy to initial protein adsorption events important to

  16. Adsorption characteristics of nano-TiO2 onto zebrafish embryos and its impacts on egg hatching.

    Shih, Yu-Jen; Su, Chia-Chi; Chen, Chiu-Wen; Dong, Cheng-Di; Liu, Wen-Sheng; Huang, C P

    2016-07-01

    The characteristics of nanoparticles (NPs) uptake may fundamentally alter physicochemical effects of engineered NPs on aquatic organisms, thereby yielding different ecotoxicology assessment results. The adsorption behavior of nano-TiO2 (P-25) on zebrafish embryos in Holtfreter's medium (pH 7.2, I ∼ 7.2 × 10(-2) M) and the presence of sodium alginate (100 mg/L) as dispersant was investigated. Zebrafish embryos (total 100) were exposed to nano-TiO2 at different concentrations (e.g., 0, 10, 20, 60, 120 mg/L) in batch-mode assay. The adsorption capacity of nano-TiO2 on fish eggs was determined by measuring the Ti concentration on the egg surface using ICP-OES analysis. Results showed that the adsorption capacity increased rapidly in the first hour, and then declined to reach equilibrium in 8 h. The adsorption characteristics was visualized as a three-step process of rapid initial layer formation, followed by break-up of aggregates and finally rearrangement of floc structures; the maximum adsorption capacity was the sum of an inner rigid layers of aggregates of 0.81-0.84 μg-TiO2/#-egg and an outer softly flocculated layers of 1.01 μg-TiO2/#-egg. The Gibbs free energy was 543.29-551.26 and 100.75 kJ/mol, respectively, for the inner-layer and the outer-layer aggregates. Adsorption capacity at 0.5-1.0 μg-TiO2/#-egg promoted egg hatching; but hatching was inhibited at higher adsorption capacity. Results clearly showed that the configuration of TiO2 aggregates could impact the hatching efficiency of zebrafish embryos. PMID:27043376

  17. Insights on finite size effects in ab initio study of CO adsorption and dissociation on Fe 110 surface

    Chakrabarty, Aurab; Bouhali, Othmane; Mousseau, Normand; Becquart, Charlotte S.; El-Mellouhi, Fedwa

    2016-08-01

    Adsorption and dissociation of hydrocarbons on metallic surfaces represent crucial steps on the path to carburization, eventually leading to dusting corrosion. While adsorption of CO molecules on Fe surface is a barrier-less exothermic process, this is not the case for the dissociation of CO into C and O adatoms and the diffusion of C beneath the surface that are found to be associated with large energy barriers. In practice, these barriers can be affected by numerous factors that combine to favour the CO-Fe reaction such as the abundance of CO and other hydrocarbons as well as the presence of structural defects. From a numerical point of view, studying these factors is challenging and a step-by-step approach is necessary to assess, in particular, the influence of the finite box size on the reaction parameters for adsorption and dissociation of CO on metal surfaces. Here, we use density functional theory (DFT) total energy calculations with the climbing-image nudged elastic band method to estimate the adsorption energies and dissociation barriers for different CO coverages with surface supercells of different sizes. We further compute the effect of periodic boundary condition for DFT calculations and find that the contribution from van der Waals interaction in the computation of adsorption parameters is important as they contribute to correcting the finite-size error in small systems. The dissociation process involves carbon insertion into the Fe surface causing a lattice deformation that requires a larger surface system for unrestricted relaxation. We show that, in the larger surface systems associated with dilute CO-coverages, C-insertion is energetically more favourable, leading to a significant decrease in the dissociation barrier. This observation suggests that a large surface system with dilute coverage is necessary for all similar metal-hydrocarbon reactions in order to study their fundamental electronic mechanisms, as an isolated phenomenon, free from

  18. Protein adsorption on materials surfaces with nano-topography

    2007-01-01

    Protein adsorption behavior on the surfaces of biomedical materials is highly related to the biocompatibility of the materials. In the past, numerous research reports were mainly focused on the effect of chemical components of a material's surface on protein adsorption. The effect of surface topography on protein adsorption, the topic of this review, has recently receuvedkeen interest. The influence of surface nano-topographic factors, including roughness, curvature and geometry, on protein adsorption as well as the protein adsorption behavior, such as the amount of protein adsorbed, the activity and morphology of adsorbed protein, is introduced.

  19. Adsorption dynamics and equilibrium studies of Zn (II) onto chitosan

    G Karthikeyan; K Anbalagan; N Muthulakshmi Andal

    2004-03-01

    Batch equilibration studies are conducted to determine the nature of adsorption of zinc (II) over chitosan. The factors affecting the adsorption process like particle size, contact time, dosage, pH, effects of chloride and nitrate are identified. The influence of temperature and co-ions on the adsorption process is verified. The fraction of adsorption, and the intraparticle diffusion rate constant, are calculated at different environments and the results are discussed. The nature of adsorption of the zinc (II) - chitosan system is explained using Freundlich, Langmuir isotherms and thermodynamic parameters.

  20. Enhanced adsorptive removal of p-nitrophenol from water by aluminum metal–organic framework/reduced graphene oxide composite

    Wu, Zhibin; Yuan, Xingzhong; Zhong, Hua; Wang, Hou; Zeng, Guangming; Chen, Xiaohong; Wang, Hui; Zhang, Lei; Shao, Jianguang

    2016-05-01

    In this study, the composite of aluminum metal–organic framework MIL-68(Al) and reduced graphene oxide (MA/RG) was synthesized via a one–step solvothermal method, and their performances for p–nitrophenol (PNP) adsorption from aqueous solution were systematically investigated. The introduction of reduced graphene oxide (RG) into MIL-68(Al) (MA) significantly changes the morphologies of the MA and increases the surface area. The MA/RG-15% prepared at RG-to-MA mass ratio of 15% shows a PNP uptake rate 64% and 123% higher than MIL-68(Al) and reduced graphene oxide (RG), respectively. The hydrogen bond and π – π dispersion were considered to be the major driving force for the spontaneous and endothermic adsorption process for PNP removal. The adsorption kinetics, which was controlled by film–diffusion and intra–particle diffusion, was greatly influenced by solution pH, ionic strength, temperature and initial PNP concentration. The adsorption kinetics and isotherms can be well delineated using pseudo–second–order and Langmuir equations, respectively. The presence of phenol or isomeric nitrophenols in the solution had minimal influence on PNP adsorption by reusable MA/RG composite.

