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Sample records for adsorption capacity calculated

  1. Surface retention capacity calculation

    NASA Astrophysics Data System (ADS)

    David, Vaclav; Dostal, Tomas

    2010-05-01

    Flood wave transformation in the floodplain is the phenomenon which is researched within interdisciplinary project NIVA - Water Retention in Floodplains and Possibilities of Retention Capacity Increase. The project focuses on broad range of floodplain ecosystem services and mitigation of flooding is one of them. Despite main influence on flood wave transformation is due to flow retardation, retention in surface depressions within floodplain has been analyzed to get better overview of whole transformation process. Detail digital relief model (DRM) has been used for given purposes to be able to analyze terrain depressions volumes. The model was developed with use of stereophotogrammetric evaluation of airborne images with high resolution of 10 cm. It was essential for purposes of presented analysis not to apply pit removal routines which are often used for generation of DRM for hydrological modelling purposes. First, the methodology of analysis was prepared and tested on artificial surface. This surface was created using random raster generation, filtration and resampling with final resolution of 1000 x 1000 units and height of maximum 10 units above datum. The methodology itself is based on analysis of areas inundated by water at different elevation levels. Volume is than calculated for each depression using extraction of terrain elevations under corresponding water level. The method was then applied on the area of Lužnice River floodplain section to assess retention capacity of real floodplain. The floodplain had to be cut into sections perpendicular to main river orientation for analyses as the method was tested for square shaped area without any significant inclination. Results obtained by mentioned analysis are presented in this paper. Acknowledgement Presented research was accomplished within national project NIVA - Water Retention in Floodplains and Possibilities of Retention Capacity Increase, nr. QH82078. The project is funded by Ministry of Agriculture of

  2. Effect of moisture on adsorption isotherms and adsorption capacities of CO{sub 2} on coals

    SciTech Connect

    Ekrem Ozdemir; Karl Schroeder

    2009-05-15

    The effect of moisture on the adsorption isotherms and adsorption capacities of CO{sub 2} on Argonne Premium coals has been investigated. In some experiments a small hysteresis was observed between the adsorption and desorption isotherms. The hysteresis was absent or negligible for high-rank and as-received coals but was discernible for lower rank and dried coals. An equation that accounted for the volumetric changes when an adsorbate alters the structure of an adsorbent was employed to interpret the data. The best-fit solutions indicate that the coal volume decreases upon drying. The microscopic shrinkage estimated using helium expansion was greater than the shrinkage reported using the bed-height technique. The microscopic shrinkage was 5-10% for low-moisture medium and high-rank coals and up to 40% for low-rank coals having higher moisture contents. The CO{sub 2} swelling of coals during adsorption isotherm measurements was estimated to be about the same as the shrinkage that occurred during the moisture loss. The adsorption capacity, isosteric heat of adsorption, average pore size, and surface area of the as-received (moist) and dried Argonne coals were estimated after accounting for the volume changes. The isosteric heat of adsorption of CO{sub 2} was found to be between 23 and 25 kJ/mol for as-received coals and between 25 and 27 kJ/mol for dried coals, regardless of the rank. The degree of drying was shown to affect the adsorption capacity and the calculated surface area. For dried coals, the adsorption capacity showed the typical 'U-shape' dependence on rank whereas the as-received coals displayed a more linear dependence. A relationship is proposed to quantify the effect of moisture on the adsorption capacity. The mechanism of CO{sub 2} adsorption on moist coals and the implications of the lower adsorption capacity of wet coals to coal seam sequestration of CO{sub 2} are presented. 70 refs., 12 figs., 2 tabs.

  3. Effect of pH on protein adsorption capacity of strong cation exchangers with grafted layer.

    PubMed

    Wrzosek, Katarzyna; Polakovič, Milan

    2011-09-28

    The effect of pH on the static adsorption capacity of immunoglobulin G, human serum albumin, and equine myoglobin was investigated for a set of five strong cation exchangers with the grafted tentacle layer having a different ligand density. A sharp maximum of adsorption capacity with pH was observed for adsorbents with a high ligand density. The results were elucidated using the protein structure and calculations of pK(a) of ionizable groups of surface basic residues. Inverse size-exclusion experiments were carried out to understand the relation between the adsorption capacity and pore accessibility of the investigated proteins. PMID:21855072

  4. Evaluating the Adsorptive Capacities of Chemsorb 1000 and Chemsorb 1425

    NASA Technical Reports Server (NTRS)

    Monje, Oscar Alberto Monje; Surma, Jan M.; Johnsey, Marissa N.; Melendez, Orlando

    2014-01-01

    The Air Revitalization Lab at KSC tested Chemsorb 1000 and 1425, two candidate sorbents for use in future air revitalization technologies being evaluated by the ARREM project. Chemsorb 1000 and 1425 are granular coconut-shell activated carbon sorbents produced by Molecular Products, Inc. that may be used in the TCCS. Chemsorb 1000 is a high grade activated carbon for organic vapor adsorption. In contrast, Chemsorb 1425 is a high-grade impregnated activated carbon for adsorption of airborne ammonia and amines. Chemsorb 1000 was challenged with simulated spacecraft gas streams in order to determine its adsorptive capacities for mixtures of volatile organics compounds. Chemsorb 1425 was challenged with various NH3 concentrations to determine its adsorptive capacity.

  5. High capacity adsorption media and method of producing

    DOEpatents

    Tranter, Troy J.; Mann, Nicholas R.; Todd, Terry A.; Herbst, Ronald S.

    2010-10-05

    A method of producing an adsorption medium to remove at least one constituent from a feed stream. The method comprises dissolving and/or suspending at least one metal compound in a solvent to form a metal solution, dissolving polyacrylonitrile into the metal solution to form a PAN-metal solution, and depositing the PAN-metal solution into a quenching bath to produce the adsorption medium. The at least one constituent, such as arsenic, selenium, or antimony, is removed from the feed stream by passing the feed stream through the adsorption medium. An adsorption medium having an increased metal loading and increased capacity for arresting the at least one constituent to be removed is also disclosed. The adsorption medium includes a polyacrylonitrile matrix and at least one metal hydroxide incorporated into the polyacrylonitrile matrix.

  6. High capacity adsorption media and method of producing

    DOEpatents

    Tranter, Troy J.; Herbst, R. Scott; Mann, Nicholas R.; Todd, Terry A.

    2008-05-06

    A method of producing an adsorption medium to remove at least one constituent from a feed stream. The method comprises dissolving at least one metal compound in a solvent to form a metal solution, dissolving polyacrylonitrile into the metal solution to form a PAN-metal solution, and depositing the PAN-metal solution into a quenching bath to produce the adsorption medium. The at least one constituent, such as arsenic, selenium, or antimony, is removed from the feed stream by passing the feed stream through the adsorption medium. An adsorption medium having an increased metal loading and increased capacity for arresting the at least one constituent to be removed is also disclosed. The adsorption medium includes a polyacrylonitrile matrix and at least one metal hydroxide incorporated into the polyacrylonitrile matrix.

  7. Methane Adsorption on Aggregates of Fullerenes: Site-Selective Storage Capacities and Adsorption Energies

    PubMed Central

    Kaiser, Alexander; Zöttl, Samuel; Bartl, Peter; Leidlmair, Christian; Mauracher, Andreas; Probst, Michael; Denifl, Stephan; Echt, Olof; Scheier, Paul

    2013-01-01

    Methane adsorption on positively charged aggregates of C60 is investigated by both mass spectrometry and computer simulations. Calculated adsorption energies of 118–281 meV are in the optimal range for high-density storage of natural gas. Groove sites, dimple sites, and the first complete adsorption shells are identified experimentally and confirmed by molecular dynamics simulations, using a newly developed force field for methane–methane and fullerene–methane interaction. The effects of corrugation and curvature are discussed and compared with data for adsorption on graphite, graphene, and carbon nanotubes. PMID:23744834

  8. Evaluation of the adsorption capacity of alkali-treated waste materials for the adsorption of sulphamethoxazole.

    PubMed

    Kurup, Lisha

    2012-01-01

    The present work is to develop potential adsorbents from waste material and employ them for the removal of a hazardous antibacterial, sulphamethoxazole, from the wastewater by the Adsorption technique. The Adsorption technique was used to impound the dangerous antibiotics from wastewater using Deoiled Soya (DOS), an agricultural waste, and Water Hyacinth (WH), a prolific colonizer. The adsorption capacity of these adsorbents was further enhanced by treating them with sodium hydroxide solution and it was seen that the adsorption capacity increases by 10 to 25%. Hence a comparative account of the adsorption studies of all the four adsorbents, i.e. DOS, Alkali-treated DOS, WH and Alkali-treated Water Hyacinth has been discussed in this paper. Different isotherms like Freundlich, Langmuir and Dubinin-Radushkevich were also deduced from the adsorption data. Isotherm studies were in turn used in estimating the thermodynamic parameters. DOS showed sorption capacity of 0.0007 mol g(-1) while Alkali-treated Deoiled Soya exhibited 0.0011 mol g(-1) of sorption capacity, which reveals that the adsorption is higher in case of alkali-treated adsorbent. The mean sorption energy (E) was obtained between 9 and 12 kJ mol, which shows that the reaction proceeds by ion exchange reaction. Kinetic study reveals that the reaction follows pseudo-second-order rate equation. Moreover, mass transfer studies performed for the ongoing processes show that the mass transfer coefficient obtained for alkali-treated moieties was higher than the parent moieties. The breakthrough curves plotted from the column studies show percentage saturation of 90-98%. About 87-97% of sulphamethoxazole was recovered from column by desorption. PMID:22508113

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Effect of purity on adsorption capacities of a Mars-like clay mineral at different pressures

    NASA Technical Reports Server (NTRS)

    Jenkins, Traci; Mcdoniel, Bridgett; Bustin, Roberta; Allton, Judith H.

    1992-01-01

    There has been considerable interest in adsorption of carbon dioxide on Marslike clay minerals. Some estimates of the carbon dioxide reservoir capacity of the martian regolith were calculated from the amount of carbon dioxide adsorbed on the ironrich smectite nontronite under martian conditions. The adsorption capacity of pure nontronite could place upper limits on the regolith carbon dioxide reservoir, both at present martian atmospheric pressure and at the postulated higher pressures required to permit liquid water on the surface. Adsorption of carbon dioxide on a Clay Mineral Society standard containing nontronite was studied over a wide range of pressures in the absence of water. Similar experiments were conducted on the pure nontronite extracted from the natural sample. Heating curves were obtained to help characterize and determine the purity of the clay sample.

  11. Effect of calcium on adsorption capacity of powdered activated carbon.

    PubMed

    Li, Gang; Shang, Junteng; Wang, Ying; Li, Yansheng; Gao, Hong

    2013-12-01

    We investigated the effect of calcium ion on the adsorption of humic acid (HA) (as a target pollutant) by powered activated carbon. The HA adsorption isotherms at different pH and kinetics of two different solutions including HA alone and HA doped Ca(2+), were performed. It was showed that the adsorption capacity of powdered activated carbon (PAC) for HA was markedly enhanced when Ca(2+) was doped into HA. Also, HA and Ca(2+) taken as nitrate were tested on the uptake of each other respectively and it was showed that the adsorbed amounts of both of them were significantly promoted when HA and calcium co-existed. Furthermore, the adsorbed amount of HA slightly decreased with the increasing of Ca(2+) concentration, whereas the amount of calcium increased with the increasing of HA concentration, but all above the amounts without addition. Finally, the change of pH before and after adsorption process is studied. In the two different solutions including HA alone and HA doped Ca(2+), pH had a small rise, but the extent of pH of later solution was bigger. PMID:25078809

  12. [Particulate matter adsorption capacity of 10 evergreen species in Beijing].

    PubMed

    Wang, Bing; Zhang Wei-kang; Niu, Xiang; Wang, Xiao-yan

    2015-02-01

    In the atmosphere, high concentrations of air particles PM (Particulate matter) cause not only environmental pollution, but also serious harm to human body. Green plants as an air filter, can effectively improve the air quality in urban and suburb, and protect human health. Therefore, it is necessary to understand the adsorption capacity of air particulate matter of different species. Based on aerosol generator (QRJZFSQ-I), the leaf surface of ten plants including six evergreen trees and four evergreen shrubs were measured to determine the atmosphere adsorption (TSP, PM10, PM2.5 and PM10) capacity in Beijing, the results showed that: (1) There was obvious difference in the PM adsorption capacity of the leaf surface of different species, the highest were Cedrus deodara and Pinus tabuliformis, which were (18.95 ± 0.71) μg x cm(-2) and (14.61 ± 0.78) μg x cm(-2) respectively, while Abiesfabri was the minimum, which was (8.02 ± 0.4) μg x cm(-2); (2) There was also difference in the per unit leaf area particulate adhesion ability among different tree species, the tree species with the strongest leaf PM10 adhesion ability were Pinus tabulformis and Cedrus deodara, those with the strongest leaf PM2.5 adhesion ability were Cedrus deodara, Juniperus procumbens , Juniperus chinensis cv. kaizuka and Pinus tabuliformis, while those with the strongest leaf PM10 adhesion ability were Cedrus deodara, Juniperus procumbens, Abies fabri and Pinus tabuliformis; (3) The proportions of particulate matters (PM10 and PM2.5) in TSP were different. PM10 had mainly two kinds of trends in April-June, one was firstly decreasing and then increasing, with the main tree type of the shrub species; and the other was increasing, with the main tree type of the tree species. But this change trend was not obvious in PM2.5. PMID:26031064

  13. COMPARISON OF PROCEDURES TO DETERMINE ADSORPTION CAPACITY OF VOLATILE ORGANIC COMPOUNDS ON ACTIVATED CARBON

    EPA Science Inventory

    Numerous volatile organic compounds (VOCs) are under regulatory consideration for inclusion in the National Primary Drinking Water Standards. Adsorption is a cost-effective treatment technology for control of VOCs. Adsorption capacities were determined for fifteen VOCs in distill...

  14. Determination of the adsorptive capacity and adsorption isotherm of vapor-phase mercury chloride on powdered activated carbon using thermogravimetric analysis

    SciTech Connect

    Hsun-Yu Lin; Chung-Shin Yuan; Wei-Ching Chen; Chung-Hsuang Hung

    2006-11-15

    This study investigated the use of thermogravimetric analysis (TGA) to determine the adsorptive capacity and adsorption isotherm of vapor-phase mercury chloride on powdered activated carbon (PAC). The technique is commonly applied to remove mercury-containing air pollutants from gas streams emitted from municipal solid waste incinerators. An alternative form of powdered activated carbon derived from a pyrolyzed tire char was prepared for use herein. The capacity of waste tire-derived PAC to adsorb vapor-phase HgCl{sub 2} was successfully measured using a self-designed TGA adsorption system. Experimental results showed that the maximum adsorptive capacities of HgCl{sub 2} were 1.75, 0.688, and 0.230 mg of HgCl{sub 2} per gram of powdered activated carbon derived from carbon black at 30, 70, and 150{sup o} for 500 {mu}g/m{sup 3} of HgCl{sub 2}, respectively. Four adsorption isotherms obtained using the Langmuir, Freundlich, Redlich-Peterson, and Brunauer-Emmett-eller (BET) models were used to simulate the adsorption of HgCl{sub 2}. The comparison of experimental data associated with the four adsorption isotherms indicated that BET fit the experimental results better than did the other isotherms at 30{sup o}, whereas the Freundlich isotherm fit the experimental results better at 70 and 150{sup o}. Furthermore, the calculations of the parameters associated with Langmuir and Freundlich isotherms revealed that the adsorption of HgCl{sub 2} by PAC-derived carbon black favored adsorption at various HgCl{sub 2} concentrations and temperatures. 35 refs., 7 figs., 3 tabs.

  15. Evaluation of Adsorption Capacity of Montmorillonite and Aluminium-pillared Clay for Pb2+, Cu2+ and Zn2.

    PubMed

    Humelnicu, Doina; Ignat, Maria; Suchea, Mirela

    2015-01-01

    Adsorption capacity of the two adsorbents was investigated as a function of contact time between adsorbent and heavy metal ions solutions, the initial heavy metals concentration of the synthetic wastewater, pH value, temperature and adsorbent mass. Preliminary experiments at different pH values between 2.0 and 7.0 were performed, and were observed that maximum adsorption occurs at pH 5 for copper (q(max) = 92.59 mg · g(–1)), 6.0 for lead (qmax = 97.08 mg · g(–1)) and 6.5 for zinc ions (q(max) = 73.52 mg · g(–1)), respectively. The sorption capacity of studied adsorbents for Pb(2+), Cu(2+) and Zn(2+) was calculated using Langmuir and Freundlich models. Thermodynamic parameters – enthalpy change (ΔH(0)), entropychange (ΔS(0)) and free energy (ΔG(0)) – were calculated for predicting the nature of adsorption. Scanning electron micrograph(SEM) revealed changes in the surface morphology of the adsorbent as a result of heavy metal ions adsorption.EDS characterization confirmed qualitatively the presence of adsorbed species in the samples. On the basis of the obtained results the adsorption it was proposed an ordered adsorption: Pb(2+), Cu(2+) and Zn(2+), on the sorbents we investigated. PMID:26680724

  16. High adsorption capacity of heavy metals on two-dimensional MXenes: an ab initio study with molecular dynamics simulation.

    PubMed

    Guo, Xun; Zhang, Xitong; Zhao, Shijun; Huang, Qing; Xue, Jianming

    2016-01-01

    Density functional theory (DFT) calculation is employed to study the adsorption properties of Pb and Cu on recently synthesized two-dimensional materials MXenes, including Ti3C2, V2C1 and Ti2C1. The influence of surface decoration with functional groups such as H, OH and F have also been investigated. Most of these studied MXenes exhibit excellent capability to adsorb Pb and Cu, especially the adsorption capacity of Pb on Ti2C1 is as high as 2560 mg g(-1). Both the binding energies and the adsorption capacities are sensitive to the functional groups attached to the MXenes' surface. Ab initio molecular dynamics (ab-init MD) simulation confirms that Ti2C1 remains stable at room temperature after adsorbing Pb atoms. Our calculations imply that these newly emerging two-dimensional MXenes are promising candidates for wastewater treatment and ion separation. PMID:26602974

  17. Preparation of mesoporous poly (acrylic acid)/SiO2 composite nanofiber membranes having adsorption capacity for indigo carmine dye

    NASA Astrophysics Data System (ADS)

    Xu, Ran; Jia, Min; Li, Fengting; Wang, Hongtao; Zhang, Bingru; Qiao, Junlian

    2012-03-01

    Mesoporous poly (acrylic acid)/SiO2 (PAA/SiO2) composite nanofiber membranes functionalized with mercapto groups were fabricated by a sol-gel electrospinning method, and their adsorption capacity for indigo carmine was investigated. The membranes were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, x-ray powder diffraction (XRD), and nitrogen adsorption-desorption measurement. SEM and TEM observation results showed that the PAA/SiO2 fibers had diameters between 400-800 nm and mesopores with an average pore size of 3.88 nm. The specific surface area of the mesoporous nanofiber membranes was 514.89 m2/g. The characteristic peaks for mercapto group vibration in FTIR and Raman spectra demonstrated that the mercapto groups have been incorporated into the silica skeleton. The adsorption isotherm data of indigo carmine on the membranes fit well with Redlich-Peterson model, and the maximum adsorption capacity calculated was 523.11 mg/g. It was found that the removal rate of indigo carmine by the membranes reached a maximum of 98% in 90 min and the adsorption kinetics followed a pseudo-second-order model. The high adsorption capacity of PAA/SiO2 nanofiber membrane makes it a promising adsorbent for indigo carmine removal from the wastewater.

  18. High-capacity adsorption of aniline using surface modification of lignocellulose-biomass jute fibers.

    PubMed

    Gao, Da-Wen; Hu, Qi; Pan, Hongyu; Jiang, Jiping; Wang, Peng

    2015-10-01

    Pyromellitic dianhydride (PMDA) modified jute fiber (MJF) were prepared with microwave treatment to generate a biosorbent for aniline removal. The characterization of the biosorbent was investigated by SEM, BET and FT-IR analysis to discuss the adsorption mechanism. The studies of various factors influencing the adsorption behavior indicated that the optimum dosage for aniline adsorption was 3g/L, the maximum adsorption capacity was observed at pH 7.0 and the adsorption process is spontaneous and endothermic. The aniline adsorption follows the pseudo second order kinetic model and Langmuir isotherm model. Moreover, the biosorbent could be regenerated through the desorption of aniline by using 0.5M HCl solution, and the adsorption capacity after regeneration is even higher than that of virgin MJF. All these results prove MJF is a promising adsorbent for aniline removal in wastewater. PMID:26172392

  19. Shape of the hydrogen adsorption regions of MOF-5 and its impact on the hydrogen storage capacity

    NASA Astrophysics Data System (ADS)

    Cabria, I.; López, M. J.; Alonso, J. A.

    2008-11-01

    The adsorption of molecular hydrogen on a metal-organic framework (MOF) material, MOF-5, has been studied using the density-functional formalism. The calculated potential-energy surface shows that there are two main adsorption regions: both near the OZn4 oxide cores at the vertices of the cubic skeleton of MOF-5. The adsorption energies in those regions are between 100 and 130 meV/molecule. Those adsorption regions have the shape of long, wide, and deep connected trenches and passage of the molecule between regions needs to surpass small barriers of 30-50 meV. The shape of these regions, and not only the presence of metal atoms, explains the large storage capacity measured for MOF-5. The elongated shape explains why some authors have previously identified only one type of adsorption site, associated to the Zn oxide core, and others identified two or three sites. One should consider adsorption regions rather than adsorption sites. A third region of adsorption is near the benzenic rings of the MOF-5. We have also analyzed the possibility of dissociative chemisorption. The chemisorption energy with respect to two separated H atoms is 1.33 eV/H atom; but, since dissociating the free molecule costs 4.75 eV, the physisorbed H2 molecule is more stable than the dissociated chemisorbed state by about 2 eV. Dissociation of the adsorbed molecule costs less energy, but the dissociation barrier is still high.

  20. Theoretical and practical aspects of chemical functionalization of carbon nanofibers (CNFs): DFT calculations and adsorption study.

    PubMed

    Rokhina, Ekaterina V; Lahtinen, Manu; Makarova, Katerina; Jegatheesan, Veeriah; Virkutyte, Jurate

    2012-06-01

    The nitric acid-functionalized commercial carbon nanofibers (CNFs) were comprehensively studied by instrumental (XRD, BET, SEM, TGA) and theoretical (DFT calculations) methods. The detailed surface study revealed the variation in the characteristics of functionalized CNFs, such as a decreased (up to 34%) surface area and impacted structural, electronic and chemical properties. The effects of functional groups were studied by comparison with pristine nanofibers. The results showed that the C-C bond lengths of the modified CNFs varied significantly. Chemical functionalization altered the frontier orbitals of the pristine material, and therefore altered the nature of their interactions with other substances. Moreover, the pristine and modified CNFs were tested for the removal of phenol from aqueous solutions. It was observed that surface modification tuned the adsorption capacity of carbon nanofibers (up to 0.35 mmol g(-1)), whereas original fibers did not demonstrate any adsorption capacity of phenol. PMID:22209137

  1. Quantum Biological Channel Modeling and Capacity Calculation

    PubMed Central

    Djordjevic, Ivan B.

    2012-01-01

    Quantum mechanics has an important role in photosynthesis, magnetoreception, and evolution. There were many attempts in an effort to explain the structure of genetic code and transfer of information from DNA to protein by using the concepts of quantum mechanics. The existing biological quantum channel models are not sufficiently general to incorporate all relevant contributions responsible for imperfect protein synthesis. Moreover, the problem of determination of quantum biological channel capacity is still an open problem. To solve these problems, we construct the operator-sum representation of biological channel based on codon basekets (basis vectors), and determine the quantum channel model suitable for study of the quantum biological channel capacity and beyond. The transcription process, DNA point mutations, insertions, deletions, and translation are interpreted as the quantum noise processes. The various types of quantum errors are classified into several broad categories: (i) storage errors that occur in DNA itself as it represents an imperfect storage of genetic information, (ii) replication errors introduced during DNA replication process, (iii) transcription errors introduced during DNA to mRNA transcription, and (iv) translation errors introduced during the translation process. By using this model, we determine the biological quantum channel capacity and compare it against corresponding classical biological channel capacity. We demonstrate that the quantum biological channel capacity is higher than the classical one, for a coherent quantum channel model, suggesting that quantum effects have an important role in biological systems. The proposed model is of crucial importance towards future study of quantum DNA error correction, developing quantum mechanical model of aging, developing the quantum mechanical models for tumors/cancer, and study of intracellular dynamics in general. PMID:25371271

  2. Modeling high adsorption capacity and kinetics of organic macromolecules on super-powdered activated carbon.

    PubMed

    Matsui, Yoshihiko; Ando, Naoya; Yoshida, Tomoaki; Kurotobi, Ryuji; Matsushita, Taku; Ohno, Koichi

    2011-02-01

    The capacity to adsorb natural organic matter (NOM) and polystyrene sulfonates (PSSs) on small particle-size activated carbon (super-powdered activated carbon, SPAC) is higher than that on larger particle-size activated carbon (powdered-activated carbon, PAC). Increased adsorption capacity is likely attributable to the larger external surface area because the NOM and PSS molecules do not completely penetrate the adsorbent particle; they preferentially adsorb near the outer surface of the particle. In this study, we propose a new isotherm equation, the Shell Adsorption Model (SAM), to explain the higher adsorption capacity on smaller adsorbent particles and to describe quantitatively adsorption isotherms of activated carbons of different particle sizes: PAC and SPAC. The SAM was verified with the experimental data of PSS adsorption kinetics as well as equilibrium. SAM successfully characterized PSS adsorption isotherm data for SPACs and PAC simultaneously with the same model parameters. When SAM was incorporated into an adsorption kinetic model, kinetic decay curves for PSSs adsorbing onto activated carbons of different particle sizes could be simultaneously described with a single kinetics parameter value. On the other hand, when SAM was not incorporated into such an adsorption kinetic model and instead isotherms were described by the Freundlich model, the kinetic decay curves were not well described. The success of the SAM further supports the adsorption mechanism of PSSs preferentially adsorbing near the outer surface of activated carbon particles. PMID:21172719

  3. Structural properties and adsorption capacity of holocellulose aerogels synthesized from an alkali hydroxide-urea solution

    NASA Astrophysics Data System (ADS)

    Kwon, Gu-Joong; Kim, Dae-Young; Hwang, Jae-Hyun; Kang, Joo-Hyon

    2014-05-01

    A tulip tree was used to synthesize a holocellulose aerogel from an aqueous alkali hydroxide-urea solution with the substitution of an organic solvent followed by freeze-drying. For comparison, the synthesized holocellulose aerogels were divided into two groups according to the source of the hydrogel, an upper suspended layer and a bottom concentrated layer of the centrifuged solution of cellulose and NaOH/urea solvents. We investigated the effects of the temperature of the pre-cooled NaOH/urea solution ( i.e., dissolution temperature) on the pore structure and the adsorption capacity of the holocellulose aerogel. A nano-fibrillar network structure of the holocellulose aerogel was observed, with little morphological difference in pore structure for different dissolution temperatures. Both micropores and mesopores were observed in the holocellulose aerogel. The specific surface area of the holocellulose aerogel was generally greater at lower dissolution temperatures. In a series of adsorption tests using methylene blue, the holocellulose aerogel showed the greatest adsorption capacity at the lowest dissolution temperature tested (-2°C). However, the dissolution temperature generally had little effect on the adsorption capacity. The holocellulose aerogel produced from the upper suspended layer of the centrifuged hydrogel solution showed a greater porosity and adsorption capacity than the one produced from the bottom concentrated layer. Overall, the aerogel made by utilizing a delignified tulip tree display a high surface area and a high adsorption property, indicating its possible application in eco-friendly adsorption materials.

  4. The Calculation of Adsorption Isotherms from Chromatographic Peak Shapes

    ERIC Educational Resources Information Center

    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. An investigation on the catalytic capacity of dolomite in transesterification and the calculation of kinetic parameters.

    PubMed

    Niu, Sheng-Li; Huo, Meng-Jia; Lu, Chun-Mei; Liu, Meng-Qi; Li, Hui

    2014-04-01

    The catalytic capacity of dolomite in transesterification was investigated and the kinetic parameters were calculated. The activated dolomites as transesterification catalyst were characterized by X-ray diffraction, nitrogen adsorption and desorption and Hammett indicator method, where the original dolomite was analyzed by thermogravimetric and X-ray fluorescence in advance. Its potential catalytic capacity was validated from aspects of the activated temperature and the reused property, where the reliability of the experimental system was also examined. Then, influences of the catalyst added amount, the mole ratio of methanol to oil, the transesterification temperature and the transesterification time on the catalytic capacity were investigated. Finally, kinetic parameters of the transesterification catalyzed by the activated dolomite were calculated. PMID:24583217

  6. Enhancement of the anionic dye adsorption capacity of clinoptilolite by Fe(3+)-grafting.

    PubMed

    Akgül, Murat

    2014-02-28

    In this paper, a batch system was applied to study the adsorption behavior of congo red (CR) on raw and modified clinoptilolites. Raw clinoptilolite (Raw-CL) was treated with Fe(NO3)3 in ethanol to obtain its iron-grafted form (Fe-CL). Adsorbents were characterized by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), energy dispersive X-ray spectroscopy (EDX), thermogravimetric/differential thermal analysis (TG/DTA), zeta-potential measurement and N2 gas adsorption-desorption techniques. Effects of the experimental parameters (initial pH, dye concentration, temperature and adsorption time) were investigated to find optimum conditions that result in highest adsorption capacity for CR removal. The obtained results suggest that the solution pH appears to be a key factor of the CR adsorption process. The maximum dye adsorption was achieved with Fe-CL adsorbent at pH ∼6.3 and the corresponding adsorption capacity was found to be 36.7mg/g, which is higher than that of its raw counterpart (16.9mg/g). A significant decrease in CR removal was given by Fe-CL between pH 7 and 11 opposite to Raw-CL which has nearly constant qe in the same pH range. The Fe(3+)-grafting increased the zeta potential of raw clinoptilolite, leading to a higher adsorption capacity compared to that of unfunctionalized adsorbent. Also, temperature change was found to have a significant effect on the adsorption process. PMID:24413045

  7. Correlation and prediction of adsorption capacity and affinity of aromatic compounds on carbon nanotubes.

    PubMed

    Wu, Wenhao; Yang, Kun; Chen, Wei; Wang, Wendi; Zhang, Jie; Lin, Daohui; Xing, Baoshan

    2016-01-01

    Adsorption of 22 nonpolar and polar aromatic compounds on 10 carbon nanotubes (CNTs) with various diameters, lengths and surface oxygen-containing group contents was investigated to develop predictive correlations for adsorption, using the isotherm fitting of Polanyi theory-based Dubinin-Ashtakhov (DA) model. Adsorption capacity of aromatic compounds on CNTs is negatively correlated with melting points of aromatic compounds, and surface oxygen-containing group contents and surface area ratios of mesopores to total pores of CNTs, but positively correlated with total surface area of CNTs. Adsorption affinity is positively correlated with solvatochromic parameters of aromatic compounds, independent of tube lengths and surface oxygen-containing group contents of CNTs, but negatively correlated with surface area ratios of mesopores to total pores of CNTs. The correlations of adsorption capacity and adsorption affinity with properties of both aromatic compounds and CNTs clearly have physical significance, can be used successfully with DA model to predict adsorption of aromatic compounds on CNTs from the well-known physiochemical properties of aromatic compounds (i.e., solvatochromic parameters, melting points) and CNTs (i.e., surface area and total acidic group contents), and thus can facilitate the environmental application of CNTs as sorbents and environmental risk assessment of both aromatic contaminants and CNTs. PMID:26521219

  8. Investigation of Mg modified mesoporous silicas and their CO 2 adsorption capacities

    NASA Astrophysics Data System (ADS)

    Zhao, Huiling; Yan, Wei; Bian, Zijun; Hu, Jun; Liu, Honglai

    2012-02-01

    CO 2 adsorption properties on Mg modified silica mesoporous materials were investigated. By using the methods of co-condensation, dispersion and ion-exchange, Mg 2+ was introduced into SBA-15 and MCM-41, and transformed into MgO in the calcination process. The basic MgO can provide active sites to enhance the acidic CO 2 adsorption capacity. To improve the amount and the dispersion state of the loading MgO, the optimized modification conditions were also investigated. The XRD and TEM characteristic results, as well as the CO 2 adsorption performance showed that the CO 2 adsorption capacity not only depended on the pore structures of MCM-41 and SBA-15, but also on the improvement of the dispersion state of MgO by modification. Among various Mg modified silica mesoporous materials, the CO 2 adsorption capacity increased from 0.42 mmol g -1 of pure silica SBA-15 to 1.35 mmol g -1 of Mg-Al-SBA-15-I1 by the ion-exchange method enhanced with Al 3+ synergism. Moreover, it also increased from 0.67 mmol g -1 of pure silica MCM-41 to 1.32 mmol g -1 of Mg-EDA-MCM-41-D10 by the dispersion method enhanced with the incorporation of ethane diamine. The stability test by 10 CO 2 adsorption/desorption cycles showed Mg-urea-MCM-41-D10 possessed quite good recyclability.

  9. Carbon nanotube membranes with ultrahigh specific adsorption capacity for water desalination and purification.

    PubMed

    Yang, Hui Ying; Han, Zhao Jun; Yu, Siu Fung; Pey, Kin Leong; Ostrikov, Kostya; Karnik, Rohit

    2013-01-01

    Development of technologies for water desalination and purification is critical to meet the global challenges of insufficient water supply and inadequate sanitation, especially for point-of-use applications. Conventional desalination methods are energy and operationally intensive, whereas adsorption-based techniques are simple and easy to use for point-of-use water purification, yet their capacity to remove salts is limited. Here we report that plasma-modified ultralong carbon nanotubes exhibit ultrahigh specific adsorption capacity for salt (exceeding 400% by weight) that is two orders of magnitude higher than that found in the current state-of-the-art activated carbon-based water treatment systems. We exploit this adsorption capacity in ultralong carbon nanotube-based membranes that can remove salt, as well as organic and metal contaminants. These ultralong carbon nanotube-based membranes may lead to next-generation rechargeable, point-of-use potable water purification appliances with superior desalination, disinfection and filtration properties. PMID:23941894

  10. Adsorption of selected pharmaceuticals and an endocrine disrupting compound by granular activated carbon. 1. Adsorption capacity and kinetics

    SciTech Connect

    Yu, Z.; Peldszus, S.; Huck, P.M.

    2009-03-01

    The adsorption of two representative PhACs (naproxen and carbamazepine) and one EDC (nonylphenol) were evaluated on two granular activated carbons (GAC) namely coal-based Calgon Filtrasorb 400 and coconut shell-based PICA CTIF TE. The primary objective was to investigate preloading effects by natural organic matter (NOM) on adsorption capacity and kinetics under conditions and concentrations (i.e., ng/L) relevant for drinking water treatment. Isotherms demonstrated that all compounds were significantly negatively impacted by NOM fouling. Adsorption capacity reduction was most severe for the acidic naproxen, followed by the neutral carbamazepine and then the more hydrophobic nonylphenol. The GAC with the wider pore size distribution had considerably greater NOM loading, resulting in lower adsorption capacity. Different patterns for the change in Freundlich KF and 1/n with time revealed different competitive mechanisms for the different compounds. Mass transport coefficients determined by short fixed-bed (SFB) tests with virgin and preloaded GAC demonstrated that film diffusion primarily controls mass transfer on virgin and preloaded carbon. Naproxen suffered the greatest deteriorative effect on kinetic parameters due to preloading, followed by carbamazepine, and then nonylphenol. A type of surface NOM/biofilm, which appeared to add an additional mass transfer resistance layer and thus reduce film diffusion, was observed. In addition, electrostatic interactions between NOM/biofilm and the investigated compounds are proposed to contribute to the reduction of film diffusion. A companion paper building on this work describes treatability studies in pilot-scale GAC adsorbers and the effectiveness of a selected fixed-bed model. 32 refs., 3 figs., 2 tabs.

  11. Non-contact analysis of the adsorptive ink capacity of nano silica pigments on a printing coating base.

    PubMed

    Jiang, Bo; Huang, Yu Dong

    2014-01-01

    Near infrared spectra combined with partial least squares were proposed as a means of non-contact analysis of the adsorptive ink capacity of recording coating materials in ink jet printing. First, the recording coating materials were prepared based on nano silica pigments. 80 samples of the recording coating materials were selected to develop the calibration of adsorptive ink capacity against ink adsorption (g/m2). The model developed predicted samples in the validation set with r2  = 0.80 and SEP = 1.108, analytical results showed that near infrared spectra had significant potential for the adsorption of ink capacity on the recording coating. The influence of factors such as recording coating thickness, mass ratio silica: binder-polyvinyl alcohol and the solution concentration on the adsorptive ink capacity were studied. With the help of the near infrared spectra, the adsorptive ink capacity of a recording coating material can be rapidly controlled. PMID:25329464

  12. Non-Contact Analysis of the Adsorptive Ink Capacity of Nano Silica Pigments on a Printing Coating Base

    PubMed Central

    Jiang, Bo; Huang, Yu Dong

    2014-01-01

    Near infrared spectra combined with partial least squares were proposed as a means of non-contact analysis of the adsorptive ink capacity of recording coating materials in ink jet printing. First, the recording coating materials were prepared based on nano silica pigments. 80 samples of the recording coating materials were selected to develop the calibration of adsorptive ink capacity against ink adsorption (g/m2). The model developed predicted samples in the validation set with r2  = 0.80 and SEP  = 1.108, analytical results showed that near infrared spectra had significant potential for the adsorption of ink capacity on the recording coating. The influence of factors such as recording coating thickness, mass ratio silica: binder-polyvinyl alcohol and the solution concentration on the adsorptive ink capacity were studied. With the help of the near infrared spectra, the adsorptive ink capacity of a recording coating material can be rapidly controlled. PMID:25329464

  13. Facile preparation of hierarchical hollow structure gamma alumina and a study of its adsorption capacity

    NASA Astrophysics Data System (ADS)

    Lan, Shi; Guo, Na; Liu, Lu; Wu, Xiaomin; Li, Linlin; Gan, Shucai

    2013-10-01

    The hierarchical shell and hollow core structure gamma alumina (γ-Al2O3) with high adsorption affinity toward organic pollutants was fabricated via a facile homogeneous precipitation method. The microstructure, morphology, and functional groups of the as-synthesized γ-Al2O3 were characterized in detail. The N2 adsorption-desorption measurement (BET) experimental result showed the surface area of γ-Al2O3 (Al90-600) is 320.6 m2/g and the average pore size is 17.8 nm. The effects of reaction parameters on the synthesis of hierarchical hollow structure were systematically investigated. The dye removal ability of this adsorbent was determined by batch adsorption procedure. The isotherms and kinetics of adsorption process were determined and analyzed in detail, which were found to obey the Langmuir isotherm model and the pseudo-second-order for both the Congo red (CR) and Methyl orange (MO). The maximum adsorption capacity of γ-Al2O3 for CR is 835.0 mg/g, which is higher than that of many other previously reported hierarchical structured adsorbents. This facile synthetic approach is a very promising way for the design and synthesis of the typical hierarchical hollow structure materials with powerful adsorption capacity for the removal of organic contaminants from wastewater.

  14. Synthesis, characterisation and methyl orange adsorption capacity of ferric oxide-biochar nano-composites derived from pulp and paper sludge

    NASA Astrophysics Data System (ADS)

    Chaukura, Nhamo; Murimba, Edna C.; Gwenzi, Willis

    2016-02-01

    A Fe2O3-biochar nano-composite (Fe2O3-BC) was prepared from FeCl3-impregnated pulp and paper sludge (PPS) by pyrolysis at 750 °C. The characteristics and methyl orange (MO) adsorption capacity of Fe2O3-BC were compared to that of unactivated biochar (BC). X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed the composite material was nano-sized. Fourier transform infrared (FTIR) spectroscopy revealed the presence of hydroxyl and aromatic groups on BC and on Fe2O3-BC, but Brunauer-Emmett-Teller (BET) surface area and Barrett-Joyner-Halenda (BJH) porosity were lower for Fe2O3-BC than BC. Despite the lower BET surface area and porosity of Fe2O3-BC, its MO adsorption capacity was 52.79 % higher than that of BC. The equilibrium adsorption data were best represented by the Freundlich model with a maximum adsorption capacity of 20.53 mg g-1 at pH 8 and 30 min contact time. MO adsorption obeyed pseudo-second-order kinetics for both BC and Fe2O3-BC with R 2 values of 0.996 and 0.999, respectively. Higher MO adsorption capacity for Fe2O3-BC was attributed to the hybrid nature of the nano-composites; adsorption occurred on both biochar matrix and Fe2O3 nanocrystals. Gibbs free energy calculations confirmed the adsorption is energetically favourable and spontaneous with a high preference for adsorption on both adsorbents. The nano-composite can be used for the efficient removal of MO (>97 %) from contaminated wastewater.

  15. Assessment of CO₂ adsorption capacity on activated carbons by a combination of batch and dynamic tests.

    PubMed

    Balsamo, Marco; Silvestre-Albero, Ana; Silvestre-Albero, Joaquín; Erto, Alessandro; Rodríguez-Reinoso, Francisco; Lancia, Amedeo

    2014-05-27

    In this work, batch and dynamic adsorption tests are coupled for an accurate evaluation of CO2 adsorption performance of three different activated carbons (AC) obtained from olive stones by chemical activation followed by physical activation with CO2 at varying times (i.e., 20, 40, and 60 h). Kinetic and thermodynamic CO2 adsorption tests from simulated flue gas at different temperatures and CO2 pressures are carried out under both batch (a manometric equipment operating with pure CO2) and dynamic (a lab-scale fixed-bed column operating with a CO2/N2 mixture) conditions. The textural characterization of the AC samples shows a direct dependence of both micropore and ultramicropore volume on the activation time; hence, AC60 has the higher contribution. The adsorption tests conducted at 273 and 293 K showed that when CO2 pressure is lower than 0.3 bar, the lower the activation time, the higher CO2 adsorption capacity; a ranking of ω(eq)(AC20) > ω(eq)(AC40) > ω(eq)(AC60) can be exactly defined when T = 293 K. This result is likely ascribed to the narrower pore size distribution of the AC20 sample, whose smaller pores are more effective for CO2 capture at higher temperature and lower CO2 pressure, the latter representing operating conditions of major interest for decarbonation of flue gas effluent. Moreover, the experimental results obtained from dynamic tests confirm the results derived from the batch tests in terms of CO2 adsorption capacity. It is important to highlight the fact that the adsorption of N2 on the synthesized AC samples can be considered to be negligible. Finally, the importance of proper analysis for data characterization and adsorption experimental results is highlighted for the correct assessment of the CO2 removal performance of activated carbons at different CO2 pressures and operating temperatures. PMID:24784997

  16. Fugitive gas adsorption capacity of biomass and animal-manure derived biochars

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This research characterized and investigated ammonia and hydrogen sulfide gas adsorption capacities of low- and high-temperature biochars made from wood shavings and chicken litter. The biochar samples were activated with steam or phosphoric acid. The specific surface areas and pore volumes of the a...

  17. Ammonia adsorption capacity of biomass and animal-manure derived biochars

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this research was to characterize and investigate ammonia and hydrogen sulfide gas adsorption capacities of low- and high-temperature biochars made from wood shavings and chicken litter. The biochar samples were activated with steam or phosphoric acid. The specific surface areas and...

  18. Effect of surface area and chemisorbed oxygen on the SO2 adsorption capacity of activated char

    USGS Publications Warehouse

    Lizzio, A.A.; DeBarr, J.A.

    1996-01-01

    The objective of this study was to determine whether activated char produced from Illinois coal could be used effectively to remove sulfur dioxide from coal combustion flue gas. Chars were prepared from a high-volatile Illinois bituminous coal under a wide range of pyrolysis and activation conditions. A novel char preparation technique was developed to prepare chars with SO2 adsorption capacities significantly greater than that of a commercial activated carbon. In general, there was no correlation between SO2 adsorption capacity and surface area. Temperature-programmed desorption (TPD) was used to determine the nature and extent of carbon-oxygen (C-O) complexes formed on the char surface. TPD data revealed that SO2 adsorption was inversely proportional to the amount of C-O complex. The formation of a stable C-O complex during char preparation may have served only to occupy carbon sites that were otherwise reactive towards SO2 adsorption. A fleeting C(O) complex formed during SO2 adsorption is postulated to be the reaction intermediate necessary for conversion of SO2 to H2SO4. Copyright ?? 1996 Elsevier Science Ltd.

  19. Nanosheet-structured boron nitride spheres with a versatile adsorption capacity for water cleaning.

    PubMed

    Liu, Fei; Yu, Jie; Ji, Xixi; Qian, Muqi

    2015-01-28

    Here, we report the synthesis of nanosheet-structured boron nitride spheres (NSBNSs) by a catalyzing thermal evaporation method from solid B powders. The NSBNSs consist of radially oriented ultrathin nanosheets with the sheet edges oriented on the surface. Formation of this unique structure occurs only at a certain reaction temperature. The diameter from 4 μm to 700 nm and the nanosheet thickness from 9.1 to 3.1 nm of the NSBNSs can be well-controlled by appropriately changing the mass ratio of boron powders and catalyst. The NSBNSs possess versatile adsorption capacity, exhibiting excellent adsorption performance for oil, dyes, and heavy metal ions from water. The oil uptake reaches 7.8 times its own weight. The adsorption capacities for malachite green and methylene blue are 324 and 233 mg/g, while those for Cu(2+), Pb(2+), and Cd(2+) are 678.7, 536.7, and 107.0 mg/g, respectively. The adsorption capacities of the NSBNSs for Cu(2+) and Pb(2+) are higher or much higher than those of the adsorbents reported previously. These results demonstrate the great potential of NSBNSs for water treatment and cleaning. PMID:25552343

  20. Foam-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

    2015-06-02

    Foam-based adsorbents and a related method of manufacture are provided. The foam-based adsorbents include polymer foam with grafted side chains and an increased surface area per unit weight to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. A method for forming the foam-based adsorbents includes irradiating polymer foam, grafting with polymerizable reactive monomers, reacting with hydroxylamine, and conditioning with an alkaline solution. Foam-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  1. Powder-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J.; Dai, Sheng; Oyola, Yatsandra

    2016-05-03

    A powder-based adsorbent and a related method of manufacture are provided. The powder-based adsorbent includes polymer powder with grafted side chains and an increased surface area per unit weight to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. A method for forming the powder-based adsorbent includes irradiating polymer powder, grafting with polymerizable reactive monomers, reacting with hydroxylamine, and conditioning with an alkaline solution. Powder-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  2. Effect of carboxyethylation degree on the adsorption capacity of Cu(II) by N-(2-carboxyethyl)chitosan from squid pens.

    PubMed

    Huang, Jun; Xie, Haihua; Ye, Hui; Xie, Tian; Lin, Yuecheng; Gong, Jinyan; Jiang, Chengjun; Wu, Yuanfeng; Liu, Shiwang; Cui, Yanli; Mao, Jianwei; Mei, Lehe

    2016-03-15

    Chitosan was prepared by N-deacetylation of squid pens β-chitin, and N-carboxyethylated chitosan (N-CECS) with different degrees of substitution (DS) were synthesized. DS values of N-CECS derivatives calculated by (1)H nuclear magnetic resonance (NMR) spectroscopy were 0.60, 1.02 and 1.46, respectively. The adsorption capacity of Cu(II) by N-CECS correlated well with the DS and pH ranging from 3.2 to 5.8. The maximum Cu(II) adsorption capacity (qm) of all three N-CECS at pH 5.4 was 207.5mg g(-1), which was 1.4-fold higher than that of chitosan. The adsorption equilibrium process was better described by the Langmuir than Freundlich isotherm model. Adsorption of Cu(II) ion onto N-CECS followed a pseudo-second order mechanism with chemisorption as the rate-limiting step. In a ternary adsorption system, the adsorption capacity of Cu(II) by N-CECS also presented high values, and qm for Cu(II), Cd(II), and Pb(II) were 150.2, 28.8, and 187.9mg g(-1), respectively. PMID:26794766

  3. All-electron scalar relativistic calculation of water molecule adsorption onto small gold clusters.

    PubMed

    Kuang, Xiang-Jun; Wang, Xin-Qiang; Liu, Gao-Bin

    2011-08-01

    An all-electron scalar relativistic calculation was performed on Au( n )H(2)O (n = 1-13) clusters using density functional theory (DFT) with the generalized gradient approximation at PW91 level. The calculation results reveal that, after adsorption, the small gold cluster would like to bond with oxygen and the H(2)O molecule prefers to occupy the single fold coordination site. Reflecting the strong scalar relativistic effect, Au( n ) geometries are distorted slightly but still maintain a planar structure. The Au-Au bond is strengthened and the H-O bond is weakened, as manifested by the shortening of the Au-Au bond-length and the lengthening of the H-O bond-length. The H-O-H bond angle becomes slightly larger. The enhancement of reactivity of the H(2)O molecule is obvious. The Au-O bond-lengths, adsorption energies, VIPs, HLGs, HOMO (LUMO) energy levels, charge transfers and the highest vibrational frequencies of the Au-O mode for Au( n )H(2)O clusters exhibit an obvious odd-even oscillation. The most favorable adsorption between small gold clusters and the H(2)O molecule takes place when the H(2)O molecule is adsorbed onto an even-numbered Au( n ) cluster and becomes an Au( n )H(2)O cluster with an even number of valence electrons. The odd-even alteration of magnetic moments is observed in Au( n )H(2)O clusters and may serve as material with a tunable code capacity of "0" and "1" by adsorbing a H(2)O molecule onto an odd or even-numbered small gold cluster. PMID:21140279

  4. Novel biosorbent with high adsorption capacity prepared by chemical modification of white pine (Pinus durangensis) sawdust. Adsorption of Pb(II) from aqueous solutions.

    PubMed

    Salazar-Rabago, J J; Leyva-Ramos, R

    2016-03-15

    The natural sawdust (NS) from white pine (Pinus durangensis) was chemically modified by a hydrothermal procedure using citric, malonic and tartaric acids. The adsorption capacity of modified sawdust (MS) towards Pb(II) was considerably enhanced due to the introduction of carboxylic groups on the surface of MS during the modification, and the adsorption capacity was almost linearly dependent on the concentration of carboxylic sites. The NS surface was acidic, and the MS surface became more acidic after the modification. At T = 25 °C and pH = 5, the maximum adsorption capacity of the optimal MS towards Pb(II) was 304 mg/g, which is exceptionally high compared to NS and other MS reported previously. The adsorption capacity of MS was considerably reduced from 304 to 154 mg/g by decreasing the solution pH from 5 to 3 due to electrostatic interactions. The adsorption of Pb(II) on MS was reversible at pH = 2, but not at pH = 5. The contribution percentage of ion exchange to the overall adsorption capacity ranged from 70 to 99% and 10-66% at the initial pH of 3 and 5, respectively. Hence, the adsorption of Pb(II) on MS was mainly due to ion exchange at pH = 3 and to both ion exchange and electrostatic attraction at pH = 5. PMID:26773434

  5. Strengthening of Graphene Aerogels with Tunable Density and High Adsorption Capacity towards Pb2+

    PubMed Central

    Han, Zhuo; Tang, Zhihong; Shen, Shuling; Zhao, Bin; Zheng, Guangping; Yang, Junhe

    2014-01-01

    Graphene aerogels (GAs) with high mechanical strength, tunable density and volume have been prepared only via soaking graphene hydrogels (GHs) in ammonia solution. The density and volume of the obtained GAs are controlled by adjusting the concentration of ammonia solution. Although volume of the GAs decreases with increasing the concentration of ammonia solution, its specific surface area maintains at about 350 m2 g−1, and the inner structure changes to radial after ammonia solution treatment. Thus, GAs are particularly suitable for the adsorption and energy storage applications owing to their high specific surface area and unique porous structure. The adsorption capacity of GAs for Pb2+ from aqueous solution maintains at about 80 mg g−1, which could reach as high as 5000 g m−3 per unit volume and they can be separated easily from water after adsorption. PMID:24848100

  6. Comparative study of carbon nanotubes and granular activated carbon: Physicochemical properties and adsorption capacities.

    PubMed

    Gangupomu, Roja Haritha; Sattler, Melanie L; Ramirez, David

    2016-01-25

    The overall goal was to determine an optimum pre-treatment condition for carbon nanotubes (CNTs) to facilitate air pollutant adsorption. Various combinations of heat and chemical pre-treatment were explored, and toluene was tested as an example hazardous air pollutant adsorbate. Specific objectives were (1) to characterize raw and pre-treated single-wall (SW) and multi-wall (MW) CNTs and compare their physical/chemical properties to commercially available granular activated carbon (GAC), (2) to determine the adsorption capacities for toluene onto pre-treated CNTs vs. GAC. CNTs were purified via heat-treatment at 400 °C in steam, followed by nitric acid treatment (3N, 5N, 11N, 16N) for 3-12 h to create openings to facilitate adsorption onto interior CNT sites. For SWNT, Raman spectroscopy showed that acid treatment removed impurities up to a point, but amorphous carbon reformed with 10h-6N acid treatment. Surface area of SWNTs with 3 h-3N acid treatment (1347 m(2)/g) was higher than the raw sample (1136 m(2)/g), and their toluene maximum adsorption capacity was comparable to GAC. When bed effluent reached 10% of inlet concentration (breakthrough indicating time for bed cleaning), SWNTs had adsorbed 240 mg/g of toluene, compared to 150 mg/g for GAC. Physical/chemical analyses showed no substantial difference for pre-treated vs. raw MWNTs. PMID:26476807

  7. A Porous Aromatic Framework Constructed from Benzene Rings Has a High Adsorption Capacity for Perfluorooctane Sulfonate

    PubMed Central

    Luo, Qin; Zhao, Changwei; Liu, Guixia; Ren, Hao

    2016-01-01

    A low-cost and easily constructed porous aromatic framework (PAF-45) was successfully prepared using the Scholl reaction. PAF-45 was, for the first time, used to remove perfluorooctane sulfonate (PFOS) from aqueous solution. Systematic experiments were performed to determine the adsorption capacity of PAF-45 for PFOS and to characterize the kinetics of the adsorption process. The adsorption of PFOS onto PAF-45 reached equilibrium in 30 min, and the adsorption capacity of PAF-45 for PFOS was excellent (5847 mg g−1 at pH 3). The amount of PFOS adsorbed by PAF-45 increased significantly as the cation (Na+, Mg2+, or Fe3+) concentration increased, which probably occurred because the cations enhanced the interactions between the negatively charged PFOS molecules and the positively charged PAF-45 surface. The cations Na+, Mg2+, and Fe3+ were found to form complexes with PFOS anions in solution. Density functional theory was used to identify the interactions between PFOS and Na+, Mg2+, and Fe3+. We expect that materials of the same type as PAF-45 could be useful adsorbents for removing organic pollutants from industrial wastewater and contaminated surface water. PMID:26843015

  8. A Porous Aromatic Framework Constructed from Benzene Rings Has a High Adsorption Capacity for Perfluorooctane Sulfonate.