  1. Enhanced adsorptive removal of p-nitrophenol from water by aluminum metal–organic framework/reduced graphene oxide composite

    Wu, Zhibin; Yuan, Xingzhong; Zhong, Hua; Wang, Hou; Zeng, Guangming; Chen, Xiaohong; Wang, Hui; zhang, Lei; Shao, Jianguang

    2016-01-01

    In this study, the composite of aluminum metal–organic framework MIL-68(Al) and reduced graphene oxide (MA/RG) was synthesized via a one–step solvothermal method, and their performances for p–nitrophenol (PNP) adsorption from aqueous solution were systematically investigated. The introduction of reduced graphene oxide (RG) into MIL-68(Al) (MA) significantly changes the morphologies of the MA and increases the surface area. The MA/RG-15% prepared at RG-to-MA mass ratio of 15% shows a PNP uptake rate 64% and 123% higher than MIL-68(Al) and reduced graphene oxide (RG), respectively. The hydrogen bond and π – π dispersion were considered to be the major driving force for the spontaneous and endothermic adsorption process for PNP removal. The adsorption kinetics, which was controlled by film–diffusion and intra–particle diffusion, was greatly influenced by solution pH, ionic strength, temperature and initial PNP concentration. The adsorption kinetics and isotherms can be well delineated using pseudo–second–order and Langmuir equations, respectively. The presence of phenol or isomeric nitrophenols in the solution had minimal influence on PNP adsorption by reusable MA/RG composite. PMID:27181188

  2. Enhanced adsorptive removal of p-nitrophenol from water by aluminum metal-organic framework/reduced graphene oxide composite.

    Wu, Zhibin; Yuan, Xingzhong; Zhong, Hua; Wang, Hou; Zeng, Guangming; Chen, Xiaohong; Wang, Hui; Zhang, Lei; Shao, Jianguang

    2016-01-01

    In this study, the composite of aluminum metal-organic framework MIL-68(Al) and reduced graphene oxide (MA/RG) was synthesized via a one-step solvothermal method, and their performances for p-nitrophenol (PNP) adsorption from aqueous solution were systematically investigated. The introduction of reduced graphene oxide (RG) into MIL-68(Al) (MA) significantly changes the morphologies of the MA and increases the surface area. The MA/RG-15% prepared at RG-to-MA mass ratio of 15% shows a PNP uptake rate 64% and 123% higher than MIL-68(Al) and reduced graphene oxide (RG), respectively. The hydrogen bond and π - π dispersion were considered to be the major driving force for the spontaneous and endothermic adsorption process for PNP removal. The adsorption kinetics, which was controlled by film-diffusion and intra-particle diffusion, was greatly influenced by solution pH, ionic strength, temperature and initial PNP concentration. The adsorption kinetics and isotherms can be well delineated using pseudo-second-order and Langmuir equations, respectively. The presence of phenol or isomeric nitrophenols in the solution had minimal influence on PNP adsorption by reusable MA/RG composite. PMID:27181188

  3. Step-By-Step: Life Cycle Radioactive Waste Management

    Radioactive waste is an unavoidable by-product when nuclear technologies are used for electricity production and for beneficial practices in medicine, agriculture, research and industry. When the radioactivity of the waste is above a certain threshold, the waste requires special disposal methods. Through extensive research, standards and approaches have been developed for safely and securely preparing for and managing radioactive waste disposal. In the course of its journey from the point of generation to disposal, radioactive waste undergoes a number of predisposal management treatment steps to transform it into a safe, stable and manageable form suitable for transport, storage and disposal

  4. Adsorption study of anionic reactive dye from aqueous solution to Mg-Fe-CO{sub 3} layered double hydroxide (LDH)

    Ahmed, I.M., E-mail: ismawy@yahoo.ca [Hot Labs Centre, Atomic Energy Authority, P. Code 13759, Cairo (Egypt); Gasser, M.S. [Hot Labs Centre, Atomic Energy Authority, P. Code 13759, Cairo (Egypt)

    2012-10-15

    Graphical abstract: Second order kinetic model for adsorption of congo red onto Mg-Fe-LDH. Highlights: Black-Right-Pointing-Pointer Mg-Fe-CO{sub 3}-LDH was utilized as an adsorbent. Black-Right-Pointing-Pointer It was used for the removal of congo red (CR), an anionic dye from aqueous solution. Black-Right-Pointing-Pointer The adsorption of (CR) is endothermic. Black-Right-Pointing-Pointer The adsorption equilibrium was well described by the Langmuir isotherm model. Black-Right-Pointing-Pointer Adsorption kinetics of (CR) was found to conform to pseudo-second order model. - Abstract: Mg-Fe-Cl Layered double hydroxides (LDHs) have been prepared using a method involving separate nucleation and aging steps with Mg/Fe = 3. The interlayer anions readily replaced by carbonate are characterized by X-ray diffraction (XRD) and FTIR. The effects of different parameters, such as pH, contact time, concentration of dye and temperature on the capacity and adsorption mechanism of Mg-Fe-CO{sub 3}-LDH in removing an anionic dye (congo red, CR) from aqueous solution were separately investigated. The results show that Mg-Fe-CO{sub 3}-LDH is particularly efficient in removing CR and the dye removal increases with decreasing pH. The adsorption of CR on Mg-Fe-CO{sub 3}-LDH reached equilibrium after 15 min where 100 mg/L CR was removed. The equilibrium isotherm indicates that the adsorption of CR onto Mg-Fe-CO{sub 3}-LDH fits to Langmuir and Freundlich equation as well. The adsorption data obtained from the Langmuir model gave good values of the determination coefficient and the saturated adsorption capacity of Mg-Fe-CO{sub 3}-LDH for CR was found to be 104.6 mg/g. The regeneration study indicates that the prepared LDH could be used for several cycles. The thermodynamic parameters have been calculated, and the adsorption process was found to be spontaneous, endothermic in nature and follows a pseudo-second-order kinetic model.

  5. A novel method of synthesizing cyclodextrin grafted multiwall carbon nanotubes/iron oxides and its adsorption of organic pollutant

    Highlights: • A cost-effective and one-step method for grafting cyclodextrin onto magnetic material. • Relatively good separation and regeneration properties as adsorbent. • The adsorption capacities are comparable with other adsorbents reported previously. - Abstract: A novel methodology for the synthesis of the multiwalled carbon nanotubes/iron oxides modified by β-cyclodextrin (denoted as MWCNTs/iron oxides/β-CD) was proposed using 1,6-diisocyanatohexane as cross-linker in N,N-dimethyl formamide, which avoided complex steps in the link of β-cyclodextrin and MWCNTs/iron oxides via conventional synthetic methods. The characteristic results of Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and thermogravimetric analysis (TGA) showed that β-CD was grafted onto the MWCNTs/iron oxides successfully. In addition, vibrating sample magnetometer (VSM) and magnetic separation experiment suggested that the prepared composite exhibited preferable magnetic property and good dispersion property in aqueous solution. The effects of contact time, initial adsorbent content, solution pH and temperature on the adsorption of p-nitrophenol (PNP) were studied systematically. The adsorption kinetics and equilibrium isotherms data fitted well with pseudo-second-order kinetic equation and Langmuir isotherm model, respectively. Furthermore, the adsorption-desorption experiment of PNP demonstrated that MWCNTs/iron oxides/β-CD is a cost-effective material with high regeneration efficiency

  6. A novel method of synthesizing cyclodextrin grafted multiwall carbon nanotubes/iron oxides and its adsorption of organic pollutant

    Liu, Wei; Jiang, Xinyu [School of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Chen, Xiaoqing, E-mail: xqchen@csu.edu.cn [School of Chemistry and Chemical Engineering, Central South University, Changsha 410083 (China); Collaborative Innovation Center of Resource-conserving and Environment-friendly Society and Ecological Civilization (China)

    2014-11-30

    Highlights: • A cost-effective and one-step method for grafting cyclodextrin onto magnetic material. • Relatively good separation and regeneration properties as adsorbent. • The adsorption capacities are comparable with other adsorbents reported previously. - Abstract: A novel methodology for the synthesis of the multiwalled carbon nanotubes/iron oxides modified by β-cyclodextrin (denoted as MWCNTs/iron oxides/β-CD) was proposed using 1,6-diisocyanatohexane as cross-linker in N,N-dimethyl formamide, which avoided complex steps in the link of β-cyclodextrin and MWCNTs/iron oxides via conventional synthetic methods. The characteristic results of Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), and thermogravimetric analysis (TGA) showed that β-CD was grafted onto the MWCNTs/iron oxides successfully. In addition, vibrating sample magnetometer (VSM) and magnetic separation experiment suggested that the prepared composite exhibited preferable magnetic property and good dispersion property in aqueous solution. The effects of contact time, initial adsorbent content, solution pH and temperature on the adsorption of p-nitrophenol (PNP) were studied systematically. The adsorption kinetics and equilibrium isotherms data fitted well with pseudo-second-order kinetic equation and Langmuir isotherm model, respectively. Furthermore, the adsorption-desorption experiment of PNP demonstrated that MWCNTs/iron oxides/β-CD is a cost-effective material with high regeneration efficiency.

  7. Study of plutonium adsorption by fibrous adsorbent

    Japan Atomic Energy Research Institute and Unitika Ltd. have been conducting, under a joint effort, development of an inorganic fibrous adsorbent (FAC), which is capable of adsorbing plutonium (Pu) contained in radioactive liquid waste and which is also able to contribute to reduction of the volume of α-waste by incineration. The fibrous adsorbent constitutes fibrous activated carbon of coal tar pitch derivative and has the following characteristics: (1) It has a large surface area. (2) Carbon constitutes more than 90% in the adsorbent; it is physically and chemically stable as an inorganic adsorbent; it is easy to be incinerated. (3) It is easy to be formed or molded into different shapes such as cartridges, and handling of the material is extremely easy. By using various kinds of Pu solution, we carried out tests and evaluations on the equilibrium adsorption quantity of Pu by the fibrous adsorbent, the adsorption property of the material by flow-through column test and the incineration property of the material in the cold test. The tests show that: (1) adsorption of Pu is the best with 0.8∼0.9 mg-Pu/g-FAC when the concentration of nitric acid is near 1 M; (2) as the concentration of nitric acid is increased, its adsorption capacity becomes poorer; (3) when Pu coexists with Uranium (U), the adsorption capacity becomes slightly inferior; (4) in the flow-through column test, no breakthrough of Pu was observed until the volume of Pu liquid becomes about 3 times larger than the column volume; (5) in the incineration tests in the cold test using a laboratory scale incinerator, no flying of particles or soot was observed; and (6) it is possible to get good incineration at 500 ∼ 600 degrees C. The above results show that, by using the fibrous adsorbent, it became possible to remove Pu from radioactive liquid waste by adsorption, to reduce the volume only to residual ash by incineration, and to reduce substantially the volume of α-waste

  8. Dynamic analysis of the CTAR (constant temperature adsorption refrigeration) cycle

    The basic SAR (solar-driven adsorption refrigeration) machine is an intermittent cold production system. Recently, the CO-SAR (continuous operation solar-powered adsorption refrigeration) system is developed. The CO-SAR machine is based on the theoretical CTAR (constant temperature adsorption refrigeration) cycle in which the adsorption process takes place at a constant temperature that equals the ambient temperature. Practically, there should be a temperature gradient between the adsorption bed and the surrounding atmosphere to provide a driving potential for heat transfer. In the present study, the dynamic analysis of the CTAR cycle is developed. This analysis provides a comparison between the theoretical and the dynamic operation of the CTAR cycle. The developed dynamic model is based on the D-A adsorption equilibrium equation and the energy and mass balances in the adsorption reactor. Results obtained from the present work demonstrate that, the idealization of the constant temperature adsorption process in the theoretical CTAR cycle is not far from the real situation and can be approached. Furthermore, enhancing the heat transfer between the adsorption bed and the ambient during the bed pre-cooling process helps accelerating the heat rejection process from the adsorption reactor and therefore approaching the isothermal process. - Highlights: • The dynamic analysis of the CTAR (constant temperature adsorption refrigeration) cycle is developed. • The CTAR theoretical and dynamic cycles are compared. • The dynamic cycle approaches the ideal one by enhancing the bed precooling