    PubMed

    Luo, Qin; Zhao, Changwei; Liu, Guixia; Ren, Hao

    2016-01-01

    A low-cost and easily constructed porous aromatic framework (PAF-45) was successfully prepared using the Scholl reaction. PAF-45 was, for the first time, used to remove perfluorooctane sulfonate (PFOS) from aqueous solution. Systematic experiments were performed to determine the adsorption capacity of PAF-45 for PFOS and to characterize the kinetics of the adsorption process. The adsorption of PFOS onto PAF-45 reached equilibrium in 30 min, and the adsorption capacity of PAF-45 for PFOS was excellent (5847 mg g(-1) at pH 3). The amount of PFOS adsorbed by PAF-45 increased significantly as the cation (Na(+), Mg(2+), or Fe(3+)) concentration increased, which probably occurred because the cations enhanced the interactions between the negatively charged PFOS molecules and the positively charged PAF-45 surface. The cations Na(+), Mg(2+), and Fe(3+) were found to form complexes with PFOS anions in solution. Density functional theory was used to identify the interactions between PFOS and Na(+), Mg(2+), and Fe(3+). We expect that materials of the same type as PAF-45 could be useful adsorbents for removing organic pollutants from industrial wastewater and contaminated surface water. PMID:26843015

  9. A Porous Aromatic Framework Constructed from Benzene Rings Has a High Adsorption Capacity for Perfluorooctane Sulfonate

    NASA Astrophysics Data System (ADS)

    Luo, Qin; Zhao, Changwei; Liu, Guixia; Ren, Hao

    2016-02-01

    A low-cost and easily constructed porous aromatic framework (PAF-45) was successfully prepared using the Scholl reaction. PAF-45 was, for the first time, used to remove perfluorooctane sulfonate (PFOS) from aqueous solution. Systematic experiments were performed to determine the adsorption capacity of PAF-45 for PFOS and to characterize the kinetics of the adsorption process. The adsorption of PFOS onto PAF-45 reached equilibrium in 30 min, and the adsorption capacity of PAF-45 for PFOS was excellent (5847 mg g-1 at pH 3). The amount of PFOS adsorbed by PAF-45 increased significantly as the cation (Na+, Mg2+, or Fe3+) concentration increased, which probably occurred because the cations enhanced the interactions between the negatively charged PFOS molecules and the positively charged PAF-45 surface. The cations Na+, Mg2+, and Fe3+ were found to form complexes with PFOS anions in solution. Density functional theory was used to identify the interactions between PFOS and Na+, Mg2+, and Fe3+. We expect that materials of the same type as PAF-45 could be useful adsorbents for removing organic pollutants from industrial wastewater and contaminated surface water.

  10. Synthesis, fine structural characterization, and CO2 adsorption capacity of metal organic frameworks-74.

    PubMed

    Adhikari, Abhijit Krishna; Lin, Kuen-Song

    2014-04-01

    Two metal organic frameworks of MOF-74 group (zinc and copper-based) were successfully synthesized, characterized, and evaluated for CO2 adsorption. The both samples such as MOF-74(Zn) and MOF-74(Cu) were characterized with FE-SEM for morphology and particle size, XRD patterns for phase structure, FTIR for organic functional groups, nitrogen adsorption for pore textural properties, and X-ray absorption spectroscopy for fine structural parameters and oxidation states of central metal atoms. CO2 adsorption isotherms of MOF-74 samples were measured in a volumetric adsorption unit at 273 K and pressure up to 1.1 bar. The MOF-74(Zn) and MOF-74(Cu) adsorbents have the pore widths of 8.58 and 8.04 angstroms with the BET specific surface areas of 1,474 and 1,345 m2 g(-1), respectively. CO2 adsorption capacities of MOF-74(Zn) and MOF-74(Cu) were 4.10 and 3.38 mmol x g(-1), respectively measured at 273 K and 1.1 bar. The oxidation state of central atoms in MOF-74(Zn) was Zn(II) confirmed by XANES spectra while MOF-74(Cu) was composed of Cu(I) and Cu(II) central atoms. The bond distances of Zn--O and Cu--O were 1.98 and 1.94 angstroms, respectively. PMID:24734683

  11. Adsorption of O on Mo(110) surface from first-principles calculation

    SciTech Connect

    Zhou, Yungang; Zu, Xiaotao T.; Ni, Jiening; Gao, Fei

    2009-01-01

    First-principles calculations based on density functional theory (DFT) have been performed to study O adsorption in on-surface and subsurface sites. For different coverages, hollow site is found to be the most stable on-surface adsorption site. The subsurface adsorption at the bare Mo surface is found unfavored. The most stable subsurface site, the tetrahedral site, has a higher adsorption energy than on-surface sites. The pre-adsorbed O overlayer reduces the adsorption energy of subsurface O atoms, particularly for the octahedral site at p(2×2) phase. Also, vibrational frequencies, work-function and density of states are presented for O adsorption in on-surface sites.

  12. Radiotherapy cost-calculation and its impact on capacity planning.

    PubMed

    Lievens, Yolande; Slotman, Berend Jan

    2003-08-01

    The rapid rise in health care expenses has resulted in an increased interest in the cost of treatments from a cost-effectiveness point of view for management purposes and in a reimbursement setting. The economics of radiotherapy within the global context of health care, and more specifically of cancer therapy, are discussed in this review. Furthermore, the calculation of radiotherapy costs from an institutional perspective using activity-based costing and on capacity planning in radiotherapy - at the departmental as well as at the national level - by integrating cost, epidemiological and scientifico-technological data are focused on. PMID:19807460

  13. High-capacity adsorption of dissolved hexavalent chromium using amine-functionalized magnetic corn stalk composites.

    PubMed

    Song, Wen; Gao, Baoyu; Zhang, Tengge; Xu, Xing; Huang, Xin; Yu, Huan; Yue, Qinyan

    2015-08-01

    Easily separable amine-functionalized magnetic corn stalk composites (AF-MCS) were employed for effective adsorption and reduction of toxic hexavalent chromium [Cr(VI)] to nontoxic Cr(III). The saturated magnetization of AF-MCS reached 6.2emu/g, and as a result, it could be separated from aqueous solution by a magnetic process for its superparamagnetism. The studies of various factors influencing the sorption behavior indicated that the optimum AF-MCS dosage for Cr(VI) adsorption was 1g/L, and the maximum adsorption capacity was observed at pH 3.0. The chromium adsorption perfectly fitted the Langmuir isotherm model and pseudo second order kinetic model. Furthermore, characterization of AF-MCS was investigated by means of XRD, SEM, TEM, FT-IR, BET, VSM and XPS analysis to discuss the uptake mechanism. Basically, these results demonstrated that AF-MCS prepared in this work has shown its merit in effective removal of Cr(VI) and rapid separation from effluents simultaneously. PMID:25690680

  14. A review on modification methods to cellulose-based adsorbents to improve adsorption capacity.

    PubMed

    Hokkanen, Sanna; Bhatnagar, Amit; Sillanpää, Mika

    2016-03-15

    In recent decades, increased domestic, agricultural and industrial activities worldwide have led to the release of various pollutants, such as toxic heavy metals, inorganic anions, organics, micropollutants and nutrients into the aquatic environment. The removal of these wide varieties of pollutants for better quality of water for various activities is an emerging issue and a robust and eco-friendly treatment technology is needed for the purpose. It is well known that cellulosic materials can be obtained from various natural sources and can be employed as cheap adsorbents. Their adsorption capacities for heavy metal ions and other aquatic pollutants can be significantly affected upon chemical treatment. In general, chemically modified cellulose exhibits higher adsorption capacities for various aquatic pollutants than their unmodified forms. Numerous chemicals have been used for cellulose modifications which include mineral and organic acids, bases, oxidizing agent, organic compounds, etc. This paper reviews the current state of research on the use of cellulose, a naturally occurring material, its modified forms and their efficacy as adsorbents for the removal of various pollutants from waste streams. In this review, an extensive list of various cellulose-based adsorbents from literature has been compiled and their adsorption capacities under various conditions for the removal of various pollutants, as available in the literature, are presented along with highlighting and discussing the key advancement on the preparation of cellulose-based adsorbents. It is evident from the literature survey presented herein that modified cellulose-based adsorbents exhibit good potential for the removal of various aquatic pollutants. However, still there is a need to find out the practical utility of these adsorbents on a commercial scale, leading to the improvement of pollution control. PMID:26789698

  15. Preferential orientation of CO adsorption on Ni as determined by extended Hueckel calculations.

    NASA Technical Reports Server (NTRS)

    Robertson, J. C.; Wilmsen, C. W.

    1972-01-01

    The adsorption of CO on the nickel surface has been calculated using a modified extended Hueckel technique for a number of different orientations of the CO with respect to the nickel surface. The calculations show that double site adsorption with the CO molecule normal to the surface and the carbon atom closest to the metal gives the most stable configuration (2.57 eV). The single site absorbs with an energy of 2.39 eV. However, other configurations also give fairly large bonding energies. The CO normal to the surface with oxygen closest to the metal gives a heat of adsorption of 0.37 eV. Two-center adsorption with the CO axis parallel to the surface and the molecule symmetrically placed between the nearest neighbors gives a chemisorption energy of 1.34 eV. These values compare with an experimental value of 1.98 eV.

  16. Effects of Mn, Cu doping concentration to the properties of magnetic nanoparticles and arsenic adsorption capacity in wastewater

    NASA Astrophysics Data System (ADS)

    Thi, Tran Minh; Trang, Nguyen Thi Huyen; Van Anh, Nguyen Thi

    2015-06-01

    The research results of Fe3O4 and Mn, Cu doped Fe3O4 nanomaterials synthesized by a chemical method for As(III) wastewater treatment are presented in this paper. The X-ray diffraction patterns and transmission electron microscopy images showed that samples had the cubic spinel structure with the grain sizes were varied from 9.4 nm to 18.1 nm. The results of vibrating sample magnetometer measurements at room temperature showed that saturation magnetic moments of Fe1-xCuxFe2O4 and Fe1-xMnxFe2O4 samples decreased from 65.9 emu/g to 53.2 emu/g and 65.9 emu/g to 61.5 emu/g, respectively, with the increase of Cu, Mn concentrations from 0.0 to 0.15. The nitrogen adsorption-desorption isotherm of a typical Fe3O4 sample at 77 K was studied in order to investigate the surface and porous structure of nanoparticles by BET method. The specific surface area of Fe3O4 magnetic nanoparticles was calculated about of 100.2 m2/g. The pore size distribution of about 15-20 nm calculated by the BJH (Barrett, Joyner, and Halendar) method at a relative pressure P/P0 of about 1. Although the saturation magnetic moments of samples decreased when the increase of doping concentration, but the arsenic adsorption capacity of Cu doped Fe3O4 nanoparticles is better than that of Fe3O4 and Mn doped Fe3O4 nanoparticles in a solution with pH = 7. In the solution with a pH > 14, the arsenic adsorption of magnetic nanoparticles is insignificant.

  17. Adsorption capacities of activated carbons for geosmin and 2-methylisoborneol vary with activated carbon particle size: Effects of adsorbent and adsorbate characteristics.

    PubMed

    Matsui, Yoshihiko; Nakao, Soichi; Sakamoto, Asuka; Taniguchi, Takuma; Pan, Long; Matsushita, Taku; Shirasaki, Nobutaka

    2015-11-15

    The adsorption capacities of nine activated carbons for geosmin and 2-methylisoborneol (MIB) were evaluated. For some carbons, adsorption capacity substantially increased when carbon particle diameter was decreased from a few tens of micrometers to a few micrometers, whereas for other carbons, the increase of adsorption capacity was small for MIB and moderate for geosmin. An increase of adsorption capacity was observed for other hydrophobic adsorbates besides geosmin and MIB, but not for hydrophilic adsorbates. The parameter values of a shell adsorption model describing the increase of adsorption capacity were negatively correlated with the oxygen content of the carbon among other characteristics. Low oxygen content indicated low hydrophilicity. The increase of adsorption capacity was related to the hydrophobic properties of both adsorbates and activated carbons. For adsorptive removal of hydrophobic micropollutants such as geosmin, it is therefore recommended that less-hydrophilic activated carbons, such as coconut-shell-based carbons, be microground to a particle diameter of a few micrometers to enhance their equilibrium adsorption capacity. In contrast, adsorption by hydrophilic carbons or adsorption of hydrophilic adsorbates occur in the inner pores, and therefore adsorption capacity is unchanged by particle size reduction. PMID:26302219

  18. Adsorptive capacity and evolution of the pore structure of alumina on reaction with gaseous hydrogen fluoride.

    PubMed

    McIntosh, Grant J; Agbenyegah, Gordon E K; Hyland, Margaret M; Metson, James B

    2015-05-19

    Brunauer-Emmet-Teller (BET) specific surface areas are generally used to gauge the propensity of uptake on adsorbents, with less attention paid to kinetic considerations. We explore the importance of such parameters by modeling the pore size distributions of smelter grade aluminas following HF adsorption, an industrially important process in gas cleaning at aluminum smelters. The pore size distributions of industrially fluorinated aluminas, and those contacted with HF in controlled laboratory trials, are reconstructed from the pore structure of the untreated materials when filtered through different models of adsorption. These studies demonstrate the presence of three distinct families of pores: those with uninhibited HF uptake, kinetically limited porosity, and pores that are surface blocked after negligible scrubbing. The surface areas of the inaccessible and blocked pores will overinflate estimates of the adsorption capacity of the adsorbate. We also demonstrate, contrary to conventional understanding, that porosity changes are attributed not to monolayer uptake but more reasonably to pore length attenuation. The model assumes nothing specific regarding the Al2O3-HF system and is therefore likely general to adsorbate/adsorbent phenomena. PMID:25913681

  19. Volumetric Interpretation of Protein Adsorption: Capacity Scaling with Adsorbate Molecular Weight and Adsorbent Surface Energy

    PubMed Central

    Parhi, Purnendu; Golas, Avantika; Barnthip, Naris; Noh, Hyeran; Vogler, Erwin A.

    2009-01-01

    Silanized-glass-particle adsorbent capacities are extracted from adsorption isotherms of human serum albumin (HSA, 66 kDa), immunoglobulin G (IgG, 160 kDa), fibrinogen (Fib, 341 kDa), and immunoglobulin M (IgM, 1000 kDa) for adsorbent surface energies sampling the observable range of water wettability. Adsorbent capacity expressed as either mass-or-moles per-unit-adsorbent-area increases with protein molecular weight (MW) in a manner that is quantitatively inconsistent with the idea that proteins adsorb as a monolayer at the solution-material interface in any physically-realizable configuration or state of denaturation. Capacity decreases monotonically with increasing adsorbent hydrophilicity to the limit-of-detection (LOD) near τo = 30 dyne/cm (θ~65o) for all protein/surface combinations studied (where τo≡γlvocosθ is the water adhesion tension, γlvo is the interfacial tension of pure-buffer solution, and θ is the buffer advancing contact angle). Experimental evidence thus shows that adsorbent capacity depends on both adsorbent surface energy and adsorbate size. Comparison of theory to experiment implies that proteins do not adsorb onto a two-dimensional (2D) interfacial plane as frequently depicted in the literature but rather partition from solution into a three-dimensional (3D) interphase region that separates the physical surface from bulk solution. This interphase has a finite volume related to the dimensions of hydrated protein in the adsorbed state (defining “layer” thickness). The interphase can be comprised of a number of adsorbed-protein layers depending on the solution concentration in which adsorbent is immersed, molecular volume of the adsorbing protein (proportional to MW), and adsorbent hydrophilicity. Multilayer adsorption accounts for adsorbent capacity over-and-above monolayer and is inconsistent with the idea that protein adsorbs to surfaces primarily through protein/surface interactions because proteins within second (or higher

  20. Diamine-appended metal-organic frameworks: enhanced formaldehyde-vapor adsorption capacity, superior recyclability and water resistibility.

    PubMed

    Wang, Zhong; Wang, WenZhong; Jiang, Dong; Zhang, Ling; Zheng, Yali

    2016-07-28

    Capturing formaldehyde (HCHO) from indoor air with porous adsorbents still faces challenges due to their low uptake capacity, difficult regeneration, and especially, the sorption capacity reduction that is caused by the competitive adsorption of H2O when exposed to a humid atmosphere. In this work, MIL-101 is modified with ethylenediamine (ED) on its open-metal sites to substantially improve the HCHO adsorption properties. The HCHO uptake capacity of modified MIL-101 can be up to 5.49 mmol g(-1) in this study, which is among the highest-levels of various adsorbents reported thus far. Moreover, this modification both improved the material's recyclability and water resistibility, allowing for cyclic and selective tests with stable adsorption capacities, revealing the potential utility of amine-modified MOFs for indoor air purification. PMID:27338802

  1. Ultra-high adsorption capacity of zeolitic imidazole framework-67 (ZIF-67) for removal of malachite green from water.

    PubMed

    Lin, Kun-Yi Andrew; Chang, Hsuan-Ang

    2015-11-01

    Zeolitic imidazole frameworks (ZIFs), a new class of adsorbents, are proposed to adsorb Malachite Green (MG) in water. Particularly, ZIF-67 was selected owing to its stability in water and straightforward synthesis. The as-synthesized ZIF-67 was characterized and used to adsorb MG from water. Factors affecting the adsorption capacity were investigated including mixing time, temperature, the presence of salts and pH. The kinetics, adsorption isotherm and thermodynamics of the MG adsorption to ZIF-67 were also studied. The adsorption capacity of ZIF-67 for MG could be as high as 2430mgg(-1) at 20°C, which could be improved at the higher temperatures. Such an ultra-high adsorption capacity of ZIF-67 was almost 10-times of those of conventional adsorbents, including activated carbons and biopolymers. A mechanism for the high adsorption capacity was proposed and possibly attributed to the π-π stacking interaction between MG and ZIF-67. ZIF-67 also could be conveniently regenerated by washing with ethanol and the regeneration efficiency could remain 95% up to 4 cycles of the regeneration. ZIF-67 was also able to remove MG from the aquaculture wastewater, in which MG can be typically found. These features enable ZIF-67 to be one of the most effective and promising adsorbent to remove MG from water. PMID:25697373

  2. Study on the Adsorption Capacities for Airborne Particulates of Landscape Plants in Different Polluted Regions in Beijing (China)

    PubMed Central

    Zhang, Wei-Kang; Wang, Bing; Niu, Xiang

    2015-01-01

    Urban landscape plants are an important component of the urban ecosystem, playing a significant role in the adsorption of airborne particulates and air purification. In this study, six common landscape plants in Beijing were chosen as research subjects, and the adsorption capacities for each different plant leaf and the effects of the leaf structures for the adsorption capacities for particulates were determined. Preliminary results show that needle-leaved tree species adsorbed more airborne particulates than broad-leaved tree species for the same leaf area. Pinus tabuliformis exhibits the highest adsorption capacity, at 3.89 ± 0.026 μg·cm−2, almost two times as much as that of Populus tomentosa (2.00 ± 0.118 μg·cm−2). The adsorption capacities for PM10 of the same tree species leaves, in different polluted regions had significant differences, and the adsorption capacities for PM10 of the tree species leaf beside the Fifth Ring Road were higher than those of the tree species leaves in the Botanical Garden, although the adsorption capacities for PM2.5 of the same tree species in different polluted regions had no significant differences. By determining the soluble ion concentrations of the airborne particulates in two regions, it is suggested that the soluble ion concentrations of PM10 in the atmosphere in the Botanical Garden and beside the Fifth Ring Road have significant differences, while those of PM2.5 in the atmosphere had no significant differences. In different polluted regions there are significant adaptive changes to the leaf structures, and when compared with slightly polluted region, in the seriously polluted region the epidermis cells of the plant leaves shrinked, the surface textures of the leaves became rougher, and the stomas’ frequency and the pubescence length increased. Even though the plant leaves exposed to the seriously polluted region changed significantly, these plants can still grow normally and healthily. PMID:26287227

  3. Reservoir capacity estimates in shale plays based on experimental adsorption data

    NASA Astrophysics Data System (ADS)

    Ngo, Tan

    from different measurement techniques using representative fluids (such as CH4 and CO2) at elevated pressures, and the adsorbed density can range anywhere between the liquid and the solid state of the adsorbate. Whether these discrepancies are associated with the inherent heterogeneity of mudrocks and/or with poor data quality requires more experiments under well-controlled conditions. Nevertheless, it has been found in this study that methane GIP estimates can vary between 10-45% and 10-30%, respectively, depending on whether the free or the total amount of gas is considered. Accordingly, CO2 storage estimates range between 30-90% and 15-50%, due to the larger adsorption capacity and gas density at similar pressure and temperature conditions. A manometric system has been designed and built that allows measuring the adsorption of supercritical fluids in microporous materials. Preliminary adsorption tests have been performed using a microporous 13X zeolite and CO 2 as an adsorbing gas at a temperature of 25oC and 35oC and at pressures up to 500 psi. Under these conditions, adsorption is quantified with a precision of +/- 3%. However, relative differences up to 15-20% have been observed with respect to data published in the literature on the same adsorbent and at similar experimental conditions. While it cannot be fully explained with uncertainty analysis, this discrepancy can be reduced by improving experiment practice, thus including the application of a higher adsorbent's regeneration temperature, of longer equilibrium times and of a careful flushing of the system between the various experimental steps. Based on the results on 13X zeolite, virtual tests have been conducted to predict the performance of the manometric system to measure adsorption on less adsorbing materials, such as mudrocks. The results show that uncertainties in the estimated adsorbed amount are much more significant in shale material and they increase with increasing pressure. In fact, relative

  4. Understanding the Adsorption Mechanism of Xe and Kr in a Metal-Organic Framework from X-ray Structural Analysis and First- Principles Calculations

    SciTech Connect

    Ghose, Sanjit K.; Li, Yan; Yakovenko, Andrey; Dooryhee, Eric; Ehm, Lars; Ecker, Lynne E.; Dippel, Ann-Christin; Halder, Gregory J.; Strachan, Denis M.; Thallapally, Praveen K.

    2015-04-16

    Enhancement of adsorption capacity and separation of radioactive Xe/Kr at room temperature and above is a challenging problem. Here, we report a detailed structural refinement and analysis of the synchrotron X-ray powder diffraction data of Ni-DODBC metal organic framework with in situ Xe and Kr adsorption at room temperature and above. Our results reveal that Xe and Kr adsorb at the open metal sites, with adsorption geometries well reproduced by DFT calculations. The measured temperature-dependent adsorption capacity of Xe is substantially larger than that for Kr, indicating the selectivity of Xe over Kr and is consistent with the more negative adsorption energy (dominated by van der Waals dispersion interactions) predicted from DFT. Our results reveal critical structural and energetic information about host–guest interactions that dictate the selective adsorption mechanism of these two inert gases, providing guidance for the design and synthesis of new MOF materials for the separation of environmentally hazardous gases from nuclear reprocessing applications.

  5. The adsorptive capacity of vapor-phase mercury chloride onto powdered activated carbon derived from waste tires

    SciTech Connect

    Hsun-Yu Lin; Chung-Shin Yuan; Chun-Hsin Wu; Chung-Hsuang Hung

    2006-11-15

    Injection of powdered activated carbon (PAC) upstream of particulate removal devices (such as electrostatic precipitator and baghouses) has been used effectively to remove hazardous air pollutants, particularly mercury containing pollutants, emitted from combustors and incinerators. Compared with commercial PACs (CPACs), an alternative PAC derived from waste tires (WPAC) was prepared for this study. The equilibrium adsorptive capacity of mercury chloride (HgCl{sub 2}) vapor onto the WPAC was further evaluated with a self-designed bench-scale adsorption column system. The adsorption temperatures investigated in the adsorption column were controlled at 25 and 150{sup o}C. The superficial velocity and residence time of the flow were 0.01 m/sec and 4 sec, respectively. The adsorption column tests were run under nitrogen gas flow. Experimental results showed that WPAC with higher Brunauer Emmett Teller (BET) surface area could adsorb more HgCl{sub 2} at room temperature. The equilibrium adsorptive capacity of HgCl{sub 2} for WPAC measured in this study was 1.49 x 10{sup -1} mg HgCl{sub 2}/g PAC at 25{sup o}C with an initial HgCl{sub 2} concentration of 25 {mu}g/m{sup 3}. With the increase of adsorption temperature {le} 150{sup o}C, the equilibrium adsorptive capacity of HgCl{sub 2} for WPAC was decreased to 1.34 x 10{sup -1} mg HgCl{sub 2}/g PAC. Furthermore, WPAC with higher sulfur contents could adsorb even more HgCl{sub 2}. It was demonstrated that the mechanisms for adsorbing HgCl{sub 2} onto WPAC were physical adsorption and chemisorption at 25 and 150{sup o}C, respectively. 35 refs., 4 figs., 4 tabs.

  6. Lithium adsorption on graphite from density functional theory calculations.

    PubMed

    Valencia, Felipe; Romero, Aldo H; Ancilotto, Francesco; Silvestrelli, Pier Luigi

    2006-08-01

    The structural, energetic, and electronic properties of the Li/graphite system are studied through density functional theory (DFT) calculations using both the local spin density approximation (LSDA), and the gradient-corrected Perdew-Burke-Ernzerhof (PBE) approximation to the exchange-correlation energy. The calculations were performed using plane waves basis, and the electron-core interactions are described using pseudopotentials. We consider a disperse phase of the adsorbate comprising one Li atom for each 16 graphite surface cells, in a slab geometry. The close contact between the Li nucleus and the graphene plane results in a relatively large binding energy (larger than 1.1 eV). A detailed analysis of the electronic charge distribution, density difference distribution, and band structures indicates that one valence electron is entirely transferred from the atom to the surface, which gives rise to a strong interaction between the resulting lithium ion and the cloud of pi electrons in the substrate. We show that it is possible to explain the differences in the binding of Li, Na, and K adatoms on graphite considering the properties of the corresponding cation/aromatic complexes. PMID:16869593

  7. Reservoir capacity estimates in shale plays based on experimental adsorption data

    NASA Astrophysics Data System (ADS)

    Ngo, Tan

    from different measurement techniques using representative fluids (such as CH4 and CO2) at elevated pressures, and the adsorbed density can range anywhere between the liquid and the solid state of the adsorbate. Whether these discrepancies are associated with the inherent heterogeneity of mudrocks and/or with poor data quality requires more experiments under well-controlled conditions. Nevertheless, it has been found in this study that methane GIP estimates can vary between 10-45% and 10-30%, respectively, depending on whether the free or the total amount of gas is considered. Accordingly, CO2 storage estimates range between 30-90% and 15-50%, due to the larger adsorption capacity and gas density at similar pressure and temperature conditions. A manometric system has been designed and built that allows measuring the adsorption of supercritical fluids in microporous materials. Preliminary adsorption tests have been performed using a microporous 13X zeolite and CO 2 as an adsorbing gas at a temperature of 25oC and 35oC and at pressures up to 500 psi. Under these conditions, adsorption is quantified with a precision of +/- 3%. However, relative differences up to 15-20% have been observed with respect to data published in the literature on the same adsorbent and at similar experimental conditions. While it cannot be fully explained with uncertainty analysis, this discrepancy can be reduced by improving experiment practice, thus including the application of a higher adsorbent's regeneration temperature, of longer equilibrium times and of a careful flushing of the system between the various experimental steps. Based on the results on 13X zeolite, virtual tests have been conducted to predict the performance of the manometric system to measure adsorption on less adsorbing materials, such as mudrocks. The results show that uncertainties in the estimated adsorbed amount are much more significant in shale material and they increase with increasing pressure. In fact, relative

  8. Adsorption of reovirus to clay minerals: effects of cation-exchange capacity, cation saturation, and surface area.

    PubMed Central

    Lipson, S M; Stotzky, G

    1983-01-01

    The adsorption of reovirus to clay minerals has been reported by several investigators, but the mechanisms defining this association have been studied only minimally. The purpose of this investigation was to elucidate the mechanisms involved with this interaction. More reovirus type 3 was adsorbed, in both distilled and synthetic estuarine water, by low concentrations of montmorillonite than by comparable concentrations of kaolinite containing a mixed complement of cations on the exchange complex. Adsorption to the clays was essentially immediate and was correlated with the cation-exchange capacity of the clays, indicating that adsorption was primarily to negatively charged sites on the clays. Adsorption was greater with low concentrations of clays in estuarine water than in distilled water, as the higher ionic strength of the estuarine water reduced the electrokinetic potential of both clay and virus particles. The addition of cations (as chloride salts) to distilled water enhanced adsorption, with divalent cations being more effective than monovalent cations and 10(-2) M resulting in more adsorption than 10(-3) M. Potassium ions suppressed reovirus adsorption to montmorillonite, probably by collapsing the clay lattices and preventing the expression of the interlayer-derived cation-exchange capacity. More virus was adsorbed by montmorillonite made homoionic to various mono-, di-, and trivalent cations (except by montmorillonite homoionic to potassium) than by comparable concentrations of kaolinite homoionic to the same cations. The sequence of the amount of adsorption to homoionic montmorillonite was Al greater than Ca greater than Mg greater than Na greater than K; the sequence of adsorption to kaolinite was Na greater than Al greater than Ca greater than Mg greater than K. The constant partition-type adsorption isotherms obtained when the clay concentration was maintained constant and the virus concentration was varied indicated that a fixed proportion of the

  9. Enhancing adsorption capacity of toxic malachite green dye through chemically modified breadnut peel: equilibrium, thermodynamics, kinetics and regeneration studies.

    PubMed

    Chieng, Hei Ing; Lim, Linda B L; Priyantha, Namal

    2015-01-01

    Breadnut skin, in both its unmodified (KS) and base-modified (BM-KS) forms, was investigated for its potential use as a low-cost adsorbent for the removal of toxic dye, malachite green (MG). Characterization of the adsorbents was carried out using scanning electron microscope, X-ray fluorescence and Fourier transform infra-red spectroscopy. Batch adsorption experiments, carried out under optimized conditions, for the adsorption of MG were fitted using five isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich, Temkin and Sips) and six error functions to determine the best-fit model. The adsorption capacity was greatly enhanced when breadnut skin was chemically modified with NaOH, leading to an adsorption capacity of 353.0 mg g(-1), that was far superior to most reported adsorbents for the removal of MG. Thermodynamics studies indicated that the adsorption of MG was spontaneous on KS and BM-KS, and the reactions were endothermic and exothermic, respectively. Kinetics studies showed that both followed the pseudo-second order. Regeneration experiments on BM-KS indicated that its adsorption capacity was still maintained at>90% even after five cycles. It can be concluded that NaOH-modified breadfruit skin has great potential to be utilized in real-life application as a low-cost adsorbent for the removal of MG in wastewater treatment. PMID:25409587

  10. Metal and proton adsorption capacities of natural and cloned Sphagnum mosses.

    PubMed

    Gonzalez, Aridane G; Pokrovsky, Oleg S; Beike, Anna K; Reski, Ralf; Di Palma, Anna; Adamo, Paola; Giordano, Simonetta; Fernandez, J Angel

    2016-01-01

    Terrestrial mosses are commonly used as bioindicators of atmospheric pollution. However, there is a lack of standardization of the biomonitoring preparation technique and the efficiency of metal adsorption by various moss species is poorly known. This is especially true for in vitro-cultivated moss clones, which are promising candidates for a standardized moss-bag technique. We studied the adsorption of copper and zinc on naturally grown Sphagnum peat moss in comparison with in vitro-cultivated Sphagnum palustre samples in order to provide their physico-chemical characterization and to test the possibility of using cloned peat mosses as bioindicators within the protocol of moss-bag technique. We demonstrate that in vitro-grown clones of S. palustre exhibit acid-base properties similar to those of naturally grown Sphagnum samples, whereas the zinc adsorption capacity of the clones is approx. twice higher than that of the samples from the field. At the same time, the field samples adsorbed 30-50% higher amount of Cu(2+) compared to that of the clones. This contrast may be related to fine differences in the bulk chemical composition, specific surface area, morphological features, type and abundance of binding sites at the cell surfaces and in the aqueous solution of natural and cloned Sphagnum. The clones exhibited much lower concentration of most metal pollutants in their tissues relative to the natural samples thus making the former better indicators of low metal loading. Overall, in vitro-produced clones of S. palustre can be considered as an adequate, environmentally benign substitution for protected natural Sphagnum sp. samples to be used in moss-bags for atmospheric monitoring. PMID:26407060

  11. Estimating Prion Adsorption Capacity of Soil by BioAssay of Subtracted Infectivity from Complex Solutions (BASICS)

    PubMed Central

    Wyckoff, A. Christy; Lockwood, Krista L.; Meyerett-Reid, Crystal; Michel, Brady A.; Bender, Heather; VerCauteren, Kurt C.; Zabel, Mark D.

    2013-01-01

    Prions, the infectious agent of scrapie, chronic wasting disease and other transmissible spongiform encephalopathies, are misfolded proteins that are highly stable and resistant to degradation. Prions are known to associate with clay and other soil components, enhancing their persistence and surprisingly, transmissibility. Currently, few detection and quantification methods exist for prions in soil, hindering an understanding of prion persistence and infectivity in the environment. Variability in apparent infectious titers of prions when bound to soil has complicated attempts to quantify the binding capacity of soil for prion infectivity. Here, we quantify the prion adsorption capacity of whole, sandy loam soil (SLS) typically found in CWD endemic areas in Colorado; and purified montmorillonite clay (Mte), previously shown to bind prions, by BioAssay of Subtracted Infectivity in Complex Solutions (BASICS). We incubated prion positive 10% brain homogenate from terminally sick mice infected with the Rocky Mountain Lab strain of mouse-adapted prions (RML) with 10% SLS or Mte. After 24 hours samples were centrifuged five minutes at 200×g and soil-free supernatant was intracerebrally inoculated into prion susceptible indicator mice. We used the number of days post inoculation to clinical disease to calculate the infectious titer remaining in the supernatant, which we subtracted from the starting titer to determine the infectious prion binding capacity of SLS and Mte. BASICS indicated SLS bound and removed ≥ 95% of infectivity. Mte bound and removed lethal doses (99.98%) of prions from inocula, effectively preventing disease in the mice. Our data reveal significant prion-binding capacity of soil and the utility of BASICS to estimate prion loads and investigate persistence and decomposition in the environment. Additionally, since Mte successfully rescued the mice from prion disease, Mte might be used for remediation and decontamination protocols. PMID:23484043

  12. Porphyrin-Alkaline Earth MOFs with the Highest Adsorption Capacity for Methylene Blue.

    PubMed

    Hou, Yuxia; Sun, Junshan; Zhang, Daopeng; Qi, Dongdong; Jiang, Jianzhuang

    2016-04-25

    A series of four porphyrin-alkaline earth metal- organic frameworks [Mg(HDCPP)2 (DMF)2 ]n ⋅(H2 O)7 n (1), [Ca(HDCPP)2 (H2 O)2 ]n (DMF)1.5 n (2), [Sr(DCPP)(H2 O)(DMA)]n (3), and [Ba(DCPP)(H2 O)(DMA)]n (4) was isolated for the first time from solvothermal reaction between metal-free 5,15-di(4- carboxyphenyl)porphyrin (H2 DCPP) and alkaline earth ions. Single-crystal X-ray diffraction analysis reveals the 2D and 3D supramolecular network with periodic nanosized porosity for 1/2 and 3/4, respectively. The whole series of MOFs, in particular, compounds 1 and 2 with intrinsic low molecular formula weight, exhibit superior adsorption performance for methylene blue (MB) with excellent capture capacity as represented by the thus far highest adsorption amount of 952 mg g(-1) for 2 and good selectivity, opening a new way for the potential application of the main group metal-based MOFs. PMID:27002679

  13. Fiber-based adsorbents having high adsorption capacities for recovering dissolved metals and methods thereof

    DOEpatents

    Janke, Christopher J; Dai, Sheng; Oyola, Yatsandra

    2014-05-13

    A fiber-based adsorbent and a related method of manufacture are provided. The fiber-based adsorbent includes polymer fibers with grafted side chains and an increased surface area per unit weight over known fibers to increase the adsorption of dissolved metals, for example uranium, from aqueous solutions. The polymer fibers include a circular morphology in some embodiments, having a mean diameter of less than 15 microns, optionally less than about 1 micron. In other embodiments, the polymer fibers include a non-circular morphology, optionally defining multiple gear-shaped, winged-shaped or lobe-shaped projections along the length of the polymer fibers. A method for forming the fiber-based adsorbents includes irradiating high surface area polymer fibers, grafting with polymerizable reactive monomers, reacting the grafted fibers with hydroxylamine, and conditioning with an alkaline solution. High surface area fiber-based adsorbents formed according to the present method demonstrated a significantly improved uranium adsorption capacity per unit weight over existing adsorbents.

  14. Biomimetic mineralization of nano-sized, needle-like hydroxyapatite with ultrahigh capacity for lysozyme adsorption.

    PubMed

    Ma, Yi; Zhang, Juan; Guo, Shanshan; Shi, Jie; Du, Wenying; Wang, Zheng; Ye, Ling; Gu, Wei

    2016-11-01

    Because of its superior biocompatibility, hydroxyapatite (HA) has been widely exploited as a promising vehicle to deliver a broad range of therapeutics in a variety of biological systems. Herein, we report a biomimetic process to prepare nano-sized, colloidal stable HA with needle-like morphology by using carboxymethyl cellulose (CMC) as the template. It was revealed that the needle-like HA was transformed from the spherical amorphous calcium phosphate (ACP) nanoparticles after a 14-day period of aging under ambient conditions. The needle-like HA/CMC exhibited an ultra-high lysozyme adsorption capacity up to 930-940mg/g. Moreover, a sustained and pH-sensitive release of adsorbed lysozyme from HA/CMC was evidenced. Therefore, our biomimetic needle-like HA/CMC nanoparticles hold great potential in serving as an efficient carrier for the delivery and controlled release of lysozyme. PMID:27524053

  15. Assessing The Hydrogen Adsorption Capacity Of Single-Wall Carbon Nanotube / Metal Composites

    NASA Astrophysics Data System (ADS)

    Heben, Michael J.; Dillon, Anne C.; Gilbert, Katherine E. H.; Parilla, Philip A.; Gennett, Thomas; Alleman, Jeffrey L.; Hornyak, G. Louis; Jones, Kim M.

    2003-07-01

    Carefully controlled and calibrated experiments indicate a maximum capacity for adsorption of hydrogen on SWNTs is ˜8 wt% under room temperature and pressure conditions. Samples displaying this maximum value were prepared by sonicating purified SWNTs in a dilute nitric acid solution with a high-energy probe. The process cuts the SWNT into shorter segments and introduces a Ti-6Al-4V alloy due to the disintegration of the ultrasonic probe. The Ti-6Al-4V alloy is a well-known metal hydride and its contribution to the measured hydrogen uptake was accounted for in order to assess the amount of hydrogen stored on the SWNT fraction. The principal purpose of this paper is to present key details associated with the measurement procedures in order to illustrate the degree of rigor with which the findings were obtained.

  16. Dissociative versus molecular adsorption of phenol on Si(100)2×1 : A first-principles calculation

    NASA Astrophysics Data System (ADS)

    Carbone, Marilena; Meloni, Simone; Caminiti, Ruggero

    2007-08-01

    We investigated the competitive adsorption of a bifunctional molecule, phenol, on Si(100)2×1 by ab initio calculations. We performed geometry optimizations of phenol adsorbed either molecularly or dissociatively, on five possible sites (top, bridge, valley bridge, cave, and pedestal), in the low coverage regime. We found that the dissociative adsorption of phenol on top of a silicon dimer is the most favorable adsorption configuration. In the group of dissociative adsorption the phenol initially placed on the bridge or the valley-bridge sites ends up as a toplike local minima. The pedestal and cave sites remain as low-adsorption energy “open” sites. In the group of molecular adsorption, a higher adsorption energy is associated to the adsorption through an addition reaction and loss of the aromatic character (bridge, valley-bridge, and pedestal sites). Standard butterfly or diagonal butterfly are the corresponding optimized geometries. Retention of aromatic character and lower adsorption energy are associated to the adsorption on the top and cave sites. The ordering of adsorption sites according to the adsorption energy shows a mixture of the dissociative and the molecular sites. In the case of adsorption on the top site, the adsorption energies after a rotation of the phenoxy fragment along the bonding axis and hydrogen migration on the surface are very similar. The bend of the phenoxy fragment on the surface, instead, is not favored (the adsorption energy is 1.004eV lower compared to the vertical position). Different electron density maps were calculated for different adsorption sites and modes. Finally, we investigated the possibility that molecularly adsorbed phenol behaves as a precursor for the dissociative one by nudged elastic band calculations. We found a barrier of the same order of magnitude of the thermodynamic energy at room temperature for the conversion of the valley-bridge molecular into the top dissociative site.

  17. Copper Accumulation, Availability and Adsorption Capacity in Sandy Soils of Vineyards with Different Cultivation Duration

    NASA Astrophysics Data System (ADS)

    Mallmann, F. J. K.; Miotto, A.; Bender, M. A.; Gubiani, E.; Rheinheimer, D. D. S.; Kaminski, J.; Ceretta, C. A.; Šimůnek, J.

    2015-12-01

    Bordeaux mixture is a copper-based (Cu) fungicide and bactericide applied in vineyards to control plant diseases. Since it is applied several times per year, it accumulates in large quantities on plants and in soil. This study evaluates the Cu accumulation in, and desorption kinetics and adsorption capability of a sandy Ultisol in a natural field and in 3 vineyards for 5 (V1), 11 (V2), and 31 (V3) years in South of Brazil. Soil samples were collected in 8 depths (0-60 cm) of all four soil profiles, which all displayed similar soil properties. The following soil properties were measured: pH, organic matter (OM), soil bulk density, Cu total concentration, and Cu desorption and adsorption curves. A two first-order reactions model and the Langmuir isotherm were fitted to the desorption and adsorption curves, respectively. An increase in the total mass of Cu in the vineyards followed a linear regression curve, with an average annual increase of 7.15 kg ha-1. Cu accumulated down to a depth of 5, 20, and 30 cm in V1, V2 and V3, respectively, with the highest Cu content reaching 138.4 mg kg-1 in the 0-5 cm soil layer of V3. Cu desorption parameters showed a high correlation with its total concentration. Approximately 57 and 19% of total Cu were immediately and slowly available, respectively, indicating a high potential for plant absorption and/or downward movement. Cu concentrations extracted by EDTA from soil layers not affected by anthropogenic Cu inputs were very low. The maximum Cu adsorption capacity of the 0-5 and 5-10 cm soil layers increased with the vineyard age, reaching concentrations higher than 900 mg kg-1. This increase was highly related to OM and pH, which both increased with cultivation duration. Despite of low clay content of these soils, there is low risk of groundwater Cu contamination for actual conditions. However, high Cu concentrations in the surface layer of the long-term vineyards could cause toxicity problems for this and for companion crops.

  18. Ab-initio calculation of C and CO adsorption on the Co (110) surface

    NASA Astrophysics Data System (ADS)

    Chin, Shin-Liang; Ionescu, Adrian; Reeve, Robert M.; Cheng, Jun; Barnes, Crispin H. W.

    2013-02-01

    The adsorption energies, structural, electrical and magnetic properties of adsorption of C and CO on the fcc Co (110) surface have been investigated using density functional theory. The preferential adsorption site for the fcc Co (110) has been calculated. For the case of C adsorption, the preferential adsorption site is the long-bridge for both the 0.5 and 1.0 monolayers (ML) coverages. Whilst for the CO case, the preferential adsorption sites are at the atop and short-bridge site for 0.5 and 1.0 ML coverages respectively. Structurally, the first two layers of the bare Co (110) surface expand whereas the second and third layers contract. Upon adsorption of either C or CO, however, the degree of expansion and compression reduces. Magnetically, the adsorbates were found to couple ferrimagnetically to the surface and suppress the magnetic moment of the Co layers beneath them. The C adsorbate has a much stronger suppression effect as compared to the CO adsorbate. At 0.5 ML coverage, the C adatom suppresses up to 47% of the magnetic moment in the surface layer compared to a clean Co (110), whereas the CO adsorbate only suppresses up to 16%. For the 1.0 ML coverage case, both the C and CO adsorbates suppress almost equivalently well at 68% and 63% respectively. We also report on a correlation between the amount of charge transfer and the degree of suppression of the surface magnetic moment. Finally, we observe that the electronic charge is shared in the [001] direction for the C adsorbate and in the [11¯0] direction for the CO adsorbate. This anisotropy of surface bonding, in conjunction with the ligand field theory, explains the mechanism behind the spin reorientation transition that occurs uniquely on the CO/Co(110) system.

  19. Cu(II) and Zn(II) adsorption capacity of three different clay liner materials.

    PubMed

    Musso, T B; Parolo, M E; Pettinari, G; Francisca, F M

    2014-12-15

    Sorption of Cu(II) and Zn(II) on three natural clays meeting the international requirements for use as liners was evaluated by means of batch tests. The purpose of this research was to determine the retention capacities of the clays for metal cations commonly present in urban solid waste leachates. The pH and ionic strength conditions were set at values frequently found in real leachates. The changes observed in the XRD patterns and FTIR spectra upon adsorption can be considered an evidence of clay-metal electrostatic interaction. The Langmuir model was found to best describe the sorption processes, offering maximum sorption capacities from 8.16 to 56.89 mg/g for Cu(II) and from 49.59 to 103.83 mg/g for Zn(II). All samples remove more Zn(II) than Cu(II), which may be related to the different geometry of the hydrated Cu(II) cation. The total amount of metal sorption was strongly influenced by the total specific surface area, the presence of carbonates and the smectite content of the clays. In addition to their known quality as physical barriers, the adsorbed amounts obtained indicate the suitability of the tested clays to contribute to the retardation of Cu(II) and Zn(II) transport through clay liners. PMID:25156265

  20. Preparation of agricultural residue anion exchangers and its nitrate maximum adsorption capacity.

    PubMed

    Orlando, U S; Baes, A U; Nishijima, W; Okada, M

    2002-09-01

    Anion exchangers were prepared from different agricultural residues (AR) after reaction with epichlorohydrin and dimethylamine in the presence of pyridine and N,N-dimethylformamide (EDM method). Agricultural residues anion exchangers (AR-AE) produced by the EDM method were inexpensive and showed almost the same NO3- removal capacities as Amberlite IRA-900. AR-AE produced from AR with higher hemicelluloses, lignin, ash and extractive contents resulted in the lower yields. Sugarcane bagasse with the highest alpha-cellulose contents of 51.2% had the highest yield (225%) and lowest preparation cost. The highest maximum adsorption capacity (Qmax) for nitrate was obtained from rice hull (1.21 mmol g(-1)) and pine bark natural exchangers (1.06 mmol g(-1)). No correlation was found between Qmax and alpha-cellulose content in the original AR. AR-AE produced from different AR demonstrated comparable Qmax due to the removal of non-active compounds such as extractives, lignin and hemicelluloses from AR during the preparation process. Similar preparation from pure cellulose and pure alkaline lignin demonstrated that the EDM method could not produce anion exchangers from pure lignin due to its solubilization after the reaction with epichlorohydrin. PMID:12227509

  1. Surface-Energetic Heterogeneity of Nanoporous Solids for CO2 and CO Adsorption: The Key to an Adsorption Capacity and Selectivity at Low Pressures.

    PubMed

    Kim, Moon Hyeon; Cho, Il Hum; Choi, Sang Ok; Lee, In Soo

    2016-05-01

    This study has been focused on surface energetic heterogeneity of zeolite (H-mordenite, "HM"), activated carbon ("RB2") and metal-organic framework family ("Z1200") materials and their isotherm features in adsorption of CO2 and CO at 25 degrees C and low pressures ≤ 850 Torr. The nanoporous solids showed not only distinctive shape of adsorption isotherms for CO2 with relatively high polarizability and quadrupole moment but also different capacities in the CO2 adsorption. These differences between the adsorbents could be well correlated with their surface nonuniformity. The most heterogeneous surfaces were found with the HM that gave the highest CO2 uptake at all pressures allowed, while the Z1200 consisted of completely homogeneous surfaces and even CO2 adsorption linearly increased with pressure. An intermediate character was indicated on the surface of RB2 and thus this sorbent possessed isotherm features between the HM and Z1200 in CO2 adsorption. Such different surface energetics was fairly consistent with changes in CO2/CO selectivity on the nanoporous adsorbents up to equilibrated pressures near 850 Torr. PMID:27483776

  2. Surface complexation modeling calculation of Pb(II) adsorption onto the calcined diatomite

    NASA Astrophysics Data System (ADS)

    Ma, Shu-Cui; Zhang, Ji-Lin; Sun, De-Hui; Liu, Gui-Xia

    2015-12-01

    Removal of noxious heavy metal ions (e.g. Pb(II)) by surface adsorption of minerals (e.g. diatomite) is an important means in the environmental aqueous pollution control. Thus, it is very essential to understand the surface adsorptive behavior and mechanism. In this work, the Pb(II) apparent surface complexation reaction equilibrium constants on the calcined diatomite and distributions of Pb(II) surface species were investigated through modeling calculations of Pb(II) based on diffuse double layer model (DLM) with three amphoteric sites. Batch experiments were used to study the adsorption of Pb(II) onto the calcined diatomite as a function of pH (3.0-7.0) and different ionic strengths (0.05 and 0.1 mol L-1 NaCl) under ambient atmosphere. Adsorption of Pb(II) can be well described by Freundlich isotherm models. The apparent surface complexation equilibrium constants (log K) were obtained by fitting the batch experimental data using the PEST 13.0 together with PHREEQC 3.1.2 codes and there is good agreement between measured and predicted data. Distribution of Pb(II) surface species on the diatomite calculated by PHREEQC 3.1.2 program indicates that the impurity cations (e.g. Al3+, Fe3+, etc.) in the diatomite play a leading role in the Pb(II) adsorption and dominant formation of complexes and additional electrostatic interaction are the main adsorption mechanism of Pb(II) on the diatomite under weak acidic conditions.

  3. Illite spatial distribution controls Cr(VI) adsorption capacity and kinetics

    NASA Astrophysics Data System (ADS)

    WANG, L.; Li, L.

    2013-12-01

    In the natural surbsurface, clays typically are the major sorbing minerals for contaminants. Clays are known to distribute unevenly with low permeability 'clay' zones, which can have significant impacts on the sorption of contaminants. In this work, the effects of illite spatial distribution on Cr(VI) adsorption was examined using column experiments and reactive transport modeling. Three columns were set up with the same volume fraction of illite (10%). The Mixed column has illite evenly distributed within a quartz matrix; the Flow-transverse column has illite distributed in one horizontal zone in the direction that is perpendicular to the main flow; the Flow-parallel column has illite distributed in one cylindrical zone in the direction parallel to the main flow direction. Cr(VI) adsorption experiments were carried out under flow velocities of 0.58, 2.93, and 14.67 m/day. Two-dimensional reactive transport modeling was used to understand the role of illite distribution in determining Cr(VI) sorption capacity and kinetics. The result showed that illite spatial distribution strongly influence Cr(VI) sorption, the extent of which depend on the flow conditions . The Cr(VI) sorption kinectics was influenced by the permeability contrast and the preferential flow paths were taken place in high permeability zones. Under the flow rate of 0.58 m/day, the Cr(VI) adsorption in the Mixed and Flow-transverse columns was very similar, showing similar breakthrough time and sorption capacity. In contrast, an early breakthrough and an extended of Cr(VI) occured in the Flow-parallel column. The 2D reactive transport model showed that the inlet fluids flow through the quartz zone and bypass the lower permeability illite zone. Cr(VI) was first adsorbed on the illite-quartz interface early on and gradually diffuse into the illite zone over time. At the flow velocity of 2.93 m/day, the difference among the three columns was similar to the difference at the flow rate of 0.58 m/day. At

  4. First principles calculations of the Sc adsorption on Si(001)-c(2 × 4)

    NASA Astrophysics Data System (ADS)

    Romero, M. T.; Cocoletzi, Gregorio H.; Takeuchi, Noboru

    2012-09-01

    We have investigated the energetics and the atomic structure of the adsorption of Sc on the Si(001)-c(2 × 4) surface using first principles total energy calculations, within the periodic density functional. The Sc adsorption has been studied at high symmetry sites considering different concentrations. We have first explored the one atom case and then increased the coverage up to a 0.25 of a monolayer of Sc. For the adsorption of one Sc atom we have obtained that the most stable configuration corresponds to the adsorption in the trench between two Si dimers, at the C1 (cave) site. The interaction of the adsorbed Sc with the Si dimers induces a decrease of the dimers buckling amplitude. On the other hand Si dimers without interaction with the adsorbate have buckling amplitudes similar to those of the clean Si surface. When the Sc coverage is increased to two Sc atoms, the most stable structure corresponds to the adsorption at two consecutive V (valley-bridge) sites along the trench between Si dimers, resulting in the weakening of some of the Si dimers bonds. This result indicates that the formation of one dimensional Sc chains on the silicon surface is energetically and kinetically favorable.

  5. EFFECT OF MOLECULAR OXYGEN ON ADSORPTIVE CAPACITY AND EXTRACTION EFFICIENCY OF GRANULATED ACTIVATED CARBON FOR THREE ORTHO-SUBSTITUTED PHENOLS

    EPA Science Inventory

    Adsorptive capacity of activated carbon for several organic compounds was found to be strongly influenced by the presence of molecular oxygen. This influence is manifested by the polymerization of adsorbate on the surface of activated carbon. As a result, GAC exhibits much high...