  9. Long-term balance in heavy metal adsorption and release in biochar derived from sewage sludge

    Sohi, Saran; Cleat, Robert; Graham, Margaret; Cross, Andrew

    2014-05-01

    In Europe, sewage sludge has major potential as a resource for producing biochar. Biochar from sludge could offer a means for the controlled recycling of phosphorus to soil, with the additional benefit of carbon stabilisation. Biochar made from contaminated feedstock could, however, also leach heavy metals into soil. Counter to release of metals, biochar from fresh plant biomass has a documented affinity and adsorption capacity. The longer term balance of release and adsorption of metals in sludge-derived biochar has not been established. Our work compared the adsorption and release of both indigenous metals and metals adsorbed to sludge derived biochar. The hypotheses were threefold: (1) the capacity to adsorb metals is lower than the potential to release them, (2) the affinity for indigenous metals is higher than for metals in solution, 3) oxidative ageing of biochar leads to partial release of adsorbed metals. Sludge biochar was produced in a horizontal, externally heated kiln at a feed rate of approx. 0.5 kg/hr. Dry sludge was converted in a 20 min. transit time with peak kiln temperature of 550°C. Elemental analysis using ICP OES (after a published preparation step) showed Zn, Pb and Cu to be the most abundant heavy metals in the biochar. The same elements were assessed in sequential water and Mehlich III extracts. Adsorption of the metals from pure and mixed Zn, Pb and Pb solutions were undertaken before and after the other extractions. All the treatments were applied to the same biochar after oxidative ageing, in which biochar C was also found to be very stable. Extractability of all three metals from fresh biochar was low (less than 5 %), but for two of the metals it was lower after ageing. For one of the metals, ageing increased extractability. For the same metal, adsorption was lower when undertaken with a mixed rather than pure solution. Capacity for adsorption of one of the other metals was higher after biochar ageing; the general capacity for metal

  10. CrⅥ adsorption on four typical soil colloids: equilibrium and kinetics

    2000-01-01

    It is observed that the adsorption of chromium are greater on kaolinite minerals, red soil (R) and laterite (L) colloids than that on montmorillonite, indicotic black (IB) and yellow brown (YB) soil colloids. The adsorption process of CrⅥ on these media can be further described by Langmuir or Freundlich equation quite well. The adsorption reaction of CrⅥ is fast, and the adsorption equilibrium can be reached within the first two hours in moderate temperature. The adsorption quantity of CrⅥ to kaolinite mineral increased with the increasing pH in the range of 2.0 to 7.0, then decreased at higher pH. But it showed some consistence among the four soil colloids. The lower the pH, the stronger the adsorption. The possible mechanisms are further discussed here. Meanwhile the influence of temperature on CrⅥ adsorption on different soil colloid and clay minerals are also investigated.

  11. Determination of Differential Enthalpy and Isotherm by Adsorption Calorimetry

    V. Garcia-Cuello

    2008-01-01

    Full Text Available An adsorption microcalorimeter for the simultaneous determination of the differential heat of adsorption and the adsorption isotherm for gas-solid systems are designed, built, and tested. For this purpose, a Calvet heat-conducting microcalorimeter is developed and is connected to a gas volumetric unit built in stainless steel to record adsorption isotherms. The microcalorimeter is electrically calibrated to establish its sensitivity and reproducibility, obtaining K=154.34±0.23 WV−1. The adsorption microcalorimeter is used to obtain adsorption isotherms and the corresponding differential heats for the adsorption of CO2 on a reference solid, such as a NaZSM-5 type zeolite. Results for the behavior of this system are compared with those obtained with commercial equipment and with other studies in the literature.

  12. Influences of Soluble Salts on Adsorption Properties of Polycarboxylate Superplasticizers

    WANG Dongmin; CHENG Peifu; XIONG Weifeng; SONG Taowen; WU Zengli

    2012-01-01

    Polycarboxylate (PC) superplasticizers with different chemical structures were synthesized through free radical co-polymerization reaction.A total organic carbon analyzer was used to investigate adsorption behaviors of PCs,and to evaluate influences of soluble salts on absorption properties of PCs.It is found that adsorption ratios of PCs on cement particles decrease greatly with the addition of Na2SO4; the adsorption ratio of ethers PC with Hydroxyethyl methacrylate (HEMA) group first increases then decreases with the addition of NaCl; the adsorption ratio of esters PC with short side chains first decreases then increases,while the adsorption ratio of ethers PC with HEMA group decreases with the addition of CaCl2; the adsorption ratio of esters PC with short side chains decreases with the addition of Ca(NO3)2; AlCl3 causes the decrease of the adsorption ratio of ethers PC with HEMA group.

  13. Adsorption behavior of 239Pu by Gaomiaozi bentonite

    Adsorption behavior of 239Pu by Gaomiaozi bentonite as a function of the factors of aqueous phase pH value, 239Pu initial concentration and ionic species is studied by static adsorption experiments in this paper. The following results are obtained. Adsorption equilibrium time of 239Pu by Gaomiaozi bentonite samples is about 24 h, and the adsorption distribution ratio Kd value of 239Pu increases with the pH value, but decreases with increasing initial concentration of 239Pu. And adsorption of 239Pu by bentonite samples with different ionic species show that anions affect the most on adsorption of bentonite is CO32-, followed by HCO3- and SO42-, whereas Cl- and NO3- hardly have any influence on the adsorption of bentonite. (authors)

  14. Adsorption of Anionic Dyes onto Chitosan-modified Diatomite

    ZHANG Ge-shan; XUE Hong-hai; TANG Xiao-jian; PENG Fei; KANG Chun-li

    2011-01-01

    The purpose of this work is to study the possibility of anionic dyes Reactive Red M-8B(RR)and Direct Green B(DG)adsorbed on chitosan-modified diatomite.The characteristics of adsorbent,adsorption isotherms and the influence of adsorption time,temperature and pH were researched in this work.The results show that the modified diatomite had a much better adsorption capability than the natural diatomite.The adsorption capacities of chitosan-modified diatomite for RR and DG were 94.46 and 137.0 mg/g,respectively.Both adsorption time and adsorption temperature provided a positive effect on the dye adsorption.Within the experimental pH range,the adsorbance was enhanced at lower pH but reduced sharply at high pH.On the basis of the experimental results and discussion,electrostatic attraction is considered as the main mechanism of this chemisorption.

  15. Adsorption of EDTA on activated carbon from aqueous solutions

    In this study, the adsorption of EDTA on activated carbon from aqueous solutions has been investigated in a batch stirred cell. Experiments have been carried out to investigate the effects of temperature, EDTA concentration, pH, activated carbon mass and particle size on EDTA adsorption. The experimental results manifest that the EDTA adsorption rate increases with its concentration in the aqueous solutions. EDTA adsorption also increases with temperature. The EDTA removal from the solution increases as activated carbon mass increases. The Langmuir and Freundlich equilibrium isotherm models are found to provide a good fitting of the adsorption data, with R2 = 0.9920 and 0.9982, respectively. The kinetic study shows that EDTA adsorption on the activated carbon is in good compliance with the pseudo-second-order kinetic model. The thermodynamic parameters (Ea, ΔG0, ΔH0, ΔS0) obtained indicate the endothermic nature of EDTA adsorption on activated carbon.

  16. New insight on the behavior of the irreversible adsorption and underpotential deposition of thallium on platinum (111) and vicinal surfaces in acid electrolytes

    Rodriguez, P.; García-Aráez, N.; Herrero, E; Feliu, J.M.

    2015-01-01

    We report, for the first time, the electrochemical behavior of thallium irreversibly adsorbed on Pt (111) and platinum stepped surfaces composed of (111) terraces and monoatomic steps. Similar to the case of thallium UPD, the voltammograms obtained after thallium irreversible adsorption present three characteristic features. After a careful analysis of the effect of the thallium concentration, the concentration and nature of the anion of the supporting electrolyte and the pH of the solution o...

  17. Adsorption of bacteriocins by ingestible silica compounds.

    Wan, J; Gordon, J; Hickey, M W; Mawson, R F; Coventry, M J

    1996-08-01

    Bacteriocins including nisin, pediocin PO2, brevicin 286 and piscicolin 126 were adsorbed from culture supernates by various food-grade porous silica anti-caking agents and the food colourant, titanium dioxide. All the porous silica (calcium silicate or silicon dioxide) materials showed substantial capacity in adsorbing bacteriocin activities from the culture supernate and biological activity was recovered in the adsorbents. In contrast, the food colourant titanium dioxide adsorbed most of the bacteriocin activity from the supernate, with minimal biological activity retained in the adsorbent. Experiments with piscicolin 126 showed that optimum adsorption could be achieved with Micro-Cel E within 30 min, independent of the supernate pH (2.0-10.0). Piscicolin activity of up to 5 x 10(7) AU g(-1) of Micro-Cel E was obtained after adsorption from culture supernates and the adsorbed piscicolin demonstrated substantial biological activity against Listeria monocytogenes in both broth and a milk growth medium. PMID:8926221

  18. The Use Of New Adsorption Technology

    Adsorption is widely used in Gas Dehydration. Recently, new technology has been applied by using a new type of silica gel adsorbent for both gas dehydration and hydrocarbon dew pointing. A study to evaluate the different methods of hydrocarbon dew pointing was performed by Enppi and proved that the use of adsorption process with a new type of silica gel has significant cost benefits over the life of field. In Egypt, this new technology has been used in the Rosetta gas plant, which was designed for 302 MMSCFD (275 + 10%). The plant has been operational for about 4 years and experience demonstrated that the new type of silica gel has high performance, excellent reliability and low operating cost. Following these good results, the plant has been tested up to 380 MMSCFD and again the adsorbent proved its high performance and efficiency

  19. Adsorption of octadecyltrichlorosilane on mesoporous SBA-15

    Adsorption of octadecyltrichlorosilane (OTS) on mesoporous SBA-15 has been studied by using Brunauer-Emmett-Teller (BET) surface area analysis, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and thermo-gravimetric analysis (TGA) techniques. BET surface area analysis shows decrease of surface area from 930 to 416 m2/g after OTS adsorption. SEM pictures show close attachment of SBA-15 particles. EDAX measurements show increase of carbon weight percentage and decrease of oxygen and silicon weight percentage. XPS results closely support EDAX analysis. FTIR spectra shows presence of methyl (-CH3) and methylene (-CH2) bands and oriented OTS monolayer on SBA-15. Thermo-gravimetric analysis shows that the OTS adsorbed on SBA-15 are stable up to a temperature of 230 deg. C and that the OTS monolayers decompose between 230 and 400 deg. C

  20. Adsorption of octadecyltrichlorosilane on mesoporous SBA-15

    Mirji, S.A. [Physical Chemistry Division, National Chemical Laboratory, Pune 411008 (India)]. E-mail: mirji@dalton.ncl.res.in; Halligudi, S.B. [Inorganic and Catalysis Division, National Chemical Laboratory, Pune 411008 (India); Sawant, Dhanashri P. [Inorganic and Catalysis Division, National Chemical Laboratory, Pune 411008 (India); Jacob, Nalini E. [Inorganic and Catalysis Division, National Chemical Laboratory, Pune 411008 (India); Patil, K.R. [Center for Material Characterization, National Chemical Laboratory, Pune 411008 (India); Gaikwad, A.B. [Center for Material Characterization, National Chemical Laboratory, Pune 411008 (India); Pradhan, S.D. [Center for Material Characterization, National Chemical Laboratory, Pune 411008 (India)

    2006-04-15

    Adsorption of octadecyltrichlorosilane (OTS) on mesoporous SBA-15 has been studied by using Brunauer-Emmett-Teller (BET) surface area analysis, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and thermo-gravimetric analysis (TGA) techniques. BET surface area analysis shows decrease of surface area from 930 to 416 m{sup 2}/g after OTS adsorption. SEM pictures show close attachment of SBA-15 particles. EDAX measurements show increase of carbon weight percentage and decrease of oxygen and silicon weight percentage. XPS results closely support EDAX analysis. FTIR spectra shows presence of methyl (-CH{sub 3}) and methylene (-CH{sub 2}) bands and oriented OTS monolayer on SBA-15. Thermo-gravimetric analysis shows that the OTS adsorbed on SBA-15 are stable up to a temperature of 230 deg. C and that the OTS monolayers decompose between 230 and 400 deg. C.