  6. EFFECT OF HEAT ON THE ADSORPTION CAPACITY OF AN ACTIVATED CARBON FOR DECOLORIZING/DEODORIZING YELLOW ZEIN

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Freundlich model was evaluated for use to assess the effect of heat on the adsorption capacity of an activated carbon for decolorizing/deodorizing corn zein. Because zein protein and its color/odor components are all adsorbed by activated carbon, a method to monitor their removal was needed. Y...

  7. Efficient Removal of Co2+ from Aqueous Solution by 3-Aminopropyltriethoxysilane Functionalized Montmorillonite with Enhanced Adsorption Capacity.

    PubMed

    Huang, Zhujian; Wu, Pingxiao; Gong, Beini; Dai, Yaping; Chiang, Pen-Chi; Lai, Xiaolin; Yu, Guangwei

    2016-01-01

    To achieve a satisfactory removal efficiency of heavy metal ions from wastewater, silane-functionalized montmorillonite with abundant ligand-binding sites (-NH2) was synthesized as an efficient adsorbent. Ca-montmorillonite (Ca-Mt) was functionalized with 3-aminopropyl triethoxysilane (APTES) to obtain the APTES-Mt products (APTES1.0CEC-Mt, APTES2.0CEC-Mt, APTES3.0CEC-Mt, APTES4.0CEC-Mt) with enhanced adsorption capacity for Co2+. The physico-chemical properties of the synthesized adsorbents were characterized by spectroscopic and microscopic methods, and the results demonstrated that APTES was successfully intercalated into the gallery of Ca-Mt or grafted onto the surface of Ca-Mt through Si-O bonds. The effect of solution pH, ionic strength, temperature, initial concentrations and contact time on adsorption of Co2+ by APTES-Mt was evaluated. The results indicated that adsorption of Co2+ onto Ca-Mt, APTES1.0CEC-Mt and APTES2.0CEC-Mt can be considered to be a pseudo-second-order process. In contrast, adsorption of Co2+ onto APTES3.0CEC-Mt and APTES4.0CEC-Mt fitted well with the pseudo-first-order kinetics. The adsorption isotherms were described by the Langmuir model, and the maximum adsorption capacities of APTES1.0CEC-Mt, APTES2.0CEC-Mt, APTES3.0CEC-Mt and APTES4.0CEC-Mt were 25.1, 33.8, 61.6, and 61.9 mg·g-1, respectively. In addition, reaction temperature had no impact on the adsorption capacity, while both the pH and ionic strength significantly affected the adsorption process. A synergistic effect of ion exchange and coordination interactions on adsorption was observed, thereby leading to a significant enhancement of Co2+ adsorption by the composites. Thus, APTES-Mt could be a cost-effective and environmental-friendly adsorbent, with potential for treating Co2+-rich wastewater. PMID:27448094

  8. Efficient Removal of Co2+ from Aqueous Solution by 3-Aminopropyltriethoxysilane Functionalized Montmorillonite with Enhanced Adsorption Capacity

    PubMed Central

    Huang, Zhujian; Gong, Beini; Dai, Yaping; Chiang, Pen-Chi; Lai, Xiaolin; Yu, Guangwei

    2016-01-01

    To achieve a satisfactory removal efficiency of heavy metal ions from wastewater, silane-functionalized montmorillonite with abundant ligand-binding sites (-NH2) was synthesized as an efficient adsorbent. Ca-montmorillonite (Ca-Mt) was functionalized with 3-aminopropyl triethoxysilane (APTES) to obtain the APTES-Mt products (APTES1.0CEC-Mt, APTES2.0CEC-Mt, APTES3.0CEC-Mt, APTES4.0CEC-Mt) with enhanced adsorption capacity for Co2+. The physico-chemical properties of the synthesized adsorbents were characterized by spectroscopic and microscopic methods, and the results demonstrated that APTES was successfully intercalated into the gallery of Ca-Mt or grafted onto the surface of Ca-Mt through Si-O bonds. The effect of solution pH, ionic strength, temperature, initial concentrations and contact time on adsorption of Co2+ by APTES-Mt was evaluated. The results indicated that adsorption of Co2+ onto Ca-Mt, APTES1.0CEC-Mt and APTES2.0CEC-Mt can be considered to be a pseudo-second-order process. In contrast, adsorption of Co2+ onto APTES3.0CEC-Mt and APTES4.0CEC-Mt fitted well with the pseudo-first-order kinetics. The adsorption isotherms were described by the Langmuir model, and the maximum adsorption capacities of APTES1.0CEC-Mt, APTES2.0CEC-Mt, APTES3.0CEC-Mt and APTES4.0CEC-Mt were 25.1, 33.8, 61.6, and 61.9 mg·g-1, respectively. In addition, reaction temperature had no impact on the adsorption capacity, while both the pH and ionic strength significantly affected the adsorption process. A synergistic effect of ion exchange and coordination interactions on adsorption was observed, thereby leading to a significant enhancement of Co2+ adsorption by the composites. Thus, APTES-Mt could be a cost-effective and environmental-friendly adsorbent, with potential for treating Co2+-rich wastewater. PMID:27448094

  9. Dissociative adsorption of water on Au/MgO/Ag(001) from first principles calculations

    NASA Astrophysics Data System (ADS)

    Nevalaita, J.; Häkkinen, H.; Honkala, K.

    2015-10-01

    The molecular and dissociative adsorption of water on a Ag-supported 1 ML, 2 ML and 3 ML-a six atomic layer-thick MgO films with a single Au adatom is investigated using density functional theory calculations. The obtained results are compared to a bulk MgO(001) surface with an Au atom. On thin films the negatively charged Au strengthens the binding of the polar water molecule due to the attractive Au-H interaction. The adsorption energy trends of OH and H with respect to the film thickness depend on an adsorption site. In the case OH or H binds atop Au on MgO/Ag(001), the adsorption becomes more exothermic with the increasing film thickness, while the reverse trend is seen when the adsorption takes place on bare MgO/Ag(001). This behavior can be explained by different bonding mechanisms identified with the Bader analysis. Interestingly, we find that the rumpling of the MgO film and the MgO-Ag interface distance correlate with the charge transfer over the thin film and the interface charge, respectively. Moreover, we employ a modified Born-Haber-cycle to analyze the effect of film thickness to the adsorption energy of isolated Au and OH species on MgO/Ag(001). The analysis shows that the attractive Coulomb interaction between the negatively charged adsorbate and the positive MgO-Ag-interface does not completely account for the weaker binding with increasing film thickness. The redox energy associated with the charge transfer from the interface to the adsorbate is more exothermic with the increasing film thickness and partly compensates the decrease in the attractive Coulomb interaction.

  10. Characterization of the cation-binding capacity of a potassium-adsorption filter used in red blood cell transfusion.

    PubMed

    Suzuki, Takao; Muto, Shigeaki; Miyata, Yukio; Maeda, Takao; Odate, Takayuki; Shimanaka, Kimio; Kusano, Eiji

    2015-06-01

    A K(+) -adsorption filter was developed to exchange K(+) in the supernatant of stored irradiated red blood cells with Na(+) . To date, however, the filter's adsorption capacity for K(+) has not been fully evaluated. Therefore, we characterized the cation-binding capacity of this filter. Artificial solutions containing various cations were continuously passed through the filter in 30 mL of sodium polystyrene sulfonate at 10 mL/min using an infusion pump at room temperature. The cation concentrations were measured before and during filtration. When a single solution containing K(+) , Li(+) , H(+) , Mg(2+) , Ca(2+) , or Al(3+) was continuously passed through the filter, the filter adsorbed K(+) and the other cations in exchange for Na(+) in direct proportion to the valence number. The order of affinity for cation adsorption to the filter was Ca(2+) >Mg(2+) >K(+) >H(+) >Li(+) . In K(+) -saturated conditions, the filter also adsorbed Na(+) . After complete adsorption of these cations on the filter, their concentration in the effluent increased in a sigmoidal manner over time. Cations that were bound to the filter were released if a second cation was passed through the filter, despite the different affinities of the two cations. The ability of the filter to bind cations, especially K(+) , should be helpful when it is used for red blood cell transfusion at the bedside. The filter may also be useful to gain a better understanding of the pharmacological properties of sodium polystyrene sulfonate. PMID:25656422

  11. Understanding the Adsorption of PFOA on MIL-101(Cr)-Based Anionic-Exchange Metal-Organic Frameworks: Comparing DFT Calculations with Aqueous Sorption Experiments.

    PubMed

    Liu, Kai; Zhang, Siyu; Hu, Xiyue; Zhang, Kunyang; Roy, Ajay; Yu, Gang

    2015-07-21

    To examine the effects of different functionalization methods on adsorption behavior, anionic-exchange MIL-101(Cr) metal-organic frameworks (MOFs) were synthesized using preassembled modification (PAM) and postsynthetic modification (PSM) methods. Perfluorooctanoic acid (PFOA) adsorption results indicated that the maximum PFOA adsorption capacity was 1.19 and 1.89 mmol g(-1) for anionic-exchange MIL-101(Cr) prepared by PAM and PSM, respectively. The sorption equilibrium was rapidly reached within 60 min. Our results indicated that PSM is a better modification technique for introducing functional groups onto MOFs for adsorptive removal because PAM places functional groups onto the aperture of the nanopore, which hinders the entrance of organic contaminants. Our experimental results and the results of complementary density functional theory calculations revealed that in addition to the anion-exchange mechanism, the major PFOA adsorption mechanism is a combination of Lewis acid/base complexation between PFOA and Cr(III) and electrostatic interaction between PFOA and the protonated carboxyl groups of the bdc (terephthalic acid) linker. PMID:26066631

  12. Novel hollow microspheres of hierarchical zinc-aluminum layered double hydroxides and their enhanced adsorption capacity for phosphate in water.

    PubMed

    Zhou, Jiabin; Yang, Siliang; Yu, Jiaguo; Shu, Zhan

    2011-09-15

    Hollow microspheres of hierarchical Zn-Al layered double hydroxides (LDHs) were synthesized by a simple hydrothermal method using urea as precipitating agent. The morphology and microstructure of the as-prepared samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), nitrogen adsorption-desorption isotherms and fourier transform infrared (FTIR) spectroscopy. It was found that the morphology of hierarchical Zn-Al LDHs can be tuned from irregular platelets to hollow microspheres by simply varying concentrations of urea. The effects of initial phosphate concentration and contact time on phosphate adsorption using various Zn-Al LDHs and their calcined products (LDOs) were investigated from batch tests. Our results indicate that the equilibrium adsorption data were best fitted by Langmuir isothermal model, with the maximum adsorption capacity of 54.1-232 mg/g; adsorption kinetics follows the pseudo-second-order kinetic equation and intra-particle diffusion model. In addition, Zn-Al LDOs are shown to be effective adsorbents for removing phosphate from aqueous solutions due to their hierarchical porous structures and high specific surface areas. PMID:21719194

  13. Predicting CH4 adsorption capacity of microporous carbon using N2 isotherm and a new analytical model

    USGS Publications Warehouse

    Sun, Jielun; Chen, S.; Rostam-Abadi, M.; Rood, M.J.

    1998-01-01

    A new analytical pore size distribution (PSD) model was developed to predict CH4 adsorption (storage) capacity of microporous adsorbent carbon. The model is based on a 3-D adsorption isotherm equation, derived from statistical mechanical principles. Least squares error minimization is used to solve the PSD without any pre-assumed distribution function. In comparison with several well-accepted analytical methods from the literature, this 3-D model offers relatively realistic PSD description for select reference materials, including activated carbon fibers. N2 and CH4 adsorption data were correlated using the 3-D model for commercial carbons BPL and AX-21. Predicted CH4 adsorption isotherms, based on N2 adsorption at 77 K, were in reasonable agreement with the experimental CH4 isotherms. Modeling results indicate that not all the pores contribute the same percentage Vm/Vs for CH4 storage due to different adsorbed CH4 densities. Pores near 8-9 A?? shows higher Vm/Vs on the equivalent volume basis than does larger pores.

  14. First-principles calculations of the indigo encapsulation and adsorption by MgO nanotubes

    SciTech Connect

    Sánchez-Ochoa, F. Cocoletzi, Gregorio H.; Canto, Gabriel I.; Takeuchi, Noboru

    2014-06-07

    We have performed ab-initio calculations to investigate the structural and electronic properties of (m,m) chiral magnesium oxide nanotubes, (m,m)MgONTs, to explore the encapsulation, inclusion, and adsorption of dyes (organic molecules) such as Indigo (IND). Studies start by determining the structural parameters of the MgO nanotubes with different diameters and the IND. The indigo encapsulation into the MgONT is studied considering four (m,m) chiralities which yield 4 different NT diameters. In the endohedral functionalization, the indigo is within the NT at a tilt angle as in previous theoretical studies of organic molecules inside carbon and boron-nitride nanotubes. Results show that the encapsulation is a strong exothermic process with the m = 6 case exhibiting the largest encapsulation energy. It is also explored the indigo adsorption on the NT surface in the parallel and perpendicular configurations. The perpendicular configuration of the IND adsorption on the (8,8)MgONT exhibits the largest energy. The indigo inclusion within the NTs meets a potential barrier when m < 6, however this barrier diminishes as the index increases. Additionally, we have determined the total density of states (DOS), partial DOS, electron charge redistributions, and the highest occupied molecular orbital–lowest unoccupied molecular orbital levels for the NTs with m = 6. Very strong binding energies and electron charge transfer from the IND to NTs is present in the atomic structures.

  15. First-principles calculations of the indigo encapsulation and adsorption by MgO nanotubes

    NASA Astrophysics Data System (ADS)

    Sánchez-Ochoa, F.; Cocoletzi, Gregorio H.; Canto, Gabriel I.; Takeuchi, Noboru

    2014-06-01

    We have performed ab-initio calculations to investigate the structural and electronic properties of (m,m) chiral magnesium oxide nanotubes, (m,m)MgONTs, to explore the encapsulation, inclusion, and adsorption of dyes (organic molecules) such as Indigo (IND). Studies start by determining the structural parameters of the MgO nanotubes with different diameters and the IND. The indigo encapsulation into the MgONT is studied considering four (m,m) chiralities which yield 4 different NT diameters. In the endohedral functionalization, the indigo is within the NT at a tilt angle as in previous theoretical studies of organic molecules inside carbon and boron-nitride nanotubes. Results show that the encapsulation is a strong exothermic process with the m = 6 case exhibiting the largest encapsulation energy. It is also explored the indigo adsorption on the NT surface in the parallel and perpendicular configurations. The perpendicular configuration of the IND adsorption on the (8,8)MgONT exhibits the largest energy. The indigo inclusion within the NTs meets a potential barrier when m < 6, however this barrier diminishes as the index increases. Additionally, we have determined the total density of states (DOS), partial DOS, electron charge redistributions, and the highest occupied molecular orbital-lowest unoccupied molecular orbital levels for the NTs with m = 6. Very strong binding energies and electron charge transfer from the IND to NTs is present in the atomic structures.

  16. Theoretical investigation of lead vapor adsorption on kaolinite surfaces with DFT calculations.

    PubMed

    Wang, Xinye; Huang, Yaji; Pan, Zhigang; Wang, Yongxing; Liu, Changqi

    2015-09-15

    Kaolinite can be used as the in-furnace sorbent/additive to adsorb lead (Pb) vapor at high temperature. In this paper, the adsorptions of Pb atom, PbO molecule and PbCl2 molecule on kaolinie surfaces were investigated by density functional theory (DFT) calculation. Si surface is inert to Pb vapor adsorption while Al surfaces with dehydroxylation are active for the unsaturated Al atoms and the O atoms losing H atoms. The adsorption energy of PbO is much higher than that of Pb atom and PbCl2. Considering the energy barriers, it is easy for PbO and PbCl2 to adsorb on Al surfaces but difficult to escape. The high energy barriers of de-HCl process cause the difficulties of PbCl2 to form PbO·Al2O3·2SiO2 with kaolinite. Considering the inertia of Si atoms and the activity of Al atoms after dehydroxylation, calcination, acid/alkali treatment and some other treatment aiming at amorphous silica producing and Al activity enhancement can be used as the modification measures to improve the performance of kaolinite as the in-furnace metal capture sorbent. PMID:25880048

  17. Molecular basis for the high CO2 adsorption capacity of chabazite zeolites.

    PubMed

    Pham, Trong D; Hudson, Matthew R; Brown, Craig M; Lobo, Raul F

    2014-11-01

    CO2 adsorption in Li-, Na-, K-CHA (Si/Al=6,=12), and silica chabazite zeolites was investigated by powder diffraction. Two CO2 adsorption sites were found in all chabazites with CO2 locating in the 8-membered ring (8MR) pore opening being the dominant site. Electric quadrupole-electric field gradient and dispersion interactions drive CO2 adsorption at the middle of the 8 MRs, while CO2 polarization due to interaction with cation sites controls the secondary CO2 site. In Si-CHA, adsorption is dominated by dispersion interactions with CO2 observed on the pore walls and in 8 MRs. CO2 adsorption complexes on dual cation sites were observed on K-CHA, important for K-CHA-6 samples due to a higher probability of two K(+) cations bridging CO2. Trends in isosteric heats of CO2 adsorption based on cation type and concentration can be correlated with adsorption sites and CO2 quantity. A decrease in the hardness of metal cations results in a decrease in the direct interaction of these cations with CO2. PMID:25273234

  18. High gas storage capacities and stepwise adsorption in a UiO type metal-organic framework incorporating Lewis basic bipyridyl sites.

    PubMed

    Li, Liangjun; Tang, Sifu; Wang, Chao; Lv, Xiaoxia; Jiang, Min; Wu, Huaizhi; Zhao, Xuebo

    2014-03-01

    A UiO type MOF with Lewis basic bipyridyl sites was synthesized and structurally characterized. After being activated by Soxhlet-extraction, this MOF exhibits high storage capacities for H2, CH4 and CO2, and shows unusual stepwise adsorption for liquid CO2 and solvents, indicating a sequential filling mechanism on different adsorption sites. PMID:24445724

  19. Water adsorption on O(2x2)/Ru(0001) from STM experiments andfirst-principles calculations

    SciTech Connect

    Cabrera-Sanfelix, P.; Sanchez-Portal, D.; Mugarza, A.; Shimizu,T.K.; Salmeron, M.; Arnau, A.

    2007-10-15

    We present a combined theoretical and experimental study of water adsorption on Ru(0001) pre-covered with 0.25 monolayers (ML) of oxygen forming a (2 x 2) structure. Several structures were analyzed by means of Density Functional Theory calculations for which STM simulations were performed and compared with experimental data. Up to 0.25 monolayers the molecules bind to the exposed Ru atoms of the 2 x 2 unit cell via the lone pair orbitals. The molecular plane is almost parallel to the surface with its H atoms pointing towards the chemisorbed O atoms of the 2 x 2 unit cell forming hydrogen bonds. The existence of these additional hydrogen bonds increases the adsorption energy of the water molecule to approximately 616 meV, which is {approx}220 meV more stable than on the clean Ru(0001) surface with a similar configuration. The binding energy shows only a weak dependence on water coverage, with a shallow minimum for a row structure at 0.125 ML. This is consistent with the STM experiments that show a tendency of the molecules to form linear rows at intermediate coverage. Our calculations also suggest the possible formation of water dimers near 0.25 ML.

  20. All-Electron Scalar Relativistic Calculations on the Adsorption of Small Gold Clusters Toward Methanol Molecule.

    PubMed

    Kuang, Xiang-Jun; Wang, Xin-Qiang; Liu, Gao-Bin

    2015-02-01

    Under the framework of DFT, an all-electron scalar relativistic calculation on the adsorption of Aun (n = 1-13) clusters toward methanol molecule has been performed with the generalized gradient approximation at PW91 level. Our calculation results reveal that the small gold cluster would like to bond with oxygen of methanol molecule at the edge of gold cluster plane. After adsorption, the chemical activities of hydroxyl group and methyl group are enhanced to some extent. The even-numbered AunCH3OH cluster with closed-shell electronic configuration is relatively more stable than the neighboring odd-numbered AunCH3OH cluster with open-shell electronic configuration. All the AunCH3OH clusters prefer low spin multiplicity (M = 1 for even-numbered AuNCH3OH clusters, M = 2 for odd-numbered AunCH3OH clusters) and the magnetic moments are mainly contributed by gold atoms. The odd-even alterations of magnetic moments and electronic configurations can be observed clearly and may be simply understood in terms of the electron pairing effect. PMID:26353643

  1. Functionalized graphene sheets with poly(ionic liquid)s and high adsorption capacity of anionic dyes

    NASA Astrophysics Data System (ADS)

    Zhao, Weifeng; Tang, Yusheng; Xi, Jia; Kong, Jie

    2015-01-01

    Graphene sheets were covalently functionalized with poly(1-vinylimidazole) (PVI) type poly(ionic liquid), by utilizing a diazonium addition reaction and the subsequent grafting of PVI polymers onto the graphene sheet surface by a quaternarization reaction. The resultant modified graphene sheets showed improved dispersion property when being dissolved in DMF and ethanol. FTIR, XPS, XRD and TEM observations confirmed the success of the covalent functionalization, and thermogravimetric analysis revealed that the grafting ratio of PVI was ∼12 wt%. The obtained PVI-functionalized graphene showed a high capability for removing anionic dyes such as methyl blue (MB) from water solution. The experimental data of isotherm fitted well with the Langmuir adsorption model. The adsorption capacity of 1910 mg g-1 for methyl blue (MB) dye was observed for functionalized graphene sheets with poly(ionic liquid)s, which was higher than that of unmodified graphene. The high adsorption capacity observed in this study emphasizes that poly(ionic liquid)s-modified graphene materials have a great potential for water purification as they are highly efficient and stable adsorbents for sustainability.

  2. Effects of igneous intrusion on microporosity and gas adsorption capacity of coals in the Haizi Mine, China.

    PubMed

    Jiang, Jingyu; Cheng, Yuanping

    2014-01-01

    This paper describes the effects of igneous intrusions on pore structure and adsorption capacity of the Permian coals in the Huaibei Coalfield, China. Twelve coal samples were obtained at different distances from a ~120 m extremely thick sill. Comparisons were made between unaltered and heat-affected coals using geochemical data, pore-fracture characteristics, and adsorption properties. Thermal alteration occurs down to ~1.3 × sill thickness. Approaching the sill, the vitrinite reflectance (R(o)) increased from 2.30% to 2.78%, forming devolatilization vacuoles and a fine mosaic texture. Volatile matter (VM) decreased from 17.6% to 10.0% and the moisture decreased from 3.0% to 1.6%. With decreasing distance to the sill, the micropore volumes initially increased from 0.0054 cm(3)/g to a maximum of 0.0146 cm(3)/g and then decreased to 0.0079 cm(3)/g. The results show that the thermal evolution of the sill obviously changed the coal geochemistry and increased the micropore volume and adsorption capacity of heat-affected coal (60-160 m from the sill) compared with the unaltered coals. The trap effect of the sill prevented the high-pressure gas from being released, forming gas pocket. Mining activities near the sill created a low pressure zone leading to the rapid accumulation of methane and gas outbursts in the Haizi Mine. PMID:24723841

  3. Effects of Igneous Intrusion on Microporosity and Gas Adsorption Capacity of Coals in the Haizi Mine, China

    PubMed Central

    2014-01-01

    This paper describes the effects of igneous intrusions on pore structure and adsorption capacity of the Permian coals in the Huaibei Coalfield, China. Twelve coal samples were obtained at different distances from a ~120 m extremely thick sill. Comparisons were made between unaltered and heat-affected coals using geochemical data, pore-fracture characteristics, and adsorption properties. Thermal alteration occurs down to ~1.3 × sill thickness. Approaching the sill, the vitrinite reflectance (Ro) increased from 2.30% to 2.78%, forming devolatilization vacuoles and a fine mosaic texture. Volatile matter (VM) decreased from 17.6% to 10.0% and the moisture decreased from 3.0% to 1.6%. With decreasing distance to the sill, the micropore volumes initially increased from 0.0054 cm3/g to a maximum of 0.0146 cm3/g and then decreased to 0.0079 cm3/g. The results show that the thermal evolution of the sill obviously changed the coal geochemistry and increased the micropore volume and adsorption capacity of heat-affected coal (60–160 m from the sill) compared with the unaltered coals. The trap effect of the sill prevented the high-pressure gas from being released, forming gas pocket. Mining activities near the sill created a low pressure zone leading to the rapid accumulation of methane and gas outbursts in the Haizi Mine. PMID:24723841

  4. 30 CFR 254.44 - Calculating response equipment effective daily recovery capacities.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR OFFSHORE OIL-SPILL RESPONSE REQUIREMENTS FOR FACILITIES... calculate the effective daily recovery capacity of the response equipment identified in your response plan... daily recovery capacity of the equipment by multiplying the manufacturer's rated throughput...

  5. 30 CFR 254.44 - Calculating response equipment effective daily recovery capacities.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... INTERIOR OFFSHORE OIL-SPILL RESPONSE REQUIREMENTS FOR FACILITIES LOCATED SEAWARD OF THE COAST LINE Related... capacity of the response equipment identified in your response plan that you would use to contain and recover your worst case discharge. You must calculate the effective daily recovery capacity of...

  6. Nature of adsorption on TiC(111) investigated with density-functional calculations

    NASA Astrophysics Data System (ADS)

    Ruberto, Carlo; Lundqvist, Bengt I.

    2007-06-01

    Extensive density-functional calculations are performed for chemisorption of atoms in the three first periods (H, B, C, N, O, F, Al, Si, P, S, and Cl) on the polar TiC(111) surface. Calculations are also performed for O on TiC(001), for full O(1×1) monolayer on TiC(111), as well as for bulk TiC and for the clean TiC(111) and (001) surfaces. Detailed results concerning atomic structures, energetics, and electronic structures are presented. For the bulk and the clean surfaces, previous results are confirmed. In addition, detailed results are given on the presence of C-C bonds in the bulk and at the surface, as well as on the presence of a Ti-based surface resonance (TiSR) at the Fermi level and of C-based surface resonances (CSR’s) in the lower part of the surface upper valence band. For the adsorption, adsorption energies Eads and relaxed geometries are presented, showing great variations characterized by pyramid-shaped Eads trends within each period. An extraordinarily strong chemisorption is found for the O atom, 8.8eV /adatom. On the basis of the calculated electronic structures, a concerted-coupling model for the chemisorption is proposed, in which two different types of adatom-substrate interactions work together to provide the obtained strong chemisorption: (i) adatom-TiSR and (ii) adatom-CSR’s. This model is used to successfully describe the essential features of the calculated Eads trends. The fundamental nature of this model, based on the Newns-Anderson model, should make it apt for general application to transition-metal carbides and nitrides and for predictive purposes in technological applications, such as cutting-tool multilayer coatings and MAX phases.

  7. Determination of the adsorption capacity of activated carbon made from coffee grounds by chemical activation with ZnCl2 and H3PO4.

    PubMed

    Namane, A; Mekarzia, A; Benrachedi, K; Belhaneche-Bensemra, N; Hellal, A

    2005-03-17

    In order to evaluate the adsorptive capacities of granular activated carbon produced from coffee grounds by chemical activation, the adsorption of different phenols and acid and basic dyes, has been carried out. The comparison with a commercial activated carbon has been made. Adsorption isotherms of phenols and dyes (acid and basic) onto produced and commercial granular activated carbons were experimentally determined by batch tests. Both Freundlich and Langmuir models are well suited to fit the adsorption isotherm data. As a result, the coffee grounds based activated carbon may be promising for phenol and dye removal from aqueous streams. PMID:15752865

  8. Calculating henry adsorption constants of molecular hydrogen at 77 K on alumophosphate zeolites with different microchannel sizes

    NASA Astrophysics Data System (ADS)

    Grenev, I. V.; Gavrilov, V. Yu.

    2014-01-01

    Adsorption isotherms of molecular hydrogen are measured at 77 K in a series of AlPO alumophosphate zeolites with different microchannel sizes. The potential of the intermolecular interaction of H2 is calculated within the model of a cylindrical channel of variable size. Henry constants are calculated for this model for arbitrary orientations of the adsorbate molecules in microchannels. The experimental and calculated values of the Henry adsorption constant of H2 are compared at 77 K on AlPO zeolites. The constants of intermolecular interaction are determined for the H2-AlPO system.

  9. 2,4-D adsorption to biochars: effect of preparation conditions on equilibrium adsorption capacity and comparison with commercial activated carbon literature data.

    PubMed

    Kearns, J P; Wellborn, L S; Summers, R S; Knappe, D R U

    2014-10-01

    Batch isotherm experiments were conducted with chars to study adsorption of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Chars generated from corncobs, bamboo and wood chips in a laboratory pyrolyzer at 400-700 °C were compared with traditional kiln charcoals collected from villages in S/SE Asia and with activated carbons (ACs). 2,4-D uptake by laboratory chars obtained from bamboo and wood chips after 14 h of pyrolysis at 700 °C, from wood chips after 96 h of pyrolysis at 600 °C, and one of the field-collected chars (basudha) was comparable to ACs. H:C and O:C ratios declined with pyrolysis temperature and duration while surface area increased to >500 m(2)/g. Increasing pyrolysis intensity by increasing temperature and/or duration of heating was found to positively influence adsorption capacity yield (mg(2,4-D/g(feedstock))) over the range of conditions studied. Economic analysis showed that high temperature chars can be a cost-effective alternative to ACs for water treatment applications. PMID:24934321

  10. Adsorption and growth morphology of rare-earth metals on graphene studied by ab initio calculations and scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Liu, Xiaojie; Wang, C. Z.; Hupalo, M.; Yao, Y. X.; Tringides, M. C.; Lu, W. C.; Ho, K. M.

    2010-12-01

    Adsorption of rare-earth (RE) adatoms (Nd, Gd, Eu, and Yb) on graphene was studied by first-principles calculations based on the density-functional theory. The calculations show that the hollow site of graphene is the energetically favorable adsorption site for all the RE adatoms studied. The adsorption energies and diffusion barriers of Nd and Gd on graphene are found to be larger than those of Eu and Yb. Comparison with scanning tunneling microscopy experiments for Gd and Eu epitaxially grown on graphene confirms these calculated adsorption and barrier differences, since fractal-like islands are observed for Gd and flat-topped crystalline islands for Eu. The formation of flat Eu islands on graphene can be attributed to its low diffusion barrier and relatively larger ratio of adsorption energy to its bulk cohesive energy. The interactions between the Nd and Gd adatoms and graphene cause noticeable in-plane lattice distortions in the graphene layer. Adsorption of the RE adatoms on graphene also induces significant electric dipole and magnetic moments.

  11. Electronic and Magnetic Properties of Al Adsorption on α-Uranium(001) Surface: Ab Initio Calculations

    SciTech Connect

    Nie, JL; Xiao, Haiyan J.; Gao, Fei; Zu, Xiaotao T.

    2009-05-12

    First-principles calculations based on density functional theory with the generalized gradient approximation have been performed to study the aluminum (Al) adsorption on the (001) surface of α-uranium (α-U). The geometric, electronic and magnetic properties have been investigated at coverages of 0.25 and 0.5 monolayer. The results show that the quasi-trigonal sites are preferred at both coverages. The bonding of Al with U is found to be metallic, which mainly arises from the mixing of Al 3sp and U 5f states. A ferromagnetic phase is determined for the bare α-U(001) surface, while the adsorption of Al on the surface significantly perturbs the spin arrangement pattern and reduces the local magnetic moment, leading to a ferrimagnetic phase on the α-U(001) surface at the coverage of 0.5 monolayer. However, the Al overlayer is paramagnetic. Generally, the spin polarization has negligible effects on the geometric and electronic properties of Al atoms on the α-U(001) surface.

  12. PREDICTING THE ADSORPTION CAPACITY OF ACTIVATED CARBON FOR ORGANIC CONTAMINANTS FROM ADSORBENT AND ADSORBATE PROPERTIES

    EPA Science Inventory

    A quantitative structure-property relationship (QSPR) was developed and combined with the Polanyi-Dubinin-Manes model to predict adsorption isotherms of emerging contaminants on activated carbons with a wide range of physico-chemical properties. Affinity coefficients (βl

  13. 40 CFR Appendix D to Part 72 - Calculation of Potential Electric Output Capacity

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 16 2011-07-01 2011-07-01 false Calculation of Potential Electric Output Capacity D Appendix D to Part 72 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) PERMITS REGULATION Pt. 72, App. D Appendix D to Part 72—Calculation...

  14. 40 CFR Appendix D to Part 72 - Calculation of Potential Electric Output Capacity

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 16 2010-07-01 2010-07-01 false Calculation of Potential Electric Output Capacity D Appendix D to Part 72 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) PERMITS REGULATION Pt. 72, App. D Appendix D to Part 72—Calculation...

  15. 40 CFR Appendix D to Part 72 - Calculation of Potential Electric Output Capacity

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 17 2013-07-01 2013-07-01 false Calculation of Potential Electric Output Capacity D Appendix D to Part 72 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) PERMITS REGULATION Pt. 72, App. D Appendix D to Part 72—Calculation...

  16. D0 Solenoid Upgrade Project: Solenoid Insulatiing Vacuum Vessels; Relief Path Capacity Calculation

    SciTech Connect

    Rucinski, R.; Bell, D.; /Fermilab

    1993-05-26

    This engineering note documents the calculations done to determine the relief capacity of the solenoid vacuum pumping line. The calculations were done by David Bell, a co-op student from the University of Wisconsin. The calculations are attached. The conclusion is that the vacuum pumping line has a venting capacity of 129 g/s warm helium or 298 g/s warm nitrogen. Both of these capacities are much larger than the expected operating mass flow rates of the liquid helium (5 to 15 g/s) or liquid nitrogen (2 or 3 g/s) circuits. The calculations assume the solenoid vacuum vessel is at 3 psig and the relief plate is set at 1.5 psig. Additional calculations were done to prove that the venting capacity of the vacuum pumping line exceeded flowrates due to a failure mode. These calculations are attached. Since the system is not finalized, (pipe sizes not determined, components sized...) the calculations were done by first picking reasonable line sizes based on known allowed pressure drops in the system and then doing a maximum delivery rate calculation if a line was completely severed in the vacuum space of the solenoid/control dewar. The numbers from these calculations say that failure mode flow rates are 80 g/s liquid helium or 80 g/s liquid nitrogen. Both these values are less than the capacity of the relief line. In the five months since the (12/92 Dave Bell) calculations were done, some changes occured to the relief path. The most notable is that the radiation shield is now considered to be 6.625-inch O.D. instead of 6.00-inch used in the venting calculation. This change would tend to lower the capacity numbers. Another change was that for about half the venting path the chimney vacuum shell size was increased to 10-inch pipe. This change tends to increase the capacity numbers which were done assuming 8-inch pipe. These changes taken together probably offset each other or make the capacity numbers better. In either case, since the margin of safety is large, the

  17. Properties of poly(1-naphthylamine)/Fe3O4 composites and arsenic adsorption capacity in wastewater

    NASA Astrophysics Data System (ADS)

    Tran, Minh Thi; Nguyen, Thi Huyen Trang; Vu, Quoc Trung; Nguyen, Minh Vuong

    2016-03-01

    The research results of poly(1-naphthylamine)/Fe3O4 (PNA/Fe3O4) nanocomposites synthesized by a chemical method for As(III) wastewater treatment are presented in this paper. XRD patterns and TEM images showed that the Fe3O4 grain size varied from 13 to 20 nm. The results of Raman spectral analysis showed that PNA participated in part of the PNA/Fe3O4 composite samples. The grain size of PNA/Fe3O4 composite samples is about 25-30 nm measured by SEM. The results of vibrating sample magnetometer measurements at room temperature showed that the saturation magnetic moment of PNA/Fe3O4 samples decreased from 63.13 to 43.43 emu/g, while the PNA concentration increased from 5% to 15%. The nitrogen adsorption-desorption isotherm of samples at 77 K at a relative pressure P/ P 0 of about 1 was studied in order to investigate the surface and porous structure of nanoparticles by the BET method. Although the saturation magnetic moments of samples decreased with the polymer concentration increase, the arsenic adsorption capacity of the PNA/Fe3O4 sample with the PNA concentration of 5% is better than that of Fe3O4 in a solution with pH = 7. In the solution with pH > 14, the arsenic adsorption of magnetic nanoparticles is insignificant.

  18. Evaluation of phosphorus adsorption capacity of sesame straw biochar on aqueous solution: influence of activation methods and pyrolysis temperatures.

    PubMed

    Park, J H; Ok, Y S; Kim, S H; Cho, J S; Heo, J S; Delaune, R D; Seo, D C

    2015-12-01

    The phosphorus (P) adsorption characteristic of sesame straw biochar prepared with different activation agents and pyrolysis temperatures was evaluated. Between 0.109 and 0.300 mg L(-1) in the form of inorganic phosphate was released from raw sesame straw biochar in the first 1 h. The release of phosphate was significantly enhanced from 62.6 to 168.2 mg g(-1) as the pyrolysis temperature increased. Therefore, sesame straw biochar cannot be used as an adsorbent for P removal without change in the physicochemical characteristics. To increase the P adsorption of biochar in aqueous solution, various activation agents and pyrolysis temperatures were applied. The amount of P adsorbed from aqueous solution by biochar activated using different activation agents appeared in the order ZnCl2 (9.675 mg g(-1)) > MgO (8.669 mg g(-1)) ⋙ 0.1N-HCl > 0.1N-H2SO4 > K2SO4 ≥ KOH ≥ 0.1N-H3PO4, showing ZnCl2 to be the optimum activation agent. Higher P was adsorbed by the biochar activated using ZnCl2 under different pyrolysis temperatures in the order 600 °C > 500 °C > 400 °C > 300 °C. Finally, the amount of adsorbed P by activated biochar at different ratios of biochar to ZnCl2 appeared in the order 1:3 ≒ 1:1 > 3:1. As a result, the optimum ratio of biochar to ZnCl2 and pyrolysis temperature were found to be 1:1 and 600 °C for P adsorption, respectively. The maximum P adsorption capacity by activated biochar using ZnCl2 (15,460 mg kg(-1)) was higher than that of typical biochar, as determined by the Langmuir adsorption isotherm. Therefore, the ZnCl2 activation of sesame straw biochar was suitable for the preparation of activated biochar for P adsorption. PMID:26040973

  19. Effects of sulfur impregnation temperature on the properties and mercury adsorption capacities of activated carbon fibers (ACFs)

    USGS Publications Warehouse

    Hsi, H.-C.; Rood, M.J.; Rostam-Abadi, M.; Chen, S.; Chang, R.

    2001-01-01

    Laboratory studies were conducted to determine the role of sulfur functional groups and micropore surface area of carbon-based adsorbents on the adsorption of Hg0 from simulated coal combustion flue gases. In this study, raw activated carbon fibers that are microporous (ACF-20) were impregnated with elemental sulfur between 250 and 650 ??C. The resulting samples were saturated with respect to sulfur content. Total sulfur content of the sulfur impregnated ACF samples decreased with increasing impregnation temperatures from 250 and 500 ??C and then remained constant to 650 ??C. Results from sulfur K-edge X-ray absorption near-edge structure (S-XANES) spectroscopy showed that sulfur impregnated on the ACF samples was in both elemental and organic forms. As sulfur impregnation temperature increased, however, the relative amounts of elemental sulfur decreased with a concomitant increase in the amount of organic sulfur. Thermal analyses and mass spectrometry revealed that sulfur functional groups formed at higher impregnation temperatures were more thermally stable. In general, sulfur impregnation decreased surface area and increased equilibrium Hg0 adsorption capacity when compared to the raw ACF sample. The ACF sample treated with sulfur at 400 ??C had a surface area of only 94 m2/g compared to the raw ACF sample's surface area of 1971 m2/g, but at least 86% of this sample's surface area existed as micropores and it had the largest equilibrium Hg0adsorption capacities (2211-11343 ??g/g). Such a result indicates that 400 ??C is potentially an optimal sulfur impregnation temperature for this ACF. Sulfur impregnated on the ACF that was treated at 400 ??C was in both elemental and organic forms. Thermal analyses and CS2extraction tests suggested that elemental sulfur was the main form of sulfur affecting the Hg0 adsorption capacity. These findings indicate that both the presence of elemental sulfur on the adsorbent and a microporous structure are important properties for

  20. Determination of coalbed methane potential and gas adsorption capacity in Western Kentucky coals

    USGS Publications Warehouse

    Mardon, S.M.; Takacs, K.G.; Hower, J.C.; Eble, C.F.; Mastalerz, Maria

    2006-01-01

    The Illinois Basin has not been developed for Coalbed Methane (CBM) production. It is imperative to determine both gas content and other parameters for the Kentucky portion of the Illinois Basin if exploration is to progress and production is to occur in this area. This research is part of a larger project being conducted by the Kentucky Geological Survey to evaluate the CBM production of Pennsylvanian-age western Kentucky coals in Ohio, Webster, and Union counties using methane adsorption isotherms, direct gas desorption measurements, and chemical analyses of coal and gas. This research will investigate relationships between CBM potential and petrographic, surface area, pore size, and gas adsorption isotherm analyses of the coals. Maceral and reflectance analyses are being conducted at the Center for Applied Energy Research. At the Indiana Geological Survey, the surface area and pore size of the coals will be analyzed using a Micrometrics ASAP 2020, and the CO2 isotherm analyses will be conducted using a volumetric adsorption apparatus in a water temperature bath. The aforementioned analyses will be used to determine site specific correlations for the Kentucky part of the Illinois Basin. The data collected will be compared with previous work in the Illinois Basin and will be correlated with data and structural features in the basin. Gas composition and carbon and hydrogen isotopic data suggest mostly thermogenic origin of coalbed gas in coals from Webster and Union Counties, Kentucky, in contrast to the dominantly biogenic character of coalbed gas in Ohio County, Kentucky.

  1. Synthesis of bilayer MoS{sub 2} nanosheets by a facile hydrothermal method and their methyl orange adsorption capacity

    SciTech Connect

    Ye, Lijuan; Xu, Haiyan; Zhang, Dingke; Chen, Shijian

    2014-07-01

    Highlights: • Hexagonal phase of MoS{sub 2} nanosheets was synthesized by a facile hydrothermal method. • FE-SEM and TEM images show the sheets-like morphology of MoS{sub 2}. • Bilayer MoS{sub 2} can be grown under the optimized mole ratio of 2:1 of S:Mo at 180 °C for 50 h. • The MoS{sub 2} nanosheets possess high methyl orange adsorption capacity due to the large surface area. - Abstract: Molybdenum disulfide (MoS{sub 2}) nanosheets have received significant attention recently due to the potential applications for exciting physics and technology. Here we show that MoS{sub 2} nanosheets can be prepared by a facile hydrothermal method. The study of the properties of the MoS{sub 2} nanosheets prepared at different conditions suggests that the mole ratio of precursors and hydrothermal time significantly influences the purity, crystalline quality and thermal stability of MoS{sub 2}. X-ray diffraction, Raman spectra and transmission electron microscopy results indicate that bilayer MoS{sub 2} can be grown under an optimized mole ratio of 2:1 of S:Mo at 180 °C for 50 h. Moreover, such ultrathin nanosheets exhibit a prominent photoluminescence and possess high methyl orange adsorption capacity due to the large surface area, which can be potentially used in photodevice and photochemical catalyst.

  2. Zeolite Y adsorbents with high vapor uptake capacity and robust cycling stability for potential applications in advanced adsorption heat pumps

    SciTech Connect

    Li, XS; Narayanan, S; Michaelis, VK; Ong, TC; Keeler, EG; Kim, H; Mckay, IS; Griffin, RG; Wang, EN

    2015-01-01

    Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg2+ ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg, Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the lab-scale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N-2 sorption, Al-27/Si-29 MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick's 2nd law and D-R equation regressions. Among these, close examination of sorption isotherms for H2O and N-2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications. (C) 2014 Elsevier Inc. All rights reserved.

  3. Zeolite Y Adsorbents with High Vapor Uptake Capacity and Robust Cycling Stability for Potential Applications in Advanced Adsorption Heat Pumps

    PubMed Central

    Li, Xiansen; Narayanan, Shankar; Michaelis, Vladimir K.; Ong, Ta-Chung; Keeler, Eric G.; Kim, Hyunho; McKay, Ian S.; Griffin, Robert G.; Wang, Evelyn N.

    2014-01-01

    Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg2+ ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg,Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the labscale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N2 sorption, 27Al/29Si MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick’s 2nd law and D-R equation regressions. Among these, close examination of sorption isotherms for H2O and N2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications. PMID:25395877

  4. Zeolite Y Adsorbents with High Vapor Uptake Capacity and Robust Cycling Stability for Potential Applications in Advanced Adsorption Heat Pumps.

    PubMed

    Li, Xiansen; Narayanan, Shankar; Michaelis, Vladimir K; Ong, Ta-Chung; Keeler, Eric G; Kim, Hyunho; McKay, Ian S; Griffin, Robert G; Wang, Evelyn N

    2015-01-01

    Modular and compact adsorption heat pumps (AHPs) promise an energy-efficient alternative to conventional vapor compression based heating, ventilation and air conditioning systems. A key element in the advancement of AHPs is the development of adsorbents with high uptake capacity, fast intracrystalline diffusivity and durable hydrothermal stability. Herein, the ion exchange of NaY zeolites with ingoing Mg(2+) ions is systematically studied to maximize the ion exchange degree (IED) for improved sorption performance. It is found that beyond an ion exchange threshold of 64.1%, deeper ion exchange does not benefit water uptake capacity or characteristic adsorption energy, but does enhance the vapor diffusivity. In addition to using water as an adsorbate, the uptake properties of Mg,Na-Y zeolites were investigated using 20 wt.% MeOH aqueous solution as a novel anti-freeze adsorbate, revealing that the MeOH additive has an insignificant influence on the overall sorption performance. We also demonstrated that the labscale synthetic scalability is robust, and that the tailored zeolites scarcely suffer from hydrothermal stability even after successive 108-fold adsorption/desorption cycles. The samples were analyzed using N2 sorption, (27)Al/(29)Si MAS NMR spectroscopy, ICP-AES, dynamic vapor sorption, SEM, Fick's 2(nd) law and D-R equation regressions. Among these, close examination of sorption isotherms for H2O and N2 adsorbates allows us to decouple and extract some insightful information underlying the complex water uptake phenomena. This work shows the promising performance of our modified zeolites that can be integrated into various AHP designs for buildings, electronics, and transportation applications. PMID:25395877

  5. First-Principles Calculation of Phonon and Schottky Heat Capacities of Plutonium Dioxide

    NASA Astrophysics Data System (ADS)

    Nakamura, Hiroki; Machida, Masahiko; Kato, Masato

    2015-05-01

    Plutonium dioxide (PuO2) is a key ingredient of mixed oxide (MOX) and advanced nuclear fuels. Its thermophysical data is crucial in understanding the high-temperature behaviors of nuclear fuels. In particular, the high-temperature heat capacity is of great importance for their safety and performance analyses. Here, we evaluate the main contributions to the heat capacity of PuO2 from 0 to 1400 K through suitable first-principles calculations. Consequently, we successfully obtain a temperature dependence in good agreement with experimental measurements. This success mainly results from accurate calculations of the Schottky heat capacity caused by the excited levels of f-electrons of Pu. Our calculations resolve the mystery of why previous works failed to reproduce the measurement data. This study extends the possibility of performing simulation-based nuclear-fuel research instead of difficult measurements.

  6. [Ecological footprint calculation and development capacity analysis of China in 1999].

    PubMed

    Xu, Zhongmin; Zhang, Zhiqiang; Cheng, Guodong; Chen, Dongjing

    2003-02-01

    The ecological footprint method put forward and improved by William Rees and Mathis Wackernagel presents a methodologically simple but integrated framework for national natural capital accounting, which is capable of measuring the impact of Human's consumption on ecosystem. Based on the ecological footprint theory and calculation method, a flow network analysis method was introduced to illuminate the structure of complex ecological economic system, and the relationship among ecological footprint, diversity and development capacity was analyzed. In this paper, the ecological footprints of China and its provinces was calculated and compared with the national and local ecological carrying capacity. The results showed that the ecological footprints of China and most of its provinces were beyond the available ecological capacity, and China and its most provinces run 'national or regional ecological deficit'. In case of China, the national ecological deficit was 0.645 hm2 per cap in 1999. Secondly, we introduced a flow network analysis method, taking various ecological productive area as note, and adopted Ulanowicz's development capacity formula to analyze the relationship among ecological footprint diversity, development capacity and output. The results demonstrated that Ulanowicz's development capacity was a good predictor of economic system output. At the same time, two distinct ways to change development capacity were produced. Increasing ecological footprint or increasing ecological footprint's diversity would both increase development capacity. Due to the fact that the ecological footprints had already been beyond bio-capacities, the only way to increase development capacity was to increase ecological footprint's diversity. The positive relationship between ecological footprint diversity and resources utilization efficiency demonstrated that there was no conflict between increasing ecological footprint's diversity and reducing footprints while not comprising our

  7. Adsorption of carbon monoxide on ZSM-5 zeolites. Infrared spectroscopic study and quantum-chemical calculations

    SciTech Connect

    Kustov, L.M.; Kazansky, V.B.; Beran, S.; Kubelkova, L.; Jiru, P.

    1987-09-24

    Low temperature adsorption of CO was studied on H-ZSM-5 zeolites modified by dehydroxylation, ionic exchange with Al/sup 3 +/, and impregnation with Al/sub 2/O/sub 3/ and on Na-ZSM-5 and CaH-ZSM-5 zeolites. It was found that interaction of CO with framework OH groups results in the formation of a hydrogen-bonded CO complex whose OH bond frequency is decreased by 310-320 cm/sup -1/ compared with that of free hydroxyls. For the less acidic framework hydroxyls in large cavities of H/sub 70/Na/sub 30/-Y zeolite the observed shift is 275 cm/sup -1/. With ZSM-5 zeolites, at least six types of electron-accepting sites are observed originating from nonframework Al species (band of CO in the interaction complex: 2132, 2222, 2202, 2195, and 2198 cm/sup -1/) and the Al/sub 2/O/sub 3/ microcrystalline phase (CO band at 2153 cm/sup -1/). The CO bond orders calculated by the CNDO/2 method for the CO interaction complexes with models of surface sites increase in the following order: > O-CO < > OH-CO approx. ..-->.. Al-CO approx. = Na-CO < alumina-CO approx. = Ca-CO < ..-->.. Si-CO < Al(cationic)-CO. A correlation between the calculated bond orders of CO and the observed vibrational frequencies of CO-forming interaction complexes is drawn.

  8. Amphiphilic agarose-based adsorbents for chromatography. Comparative study of adsorption capacities and desorption efficiencies.

    PubMed

    Oscarsson, S; Angulo-Tatis, D; Chaga, G; Porath, J

    1995-01-01

    A number of hydrophobic derivatives attached to cross-linked agarose were studied as protein adsorbents. Differences in the adsorption and desorption behaviour were determined as functions of type and concentration of selected salts. Whereas octyl- and phenyl-Sepharose adsorb serum albumin preferentially, pyridyl-S-agarose shows a much stronger preferential affinity for IgG in the presence of high concentrations of lyotropic salts, such as sulphates. In contrast to pyridyl-S-agarose, a large portion of proteins remained fixed to octyl- and phenyl-Sepharose after extensive washing with 1 M NaOH. PMID:7881534

  9. Surface heterogeneity of C{sub 60} as studied by infrared spectroscopy of adsorbed CO and adsorption potential calculations

    SciTech Connect

    Folman, M.; Fastow, M.; Kozirovski, Y.

    1997-03-05

    In our recent investigation of the IR spectrum of CO physically adsorbed on C{sub 60} films, two well-resolved absorption bands at 2135 and 2128 cm{sup -1} were found, suggesting that the molecule is adsorbed on two different sites. To determine the nature of these adsorption sites, calculations of adsorption potentials and spectral shifts for the CO/C{sub 60} system were performed. The calculations were done for the fcc (100), fcc (111) hcp (001), and hcp (111) surface planes. In the calculations the 6-exponential and the Lennard-Jones potentials were used. A number of adsorption sites were chosen. These included the void space between four, three, and two neighboring C{sub 60} molecules and the center of the hexagon and the pentagon on the C{sub 60} surface. The calculated potentials and spectral shifts clearly indicate that adsorption sites in the voids between the C{sub 60} molecules are energetically preferred over sites on top of single C{sub 60} molecules. Comparison is made between results obtained with the two potentials and with results obtained previously with the two other carbon allotropes: graphite and diamond. 11 refs., 4 figs., 3 tabs.

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

    PubMed

    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

  11. High surface-area amidoxime-based polymer fibers co-grafted with various acid monomers yielding increased adsorption capacity for the extraction of uranium from seawater.

    PubMed

    Oyola, Yatsandra; Dai, Sheng

    2016-06-01

    Uranium is dissolved in the ocean at a uniform concentration of 3.34 ppb, which translates to approximately 4-5 billion tons of uranium. The development of adsorbents that can extract uranium from seawater has been a long term goal, but the extremely dilute uranium concentration along with the competition of other metal salts (which are at higher concentrations) has hindered the development of an economical adsorption process. Several acid monomers were co-grafted with acrylonitrile (AN) to help increase the hydrophilicity of the adsorbent to improve access to the metal adsorption sites. Grafting various acid monomers on PE fibers was found to significantly affect the uranium adsorption in simulated seawater in the following order: acrylic acid (AA) < vinyl sulfonic acid (VSA) < methacrylic acid (MAA) < itaconic acid (ITA) < vinyl phosphonic acid (VPA). Interestingly, the uranium adsorption capacity significantly increased when Mohr's salt was added with acrylic acid, most likely due to the reduction of co-polymerization of the monomers. When testing under more realistic conditions, the acid-grafted PE fiber adsorbents were exposed to natural seawater (more dilute uranium), the uranium adsorption capacity increased in the following order: MAA < AA (Mohr's salt) < VSA < ITA (Mohr's salt) < ITA < VPA, which agreed well with the simulated seawater results. Characterization of the adsorbents indicated that the increase in uranium adsorption capacity with each acid monomer was related to higher grafting of AN and therefore a higher conversion to amidoxime (AO). PMID:27145863

  12. 40 CFR Appendix D to Part 72 - Calculation of Potential Electric Output Capacity

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Output Capacity D Appendix D to Part 72 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) PERMITS REGULATION Pt. 72, App. D Appendix D to Part 72—Calculation of... design heat input from the boiler by the following equation: EC10NO91.003 For example: (1) Assume...

  13. SO 2 adsorption capacity of K 2CO 3-impregnated activated carbon as a function of K 2CO 3 content loaded by soaking and incipient wetness

    NASA Astrophysics Data System (ADS)

    Fortier, H.; Zelenietz, C.; Dahn, T. R.; Westreich, P.; Stevens, D. A.; Dahn, J. R.

    2007-01-01

    The SO 2 adsorption capacity of K 2CO 3-impregnated activated carbons, prepared by soaking carbon in large volumes of K 2CO 3 in solution of various concentrations, varies linearly with respect to the loading of K 2CO 3 on the carbon up to about 12% K 2CO 3 by weight. Above 12%, the capacity for SO 2 levels out and then decreases. This suggests that at high loadings the K 2CO 3 either aggregates and/or blocks pores of the activated carbon. In contrast, the adsorption capacity of carbons prepared by repeatedly (maximum of three times total) loading K 2CO 3 via incipient wetness is much larger than that of the soaked samples, up to 70% more, when the loading of K 2CO 3 is greater than 12%. Static and dynamic adsorption, DSC, SEM, EDX and incipient wetness studies of the samples show that the impregnant aggregates but does not block carbon pores.

  14. Gas Adsorption and Selectivity in Zeolitic Imidazolate Frameworks from First Principles Calculations

    NASA Astrophysics Data System (ADS)

    Ray, Keith; Olmsted, David; He, Ning; Houndonougbo, Yao; Laird, Brian; Asta, Mark

    2012-02-01

    Zeolitic Imidazolate Framework (ZIFs) are excellent candidate materials for carbon capture and gas separation. Here we employ the van der Waals density functional (vdW-DF) [1] in an analysis of the binding energetics for CO2, CH4 and N2 molecules in a set of ZIFs featuring different chemical functionalizations. We investigate multiple low-energy binding sites, which differ in their positions relative to functional groups on the imidazole linkers. In all cases an accurate treatment of van der Waals forces appears essential to provide reasonable binding energy magnitudes. We report results obtained from different parameterizations of the vdW-DF, providing comparisons between calculations and experimental values of the heat of adsorption [2]. This research is supported by the Energy Frontier Research Center ``Molecularly Engineered Energy Materials,'' funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001342. [1] M. Dion, H. Rydberg, E. Schroder, D. C. Langreth, B. I. Lundqvist, Phys. Rev. Let. 92, 246401 (2004) [2] W. Morris, B. Leung, H. Furukawa, O. K. Yaghi, N. He, H. Hayashi, Y. Houndonougbo, M. Asta, B. B. Laird, O. M. Yaghi, J. AM. CHEM. SOC. 2010, 132, 11006-11008

  15. Virial expansion of the second layer in physical adsorption - An ab initio calculation for helium on argon crystal

    NASA Technical Reports Server (NTRS)

    Oh, B. K.; Kim, S. K.

    1974-01-01

    A model of helium adsorption on an argon crystal is built up from the premise that local adsorption predominates in the first layer and nonlocal adsorption in the second. Application of the virial expansion theorem to the second layer gives a series in which the first term represents the motion of a single molecule in the external potential field and the second a two-body interaction under this field. The thermodynamic functions of the adsorbed phase are calculated ab initio, the gas-solid interaction potential being derived from lattice summation and the partition function from an appropriate choice of a site-spacing polynomial to describe the periodic potential. The mutual interaction of adsorbed molecules is calculated with a two-dimensional Lennard-Jones potential. The second virial coefficient is calculated and its dependence on temperature and choice of potential is studied. It is found that the second virial coefficient is very well approximated by a two-dimensional gas in free space. The adsorption isotherm, isosteric heat, and specific heat are obtained and compared with the results of Ross and Steele, giving excellent agreement.

  16. Long-Life and High-Areal-Capacity Li-S Batteries Enabled by a Light-Weight Polar Host with Intrinsic Polysulfide Adsorption.

    PubMed

    Pang, Quan; Nazar, Linda F

    2016-04-26

    Lithium-sulfur batteries are attractive electrochemical energy storage systems due to their high theoretical energy density and very high natural abundance of sulfur. However, practically, Li-S batteries suffer from short cycling life and low sulfur utilization, particularly in the case of high-sulfur-loaded cathodes. Here, we report on a light-weight nanoporous graphitic carbon nitride (high-surface-area g-C3N4) that enables a sulfur electrode with an ultralow long-term capacity fade rate of 0.04% per cycle over 1500 cycles at a practical C/2 rate. More importantly, it exhibits good high-sulfur-loading areal capacity (up to 3.5 mAh cm(-2)) with stable cell performance. We demonstrate the strong chemical interaction of g-C3N4 with polysulfides using a combination of spectroscopic experimental studies and first-principles calculations. The 53.5% concentration of accessible pyridinic nitrogen polysulfide adsorption sites is shown to be key for the greatly improved cycling performance compared to that of N-doped carbons. PMID:26841116

  17. Choosing a density functional for modeling adsorptive hydrogen storage: reference quantum mechanical calculations and a comparison of dispersion-corrected density functionals.

    PubMed

    Kocman, Mikuláš; Jurečka, Petr; Dubecký, Matúš; Otyepka, Michal; Cho, Yeonchoo; Kim, Kwang S

    2015-03-01

    Hydrogen storage in carbonaceous materials and their derivatives is currently a widely investigated topic. The rational design of novel adsorptive materials is often attempted with the help of computational chemistry tools, in particular density functional theory (DFT). However, different exchange-correlation functionals provide a very wide range of hydrogen binding energies. The aim of this article is to offer high level QM reference data based on coupled-cluster singles and doubles calculations with perturbative triple excitations, CCSD(T), and a complete basis set limit estimate that can be used to assess the accuracy of various DFT-based predictions. For one complex, the CCSD(T) result is verified against diffusion quantum Monte Carlo calculations. Reference binding curves are calculated for two model compounds representing weak and strong hydrogen adsorption: coronene (-4.7 kJ mol(-1) per H2), and coronene modified with boron and lithium (-14.3 kJ mol(-1)). The reference data are compared to results obtained with widely used density functionals including pure DFT, M06, DFT-D3, PBE-TS, PBE + MBD, optB88-vdW, vdW-DF, vdW-DF2 and VV10. We find that whereas DFT-D3 shows excellent results for weak hydrogen adsorption on coronene, most of the less empirical density based dispersion functionals except VV10 overestimate this interaction. On the other hand, some of the less empirical density based dispersion functionals better describe stronger binding in the more polar coroB2Li22H2 complex which is one of realistic models for high-capacity hydrogen storage materials. Our results may serve as a guide for choosing suitable DFT methods for quickly evaluating hydrogen binding potential and as a reference for assessing the accuracy of the previously published DFT results. PMID:25655486

  18. Effect of carbonation temperature on CO2 adsorption capacity of CaO derived from micro/nanostructured aragonite CaCO3

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    Recent years, CaO-based synthetic materials have been attracted attention as potential adsorbents for CO2 capture mainly due to their high CO2 adsorption capacity. In this study, micro/nanostructured aragonite CaCO3 was synthesized by a simple hydrothermal method with using polyacrylamide (PAM). The structural, morphological and thermal properties of the synthesized sample were investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and thermogravimetry analysis (TG-DTA). The XRD and FESEM results showed that the obtained sample was aragonite CaCO3 with aggregated nanorods and microspheres composed of nanorods. A TG-DTA apparatus with Thermoplus 2 software was used to investigate the effect of carbonation temperature on the CO2 adsorption capacity of CaO derived from aragonite CaCO3 sample. At 300 °C, the sample reached the CO2 adsorption capacity of 0.098 g-CO2/g-adsorbent, whereas the sample achieved the highest capacity of 0.682 g-CO2/g-adsorbent at 700 °C. The results showed that the carbonation temperature significantly influenced on the CO2 adsorption capacity of the CaO derived from aragonite CaCO3.

  19. High adsorption capacity of two Zn-based metal-organic frameworks by ultrasound assisted synthesis.

    PubMed

    Masoomi, Mohammad Yaser; Bagheri, Minoo; Morsali, Ali

    2016-11-01

    Micro- and nano-rods and plates of two 3D, porous Zn(II)-based metal-organic frameworks [Zn(oba)(4-bpdh)0.5]n·(DMF)1.5 (TMU-5) and [Zn(oba)(4-bpmb)0.5]n (DMF)1.5 (TMU-6) were prepared by sonochemical process and characterized by scanning electron microscopy, X-ray powder diffraction and IR spectroscopy. These MOFs were synthesized using a non-linear dicarboxylate (H2oba=4,4-oxybisbenzoic acid) and two linear N-donor (4-bpdh=2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene and 4-bpmb=N(1),N(4)-bis((pyridin-4-yl)methylene)benzene-1,4-diamine) ligands by ultrasonic irradiation. Sonication time and concentration of initial reagents influencing size and morphology of nano-structured MOFs, were also studied. Calcination of TMU-5 and TMU-6 at 550°C under air atmosphere yields ZnO nanoparticles. TMU-5 and TMU-6 exhibited maximum percent adsorption of 96.2% and 92.8% of 100ppm rhodamine B dye, respectively, which obeys first order reaction kinetics. PMID:27245956

  20. Ethane/ethylene adsorption on carbon nanotubes: temperature and size effects on separation capacity.

    PubMed

    Albesa, Alberto G; Rafti, Matías; Rawat, Dinesh S; Vicente, José Luis; Migone, Aldo D

    2012-01-24

    We present the results of Monte Carlo simulations of the adsorption of single-component ethane and ethylene and of equimolar mixtures of these two gases on bundles of closed, single-walled carbon nanotubes. Two types of nanotube bundles were used in the simulations: homogeneous (i.e., those in which all the nanotubes have identical diameters) and heterogeneous (those in which nanotubes of different diameters are allowed). We found that at the same pressure and temperature more ethane than ethylene adsorbs on the bundles over the entire range of pressures and temperatures explored. The simulation results for the equimolar mixtures show that the pressure at which maximum separation is attained is a very sensitive function of the diameter of the nanotubes present in the bundles. Simulations using heterogeneous bundles yield better agreement with single-component experimental data for isotherms and isosteric heats than those obtained from simulations using homogeneous bundles. Possible applications of nanotubes in gas separation are discussed. We explored the effect of the diameter of the nanotubes on the separation ability of these sorbents, both for the internal and for the external sites. We found that substrate selectivity is a decreasing function of temperature. PMID:22168522

  1. Adsorption and diffusion of hydrogen on Pd(211) and Pd(111): Results from first-principles electronic structure calculations

    NASA Astrophysics Data System (ADS)

    Hong, Sampyo; Rahman, Talat S.

    2007-04-01

    We have carried out first-principles calculations of H adsorption on Pd(211) using density-functional theory with the generalized gradient approximation in the plane-wave basis to find out that the most preferred is the threefold hollow site on the terrace of Pd(211) with an adsorption energy of 0.52eV : the hcp and fcc sites being almost energetically equally favorable. For subsurface H adsorption on Pd(211), the octahedral site with an adsorption energy of 0.19eV is slightly more favorable than the tetrahedral site (0.18eV) . Our calculated activation energy barrier for H to diffuse from the preferred surface site to the subsurface one on Pd(211) is 0.33eV , as compared with 0.41eV on Pd(111). Thus, there is an enhancement of the probability of finding subsurface hydrogen in Pd(211). Additionally, we find the diffusion barriers for H on the terraces of Pd(211) to be 0.11eV , while that along the step edge to be only 0.05eV and that within the second layer (subsurface) to be 0.15eV .

  2. Potential of mean force calculation of the free energy of adsorption of Type I winter flounder antifreeze protein on ice

    NASA Astrophysics Data System (ADS)

    Battle, Keith; Alan Salter, E.; Wesley Edmunds, R.; Wierzbicki, Andrzej

    2010-04-01

    Antifreeze proteins (AFPs) are a unique class of proteins that inhibit ice growth without changing the melting point of ice. In this work, we study the detailed molecular mechanism of interactions between the hydrophobic side of the winter flounder (WF) AFP and two mutants, AAAA and SSSS, in which threonine residues are substituted by serines and alanines, respectively. Umbrella sampling molecular dynamics simulations of the separation of the proteins from the (2 0 1) surface in an explicit water box is carried out to calculate the potential of mean force free energies of adsorption using AMBER10i. We estimate wild-type WF's free energy of adsorption to ice to be about -12.0 kcal/mol. Gas-phase pseudopotential plane-wave calculations of methane adsorption onto select surfaces of ice are also carried out under periodic boundary conditions to address the possible enthalpic role of WF's methyl groups in binding. The contributions of hydrophobic residues to the free energy of adsorption are discussed.

  3. Calculation of adsorption free energy for solute-surface interactions using biased replica-exchange molecular dynamics

    PubMed Central

    Wang, Feng; Stuart, Steven J.; Latour, Robert A.

    2009-01-01

    The adsorption behavior of a biomolecule, such as a peptide or protein, to a functionalized surface is of fundamental importance for a broad range of applications in biotechnology. The adsorption free energy for these types of interactions can be determined from a molecular dynamics simulation using the partitioning between adsorbed and nonadsorbed states, provided that sufficient sampling of both states is obtained. However, if interactions between the solute and the surface are strong, the solute will tend to be trapped near the surface during the simulation, thus preventing the adsorption free energy from being calculated by this method. This situation occurs even when using an advanced sampling algorithm such as replica-exchange molecular dynamics (REMD). In this paper, the authors demonstrate the fundamental basis of this problem using a model system consisting of one sodium ion (Na+) as the solute positioned over a surface functionalized with one negatively charged group (COO−) in explicit water. With this simple system, the authors show that sufficient sampling in the coordinate normal to the surface cannot be obtained by conventional REMD alone. The authors then present a method to overcome this problem through the use of an adaptive windowed-umbrella sampling technique to develop a biased-energy function that is combined with REMD. This approach provides an effective method for the calculation of adsorption free energy for solute-surface interactions. PMID:19768127

  4. Predicting enzyme adsorption to lignin films by calculating enzyme surface hydrophobicity.

    PubMed

    Sammond, Deanne W; Yarbrough, John M; Mansfield, Elisabeth; Bomble, Yannick J; Hobdey, Sarah E; Decker, Stephen R; Taylor, Larry E; Resch, Michael G; Bozell, Joseph J; Himmel, Michael E; Vinzant, Todd B; Crowley, Michael F

    2014-07-25

    The inhibitory action of lignin on cellulase cocktails is a major challenge to the biological saccharification of plant cell wall polysaccharides. Although the mechanism remains unclear, hydrophobic interactions between enzymes and lignin are hypothesized to drive adsorption. Here we evaluate the role of hydrophobic interactions in enzyme-lignin binding. The hydrophobicity of the enzyme surface was quantified using an estimation of the clustering of nonpolar atoms, identifying potential interaction sites. The adsorption of enzymes to lignin surfaces, measured using the quartz crystal microbalance, correlates to the hydrophobic cluster scores. Further, these results suggest a minimum hydrophobic cluster size for a protein to preferentially adsorb to lignin. The impact of electrostatic contribution was ruled out by comparing the isoelectric point (pI) values to the adsorption of proteins to lignin surfaces. These results demonstrate the ability to predict enzyme-lignin adsorption and could potentially be used to design improved cellulase cocktails, thus lowering the overall cost of biofuel production. PMID:24876380

  5. Predicting Enzyme Adsorption to Lignin Films by Calculating Enzyme Surface Hydrophobicity*

    PubMed Central

    Sammond, Deanne W.; Yarbrough, John M.; Mansfield, Elisabeth; Bomble, Yannick J.; Hobdey, Sarah E.; Decker, Stephen R.; Taylor, Larry E.; Resch, Michael G.; Bozell, Joseph J.; Himmel, Michael E.; Vinzant, Todd B.; Crowley, Michael F.

    2014-01-01

    The inhibitory action of lignin on cellulase cocktails is a major challenge to the biological saccharification of plant cell wall polysaccharides. Although the mechanism remains unclear, hydrophobic interactions between enzymes and lignin are hypothesized to drive adsorption. Here we evaluate the role of hydrophobic interactions in enzyme-lignin binding. The hydrophobicity of the enzyme surface was quantified using an estimation of the clustering of nonpolar atoms, identifying potential interaction sites. The adsorption of enzymes to lignin surfaces, measured using the quartz crystal microbalance, correlates to the hydrophobic cluster scores. Further, these results suggest a minimum hydrophobic cluster size for a protein to preferentially adsorb to lignin. The impact of electrostatic contribution was ruled out by comparing the isoelectric point (pI) values to the adsorption of proteins to lignin surfaces. These results demonstrate the ability to predict enzyme-lignin adsorption and could potentially be used to design improved cellulase cocktails, thus lowering the overall cost of biofuel production. PMID:24876380

  6. Dye adsorption behavior of Luffa cylindrica fibers.

    PubMed

    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. Rational design of sulphur host materials for Li-S batteries: correlating lithium polysulphide adsorptivity and self-discharge capacity loss.

    PubMed

    Hart, Connor J; Cuisinier, Marine; Liang, Xiao; Kundu, Dipan; Garsuch, Arnd; Nazar, Linda F

    2015-02-11

    A versatile, cost-effective electrochemical analysis strategy is described that determines the specific S(n)(2-) adsorptivity of materials, and allows prediction of the long-term performance of sulphur composite electrodes in Li-S cells. Measurement of nine different materials with varying surface area, and hydrophobicity using this protocol determined optimum properties for capacity stabilization. PMID:25562067

  8. Adsorption and diffusion of Ru adatoms on Ru(0001)-supported graphene: Large-scale first-principles calculations

    DOE PAGESBeta

    Han, Yong; Evans, James W.

    2015-10-27

    Large-scale first-principles density functional theory calculations are performed to investigate the adsorption and diffusion of Ru adatoms on monolayer graphene (G) supported on Ru(0001). The G sheet exhibits a periodic moiré-cell superstructure due to lattice mismatch. Within a moiré cell, there are three distinct regions: fcc, hcp, and mound, in which the C6-ring center is above a fcc site, a hcp site, and a surface Ru atom of Ru(0001), respectively. The adsorption energy of a Ru adatom is evaluated at specific sites in these distinct regions. We find the strongest binding at an adsorption site above a C atom inmore » the fcc region, next strongest in the hcp region, then the fcc-hcp boundary (ridge) between these regions, and the weakest binding in the mound region. Behavior is similar to that observed from small-unit-cell calculations of Habenicht et al. [Top. Catal. 57, 69 (2014)], which differ from previous large-scale calculations. We determine the minimum-energy path for local diffusion near the center of the fcc region and obtain a local diffusion barrier of ~0.48 eV. We also estimate a significantly lower local diffusion barrier in the ridge region. These barriers and information on the adsorption energy variation facilitate development of a realistic model for the global potential energy surface for Ru adatoms. Furthermore, this in turn enables simulation studies elucidating diffusion-mediated directed-assembly of Ru nanoclusters during deposition of Ru on G/Ru(0001).« less

  9. Adsorption and diffusion of Ru adatoms on Ru(0001)-supported graphene: Large-scale first-principles calculations

    SciTech Connect

    Han, Yong; Evans, James W.

    2015-10-27

    Large-scale first-principles density functional theory calculations are performed to investigate the adsorption and diffusion of Ru adatoms on monolayer graphene (G) supported on Ru(0001). The G sheet exhibits a periodic moiré-cell superstructure due to lattice mismatch. Within a moiré cell, there are three distinct regions: fcc, hcp, and mound, in which the C6-ring center is above a fcc site, a hcp site, and a surface Ru atom of Ru(0001), respectively. The adsorption energy of a Ru adatom is evaluated at specific sites in these distinct regions. We find the strongest binding at an adsorption site above a C atom in the fcc region, next strongest in the hcp region, then the fcc-hcp boundary (ridge) between these regions, and the weakest binding in the mound region. Behavior is similar to that observed from small-unit-cell calculations of Habenicht et al. [Top. Catal. 57, 69 (2014)], which differ from previous large-scale calculations. We determine the minimum-energy path for local diffusion near the center of the fcc region and obtain a local diffusion barrier of ~0.48 eV. We also estimate a significantly lower local diffusion barrier in the ridge region. These barriers and information on the adsorption energy variation facilitate development of a realistic model for the global potential energy surface for Ru adatoms. Furthermore, this in turn enables simulation studies elucidating diffusion-mediated directed-assembly of Ru nanoclusters during deposition of Ru on G/Ru(0001).

  10. Water adsorption in SAPO-34: elucidating the role of local heterogeneities and defects using dispersion-corrected DFT calculations.

    PubMed

    Fischer, Michael

    2015-10-14

    The chabazite-type silicoaluminophosphate SAPO-34 is a promising adsorbent for applications in thermal energy storage using water adsorption-desorption cycles. In order to develop a microscopic understanding of the impact of local heterogeneities and defects on the water adsorption properties, the interaction of different models of SAPO-34 with water was studied using dispersion-corrected density-functional theory (DFT-D) calculations. In addition to SAPO-34 with isolated silicon atoms, the calculations considered models incorporating two types of heterogeneities (silicon islands, aluminosilicate domains), and two defect-containing (partially and fully desilicated) systems. DFT-D optimisations were performed for systems with small amounts of adsorbed water, in which all H2O molecules can interact with framework protons, and systems with large amounts of adsorbed water (30 H2O molecules per unit cell). At low loadings, the host-guest interaction energy calculated for SAPO-34 with isolated Si atoms amounts to approximately -90 kJ mol(-1). While the presence of local heterogeneities leads to the creation of some adsorption sites that are energetically slightly more favourable, the interaction strength is drastically reduced in systems with defects. At high water loadings, energies in the range of -70 kJ mol(-1) are obtained for all models. The DFT-D interaction energies are in good agreement with experimentally measured heats of water adsorption. A detailed analysis of the equilibrium structures was used to gain insights into the binding modes at low coverages, and to assess the extent of framework deprotonation and changes in the coordination environment of aluminium atoms at high water loadings. PMID:26352329

  11. Adsorption and diffusion of Ru adatoms on Ru(0001)-supported graphene: Large-scale first-principles calculations

    SciTech Connect

    Han, Yong; Evans, James W.

    2015-10-28

    Large-scale first-principles density functional theory calculations are performed to investigate the adsorption and diffusion of Ru adatoms on monolayer graphene (G) supported on Ru(0001). The G sheet exhibits a periodic moiré-cell superstructure due to lattice mismatch. Within a moiré cell, there are three distinct regions: fcc, hcp, and mound, in which the C{sub 6}-ring center is above a fcc site, a hcp site, and a surface Ru atom of Ru(0001), respectively. The adsorption energy of a Ru adatom is evaluated at specific sites in these distinct regions. We find the strongest binding at an adsorption site above a C atom in the fcc region, next strongest in the hcp region, then the fcc-hcp boundary (ridge) between these regions, and the weakest binding in the mound region. Behavior is similar to that observed from small-unit-cell calculations of Habenicht et al. [Top. Catal. 57, 69 (2014)], which differ from previous large-scale calculations. We determine the minimum-energy path for local diffusion near the center of the fcc region and obtain a local diffusion barrier of ∼0.48 eV. We also estimate a significantly lower local diffusion barrier in the ridge region. These barriers and information on the adsorption energy variation facilitate development of a realistic model for the global potential energy surface for Ru adatoms. This in turn enables simulation studies elucidating diffusion-mediated directed-assembly of Ru nanoclusters during deposition of Ru on G/Ru(0001)

  12. Direct observation of solid-phase adsorbate concentration profile in powdered activated carbon particle to elucidate mechanism of high adsorption capacity on super-powdered activated carbon.

    PubMed

    Ando, Naoya; Matsui, Yoshihiko; Matsushita, Taku; Ohno, Koichi

    2011-01-01

    Decreasing the particle size of powdered activated carbon (PAC) by pulverization increases its adsorption capacities for natural organic matter (NOM) and polystyrene sulfonate (PSS, which is used as a model adsorbate). A shell adsorption mechanism in which NOM and PSS molecules do not completely penetrate the adsorbent particle and instead preferentially adsorb near the outer surface of the particle has been proposed as an explanation for this adsorption capacity increase. In this report, we present direct evidence to support the shell adsorption mechanism. PAC particles containing adsorbed PSS were sectioned with a focused ion beam, and the solid-phase PSS concentration profiles of the particle cross-sections were directly observed by means of field emission-scanning electron microscopy/energy-dispersive X-ray spectrometry (FE-SEM/EDXS). X-ray emission from sulfur, an index of PSS concentration, was higher in the shell region than in the inner region of the particles. The X-ray emission profile observed by EDXS did not agree completely with the solid-phase PSS concentration profile predicted by shell adsorption model analysis of the PSS isotherm data, but the observed and predicted profiles were not inconsistent when the analytical errors were considered. These EDXS results provide the first direct evidence that PSS is adsorbed mainly in the vicinity of the external surface of the PAC particles, and thus the results support the proposition that the increase in NOM and PSS adsorption capacity with decreasing particle size is due to the increase in external surface area on which the molecules can be adsorbed. PMID:20851447

  13. The role of counter ions in nano-hematite synthesis: Implications for surface area and selenium adsorption capacity.

    PubMed

    Lounsbury, Amanda W; Yamani, Jamila S; Johnston, Chad P; Larese-Casanova, Philip; Zimmerman, Julie B

    2016-06-01

    Nano metal oxides are of interest for aqueous selenium (Se) remediation, and as such, nano-hematite (nα-Fe2O3) was examined for use as a Se adsorbent. The effect of surface area on adsorption was also studied. nα-Fe2O3 particles were synthesized from Fe(NO3)3 and FeCl3 via forced hydrolysis. The resulting particles have similar sizes, morphologies, aggregate size, pore size, and PZC. The nα-Fe2O3 from FeCl3 (nα-Fe2O3-C) differs from the nα-Fe2O3 from Fe(NO3)3 (nα-Fe2O3-N) with a ∼25±2m(2)/g greater surface area. Selenite Se(IV) adsorption capacity on nα-Fe2O3 has a qmax ∼17mg/g for the freeze-dried and re-suspended nα-Fe2O3. The Δqmax for nα-Fe2O3 from Fe(NO3)3 and FeCl3 that remained in suspension was 4.6mg/g. For selenate Se(VI), the freeze-dried and re-suspended particles realize a Δqmax= 1.5mg/g for nα-Fe2O3 from Fe(NO3)3 and FeCl3. The nα-Fe2O3 from Fe(NO3)3 and FeCl3 that remained in suspension demonstrated Se(VI) Δqmax=5.4mg/g. In situ ATR-FTIR isotherm measurements completed for Se(VI) at a pH 6 suggest that Se(VI) forms primarily outer-sphere complexes with nα-Fe2O3 synthesized from both salts. PMID:26905609

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

    NASA Astrophysics Data System (ADS)

    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.

  15. The effect of low-NO{sub x} combustion on residual carbon in fly ash and its adsorption capacity for air entrainment admixtures in concrete

    SciTech Connect

    Pedersen, K.H.; Jensen, A.D.; Dam-Johansen, K.

    2010-02-15

    Fly ash from pulverized coal combustion contains residual carbon that can adsorb the air-entraining admixtures (AEAs) added to control the air entrainment in concrete. This is a problem that has increased by the implementation of low-NO{sub x} combustion technologies. In this work, pulverized fuel has been combusted in an entrained flow reactor to test the impact of changes in operating conditions and fuel type on the AEA adsorption of ash and NO{sub x} formation. Increased oxidizing conditions, obtained by improved fuel-air mixing or higher excess air, decreased the AEA requirements of the produced ash by up to a factor of 25. This was due to a lower carbon content in the ash and a lower specific AEA adsorptivity of the carbon. The latter was suggested to be caused by changes in the adsorption properties of the unburned char and a decreased formation of soot, which was found to have a large AEA adsorption capacity based on measurements on a carbon black. The NO{sub x} formation increased by up to three times with more oxidizing conditions and thus, there was a trade-off between the AEA requirements of the ash and NO{sub x} formation. The type of fuel had high impact on the AEA adsorption behavior of the ash. Ashes produced from a Columbian and a Polish coal showed similar AEA requirements, but the specific AEA adsorptivity of the carbon in the Columbian coal ash was up to six times higher. The AEA requirements of a South African coal ash was unaffected by the applied operating conditions and showed up to 12 times higher AEA adsorption compared to the two other coal ashes. This may be caused by larger particles formed by agglomeration of the primary coal particles in the feeding phase or during the combustion process, which gave rise to increased formation of soot. (author)

  16. Phosphate adsorption on lanthanum loaded biochar.

    PubMed

    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

  17. STATISTICAL COMPARISON OF THE EFFECT OF RELATIVE AND ABSOLUTE HUMIDITY ON FIXED-BED CARBON ADSORPTION CAPACITY

    EPA Science Inventory

    The paper describes statistical methods used to evaluate data for toluene (at several typical operating temperatures and humidity levels) and to determine which measure of humidity (relative or absolute) is more important in determining carbon adsorption efficiency. The water con...

  18. Improvement of pesticide adsorption capacity of cellulose fibre by high-energy irradiation-initiated grafting of glycidyl methacrylate

    NASA Astrophysics Data System (ADS)

    Takács, Erzsébet; Wojnárovits, László; Koczog Horváth, Éva; Fekete, Tamás; Borsa, Judit

    2012-09-01

    Cellulose as a renewable raw material was used for preparation of adsorbent of organic impurities in wastewater treatment. Hydrophobic surface of cellulose substrate was developed by grafting glycidyl methacrylate in simultaneous grafting using gamma irradiation initiation. Water uptake of cellulose significantly decreased while adsorption of phenol and a pesticide molecule (2,4-dichlorophenoxyacetic acid: 2,4-D) increased upon grafting. Adsorption equilibrium data fitted the Freundlich isotherm for both solutes.

  19. A Initio Calculations Performed on Carbon Monoxide Adsorption on the IRON(100) Surface and Complementing Theoretical Techniques

    NASA Astrophysics Data System (ADS)

    Meehan, Timothy Erickson

    1992-01-01

    Unrestricted Hartree-Fock calculations were performed on Fe_{x}CO clusters to model the CO(alpha_1), CO(alpha_2), and CO( alpha_3) adsorptions on the Fe(100) surface. Clusters of FeCO(C_{4v}) and a multiplicity of 5, Fe_2 CO(C_{2v}) and a multiplicity of 7, and Fe_2CO(C _{s}) and a multiplicity of 7, were constructed to model, respectively, the adsorption for the on top site, bridging site, and tilted CO structure at the 4-fold site. The CO position was optimized with respect to the Fe bulk distances using gradient techniques and the partial geometry optimization. CO stretching frequencies were calculated for each optimized geometry, and we find no evidence supporting CO adsorption in the bridging site. Using a full basis set the calculated CO stretching frequencies for the FeCO(C_{4v}), Fe_2CO(C_ {2v}), and the Fe_2 CO(C_{s}) clusters are 1992, 1767, and 771 cm^{ -1}, respectively. The CSOV analysis was executed to analyze the major orbital interactions between the CO and Fe_{x} clusters. For both Fe_2CO clusters, the CO pi^* perpendicular to the Fe _2 axis had a more significant contribution involving the pi backdonation from the Fe_2 clusters. Furthermore, the spin minority d electrons are mainly responsible for the pi backdonation. Due to problems with SCF convergence incurred during the Fe_{x}CO studies, we were forced to investigate a number of different techniques to achieve SCF convergence. Therefore, techniques that generate starting guesses of the eigenvectors for the SCF procedure and techniques used to accelerate SCF convergence are reviewed. The standard guesses of H _{core} and charge build -up are examined, and we introduce a new incremental cluster method for generating starting guesses for large clusters. The standard techniques of extrapolation, DIIS, damping, level shifting, restrict, and symmetry blocking are examined, and we also developed the hacker method and partial geometry optimization as new techniques to achieve SCF convergence. Results

  20. Novel Anthropometry-Based Calculation of the Body Heat Capacity in the Korean Population.

    PubMed

    Pham, Duong Duc; Lee, Jeong Hoon; Lee, Young Boum; Park, Eun Seok; Kim, Ka Yul; Song, Ji Yeon; Kim, Ji Eun; Leem, Chae Hun

    2015-01-01

    Heat capacity (HC) has an important role in the temperature regulation process, particularly in dealing with the heat load. The actual measurement of the body HC is complicated and is generally estimated by body-composition-specific data. This study compared the previously known HC estimating equations and sought how to define HC using simple anthropometric indices such as weight and body surface area (BSA) in the Korean population. Six hundred participants were randomly selected from a pool of 902 healthy volunteers aged 20 to 70 years for the training set. The remaining 302 participants were used for the test set. Body composition analysis using multi-frequency bioelectrical impedance analysis was used to access body components including body fat, water, protein, and mineral mass. Four different HCs were calculated and compared using a weight-based HC (HC_Eq1), two HCs estimated from fat and fat-free mass (HC_Eq2 and HC_Eq3), and an HC calculated from fat, protein, water, and mineral mass (HC_Eq4). HC_Eq1 generally produced a larger HC than the other HC equations and had a poorer correlation with the other HC equations. HC equations using body composition data were well-correlated to each other. If HC estimated with HC_Eq4 was regarded as a standard, interestingly, the BSA and weight independently contributed to the variation of HC. The model composed of weight, BSA, and gender was able to predict more than a 99% variation of HC_Eq4. Validation analysis on the test set showed a very high satisfactory level of the predictive model. In conclusion, our results suggest that gender, BSA, and weight are the independent factors for calculating HC. For the first time, a predictive equation based on anthropometry data was developed and this equation could be useful for estimating HC in the general Korean population without body-composition measurement. PMID:26529594

  1. Novel Anthropometry-Based Calculation of the Body Heat Capacity in the Korean Population

    PubMed Central

    Pham, Duong Duc; Lee, Jeong Hoon; Lee, Young Boum; Park, Eun Seok; Kim, Ka Yul; Song, Ji Yeon; Kim, Ji Eun; Leem, Chae Hun

    2015-01-01

    Heat capacity (HC) has an important role in the temperature regulation process, particularly in dealing with the heat load. The actual measurement of the body HC is complicated and is generally estimated by body-composition-specific data. This study compared the previously known HC estimating equations and sought how to define HC using simple anthropometric indices such as weight and body surface area (BSA) in the Korean population. Six hundred participants were randomly selected from a pool of 902 healthy volunteers aged 20 to 70 years for the training set. The remaining 302 participants were used for the test set. Body composition analysis using multi-frequency bioelectrical impedance analysis was used to access body components including body fat, water, protein, and mineral mass. Four different HCs were calculated and compared using a weight-based HC (HC_Eq1), two HCs estimated from fat and fat-free mass (HC_Eq2 and HC_Eq3), and an HC calculated from fat, protein, water, and mineral mass (HC_Eq4). HC_Eq1 generally produced a larger HC than the other HC equations and had a poorer correlation with the other HC equations. HC equations using body composition data were well-correlated to each other. If HC estimated with HC_Eq4 was regarded as a standard, interestingly, the BSA and weight independently contributed to the variation of HC. The model composed of weight, BSA, and gender was able to predict more than a 99% variation of HC_Eq4. Validation analysis on the test set showed a very high satisfactory level of the predictive model. In conclusion, our results suggest that gender, BSA, and weight are the independent factors for calculating HC. For the first time, a predictive equation based on anthropometry data was developed and this equation could be useful for estimating HC in the general Korean population without body-composition measurement. PMID:26529594

  2. Formation of High-Capacity Protein-Adsorbing Membranes Through Simple Adsorption of Poly(acrylic acid)-Containing Films at low pH

    PubMed Central

    Bhattacharjee, Somnath; Dong, Jinlan; Ma, Yiding; Hovde, Stacy; Geiger, James H; Baker, Gregory L.; Bruening, Merlin L.

    2012-01-01

    Layer-by-layer polyelectrolyte adsorption is a simple, convenient method for introducing ion-exchange sites in porous membranes. This study demonstrates that adsorption of poly(acrylic acid) (PAA)-containing films at pH 3 rather than pH 5 increases the protein-binding capacity of such polyelectrolyte-modified membranes 3- to 6-fold. The low adsorption pH generates a high density of –COOH groups that function as either ion-exchange sites or points for covalent immobilization of metal-ion complexes that selectively bind tagged proteins. When functionalized with nitrilotriacetate (NTA)-Ni2+ complexes, membranes containing PAA/polyethyleneimine (PEI)/PAA films bind 93 mg of histidine6-tagged (His-tagged) ubiquitin per cm3 of membrane. Additionally these membranes isolate His-tagged COP9 signalosome complex subunit 8 from cell extracts and show >90% recovery of His-tagged ubiquitin. Although modification with polyelectrolyte films occurs by simply passing polyelectrolyte solutions through the membrane for as little as 5 min, with low-pH deposition the protein binding capacities of such membranes are as high as for membranes modified with polymer brushes and 2–3 fold higher than for commercially available IMAC resins. Moreover, the buffer permeabilities of polyelectrolyte-modified membranes that bind His-tagged protein are ~30% of the corresponding permeabilities of unmodified membranes, so protein capture can occur rapidly with low pressure drops. Even at a solution linear velocity of 570 cm/h, membranes modified with PAA/PEI/PAA exhibit a lysozyme dynamic binding capacity (capacity at 10% breakthrough) of ~ 40 mg/cm3. Preliminary studies suggest that these membranes are stable under depyrogenation conditions (1 M NaOH). PMID:22468687

  3. Pore size distribution calculation from 1H NMR signal and N2 adsorption-desorption techniques

    NASA Astrophysics Data System (ADS)

    Hassan, Jamal

    2012-09-01

    The pore size distribution (PSD) of nano-material MCM-41 is determined using two different approaches: N2 adsorption-desorption and 1H NMR signal of water confined in silica nano-pores of MCM-41. The first approach is based on the recently modified Kelvin equation [J.V. Rocha, D. Barrera, K. Sapag, Top. Catal. 54(2011) 121-134] which deals with the known underestimation in pore size distribution for the mesoporous materials such as MCM-41 by introducing a correction factor to the classical Kelvin equation. The second method employs the Gibbs-Thompson equation, using NMR, for melting point depression of liquid in confined geometries. The result shows that both approaches give similar pore size distribution to some extent, and also the NMR technique can be considered as an alternative direct method to obtain quantitative results especially for mesoporous materials. The pore diameter estimated for the nano-material used in this study was about 35 and 38 Å for the modified Kelvin and NMR methods respectively. A comparison between these methods and the classical Kelvin equation is also presented.

  4. Surfactant-free synthesis of octahedral ZnO/ZnFe2O4 heterostructure with ultrahigh and selective adsorption capacity of malachite green

    PubMed Central

    Liu, Jue; Zeng, Min; Yu, Ronghai

    2016-01-01

    A new octahedral ZnO/ZnFe2O4 heterostructure has been fabricated through a facile surfactant-free solvothermal method followed by thermal treatment. It exhibits a record-high adsorption capacity (up to 4983.0 mg·g−1) of malachite green (MG), which is a potentially harmful dye in prevalence and should be removed from wastewater and other aqueous solutions before discharging into the environment. The octahedral ZnO/ZnFe2O4 heterostructure also demonstrates strong selective adsorption towards MG from two kinds of mixed solutions: MG/methyl orange (MO) and MG/rhodamine B (RhB) mixtures, indicating its promise in water treatment. PMID:27142194

  5. Surfactant-free synthesis of octahedral ZnO/ZnFe2O4 heterostructure with ultrahigh and selective adsorption capacity of malachite green

    NASA Astrophysics Data System (ADS)

    Liu, Jue; Zeng, Min; Yu, Ronghai

    2016-05-01

    A new octahedral ZnO/ZnFe2O4 heterostructure has been fabricated through a facile surfactant-free solvothermal method followed by thermal treatment. It exhibits a record-high adsorption capacity (up to 4983.0 mg·g‑1) of malachite green (MG), which is a potentially harmful dye in prevalence and should be removed from wastewater and other aqueous solutions before discharging into the environment. The octahedral ZnO/ZnFe2O4 heterostructure also demonstrates strong selective adsorption towards MG from two kinds of mixed solutions: MG/methyl orange (MO) and MG/rhodamine B (RhB) mixtures, indicating its promise in water treatment.

  6. Surfactant-free synthesis of octahedral ZnO/ZnFe2O4 heterostructure with ultrahigh and selective adsorption capacity of malachite green.

    PubMed

    Liu, Jue; Zeng, Min; Yu, Ronghai

    2016-01-01

    A new octahedral ZnO/ZnFe2O4 heterostructure has been fabricated through a facile surfactant-free solvothermal method followed by thermal treatment. It exhibits a record-high adsorption capacity (up to 4983.0 mg·g(-1)) of malachite green (MG), which is a potentially harmful dye in prevalence and should be removed from wastewater and other aqueous solutions before discharging into the environment. The octahedral ZnO/ZnFe2O4 heterostructure also demonstrates strong selective adsorption towards MG from two kinds of mixed solutions: MG/methyl orange (MO) and MG/rhodamine B (RhB) mixtures, indicating its promise in water treatment. PMID:27142194

  7. 30 CFR 254.44 - Calculating response equipment effective daily recovery capacities.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., DEPARTMENT OF THE INTERIOR OFFSHORE OIL-SPILL RESPONSE REQUIREMENTS FOR FACILITIES LOCATED SEAWARD OF THE... effective daily recovery capacity of the response equipment identified in your response plan that you would... capacity of the equipment by multiplying the manufacturer's rated throughput capacity over a 24-hour...

  8. 30 CFR 254.44 - Calculating response equipment effective daily recovery capacities.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., DEPARTMENT OF THE INTERIOR OFFSHORE OIL-SPILL RESPONSE REQUIREMENTS FOR FACILITIES LOCATED SEAWARD OF THE... effective daily recovery capacity of the response equipment identified in your response plan that you would... capacity of the equipment by multiplying the manufacturer's rated throughput capacity over a 24-hour...

  9. 30 CFR 254.44 - Calculating response equipment effective daily recovery capacities.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., DEPARTMENT OF THE INTERIOR OFFSHORE OIL-SPILL RESPONSE REQUIREMENTS FOR FACILITIES LOCATED SEAWARD OF THE... effective daily recovery capacity of the response equipment identified in your response plan that you would... capacity of the equipment by multiplying the manufacturer's rated throughput capacity over a 24-hour...

  10. 40 CFR Appendix D to Part 72 - Calculation of Potential Electric Output Capacity

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... boiler with a maximum design heat input capacity of 340 million Btu/hr. (2) One-third of the maximum design heat input capacity is 113.3 mmBtu/hr. The one-third factor relates to the thermodynamic... Output Capacity D Appendix D to Part 72 Protection of Environment ENVIRONMENTAL PROTECTION...

  11. Vehicle-to-grid power fundamentals: Calculating capacity and net revenue

    NASA Astrophysics Data System (ADS)

    Kempton, Willett; Tomić, Jasna

    As the light vehicle fleet moves to electric drive (hybrid, battery, and fuel cell vehicles), an opportunity opens for "vehicle-to-grid" (V2G) power. This article defines the three vehicle types that can produce V2G power, and the power markets they can sell into. V2G only makes sense if the vehicle and power market are matched. For example, V2G appears to be unsuitable for baseload power—the constant round-the-clock electricity supply—because baseload power can be provided more cheaply by large generators, as it is today. Rather, V2G's greatest near-term promise is for quick-response, high-value electric services. These quick-response electric services are purchased to balance constant fluctuations in load and to adapt to unexpected equipment failures; they account for 5-10% of electric cost—$ 12 billion per year in the US. This article develops equations to calculate the capacity for grid power from three types of electric drive vehicles. These equations are applied to evaluate revenue and costs for these vehicles to supply electricity to three electric markets (peak power, spinning reserves, and regulation). The results suggest that the engineering rationale and economic motivation for V2G power are compelling. The societal advantages of developing V2G include an additional revenue stream for cleaner vehicles, increased stability and reliability of the electric grid, lower electric system costs, and eventually, inexpensive storage and backup for renewable electricity.

  12. Adsorption of F2Cdbnd CFCl on TiO2 nano-powder: Structures, energetics and vibrational properties from DRIFT spectroscopy and periodic quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Tasinato, Nicola; Moro, Daniele; Stoppa, Paolo; Pietropolli Charmet, Andrea; Toninello, Piero; Giorgianni, Santi

    2015-10-01

    Photodegradation over titanium dioxide (TiO2) is a very appealing technology for removing environmental pollutants from the air, the adsorption interaction being the first step of the whole reaction pathway. In the present work the adsorption of F2Cdbnd CFCl (chlorotrifluoroethene, halon 1113), a compound used by industry and detected in the atmosphere, on a commercial TiO2 nano-powder is investigated experimentally by in situ DRIFT spectroscopy and theoretically through periodic ab initio calculations rooted in DFT. The spectra of the adsorbed molecule suggest that the anchoring to the surface mainly takes place through F atoms. Theoretically, five adsorption configurations for the molecule interacting with the anatase (1 0 1) surface are simulated at B3LYP level and for each of them, structures, binding energies and vibrational frequencies are derived. The interplay between theory and experiments shows the coexistence of different adsorption configurations, the foremost ones featuring the interaction of one F atom with a fivefold coordinated Ti4+ of the surface. These two adsorption models, which mostly differ for the orientation of the adsorbate with respect to the surface, feature a binding energy of -45.6 and -41.0 kJ mol-1 according to dispersion corrected DFT calculations. The favorable adsorption interaction appears as an important requirement toward the application of titanium dioxide technologies for the photocatalytic degradation of halon 1113.

  13. PREDICTING THE ADSORPTION CAPACITY OF ACTIVATED CARBON FOR EMERGING ORGANIC CONTAMINANTS FROM FUNDAMENTAL ADSORBENT AND ADSORBATE PROPERTIES - PRESENTATION

    EPA Science Inventory

    A quantitative structure-property relationship (QSPR) was developed and combined with the Polanyi-Dubinin-Manes model to predict adsorption isotherms of emerging contaminants on activated carbons with a wide range of physico-chemical properties. Affinity coefficients (βl

  14. Normal Mode Analysis in Zeolites: Toward an Efficient Calculation of Adsorption Entropies.

    PubMed

    De Moor, Bart A; Ghysels, An; Reyniers, Marie-Françoise; Van Speybroeck, Veronique; Waroquier, Michel; Marin, Guy B

    2011-04-12

    An efficient procedure for normal-mode analysis of extended systems, such as zeolites, is developed and illustrated for the physisorption and chemisorption of n-octane and isobutene in H-ZSM-22 and H-FAU using periodic DFT calculations employing the Vienna Ab Initio Simulation Package. Physisorption and chemisorption entropies resulting from partial Hessian vibrational analysis (PHVA) differ at most 10 J mol(-1) K(-1) from those resulting from full Hessian vibrational analysis, even for PHVA schemes in which only a very limited number of atoms are considered free. To acquire a well-conditioned Hessian, much tighter optimization criteria than commonly used for electronic energy calculations in zeolites are required, i.e., at least an energy cutoff of 400 eV, maximum force of 0.02 eV/Å, and self-consistent field loop convergence criteria of 10(-8) eV. For loosely bonded complexes the mobile adsorbate method is applied, in which frequency contributions originating from translational or rotational motions of the adsorbate are removed from the total partition function and replaced by free translational and/or rotational contributions. The frequencies corresponding with these translational and rotational modes can be selected unambiguously based on a mobile block Hessian-PHVA calculation, allowing the prediction of physisorption entropies within an accuracy of 10-15 J mol(-1) K(-1) as compared to experimental values. The approach presented in this study is useful for studies on other extended catalytic systems. PMID:26606357

  15. Evaluation of the isosteric heat of adsorption at zero coverage for hydrogen on activated carbons

    NASA Astrophysics Data System (ADS)

    Dohnke, E.; Beckner, M.; Romanos, J.; Olsen, R.; Wexler, C.; Pfeifer, P.

    2011-03-01

    Activated carbons made from corn cob show promise as materials for high-capacity hydrogen storage. As part of our characterization of these materials, we are interested in learning how different production methods affect the adsorption energies. In this talk, we will show how hydrogen adsorption isotherms may be used to calculate these adsorption energies at zero coverage using Henry's law. We will additionally discuss differences between the binding energy and the isosteric heat of adsorption by applying this analysis at different temperatures.

  16. Enhanced Adsorption of Hydroxyl- and Amino-Substituted Aromatic Chemicals to Nitrogen-Doped Multiwall Carbon Nanotubes: A Combined Batch and Theoretical Calculation Study.

    PubMed

    Zuo, Linzi; Guo, Yong; Li, Xiao; Fu, Heyun; Qu, Xiaolei; Zheng, Shourong; Gu, Cheng; Zhu, Dongqiang; Alvarez, Pedro J J

    2016-01-19

    A large effort is being made to develop nanosorbents with tunable surface chemistry for enhanced adsorption affinity and selectivity toward target organic contaminants. Heteroatom N-doped multiwall carbon nanotubes (N-MCNT) were synthesized by chemical vapor deposition of pyridine and were further investigated for the adsorptive removal of several aromatic chemicals varying in electronic donor and acceptor ability from aqueous solutions using a batch technique. Compared with commercial nondoped multiwall carbon nanotubes (MCNT), N-MCNT had similar specific surface area, morphology, and pore-size distribution but more hydrophilic surfaces and more surface defects due to the doping of graphitic and pyridinic N atoms. N-MCNT exhibited enhanced adsorption (2-10 folds) for the π-donor chemicals (2-naphthol and 1-naphthalmine) at pH ∼6 but similar adsorption for the weak π-donor chemical (naphthalene) and even lower adsorption (up to a 2-fold change) for the π-acceptor chemical (1,3-dinitrobenzene). The enhanced adsorption of 2-naphthol and 1-naphthalmine to N-MCNT was mainly attributed to the favored π-π electron-donor-acceptor (EDA) interaction between the π-donor adsorbate molecule and the polarized N-heterocyclic aromatic ring (π-acceptor) on N-MCNT. The proposed adsorption enhancement mechanisms were further tested through the pH effects on adsorption and the density function theory (DFT) calculation. The results show for the first time that the adsorptive interaction of π-donor aromatic compounds with carbon nanomaterials can be facilitated by N-doping. PMID:26669961

  17. First Principles Calculations of Oxygen Adsorption on the UN(001) Surface

    SciTech Connect

    Zhukovskii, Yuri F.; Bocharov, Dmitry; Kotomin, Eugene Alexej; Evarestov, Robert; Bandura, A. V.

    2009-01-01

    Fabrication, handling and disposal of nuclear fuel materials require comprehensive knowledge of their surface morphology and reactivity. Due to unavoidable contact with air components (even at low partial pressures), UN samples contain considerable amount of oxygen impurities affecting fuel properties. In this study we focus on reactivity of the energetically most stable (001) substrate of uranium nitride towards the atomic oxygen as one of initial stages for further UN oxidation. The basic properties of O atoms adsorbed on the UN(001) surface are simulated here combining the two first principles calculation methods based on the plane wave basis set and that of the localized orbitals.

  18. Preparation of hybrid organic-inorganic mesoporous silicas applied to mercury removal from aqueous media: Influence of the synthesis route on adsorption capacity and efficiency.

    PubMed

    Pérez-Quintanilla, Damián; Sánchez, Alfredo; Sierra, Isabel

    2016-06-15

    New hybrid organic-inorganic mesoporous silicas were prepared by employing three different synthesis routes and mercury adsorption studies were done in aqueous media using the batch technique. The organic ligands employed for the functionalization were derivatives of 2-mercaptopyrimidine or 2-mercaptothiazoline, and the synthesis pathways used were post-synthesis, post-synthesis with surface ion-imprinting and co-condensation with ion-imprinting. The incorporation of functional groups and the presence of ordered mesopores in the organosilicas was confirmed by XRD, TEM and SEM, nitrogen adsorption-desorption isotherms, (13)C MAS-NMR, (29)Si MAS-NMR, elemental and thermogravimetric analysis. The highest adsorption capacity and selectivity observed was for the material functionalized with 2-mercaptothiazoline ligand by means the co-condensation with ion-imprinting route (1.03mmolg(-1) at pH 6). The prepared material could be potential sorbent for the extraction of this heavy metal from environmental and drinking waters. PMID:27023632

  19. Adsorption of CO2, N2, and CH4 in Cs-exchanged chabazite: A combination of van der Waals density functional theory calculations and experiment study

    NASA Astrophysics Data System (ADS)

    Shang, Jin; Li, Gang; Singh, Ranjeet; Xiao, Penny; Danaci, David; Liu, Jefferson Z.; Webley, Paul A.

    2014-02-01

    The crucial role of dispersion force in correctly describing the adsorption of some typical small-size gas molecules (e.g., CO2, N2, and CH4) in ion-exchanged chabazites has been investigated at different levels of theory, including the standard density functional theory calculation using the Perdew, Burke, and Ernzerhof (PBE) exchange-correlation functional and van der Waals density functional theory (vdWDFT) calculations using different exchange-correlation models - vdW_DF2, optB86b, optB88, and optPBE. Our results show that the usage of different vdWDFT functionals does not significantly change the adsorption configuration or the profile of static charge rearrangement of the gas-chabazite complexes, in comparison with the results obtained using the PBE. The calculated values of adsorption enthalpy using different functionals are compared with our experimental results. We conclude that the incorporation of dispersion interaction is imperative to correctly predict the trend of adsorption enthalpy values, in terms of different gas molecules and Cs+ cation densities in the adsorbents, even though the absolute values of adsorption enthalpy are overestimated by approximate 10 kJ/mol compared with experiments.

  20. Ab initio calculations for dissociative hydrogen adsorption on lithium oxide surfaces

    SciTech Connect

    Sutjianto, A. |; Tam, S.W.; Curtiss, L.A.; Johnson, C.E.; Pandey, R.

    1994-12-01

    Lithium ceramics are one class of materials being considered as tritium breeders for fusion technology,and hydrogen is known to enhance the release of tritium from lithium ceramic materials. Dissociative hydrogen chemisorption on the Li{sub 2}O surfaces of the (100), (110), and (111) planes has been investigated with ab initio Hartree-Fock calculations. Calculations for unrelaxed crystal Li{sub 2}O structures indicated that except for the (100) surface, the (110) and (111) surfaces are stable. Results on the heterolytic sites of n-layer (110) (where n {ge} 2) slabs and three-layer (111) slabs suggest that dissociative hydrogen chemisorption is endothermic. For a one-layer (110) slab at 100% surface coverage, the dissociative hydrogen chemisorption is exothermic, forming OH{sup {minus}} and Li{sup +}H{sup {minus}}Li{sup +}. The results also indicate that the low coordination environment in surface step structures, such as kinks and ledges, may plan an important role in the hydrogen chemisorption process. On the homolytic sites of the (110) and (111) surfaces, there is no hydrogen chemisorption.