  1. Removal of mercury by adsorption: a review.

    Yu, Jin-Gang; Yue, Bao-Yu; Wu, Xiong-Wei; Liu, Qi; Jiao, Fei-Peng; Jiang, Xin-Yu; Chen, Xiao-Qing

    2016-03-01

    Due to natural and production activities, mercury contamination has become one of the major environmental problems over the world. Mercury contamination is a serious threat to human health. Among the existing technologies available for mercury pollution control, the adsorption process can get excellent separation effects and has been further studied. This review is attempted to cover a wide range of adsorbents that were developed for the removal of mercury from the year 2011. Various adsorbents, including the latest adsorbents, are presented along with highlighting and discussing the key advancements on their preparation, modification technologies, and strategies. By comparing their adsorption capacities, it is evident from the literature survey that some adsorbents have shown excellent potential for the removal of mercury. However, there is still a need to develop novel, efficient adsorbents with low cost, high stability, and easy production and manufacture for practical utility. PMID:26620868

  2. Adsorption of maleic anhydride on Pt(111)

    Sinha, Godhuli; Heikkinen, Olli; Vestberg, Matias; Mether, Lotta; Nordlund, Kai; Lahtinen, Jouko

    2014-02-01

    The surface chemistry of maleic anhydride (MA) has been studied on Pt(111) with temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. Adsorption of MA takes place at 170 K forming multilayers. We have studied the behavior of distinct carbon and oxygen species of MA depending on the surface temperature. MA-TPD indicates three main desorption temperatures; at 240 K, approximately 60% of total MA on the surface shows molecular desorption. At high temperatures (360 and 550 K) MA shows dissociative decomposition with production of C2H2, CO and CO2 fragments. A plausible decomposition pathway of MA on the Pt(111) surface is discussed. DFT calculations provide details of the adsorption geometry.

  3. [Water binding of adsorptive immobilized lipases].

    Loose, S; Meusel, D; Muschter, A; Ruthe, B

    1990-01-01

    It is supposed that not only the total water content of lipase preparations but more their state of water binding is of technological importance in enzymatic interesterification reactions in systems nearly free from water. The isotherms at 65 degrees C of two microbial lipases immobilized on various adsorbents as well as different adsorbents themselves are shown. The water binding capacity in the range of water content of technological interest decreases from the anion exchange resin Amberlyst A 21 via nonpolar adsorbent Amberlite XAD-2 to kieselguhr Celite 545. It is demonstrated that water binding by lipases is depending on temperature but is also affected by adsorptive immobilization. Adsorptive immobilized lipases show hysteresis, which is very important for preparing a definite water content of the enzyme preparations. PMID:2325750

  4. Steps Towards an Evolutionary Physics

    Tiezzi, E

    2006-01-01

    If thermodynamics is to physics as logic is to philosophy, recent theoretical advancements lend new coherence to the marvel and dynamism of life on Earth. Enzo Tiezzi's "Steps Towards an Evolutionary Physics" is a primer and guide, to those who would to stand on the shoulders of giants to attain this view: Heisenberg, Planck, Bateson, Varela, and Prigogine as well as notable contemporary scientists. The adventure of such a free and enquiring spirit thrives not so much on answers as on new questions. The book offers a new gestalt on the uncertainty principle and concept of probability. A wide r

  5. Nitrate Adsorption on Clay Kaolin: Batch Tests

    Morteza Mohsenipour; Shamsuddin Shahid; Kumars Ebrahimi

    2015-01-01

    Soils possessing kaolin, gibbsite, goethite, and hematite particles have been found to have a natural capacity to attenuate pollution in aqueous phase. On the other hand, the hydroxyl group in soil increases anion exchange capacity under a low pH condition. The main objective of this paper was to evaluate effects of kaolin on nitrate reduction under acidic condition. In order to analyze the kaolin adsorption behaviour under various conditions, four different concentrations of nitrate, 45, 112...

  6. Adsorption and Biocirculation in Oceanic Waters

    It is generally known that in recent years oceanographers in all countries have denoted great attention to studying the dispersion routes and speed of movement of radioactive decay products in oceanic waters. At the same time the form, degree and extent of contamination of oceanic waters by fission products has been investigated. It is clear that scientists are becoming more and more interested in living organisms as a factor responsible for the transport and distribution of radioactive substances in water. B. Ketchum and Y. Bowen discuss the concept of “biological transport” and make an interesting attempt to define it in mathematical terms and to collate it with research on “physical transport”. The term “biocirculation” has come into use. It is evident that this factor cannot be left out of account as a means of transport or system of adsorption. The great volume of suspension formed of mineral substances and not containing living organisms is characterized by its relatively low mobility, and the bacterial and phytoplankton bodies constitute a vast adsorption surface (Tables 1 and 2). The ocean water column contains a vast quantity of matter in suspension, including living organisms (bacteria, phytoplankton and zooplankton) and components not containing living organisms (bioseston and abioseston). Quantitative determination of all the seston enables its role as an adsorption surface and as a mechanism of vertical and horizontal biocirculation to be evaluated. The adsorption surface for various seston groups in average density distribution zones, and the index of subsurface biocirculation in a water column less than 1 m2 in the habitat are given

  7. Interfacial Interactions, Competitive Adsorption and Emulsion Stability

    Chen, Jianshe; Dickinson, Eric; Iveson, Graeme

    1993-01-01

    Food emulsion stability is strongly influenced by the interactions in the adsorbed layer around emulsion droplets. Competitive adsorption of pure milk proteins (13-casein or 13 -lactoglobulin) with nonionic surfactants in oil-in-water emulsions is shown to depend on the age of the adsorbed protein layer. Evidence is presented for slow accumulation of protein at the oil-water interface and/or partition of protein into the oil phase of emulsion droplets containing oil-soluble surfactant associa...