  1. Changing the adsorption capacity of coal-based honeycomb monoliths for pollutant removal from liquid streams by controlling their porosity

    NASA Astrophysics Data System (ADS)

    Gatica, José M.; Harti, Sanae; Vidal, Hilario

    2010-09-01

    Coal-based honeycomb monoliths extruded using methods developed for ceramic materials have been used to retain methylene blue and p-nitrophenol from aqueous solutions. The influence of the filters' thermal treatment on their textural properties and performance as adsorbents was examined. Characterization by N 2 physisorption, mercury porosimetry and scanning electron microscopy along with adsorption tests under dynamic conditions suggest that, depending on the pollutant and its initial concentration, it can be more convenient to previously submit the monoliths to a simple carbonization or to an additional activation, with or without preoxidation, as a consequence of their different resulting pore structures. Infrared spectroscopy indicates that their different adsorption behaviour seems not to be related to differences in their surface chemical groups. In addition, axial crushing tests show that the monoliths have an acceptable mechanical resistance for the application investigated.

  2. Adsorption of metal-phthalocyanine molecules onto the Si(111) surface passivated by δ doping: Ab initio calculations

    NASA Astrophysics Data System (ADS)

    Veiga, R. G. A.; Miwa, R. H.; McLean, A. B.

    2016-03-01

    We report first-principles calculations of the energetic stability and electronic properties of metal-phthalocyanine (MPc) molecules (M = Cr, Mn, Fe, Co, Ni, Cu, and Zn) adsorbed on the δ -doped Si(111)-B (√{3 }×√{3 }) reconstructed surface. (i) It can be seen that CrPc, MnPc, FePc, and CoPc are chemically anchored to the topmost Si atom. (ii) Contrastingly, the binding of the NiPc, CuPc, and ZnPc molecules to the Si (111 ) -B (√{3 }×√{3 }) surface is exclusively ruled by van der Waals interactions, the main implication being that these molecules may diffuse and rearrange to form clusters and/or self-organized structures on this surface. The electronic structure calculations reveal that in point (i), owing to the formation of the metal-Si covalent bond, the net magnetic moment of the molecule is quenched by 1 μB , remaining unchanged in point (ii). In particular, the magnetic moment of CuPc (1 μB ) is preserved after adsorption. Finally, we verify that the formation of ZnPc, CuPc, and NiPc molecular (self-assembled) arrangements on the Si(111)-B (√{3 }×√{3 } ) surface is energetically favorable, in good agreement with recent experimental findings.

  3. Hydrogen adsorption capacities of multi-walled boron nitride nanotubes and nanotube arrays: a grand canonical Monte Carlo study.

    PubMed

    Ahadi, Zohreh; Shadman, Muhammad; Yeganegi, Saeed; Asgari, Farid

    2012-07-01

    Hydrogen adsorption in multi-walled boron nitride nanotubes and their arrays was studied using grand canonical Monte Carlo simulation. The results show that hydrogen storage increases with tube diameter and the distance between the tubes in multi-walled boron nitride nanotube arrays. Also, triple-walled boron nitride nanotubes present the lowest level of hydrogen physisorption, double-walled boron nitride nanotubes adsorb hydrogen better when the diameter of the inner tube diameter is sufficiently large, and single-walled boron nitride nanotubes adsorb hydrogen well when the tube diameter is small enough. Boron nitride nanotube arrays adsorb hydrogen, but the percentage of adsorbed hydrogen (by weight) in boron nitride nanotube arrays is rather similar to that found in multi-walled boron nitride nanotubes. Also, when the Langmuir and Langmuir-Freundlich equations were fitted to the simulated data, it was found that multi-layer adsorptivity occurs more prominently as the number of walls and the tube diameter increase. However, in single-walled boron nitride nanotubes with a small diameter, the dominant mechanism is monolayer adsorptivity. PMID:22160758

  4. CTAB-assisted synthesis of mesoporous F-N-codoped TiO{sub 2} powders with high visible-light-driven catalytic activity and adsorption capacity

    SciTech Connect

    Xie Yi Zhao Xiujian Li Yuanzhi; Zhao Qingnan; Zhou Xuedong; Yuan Qihua

    2008-08-15

    This article describes the preparation of mesoporous rod-like F-N-codoped TiO{sub 2} powder photocatalysts with anatase phase via a sol-gel route at the temperature of 373 K, using cetyltrimethyl ammonium bromide (CTAB) as surfactant. The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectra (UV-vis DRS). The results showed that the photocatalysts possessed a homogeneous pore diameter and a high surface area of 106.3-160.7 m{sup 3} g{sup -1}. The increasing CTAB reactive concentration extended the visible-light absorption up to 600 nm. The F-N-codoped TiO{sub 2} powders exhibited significant higher adsorption capacity for methyl orange (MO) than that of Degussa P25 and showed more than 6 times higher visible-light-induced catalytic degradation for MO than that of P25. - Graphical abstract: The introduction of surfactant CTAB not only extended the visible light absorption of mesoporous F-N-codoped TiO{sub 2} up to 600 nm but also significantly enhanced the adsorption capacity and visible-light-induced degradation for methyl orange. Mesoporous rod-like F-N-codoped TiO{sub 2} powder photocatalysts were synthesized via a sol-gel route at low temperature of 373 K.

  5. Strong and weak adsorption of CO2 on PuO2 (1 1 0) surfaces from first principles calculations

    NASA Astrophysics Data System (ADS)

    Yu, H. L.; Deng, X. D.; Li, G.; Lai, X. C.; Meng, D. Q.

    2014-10-01

    The CO2 adsorption on plutonium dioxide (PuO2) (1 1 0) surface was studied using projector-augmented wave (PAW) method based on density-functional theory corrected for onsite Coulombic interactions (GGA + U). It is found that CO2 has several different adsorption features on PuO2 (1 1 0) surface. Both weak and strong adsorptions exist between CO2 and the PuO2 (1 1 0) surface. Further investigation of partial density of states (PDOS) and charge density difference on two typical absorption sites reveal that electrostatic interactions were involved in the weak interactions, while covalent bonding was developed in the strong adsorptions.

  6. Investigation on NOx adsorption in [M‧]-MAPO-5 (M = Si, Ti; M‧ = Ag, Cu) by density functional theory calculation

    NASA Astrophysics Data System (ADS)

    Liu, Jiexiang; Zhang, Xiaoguang

    2013-01-01

    NO, N2O and NO2 adsorption in [M‧]-MAPO-5 (M = Si, Ti; M‧ = Ag, Cu) models of the modified aluminophosphate molecular sieves was investigated by density functional theory (DFT) method. The equilibrium structural parameters and adsorption energies were obtained and compared. The structural parameters of NO and NO2 in the adsorbed state had a distinct change than that of N2O compared to their free gas state. [M‧]-MAPO-5 was more effective for the activation of NOx molecule compared to [M‧]-AlMOR (M‧ = Ag, Cu) models of the modified mordenite in our previous studies. The adsorption energies data indicated that adsorption strength of NOx followed the decreasing order of NO2 > NO > N2O. And adsorption complexes in η1-N mode were much stabler than that in η1-O mode, which was similar to that in [M‧]-AlMOR. [Cu]-MAPO-5 had a much stronger adsorption for NOx than [Ag]-MAPO-5. And [M‧]-SiMOR had a little stronger adsorption for NOx than [M‧]-TiMOR. Furthermore, the resistance capabilities of [M‧]-MAPO-5 to SO2, H2O and O2 were studied and analyzed. The interaction mechanism of NOx adsorption in [M‧]-MAPO-5 was also discussed by natural bond orbital (NBO) analysis, which was in reasonable agreement with the adsorption interaction strengths.

  7. New V(IV)-based metal-organic framework having framework flexibility and high CO2 adsorption capacity.

    PubMed

    Liu, Ying-Ya; Couck, Sarah; Vandichel, Matthias; Grzywa, Maciej; Leus, Karen; Biswas, Shyam; Volkmer, Dirk; Gascon, Jorge; Kapteijn, Freek; Denayer, Joeri F M; Waroquier, Michel; Van Speybroeck, Veronique; Van Der Voort, Pascal

    2013-01-01

    A vanadium based metal-organic framework (MOF), VO(BPDC) (BPDC(2-) = biphenyl-4,4'-dicarboxylate), adopting an expanded MIL-47 structure type, has been synthesized via solvothermal and microwave methods. Its structural and gas/vapor sorption properties have been studied. This compound displays a distinct breathing effect toward certain adsorptives at workable temperatures. The sorption isotherms of CO(2) and CH(4) indicate a different sorption behavior at specific temperatures. In situ synchrotron X-ray powder diffraction measurements and molecular simulations have been utilized to characterize the structural transition. The experimental measurements clearly suggest the existence of both narrow pore and large pore forms. A free energy profile along the pore angle was computationally determined for the empty host framework. Apart from a regular large pore and a regular narrow pore form, an overstretched narrow pore form has also been found. Additionally, a variety of spectroscopic techniques combined with N(2) adsorption/desorption isotherms measured at 77 K demonstrate that the existence of the mixed oxidation states V(III)/V(IV) in the titled MOF structure compared to pure V(IV) increases the difficulty in triggering the flexibility of the framework. PMID:23256823

  8. Polyamine-Cladded 18-Ring-Channel Gallium Phosphites with High-Capacity Hydrogen Adsorption and Carbon Dioxide Capture.

    PubMed

    Sie, Ming-Jhe; Lin, Chia-Her; Wang, Sue-Lein

    2016-06-01

    In this study, we synthesized a unique inorganic framework bearing the largest 18-membered-ring channels in gallium phosphites, denoted as NTHU-15, which displayed genuine porosity even though large organic templates were present. The idea of using the "template-cladded" strategy succeeded in releasing channel space of up to ∼24% of the unit-cell volume as highly positive-charged organic templates were manipulated to cling to the anionic inorganic walls. NTHU-15 showed both high H2 uptake of 3.8 mmol/g at 77 K and effective CO2 adsorption of ∼2.4 mmol/g at 298 K, which surpassed those of all other known extra-large-channel inorganic framework structures. NTHU-15 has been successful at overcoming the long-standing problem of organic-templated extra-large-channel structures as opposed to a "true open" framework. Moreover, it realized practical gas sorption functionality in innovated metal phosphites. In view of its high stability in hot water and high selectivity for CO2 adsorption, NTHU-15 may be the first novel inorganic framework material to be applied to the field of flue gas cleaning. PMID:27181272

  9. Effect of cetyl trimethyl ammonium bromide concentration on structure, morphology and carbon dioxide adsorption capacity of calcium hydroxide based sorbents

    NASA Astrophysics Data System (ADS)

    Hlaing, Nwe Ni; Vignesh, K.; Sreekantan, Srimala; Pung, Swee-Yong; Hinode, Hirofumi; Kurniawan, Winarto; Othman, Radzali; Thant, Aye Aye; Mohamed, Abdul Rahman; Salim, Chris

    2016-02-01

    Calcium hydroxide (Ca(OH)2) has been proposed as an important material for industrial, architectural, and environmental applications. In this study, calcium acetate was used as a precursor and cetyl trimethyl ammonium bromide (CTAB) was used as a surfactant to synthesize Ca(OH)2 based adsorbents for carbon dioxide (CO2) capture. The effect of CTAB concentration (0.2-0.8 M) on the structure, morphology and CO2 adsorption performance of Ca(OH)2 was studied in detail. The synthesized samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), BET surfaced area and thermogravimetry-differential thermal analysis (TG-DTA) techniques. The phase purity, crystallite size, Brunauer-Emmett-Teller (BET) surface area and CO2 adsorption performance of Ca(OH)2 precursor adsorbents were significantly increased when the concentration of CTAB was increased. XRD results showed that pure Ca(OH)2 phase was obtained at the CTAB concentration of 0.8 M. TGA results exhibited that 0.8 M of CTAB-assisted Ca(OH)2 precursor adsorbent possessed a residual carbonation conversion of ∼56% after 10 cycles.

  10. Rb+ adsorption at the quartz(101)-aqueous interface: comparison of resonant anomalous x-ray reflectivity with ab initio calculations

    DOE PAGESBeta

    Bellucci, Francesco; Lee, Sang Soo; Kubicki, James D.; Bandura, Andrei V.; Zhang, Zhan; Wesolowski, David J.; Fenter, Paul

    2015-01-29

    We study adsorption of Rb+ to the quartz(101)–aqueous interface at room temperature with specular X-ray reflectivity, resonant anomalous X-ray reflectivity, and density functional theory. The interfacial water structures observed in deionized water and 10 mM RbCl solution at pH 9.8 were similar, having a first water layer at height of 1.7 ± 0.1 Å above the quartz surface and a second layer at 4.8 ± 0.1 Å and 3.9 ± 0.8 Å for the water and RbCl solutions, respectively. The adsorbed Rb+ distribution is broad and consists of presumed inner-sphere (IS) and outer-sphere (OS) complexes at heights of 1.8 ±more » 0.1 and 6.4 ± 1.0 Å, respectively. Projector-augmented planewave density functional theory (DFT) calculations of potential configurations for neutral and negatively charged quartz(101) surfaces at pH 7 and 12, respectively, reveal a water structure in agreement with experimental results. These DFT calculations also show differences in adsorbed speciation of Rb+ between these two conditions. At pH 7, the lowest energy structure shows that Rb+ adsorbs dominantly as an IS complex, whereas at pH 12 IS and OS complexes have equivalent energies. The DFT results at pH 12 are generally consistent with the two site Rb distribution observed from the X-ray data at pH 9.8, albeit with some differences that are discussed. In conclusion, surface charge estimated on the basis of the measured total Rb+ coverage was -0.11 C/m2, in good agreement with the range of the surface charge magnitudes reported in the literature.« less

  11. First-principles calculations of NO and NO2 adsorption on a spinel ZnGaAlO4(100) surface

    NASA Astrophysics Data System (ADS)

    Xiang, Chao; Tan, Honglin; Lu, Jiansheng; Yu, Lan; Song, Peng; Zeng, Chunhua; Zhang, Defeng; Tao, Shigang

    2014-07-01

    Density functional theory (DFT) has been used to investigate the properties of NO and NO2 adsorption on a ZnGaAlO4(100) surface. The calculation results show that the minimum surface energy is 2.3073 J m-2. The configuration of NO adsorbed on the surface is more stable through an N-down orientation due to the strong hybridization between d states and the NO-π orbital. In particular, NO approaches Zn via its N side with an adsorption energy of -23.50 kcal mol-1, while the comparable value is -44.19 kcal mol-1 for NO2 adsorbed at Zn, suggesting a higher degree of adsorption stability. In addition, substitution of Al with Ga is responsible for the most stable mode of NO2 adsorption with a binding energy of -53.40 kcal mol-1. This demonstrates that the process of desorption of NO2 is thermodynamically feasible. NO2 adsorbed on the surface is activated, showing that the adsorption can directly lead to a dissociation of NO2. Moreover, the process of dissociation of NO2 adsorbed at Ga is favored due to a lower energy barrier of activation.

  12. 75 FR 43059 - Mandatory Reliability Standards for the Calculation of Available Transfer Capability, Capacity...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-23

    ... Protocol for Public Utilities, Order No. 676-E, 74 FR 63288 (Dec. 3, 2009), FERC Stats. & Regs. ] 31,299... Energy Regulatory Commission 18 CFR Parts 38 and 40 Mandatory Reliability Standards for the Calculation...-003, Mandatory Reliability Standards for the Calculation of Available Transfer Capability,...

  13. Calculation of the standard heat capacity at constant pressure for cobalt ferrite-zinc ferrite solid solutions

    SciTech Connect

    Chachanidze, G.D.; Pavlenishvili, T.A.; Machaladze, T.E.; Khutsishvili, D.I.

    1994-08-01

    Magnetic, electrical, and other properties of Co{sub 1-x}Zn{sub x}Fe{sub 2}O{sub 4} solid solutions are widely studied because of their high coercive force and Curie temperature ({Tc}), which makes these compounds applicable in modern electronic devices. However, the information published on their thermodynamic properties is limited. This paper focuses on calculation of the standard heat capacity C{sub p}{sup 0} (298 K) for cobalt zinc ferrites using correlation analysis of the relationship between C{sub p}{sup 0} (298 K) and the saturation magnetic moment {mu}{sub o}. The authors studied the solid solutions Co{sub 1-x}Zn{sub x}Fe{sub 2}O{sub 4} (x = 0.2, 0.4, 0.5, 0.6, and 0.8), whose magnetic and thermal parameters, crucial in our calculations, are known to be strongly dependent on the preparation conditions. An equation was derived for calculation of the standard heat capacity at constant pressure from the saturation magnetic moment of Co{sub 1-x}Zn{sub x}Fe{sub 2}O{sub 4} solid solutions. The equation allows a satisfactory estimation of the standard heat capacity at 298 Kelvin for any cobalt ferrite-zinc ferrite solid, providing the saturation magnetic moment is available.

  14. Modification of ASM3 for the determination of biomass adsorption/storage capacity in bulking sludge control.

    PubMed

    Makinia, J; Rosenwinkel, K H; Phan, L C

    2006-01-01

    The selector activated sludge (SAS) systems are known to prevent excessive growth of filamentous microorganisms responsible for bulking sludge, but these systems were hardly ever modelled. This study aimed to develop a model capable of predicting rapid substrate removal in the SAS systems. For this purpose, the Activated Sludge Model No. 3 (ASM3) was extended with three processes (adsorption, direct growth on the adsorbed substrate under aerobic or anoxic conditions). The modified ASM3 was tested against the results of batch experiments with the biomass originating from two full-scale SAS systems in Germany. The endogenous biomass was mixed with various readily biodegradable substrates (acetate, peptone, glucose and wastewater) and the utilisation of substrate (expresses as COD) and oxygen uptake rates (OURs) were measured during the experiments. In general, model predictions fitted to the experimental data, but a considerable number of kinetic (5) and stoichiometric (2) parameters needed to be adjusted during model calibration. The simulation results revealed that storage was generally a dominating process compared to direct growth in terms of the adsorbed substrate utilisation. The contribution of storage ranged from 65-71% (Plant A) and 69-92% (Plant B). PMID:16605021

  15. STM imagery and density functional calculations of C60 fullerene adsorption on the 6H-SiC(0001)-3×3 surface

    NASA Astrophysics Data System (ADS)

    Ovramenko, T.; Spillebout, F.; Bocquet, F. C.; Mayne, A. J.; Dujardin, G.; Sonnet, Ph.; Stauffer, L.; Ksari, Y.; Themlin, J.-M.

    2013-04-01

    Scanning tunneling microscopy (STM) studies of the fullerene C60 molecule adsorbed on the silicon carbide SiC(0001)-3×3 surface, combined with density functional theory (DFT) calculations, show that chemisorption of individual C60 molecules occurs through the formation of one bond to one silicon adatom only in contrast to multiple bond formation on other semiconducting surfaces. We observe three stable adsorption sites with respect to the Si adatoms of the surface unit cell. Comprehensive DFT calculations give different adsorption energies for the three most abundant sites showing that van der Waals forces between the C60 molecule and the neighboring surface atoms need to be considered. The C60 molecules are observed to form small clusters even at low coverage indicating the presence of a mobile molecular precursor state and nonnegligible intermolecular interactions.

  16. Synthesis of fungus-like MoS2 nanosheets with ultrafast adsorption capacities toward organic dyes

    NASA Astrophysics Data System (ADS)

    Song, HaoJie; You, Shengsheng; Jia, XiaoHua

    2015-11-01

    Fungus-like molybdenum disulfide (MoS2) nanosheets with a thickness of a few nanometers have been successfully synthesized via one-pot hydrothermal method. The as-prepared MoS2 nanosheets with a high surface area of 106.989 m2 g-1 exhibited excellent wastewater treatment performance with high removal capacities toward organic dyes. In addition, the fungus-like MoS2 nanosheets can absorb Congo red completely within 2 min. Successful access to high quality fungus-like MoS2 nanosheets will make it possible for their potential application in catalysis and other fields.

  17. Improved methods for Feynman path integral calculations and their application to calculate converged vibrational–rotational partition functions, free energies, enthalpies, entropies, and heat capacities for methane

    SciTech Connect

    Mielke, Steven L. E-mail: truhlar@umn.edu; Truhlar, Donald G. E-mail: truhlar@umn.edu

    2015-01-28

    We present an improved version of our “path-by-path” enhanced same path extrapolation scheme for Feynman path integral (FPI) calculations that permits rapid convergence with discretization errors ranging from O(P{sup −6}) to O(P{sup −12}), where P is the number of path discretization points. We also present two extensions of our importance sampling and stratified sampling schemes for calculating vibrational–rotational partition functions by the FPI method. The first is the use of importance functions for dihedral angles between sets of generalized Jacobi coordinate vectors. The second is an extension of our stratification scheme to allow some strata to be defined based only on coordinate information while other strata are defined based on both the geometry and the energy of the centroid of the Feynman path. These enhanced methods are applied to calculate converged partition functions by FPI methods, and these results are compared to ones obtained earlier by vibrational configuration interaction (VCI) calculations, both calculations being for the Jordan–Gilbert potential energy surface. The earlier VCI calculations are found to agree well (within ∼1.5%) with the new benchmarks. The FPI partition functions presented here are estimated to be converged to within a 2σ statistical uncertainty of between 0.04% and 0.07% for the given potential energy surface for temperatures in the range 300–3000 K and are the most accurately converged partition functions for a given potential energy surface for any molecule with five or more atoms. We also tabulate free energies, enthalpies, entropies, and heat capacities.

  18. Improved methods for Feynman path integral calculations and their application to calculate converged vibrational-rotational partition functions, free energies, enthalpies, entropies, and heat capacities for methane

    NASA Astrophysics Data System (ADS)

    Mielke, Steven L.; Truhlar, Donald G.

    2015-01-01

    We present an improved version of our "path-by-path" enhanced same path extrapolation scheme for Feynman path integral (FPI) calculations that permits rapid convergence with discretization errors ranging from O(P-6) to O(P-12), where P is the number of path discretization points. We also present two extensions of our importance sampling and stratified sampling schemes for calculating vibrational-rotational partition functions by the FPI method. The first is the use of importance functions for dihedral angles between sets of generalized Jacobi coordinate vectors. The second is an extension of our stratification scheme to allow some strata to be defined based only on coordinate information while other strata are defined based on both the geometry and the energy of the centroid of the Feynman path. These enhanced methods are applied to calculate converged partition functions by FPI methods, and these results are compared to ones obtained earlier by vibrational configuration interaction (VCI) calculations, both calculations being for the Jordan-Gilbert potential energy surface. The earlier VCI calculations are found to agree well (within ˜1.5%) with the new benchmarks. The FPI partition functions presented here are estimated to be converged to within a 2σ statistical uncertainty of between 0.04% and 0.07% for the given potential energy surface for temperatures in the range 300-3000 K and are the most accurately converged partition functions for a given potential energy surface for any molecule with five or more atoms. We also tabulate free energies, enthalpies, entropies, and heat capacities.

  19. Adsorption of hydrogen on boron-doped graphene: A first-principles prediction

    SciTech Connect

    Zhou, Yungang; Zu, Xiaotao T.; Gao, Fei; Nie, JL; Xiao, H. Y.

    2009-01-01

    The doping effects of boron on the atomic adsorption of hydrogen on graphene have been investigated using density functional theory calculations. The hydrogen adsorption energies and electronic structures have been considered for pristine and B-doped graphene with the adsorption of hydrogen on top of carbon or boron atom. It is found that the B-doping forms an electron-deficient structure, and decreases the hydrogen adsorption energy dramatically. For the adsorption of hydrogen on top of other sites, similar results also have been found. These results indicate that the hydrogen storage capacity is improved by the doping of B atom.

  20. Calculation of the acid-base equilibrium constants at the alumina/electrolyte interface from the ph dependence of the adsorption of singly charged ions (Na+, Cl-)

    NASA Astrophysics Data System (ADS)

    Gololobova, E. G.; Gorichev, I. G.; Lainer, Yu. A.; Skvortsova, I. V.

    2011-05-01

    A procedure was proposed for the calculation of the acid-base equilibrium constants at an alumina/electrolyte interface from experimental data on the adsorption of singly charged ions (Na+, Cl-) at various pH values. The calculated constants (p K {1/0}= 4.1, p K {2/0}= 11.9, p K {3/0}= 8.3, and p K {4/0}= 7.7) are shown to agree with the values obtained from an experimental pH dependence of the electrokinetic potential and the results of potentiometric titration of Al2O3 suspensions.

  1. Heat Capacity Uncertainty Calculation for the Eutectic Mixture of Biphenyl/Diphenyl Ether Used as Heat Transfer Fluid: Preprint

    SciTech Connect

    Gomez, J. C.; Glatzmaier, G. C.; Mehos, M.

    2012-09-01

    The main objective of this study was to calculate the uncertainty at 95% confidence for the experimental values of heat capacity of the eutectic mixture of biphenyl/diphenyl ether (Therminol VP-1) determined from 300 to 370 degrees C. Twenty-five samples were evaluated using differential scanning calorimetry (DSC) to obtain the sample heat flow as a function of temperature. The ASTM E-1269-05 standard was used to determine the heat capacity using DSC evaluations. High-pressure crucibles were employed to contain the sample in the liquid state without vaporizing. Sample handling has a significant impact on the random uncertainty. It was determined that the fluid is difficult to handle, and a high variability of the data was produced. The heat capacity of Therminol VP-1 between 300 and 370 degrees C was measured to be equal to 0.0025T+0.8672 with an uncertainty of +/- 0.074 J/g.K (3.09%) at 95% confidence with T (temperature) in Kelvin.

  2. Adsorption of sulfur dioxide on ammonia-treated activated carbon fibers

    USGS Publications Warehouse

    Mangun, C.L.; DeBarr, J.A.; Economy, J.

    2001-01-01

    A series of activated carbon fibers (ACFs) and ammonia-treated ACFs prepared from phenolic fiber precursors have been studied to elucidate the role of pore size, pore volume, and pore surface chemistry on adsorption of sulfur dioxide and its catalytic conversion to sulfuric acid. As expected, the incorporation of basic functional groups into the ACFs was shown as an effective method for increasing adsorption of sulfur dioxide. The adsorption capacity for dry SO2 did not follow specific trends; however the adsorption energies calculated from the DR equation were found to increase linearly with nitrogen content for each series of ACFs. Much higher adsorption capacities were achieved for SO2 in the presence of oxygen and water due to its catalytic conversion to H2SO4. The dominant factor for increasing adsorption of SO2 from simulated flue gas for each series of fibers studied was the weight percent of basic nitrogen groups present. In addition, the adsorption energies calculated for dry SO2 were shown to be linearly related to the adsorption capacity of H2SO4 from this flue gas for all fibers. It was shown that optimization of this parameter along with the pore volume results in higher adsorption capacities for removal of SO2 from flue gases. ?? 2001 Elsevier Science Ltd. All rights reserved.

  3. Calculation of protein heat capacity from replica-exchange molecular dynamics simulations with different implicit solvent models.

    PubMed

    Yeh, In-Chul; Lee, Michael S; Olson, Mark A

    2008-11-27

    The heat capacity has played a major role in relating microscopic and macroscopic properties of proteins and their disorder-order phase transition of folding. Its calculation by atomistic simulation methods remains a significant challenge due to the complex and dynamic nature of protein structures, their solvent environment, and configurational averaging. To better understand these factors on calculating a protein heat capacity, we provide a comparative analysis of simulation models that differ in their implicit solvent description and force-field resolution. Our model protein system is the src Homology 3 (SH3) domain of alpha-spectrin, and we report a series of 10 ns replica-exchange molecular dynamics simulations performed at temperatures ranging from 298 to 550 K, starting from the SH3 native structure. We apply the all-atom CHARMM22 force field with different modified analytical generalized Born solvent models (GBSW and GBMV2) and compare these simulation models with the distance-dependent dielectric screening of charge-charge interactions. A further comparison is provided with the united-atom CHARMM19 plus a pairwise GB model. Unfolding-folding transition temperatures of SH3 were estimated from the temperature-dependent profiles of the heat capacity, root-mean-square distance from the native structure, and the fraction of native contacts, each calculated from the density of states by using the weighted histogram analysis method. We observed that, for CHARMM22, the unfolding transition and energy probability density were quite sensitive to the implicit solvent description, in particular, the treatment of the protein-solvent dielectric boundary in GB models and their surface-area-based hydrophobic term. Among the solvent models tested, the calculated melting temperature varied in the range 353-438 K and was higher than the experimental value near 340 K. A reformulated GBMV2 model of employing a smoother molecular-volume dielectric interface was the most accurate

  4. Efficient Cadmium Bioaccumulation by Displayed Hybrid CS3 Pili: Effect of Heavy Metal Binding Motif Insertion Site on Adsorption Capacity and Selectivity.

    PubMed

    Eskandari, Vajiheh; Yakhchali, Bagher; Sadeghi, Mehdi; Karkhane, Ali Asghar; Ahmadi-Danesh, Houra

    2015-12-01

    The objective of this study was to evaluate the influence of insertion site of the metal binding motif on the bioaccumulation capacity of the hybrid CS3 pili displayed on the surface of Escherichia coli using both computational and experimental methods. Two metal binding motifs (cadmium binding motif (cbm) and cadmium binding beta motif (cbβm)), identified by searching against the PROSITE database, were inserted into five putative permissive sites of CstH protein (CS3 pili subunit) by using SOEing PCR technique. The expression and surface display of the hybrid pili were evaluated using dot and Western blotting methods and also immunofluorescence microscopy. The cadmium binding affinity and selectivity of the recombinant bacteria displaying various hybrid pili were evaluated using atomic absorption procedure. The results showed that the cadmium binding motifs enabled the cells to sequester cadmium 8- to 16-fold higher than the E.coli expressing native pili. The location of the metal binding motifs in the pili subunit had also a significant effect on the metal-binding properties of the hybrid pili. The insertion at positions 107-108 and 92-93 of the mature CstH showed the highest adsorption in comparison to other positions. PMID:26438314

  5. Tuning the work function of VO2(1 0 0) surface by Ag adsorption and incorporation: Insights from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Chen, Lanli; Wang, Xiaofang; Shi, Siqi; Cui, Yuanyuan; Luo, Hongjie; Gao, Yanfeng

    2016-03-01

    VO2 is an attractive material for application to thermochromic optoelectronic devices such as smart windows, and Ag/VO2 double-layered structure can effectively decrease the phase transition temperature (Tc) of VO2 thin film, which is very important for practical application of VO2. Previous works has shown that the decrease in phase transition temperature (Tc) seems to be relevant with the work function of VO2 in Ag/VO2 double-layered thin film, although the underlying mechanism of tuning its Tc by Ag incorporation and adsorption on the VO2(1 0 0) surface has been rarely investigated. Our first-principles calculations reveal that the adsorption of Ag atoms on the VO2(1 0 0) surface rather than incorporation of Ag exhibits a lower work function, which is ascribed to an integrated effect of charge transfer from Ag to VO2(1 0 0) surface and enhanced surface dipole moment. The results suggest that the decrease in work function of VO2 with Ag adsorption favors the reduction in Tc. The current findings are helpful to understand the fundamental mechanism for yielding high-efficiency VO2-based optoelectronic devices.

  6. Comparisons between adsorption and diffusion of alkali, alkaline earth metal atoms on silicene and those on silicane: Insight from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Bo, Xu; Huan-Sheng, Lu; Bo, Liu; Gang, Liu; Mu-Sheng, Wu; Chuying, Ouyang

    2016-06-01

    The adsorption and diffusion behaviors of alkali and alkaline-earth metal atoms on silicane and silicene are both investigated by using a first-principles method within the frame of density functional theory. Silicane is staler against the metal adatoms than silicene. Hydrogenation makes the adsorption energies of various metal atoms considered in our calculations on silicane significantly lower than those on silicene. Similar diffusion energy barriers of alkali metal atoms on silicane and silicene could be observed. However, the diffusion energy barriers of alkali-earth metal atoms on silicane are essentially lower than those on silicene due to the small structural distortion and weak interaction between metal atoms and silicane substrate. Combining the adsorption energy with the diffusion energy barriers, it is found that the clustering would occur when depositing metal atoms on perfect hydrogenated silicene with relative high coverage. In order to avoid forming a metal cluster, we need to remove the hydrogen atoms from the silicane substrate to achieve the defective silicane. Our results are helpful for understanding the interaction between metal atoms and silicene-based two-dimensional materials. Project supported by the Natural Science Foundation of Jiangxi Province, China (Grant Nos. 20152ACB21014, 20151BAB202006, and 20142BAB212002) and the Fund from the Jiangxi Provincial Educational Committee, China (Grant No. GJJ14254). Bo Xu is also supported by the Oversea Returned Project from the Ministry of Education, China.

  7. H2 adsorption and dissociation on PdO(101) films supported on rutile TiO2 (110) facet: elucidating the support effect by DFT calculations.

    PubMed

    Sun, Xiongfei; Peng, Xing; Xu, Xianglan; Jin, Hua; Wang, Hongming; Wang, Xiang

    2016-09-01

    To explore metal oxide-support interactions and their effect, H2 adsorption and dissociation on PdO(101)/TiO2(110) films with different film thicknesses, in comparison with that on pure PdO(101) surface without TiO2(110) support, were studied by density functional theory calculation. A monolayer PdO(101) film supported on TiO2 facet shows different properties to a pure PdO(101) surface. On the monolayer PdO(101)/TiO2(110) film, TiO2 support leads to stronger molecular adsorption of H2 on coordinatively unsaturated Pd top sites than that on a pure PdO surface. H2 dissociation with the formation of OH was preferred thermodynamically but slightly unfavorable kinetically on the monolayer PdO film due to the TiO2 support effect. Graphical abstract On the monolayer PdO(101)/TiO2(110) film, the TiO2 support effect leads to stronger H2 molecular adsorption on coordinatively unsaturated Pd top sites than on pure PdO surface. H2 dissociation with the formation of OH is preferred thermodynamically but slightly unfavorable kinetically on the film due to the TiO2 support effect. PMID:27491853

  8. Method of local increments for the calculation of adsorption energies of atoms and small molecules on solid surfaces. 2. CO/MgO(001).

    PubMed

    Staemmler, Volker

    2011-06-30

    The method of local increments is used in connection with an embedded cluster approach and wave function based quantum chemical ab initio methods to describe the adsorption of a single CO molecule on the MgO(001) surface. The first step in this approach is a conventional Hartree-Fock calculation. The occupied orbitals are then localized by means of the Foster-Boys localization procedure, and the full system is decomposed into several "subunits" that consist of the orbitals localized at the CO molecule and at the Mg and O atoms of the MgO cluster. The correlation energy is expanded into a series of local n-body increments that are evaluated separately and independently. In this way, big savings in computer time can be achieved because (a) the treatment of a large system is replaced with a series of much faster calculations for small subsystems and (b) the big basis sets necessary for describing dispersion effects are only needed for the atoms in the respective subsystem while all other atoms can be treated by medium size Hartree-Fock type basis sets. The coupled electron pair approach, CEPA, an approximate coupled cluster method, is used to calculate the correlation energies of the various subsystems. For the vertical adsorption of CO on top a Mg atom of the MgO(001) surface with the C atom toward Mg, the individual one- and two-body increments are calculated as functions of the CO-MgO separation and a full potential energy curve is constructed from them. A very shallow minimum with an adsorption energy of 0.016 eV at a Mg-C distance of 3.04 Å is found at the Hartree-Fock level, while inclusion of correlation (dispersion) effects shortens the Mg-C distance to 2.59 Å and yields a much larger adsorption energy of 0.124 eV. This is in very good agreement with the best experimental value of 0.14 eV. The basis set superposition error, BSSE, was fully corrected for by the counterpoise method and the bonding mechanism was analyzed at the Hartree-Fock level by means of

  9. Rapid and accurate determination of total lung capacity (TLC) from routine chest radiograms using a programmable hand-held calculator.

    PubMed

    Rodgers, R P; Tannen, R

    1983-01-01

    Since its appearance in 1960, the method of Barnhard and associates for the determination of total lung capacity (TLC) from routine chest radiograms has been widely studied in normal and diseased subjects. The method appears to be as accurate as the current definitive procedure, total body plethysmography. The method is in routine use in major medical institutions where the procedure has been automated, but the method does not seem to have gained the wide use it deserves. This is likely due to the tedium of the technique when performed manually--a single determination can require 30 min. We present here an implementation of the Barnhard method for the HP41-C hand-held programmable calculator. In conjunction with the use of a transparent reticle used for obtaining the required measurements, the program allows a single measurement to be made in under 12 minutes. We hope this technique will make radiographic TLC measurements more broadly accessible to the medical profession. PMID:6872526

  10. Can carbon surface oxidation shift the pore size distribution curve calculated from Ar, N2 and CO2 adsorption isotherms? Simulation results for a realistic carbon model

    NASA Astrophysics Data System (ADS)

    Furmaniak, Sylwester; Terzyk, Artur P.; Gauden, Piotr A.; Harris, Peter J. F.; Kowalczyk, Piotr

    2009-08-01

    Using the virtual porous carbon model proposed by Harris et al, we study the effect of carbon surface oxidation on the pore size distribution (PSD) curve determined from simulated Ar, N2 and CO2 isotherms. It is assumed that surface oxidation is not destructive for the carbon skeleton, and that all pores are accessible for studied molecules (i.e., only the effect of the change of surface chemical composition is studied). The results obtained show two important things, i.e., oxidation of the carbon surface very slightly changes the absolute porosity (calculated from the geometric method of Bhattacharya and Gubbins (BG)); however, PSD curves calculated from simulated isotherms are to a greater or lesser extent affected by the presence of surface oxides. The most reliable results are obtained from Ar adsorption data. Not only is adsorption of this adsorbate practically independent from the presence of surface oxides, but, more importantly, for this molecule one can apply the slit-like model of pores as the first approach to recover the average pore diameter of a real carbon structure. For nitrogen, the effect of carbon surface chemical composition is observed due to the quadrupole moment of this molecule, and this effect shifts the PSD curves compared to Ar. The largest differences are seen for CO2, and it is clearly demonstrated that the PSD curves obtained from adsorption isotherms of this molecule contain artificial peaks and the average pore diameter is strongly influenced by the presence of electrostatic adsorbate-adsorbate as well as adsorbate-adsorbent interactions.

  11. Can carbon surface oxidation shift the pore size distribution curve calculated from Ar, N(2) and CO(2) adsorption isotherms? Simulation results for a realistic carbon model.

    PubMed

    Furmaniak, Sylwester; Terzyk, Artur P; Gauden, Piotr A; Harris, Peter J F; Kowalczyk, Piotr

    2009-08-01

    Using the virtual porous carbon model proposed by Harris et al, we study the effect of carbon surface oxidation on the pore size distribution (PSD) curve determined from simulated Ar, N(2) and CO(2) isotherms. It is assumed that surface oxidation is not destructive for the carbon skeleton, and that all pores are accessible for studied molecules (i.e., only the effect of the change of surface chemical composition is studied). The results obtained show two important things, i.e., oxidation of the carbon surface very slightly changes the absolute porosity (calculated from the geometric method of Bhattacharya and Gubbins (BG)); however, PSD curves calculated from simulated isotherms are to a greater or lesser extent affected by the presence of surface oxides. The most reliable results are obtained from Ar adsorption data. Not only is adsorption of this adsorbate practically independent from the presence of surface oxides, but, more importantly, for this molecule one can apply the slit-like model of pores as the first approach to recover the average pore diameter of a real carbon structure. For nitrogen, the effect of carbon surface chemical composition is observed due to the quadrupole moment of this molecule, and this effect shifts the PSD curves compared to Ar. The largest differences are seen for CO(2), and it is clearly demonstrated that the PSD curves obtained from adsorption isotherms of this molecule contain artificial peaks and the average pore diameter is strongly influenced by the presence of electrostatic adsorbate-adsorbate as well as adsorbate-adsorbent interactions. PMID:21828590

  12. Storage capacity and vibration frequencies of guest molecules in CH4 and CO2 hydrates by first-principles calculations.

    PubMed

    Cao, Xiaoxiao; Su, Yan; Liu, Yuan; Zhao, Jijun; Liu, Changling

    2014-01-01

    Using first-principle calculations at B97-D/6-311++G(2d,2p) level, we systematically explore the gas capacity of five standard water cavities (5(12), 4(3)5(6)6(3), 5(12)6(2), 5(12)6(4), and 5(12)6(8)) in clathrate hydrate and study the inclusion complexes to infer general trends in vibrational frequencies of guest molecules as a function of cage size and number of guest molecules. In addition, the Raman spectra of hydrates from CO2/CH4 gases are simulated. From our calculations, the maximum cage occupancy of the five considered cages (5(12), 4(3)5(6)6(3), 5(12)6(2), 5(12)6(4), and 5(12)6(8)) is one, one, two, three, and seven for both CH4 and CO2 guest molecules, respectively. Meanwhile, the optimum cage occupancy are one, one, one, two, and four for CO2 molecules and one, one, two, three, and five for CH4 molecules, respectively. Both the C-H stretching frequency of CH4 and the C-O stretching frequency of CO2 gradually decrease as size of the water cages increases. Meanwhile, the C-H stretching frequency gradually increases as the amount of CH4 molecules in the water cavity (e.g., 5(12)6(8)) increases. PMID:24320601

  13. Insights into the Mechanism of Fe(II) Adsorption and Oxidation at Fe-Clay Mineral Surfaces from First-Principles Calculations

    SciTech Connect

    Alexandrov, Vitali Y.; Rosso, Kevin M.

    2013-10-02

    Interfacial reactivity of redox-active iron-bearing mineral surfaces plays a crucial role in many environmental processes including biogeochemical cycling of various elements and contaminants. Herein, we apply density-functional-theory (DFT) calculations to provide atomistic insights into the heterogeneous reaction between aqueous Fe(II) and the Fe-bearing clay mineral nontronite Fe2Si4O10(OH)2 by studying its adsorption mechanism and interfacial Fe(II)-Fe(III) electron transfer (ET) at edge and basal surfaces. We find that edge-bound Fe(II) adsorption complexes at different surface sites (ferrinol, silanol and mixed) may coexist on both (010) and (110) edge facets, with complexes at ferrinol FeO(H) sites being the most energetically favorable and coupled to proton transfer. Calculation of the ET activation energy suggests that interfacial ET into dioctahedral Fe(III) sheets is probable at the clay edges and occurs predominantly but not exclusively through the complexes adsorbed at ferrinol sites and might also involve mixed sites. No clear evidence is found for complexes on basal surface that are compatible with ET through the basal sheet despite this experimentally hypothesized ET interface. This study suggests a strong pH-dependence of Fe(II) surface complexation at basal versus edge facets and highlights the importance of the protonation state of bridging ligands and proton coupled electron transfer to facilitate ET into Fe-rich clay minerals.

  14. Adsorption and isothermal models of atrazine by zeolite prepared from Egyptian kaolin

    NASA Astrophysics Data System (ADS)

    Jamil, Tarek S.; Gad-Allah, Tarek A.; Ibrahim, Hanan S.; Saleh, Tamer S.

    2011-01-01

    The adsorption behavior of Atrazine on zeolites, prepared from Egyptian kaolin, has been studied in order to consider the application of these types of zeolites in water purification. The batch mode has been employed, using atrazine solution of concentration ranging from 2 to 10 mg /l. The adsorption capacity and distribution coefficients ( Kd) were determined for the adsorption system as a function of sorbate concentration. It was found that, under the studies concentrations, the percent of adsorbed atrazine on both zeolites match to Langmuir and Freundlich adsorption models. The constants of each model were calculated to assess the adsorption behavior of atrazine on each type of zeolite. According to the equilibrium studies, adsorption of atrazine on zeolite X at lower concentrations is much better than that on zeolite A. The application of Dublin-Kaganer-Radushkevich model revealed physisorption endothermic adsorption process for both zeolites. These results show that natural zeolites hold great potential to remove hazardous materials such as atrazine from water.

  15. Calculation of thermal conductivity, thermal diffusivity and specific heat capacity of sedimentary rocks using petrophysical well logs

    NASA Astrophysics Data System (ADS)

    Fuchs, Sven; Balling, Niels; Förster, Andrea

    2015-12-01

    In this study, equations are developed that predict for synthetic sedimentary rocks (clastics, carbonates and evapourates) thermal properties comprising thermal conductivity, specific heat capacity and thermal diffusivity. The rock groups are composed of mineral assemblages with variable contents of 15 major rock-forming minerals and porosities of 0-30 per cent. Petrophysical properties and their well-logging-tool-characteristic readings were assigned to these rock-forming minerals and to pore-filling fluids. Relationships are explored between each thermal property and other petrophysical properties (density, sonic interval transit time, hydrogen index, volume fraction of shale and photoelectric absorption index) using multivariate statistics. The application of these relations allows computing continuous borehole profiles for each rock thermal property. The uncertainties in the prediction of each property vary depending on the selected well-log combination. Best prediction is in the range of 2-8 per cent for the specific heat capacity, of 5-10 per cent for the thermal conductivity, and of 8-15 for the thermal diffusivity, respectively. Well-log derived thermal conductivity is validated by laboratory data measured on cores from deep boreholes of the Danish Basin, the North German Basin, and the Molasse Basin. Additional validation of thermal conductivity was performed by comparing predicted and measured temperature logs. The maximum deviation between these logs is <3 °C. The thermal-conductivity calculation allowed an evaluation of the depth range in which the palaeoclimatic effect on the subsurface temperature field can be observed in the North German Basin. This effect reduces the surface heat-flow density by 25 mW m-2.

  16. Functionalized mesoporous silica materials for molsidomine adsorption: Thermodynamic study

    SciTech Connect

    Alyoshina, Nonna A.; Parfenyuk, Elena V.

    2013-09-15

    A series of unmodified and organically modified mesoporous silica materials was prepared. The unmodified mesoporous silica was synthesized via sol–gel synthesis in the presence of D-glucose as pore-forming agent. The functionalized by phenyl, aminopropyl and mercaptopropyl groups silica materials were prepared via grafting. The fabricated adsorbent materials were characterized by Fourier transform infrared spectroscopy (FTIR) analysis, N{sub 2} adsorption/desorption and elemental analysis methods. Then their adsorption properties for mesoionic dug molsidomine were investigated at 290–313 K and physiological pH value. Thermodynamic parameters of molsidomine adsorption on the synthesized materials have been calculated. The obtained results showed that the adsorption process of molsidomine on the phenyl modified silica is the most quantitatively and energetically favorable. The unmodified and mercaptopropyl modified silica materials exhibit significantly higher adsorption capacities and energies for molsidomine than the aminopropyl modified sample. The effects are discussed from the viewpoint of nature of specific interactions responsible for the adsorption. - Graphical abstract: Comparative analysis of the thermodynamic characteristics of molsidomine adsorption showed that the adsorption process on mesoporous silica materials is controlled by chemical nature of surface functional groups. Molsidomine adsorption on the phenyl modified silica is the most quantitatively and energetically favorable. Taking into account ambiguous nature of mesoionic compounds, it was found that molsidomine is rather aromatic than dipolar. Display Omitted - Highlights: • Unmodified and organically modified mesoporous silica materials were prepared. • Molsidomine adsorption on the silica materials was studied. • Phenyl modified silica shows the highest adsorption capacity and favorable energy. • Molsidomine exhibits the lowest affinity to aminopropyl modified silica.

  17. Benchmarking dispersion and geometrical counterpoise corrections for cost-effective large-scale DFT calculations of water adsorption on graphene.

    PubMed

    Lorenz, Marco; Civalleri, Bartolomeo; Maschio, Lorenzo; Sgroi, Mauro; Pullini, Daniele

    2014-09-15

    The physisorption of water on graphene is investigated with the hybrid density functional theory (DFT)-functional B3LYP combined with empirical corrections, using moderate-sized basis sets such as 6-31G(d). This setup allows to model the interaction of water with graphene going beyond the quality of classical or semiclassical simulations, while still keeping the computational costs under control. Good agreement with respect to Coupled Cluster with singles and doubles excitations and perturbative triples (CCSD(T)) results is achieved for the adsorption of a single water molecule in a benchmark with two DFT-functionals (Perdew/Burke/Ernzerhof (PBE), B3LYP) and Grimme's empirical dispersion and counterpoise corrections. We apply the same setting to graphene supported by epitaxial hexagonal boron nitride (h-BN), leading to an increased interaction energy. To further demonstrate the achievement of the empirical corrections, we model, entirely from first principles, the electronic properties of graphene and graphene supported by h-BN covered with different amounts of water (one, 10 water molecules per cell and full coverage). The effect of h-BN on these properties turns out to be negligibly small, making it a good candidate for a substrate to grow graphene on. PMID:25056422

  18. Insights into the adsorption capacity and breakthrough properties of a synthetic zeolite against a mixture of various sulfur species at low ppb levels.

    PubMed

    Vellingiri, Kowsalya; Kim, Ki-Hyun; Kwon, Eilhann E; Deep, Akash; Jo, Sang-Hee; Szulejko, Jan E

    2016-01-15

    The sorptive removal properties of a synthetic A4 zeolite were evaluated against sulfur dioxide (SO2) and four reference reduced sulfur compounds (RSC: hydrogen sulfide (H2S), methanethiol (CH3SH), dimethyl sulfide (DMS, (CH3)2S), and dimethyl disulfide (DMDS, CH3SSCH3). To this end, a sorbent bed of untreated (as-received) A4 zeolite was loaded with gaseous standards at four concentration levels (10-100 part-per-billion (ppb (v/v)) at four different volumes (0.1, 0.2, 0.5, and 1 L increments) in both increasing (IO: 0.1-1.0 L) and decreasing volume order (DO: 1.0 to 0.1 L). Morphological properties were characterized by PXRD, FTIR, and BET analysis. The removal efficiency of SO2 decreased from 100% for all concentrations at 0.1 L (initial sample volume) to ∼82% (100 ppb) or ∼96% (10 ppb) at 3.6 L. In contrast, removal efficiency of RSC was near 100% at small loading volumes but then fell sharply, irrespective of concentration (10-100 ppb) (e.g., 32% (DMS) to 52% (H2S) at 100 ppb). The adsorption capacity of zeolite, if expressed in terms of solid-gas partition coefficient (e.g., similar to the Henry's law constant (mmol kg(-1) Pa(-1))), showed moderate variabilities with the standard concentration levels and S compound types such as the minimum of 2.03 for CH3SH (at 20 ppb) to the maximum of 13.9 for SO2 (at 10 ppb). It clearly demonstrated a notable distinction in the removal efficiency of A4 zeolite among the different S species in a mixture with enhanced removal efficiency of SO2 compared to the RSCs. PMID:26562781

  19. Studies of gas adsorption in flexible Metal-Organic frameworks

    NASA Astrophysics Data System (ADS)

    Sircar, Sarmishtha

    minutes to >60 hours, and this in turn, led to a ˜300 fold increase in capacity, convergence of capacities at similar reduced temperatures (critical temperature being the reducing parameter), discontinuities in the isotherms, lowering of gate-opening pressures, changes in the isotherm shapes as well as width of hysteresis loops. Although an experimental time effect was also seen for H2 adsorption at 77K, H2 showed no discontinuity in the adsorption isotherm, adsorption-desorption hysteresis was much less pronounced, and equilibration required significantly less time. The significant difference in rates of adsorption by different gases was attributed to an activated configurational diffusion regime in which the diffusing species moves through a corrugated surface potential when the diameter of the adsorbate approaches that of the pore. A concentration-dependent diffusion model coupled with insufficient equilibration time provides an alternate explanation to describe the stepwise adsorption behavior in GO-MOFs and the changes in capacities. A sigmoid shape of adsorption rate data at cryogenic temperatures is atypical of simple Fickian diffusion, suggesting a more complex mechanistic explanation is required to explain adsorption kinetics to GO-MOFs. Extending the unreacted shrinking core model from the field of catalyst deactivation suggests that relaxation will be much faster relative to diffusion when temperature is increased even by just 10K. From a thermodynamic perspective, adsorption isotherms on (2) demonstrate universality when pressure and temperature are scaled/reduced according to those at critical conditions. At similar reduced conditions, isotherms of gases on (2) converged and both capacity and pressure points of discontinuities showed a predictive behavior. Discrete levels of capacities were found which decrease in temperature. Existence of a universal parameter of heat of gate-opening is calculated and the heats of adsorption and structural expansion are

  20. First-Principles Calculation Study of Mechanism of Cation Adsorption Selectivity of Zeolites: A Guideline for Effective Removal of Radioactive Cesium

    NASA Astrophysics Data System (ADS)

    Nakamura, Hiroki; Okumura, Masahiko; Machida, Masahiko

    2013-02-01

    Zeolites have attracted attention in the reprocessing of radioactive nuclear waste because of their high selective affinity for radioisotopes of Cs. Very recently, their useful properties have been widely utilized in decontamination after the accident at the Fukushima Daiichi Nuclear Power Plants. In this study, we study the high selectivity in the Cs adsorption of zeolites using first-principles calculations and clarify the mechanism of the cation selectivity of zeolites. We obtain energy surfaces on all capture locations for Cs/Na ions inside the micropores of a zeolite, ``mordenite'', and find three crucial conditions for the highly ion-selective exchange of Na for Cs: i) micropores with a radius of ˜3 Å, ii) a moderate Al/Si ratio, and iii) a uniform distribution of Al atoms around each micropore. These insights suggest a guideline for developing zeolites with high Cs selectivity and for enhancing the cation selectivity in more general situations.

  1. Theoretical study and experimental verification on calculation of bearing capacity of aerostatic restrictor system with a gas-impedance model

    NASA Astrophysics Data System (ADS)

    Cheng, Yang; Li, Dongsheng; Hu, Jiacheng; Li, Jiafu

    2015-02-01

    Bearing capacity is a most significant parameter to evaluate the quality of aerostatic restrictor system. A gas-impedance model was established using the theory of gas dynamics to determine the bearing capacity of three aerostatic restrictor systems which were multi-micro channel, dual U-shaped and dual circle-shaped aerostatic restrictor system respectively. Experiments were run using gas-impedance method and finite difference method to prove the validity of gas-impedance method. Experimental results indicated the gas-impedance model method was effective in establishing the bearing capacity of aerostatic restrictor system.