  8. Arsenic Adsorption Onto Iron Oxides Minerals

    Aredes, S.; Klein, B.; Pawlik, M.

    2004-12-01

    The predominant form of arsenic in water is as an inorganic ion. Under different redox conditions arsenic in water is stable in the +5 and +3 oxidation states. Arsenic oxidation state governs its toxicity, chemical form and solubility in natural and disturbed environments. As (III) is found in anoxic environments such as ground water , it is toxic and the common species is the neutral form, H3AsO3. As (V) is found in aerobic conditions such as surface water, it is less toxic and the common species in water are: H2AsO4 - and HAsO4 {- 2}. The water pH determines the predominant arsenate or arsenite species, however, both forms of arsenic can be detected in natural water systems. Iron oxides minerals often form in natural waters and sediments at oxic-anoxic boundaries. Over time they undergo transformation to crystalline forms, such as goethite or hematite. Both As(V) and As(III) sorbs strongly to iron oxides, however the sorption behavior of arsenic is dependent on its oxidation state and the mineralogy of the iron oxides. Competition between arsenic and others ions, such fluoride, sulphate and phosphate also play a role. On the other hand, calcium may increase arsenic adsorption onto iron oxides. Electrokinetic studies and adsorption experiments were carried out in order to determine which conditions favour arsenic adsorption. Hematite, goethite and magnetite as iron based sorbents were used. Test were also conducted with a laterite soil rich in iron minerals. The focus of this study is to evaluate physical and chemical conditions which favour arsenic adsorption onto iron oxides minerals, the results contribute to an understanding of arsenic behaviour in natural and disturbed environments. Furthermore, results could contribute in developing an appropriate remediation technology for arsenic removal in water using iron oxides minerals.

  9. Managing numerical errors in random sequential adsorption

    Cieśla, Michał; Nowak, Aleksandra

    2016-09-01

    Aim of this study is to examine the influence of a finite surface size and a finite simulation time on a packing fraction estimated using random sequential adsorption simulations. The goal of particular interest is providing hints on simulation setup to achieve desired level of accuracy. The analysis is based on properties of saturated random packing of disks on continuous and flat surfaces of different sizes.

  10. COMPARISON OF BET AND WATER ADSORPTION TECHNIQUES

    B. H. Diyaâuddeen; I. A. Mohammed; B. Y. Jibril; I. M. Bugaje

    2013-01-01

    The effect of activated carbon surface area on the amount of fluid adsorbed is significant. Thus, the surface area of an adsorbent is an important factor. The use of the costly BET measurement method is the standard. However, water adsorption method was proposed as an alternate method. Nevertheless, results presented were for activated carbon prepared and surface areas reported were based on BET literature values. In this study, chemically activated carbons were produced from corn cobs by imp...

  11. Dopamine Adsorption Configurations on Anatase (101) Surface

    Stashans, Arvids; Marcillo, Freddy; Castillo, Darwin

    2015-05-01

    Present work is based on the density functional theory (DFT) and generalized gradient approximation studies. Different adsorption geometries of dopamine, C8H11O2N, on the anatase (101) surface have been considered and carefully investigated. Bidentate chelating configuration with two molecular oxygens binding to the same surface titanium has been found to be the equilibrium case. The Ti-O distances for this configuration are obtained to be equal to 2.23 and 2.37 Å, respectively.

  12. Estrogenic micropollutant adsorption dynamics onto nanofiltration membranes

    Correia Semiao, Andrea; Schaefer, Andrea

    2011-01-01

    Nanofiltration (NF) is used in water and wastewater treatment as well as water recycling applications, treating micropollutants such as hormones. Due to their potential health risk it is critical to develop effective treatment processes. Polymeric NF membranes should be effective in removing such micropollutants based on molecular size. However, the occurrence of adsorption onto the membranes results in unpredictable performance. It is hence important to understand NF retention mechanisms.The...

  13. The molecular dynamics of adsorption and dissociation of O2 on Pt(553)

    Molecular adsorption and dissociation of O2 on the stepped Pt(553) surface have been investigated using supersonic molecular beam techniques and temperature programmed desorption. The initial and coverage-dependent sticking probability was determined with the King and Wells technique for various combinations of incident kinetic energy, surface temperature, incident angle, and surface coverage. A comparison with similar data for Pt(533) and Pt(110)(1 × 2) shows quantitatively the same high step-induced sticking at low incident energies compared to Pt(111). The enhancement is therefore insensitive to the exact arrangement of atoms forming surface corrugation. We consider energy transfer and electronic effects to explain the enhanced sticking. On the other hand, dissociation dynamics at higher incident kinetic energies are strongly dependent on step type. The Pt(553) and Pt(533) surfaces are more reactive than Pt(111), but the (100) step shows higher sticking than the (110) step. We relate this difference to a variation in the effective lowering of the barrier to dissociation from molecularly adsorbed states into atomic states. Our findings are in line with results from experimental desorption studies and theoretical studies of atomic binding energies. We discuss the influence of the different step types on sticking and dissociation dynamics with a one-dimensional potential energy surface

  14. Line contribution to the critical Casimir force between a homogeneous and a chemically stepped surface

    Parisen Toldin, Francesco; Tröndle, Matthias; Dietrich, S.

    2015-06-01

    Recent experimental realizations of the critical Casimir effect have been implemented by monitoring colloidal particles immersed in a binary liquid mixture near demixing and exposed to a chemically structured substrate. In particular, critical Casimir forces have been measured for surfaces consisting of stripes with periodically alternating adsorption preferences, forming chemical steps between them. Motivated by these experiments, we analyze the contribution of such chemical steps to the critical Casimir force for the film geometry and within the Ising universality class. By means of Monte Carlo simulations, mean-field theory and finite-size scaling analysis we determine the universal scaling function associated with the contribution to the critical Casimir force due to individual, isolated chemical steps facing a surface with homogeneous adsorption preference or with Dirichlet boundary condition. In line with previous findings, these results allow one to compute the critical Casimir force for the film geometry and in the presence of arbitrarily shaped, but wide stripes. In this latter limit the force decomposes into a sum of the contributions due to the two homogeneous parts of the surface and due to the chemical steps between the stripes. We assess this decomposition by comparing the resulting sum with actual simulation data for the critical Casimir force in the presence of a chemically striped substrate.

  15. Hydraulic Design of Stepped Spillways Workshop

    Stepped chutes and spillways are commonly used for routing discharges during flood events. In addition, stepped chutes are used for overtopping protection of earthen embankments. Stepped spillways provide significant energy dissipation due to its stepped feature; as a result, the stilling basin as...

  16. Steps in Researching the Music in Therapy

    Bonde, Lars Ole

    2007-01-01

    The chapter introduces a generic flowchart + step-by-step guide for microanalysis of music (compositions and improvisations) in music therapy.......The chapter introduces a generic flowchart + step-by-step guide for microanalysis of music (compositions and improvisations) in music therapy....

  17. Adsorption of tetrahydroxybenzene on metal surfaces

    Bebensee, Fabian; Bombis, Christian; Masini, Federico; Laegsgaard, Erik; Besenbacher, Flemming; Linderoth, Trolle R. [NANO, Aarhus University, Aarhus (Denmark); Klyatskaya, Svetlana; Ruben, Mario [Karlsruhe Institure of Technology (KIT), Institut fuer Nanotechnologie, Karlsruhe (Germany)

    2011-07-01

    The synthesis of extended, well-ordered bi-dimensional molecular networks on surfaces has received a great deal of interest over the past years, fueled not least by potential applications such as functionalized surface coatings, sensors and molecular electronics. Here, we employ scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) to study the adsorption of tetrahydroxybenzene (THB) on the Au(111) and Cu(111) surfaces. The molecule shows a complex adsorption behavior despite being structurally rather simple. Depending on post-deposition treatment, coverage and substrate, we find different adsorption structures: a hexagonal close-packed phase and a porous network structure exhibiting a high degree of order. The XPS results reveal that the transformation from the hexagonal close-packed phase to the porous network is linked to a chemical modification of THB, possibly involving dehydrogenation of the molecules. We tentatively propose that the porous network, which was observed solely on the Cu(111) surface, is a metal complexation structure involving native Cu released during post-deposition annealing.

  18. Simulation of an adsorption solar cooling system

    A more realistic theoretical simulation model for a tubular solar adsorption refrigerating system using activated carbon-methanol (AC/M) pair has been introduced. The mathematical model represents the heat and mass transfer inside the adsorption bed, the condenser, and the evaporator. The simulation technique takes into account the variations of ambient temperature and solar radiation along the day. Furthermore, the local pressure, and local thermal conductivity variations in space and time inside the tubular reactor are investigated as well. A C++ computer program is written to solve the proposed numerical model using the finite difference method. The developed program covers the operations of all the system components along the cycle time. The performance of the tubular reactor, the condenser, and the evaporator has been discussed. Time allocation chart and switching operations for the solar refrigeration system processes are illustrated as well. The case studied has a 1 m2 surface area solar flat plate collector integrated with a 20 stainless steel tubes containing the AC/M pair and each tube has a 5 cm outer diameter. In addition, the condenser pressure is set to 54.2 kpa. It has been found that, the solar coefficient of performance and the specific cooling power of the system are 0.211 and 2.326 respectively. In addition, the pressure distribution inside the adsorption bed has been found nearly uniform and varying only with time. Furthermore, the AC/M thermal conductivity is shown to be constant in both space and time.

  19. Adsorption of ions onto treated natural zeolite

    Cristiane da Rosa Oliveira

    2007-12-01

    Full Text Available This work presents studies of modification of a natural zeolite by activation with Na+ cations and functionalisation with Ba+2 and/or Cu2+ ions (FZ. The zeolite was characterized, modified and applied in adsorption studies of sulphate and isopropilxanthate ions as flocculated and powdered forms. The reuse of SO4Ba-FZ was investigated by adsorption-removal of either Ba2+ or sulphate ions in stages. Equilibrium data showed that the FZ, flocculated or as powder, provide considerable removal of sulphate ions (q mLangmuir: 1.15 and 1.35 meq.g-1, respectively and isopropilxanthate (q mLangmuir: 0.35 and 0.93 meq.g-1, respectively. The reuse of the SO4-FZ, either powdered or flocculated also uptake significant amount of Ba2+ or sulphate ions (q mLangmuir: 1.15 meq.g-1, providing a new alternative for the exhausted adsorbent. Thus the activated and functionalised zeolites create new options on the materials engineering area with applications in environmental applied adsorption processes.

  20. Hydrogen adsorption in doped porous carbons

    Full text of publication follows: Hydrogen is a clean fuel that will be used in automotive transport when the problem of storage will be solved. The difficulties of H2 storage (available space, security and performance, etc...) require a material that can store 5 weight % of hydrogen. Research is focused on new materials that can assume the constraints imposed by the automotive applications. Among these materials, the nano-structured carbons (nano-fibers and single walled carbon nano-tubes) were claimed to be promising by numerous authors [1-3]. The more promising carbon materials for hydrogen adsorption are those having micropores (i. e. single walled carbon nano-tubes and activated carbon), for which the energy of sorption of hydrogen molecules is theoretically higher [7- 8]. Presently, the best performance of hydrogen adsorption was found in super-activated micro-porous carbons sorbing 5 weight % at 77 K, and almost 0.5 % at room temperature and 6 MPa [9]. Up to now, the performance of these materials can still be improved as the known mechanism of sorption in these carbon materials: physisorption controlled by Van der Waals attractive forces through London interaction is efficient at cryogenic temperatures (77 K) where the interaction between adsorbent and adsorbate becomes stronger. One way to improve the attractive interaction between adsorbent and molecule is to increase the forces due to the interaction of electrical field and induced dipole of the molecule. This can be theoretically tailored in carbon materials through the electron charge transfer by electron donors who can provide an increase in the electrical field al the surface of the adsorbent. Then, the doping of carbon substrates, appearing to be a promising method to increase the energy of adsorption has been proposed in recent papers as a solution to obtain good hydrogen adsorption properties at appropriate temperatures close to room temperatures [10-12]. Thus, we have studied the adsorption