  2. Adsorption kinetics of Rhodamine-B on used black tea leaves

    PubMed Central

    2012-01-01

    Rhodamine B (Rh-B) is one of the most common pollutants in the effluents of textile industries effluents in developing countries. This study was carried out to evaluate the applicability of used black tea leaves (UBTL) for the adsorptive removal of Rh-B from aqueous system by investigating the adsorption kinetics in batch process. The effects of concentration and temperature on adsorption kinetics were examined. First-, second- and pseudo-second order kinetic equations were used to investigate the adsorption mechanism. The adsorption of Rh-B on UBTL followed pseudo-second order kinetics. The equilibrium amount adsorbed and the equilibrium concentration were calculated from pseudo-second-order kinetic plots for different initial concentrations of Rh-B to construct the adsorption isotherm. The adsorption isotherm was well expressed by Langmuir equation. The maximum adsorption capacity of UBTL to Rh-B was found to be 53.2 mg/g at pH = 2.0. The equilibrium amount adsorbed, calculated from pseudo-second-order kinetic plots, increased with temperature increase. The positive value of enthalpy of adsorption, ΔHads = 31.22 kJ/mol, suggested that the adsorption of Rh-B on UBTL at pH = 2.0 is an endothermic process. PMID:23369452

  3. Studies on adsorption of mono- and multi-chromophoric hemicyanine dyes on silver nanoparticles by surface-enhanced resonance raman and theoretical calculations

    NASA Astrophysics Data System (ADS)

    Biswas, Nandita; Thomas, Susy; Kapoor, Sudhir; Mishra, Amaresh; Wategaonkar, Sanjay; Mukherjee, Tulsi

    2008-11-01

    Structural and vibrational properties of mono- and multichromophoric hemicyanine (HC) dyes in solution and adsorbed on silver-coated films have been investigated using optical absorption and resonance Raman scattering techniques, with interpretations aided by theoretical calculations. This is the first report on the Raman spectroscopic studies of multichromophoric HC derivatives. The structure of the monomer, N-propyl-4-(p-N,N-dimethylamino styryl)pyridinium bromide (HC3), and its charged and neutral silver complexes (HC3-Ag) in the ground electronic (S0) state were optimized using density functional calculations with the B3LYP method using the 6-31G* and LANL2DZ basis sets. The ground state structure of N-hexyl-4-(p-N,N-dimethylamino styryl)pyridinium bromide (HC6) and multichromophoric HC dyes were computed using the HF /6-31G* method. The negligible shift or broadening observed in the electronic absorption and resonance Raman spectra in solution with increasing size of the HC chromophore suggests that the excitations are localized within individual monomer units in bis and tetra chromophores. However, in the tris chromophore, considerable redshift and broadening were observed, indicating a significant electronic interaction between the nonbonded electrons of the N atom and the aromatic π-system that is supported by the calculated excitation energies using the time-dependent density functional theory method. The effect of HC dye concentration on the electronic absorption spectra of the silver-coated film showed significant broadening, which was attributed to the formation of H- and J-aggregates in addition to the formation of a metal-molecule complex. A considerable redshift along various vibrations observed in the surface-enhanced resonance Raman scattering (SERRS) spectra of the HC derivatives indicates that adsorption on the silver surface leads to a considerable interaction of the electron rich moiety of HC derivatives with the silver surface. The

  4. [Adsorption of Congo red from aqueous solution on hydroxyapatite].

    PubMed

    Zhan, Yan-Hui; Lin, Jian-Wei

    2013-08-01

    The adsorption of Congo red (CR) from aqueous solution on hydroxyapatite was investigated using batch experiments. The hydroxyapatite was effective for CR removal from aqueous solution. The adsorption kinetics of CR on hydroxyapatite well followed a pseudo-second-order model. The equilibrium adsorption data of CR on hydroxyapatite could be described by the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. Thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated and showed that the adsorption of CR on hydroxyapatite was spontaneous and exothermic in nature. The CR adsorption capacity for hydroxyapatite decreased significantly with increasing pH from 8 to 10. Thermal regeneration showed that hydroxyapatite could be used for six desorption-adsorption cycles with high removal efficiency for CR in each cycle. The mechanisms for CR adsorption on hydroxyapatite with pH value below the pH at point of zero charge (pH(PZC)) include electrostatic attraction, hydrogen bonding and Lewis acid-base interaction. The mechanisms for CR adsorption on hydroxyapatite with pH value above its pH(PZC) include hydrogen bonding and Lewis acid-base interaction. Results of this work indicate that hydroxyapatite is a promising adsorbent for CR removal from aqueous solution. PMID:24191561

  5. Enhancement of arsenic adsorption during mineral transformation from siderite to goethite: mechanism and application.

    PubMed

    Guo, Huaming; Ren, Yan; Liu, Qiong; Zhao, Kai; Li, Yuan

    2013-01-15

    Synthesized siderite was used to remove As(III) and As(V) from water solutions under anoxic conditions and oxic conditions. Results showed that As adsorption on synthetic siderite under anoxic conditions was around 10 mg/g calculated with Langmuir isotherm. However, the calculated As adsorption on synthetic siderite under oxic conditions ranged between 115 and 121 mg/g, which was around 11 times higher than that under anoxic conditions. It was found that 75% siderite was transformed into goethite during oxic adsorption. However, synthetic goethite had lower As adsorption capacity than siderite under oxic conditions, although its adsorption capacity was a little higher than siderite under anoxic conditions. It suggested that the coexistence of goethite and siderite bimineral during mineral transformation probably contributed to the robust adsorption capacity of siderite under oxic conditions. Results of extended X-ray absorption fine structure (EXAF) spectroscopy indicated both As(III) and As(V) formed inner-sphere complexes on the surface of As-treated solid regardless of substrates, including the bidentate binuclear corner-sharing ((2)C) complexes and the monodentate mononuclear corner-sharing ((1)V) complexes. Monodenate ((1)V) and bidentate ((2)C) complexes would be related to high As adsorption capacity of siderite under oxic conditions. It showed that more Fe atoms were coordinated with As atom in the monodentate complexes and the bidentate complexes of As(V)/As(III)-treated siderite under oxic conditions, in comparison with As(V)/As(III)-treated siderite under anoxic conditions and As(V)/As(III)-treated goethite. Calcinations of natural siderite resulting in the coexistence of goethite and siderite greatly increased As adsorption on the solid, which confirmed that the coexistence of bimineral during mineral transformation from siderite to goethite greatly enhanced As adsorption capacity of siderite adsorbent. The observation can be applied for modification of

  6. First-principles calculations of the adsorption and hydrogenation reactions of CHx(x=0,4) species on a Fe(100) surface

    SciTech Connect

    Sorescu, D.C.

    2006-04-01

    A previous set of investigations related to adsorption, diffusion, and dissociation properties of CO [D. C. Sorescu, D. L. Thompson, M. M. Hurley, and C. F. Chabalowski, Phys. Rev. B 66, 035416 (2002)] and H2 [D. C. Sorescu, Catal. Today 105, 44 (2005)] on Fe(100) surface have been extended to the case of chemisorption properties of CHx (x=0,4) species on the same surface. Similar to our previous studies, the current work is based on first-principles plane-wave calculations using spin-polarized density functional theory (DFT) and the generalized gradient approximation (GGA). The calculations employ slab geometry and periodic boundary conditions. It was determined that CHx (x=0,2) species preferentially adsorb at the four-folded sites while the CH3 species prefer the binding at the bridge site. In contradistinction, the CH4 molecule is only weakly physisorbed on the surface, independent of surface site or molecular orientation. In the case of the C atom, the adsorption investigations have been extended to include both the coverage effects as well as the possibility for absorption at subsurface sites. The presence of the C atom at either hollow or subsurface sites was found to increase the stability of the other atomic (C, H, O) and molecular or radical species [CO, CHx (x=1,4)] adsorbed on the surface. Beside chemisorption properties, the activation energies for surface diffusion have been determined for all individual CHx (x=0,3)species while in the case of C atom diffusion to subsurface sites have also been considered. Finally, we have determined the minimum energy path for the elementary hydrogenation reactions of CHx (x=0,3) species. We found that for the ensemble of surface processes involving dissociation of CO and H2 on Fe(100) surface followed by hydrogenation of CHx (x=0,3) species with formation of CH4, the CO dissociation is the rate determining step with an activation energy of 24.5 kcal/mol.

  7. Application of van der Waals functionals to the calculation of dissociative adsorption of N2 on W(110) for static and dynamic systems

    NASA Astrophysics Data System (ADS)

    Migliorini, Davide; Nattino, Francesco; Kroes, Geert-Jan

    2016-02-01

    The fundamental understanding of molecule-surface reactions is of great importance to heterogeneous catalysis, motivating many theoretical and experimental studies. Even though much attention has been dedicated to the dissociative chemisorption of N2 on tungsten surfaces, none of the existing theoretical models has been able to quantitatively reproduce experimental reaction probabilities for the sticking of N2 to W(110). In this work, the dissociative chemisorption of N2 on W(110) has been studied with both static electronic structure and ab initio molecular dynamics (AIMD) calculations including the surface temperature effects through surface atom motion. Calculations have been performed using density functional theory, testing functionals that account for the long range van der Waals (vdW) interactions, which were previously only considered in dynamical calculations within the static surface approximation. The vdW-DF2 functional improves the description of the potential energy surface for N2 on W(110), returning less deep molecular adsorption wells and a better ratio between the barriers for the indirect dissociation and the desorption, as suggested by previous theoretical work and experimental evidence. Using the vdW-DF2 functional less trapping-mediated dissociation is obtained compared to results obtained with standard semi-local functionals such as PBE and RPBE, improving agreement with experimental data at Ei = 0.9 eV. However, at Ei = 2.287 and off-normal incidence, the vdW-DF2 AIMD underestimates the experimental reaction probabilities, showing that also with the vdW-DF2 functional the N2 on W(110) interaction is not yet described with quantitative accuracy.

  8. Application of van der Waals functionals to the calculation of dissociative adsorption of N2 on W(110) for static and dynamic systems.

    PubMed

    Migliorini, Davide; Nattino, Francesco; Kroes, Geert-Jan

    2016-02-28

    The fundamental understanding of molecule-surface reactions is of great importance to heterogeneous catalysis, motivating many theoretical and experimental studies. Even though much attention has been dedicated to the dissociative chemisorption of N2 on tungsten surfaces, none of the existing theoretical models has been able to quantitatively reproduce experimental reaction probabilities for the sticking of N2 to W(110). In this work, the dissociative chemisorption of N2 on W(110) has been studied with both static electronic structure and ab initio molecular dynamics (AIMD) calculations including the surface temperature effects through surface atom motion. Calculations have been performed using density functional theory, testing functionals that account for the long range van der Waals (vdW) interactions, which were previously only considered in dynamical calculations within the static surface approximation. The vdW-DF2 functional improves the description of the potential energy surface for N2 on W(110), returning less deep molecular adsorption wells and a better ratio between the barriers for the indirect dissociation and the desorption, as suggested by previous theoretical work and experimental evidence. Using the vdW-DF2 functional less trapping-mediated dissociation is obtained compared to results obtained with standard semi-local functionals such as PBE and RPBE, improving agreement with experimental data at E(i) = 0.9 eV. However, at E(i) = 2.287 and off-normal incidence, the vdW-DF2 AIMD underestimates the experimental reaction probabilities, showing that also with the vdW-DF2 functional the N2 on W(110) interaction is not yet described with quantitative accuracy. PMID:26931713

  9. Reactive adsorption of SO2 on activated carbons with deposited iron nanoparticles.

    PubMed

    Arcibar-Orozco, Javier A; Rangel-Mendez, J Rene; Bandosz, Teresa J

    2013-02-15

    The effect of iron particle size anchored on the surface of commercial activated carbon on the removal of SO(2) from a gas phase was studied. Nanosize iron particles were deposited using forced hydrolysis of FeCl(3) with or without H(3)PO(4) as a capping agent. Dynamic adsorption experiments were carried out on either dry or pre-humidified materials and the adsorption capacities were calculated. The surface of the initial and exhausted materials was extensively characterized by microscopic, porosity, thermogravimetric and surface chemistry. The results indicate that the SO(2) adsorption capacity increased two and half times after the prehumidification process owing to the formation of H(2)SO(4) in the porous system. Iron species enhance the SO(2) adsorption capacity only when very small nanoparticles are deposited on the pore walls as a thin layer. Large iron nanoparticles block the ultramicropores decreasing the accessibility of the active sites and consuming oxygen that rest adsorption centers for SO(2) molecules. Iron nanoparticles of about 3-4 nm provide highly dispersed adsorption sites for SO(2) molecules and thus increase the adsorption capacity of about 80%. Fe(2)(SO(4))(3) was detected on the surface of exhausted samples. PMID:23333487

  10. Kinetics and Thermodynamics of Reserpine Adsorption onto Strong Acidic Cationic Exchange Fiber

    PubMed Central

    Guo, Zhanjing; Liu, Xiongmin; Huang, Hongmiao

    2015-01-01

    The kinetics and thermodynamics of the adsorption process of reserpine adsorbed onto the strong acidic cationic exchange fiber (SACEF) were studied by batch adsorption experiments. The adsorption capacity strongly depended on pH values, and the optimum reserpine adsorption onto the SACEF occurred at pH = 5 of reserpine solution. With the increase of temperature and initial concentration, the adsorption capacity increased. The equilibrium was attained within 20 mins. The adsorption process could be better described by the pseudo-second-order model and the Freundlich isotherm model. The calculated activation energy Ea was 4.35 kJ/mol. And the thermodynamic parameters were: 4.97<ΔH<7.44 kJ/mol, -15.29<ΔG<-11.87 kJ/mol and 41.97<ΔS<47.35 J/mol·K. The thermodynamic parameters demonstrated that the adsorption was an endothermic, spontaneous and feasible process of physisorption within the temperature range between 283 K and 323 K and the initial concentration range between 100 mg/L and 300 mg/L. All the results showed that the SACEF had a good adsorption performance for the adsorption of reserpine from alcoholic solution. PMID:26422265

  11. Adsorption of Gases on Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Mbaye, Mamadou Thiao

    This research focus in studying the interaction between various classical and quantum gases with novel carbon nanostructures, mainly carbon nanotubes (CNTs). Since their discovery by the Japanese physicist Sumio Iijima [1] carbon nanotubes have, experimentally and theoretically, been subjected to many scientific investigation. Studies of adsorption on CNTs are particularly directed toward their better usage in gas storage, gas separation, catalyst, drug delivery, and water purification. We explore the adsorption of different gases entrapped in a single, double, or multi-bundles of CNTs using computer simulations. The first system we investigate consists of Ar and Kr films adsorbed on zigzag or armchair nanotubes. Our simulations revealed that Kr atoms on intermediate size zigzag NTs undergo two phase transitions: A liquid-vapor (L→V), and liquid-commensurate (L→CS) with a fractional coverage of one Kr atoms adsorbed for every four carbon atoms. For Ar on zigzag and armchair NTs, the only transition observed is a L→V. In the second problem, we explore the adsorption of CO2 molecules in a nanotube bundle and calculate the isosteric heat of adsorption of the entrapped molecules within the groove. We observed that the lower the temperature, the higher the isosteric of adsorption. Last, we investigate the adsorption of hydrogen, Helium, and Neon gases on the groove site of two parallel nanotubes. At low temperature, the transverse motion on the plane perpendicular to the tubes' axis is frozen out and as a consequence, the heat capacity is reduced to 1/2. At high temperature, the atoms gain more degree of freedom and as a consequence the heat capacity is 5/2.

  12. Highly enhanced adsorption for the removal of Hg(II) from aqueous solution by Mercaptoethylamine/Mercaptopropyltrimethoxysilane functionalized vermiculites.

    PubMed

    Tran, Lytuong; Wu, Pingxiao; Zhu, Yajie; Yang, Lin; Zhu, Nengwu

    2015-05-01

    Vermiculites modified with Mercaptoethylamine (MEA) and 3-Mercaptopropyltrimethoxysilane (MPTMS) were used as effective adsorbents for the removal of Hg(II) from aqueous solution. The physicochemical characteristics of the pristine and functionalized vermiculites were analyzed by XRD, BET, FTIR, SEM, TEM and Zeta potentials, confirming that the vermiculite was successfully functionalized by the organic ligands containing the thiol (SH) metal-chelating groups. Batch adsorption experiments demonstrated that the factors such as initial pH, contact time, temperature, coexisting cations and initial Hg(II) concentration could significantly influence the adsorption behaviors typically for VER and MEA-VER, whereas the adsorption capacity of MPTMS-VER showed negligible dependence on such factors. The maximum adsorption capacity of Hg(II) ions was greatly improved after functionalization, which was in the order of MPTMS-VER>MEA-VER>VER (286.29 μg g(-1), 176.33 μg g(-1), 99.95 μg g(-1), respectively). The adsorption isotherm could be well described with Langmuir model and the kinetic studies indicated that the adsorption process fitted well with the pseudo-second-order model. The calculated thermodynamic parameters suggested that the adsorption process was feasible and spontaneous. The adsorption mechanism of Hg(II) on thiol groups was studied through XPS analysis. Considering the favorable adsorption capacities, thiol-functionalized vermiculites show a promising application in the removal of Hg(II) from wastewater. PMID:25643962

  13. Evaluation of the adsorptive behavior of cesium and strontium on hydroxyapatite and zeolite for decontamination of radioactive substances.

    PubMed

    Ozeki, K; Aoki, H

    2016-08-12

    Removal of radioactive substances, such as cesium (Cs) and strontium (Sr), has become an emerging issue after the Fukushima Daiichi Nuclear Power Plant Disaster. To assess the possibility that hydroxyapatite (HA) and zeolites can be used for removal of radioactive substances, the adsorption capacities of Cs and Sr on the HA and a zeolite were investigated. The influence of Fe ions on Cs and Sr adsorption on the HA and the zeolite was also evaluated, because Fe ions are the most effective inhibitor of Cs adsorption on the zeolite.In the Cs adsorption process on the HA and the zeolite, the zeolite showed a higher adsorption ratio than the HA, and the maximum sorption capacity of the zeolite was calculated as 196 mg/g, whereas the HA showed a higher Sr adsorption ratio than the zeolite. The maximum sorption capacity of Sr on the HA was 123 mg/g. Under coexistence with Fe, Cs adsorption on the zeolite decreased with increasing Fe concentration, reaching 2.0 ± 0.8% at 0.1 M Fe concentration. In contrast, Cs adsorption on the zeolite was improved by adding the HA. In the case of coexistence of the HA, the Cs adsorption on the mixture of the HA and the zeolite was 52.4% ± 3.6 % at 0.1 M Fe concentration, although Cs adsorption on the HA alone was quite low. In the Fe adsorption processes of the HA and the zeolite, the HA exhibited a maximum sorption capacity of 256 mg/g, which was much higher than that of the zeolite (111 mg/g). The high affinity of Fe on the HA contributes to the improvement of the deteriorated Cs adsorption on the zeolite due to Fe ions. PMID:27567777

  14. Rb+ adsorption at the quartz(101)-aqueous interface: comparison of resonant anomalous x-ray reflectivity with ab initio calculations

    SciTech Connect

    Bellucci, Francesco; Lee, Sang Soo; Kubicki, James D.; Bandura, Andrei V.; Zhang, Zhan; Wesolowski, David J.; Fenter, Paul

    2015-01-29

    We study adsorption of Rb+ to the quartz(101)–aqueous interface at room temperature with specular X-ray reflectivity, resonant anomalous X-ray reflectivity, and density functional theory. The interfacial water structures observed in deionized water and 10 mM RbCl solution at pH 9.8 were similar, having a first water layer at height of 1.7 ± 0.1 Å above the quartz surface and a second layer at 4.8 ± 0.1 Å and 3.9 ± 0.8 Å for the water and RbCl solutions, respectively. The adsorbed Rb+ distribution is broad and consists of presumed inner-sphere (IS) and outer-sphere (OS) complexes at heights of 1.8 ± 0.1 and 6.4 ± 1.0 Å, respectively. Projector-augmented planewave density functional theory (DFT) calculations of potential configurations for neutral and negatively charged quartz(101) surfaces at pH 7 and 12, respectively, reveal a water structure in agreement with experimental results. These DFT calculations also show differences in adsorbed speciation of Rb+ between these two conditions. At pH 7, the lowest energy structure shows that Rb+ adsorbs dominantly as an IS complex, whereas at pH 12 IS and OS complexes have equivalent energies. The DFT results at pH 12 are generally consistent with the two site Rb distribution observed from the X-ray data at pH 9.8, albeit with some differences that are discussed. In conclusion, surface charge estimated on the basis of the measured total Rb+ coverage was -0.11 C/m2, in good agreement with the range of the surface charge magnitudes reported in the literature.

  15. Microcolumn studies of dye adsorption onto manganese oxides modified diatomite.

    PubMed

    Al-Ghouti, M A; Khraisheh, M A M; Ahmad, M N; Allen, S J

    2007-07-19

    The method described here cannot fully replace the analysis of large columns by small test columns (microcolumns). The procedure, however, is suitable for speeding up the determination of adsorption parameters of dye onto the adsorbent and for speeding up the initial screening of a large adsorbent collection that can be tedious if a several adsorbents and adsorption conditions must be tested. The performance of methylene blue (MB), a basic dye, Cibacron reactive black (RB) and Cibacron reactive yellow (RY) was predicted in this way and the influence of initial dye concentration and other adsorption conditions on the adsorption behaviour were demonstrated. On the basis of the experimental results, it can be concluded that the adsorption of RY onto manganese oxides modified diatomite (MOMD) exhibited a characteristic "S" shape and can be simulated effectively by the Thomas model. It is shown that the adsorption capacity increased as the initial dye concentration increased. The increase in the dye uptake capacity with the increase of the adsorbent mass in the column was due to the increase in the surface area of adsorbent, which provided more binding sites for the adsorption. It is shown that the use of high flow rates reduced the time that RY in the solution is in contact with the MOMD, thus allowing less time for adsorption to occur, leading to an early breakthrough of RY. A rapid decrease in the column adsorption capacity with an increase in particle size with an average 56% reduction in capacity resulting from an increase in the particle size from 106-250 microm to 250-500 microm. The experimental data correlated well with calculated data using the Thomas equation and the bed depth-service time (BDST) equation. Therefore, it might be concluded that the Thomas equation and the BDST equations can produce accurate predication for variation of dye concentration, mass of the adsorbent, flow rate and particle size. In general, the values of adsorption isotherm capacity

  16. Protein nanoparticle interaction: A spectrophotometric approach for adsorption kinetics and binding studies

    NASA Astrophysics Data System (ADS)

    Vaishanav, Sandeep K.; Chandraker, Kumudini; Korram, Jyoti; Nagwanshi, Rekha; Ghosh, Kallol K.; Satnami, Manmohan L.

    2016-08-01

    Investigating the protein nanoparticle interaction is crucial to understand how to control the biological interactions of nanoparticles. In this work, Model protein Bovine serum albumin (BSA) was used to evaluate the process of protein adsorption to the gold nanoparticles (GNPs) surface. The binding of a model protein (BSA) to GNPs was investigated through fluorescence quenching measurements. The strong affinities of BSA for GNPs were confirmed by the high value of binding constant (Ks) which was calculated to be 2.2 × 1011 L/mol. In this consequence, we also investigated the adsorption behavior of BSA on GNPs surface via UV-Vis spectroscopy. The effect of various operational parameters such as pH, contact time, initial BSA concentration, and temperature on adsorption of BSA was investigated using batch adsorption experiments. Kinetics of adsorption was found to follow the pseudo-second order rate equation. The suitability of Freundlich and Langmuir adsorption models to the equilibrium data was investigated. The equilibrium adsorption was well described by the Freundlich isotherm model. The maximum adsorption capacity for BSA adsorbed on GNPs was 58.71 mg/g and equilibrium constant was 0.0058 calculated by the Langmuir model at 298 K and pH = 11.0. Thermodynamic parameters showed that the adsorption of BSA onto GNPs was feasible, spontaneous, and exothermic.

  17. In vitro adsorption of aluminum by an edible biopolymer poly(γ-glutamic acid).

    PubMed

    Rajan, Yesudoss Christu; Inbaraj, Baskaran Stephen; Chen, Bing Huei

    2014-05-21

    Accumulation of aluminum in human has been reported to be associated with dementia, Parkinson's disease, and Alzheimer's disease. The objectives of this study were to evaluate an edible biopolymer poly(γ-glutamic acid) (γ-PGA) for aluminum removal efficiency under in vitro conditions as affected by pH, contact time, aluminum concentration, temperature, ionic strength, and essential metals in both aqueous aluminum solution and simulated gastrointestinal fluid (GIF). A low aluminum adsorption occurred at pH 1.5-2.5, followed by a maximum adsorption at pH 3.0-4.0 and precipitating thereafter as aluminum hydroxide at pH > 4. Adsorption was extremely fast with 81-96% of total adsorption being attained within 1 min, reaching equilibrium in 5-10 min. Kinetic data at low (10 mg/L) and high (50 mg/L) concentrations were well described by pseudo-first-order and pseudo-second-order models, respectively. Equilibrium adsorption isotherms at different temperatures were precisely fitted by both Langmuir and Redlich-Peterson models with the maximum adsorption capacities at 25, 37, and 50 °C being 35.85, 38.68, and 44.23 mg/g, respectively. Thermodynamic calculations suggested endothermic and spontaneous nature of aluminum adsorption by γ-PGA with increased randomness at the solid/solution interface. Variation in ionic strengths did not alter the adsorption capacity, however, the incorporation of essential metals significantly reduced the aluminum adsorption by following the order copper > iron > zinc > calcium > potassium. Compared to aqueous solution, the aluminum adsorption from simulated GIF was high at all studied pH (1-4) with Langmuir monolayer adsorption capacity being 49.43 mg/g at 37 °C and pH 4. The outcome of this study suggests that γ-PGA could be used as a safe detoxifying agent for aluminum. PMID:24799126

  18. CO2 Adsorption on Activated Carbon Honeycomb-Monoliths: A Comparison of Langmuir and Tóth Models

    PubMed Central

    Vargas, Diana P.; Giraldo, Liliana; Moreno-Piraján, Juan C.

    2012-01-01

    Activated carbon honeycomb-monoliths with different textural properties were prepared by chemical activation of African palm shells with H3PO4, ZnCl2 and CaCl2 aqueous solutions of various concentrations. The adsorbents obtained were characterized by N2 adsorption at 77 K, and their carbon dioxide adsorption capacities were measured at 273 K and 1 Bar in volumetric adsorption equipment. The experimental adsorption isotherms were fitted to Langmuir and Tóth models, and a better fit was observed to Tóth equation with a correlation coefficient of 0.999. The maximum experimental values for adsorption capacity at the highest pressure (2.627–5.756 mmol·g−1) are between the calculated data in the two models. PMID:22942710

  19. 2, 4 dichlorophenol (2, 4-DCP) sorption from aqueous solution using granular activated carbon and polymeric adsorbents and studies on effect of temperature on activated carbon adsorption.

    PubMed

    Ghatbandhe, A S; Yenkie, M K N

    2008-04-01

    Adsorption equilibrium, kinetics and thermodynamics of 2,4-dichlorophenol (2,4-DCP), one of the most commonly used chlorophenol, onto bituminous coal based Filtrasorb-400 grade granular activated carbon, were studied in aqueous solution in a batch system with respect to temperature. Uptake capacity of activated carbon found to increase with temperature. Langmuir isotherm models were applied to experimental equilibrium data of 2, 4-DCP adsorption and competitive studies with respect to XAD resin were carried out. Equilibrium data fitted very well to the Langmuir equilibrium model. Adsorbent monolayer capacity 'Q0, Langmuir constant 'b' and adsorption rate constant 'k(a)' were evaluated at different temperatures for activated carbon adsorption. This data was then used to calculate the energy of activation of adsorption and also the thermodynamic parameters, namely the free energy of adsorption, deltaG0, enthalpy of adsorption, deltaH0 and the entropy of adsorption deltaS0. The obtained results showed that the monolayer capacity increases with the increase in temperatures. The obtained values of thermodynamic parameters showed that adsorption of 2,4 DCP is an endothermic process. Synthetic resin was not found efficient to adsorb 2,4 DCP compared to activated carbon. The order of adsorption efficiencies of three resins used in the study found as XAD7HP > XAD4 > XAD1180. PMID:19295102

  20. Phosphate adsorption performance of a novel filter substrate made from drinking water treatment residuals.

    PubMed

    Wang, Wendong; Ma, Cui; Zhang, Yinting; Yang, Shengjiong; Shao, Yue; Wang, Xiaochang

    2016-07-01

    Phosphate is one of the most predominant pollutants in natural waters. Laboratory experiments were conducted to investigate the phosphate adsorption performance of a (NFS) made from drinking water treatment residuals. The adsorption of phosphate on the NFS fitted well with the Freundlich isotherm and pseudo second-order kinetic models. At pH7.0, the maximum adsorption capacity of 1.03mg/g was achieved at 15°C corresponding to the wastewater temperature in cold months, and increased notably to 1.31mg/g at 35°C. Under both acidic conditions (part of the adsorption sites was consumed) and basic conditions (negative charges formed on the surface of NFS, which led to a static repulsion of PO4(3-) and HPO4(2-)), the adsorption of phosphate was slightly inhibited. Further study showed that part of the adsorption sites could be recovered by 0.25mol/L NaOH. The activation energy was calculated to be above 8.0kJ/mol, indicating that the adsorption of phosphate on NFS was probably a chemical process. Considering the strong phosphate adsorption capacity and recoverability, NFS showed great promise on enhancing phosphate removal from the secondary treated wastewater in the filtration process. PMID:27372133

  1. K4Nb6O17·4.5H2O: a novel dual functional material with quick photoreduction of Cr(VI) and high adsorptive capacity of Cr(III).

    PubMed

    Ma, Yuli; Liu, Xiaoqing; Li, Yang; Su, Yiguo; Chai, Zhanli; Wang, Xiaojing

    2014-08-30

    A series of orthorhombic phase K4Nb6O17·4.5H2O was synthesized via a hydrothermal approach. When presented in an acidic pH range, K4Nb6O17·4.5H2O showed a strong ability in quick reduction from Cr(VI) to Cr(III). The resulted Cr(III) ions were removed by an effective adsorption through simply adjusting the solution pH from strong acidity to near neutrality, owing to the sample's unique nano-sheet structure with a wide layer spacing. The Cr(III) ions adsorbed onto samples were released again for reusing by eluting with 1molL(-1) HCl solution, and K4Nb6O17·4.5H2O regenerated by immersing in a KOH solution. The reduction efficiency of Cr(VI) was still up to 98% after irradiation for 60min, and the removal efficiency of Cr(III) ions was as high as 83% even after five cycles. Therefore, K4Nb6O17·4.5H2O is clearly demonstrated to be an excellent dual functional material with quick photoreduction of Cr(VI) and high adsorptive capacity of Cr(III). The relevant materials reported herein might be found various environment-related applications. PMID:25113515

  2. MSTor: A program for calculating partition functions, free energies, enthalpies, entropies, and heat capacities of complex molecules including torsional anharmonicity

    NASA Astrophysics Data System (ADS)

    Zheng, Jingjing; Mielke, Steven L.; Clarkson, Kenneth L.; Truhlar, Donald G.

    2012-08-01

    We present a Fortran program package, MSTor, which calculates partition functions and thermodynamic functions of complex molecules involving multiple torsional motions by the recently proposed MS-T method. This method interpolates between the local harmonic approximation in the low-temperature limit, and the limit of free internal rotation of all torsions at high temperature. The program can also carry out calculations in the multiple-structure local harmonic approximation. The program package also includes six utility codes that can be used as stand-alone programs to calculate reduced moment of inertia matrices by the method of Kilpatrick and Pitzer, to generate conformational structures, to calculate, either analytically or by Monte Carlo sampling, volumes for torsional subdomains defined by Voronoi tessellation of the conformational subspace, to generate template input files, and to calculate one-dimensional torsional partition functions using the torsional eigenvalue summation method. Catalogue identifier: AEMF_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEMF_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 77 434 No. of bytes in distributed program, including test data, etc.: 3 264 737 Distribution format: tar.gz Programming language: Fortran 90, C, and Perl Computer: Itasca (HP Linux cluster, each node has two-socket, quad-core 2.8 GHz Intel Xeon X5560 “Nehalem EP” processors), Calhoun (SGI Altix XE 1300 cluster, each node containing two quad-core 2.66 GHz Intel Xeon “Clovertown”-class processors sharing 16 GB of main memory), Koronis (Altix UV 1000 server with 190 6-core Intel Xeon X7542 “Westmere” processors at 2.66 GHz), Elmo (Sun Fire X4600 Linux cluster with AMD Opteron cores), and Mac Pro (two 2.8 GHz Quad-core Intel Xeon

  3. A Modular Approach To Study Protein Adsorption on Surface Modified Hydroxyapatite.

    PubMed

    Ozhukil Kollath, Vinayaraj; Van den Broeck, Freya; Fehér, Krisztina; Martins, José C; Luyten, Jan; Traina, Karl; Mullens, Steven; Cloots, Rudi

    2015-07-13

    Biocompatible inorganic nano- and microcarriers can be suitable candidates for protein delivery. This study demonstrates facile methods of functionalization by using nanoscale linker molecules to change the protein adsorption capacity of hydroxyapatite (HA) powder. The adsorption capacity of bovine serum albumin as a model protein has been studied with respect to the surface modifications. The selected linker molecules (lysine, arginine, and phosphoserine) can influence the adsorption capacity by changing the electrostatic nature of the HA surface. Qualitative and quantitative analyses of linker-molecule interactions with the HA surface have been performed by using NMR spectroscopy, zeta-potential measurements, X-ray photoelectron spectroscopy, and thermogravimetric analyses. Additionally, correlations to theoretical isotherm models have been calculated with respect to Langmuir and Freundlich isotherms. Lysine and arginine increased the protein adsorption, whereas phosphoserine reduced the protein adsorption. The results show that the adsorption capacity can be controlled with different functionalization, depending on the protein-carrier selections under consideration. The scientific knowledge acquired from this study can be applied in various biotechnological applications that involve biomolecule-inorganic material interfaces. PMID:26096378

  4. Studies on the adsorption of sulfo-group-containing aromatics by chitosan-β-cyclodextrin.

    PubMed

    Shi, Wenjian; Chen, Shuwei; Chang, Fei; Han, Yue; Zhang, Yuanzhang

    2012-01-01

    Chitosan-β-cyclodextrin (CTS-CD) prepared through a crosslinking reaction between chitosan and β-cyclodextrin was employed to adsorb the three following sulfo-group-containing aromatics: disodium 2-naphthol-3,6-disulfonate (R salt), 2-naphthalene sulfonic acid (NSA), and sodium dodecylbenzene sulfonate (SDBS). At 318 K, the saturated adsorption capacity of CTS-CD for R salt, NSA, and SDBS was 431, 416, and 376 mg/g, respectively. The experimental data fitted the second-order model well and the rate constant of the adsorption increased with the temperature increment. The values of apparent activation energy for R salt, NSA, and SDBS were calculated as 33.2, 34.2, and 16.8 kJ/mol respectively. The isothermal adsorption was found following the Langmuir adsorption equation. The negative values of ΔG and the positive values of ΔH indicated that the adsorption process was spontaneous and exothermic. PMID:22339013

  5. Equilibrium and kinetic data and process design for adsorption of Congo Red onto bentonite.

    PubMed

    Bulut, Emrah; Ozacar, Mahmut; Sengil, I Ayhan

    2008-06-15

    The adsorption of Congo Red onto bentonite in a batch adsorber has been studied. Four kinetic models, the pseudo first- and second-order equations, the Elovich equation and the intraparticle diffusion equation, were selected to follow the adsorption process. Kinetic parameters; rate constants, equilibrium adsorption capacities and correlation coefficients, for each kinetic equation were calculated and discussed. It was shown that the adsorption of Congo Red onto bentonite could be described by the pseudo second-order equation. The experimental isotherm data were analyzed using the Langmuir, Freundlich and Temkin equations. Adsorption of Congo Red onto bentonite followed the Langmuir isotherm. A single stage batch adsorber was designed for different adsorbent mass/treated effluent volume ratios using the Langmuir isotherm. PMID:18055111

  6. A comparative study and evaluation of sulfamethoxazole adsorption onto organo-montmorillonites.

    PubMed

    Lu, Laifu; Gao, Manglai; Gu, Zheng; Yang, Senfeng; Liu, Yuening

    2014-12-01

    Three organo-montmorillonites were prepared using surfactants, and their adsorption behaviors toward sulfamethoxazole (SMX) were investigated. The surfactants used were cetyltrimethyl ammonium bromide (CTMAB), 3-(N,N-dimethylhexadecylammonio) propane sulfonate (HDAPS) and 1,3-bis(hexadecyldimethylammonio)-propane dibromide (BHDAP). The properties of the organo-montmorillonites were characterized by X-ray diffraction, scanning electron microscopy and N2 adsorption-desorption isotherm measurements. Results showed that the interlayer spacing of montmorillonite was increased and the surface area as well as the morphology were changed. Batch adsorption experiments showed that the surfactant loading amount had a great effect on the adsorption of SMX. The adsorption process was pH dependent and the maximum adsorption capacity was obtained at pH3 for HDAPS-Mt, while CTMAB-Mt and BHDAP-Mt showed a high removal efficiency at 3-11. The adsorption capacity increased with the initial SMX concentration and contact time but decreased with increasing solution ionic strength. Kinetic data were best described by the pseudo second-order model. Equilibrium data were best represented by the Langmuir model, and the Freundlich constant (n) indicated a favorable adsorption process. The maximum adsorption capacity of SMX was 235.29 mg/g for CTMAB-Mt, 155.28 mg/g for HDAPS-Mt and 242.72 mg/g for BHDAP-Mt. Thermodynamic parameters were calculated to evaluate the spontaneity and endothermic or exothermic nature. The adsorption mechanism was found to be dominated by electrostatic interaction, while hydrophobic interaction played a secondary role. PMID:25499502

  7. [Thermodynamics adsorption and its influencing factors of chlorpyrifos and triazophos on the bentonite and humus].

    PubMed

    Zhu, Li-Jun; Zhang, Wei; Zhang, Jin-Chi; Zai, De-Xin; Zhao, Rong

    2010-11-01

    The adsorption of chlorpyrifos and triazophos on bentonite and humus was investigated by using the equilibrium oscillometry. The adsorption capacity of chlorpyrifos and triazophos on humus was great higher than bentonite at the same concentration. Equilibrium data of Langmuir, Freundlich isotherms showed significant relationship to the adsorption of chlorpyrifos and triazophos on humus (chlorpyrifos: R2 0.996 4, 0.996 3; triazophos: R2 0.998 9, 0.992 4). Langmuir isotherm was the best for chlorpyrifos and triazophos on bentonite (chlorpyrifos: R2 = 0.995 7, triazophos: R2 = 0.998 9). The pH value, adsorption equilibrium time and temperature were the main factors affecting adsorption of chlorpyrifos and triazophos on bentonite and humus. The adsorption equilibrium time on mixed adsorbent was 12h for chlorpyrifos and 6h for triazophos respectively. The mass ratio of humus and bentonite was 12% and 14% respectively, the adsorption of chlorpyrifos and triazophos was the stronglest and tended to saturation. At different temperatures by calculating the thermodynamic parameters deltaG, deltaH and deltaS, confirmed that the adsorption reaction was a spontaneous exothermic process theoretically. The adsorption was the best when the pH value was 6.0 and the temperature was 15 degrees C. PMID:21250454

  8. [Rapid Synthesis of Metal Organic Framework and Its Adsorption Properties on Anonic Dyes].

    PubMed

    Sun, De-shuai; Liu, Ya-li; Zhang, Xiao-dong; Qin, Ting-ting

    2016-03-15

    The waste water containing dyes is difficult to be biochemically treated because of its deep color. Adsorption becomes an important treatment method for this kind of waste water. The iron organic framework was rapidly synthesized at room temperature, and characterized by IR and XRD. Adsorption properties of the materials were tested using four anonic dyes solutions. It was found that the iron organic framework could be formed rapidly, with higher surface area and pore volumes. The pH value of zero point charge was 3.7. The adsorption experiments showed that the iron organic material could remove more dyes in acid solution. The dye adsorption capacity increased with increasing dye concentration. These adsorption data fitted well with Langmuir thermoadsorption equation. The calculated parameter from Langmuir adsorption indicated that the adsorption process could be performed easily. The second order kinetic equation could describe the adsorption data. In addition, the structure of dyes could affect the adsorption process. The metal complex dyes could be quickly removed. PMID:27337895

  9. The effect of lithium adsorption on the formation of 1T-MoS2 phase based on first-principles calculation

    NASA Astrophysics Data System (ADS)

    Zheng, Yuanliao; Huang, Yan; Shu, Haibo; Zhou, Xiaohao; Ding, Jiayi; Chen, Xiaoshuang; Lu, Wei

    2016-04-01

    The effect of lithium adsorption on the phase transition from 1H-MoS2 to 1T-MoS2 is studied by first-principles computations. The results indicate the possibilities of the phase transition for the lithium adsorption. Based on the results of charge density difference and charge-transfer of molybdenum disulfide with lithium adsorption, we elucidated that the mechanism of the changes of electronic property accompanying the phase transition is attributed to the electron transfer of different atoms. According to the result of transition state, it can be found that the phase-transition barrier is related to the coverage of lithium atoms on MoS2 surface. It may be helpful to obtaining experimentally the stable 1T-MoS2 structure.

  10. Cooling Capacity Optimization: Calculation of Hardening Power of Aqueous Solution Based on Poly(N-Vinyl-2-Pyrrolidone)

    NASA Astrophysics Data System (ADS)

    Koudil, Z.; Ikkene, R.; Mouzali, M.

    2013-11-01

    Polymer quenchants are becoming increasingly popular as substitutes for traditional quenching media in hardening metallic alloys. Water-soluble organic polymer offers a number of environmental, economic, and technical advantages, as well as eliminating the quench-oil fire hazard. The close control of polymer quenchant solutions is essential for their successful applications, in order to avoid the defects of structure of steels, such as shrinkage cracks and deformations. The aim of the present paper is to evaluate and optimize the experimental parameters of polymer quenching bath which gives the best behavior quenching process and homogeneous microstructure of the final work-piece. This study has been carried out on water-soluble polymer based on poly(N-vinyl-2-pyrrolidone) PVP K30, which does not exhibit inverse solubility phenomena in water. The studied parameters include polymer concentration, bath temperature, and agitation speed. Evaluation of cooling power and hardening performance has been measured with IVF SmartQuench apparatus, using standard ISO Inconel-600 alloy. The original numerical evaluation method has been introduced in the computation software called SQ Integra. The heat transfer coefficients were used as input data for calculation of microstructural constituents and the hardness profile of cylindrical sample.

  11. Experimental and calculated evaluation of the supporting capacity of steel 13KhGMF welded joints in the low endurance region

    SciTech Connect

    Yakubovskii, V.V.

    1987-03-01

    In recent years thermally-hardened low-alloy steel 13KhGMF, which exhibits high mechanical properties and good weldability, has found use in hydrotechnical structures. In this work, besides studying static and cyclic properties of individual zones of butt joints in steel 13KhGMF, consideration is given to regularities of deformation and failure for welded joints made by the methods indicated with measurement of the geometric parameters of the joints, and a calculated evaluation is also given for their supporting capacity in the region of loading cycles not exceeding 10/sup 5/. The results show that the mechanical properties of the different zones of joints made by manual and electroslag welding differ markedly. The metal resistance of different joints to low-cycle failure is presented. A comparison is shown of experimental and calculated curves for the development of a fatigue crack in welded joints of steel 13KhGMF. The effect of nonuniformity in mechanical properties on the supporting capacity of joints in steel 13KhGMF is shown to be most marked in the quasistatic failure region.

  12. The Adsorption of Reactive Blue 19 Dye onto Cucurbit[8]uril and Cucurbit[6]uril: An Experimental and Theoretical Study.

    PubMed

    Xie, Xiaomei; Li, Xiaolei; Luo, Hanhan; Lu, Huijuan; Chen, Feifei; Li, Wei

    2016-05-01

    The adsorption behavior and mechanism of Reactive Blue 19 (RB19) on cucurbit[6]uril (CB[6]) and cucurbit[8]uril (CB[8]) were investigated. The adsorption isotherm data obtained at different temperatures were fitted well to the Langmuir isotherm, and according to this model, CB[8] and CB[6] exhibited maximum monolayer adsorption capacities of 714.29 and 100.5 mg/g, respectively, at 298.15 K. The adsorption thermodynamic functions ΔG, ΔH, and ΔS were evaluated and revealed that RB19 adsorption onto CB[8] and CB[6] is a spontaneous and enthalpy-driven process. The adsorption process was determined to follow pseudo-second-order kinetics, indicating that chemisorption dominates the adsorption process. Fourier tranform IR spectroscopy, thermogravimetric analysis, and density functional theory (DFT) calculations revealed that the formation of an inclusion complex is the main driving force of adsorption. The phenyl and sulfone moieties of RB19 reside inside the cavity of CB[8], but because of the small cavity, only the sulfone of RB19 resides inside the cavity of CB[6]. Time-dependent DFT calculations revealed that all of the absorption bands of RB19 derive from π → π* transitions, while for the adsorption product of CB[8], the bands located at 590 and 287 nm derive from π → π* transitions and the bands located at 254 and 202 nm mainly derive from intermolecular charge transfer (ICT). PMID:27064317

  13. Solvothermal synthesis of different phase N-TiO2 and their kinetics, isotherm and thermodynamic studies on the adsorption of methyl orange.

    PubMed

    Fan, Jimin; Zhao, Zhihuan; Liu, Wenhui; Xue, Yongqiang; Yin, Shu

    2016-05-15

    The different crystal forms of nitrogen doped-titanium oxide (N-TiO2) with different particle sizes were produced by precipitation-solvothermal method and their adsorption mechanism were also investigated. The adsorption kinetics showed that rutile N-TiO2 displayed higher adsorption capacity than anatase for methyl orange (MO) and its adsorption behavior followed the pseudo-second-order kinetics. The equilibrium adsorption rate of N-TiO2 for MO was well fitted by the Langmuir isotherm model and the adsorption process was monolayer adsorption. The adsorption capacity decreased with increasing temperature. The average correlation coefficient was beyond 97%. The thermodynamic parameters (ΔaGm(ө), ΔaHm(ө), and ΔaSm(ө)) were calculated. It was found that anatase and rutile N-TiO2 had different adsorption enthalpy and entropy. The smaller the particle size, the greater the surface area and surface energy was, then ΔaGm(ө) decreased and the standard equilibrium constant increased at the same time. The adsorption process onto different crystalline phase N-TiO2 was exothermic and non-spontaneous. PMID:26945716

  14. H2 adsorption in Li-decorated porous graphene

    NASA Astrophysics Data System (ADS)

    Seenithurai, S.; Pandyan, R. Kodi; Kumar, S. Vinodh; Munieswaran, P.; Saranya, C.; Mahendran, M.

    2015-06-01

    Porous graphene (PG) has been decorated with Li atoms and subsequently studied the hydrogen (H2) adsorption characteristics, by using Density Functional Theory (DFT)-based calculations. A 2×2 PG has been decorated with eight Li atoms. Upto four H2 molecules get adsorbed on each Li atom. The maximum H2 storage capacity that could be achieved in 2×2PG-8Li is 8.95 wt% which is higher than the U.S. DOE's revised target for the on-board vehicles. The average H2 adsorption binding energy is 0.535 eV/H2, which lies between 0.2-0.6 eV/H2 that is required for achieving adsorption and desorption at near ambient conditions. Thus, Li-decorated PG could be a viable option for on-board automobile applications.

  15. A Study of Adsorptive Characteristics of Australian Coals

    NASA Astrophysics Data System (ADS)

    Lan, Y. P.; Tsai, L. L.

    2012-04-01

    Ever since the Kyoto Protocol, controlling carbon dioxide emission and reducing its content in atmosphere are very important environmental issues up to today. One of the effective methods for permanent sequestration of anthropogenic CO2 is to inject CO2 into deep, unminable coal seams and recover coal bed methane at the same time. CO2-ECBM technology had been proved to be very promising to meet the needs of both environment and energy. Beside other external environment factors, capacity of CO2 adsorption and CH4 desorption are the most influencing factors in selection of sites for the geological storage of CO2. Therefore, the objective of this study is to understand the relationship between gas adsorption and CO2 sequestration, by various experiments for the characterization of Australian of coals. Generally speaking, coal seam gas comprises mostly of CH4, CO2, C2H6, and N2. However, some of the Australian coals were reported with significant amount of CO2 up to 90%, which might strongly affect their capacity of CO2 capture and storage (CCS). High to medium volatile bituminous coals from Sydney Basin and Bowen Basin, southeast Australia were selected in this study. Experiments include maceral composition and vitrinite reflectance measurements, petrographic analysis, Proximate analysis, Ultimate analysis, specific surface area analysis as well as CO2 and CH4 adsorption experiments were performed. Parameters for difference adsorption functions (Langmuir, BET, D-R and D-A) were then calculated to fit their adsorption isotherms the best fitting curve can then be found. Among these adsorption functions, Langmuir is the most basic and commonly used function theory. The results of all experiments were synthesized to discuss the relations among each other, so as to establish the relationship between gas adsorption and coal characteristics.

  16. Fe(II) adsorption onto natural polymers derived from low-grade lignites

    SciTech Connect

    Tarlan, E.; Ahmetli, G.

    2007-09-15

    In comparison with conventional chemical treatment methods for Fe(II) ions, adsorption and ion exchange are considered more easily applicable and economical, depending on the material used. Polymeric rnaterials are the examples used in these commonly applied removal processes. In this study, the adsorption of Fe(II) ions from aqueous solutions onto two different natural polymers, insoluble humic acids (IHAs) extracted from low-grade lignites from Beysehir and Ermenek (in the central Anatolia region, Konya, Turkey), was investigated. The IHAs were synthesized through a series of acid-base reactions, and the obtained precipitates were chemically stable and had about 40% humic matter together with functional carboxyl and hydroxyl groups. The effects of the time and initial metal concentration on the effectiveness of the IHAs for Fe(II) adsorption were determined through batch experiments; the adsorption isotherms and capacities were calculated. The IHAs were effective, with capacities of 59 mg/g for the Beysehir IHA and 57 mg/g for the Ermenek IHA, for Fe removal under neutral pH conditions. The adsorption followed mainly a Freundlich isotherm for both IHAs, and the calculated adsorption rates were 0.86 for the Beysehir IHA and 0.81 for the Ermenek IHA. This indicated that the effectiveness of the Beysehir IHA was slightly higher than that of the Ermenek IHA. The results confirmed the real possibility of the practical application of IHAs for the separation of Fe(II) in aqueous systems.

  17. Experimental, density function theory calculations and molecular dynamics simulations to investigate the adsorption of some thiourea derivatives on iron surface in nitric acid solutions

    NASA Astrophysics Data System (ADS)

    Khaled, K. F.

    2010-09-01

    The effects of thiourea derivatives, namely N-methyl thiourea (MTU), N-propyl thiourea (PTU) and N-allyl thiourea (ATU) on the corrosion behaviour of iron in 1.0 M solution of HNO 3 have been investigated in relation to the concentration of thiourea derivatives. The experimental data obtained using the techniques of weight loss, Tafel polarization and electrochemical impedance spectroscopy, EIS. The results showed that these compounds revealed a good corrosion inhibition, (ATU) being the most efficient and (MTU) the least. Computational studies have been used to find the most stable adsorption sites for thiourea derivatives. This information help to gain further insight about corrosion system, such as the most likely point of attack for corrosion on iron (1 1 0), the most stable site for thiourea derivatives adsorption and the binding energy of the adsorbed layer. The efficiency order of the inhibitors obtained by experimental results was verified by theoretical analysis.

  18. Study on the adsorption properties of O3, SO2, and SO3 on B-doped graphene using DFT calculations

    NASA Astrophysics Data System (ADS)

    Rad, Ali Shokuhi; Shabestari, Sahand Sadeghi; Mohseni, Soheil; Aghouzi, Samaneh Alijantabar

    2016-05-01

    We investigated the structure, adsorption, electronic states, and charge transfer of O3, SO2 and SO3 molecules on the surface of a B-doped graphene using density functional theory (DFT). We found weak physisorption of SO2 (-10.9 kJ/mole, using B3LYP-D) and SO3 (-15.7 kJ/mole, using B3LYP-D) on the surface of B-doped graphene while there is strong chemisorption for O3 (-96.3 kJ/mole, using B3LYP-D) on this surface. Our results suggest the potential of B-doped graphene as a selective sensor/adsorbent for O3 molecule. We noticed some change in hybridizing of boron from sp2 to sp3 upon adsorption of O3 which cases transformation of the adsorbent from 2D to 3D.

  19. Size-fractionation and characterization of landfill leachate and the improvement of Cu{sup 2+} adsorption capacity in soil and aged refuse

    SciTech Connect

    Lou Ziyang; Chai Xiaoli; Niu Dongjie; Ou Yuanyang; Zhao Youcai

    2009-01-15

    Leachate was collected from an anaerobic lagoon at Shanghai Laogang refuse landfill, the largest landfill in China, and the sample was separated into six fractions using micro-filtration membranes, followed by ultra-filtration membranes. Several parameters of the samples were measured, including chemical oxygen demand (COD), total organic carbon (TOC), total solids (TS), pH, total phosphate (TP), total nitrogen (TN), fixed solids (FS), NH{sub 4}{sup +}, orthophosphate, color, turbidity, and conductivity. These parameters were then quantitatively correlated with the molecular weight cutoff of the membrane used. Organic matter in the dissolved fraction (MW < 1 kDa) predominated in the leachate, accounting for 65% of TOC. Thermal infrared spectroscopy was used to characterize the filter residues. Asymmetric and symmetric stretching of methyl and methylene groups, and of functional groups containing nitrogen and oxygen atoms, were observed. In addition, the ability of two different samples to adsorb heavy metals was tested. Cu{sup 2+} was chosen as the representative heavy metal in this study, and the samples were soil; aged refuse, which had spent 8 years in a conventional sanitary landfill; and samples of soil and aged refuse treated for 48 h with leachate in the ratio of 5 g of sample per 50 ml of leachate. Cu{sup 2+} uptake by the raw soil was {approx}4.60 {mu}g/g, while uptake by the leachate-contacted soil and leachate-contacted aged refuse were 5.66 and 5.11 {mu}g/g, respectively. These results show that the organic matter in the leachate enhanced the capacity of aqueous solutions to adsorb Cu{sup 2+}.

  20. Bovine serum albumin adsorption onto functionalized polystyrene lattices: A theoretical modeling approach and error analysis

    NASA Astrophysics Data System (ADS)

    Beragoui, Manel; Aguir, Chadlia; Khalfaoui, Mohamed; Enciso, Eduardo; Torralvo, Maria José; Duclaux, Laurent; Reinert, Laurence; Vayer, Marylène; Ben Lamine, Abdelmottaleb

    2015-03-01

    The present work involves the study of bovine serum albumin adsorption onto five functionalized polystyrene lattices. The adsorption measurements have been carried out using a quartz crystal microbalance. Poly(styrene-co-itaconic acid) was found to be an effective adsorbent for bovine serum albumin molecule adsorption. The experimental isotherm data were analyzed using theoretical models based on a statistical physics approach, namely monolayer, double layer with two successive energy levels, finite multilayer, and modified Brunauer-Emmet-Teller. The equilibrium data were then analyzed using five different non-linear error analysis methods and it was found that the finite multilayer model best describes the protein adsorption data. Surface characteristics, i.e., surface charge density and number density of surface carboxyl groups, were used to investigate their effect on the adsorption capacity. The combination of the results obtained from the number of adsorbed layers, the number of adsorbed molecules per site, and the thickness of the adsorbed bovine serum albumin layer allows us to predict that the adsorption of this protein molecule can also be distinguished by monolayer or multilayer adsorption with end-on, side-on, and overlap conformations. The magnitudes of the calculated adsorption energy indicate that bovine serum albumin molecules are physisorbed onto the adsorbent lattices.

  1. Ultrasound-assisted adsorption of 4-dodecylbenzene sulfonate from aqueous solutions by corn cob activated carbon.

    PubMed

    Milenković, D D; Bojić, A Lj; Veljković, V B

    2013-05-01

    This study was aimed at removal of 4-dodecylbenzene sulfonate (DBS) ions from aqueous solutions by ultrasound-assisted adsorption onto the carbonized corn cob (AC). The main attention was focused on modeling the equilibrium and kinetics of adsorption of DBS onto the AC. The AC was prepared from ground dried corn cob by carbonization and activation by carbon dioxide at 880°C for 2h in a rotary furnace. The adsorption isotherm data were fitted by the Langmuir model in both the absence and the presence of ultrasound (US). The maximum adsorption capacities of the adsorbent for DBS, calculated from the Langmuir isotherms, were 29.41mg/g and 27.78mg/g in the presence of US and its absence, respectively. The adsorption process in the absence and the presence of US obeyed the pseudo second-order kinetics. The intraparticular diffusion model indicated that the adsorption of DBS ions on the AC was diffusion controlled as well as that US promoted intraparticular diffusion. The ΔG° values, -24.03kJ/mol, -25.78kJ/mol and -27.78kJ/mol, were negative at all operating temperatures, verifying that the adsorption of DBS ions was spontaneous and thermodynamically favorable. The positive value of ΔS°=187J/molK indicated the increased randomness at the adsorbent-adsorbate interface during the adsorption of DBS ions by the AC. PMID:23187067

  2. Humic acid adsorption on fly ash and its derived unburned carbon.

    PubMed

    Wang, Shaobin; Zhu, Z H

    2007-11-01

    Fly ash is solid waste from combustion process, containing oxide minerals and unburned carbon. In this investigation, fly ash has been separated into metal oxide mineral section and unburned carbon. The fly ash with different contents of unburned carbon was employed for humic acid adsorption to investigate the influence of unburned carbon on adsorption. It is found that metal oxides and unburned carbon in fly ash exhibit significant difference in humic acid adsorption. The unburned carbon plays the major role in adsorption. Higher content of unburned carbon in fly ash results in higher surface area and thus higher humic acid adsorption. Fly ash and unburned carbon exhibit adsorption capacity of humic acid of 11 and 72 mg/g, respectively, at 30 degrees C, pH 7. Humic acid adsorption is also affected by ion strength, pH, and temperature. The thermodynamic calculations indicate that the adsorption is endothermic nature with DeltaH(0) and DeltaS(0) as 5.79 kJ/mol and 16.0 J/K mol, respectively. PMID:17628583

  3. Gas adsorption on microporous carbon thin films

    SciTech Connect

    O'Shea, S.; Pailthorpe, B.A.; Collins, R.E.; Furlong, D.N. )

    1992-05-01

    A gas adsorption study was performed on amorphous hydrogenated carbon thin films which are deposited by reactive magnetron sputtering using acetylene gas. It is found that the films are highly microporous. Annealing significantly increases the adsorption capacity of the films and decreases the effects of low-pressure hysteresis in the adsorption isotherms. The general gas adsorption behavior closely resembles that of powdered activated carbons. The Dubinin-Radushkevich equation can be used to model the submonolayer adsorption isotherm for a variety of gases. 38 refs., 9 figs., 3 tabs.

  4. O2 adsorption on MO2 (M=Ru, Ir, Sn) films supported on rutile TiO2(110) by DFT calculations: Probing the nature of metal oxide-support interaction.

    PubMed

    Xu, Xianglan; Sun, Xiongfei; Sun, Baozhen; Peng, Honggen; Liu, Wenming; Wang, Xiang

    2016-07-01

    To explore metal oxide-support interaction and its effect on O2 adsorption, periodic DFT calculations were used to explore the most preferred O2 molecular and dissociative adsorption on stoichiometric (MO2) and defective (MO2-x) (M=Ru, Ir, Sn) films supported on rutile TiO2(110), and compared with that on pure surfaces without TiO2(110) support. For defective RuO2-x films, it is revealed that the TiO2(110) support and the film thickness have an evident impact on the O2 adsorbed species. On the contrary, the two factors show little influence for defective IrO2-x and SnO2-x films. The analyses for Bader charge and density of states indicate that the reducibility change of the unsaturated surface Ru atoms, which are adjacent to the bridge oxygen vacancies, is responsible for this O2 adsorption alteration. These results provide insights into the oxide-oxide interaction, and its effect on the properties of supported oxide catalysts. PMID:27060230

  5. Structure and hydrogen adsorption properties in low density nanoporous carbons from simulations

    SciTech Connect

    Peng, L.; Morris, James R

    2012-01-01

    We systematically model the hydrogen adsorption in nanoporous carbons over a wide range of carbon bulk densities (0.6 - 2.4 g/cm3) by using tight binding molecular dynamics simulations for the carbon structures and thermodynamics calculations of the hydrogen adsorption. The resulting structures are in good agreement with the experimental data of ultra-microporous carbon (UMC), a wood-based activated carbon, as indicated by comparisons of the microstructure at atomic level, pair distribution function, and pore size distribution. The hydrogen adsorption calculations in carbon structures demonstrate both a promising hydrogen storage capacity (excess uptake of 1.33 wt% at 298K and 5 MPa, for carbon structures at the lower range of densities) and a reasonable heat of adsorption (12-22 kJ/mol). This work demonstrates that increasing the heat of adsorption does not necessarily increase the hydrogen uptake. In fact, the available adsorption volume is as important as the isosteric heat of adsorption for hydrogen storage in nanoporous carbons.

  6. Chromium(VI) adsorption from aqueous solution onto Moroccan Al-pillared and cationic surfactant stevensite.

    PubMed

    Benhammou, Abdelaziz; Yaacoubi, Abdelrani; Nibou, Lahbib; Tanouti, Boumediane

    2007-02-01

    Batch adsorption of the chromium(VI) onto Moroccan stevensite pillared by Keggin aluminium hydroxypolycation (Al-stevensite) and cationic surfactant cetyltrimethylammoniumbromide (CTA-stevensite) was investigated. The results showed that the CTA-stevensite has a higher affinity than that of Al-stevensite for chromium(VI) adsorption. The adsorption capacities for natural stevensite, Al-stevensite and CTA-stevensite calculated according to the Dubinin-Kaganer-Radushkevich isotherm (DKR) are 13.7, 75.4 and 195.6mmolkg(-1), respectively. The study of the pH effect showed that the optimal range corresponding to the Cr(VI) maximum adsorption on Al-stevensite is pH 3.5-6 and that on CTA-stevensite is pH 2-6. The adsorption rates evaluated according to the pseudo-second-order model are 7.2, 207.2 and 178.5mmolkg(-1)min(-1) for the natural stevensite, Al-stevensite and CTA-stevensite, respectively. The low values of the adsorption energy calculated by (DKR) suggest that anion exchange is the main mechanism that governs the chromate adsorption. PMID:16876943

  7. Adsorption properties of biomass-based activated carbon prepared with spent coffee grounds and pomelo skin by phosphoric acid activation

    NASA Astrophysics Data System (ADS)

    Ma, Xiaodong; Ouyang, Feng

    2013-03-01

    Activated carbon prepared from spent coffee grounds and pomelo skin by phosphoric acid activation had been employed as the adsorbent for ethylene and n-butane at room temperature. Prepared activated carbon was characterized by means of nitrogen adsorption-desorption, X-ray powder diffraction, scanning electron microscope and Fourier transform infrared spectroscope. It was confirmed that pore structure played an important role during the adsorption testes. Adsorption isotherms of ethylene and n-butane fitted well with Langmuir equation. The prepared samples owned better adsorption capacity for n-butane than commercial activated carbon. Isosteric heats of adsorptions at different coverage were calculated through Clausius-Clapeyron equation. Micropore filling effect was explained in a thermodynamic way.

  8. Adsorption and spin state properties of Cr, Ni, Mo, and Pt deposited on Li⁺ and Na⁺ monovalent cation impurities of MgO (001) surface: DFT calculations.

    PubMed

    Shalabi, Ahmad S; Assem, Mervat M; Soliman, Kamal A

    2011-12-01

    We have analyzed, by means of density functional theory calculations and the embedded cluster model, the adsorption and spin-state properties of Cr, Ni, Mo, and Pt deposited on a MgO crystal. We considered deposition at the Mg(2+) site of a defect-free surface and at Li(+) and Na(+) sites of impurity-containing surfaces. To avoid artificial polarization effects, clusters of moderate sizes with no border anions were embedded in simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces. The interaction between a transition metal atom and a surface results from a competition between Hund's rule for the adsorbed atom and the formation of a chemical bond at the interface. We found that the adsorption energies of the metal atoms are significantly enhanced by the cation impurities, and the adsorption energies of the low-spin states of spin-quenched complexes are always more favorable than those of the high-spin states. Spin polarization effects tend to preserve the spin states of the adsorbed atoms relative to those of the isolated atoms. The metal-support interactions stabilize the low-spin states of the adsorbed metals with respect to the isolated metals, but the effect is not always enough to quench the spin. Spin quenching occurs for Cr and Mo complexes at the Mg(2+) site of the pure surface and at Li(+) and Na(+) sites of the impurity-containing surfaces. Variations of the spin-state properties of free metals and of the adsorption and spin-state properties of metal complexes are correlated with the energies of the frontier orbitals. The electrostatic potential energy curves provide further understanding of the nature of the examined properties. PMID:21369929

  9. Metal-organic frameworks with high capacity and selectivity for harmful gases

    PubMed Central

    Britt, David; Tranchemontagne, David; Yaghi, Omar M.

    2008-01-01

    Benchmarks have been established for the performance of six metal-organic frameworks (MOFs) and isoreticular MOFs (IRMOFs, which have the same underlying topology as MOF-5), MOF-5, IRMOF-3, MOF-74, MOF-177, MOF-199, and IRMOF-62, as selective adsorbents for eight harmful gases: sulfur dioxide, ammonia, chlorine, tetrahydrothiophene, benzene, dichloromethane, ethylene oxide, and carbon monoxide. Kinetic breakthrough measurements are used to determine the calculated dynamic adsorption capacity of each “benchmark” MOF for each gas. The capacity of each MOF is compared to that of a sample of Calgon BPL activated carbon. We find that pore functionality plays a dominant role in determining the dynamic adsorption performance of MOFs. MOFs featuring reactive functionality outperform BPL carbon in all but one case and exhibit high dynamic adsorption capacities up to 35% by weight. PMID:18711128

  10. Studies of gas adsorption in flexible Metal-Organic frameworks

    NASA Astrophysics Data System (ADS)

    Sircar, Sarmishtha

    minutes to >60 hours, and this in turn, led to a ˜300 fold increase in capacity, convergence of capacities at similar reduced temperatures (critical temperature being the reducing parameter), discontinuities in the isotherms, lowering of gate-opening pressures, changes in the isotherm shapes as well as width of hysteresis loops. Although an experimental time effect was also seen for H2 adsorption at 77K, H2 showed no discontinuity in the adsorption isotherm, adsorption-desorption hysteresis was much less pronounced, and equilibration required significantly less time. The significant difference in rates of adsorption by different gases was attributed to an activated configurational diffusion regime in which the diffusing species moves through a corrugated surface potential when the diameter of the adsorbate approaches that of the pore. A concentration-dependent diffusion model coupled with insufficient equilibration time provides an alternate explanation to describe the stepwise adsorption behavior in GO-MOFs and the changes in capacities. A sigmoid shape of adsorption rate data at cryogenic temperatures is atypical of simple Fickian diffusion, suggesting a more complex mechanistic explanation is required to explain adsorption kinetics to GO-MOFs. Extending the unreacted shrinking core model from the field of catalyst deactivation suggests that relaxation will be much faster relative to diffusion when temperature is increased even by just 10K. From a thermodynamic perspective, adsorption isotherms on (2) demonstrate universality when pressure and temperature are scaled/reduced according to those at critical conditions. At similar reduced conditions, isotherms of gases on (2) converged and both capacity and pressure points of discontinuities showed a predictive behavior. Discrete levels of capacities were found which decrease in temperature. Existence of a universal parameter of heat of gate-opening is calculated and the heats of adsorption and structural expansion are

  11. Removal of cesium ions from aqueous solution by adsorption onto local Taiwan laterite.

    PubMed

    Wang, Tsing-Hai; Li, Ming-Hsu; Yeh, Wen-Chun; Wei, Yuan-Yaw; Teng, Shi-Ping

    2008-12-30

    Utilization of local Taiwan laterite (LTL) to remove aqueous cesium was investigated in this work under the conditions of various contact time, cesium (Cs) loading and temperature. Experimental results show that adsorption is instantaneous. Freundlich and Langmuir simulation results demonstrate that local Taiwan laterite has high affinity and sorption capacity for Cs at low temperatures, which may be attributed to enhanced desorption as temperature increased. Thermodynamic parameters including DeltaH, DeltaG and DeltaS were calculated and it is indicated that Cs adsorption on LTL is an exothermic, spontaneous and physical adsorption reaction. Moreover, the adsorbed Cs is distributed evenly on the LTL surface, which is confirmed by SEM/EDS mapping images. Furthermore, the absence of apparent shifting or broadening of the kaolinite signal in XRD patterns after Cs adsorption is an indication of the non-expanding characteristic of kaolinite structure. PMID:18448244

  12. Mercapto functionalized silica entrapped polyacrylamide hydrogel: Arsenic adsorption behaviour from aqueous solution.

    PubMed

    Kumar, Rajesh; Jain, S K; Verma, S; Malodia, P

    2015-10-15

    In this article, 3-mercaptopropyl functionalized silica entrapped polyacrylamide hydrogel (MPFS-PAA) was prepared and characterized by FT-IR, scanning electron microscopy (SEM) and energy dispersion X-ray spectroscopy (EDS). Synthesized hydrogel was evaluated for removal of arsenic(III) from aqueous solution. Adsorption studies were carried out by batch method as function of contact time, initial concentration of arsenic and pH. As(III) adsorption data fitted well with Langmuir and Freundlich isotherm models. Adsorption capacity of arsenic 92.5 μg/g was obtained at initial concentration of 100 μg/L by Langmuir isotherm. Adsorption kinetics was tested for pseudo-second order reaction at different contact time. The rate constants of pseudo second order reaction were calculated and good correlation coefficient R(2) 99.67 obtained. The results indicates that MPFS-PAA is an effective adsorbent for removal of As(III) from aqueous solution. PMID:26151463

  13. Adsorptive removal of methylene blue by agar: effects of NaCl and ethanol

    PubMed Central

    2012-01-01

    Adsorption of methylene blue (MB) on agar was investigated as a function of temperature (308-328 K), different concentrations of NaCl and HCl and various weight percentages of binary mixtures of ethanol with water. It was observed that the maximum experimental adsorption capacity, qm, exp, in water is up to 50 mg g-1 and decreases with increase in weight percentage of ethanol and NaCl and HCl concentration compared to that of water. Analysis of data using ARIAN model showed that MB adsorbs as monomer and dimer on the surface of agar. Binding constants of MB to agar were calculated using the Temkin isotherm. The process is exothermic in water and other solutions. The mean adsorption energy (E) value indicated binding of MB to agar is chemical adsorption. Kinetics of this interaction obeys from the pseudo-second-order model and diffusion of the MB molecules into the agar is the main rate-controlling step. PMID:22339759

  14. Kafirin adsorption on ion-exchange resins: isotherm and kinetic studies.

    PubMed

    Kumar, Prashant; Lau, Pei Wen; Kale, Sandeep; Johnson, Stuart; Pareek, Vishnu; Utikar, Ranjeet; Lali, Arvind

    2014-08-22

    Kafirin is a natural, hydrophobic and celiac safe prolamin protein obtained from sorghum seeds. Today kafirin is found to be useful in designing delayed delivery systems and coatings of pharmaceuticals and nutraceuticals where its purity is important and this can be obtained by adsorptive chromatography. This study is the first scientific insight into the isotherm and kinetic studies of kafirin adsorption on anion- and cation-exchange resins for practical applications in preparative scale chromatography. Adsorption isotherms of kafirin were determined for five anion- and two cation-exchange resins in batch systems. Isotherm parameters such as maximum binding capacity and dissociation constant were determined from Langmuir isotherm, and adsorptive capacity and affinity constant from Freundlich isotherm. Langmuir isotherm was found to fit the adsorption equilibrium data well. Batch uptake kinetics for kafirin adsorption on these resins was also carried out and critical parameters including the diffusion coefficient, film mass transfer coefficient, and Biot number for film-pore diffusion model were calculated. Both the isotherm and the kinetic parameters were considered for selection of appropriate resin for kafirin purification. UNOsphere Q (78.26 mg/ml) and Toyopearl SP-650M (57.4 mg/ml) were found to offer better kafirin binding capacities and interaction strength with excellent uptake kinetics under moderate operating conditions. With these adsorbents, film diffusion resistance was found to be major governing factor for adsorption (Bi<10 and δ<1). Based on designer objective function, UNOsphere Q was found be best adsorbent for binding of kafirin. The data presented is valuable for designing large scale preparative adsorptive chromatographic kafirin purification systems. PMID:25022481

  15. Study of Solar Driven Silica gel-Water based Adsorption Chiller

    NASA Astrophysics Data System (ADS)

    Habib, K.; Assadi, M. K.; Zainudin, M. H. B.

    2015-09-01

    In this study, a dynamic behaviour of a solar powered single stage four bed adsorption chiller has been analysed designed for Malaysian climate. Silica gel and water have been used as adsorbent-refrigerant pair. A simulation program has been developed for modeling and performance evaluation of the chiller using the meteorological data of Kuala Lumpur. The optimum cooling capacity and coefficient of performance (COP) are calculated in terms of adsorption/desorption cycle time and regeneration temperature. Results indicate that the chiller is feasible even when low temperature heat source is available. Results also show that the adsorption cycle can achieve a cooling capacity of 14 kW when the heat source temperature is about 85°C.

  16. Protein adsorption using novel carboxymethyl-curdlan microspheres.

    PubMed

    Rafigh, Sayyid Mahdi; Vaziri Yazdi, Ali; Safekordi, Ali Akbar; Heydari Nasab, Amir; Ardjmand, Mehdi; Naderi, Fereshteh; Mozafari, Hamid

    2016-06-01

    Carboxymethyl-curdlan as a water soluble curdlan derivative, was synthesized in an aqueous alkaline medium using monochloroacetic acid. Novel carboxymethyl-curdlan (CC) microspheres were prepared by the method of W/O/W emulsion. The chemical and morphological structures of CC microspheres were investigated by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and particle size analysis. The CC microspheres were spherical, free flowing, non-aggregated and uniform mono-disperse with diameter of 260μm. The prepared CC microspheres were applied to adsorbing Bovine serum albumin (BSA) as model protein. Factors influencing the adsorption of BSA such as solution pH, temperature, initial BSA concentration and ionic strength were examined by batch experiments. The maximum adsorption capacity was calculated as 168mg/g under optimal conditions including BSA initial concentration (4mg/mL), pH (4.7), adsorption time (9h) and temperature (35°C). The adsorption isotherm followed the Langmuir model and the adsorption kinetics fitted the pseudo-second-order model. In addition, the CC microspheres can be also regenerated and re-used. PMID:26964526

  17. Molecular structure-adsorption study on current textile dyes.

    PubMed

    Örücü, E; Tugcu, G; Saçan, M T

    2014-01-01

    This study was performed to investigate the adsorption of a diverse set of textile dyes onto granulated activated carbon (GAC). The adsorption experiments were carried out in a batch system. The Langmuir and Freundlich isotherm models were applied to experimental data and the isotherm constants were calculated for 33 anthraquinone and azo dyes. The adsorption equilibrium data fitted more adequately to the Langmuir isotherm model than the Freundlich isotherm model. Added to a qualitative analysis of experimental results, multiple linear regression (MLR), support vector regression (SVR) and back propagation neural network (BPNN) methods were used to develop quantitative structure-property relationship (QSPR) models with the novel adsorption data. The data were divided randomly into training and test sets. The predictive ability of all models was evaluated using the test set. Descriptors were selected with a genetic algorithm (GA) using QSARINS software. Results related to QSPR models on the adsorption capacity of GAC showed that molecular structure of dyes was represented by ionization potential based on two-dimensional topological distances, chromophoric features and a property filter index. Comparison of the performance of the models demonstrated the superiority of the BPNN over GA-MLR and SVR models. PMID:25529487

  18. [Adsorption and Desorption Characteristics of Endosulfan in Purple Soil].

    PubMed

    Zhao, Yan; Zheng, Guo-can; Zhu, Heng; Zhang, Jin-zhong; Zhu, Xiu-ying; Hu, Shu-chun; Wu, Ya-lin

    2015-09-01

    In order to reveal the residual process of endosulfan in purple soil and protect soil ecological environment, the adsorption and desorption characteristics of endosulfan in purple soil were investigated, and effects of temperature, adsorbent amount, and initial pH of adsorption solution on the adsorption capacity were also examined by static adsorption and desorption experiments. The results showed that the adsorption kinetic process could be well described by the second-order kinetic equation with the initial rate constants of α-, β-endosulfan as 0. 157 and 0. 115 mg.(g.min)-1, respectively. The adsorption thermodynamic process could be well described by the Langmuir isotherm with the maximum adsorption capacities of α-, β-endosulfan as 0. 257 mg . g -1 and 0. 155 mg . g -1, respectively. The adsorption process of endosulfan in purple soil may be an exothermic physicochemical process, and is dominated by physical adsorption. Under the experimental conditions examined in this study, the initial pH of adsorption solution had a relative great influence on the adsorption capacity, whereas the temperature and adsorbent amount had no significant influence. The desorption experiments found that the maximum desorption capacities of α-, β-endosulfan adsorbed in purple soil were 0. 029 mg . g -1 and 0. 017 mg . g -1 at 6 and 4 h, and accounted for 10. 5% and 16. 1% in the maximum adsorption capacities, respectively. PMID:26717711

  19. Removal of phenol from aqueous solutions by adsorption.

    PubMed

    Roostaei, Nadia; Tezel, F Handan

    2004-02-01

    Experiments have been conducted to examine the liquid-phase adsorption of phenol from water by silica gel, HiSiv 3000, activated alumina, activated carbon, Filtrasorb-400, and HiSiv 1000. Experiments were carried out for the analysis of adsorption equilibrium capacities and kinetics. The adsorption isotherm model of the Langmuir-Freundlich type was the best to describe adsorption equilibrium data for phenol for the adsorbents studied. Results of kinetic experiments indicated that HiSiv 1000 had the highest rate of adsorption among the adsorbents studied and therefore more detailed studies were carried out with this adsorbent. The influence of particle size, temperature, and thermal regeneration on adsorption of phenol by HiSiv 1000 was evaluated. From particle size experiments it appeared that adsorption capacity of HiSiv 1000 did not change by changing the particle size, but the rate of adsorption decreased considerably by increasing the particle size. The effect of temperature on adsorption was studied by determining equilibrium isotherms for HiSiv 1000 at 25, 40, and 55 degrees C. The results showed that adsorption capacity decreased with increasing temperature. Thermal regeneration of HiSiv 1000 was performed at 360 degrees C. It was observed that adsorption capacity of HiSiv 1000 did not change after 14 regeneration cycles. Equilibrium experiments showed that the adsorption capacities of activated carbon and Filtrasorb-400 were several times higher than that of HiSiv 1000. PMID:15160741

  20. Calculating in situ density and heat capacity of rocks with GMIN: new type of input data for thermomechanical modeling of subduction zones

    NASA Astrophysics Data System (ADS)

    Burchard, M.; Gerya, T.

    2003-04-01

    The technique of minimizing the Gibbs free energy of specified rock compositions by varying the amounts and compositions of coexisting phases has provided new insights and possibilities for petrological investigations. For thermomechanical modeling of subduction zone processes density, isobaric heat capacity, thermal expansion and compressibility can then be extracted as a function of the amounts and compositions of coexisting phases [1]. At present two programs offer the possibility of calculating phase diagrams with this technique, Holland and Powell's Thermocalc [2] and De Capitani's Theriac/Domino [3] package. The first one is a command line program producing a text output which can be converted to graphics with a user-written MathematicaTM program. It uses the Holland and Powell data base [2]. De Capitani's program is distributed as a Fortran 77 source code and uses the Berman database. Neither of these programs offers interfaces for use with geodynamic modeling programs. We have therefore enhanced our new Gibbs minimization program GMin [4] with an interface able to transfer density, entahalpy and volume values into databases or other programs. The minimization algorithm of our program is based on the de Capitani method [3], modified and adapted for the Holland and Powell database [2]. To achieve rapid convergence and stability of minimization we have optimized the computing strategy for models of solid solutions used in [2]. The standard program is divided in two parts, a front end and a calculation program controlled by the front end program. This construction opens the possibility of starting up several calculations in parallel on different computers and different operating systems. In this way large numbers of calculations can be performed on normal PC-networks (servers and clients) controlled by only one front end program. The front end is able to create pressure and temperature ordered databases containing density, enthalpy, volume and composition which

  1. Adsorptive potential of cationic Basic Yellow 2 (BY2) dye onto natural untreated clay (NUC) from aqueous phase: Mass transfer analysis, kinetic and equilibrium profile

    NASA Astrophysics Data System (ADS)

    Öztürk, A.; Malkoc, E.

    2014-04-01

    In this work, natural untreated clay (NUC) was studied for the removal of Basic Yellow 2 (BY2) from aqueous solution in batch system. The effects of initial BY2 concentration, contact time, solution temperature and solution pH on BY2 adsorption were investigated. Nitrogen sorption measurements were employed to investigate the variation in surface and pore properties after dye adsorption. The adsorbent was characterized by means of FTIR, PSD, TEM, XRD and BET analysis. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin and Scatchard isotherm models. The maximum monolayer adsorption capacity was found to be 833.33 mg/g at 25 °C (at room temperature). The pseudo-second-order kinetic model provided the best fit to the experimental datas compared with pseudo-first-order kinetic adsorption models. To explain mass transfer mechanism of BY2 adsorption, obtained experimental datas were applied Weber and Morris model, Body and Frusawa and Smith models. The results show that the adsorption process is controlled by film diffusion. The thermodynamic parameters such as, Gibbs free energy changes (ΔG°), standard enthalpy change (ΔH°) and standard entropy change (ΔS°) were determined. Adsorption of BY2 on NUC is exothermic and spontaneous in nature. The calculated activation energy of adsorption was found to be 5.24 kJ/mol for BY2. This value indicates that the adsorption process is a physisorption.

  2. EVALUATING MULTICOMPONENT COMPETITIVE ADSORPTION IN FIXED BEDS

    EPA Science Inventory

    An equilibrium column model (ECM) was developed to evaluate multicomponent competition in fixed-bed adsorption columns. The model ignores mass transfer resistances and uses ideal adsorbed solution theory to predict the competitive effects in multicomponent mixtures. The bed capac...

  3. Adsorptive removal of phenol from aqueous solution with zeolitic imidazolate framework-67.

    PubMed

    Pan, Yong; Li, Zhi; Zhang, Zhe; Tong, Xiong-Shi; Li, Hai; Jia, Chong-Zhi; Liu, Bei; Sun, Chang-Yu; Yang, Lan-Ying; Chen, Guang-Jin; Ma, De-Yun

    2016-03-15

    ZIF-67(zinc-methylimidazolate framework-67), one of the zeolitic imidazolate frameworks (ZIFs), was used for the removal of phenol from aqueous solutions via adsorption and shows high adsorption capacity for phenol. The thermodynamic and kinetic adsorption behavior of ZIF-67 for phenol in water with concentration ranging from 50 to 300 ppm were investigated in a batch reactor and a ZIF-67 packed column, respectively. The effects of pH, contact time, zeta potential of the adsorbent and temperature on the adsorption behavior were evaluated, and the results demonstrated that the adsorption is primarily brought about by a specific favorable interaction (electrostatic interaction) between phenol and ZIF-67 surface. The suitability of the Langmuir adsorption model to the equilibrium data was investigated for each phenol-adsorbent system, which the results showed that the equilibrium data for all the phenol-sorbent systems fitted the Langmuir model. Thermodynamic parameters such as Gibbs free energy are calculated from the experimental data at different temperatures. The adsorbent could be perfectly regenerated at 120 °C with little loss in the adsorption ability. PMID:26745178

  4. A fundamental study of the impact of pressure on the adsorption mechanism in reversed-phase liquid chromatography.

    PubMed

    Åsberg, Dennis; Samuelsson, Jörgen; Fornstedt, Torgny

    2016-07-29

    A fundamental investigation of the pressure effect on individual adsorption sites was undertaken based on adsorption energy distribution and adsorption isotherm measurements. For this purpose, we measured adsorption equilibrium data at pressures ranging from 100 to 1000bar at constant flow and over a wide concentration range for three low-molecular-weight solutes, antipyrine, sodium 2-naphthalenesulfonate, and benzyltriethylammonium chloride, on an Eternity C18 stationary phase. The adsorption energy distribution was bimodal for all solutes, remaining clearly so at all pressures. The bi-Langmuir model best described the adsorption in these systems and two types of adsorption sites were identified, one with a low and another with a high energy of interaction. Evidence exists that the low-energy interactions occur at the interface between the mobile and stationary phases and that the high-energy interactions occur nearer the silica surface, deeper in the C18 layer. The contribution of each type of adsorption site to the retention factor was calculated and the change in solute molar volume from the mobile to stationary phase during the adsorption process was estimated for each type of site. The change in solute molar volume was 2-4 times larger at the high-energy site, likely because of the greater loss of solute solvation layer when penetrating deeper into the C18 layer. The association equilibrium constant increased with increasing pressure while the saturation capacity of the low-energy site remained almost unchanged. The observed increase in saturation capacity for the high-energy site did not affect the column loading capacity, which was almost identical at 50- and 950-bar pressure drops over the column. PMID:27357740

  5. Global versus local adsorption selectivity

    NASA Astrophysics Data System (ADS)

    Pauzat, Françoise; Marloie, Gael; Markovits, Alexis; Ellinger, Yves

    2015-10-01

    The origin of the enantiomeric excess found in the amino acids present in the organic matter of carbonaceous meteorites is still unclear. Selective adsorption of one of the two enantiomers existing after a racemic formation could be part of the answer. Hereafter we report a comparative study of the adsorption of the R and S enantiomers of α-alanine and lactic acid on the hydroxylated { } chiral surface of α-quartz using numerical simulation techniques. Structurally different adsorption sites were found with opposite R versus S selectivity for the same molecule-surface couple, raising the problem of whether to consider adsorption as a local property or as a global response characteristic of the whole surface. To deal with the second term of this alternative, a statistical approach was designed, based on the occurrence of each adsorption site whose energy was calculated using first principle periodic density functional theory. It was found that R-alanine and S-lactic acid are the enantiomers preferentially adsorbed, even if the adsorption process on the quartz { } surface stays with a disappointingly poor enantio-selectivity. Nevertheless, it highlighted the important point that considering adsorption as a global property changes perspectives in the search for more efficient enantio-selective supports and more generally changes the way to apprehend adsorption processes in astro-chemistry/biology.

  6. Removal of beta-blockers from aqueous media by adsorption onto graphene oxide.

    PubMed

    Kyzas, George Z; Koltsakidou, Anastasia; Nanaki, Stavroula G; Bikiaris, Dimitrios N; Lambropoulou, Dimitra A

    2015-12-15

    The aim of the present study is the evaluation of graphene oxide (GhO) as adsorbent material for the removal of beta-blockers (pharmaceutical compounds) in aqueous solutions. The composition and morphology of prepared materials were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Atenolol (ATL) and propranolol (PRO) were used as model drug molecules and their behavior were investigated in terms of GhO dosage, contact time, temperature and pH. Adsorption mechanisms were proposed and the pH-effect curves after adsorption were discussed. The kinetic behavior of GhO-drugs system was analyzed after fitting to pseudo-first and -second order equations. The adsorption equilibrium data were fitted to Langmuir, Freundlich and Langmuir-Freundlich model calculating the maximum adsorption capacity (67 and 116 mg/g for PRO and ATL (25 °C), respectively). The temperature effect on adsorption was tested carrying out the equilibrium adsorption experiments at three different temperatures (25, 45, 65 °C). Then, the thermodynamic parameters of enthalpy, free energy and entropy were calculated. Finally, the desorption of drugs from GhO was evaluated by using both aqueous eluants (pH2-10) and organic solvents. PMID:26282775

  7. Molecular simulation of hydrogen adsorption in single-walled carbon nanotubes and idealized carbon slit pores

    NASA Astrophysics Data System (ADS)

    Wang, Qinyu; Johnson, J. Karl

    1999-01-01

    The adsorption of hydrogen gas into single-walled carbon nanotubes (SWNTs) and idealized carbon slit pores is studied by computer simulation. Hydrogen-hydrogen interactions are modeled with the Silvera-Goldman potential. The Crowell-Brown potential is used to model the hydrogen-carbon interactions. Calculations include adsorption inside the tubes, in the interstitial regions of tube arrays, and on the outside surface of isolated tubes. Quantum effects are included through implementation of the path integral formalism. Comparison with classical simulations gives an indication of the importance of quantum effects for hydrogen adsorption. Quantum effects are important even at 298 K for adsorption in tube interstices. We compare our simulations with experimental data for SWNTs, graphitic nanofibers, and activated carbon. Adsorption isotherms from simulations are in reasonable agreement with experimental data for activated carbon, but do not confirm the large uptake reported for SWNTs and nanofibers. Although the adsorption potential for hydrogen in SWNTs is enhanced relative to slit pores of the same size, our calculations show that the storage capacity of an array of tubes is less than that for idealized slit pore geometries, except at very low pressures. Ambient temperature isotherms indicate that an array of nanotubes is not a suitable sorbent material for achieving DOE targets for vehicular hydrogen storage.

  8. Adsorption and desorption characteristics of hydrophobic pesticide endosulfan in four Indian soils.

    PubMed

    Kumar, Mathava; Philip, Ligy

    2006-02-01

    Adsorption and desorption characteristics of endosulfan in four Indian soils were studied extensively. The soils used were clayey soil (CL--lean clay with sand), red soil (GM--silty gravel with sand), sandy soil (SM--silty sand with gravel) and composted soil (PT--peat) as per ASTM (American Society for Testing and Materials) standards. Adsorption and desorption rates were calculated from kinetic studies. These values varied for alpha and beta endosulfan depending on the soil type. Maximum specific adsorption capacities (qmax) for different soils were calculated by Langmuir model. The values varied from 0.1 to 0.45 mg g(-1) for alpha endosulfan and 0.0942-0.2722 mg g(-1) for beta endosulfan. Maximum adsorption took place in clay soil followed by composted soil and red soil. Adsorptions of alpha and beta endosulfan were negligible in sand. The binding characteristics of various functional groups were calculated using Scatchard plot. Effect of functional groups was more predominant in clayey soil. Organic matter also played a significant role in adsorption and desorption of endosulfan. Endosulfan adsorption decreased drastically in clay soil when the pH was reduced. Desorption was higher at both acidic and alkaline pH ranges compared to neutral pH. Results indicated that alpha endosulfan is more mobile compared to beta endosulfan and mobility of endosulfan is maximum in sandy soil followed by red soil. It can be inferred that crystal lattice of the clay soil plays a significant role in endosulfan adsorption and desorption. Immobilization of endosulfan is more advisable in clay soil whereas biological and or chemical process can be applied effectively for the remediation of other soil types. PMID:15990147

  9. Powdered activated carbon adsorption of two fishy odorants in water: Trans,trans-2,4-heptadienal and trans,trans-2,4-decadienal.

    PubMed

    Li, Xin; Wang, Jun; Zhang, Xiaojian; Chen, Chao

    2015-06-01

    Powdered activated carbon (PAC) adsorption of two fishy odorants, trans,trans-2,4-heptadienal (HDE) and trans,trans-2,4-decadienal (DDE), was investigated. Both the pseudo first-order and the pseudo second-order kinetic models well described the kinetics curves, and DDE was more readily removed by PAC. In isotherm tests, both Freundlich and Modified Freundlich isotherms fitted the experimental data well. PAC exhibited a higher adsorption capacity for DDE than for HDE, which could be ascribed to the difference in their hydrophobicity. The calculated thermodynamic parameters (ΔG0, ΔH0, and ΔS0) indicated an exothermic and spontaneous adsorption process. PAC dosage, pH, and natural organic matter (NOM) presence were found to influence the adsorption process. With increasing PAC dosage, the pseudo first-order and pseudo second-order rate constants both increased. The value of pH had little influence on HDE or DDE molecules but altered the surface charge of PAC, and the maximum adsorption capacity occurred at pH9. The presence of NOM, especially the fraction with molecular weight less than 1k Dalton, hindered the adsorption. The study showed that preloaded NOM impaired the adsorption capacity of HDE or DDE more severely than simultaneously fed NOM did. PMID:26040727

  10. Highly efficient ultrasonic-assisted removal of Hg(II) ions on graphene oxide modified with 2-pyridinecarboxaldehyde thiosemicarbazone: Adsorption isotherms and kinetics studies.

    PubMed

    Tadjarodi, Azadeh; Moazen Ferdowsi, Somayeh; Zare-Dorabei, Rouholah; Barzin, Ahmad

    2016-11-01

    A novel adsorbent, based on modifying graphene oxide (GO) chemically with 2-pyridinecarboxaldehyde thiosemicarbazone (2-PTSC) as ligand, was designed by facile process for removal of Hg(II) from aqueous solution. Characterization of the adsorbent was performed using various techniques, such as FT-IR, XRD, XPS, SEM and AFM analysis. The adsorption capacity was affected by variables such as adsorbent dosage, pH solution, Hg(2+) initial concentration and sonicating time. These variables were optimized by rotatable central composite design (CCD) under response surface methodology (RSM). The predictive model for Hg(II) adsorption was constructed and applied to find the best conditions at which the responses were maximized. In this conditions, the adsorption capacity of this adsorbent for Hg(2+) ions was calculated to be 309mgg(-1) that was higher than that of GO. Appling the ultrasound power combined with adsorption method was very efficient in shortening the removal time of Hg(2+) ions by enhancing the dispersion of adsorbent and metal ions in solution and effective interactions among them. The adsorption process was well described by second-order kinetic and Langmuir isotherm model in which the maximum adsorption capacity (Qm) was found to be 555mgg(-1) for adsorption of Hg(2+) ions over the obtained adsorbent. The performance of adsorbent was examined on the real wastewaters and confirmed the applicability of adsorbent for practical applications. PMID:27245963

  11. The removal of phenol from aqueous solutions by adsorption using surfactant-modified bentonite and kaolinite.

    PubMed

    Alkaram, Uday F; Mukhlis, Abduljabar A; Al-Dujaili, Ammar H

    2009-09-30

    The natural bentonite (BC) and kaolinite (KC) were modified with two surfactant of hexadecyltrimethylammonium bromide (HDTMA) and phenyltrimethylammonium bromide (PTMA) to form four kinds of organic-modified clays, i.e., HDTMA-bentonite (BHM), HDTMA-kaolinite (KHM), PTMA-bentonite (KPM) and PTMA-kaolinite (KPM). The modified minerals were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and FT-IR spectroscopy. The surface areas were determined using methylene blue adsorption method. Cation-exchange capacity (CEC) was estimated using an ethylenediamine complex of copper method and the modifier loading was calculated from the total carbon analysis. The ability of raw and organo-modified clays to remove phenol from aqueous solutions has been carried out as a function of contact time, pH and temperatures using a batch technique. The removal of phenol from aqueous solutions by modified clays seems to be more effective than unmodified samples. The adsorption capacity was found to increase with increasing temperature indication that the adsorptions were endothermic. The adsorption of phenol onto these clays was found to be increased by increasing of pH value and the adsorption patterns data are correlated well by Langmuir and Freundlich isotherm models and that the adsorption is physical in nature. The experimental data fitted very well with the pseudo-second-order kinetic model. The thermodynamic study of adsorption process showed that the adsorption of phenol with these six adsorbents was carried out spontaneously, and the process was endothermic in nature. PMID:19464105

  12. Adsorption of selected volatile organic vapors on multiwall carbon nanotubes.

    PubMed

    Shih, Yang-hsin; Li, Mei-syue

    2008-06-15

    Carbon nanotubes are expected to play an important role in sensing, pollution treatment and separation techniques. This study examines the adsorption behaviors of volatile organic compounds (VOCs), n-hexane, benzene, trichloroethylene and acetone on two multiwall carbon nanotubes (MWCNTs), CNT1 and CNT2. Among these VOCs, acetone exhibits the highest adsorption capacity. The highest adsorption enthalpies and desorption energies of acetone were also observed. The strong chemical interactions between acetone and both MWCNTs may be the result from chemisorption on the topological defects. The adsorption heats of trichloroethylene, benzene, and n-hexane are indicative of physisorption on the surfaces of both MWCNTs. CNT2 presents a higher adsorption capacity than CNT1 due to the existence of an exterior amorphous carbon layer on CNT2. The amorphous carbon enhances the adsorption capacity of organic chemicals on carbon nanotubes. The morphological and structure order of carbon nanotubes are the primary affects on the adsorption process of organic chemicals. PMID:17980962

  13. CRYOGENIC ADSORPTION OF HYDROGEN ISOTOPES OVER NANO-STRUCTURED MATERIALS

    SciTech Connect

    Xiao, S.; Heung, L.

    2010-10-07

    Porous materials such as zeolites, activated carbon, silica gels, alumina and a number of industrial catalysts are compared and ranked for hydrogen and deuterium adsorption at liquid nitrogen temperature. All samples show higher D{sub 2} adsorption than that of H{sub 2}, in which a HY sample has the greatest isotopic effect while 13X has the highest hydrogen uptake capacity. Material's moisture content has significant impact to its hydrogen uptake. A material without adequate drying could result in complete loss of its adsorption capacity. Even though some materials present higher H{sub 2} adsorption capacity at full pressure, their adsorption at low vapor pressure may not be as good as others. Adsorption capacity in a dynamic system is much less than in a static system. A sharp desorption is also expected in case of temperature upset.

  14. Adsorption of octylamine on titanium dioxide

    NASA Astrophysics Data System (ADS)

    Siwińska, Daria; Kołodziejczak-Radzimska, Agnieszka; Krysztafkiewicz, Andrzej; Jesionowski, Teofil

    2009-05-01

    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 TiO 2 in the production of pharmaceuticals.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

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

    2016-05-14

    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. PMID:27179497

  17. Adsorption of sulfur dioxide by native clinoptilolite

    SciTech Connect

    Merkun, I.I.; Kel'tsev, N.V.; Bratchuk, F.N.; Rogovik, M.I.

    1982-11-10

    The purpose of the present work was to study the adsorption capacity of the little-studied native clinoptilolite from Beregovo in the Zakarpatskaya region (Ruthenia) for sulfur dioxide. Adsorption of SO/sub 2/ under analogous conditions by Patrick's silica gel, prepared by us by a known method, was studied for comparison. Results indicated that native clinoptilolite studied has much higher adsorption capacity than Patrick's silica gel for sulfur dioxide in the temperature range studied. The adsorption capacity of this zeolite alters little with increase of temperature in the range 25-75/sup 0/. It is considered that native clinoptilolite can be used for removing sulfur dioxide from waste gases in the temperature and pressure ranges studied.

  18. Superior adsorption of pharmaceutical molecules by highly porous BN nanosheets.

    PubMed

    Liu, Dan; Lei, Weiwei; Qin, Si; Klika, Karel D; Chen, Ying

    2016-01-01

    Highly porous boron nitride nanosheets (BNNSs) were tested as a re-usable adsorbent for the removal of pharmaceuticals from aqueous solution. The BNNSs exhibit both unprecedentedly high adsorption capacities and excellent recyclability while maintaining their high adsorption capacity by a simple regeneration process. These advantages render BNNSs a promising material for water remediation applications. PMID:26618906

  19. Simultaneous removal of potent cyanotoxins from water using magnetophoretic nanoparticle of polypyrrole: adsorption kinetic and isotherm study.

    PubMed

    Hena, S; Rozi, R; Tabassum, S; Huda, A

    2016-08-01

    Cyanotoxins, microcystins and cylindrospermopsin, are potent toxins produced by cyanobacteria in potable water supplies. This study investigated the removal of cyanotoxins from aqueous media by magnetophoretic nanoparticle of polypyrrole adsorbent. The adsorption process was pH dependent with maximum adsorption occurring at pH 7 for microcystin-LA, LR, and YR and at pH 9 for microcystin-RR and cylindrospermopsin (CYN). Kinetic studies and adsorption isotherms reflected better fit for pseudo-second-order rate and Langmuir isotherm model, respectively. Thermodynamic calculations showed that the cyanotoxin adsorption process is endothermic and spontaneous in nature. The regenerated adsorbent can be successfully reused without appreciable loss of its original capacity. PMID:27072032

  20. Multiscale Study of Hydrogen Adsorption on Six Designed Covalent Organic Frameworks Based on Porphyrazine, Cyclobutane and Scandium

    NASA Astrophysics Data System (ADS)

    Li, Le-Le; Gao, Teng-Fei; Zhang, Ruan-Yu; Zhang, Hong

    2014-09-01

    The first-principles method of hydrogen adsorption is used to investigate the interaction of H2 with the scandium-porphyrazine (Sc-Pz) and porphyrazine (Pz) clusters. The result shows that the interaction of H2 with Sc-Pz is stronger than with Pz. Then grand canonical Monte Carlo simulations are used to investigate hydrogen adsorption in six designed covalent organic frameworks (COFs), which are designed based on porphyrazine, cyclobutane and scandium. When the pressure is from 0.1 to 100 bar and the temperature is 298 K and 77 K, the hydrogen adsorption capacities of the six COFs are calculated. We further study the importance of Sc and fillers to improve the H2 uptake in the modified COFs by analyzing the isosteric heat of hydrogen adsorption.

  1. [Effect of SO2 volume fraction in flue gas on the adsorption behaviors adsorbed by ZL50 activated carbon and kinetic analysis].

    PubMed

    Gao, Ji-xian; Wang, Tie-feng; Wang, Jin-fu

    2010-05-01

    The influence of SO2 dynamic adsorption behaviors using ZL50 activated carbon for flue gas desulphurization and denitrification under different SO2 volume fraction was investigated experimentally, and the kinetic analysis was conducted by kinetic models. With the increase of SO2 volume fraction in flue gas, the SO2 removal ratio and the activity ratio of ZL50 activated carbon decreased, respectively, and SO2 adsorption rate and capacity increased correspondingly. The calculated results indicate that Bangham model has the best prediction effect, the chemisorption processes of SO2 was significantly affected by catalytic oxidative reaction. The adsorption rate constant of Lagergren's pseudo first order model increased with the increase of inlet SO, volume fraction, which indicated that catalytic oxidative reaction of SO2 adsorbed by ZL50 activated carbon may be the rate controlling step in earlier adsorption stage. The Lagergren's and Bangham's initial adsorption rate were deduced and defined, respectively. The Ho's and Elovich's initial adsorption rate were also deduced in this paper. The Bangham's initial adsorption rate values were defined in good agreement with those of experiments. The defined Bangham's adsorptive reaction kinetic model can describe the SO2 dynamic adsorption rate well. The studied results indicated that the SO2 partial order of initial reaction rate was one or adjacent to one, while the O2 and water vapor partial order of initial reaction rate were constants ranging from 0.15-0.20 and 0.45-0.50, respectively. PMID:20623845

  2. Macroscopic and Microscopic Investigation of U(VI) and Eu(III) Adsorption on Carbonaceous Nanofibers.

    PubMed

    Sun, Yubing; Wu, Zhen-Yu; Wang, Xiangxue; Ding, Congcong; Cheng, Wencai; Yu, Shu-Hong; Wang, Xiangke

    2016-04-19

    The adsorption mechanism of U(VI) and Eu(III) on carbonaceous nanofibers (CNFs) was investigated using batch, IR, XPS, XANES, and EXAFS techniques. The pH-dependent adsorption indicated that the adsorption of U(VI) on the CNFs was significantly higher than the adsorption of Eu(III) at pH < 7.0. The maximum adsorption capacity of the CNFs calculated from the Langmuir model at pH 4.5 and 298 K for U(VI) and Eu(III) were 125 and 91 mg/g, respectively. The CNFs displayed good recyclability and recoverability by regeneration experiments. Based on XPS and XANES analyses, the enrichment of U(VI) and Eu(III) was attributed to the abundant adsorption sites (e.g., -OH and -COOH groups) of the CNFs. IR analysis further demonstrated that -COOH groups were more responsible for U(VI) adsorption. In addition, the remarkable reducing agents of the R-CH2OH groups were responsible for the highly efficient adsorption of U(VI) on the CNFs. The adsorption mechanism of U(VI) on the CNFs at pH 4.5 was shifted from inner- to outer-sphere surface complexation with increasing initial concentration, whereas the surface (co)precipitate (i.e., schoepite) was observed at pH 7.0 by EXAFS spectra. The findings presented herein play an important role in the removal of radionuclides on inexpensive and available carbon-based nanoparticles in environmental cleanup applications. PMID:26998856

  3. Removal of vertigo blue dyes from Batik textile wastewater by adsorption onto activated carbon and coal bottom ash

    NASA Astrophysics Data System (ADS)

    Kusmiyati, L., Puspita Adi; Deni, V.; Robi Indra, S.; Islamica, Dlia; Fuadi, M.

    2016-04-01

    Removal of vertigo blue dye from batik textile wastewater was studied by adsorptionprocess onto activated carbon (AC) and coal bottom ash (CBA).The influence of experimental conditions (pH solution, dye concentration, and contact time) were studied on the both adsorbents. At equilibrium conditions, the data were fitted to Langmuir and Freundlich adsorption models. The maximum adsorption capacity calculated from the Langmuir model for carbon active was 6.29mg/g at pH that found to be considerably higher than that obtained for coal bottom ash 3.72mg/g pH 9. From Freundlich model, the maximum adsorption capacity is less for coal bottom ash (pH 9) than that for carbon active (pH4).

  4. Fluoride adsorption onto amorphous aluminum hydroxide: Roles of the surface acetate anions.

    PubMed

    Zhang, Yong-Xing; Jia, Yong

    2016-12-01

    Amorphous aluminum hydroxide with hydroxyl groups, acetate anions and chlorine anions enriched surface was synthesized, and was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. Batch experiments were performed to study the influence of various experimental parameters such as contact time, initial fluoride concentration, temperature, pH value and the presence of competing anions on the adsorption of fluoride on amorphous aluminum hydroxide. The kinetic data was well fitted to pseudo-second-order model. The fluoride adsorption on the amorphous aluminum hydroxide can be well described by the Langmuir model, and the maximum adsorption capacity was 63.94mgg(-1) at pH 7.0. Thermodynamic parameters including the Gibbs free energy, standard enthalpy and standard entropy were calculated, and the results suggested that the adsorption of fluoride on the amorphous aluminum hydroxide was a feasible, spontaneous and exothermic process. The adsorption mechanism was revealed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analysis. The results suggested that the surface acetate anions and surface chlorine anions played important roles in the fluoride removal process. PMID:27565961

  5. Protein Adsorption in Three Dimensions

    PubMed Central

    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 protein-adsorption literature identifies some of the sources of inconsistency among many investigators participating in more than five decades of focused research. A tutorial on the fundamental biophysical chemistry of protein adsorption sets the stage for a detailed discussion of the kinetics and thermodynamics of protein adsorption, including adsorption competition between two proteins for the same adsorbent immersed in a binary-protein mixture. Both kinetics and steady-state adsorption can be rationalized using a single interpretive paradigm asserting that protein molecules partition from solution into a three-dimensional (3D) interphase separating bulk solution from the physical-adsorbent surface. Adsorbed protein collects in one-or-more adsorbed layers, depending on protein size, solution concentration, and adsorbent surface energy (water wettability). The adsorption process begins with the hydration of an adsorbent surface brought into contact with an aqueous-protein solution. Surface hydration reactions instantaneously form a thin, pseudo-2D interface between the adsorbent and protein solution. Protein molecules rapidly diffuse into this newly-formed interface, creating a truly 3D interphase that inflates with arriving proteins and fills to capacity within milliseconds at mg/mL bulk-solution concentrations CB. This inflated interphase subsequently undergoes time-dependent (minutes-to-hours) decrease in volume VI by expulsion of either-or-both interphase water and

  6. Development of a polyaniline-lignocellulose composite for optimal adsorption of Congo red.

    PubMed

    Debnath, Sushanta; Ballav, Niladri; Maity, Arjun; Pillay, Kriveshini

    2015-04-01

    A polyaniline lignocellulose composite (PLC) was synthesized and used in the removal of Congo red (CR) from aqueous solution. The adsorption process showed good fits to both the pseudo-second-order and pseudo-first-order models and the Redlich Peterson isotherm. Boundary layer diffusion was the rate-limiting step. The adsorption was spontaneous and endothermic. The combined effect of pH and initial dye concentration was antagonistic; the combined effect of initial dye concentration and temperature was synergistic, while the combined effect of pH and temperature was reciprocal. The maximum CR adsorption capacity of PLC was evaluated as 1672.5 mg g(-1). The optimal removal was calculated as 99.85% at pH 4.29, initial dye concentration of 28.5 mg L(-1) and adsorbent dosage of 0.69 g L(-1). The predicted removal capacity showed a good correlation to the experimental results. PLC has demonstrated a superior adsorption capacity to many other adsorbents reported and could be used as an efficient adsorbent for CR removal from industrial wastewater. PMID:25620783

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

    SciTech Connect

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

    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. A method for the calculation of the adsorbed phase volume and pseudo-saturation pressure from adsorption isotherm data on activated carbon.

    PubMed

    Srinivasan, Kandadai; Saha, Bidyut Baran; Ng, Kim Choon; Dutta, Pradip; Prasad, Madhu

    2011-07-21

    We propose a new method for evaluating the adsorbed phase volume during physisorption of several gases on activated carbon specimens. We treat the adsorbed phase as another equilibrium phase which satisfies the Gibbs equation and hence assume that the law of rectilinear diameters is applicable. Since invariably the bulk gas phase densities are known along measured isotherms, the constants of the adsorbed phase volume can be regressed from the experimental data. We take the Dubinin-Astakhov isotherm as the model for verifying our hypothesis since it is one of the few equations that accounts for adsorbed phase volume changes. In addition, the pseudo-saturation pressure in the supercritical region is calculated by letting the index of the temperature term in Dubinin's equation to be temperature dependent. Based on over 50 combinations of activated carbons and adsorbates (nitrogen, oxygen, argon, carbon dioxide, hydrocarbons and halocarbon refrigerants) it is observed that the proposed changes fit experimental data quite well. PMID:21670804

  9. Development of a sodium alginate-based organic/inorganic superabsorbent composite hydrogel for adsorption of methylene blue.

    PubMed

    Thakur, Sourbh; Pandey, Sadanand; Arotiba, Omotayo A

    2016-11-20

    Batch adsorption experiments were carried out for the removal of methylene blue (MB) cationic dye from aqueous solution using organic/inorganic hydrogel nanocomposite of titania incorporated sodium alginate crosslinked polyacrylic acid (SA-cl-poly(AA)-TiO2). The hydrogel was prepared by graft copolymerization of acrylic acid (AA) onto sodium alginate (SA) biopolymer in the presence of a crosslinking agent, a free radical initiator and TiO2 nanoparticles. The hydrogel exhibited a high swelling capacity of 412.98g/g. The factors influencing adsorption capacity of the absorbents such as pH of the dye solutions, initial concentration of the dye, amount of absorbents, and temperature were investigated and used to propose a possible mechanism of adsorption. The adsorption process concurs with a pseudo-second-order kinetics and with Langmuir isotherm equation. A very high adsorption capacity (Qmax=2257.36 (mg/g)) and a correlation coefficient of 0.998 calculated from isotherm equations show the high efficiency of the absorbent and thus expected to be a good candidate as an absorbent for water treatment. PMID:27561469

  10. H{sub 2} adsorption in Li-decorated porous graphene

    SciTech Connect

    Seenithurai, S.; Pandyan, R. Kodi; Kumar, S. Vinodh; Munieswaran, P.; Saranya, C.; Mahendran, M.

    2015-06-24

    Porous graphene (PG) has been decorated with Li atoms and subsequently studied the hydrogen (H{sub 2}) adsorption characteristics, by using Density Functional Theory (DFT)-based calculations. A 2×2 PG has been decorated with eight Li atoms. Upto four H{sub 2} molecules get adsorbed on each Li atom. The maximum H{sub 2} storage capacity that could be achieved in 2×2PG-8Li is 8.95 wt% which is higher than the U.S. DOE’s revised target for the on-board vehicles. The average H{sub 2} adsorption binding energy is 0.535 eV/H{sub 2}, which lies between 0.2-0.6 eV/H{sub 2} that is required for achieving adsorption and desorption at near ambient conditions. Thus, Li-decorated PG could be a viable option for on-board automobile applications.

  11. Physical Adsorption of Gases on Heterogeneous Solids and Equilibrium Studies of the Pressure Swing Adsorption Process.

    NASA Astrophysics Data System (ADS)

    Lu, Xiaochun

    1990-01-01

    Adsorption isotherms of ethane, propane, and n -butane on two polystyrene adsorbents and two activated carbons were measured at 0, 25, and 40^ circC. A dynamic chromatographic experimental system was used to measure the transmission curves of gases through a packed bed. The transmission is defined as the ratio of the adsorbate concentration at the bed outlet to that at the bed inlet. A mass-balance equation was used to calculate the solid-phase concentration and the dimensionless adsorption capacity. The structural and energetic heterogeneities of microporous adsorbents were explored by means of Dubinin's Theory of Volume Filling of Micropores (TVFM) and by a modified TVFM. The structural heterogeneity of a microporous adsorbent refers to the non-uniformity of the pore sizes and pore shapes. In polystyrene adsorbents, these non -uniform pores were formed by different copolymerization of monomers; while in activated carbons, these non-uniform pores were formed in the processes of carbonization and activation. The energetic heterogeneities of a microporous adsorbent comes from the structural heterogeneity as well as from the various atoms and functional groups exposed at the pore surface, the impurities strongly bound to the surface, and the irregularities in the crystallographical structure of the surface. Dubinin's original TVFM applies well in structurally homogeneous or weakly-heterogeneous microporous activated carbons; however, fits of experimental isotherms to the Dubinin-Radushkevich equation reveal deviations for structurally -heterogeneous adsorbents. We extended Dubinin's TVFM to the case of structurally-heterogeneous adsorbents by using an overall integral isotherm equation. A gamma-function type micropore-size distribution was used and a three-parameter isotherm equation was obtained. The experimental isotherms on activated carbons were fitted well by this isotherm equation. We characterized eight different activated carbons with the three

  12. Direct visual evidence of end-on adsorption geometry of pyridine on silver surface investigated by surface enhanced Raman scattering and density functional theory calculations.

    PubMed

    Bhunia, Snehasis; Forster, Stefan; Vyas, Nidhi; Schmitt, Hans-Christian; Ojha, Animesh K

    2015-12-01

    Fourier transform Raman (FT-Raman) spectra of neat pyridine (Py) and surface enhanced Raman scattering (SERS) spectra of Py with silver nanoparticles (AgNPs) solution at different molar concentrations (X=1.5M, 1.0M, 0.50 M, 0.25 M, and 0.125 M) were recorded using 1064 nm excitation wavelength. The intensity of Raman bands at ∼1003 (ν11) and ∼1035 (ν21) cm(-1) of Py is enhanced in the SERS spectra. Two new Raman bands were observed at ∼1009 (ν12) and ∼1038 (ν22) cm(-1) in the SERS spectra. These bands correspond to the ring breathing vibrations of Py molecules adsorbed at the AgNPs surface. The value of intensity ratios (I12/I11) and (I21/I22) is increased with dilution and attains a maximum value at X=0.5M and upon further dilution (0.25 and 0.125 M) it drops gradually. The theoretically calculated Raman spectra were found to be in good agreement with experimentally observed Raman spectra. Both, experimental and theoretical investigations have confirmed that the Py interacts with AgNPs via the end-on geometry. PMID:26184474

  13. Parametric study of a silica gel-water adsorption refrigeration cycle -- The influence of thermal capacitance and heat exchanger UA-values on cooling capacity, power density, and COP

    SciTech Connect

    Boelman, E.C.; Saha, B.B.; Kashiwagi, Takao

    1997-12-31

    The influence of heat exchanger UA-values (adsorber/desorber, evaporator, and condenser) is investigated for an adsorption chiller, with consideration given to the thermal capacitance of the adsorber/desorber by means of a lumped-parameter cycle simulation model developed by the authors and co-workers for the single-stage silica gel-water adsorption chiller. The closed-cycle-type chiller, for use in air conditioning, is driven by low-grade waste heat (85 C [185 F]) and cooled by water at 31 C (88 F) and operates on relatively short cycle times (420 seconds adsorption/desorption; 30 second adsorber/desorber sensible cooling and heating). The results showed cycle performance to be considerably affected by the thermal capacitance and UA-value of the adsorber/desorber, which is attributed to the severe sensible cooling/heating requirements resulting from batched cycle operation. The model is also sensitive to the evaporator UA-value--but to a lesser extent. The condenser UA-value is the least sensitive parameter due to the working pair adsorption behavior in the temperature range defined for desorption and condensation.

  14. ZK-5: a CO₂-selective zeolite with high working capacity at ambient temperature and pressure.

    PubMed

    Liu, Qingling; Pham, Trong; Porosoff, Marc D; Lobo, Raul F

    2012-11-01

    The increased carbon dioxide concentration in the atmosphere caused by combustion of fossil fuels has been a leading contributor to global climate change. The adsorption-driven pressure or vacuum swing (PSA/VSA) processes are promising as affordable means for the capture and separation of CO₂. Herein, an 8-membered-ring zeolite ZK-5 (Framework Type Code: KFI) exchanged with different cations (H⁺, Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺) was synthesized as novel CO₂ adsorbent. The samples were characterized by SEM, energy-dispersive X-ray spectroscopy (EDAX), XRD, and gas adsorption (CO₂ and N₂). The Toth adsorption model was used to describe the CO₂ adsorption isotherms, and the isosteric heats of adsorption were calculated. CO₂ capture adsorbent evaluation criteria such as working capacity, regenerability and CO₂/N₂ selectivity were applied to evaluate the zeolite adsorbents for PSA/VSA applications. The in situ FTIR CO₂ adsorption spectra show that physisorption accounts for the largest fraction of the total CO₂ adsorbed. The CO₂ adsorption analysis shows that Mg-ZK-5 is the most promising adsorbent for PSA applications with the highest working capacity (ΔN(CO₂)=2.05 mmol g⁻¹), excellent selectivity (α(CO₂/N₂)=121), and low isosteric heat. Li-, Na- and K-ZK-5 with good working capacity (ΔN(CO₂)=1.55-2.16 mmol g⁻¹) and excellent selectivity (α(CO₂/N₂)=103-128) are promising CO₂ adsorbents for the VSA working region. PMID:22907818

  15. Adsorption interactions of humic acids with biocides

    NASA Astrophysics Data System (ADS)

    Mal'Tseva, E. V.; Ivanov, A. A.; Yudina, N. V.

    2009-11-01

    The chemical composition of humic acids from brown coal (Aldrich) was determined by element analysis, 13C NMR spectroscopy, and potentiometric titration. The adsorption ability of humic acids with different biocides (cyproconasol, propiconasol, tebuconasol, irgarol 1051, and DCOIT) was studied. The adsorption ability of a mixture of biocides in aqueous solutions was higher than that of the individual components. The limiting concentration of humic acids at which adsorption of biocides was maximum was determined. Adsorption constants were calculated by the Freundlich equation for each biocide in aqueous solution.

  16. Novel sandwich structure adsorptive membranes for removal of 4-nitrotoluene from water.

    PubMed

    Guo, Yuexin; Jia, Zhiqian

    2016-11-01

    Novel sandwich PES-SPES/PS-PDVB/PTFE adsorptive membranes were prepared by a filtration/immersion precipitation method and employed for the removal of 4-nitrotoluene from water. The static adsorption thermodynamics, kinetics, dynamic adsorption/desorption and membrane reusability were investigated. The results showed that the Freundlich model describes the adsorption isotherm satisfactorily. With increased PS-PDVB content, the maximum static adsorption capacity, partition coefficient, apparent adsorption rate constant, and dynamic adsorption capacity all significantly increased. The sandwich membranes showed much higher removal efficiency and adsorption capacity than those of mixed matrix membranes. With respect to dynamics adsorption/desorption, the sandwich membranes exhibited excellent reusability, with a removal efficiency greater than 95% even after five recycles. PMID:27322899

  17. Fluorocarbon Adsorption in Hierarchical Porous Frameworks

    SciTech Connect

    Motkuri, Radha K.; Annapureddy, Harsha V.; Vijayakumar, M.; Schaef, Herbert T.; Martin, P F.; McGrail, B. Peter; Dang, Liem X.; Krishna, Rajamani; Thallapally, Praveen K.

    2014-07-09

    The adsorption behavior of a series of fluorocarbon derivatives was examined on a set of microporous metal organic framework (MOF) sorbents and another set of hierarchical mesoporous MOFs. The microporous M-DOBDC (M = Ni, Co) showed a saturation uptake capacity for R12 of over 4 mmol/g at a very low relative saturation pressure (P/Po) of 0.02. In contrast, the mesoporous MOF MIL-101 showed an exceptionally high uptake capacity reaching over 14 mmol/g at P/Po of 0.4. Adsorption affinity in terms of mass loading and isosteric heats of adsorption were found to generally correlate with the polarizability of the refrigerant with R12 > R22 > R13 > R14 > methane. These results suggest the possibility of exploiting MOFs for separation of azeotropic mixtures of fluorocarbons and use in eco-friendly fluorocarbon-based adsorption cooling and refrigeration applications.

  18. Volumetric interpretation of protein adsorption kinetics

    NASA Astrophysics Data System (ADS)

    Barnthip, Naris

    Protein adsorption is believed to be a very important factor ultimately leading to a predictive basis for biomaterials design and improving biocompatibility. Standard adsorption theories are modified to accommodate experimental observations. Adsorption from single-protein solutions and competitive adsorption from binary solutions are mainly considered. The standard solution-depletion method of measuring protein adsorption is implemented with SDS-gel electrophoresis as a multiplexing, separation-and-quantification tool to measure protein adsorption to hydrophobic octyl sepharose (OS) adsorbent particles. Standard radiometric methods have also been used as a further check on the electrophoresis method mentioned above for purified-protein cases. Experimental results are interpreted in terms of an alternative kinetic model called volumetric interpretation of protein adsorption. A partitioning process between bulk solution and a three-dimensional interphase region that separates bulk solution from the physical adsorbent surface is the concept of the model. Protein molecules rapidly diffuse into an inflating interphase that is spontaneously formed by bringing a protein solution into contact with a physical surface, then follows by rearrangement of proteins within this interphase to achieve the maximum interphase concentration (dictated by energetics of interphase dehydration) within the thinnest (lowest volume) interphase possible. An important role of water in protein adsorption is emphasized and supported by this model. The fundamental aspects including the reversibility/irreversibility of protein adsorption, the multilayer adsorption, the applicability of thermodynamic/computational models, the capacity of protein adsorption, and the mechanism of so called Vroman effect are discussed and compared to the conventional theories. Superhydrophobic effect on the adsorption of human serum albumin is also examined.

  19. Phosphate adsorption on aluminum-coordinated functionalized macroporous–mesoporous silica: Surface structure and adsorption behavior

    SciTech Connect

    Huang, Weiya; Li, Dan; Zhu, Yi; Xu, Kai; Li, Jianqiang; Han, Boping; Zhang, Yuanming

    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%.

  20. Fabrication of hybrid magnetic Sr5xBa3x(PO4)3(OH)/Fe3O4 nanorod and its highly efficient adsorption performance for acid fuchsin dye

    NASA Astrophysics Data System (ADS)

    Yin, Xiaoju; Zhang, Fan; Zhang, Weihua

    2015-12-01

    The hybrid magnetic Sr5xBa3x(PO4)3(OH)/Fe3O4 (SBPF) nanorod was prepared and characterized using different techniques, such as SEM, EDS, TEM, SAED, HRTEM, XRD, and FT-IR. Adsorption studies of acid fuchsin (AF) from aqueous solution with respect to the pH, temperature, time, initial dye concentration, and sorbent dosage were investigated. The Freundlich adsorption model was applied to describe the equilibrium isotherms. The maximal AF uptake by SBPF was 1590 mg/g in the test. Kinetics parameters of the adsorption process indicated that it followed the pseudo-second order equation, and the maximum sorption capacity calculated from the pseudo-second-order rate equation was 909 mg/g which was close to the experimental value. Adsorption thermodynamics study indicated the spontaneous nature and exothermic of the adsorption process. The removal of AF was attributed to the hydrogen bond and ionic interactions. Moreover, SBPF was easily recovered, and the adsorption capacity was approximately 97.7% of the initial saturation adsorption capacity after being used five times.

  1. Analysis of the heat capacity for pure CH4 and CH4/CCl4 on graphite near the melting point and calculation of the T-X phase diagram for (CH3)CCl3 + CCl4

    NASA Astrophysics Data System (ADS)

    Yurtseven, Hamit; Yılmaz, Aygül

    2016-06-01

    We study the temperature dependence of the heat capacity Cp for the pure CH4 and the coadsorbed CH4/CCl4 on graphite near the melting point. The heat capacity peaks are analyzed using the experimental data from the literature by means of the power-law formula. The critical exponents for the heat capacity are deduced below and above the melting point for CH4 (Tm = 104.8 K) and CH4/CCl4 (Tm = 99.2 K). Our exponent values are larger as compared with the predicted values of some theoretical models exhibiting second order transition. Our analyses indicate that the pure methane shows a nearly second order (weak discontinuity in the heat capacity peak), whereas the transition in coadsorbed CH4/CCl4 is of first order (apparent discontinuity in Cp). We also study the T – X phase diagram of a two-component system of CH3CCl3+CCl4 using the Landau phenomenological model. Phase lines of the R+L (rhombohedral+liquid) and FCC+L (face-centred cubic + liquid) are calculated using the observed T – X phase diagram of this binary mixture. Our results show that the Landau mean field theory describes the observed behavior of CH3CCl3+CCl4 adequately. From the calculated T – X phase diagram, critical behavior of some thermodynamic quantities can be predicted at various temperatures and concentrations (CCl4) for a binary mixture of CH3CCl3+CCl4.

  2. Kinetic and thermodynamic studies of sulforaphane adsorption on macroporous resin.

    PubMed

    Yuanfeng, Wu; Lei, Zhang; Jianwei, Mao; Shiwang, Liu; Jun, Huang; Yuru, You; Lehe, Mei

    2016-08-15

    The adsorption equilibrium, kinetic and thermodynamic of sulforaphane (SF) adsorption onto macroporous resin in aqueous phase were studied. The SP850 resin was screened as the appropriate resin for SF purification. From the equilibrium studies, the Redlich-Peterson model was found to be the best for description of the adsorption behavior of SF onto SP850 resin, followed by the Freundlich model and the Langmuir model. Batch equilibrium experiments demonstrated that, in the examined temperature range, the equilibrium adsorption capacity of SP850 resin decreased with increasing adsorption temperature. Thermodynamics studies indicated that the adsorption of SF was a physical, exothermic, and spontaneous process. The adsorption kinetics revealed that the pseudo-second-order kinetic model was suitable to characterize the kinetics of adsorption of SF onto SP850. Finally, the intra-particle diffusion model demonstrated that SF diffused quickly into macropores, and that diffusion slowed down in the meso- and micropores. PMID:27391585

  3. Hydrogen Adsorption on Activated Carbon an Carbon Nanotubes Using Volumetric Differential Pressure Technique

    SciTech Connect

    Sanip, S. M.; Saidin, M. A. R.; Aziz, M.; Ismail, A. F.

    2010-03-11

    A simple hydrogen adsorption measurement system utilizing the volumetric differential pressure technique has been designed, fabricated and calibrated. Hydrogen adsorption measurements have been carried out at temperatures 298 K and 77 K on activate carbon and carbon nanotubes with different surface areas. The adsorption data obtained will be helpful in understanding the adsorption property of the studied carbon materials using the fundamentals of adsorption theory. The principle of the system follows the Sievert-type method. The system measures a change in pressure between the reference cell, R1 and the sample cell S1, S2, S3 over a certain temperature range, R1, S1, S2, and S3 having known fixed volume. The sample temperatures will be monitored by thermocouple TC while the pressures in R1 an S1, S2, S3 will be measured using a digital pressure transducer. The maximum operating pressure of the pressure transducer is 20 bar and calibrated with an accuracy of +-0.01 bar. High purity hydrogen is being used in the system and the amount of samples for the study is between 1.0-2.0 grams. The system was calibrated using helium gas without any samples in S1, S2 an S3. This will provide a correction factor during the adsorption process providing an adsorption free reference point when using hydrogen gas resulting in a more accurate reading of the adsorption process by eliminating the errors caused by temperature expansion effects and other non-adsorption related phenomena. The ideal gas equation of state is applied to calculate the hydrogen adsorption capacity based on the differential pressure measurements. Activated carbon with a surface area of 644.87 m{sup 2}/g showed a larger amount of adsorption as compared to multiwalled nanotubes (commercial) with a surface area of 119.68 m{sup 2}/g. This study als indicated that there is a direct correlation between the amounts of hydrogen adsorbed an surface area of the carbon materials under the conditions studied and that the

  4. Competitive adsorption of heavy metals onto sesame straw biochar in aqueous solutions.

    PubMed

    Park, Jong-Hwan; Ok, Yong Sik; Kim, Seong-Heon; Cho, Ju-Sik; Heo, Jong-Soo; Delaune, Ronald D; Seo, Dong-Cheol

    2016-01-01

    Objective of this research was to evaluate adsorption of heavy metals in mono and multimetal forms onto sesame straw biochar (SSB). Competitive sorption of metals by SSB has never been reported previously. The maximum adsorption capacities (mgg(-1)) of metals by SSB were in the order of Pb (102)≫Cd (86)≫Cr (65)>Cu (55)≫Zn (34) in the monometal adsorption isotherm and Pb (88)≫Cu (40)≫Cr (21)>Zn (7)⩾Cd (5) in the multimetal adsorption isotherm. Based on data obtained from the distribution coefficients, Freundlich and Langmuir adsorption models, and three-dimensional simulation, multimetal adsorption behaviors differed from monometal adsorption due to competition. Especially, during multimetal adsorption, Cd was easily exchanged and substituted by other metals. Further competitive adsorption studies are necessary in order to accurately estimate the heavy metal adsorption capacity of biochar in natural environments. PMID:26082184

  5. Kinetic study of aluminum adsorption by aluminosilicate clay minerals

    SciTech Connect

    Walker, W.J.; Cronan, C.S.; Patterson, H.H.

    1988-01-01

    The adsorption kinetics of Al/sup 3 +/ by montmorillonite, kaolinite, and vermiculite were investigated as a function of the initial Al concentration, the surface area of the clay, and H/sup +/ concentration, at 25/sup 0/, 18/sup 0/, and 10/sup 0/C. In order to minimize complicated side reactions the pH range was kept between 3.0 and 4.1. Results showed that the adsorption rate was first order with respect to both the initial Al concentration and the clay surface area. Changes in pH within this narrow range had virtually no effect on adsorption rate. This zero order reaction dependence suggested that the H/sup +/, compared to Al, has a weak affinity for the surface. The rates of adsorption decreased in the order of montmorillonite > kaolinite > vermiculite when compared on the basis of equal surface areas, but changed to kaolinite > montmorillonite > vermiculite when the clays were compared on an equal exchange capacity basis. The calculated apparent activation energies were < 32 kJ mol/sup -1/, indicating that over the temperature range of the study the adsorption process is only marginally temperature sensitive. The mechanism is governed by a simple electrostatic cation exchange involving outer sphere complexes between adsorbed Al and the clay surface. Vermiculite, may have a second reaction step governed by both electrostatic attraction and internal ion diffusion. Equilibrium constants for the formation of an adsorbed Al clay complex were also estimated and are 10/sup 5.34/, 10/sup 5.18/, and 10/sup 4.94/ for kaolinite, montmorillonite, and vermiculite, respectively, suggesting that these clays could play a significant role in controlling soil solutions Al concentrations.

  6. Adsorption Isotherms and Surface Reaction Kinetics

    ERIC Educational Resources Information Center

    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)

  7. Preparation and characterization of chitosan/graphene oxide composites for the adsorption of Au(III) and Pd(II).

    PubMed

    Liu, Li; Li, Cui; Bao, Changli; Jia, Qiong; Xiao, Pengfei; Liu, Xiaoting; Zhang, Qiuping

    2012-05-15

    In this work, graphene oxide (GO) was firstly prepared, following by element analysis. Glutaraldehyde cross-linked chitosan (GCCS) and chitosan/graphene oxide (CSGO) composite with three different amounts of GO (5 wt%, 10 wt% and 15 wt%) were also prepared for the adsorption of Au(III) and Pd(II) in aqueous solution. The properties of the adsorbents were investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and surface area analysis. Batch adsorption studies were carried out. The adsorption of Au(III) and Pd(II) onto CSGO composites was optimum at pH 3.0-5.0 for Au(III) and pH 3.0-4.0 for Pd(II), which was much wider than that of GCCS. The adsorption isotherms obeyed the Langmuir isotherm models for the adsorption of Au(III) and Pd(II). Chitosan with 5 wt% graphene oxide (CSGO(5)) composite had the largest adsorption capacity for Au(III) and Pd(II) compared with the other prepared adsorbents, where the maximum adsorption capacity were 1076.649 mg/g for Au(III) and 216.920 mg/g for Pd(II), respectively. The adsorption kinetics of Au(III) and Pd(II) onto CSGO(5) followed a pseudo-second-order kinetic model, indicating that the chemical adsorption was the rate-limiting step. Thermodynamic parameters, such as Gibbs energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°), were calculated, showing that the adsorption of Au(III) and Pd(II) onto CSGO(5) were spontaneous, endothermic and feasible. The desorption studies of Au(III) and Pd(II) onto CSGO(5) showed that CSGO(5) can be used repeatedly without significantly changing its adsorption capacity and desorption percentage after 3 cycles. Besides CSGO(5) was successfully applied for the determination and separation of Au(III) and Pd(II) in ore samples. PMID:22483922

  8. Carbon monoxide adsorption on beryllium surfaces

    NASA Astrophysics Data System (ADS)

    Allouche, A.

    2013-02-01

    Density functional calculations are here carried out to study the carbon monoxide molecule adsorption on pristine, hydrogenated and hydroxylated beryllium Be (0001) surfaces. The adsorption energies and structures, the activation barriers to molecular adsorption and dissociation are calculated. These reactions are described in terms of potential energy surfaces and electronic density of states. The quantum results are discussed along two directions: the beryllium surface reactivity in the domain of nuclear fusion devices and the possible usage of beryllium as a catalyst of Fischer-Tropsch-type synthesis.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Thermodynamical and structural insights of orange II adsorption by Mg{sub R}AlNO{sub 3} layered double hydroxides

    SciTech Connect

    Mustapha Bouhent, Mohamed; Derriche, Zoubir; Denoyel, Renaud; Prevot, Vanessa; Forano, Claude

    2011-05-15

    [Mg{sub 1-x} Al{sub x}(OH){sub 2}][(NO{sub 3}){sub x}, nH{sub 2}O] 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. Mg{sub 2}AlNO{sub 3} displays the highest adsorption capacity with 3.611 mmol of OII per gram of Mg{sub 2}AlNO{sub 3} at 40 {sup o}C. Adsorption isotherms have been fitted using the Langmuir model and free energy of adsorption ({Delta}G{sup o}), enthalpy ({Delta}H{sup o}) and entropy ({Delta}S{sup o}) were calculated. The experimental values for {Delta}G{sup o} in temperature range between 10 and 40 {sup o}C 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 Mg{sub R}Al LDH Display Omitted Highlights: {yields} The nitrate containing hydrotalcite-like compounds (Mg{sub R}AlNO{sub 3} LDH) were prepared by the coprecipitation method. {yields} Adsorption of anionic orange dye(OII) is studied on LDHs at different temperatures. {yields} The adsorption process is well described by the Langmuir isotherm model. {yields} Mg{sub 2}AlNO{sub 3} displays the highest adsorption capacity with 3.611 mmol of OII per gram of Mg{sub 2}AlNO{sub 3} at 40 {sup o}C. {yields} 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.

  11. DFT study of Hg adsorption on M-substituted Pd(1 1 1) and PdM/γ-Al2O3(1 1 0) (M = Au, Ag, Cu) surfaces

    NASA Astrophysics Data System (ADS)

    Wang, Jiancheng; Yu, Huafeng; Geng, Lu; Liu, Jianwen; Han, Lina; Chang, Liping; Feng, Gang; Ling, Lixia

    2015-11-01

    The adsorption of Hgn (n = 1-3) on the Au-, Ag-, Cu-substituted Pd(1 1 1) surfaces as well as the PdM/γ-Al2O3(1 1 0) (M = Au, Ag, Cu) surfaces has been investigated using spin-polarized density functional theory calculations. It is found that M-substituted Pd(1 1 1) surfaces show as good Hg adsorption capacity as the perfect Pd(1 1 1) at low Hg coverage, while the Hg adsorption capacity is only slightly weakened at high Hg coverage. On the basis of stepwise adsorption energies analysis, it is concluded that M-substituted Pd(1 1 1) surfaces can contribute to the binding of Hg atom on the surfaces at high Hg coverage. The electronic properties of the second metal atoms are the main factor contributes to the Hg adsorption capacity. Gas phase Pd2 shows better Hg adsorption capacity than Pd2/γ-Al2O3, while PdM/γ-Al2O3 can adsorb Hg more efficiently than bare PdM clusters. It suggests that the γ-Al2O3 support can enhance the activity of PdM for Hg adsorption and reduces the activity of Pd2. It is also found that Pd is the main active composition responsible for the interaction of mercury with the surface for PdM/γ-Al2O3 sorbent. Taking Hg adsorption capacity and economic costs into account, Cu addition is a comparatively good candidate for Hg capture.

  12. Defect-Mediated Lithium Adsorption and Diffusion on Monolayer Molybdenum Disulfide.

    PubMed

    Sun, Xiaoli; Wang, Zhiguo; Fu, Y Q

    2015-01-01

    Monolayer Molybdenum Disulfide (MoS2) is a promising anode material for lithium ion batteries because of its high capacities. In this work, first principle calculations based on spin density functional theory were performed to investigate adsorption and diffusion of lithium on monolayer MoS2 with defects, such as single- and few-atom vacancies, antisite, and grain boundary. The values of adsorption energies on the monolayer MoS2 with the defects were increased compared to those on the pristine MoS2. The presence of defects causes that the Li is strongly bound to the monolayer MoS2 with adsorption energies in the range between 2.81 and 3.80 eV. The donation of Li 2s electron to the defects causes an enhancement of adsorption of Li on the monolayer MoS2. At the same time, the presence of defects does not apparently affect the diffusion of Li, and the energy barriers are in the range of 0.25-0.42 eV. The presence of the defects can enhance the energy storage capacity, suggesting that the monolayer MoS2 with defects is a suitable anode material for the Li-ion batteries. PMID:26692345

  13. Defect-Mediated Lithium Adsorption and Diffusion on Monolayer Molybdenum Disulfide

    PubMed Central

    Sun, Xiaoli; Wang, Zhiguo; Fu, Y. Q.

    2015-01-01

    Monolayer Molybdenum Disulfide (MoS2) is a promising anode material for lithium ion batteries because of its high capacities. In this work, first principle calculations based on spin density functional theory were performed to investigate adsorption and diffusion of lithium on monolayer MoS2 with defects, such as single- and few-atom vacancies, antisite, and grain boundary. The values of adsorption energies on the monolayer MoS2 with the defects were increased compared to those on the pristine MoS2. The presence of defects causes that the Li is strongly bound to the monolayer MoS2 with adsorption energies in the range between 2.81 and 3.80 eV. The donation of Li 2s electron to the defects causes an enhancement of adsorption of Li on the monolayer MoS2. At the same time, the presence of defects does not apparently affect the diffusion of Li, and the energy barriers are in the range of 0.25–0.42 eV. The presence of the defects can enhance the energy storage capacity, suggesting that the monolayer MoS2 with defects is a suitable anode material for the Li-ion batteries. PMID:26692345

  14. Defect-Mediated Lithium Adsorption and Diffusion on Monolayer Molybdenum Disulfide

    NASA Astrophysics Data System (ADS)

    Sun, Xiaoli; Wang, Zhiguo; Fu, Y. Q.

    2015-12-01

    Monolayer Molybdenum Disulfide (MoS2) is a promising anode material for lithium ion batteries because of its high capacities. In this work, first principle calculations based on spin density functional theory were performed to investigate adsorption and diffusion of lithium on monolayer MoS2 with defects, such as single- and few-atom vacancies, antisite, and grain boundary. The values of adsorption energies on the monolayer MoS2 with the defects were increased compared to those on the pristine MoS2. The presence of defects causes that the Li is strongly bound to the monolayer MoS2 with adsorption energies in the range between 2.81 and 3.80 eV. The donation of Li 2s electron to the defects causes an enhancement of adsorption of Li on the monolayer MoS2. At the same time, the presence of defects does not apparently affect the diffusion of Li, and the energy barriers are in the range of 0.25-0.42 eV. The presence of the defects can enhance the energy storage capacity, suggesting that the monolayer MoS2 with defects is a suitable anode material for the Li-ion batteries.

  15. Dye adsorption and bactericidal properties of TiO2/chitosan coating layer.

    PubMed

    Kamal, Tahseen; Anwar, Yasir; Khan, Sher Bahadar; Chani, Muhammad Tariq Saeed; Asiri, Abdullah M

    2016-09-01

    A new kind of titanium oxide dispersed in chitosan (TiO2/CS) nanocomposite adsorbent was prepared and adhered to high surface area substrate, cellulose microfibers mat (CMM). CS-CMM and TiO2/CS-CMM were used for the thymol violet (TV) dye removal from wastewater. Characterization of materials was carried out by X-ray diffraction, scanning electron microscope and energy dispersive X-ray spectroscopy. The adsorption properties of both the CS-CMM and TiO2/CS-CMM were investigated as a function of adsorbent dosage, solution pH, and contact time. It was revealed that the composites pretreated in the solution with higher pH value exhibited larger adsorption capacities. Kinetic studies showed that the composites could adsorb TV dye rapidly and reached the equilibrium in 90min. The adsorption process followed pseudo-second order kinetics and involved particle diffusion mechanism. The calculated maximum adsorption capacities of CS-CMM and TiO2/CS-CMM were 84.32 and 97.51mgg(-1), respectively. Compare to CS, the TiO2/CS nanocomposite coated CMM showed higher antibacterial characteristics as tested against Escherichia coli. PMID:27185126

  16. Mechanism of Arsenic Adsorption on Magnetite Nanoparticles from Water: Thermodynamic and Spectroscopic Studies.

    PubMed

    Liu, Cheng-Hua; Chuang, Ya-Hui; Chen, Tsan-Yao; Tian, Yuan; Li, Hui; Wang, Ming-Kuang; Zhang, Wei

    2015-07-01

    Removal of arsenic (As) from water supplies is needed to reduce As exposure through drinking water and food consumption in many regions of the world. Magnetite nanoparticles (MNPs) are promising and novel adsorbents for As removal because of their great adsorption capacity for As and easy separation. This study aimed to investigate the adsorption mechanism of arsenate, As(V), and arsenite, As(III), on MNPs by macroscopic adsorption experiments in combination with thermodynamic calculation and microspectroscopic characterization using synchrotron-radiation-based X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS). Adsorption reactions are favorable endothermic processes as evidenced by increased adsorption with increasing temperatures, and high positive enthalpy change. EXAFS spectra suggested predominant formation of bidentate binuclear corner-sharing complexes ((2)C) for As(V), and tridentate hexanuclear corner-sharing ((3)C) complexes for As(III) on MNP surfaces. The macroscopic and microscopic data conclusively identified the formation of inner-sphere complexes between As and MNP surfaces. More intriguingly, XANES and XPS results revealed complex redox transformation of the adsorbed As on MNPs exposed to air: Concomitant with the oxidation of MNPs, the oxidation of As(III) and MNPs was expected, but the observed As(V) reduction was surprising because of the role played by the reactive Fe(II). PMID:26055623

  17. Relationship between bond stiffness and electrical energy storage capacity in oxides: density functional calculations for h-La2O3, MgO and BeO

    SciTech Connect

    Xu, Bo; Cooper, Valentino R; Singh, David J; Feng, Yuan Ping

    2011-01-01

    We report finite electric field calculations for three representative oxide dielectrics: MgO, La{sub 2}O{sub 3}, and BeO. These materials have very different dielectric constants and bond stiffness. Good accord with experimental low field data is obtained. We discuss the results from the point of view of dielectric energy storage and suggest that the low dielectric constant, high bond stiffness material BeO is best from the viewpoint of energy density.

  18. Equilibrium, kinetic and thermodynamic studies on the adsorption of phenol onto graphene

    SciTech Connect

    Li, Yanhui; Du, Qiuju; Liu, Tonghao; Sun, Jiankun; Jiao, Yuqin; Xia, Yanzhi; Xia, Linhua; Wang, Zonghua; Zhang, Wei; Wang, Kunlin; Zhu, Hongwei; Wu, Dehai

    2012-08-15

    Graphical abstract: The effect of temperature on phenol adsorbed by graphene shows that the equilibrium adsorption capacity of phenol increases with the increase in temperature from 285 to 333 K. Increasing adsorption capacities with temperature indicates that the adsorption of phenol is controlled by an endothermic reaction. Highlights: ► The graphene has high phenol adsorption capacity. ► The graphene has a high specific surface area of 305 m{sup 2}/g. ► The adsorption capacity is high at acidic pH range. ► The graphene has rapid phenol adsorption rate. ► Phenol adsorption is a spontaneous and endothermic process. -- Abstract: Graphene, a new member of carbon family, has been prepared, characterized and used as adsorbent to remove phenol from aqueous solution. The effect parameters including pH, dosage, contact time, and temperature on the adsorption properties of phenol onto graphene were investigated. The results showed that the maximum adsorption capacity can reach 28.26 mg/g at the conditions of initial phenol concentration of 50 mg/L, pH 6.3 and 285 K. Adsorption data were well described by both Freundlich and Langmuir models. The kinetic study illustrated that the adsorption of phenol onto graphene fit the pseudo second-order model. The thermodynamic parameters indicated that the adsorption of phenol onto graphene was endothermic and spontaneous.

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

    PubMed

    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

  20. Density Functional Theory Study of Hydrogen Adsorption in a Ti-Decorated Mg-Based Metal-Organic Framework-74.

    PubMed

    Suksaengrat, Pitphichaya; Amornkitbamrung, Vittaya; Srepusharawoot, Pornjuk; Ahuja, Rajeev

    2016-03-16

    The Ti-binding energy and hydrogen adsorption energy of a Ti-decorated Mg-based metal-organic framework-74 (Mg-MOF-74) were evaluated by using first-principles calculations. Our results revealed that only three Ti adsorption sites were found to be stable. The adsorption site near the metal oxide unit is the most stable. To investigate the hydrogen-adsorption properties of Ti-functionalized Mg-MOF-74, the hydrogen-binding energy was determined. For the most stable Ti adsorption site, we found that the hydrogen adsorption energy ranged from 0.26 to 0.48 eV H2 (-1) . This is within the desirable range for practical hydrogen-storage applications. Moreover, the hydrogen capacity was determined by using ab initio molecular dynamics simulations. Our results revealed that the hydrogen uptake by Ti-decorated Mg-MOF-74 at temperatures of 77, 150, and 298 K and ambient pressure were 1.81, 1.74, and 1.29 H2  wt %, respectively. PMID:26717417

  1. Preparation and Characterization of Chitosan/Feldspar Biohybrid as an Adsorbent: Optimization of Adsorption Process via Response Surface Modeling

    PubMed Central

    Yazdani, Maryam; Bahrami, Hajir; Arami, Mokhtar

    2014-01-01

    Chitosan/feldspar biobased beads were synthesized, characterized, and tested for the removal of Acid Black 1 dye from aquatic phases. A four-factor central composite design (CCD) accompanied by response surface modeling (RSM) and optimization was used to optimize the dye adsorption by the adsorbent (chitosan/feldspar composite) in 31 different batch experiments. Independent variables of temperature, pH, initial dye concentration, and adsorbent dose were used to change to coded values. To anticipate the responses, a quadratic model was applied. Analysis of variance (ANOVA) tested the significance of the process factors and their interactions. The adequacy of the model was investigated by the correlation between experimental and predicted data of the adsorption and the calculation of prediction errors. The results showed that the predicted maximum adsorption amount of 21.63 mg/g under the optimum conditions (pH 3, temperature 15°C, initial dye concentration 125 mg/L, and dose 0.2 g/50 mL) was close to the experimental value of 19.85 mg/g. In addition, the results of adsorption behaviors of the dye illustrated that the adsorption process followed the Langmuir isotherm model and the pseudo-second-order kinetic model. Langmuir sorption capacity was found to be 17.86 mg/g. Besides, thermodynamic parameters were evaluated and revealed that the adsorption process was exothermic and favourable. PMID:24587722

  2. First-principles vdW-DF study on the enhanced hydrogen storage capacity of Pt-adsorbed graphene.

    PubMed

    Khosravi, Azadeh; Fereidoon, Abdolhosein; Ahangari, Morteza Ghorbanzadeh; Ganji, Masoud Darvish; Emami, Seyede Negar

    2014-05-01

    Ab initio vdW calculations with the DFT level of theory were used to investigate hydrogen (H₂) adsorption on Pt-adsorbed graphene (Pt-graphene). We have explored the most energetically favorable sites for single Pt atom adsorption on the graphene surface. The interaction of H₂ with the energetically favorable Pt-graphene system was then investigated. We found that H₂ physisorbs on pristine graphene with a binding energy of -0.05 eV, while the binding energy is enhanced to -1.98 eV when H₂ binds Pt-adsorbed graphene. We also found that up to four H₂ molecules can be adsorbed on the Pt-graphene system with a -0.74 eV/H₂ binding energy. The effect of graphene layer stretching on the Pt-graphene capacity/ability for hydrogen adsorption was evaluated. Our results show that the number of H₂ molecules adsorbed on the Pt-graphene surface rises to six molecules with a binding energy of approximately -0.29 eV/H₂. Our first-principles results reveal that the Young's modulus was slightly decreased for Pt adsorption on the graphene layer. The first-principles calculated Young's modulus for the H₂-adsorbed Pt-graphene system demonstrates that hydrogen adsorption can dramatically increase the Young's modulus of such systems. As a result, hydrogen adsorption on the Pt-graphene system might enhance the substrate strength. PMID:24777315

  3. Mechanism of highly efficient adsorption of 2-chlorophenol onto ultrasonic graphene materials: Comparison and equilibrium.

    PubMed

    Soltani, Tayyebeh; Lee, Byeong-Kyu

    2016-11-01

    The deficiencies of the recently reported improved Hummers method for the synthesis of graphene oxide (GO), such as high reaction temperature (60°C) and long reaction time (10h), were successfully solved using a low-intensity ultrasonic bath for 30min at 40°C. Furthermore, compared to its conventional synthesis counterpart, a facile and fast, one-step ultrasonic method that excluded hydrazine hydrate was developed to synthesize reduced GO (rGO) from graphite (10min, 50°C) in the presence of hydrazine hydrate (rGO-C, 12h, 90°C). The adsorption characteristics of 2-chlorophenol (2-CP) from an aqueous solution were investigated using rGOs and GOs prepared by ultrasonic (rGO-Us/GO-Us) and conventional (rGO-C/GO-C) methods. Whereas 2-CP was completely removed with rGO-Us after 50min, only 40% of 2-CP was eliminated with rGO-C. The maximum adsorption capacity of 2-CP calculated by the Langmuir model onto rGO-Us (208.67mg/g) was much higher than that onto GO-Us (134.49mg/g). In addition, the ultrasonic graphene adsorption capacities were much higher than the corresponding values of rGO-C (49.9mg/g) and GO-C (32.06mg/g). The enhanced adsorption for rGO-Us and GO-Us is attributed to their greater surface areas, excellent oxygenated groups for GO-Us and superior π-electron-rich matrix for rGO-Us, compared to other adsorbents. The adsorption of 2-CP on the rGO materials increased with increasing solution pH to a maximum around its pKa (pKa=8.85), while the adsorption for the GO materials increased with decreasing solution pH. The adsorption mechanism proceeded via hydrogen bonding in neutral and acidic media, but via π-π electron donor-accepter (EDA) interactions between 2-CP and graphene materials in basic medium. The FTIR spectrum of GO-Us after adsorption indicates that the position and intensity of many peaks of GO-Us were affected due to the adsorption of different 2-CP groups at different pHs. PMID:27474817

  4. Adsorption coefficients for TNT on soil and clay minerals

    NASA Astrophysics Data System (ADS)

    Rivera, Rosángela; Pabón, Julissa; Pérez, Omarie; Muñoz, Miguel A.; Mina, Nairmen

    2007-04-01

    To understand the fate and transport mechanisms of TNT from buried landmines is it essential to determine the adsorption process of TNT on soil and clay minerals. In this research, soil samples from horizons Ap and A from Jobos Series at Isabela, Puerto Rico were studied. The clay fractions were separated from the other soil components by centrifugation. Using the hydrometer method the particle size distribution for the soil horizons was obtained. Physical and chemical characterization studies such as cation exchange capacity (CEC), surface area, percent of organic matter and pH were performed for the soil and clay samples. A complete mineralogical characterization of clay fractions using X-ray diffraction analysis reveals the presence of kaolinite, goethite, hematite, gibbsite and quartz. In order to obtain adsorption coefficients (K d values) for the TNT-soil and TNT-clay interactions high performance liquid chromatography (HPLC) was used. The adsorption process for TNT-soil was described by the Langmuir model. A higher adsorption was observed in the Ap horizon. The Freundlich model described the adsorption process for TNT-clay interactions. The affinity and relative adsorption capacity of the clay for TNT were higher in the A horizon. These results suggest that adsorption by soil organic matter predominates over adsorption on clay minerals when significant soil organic matter content is present. It was found that, properties like cation exchange capacity and surface area are important factors in the adsorption of clayey soils.

  5. Calculation of permissible load capacity and establishment of total amount control in the Wujin River Catchment--a tributary of Taihu Lake, China.

    PubMed

    Zhang, Ruibin; Gao, Hailong; Zhu, Wenting; Hu, Wei; Ye, Rui

    2015-08-01

    The deterioration of water quality in Taihu Lake, China, has caused widespread concern in recent years. The primary pollution sources of Taihu Lake are its inflow rivers. Effective environmental water management strategies need to be implemented in these rivers to improve the water quality of Taihu Lake and to promote sustainable development in the region. In this study, the QUAL2K model is used in conjunction with the trial and error approach to assess permissible load capacities for the Wujin River (a major tributary of Taihu Lake) in terms of COD, NH3-N, TN, and TP. Results show that permissible annual loads for these pollutants are 5216.31, 491.71, 948.53, and 104.38 t, respectively. This suggests that COD, NH3-N, TN, and TP loads in the Wujin River catchment need to be reduced by 13.35, 27.26, 47.75, and 37.08 %, respectively, to satisfy national water quality objectives. Total amount control measures are proposed to control and reduce pollution loads of the Wujin River catchment. The method applied in this study should provide a sound basis for water environmental management decision-making. PMID:25822841

  6. EFFECT OF GAC CHARACTERISTICS ON ADSORPTION OF ORGANIC POLLUTANTS

    EPA Science Inventory

    The impact of the characteristics of granular activated carbon (GAC) on adsorption capacity and on the potential for polymerization of phenolic compounds on the surface of GAC in the presence of molecular oxygen is evaluated in this study. Adsorption isotherm data were collected...

  7. Study of Adsorption of Copper Species onto Multiwall Carbon Nanotubes

    EPA Science Inventory

    Functionalized CNTs have improved adsorptive capacities over pristine CNTs. These can be used for sensors, membranes, filters and matrix composite enhancements made possible because of their nano-size.

  8. Impact of carbon nanotube morphology on phenanthrene adsorption.

    PubMed

    Apul, Onur Guven; Shao, Ting; Zhang, Shujuan; Karanfil, Tanju

    2012-01-01

    The present study examined the roles of the specific surface area (SSA), diameter, and length of carbon nanotubes (CNT) on the adsorption of phenanthrene (PNT) by analyzing the adsorption isotherms obtained with several single-walled carbon nanotubes (SWNT) and multiwalled carbon nanotubes (MWNT). At low equilibrium concentrations (e.g., 1 ppb), MWNTs with larger outer diameters exhibited higher PNT adsorption capacity on an SSA basis than those with smaller diameters. With increasing equilibrium concentration, adsorption on an SSA basis became independent of MWNT diameter, and the total surface area controlled maximum adsorption capacity. A similar analysis for the adsorption of naphthalene, a planar molecule with one less benzene ring but 20 times higher solubility than PNT, showed no correlation with respect to MWNT outer diameter. The results indicated that the surface curvature of MWNT was more important on the adsorption of PNT than on the adsorption of naphthalene. Specific surface area normalized isotherms did not show a correlation between PNT adsorption and lengths of SWNTs and MWNTs. Characterization results indicated that the morphology of CNTs plays an important role on the SSA and pore volume. Data from the manufacturer may not always represent the characteristics of CNTs in a particular batch. Therefore, accurate characterization of CNTs is critical to systematically examine the behavior of CNTs, such as adsorption and transport, in environmental systems. PMID:22002628

  9. Multicarboxylic hyperbranched polyglycerol modified SBA-15 for the adsorption of cationic dyes and copper ions from aqueous media

    NASA Astrophysics Data System (ADS)

    Chen, Zhengji; Zhou, Li; Zhang, Faai; Yu, Chuanbai; Wei, Zhibo

    2012-04-01

    The aim of the present work was to investigate the potential of multicarboxylic hyperbranched polyglycerol (HPG) modified mesoporous SBA-15 (SBA/HPG-COOH) as adsorbent for the removal of cationic dyes or/and heavy metal ions from aqueous media. The SBA/HPG-COOH adsorbents can be facilely synthesized through two steps: in situ anionic ring-opening polymerization of glycidol and further modification of hydroxyl groups by succinic anhydride. The resulting SBA/HPG-COOH was characterized by means of FTIR, TGA, XRD, SEM and nitrogen adsorption-desorption isotherms. The results demonstrate that the SBA/HPG-COOH was successfully synthesized and the density of carboxylic groups on the SBA/HPG-COOH is calculated to be as high as 1.5 mmol/g, posing a powerful base for adsorbing cationic adsorbates. Four kinds of dyes and copper ions were chosen as representatives to investigate the adsorption ability of SBA/HPG-COOH. The SBA/HPG-COOH adsorbent showed quick adsorption rate, high adsorption capacity (e.g., its saturated adsorption capacity for methylene blue (MB) can reach 0.50 mmol/g, while for unmodified SBA-15 is lower than 0.05 mmol/g), and high selectivity for cationic adsorbates. The fitness of Langmuir adsorption model and pseudo second-order kinetics on describing the adsorption isotherm and kinetics of SBA/HPG-COOH for MB dye was examined, respectively. It is believed that this robust SBA/HPG-COOH adsorbent will find important application in removal of cationic adsorbates from aqueous solution.

  10. Synthesis and utilization of a novel carbon nanotubes supported nanocables for the adsorption of dyes from aqueous solutions

    SciTech Connect

    Liu, Wei; Jiang, Xinyu; Chen, Xiaoqing

    2015-09-15

    Using multiwalled carbon nanotubes(MWCNTs) as mechanical support and glucose as carbon resource, a hydrothermal carbonization route was designed for the synthesis of MWCNTs@carbon nanocables with tunable diameter and length. MWCNTs are firstly used as templates for the formation of carbon-rich composite nanocables, and the diameter of the nanocables could be tailored through adjusting the hydrothermal time or the ratio of MWCNTs and glucose. Owing to abundant superficial oxygen-containing functional groups, porous surface and remarkable reactivity, the as-synthesized nanocables are capable of efficiently adsorbing cationic dye methylene blue (MB) and crystal violet (CV). Furthermore, the optimum adsorption conditions, kinetics, adsorption isotherms and adsorption thermodynamics of dyes were studied systematically. Additionally, the maximum adsorption capacities calculated from data analysis (298.5 mg/g for MB and 228.3 mg/g for CV) are significant higher than those of raw MWCNTs and some other adsorbents reported previously, which provides strong evidence for using MWCNTs@carbon nanocables as adsorbent to remove dyes from aqueous solutions. - Graphical abstract: MWCNTs@carbon nanocables has been successfully fabricated by a hydrothermal carbonization method. The as-synthesized novel samples were used as adsorbents and exhibited high adsorption capacity on MB and CV. - Highlights: • A simple, cost-effective and “green” method for the synthesis of the material. • The diameter and length of the material are relatively easy to control. • The surface has large oxygen-containing groups and preferable chemical reactivity. • Compared with raw MWCNTs and some other adsorbents, the adsorption capacity is much high.

  11. Adsorption of Sr by immobilized microorganisms

    SciTech Connect

    Watson, J.S.; Scott, C.D.; Faison, B.D.

    1988-01-01

    Wastewaters from numerous industrial and laboratory operations can contain toxic or undesirable components such as metal ions, which must be removed before discharge to surface waters. Adsorption processes that have high removal efficiencies are attractive methods for removing such contaminants. For economic operations, it is desirable to have an adsorbent that is selective for the metal contaminant of interest, has high capacity for the contaminant, has rapid adsorption kinetics, can be economically produced, and can be regenerated to a concentrated waste product or decomposed to a low-volume waste. Selected microorganisms are potentially useful adsorbents for these applications because they can be inexpensive, have high selectivities, and have high capacities for adsorption of many heavy metals, which are often problems in a variety of industries. A laboratory-scale packed column containing microbial cells immobilized within a gelatin matrix has been prepared, and its application to removal of Sr from a simulated wastewater is described. 6 refs., 2 figs., 3 tabs.

  12. Effect of the adsorbate kinetic diameter on the accuracy of the Dubinin-Radushkevich equation for modeling adsorption of organic vapors on activated carbon.

    PubMed

    Jahandar Lashaki, Masoud; Fayaz, Mohammadreza; Niknaddaf, Saeid; Hashisho, Zaher

    2012-11-30

    This paper investigates the effect of the kinetic diameter (KD) of the reference adsorbate on the accuracy of the Dubinin-Radushkevich (D-R) equation for predicting the adsorption isotherms of organic vapors on microporous activated carbon. Adsorption isotherms for 13 organic compounds on microporous beaded activated carbon were experimentally measured, and predicted using the D-R model and affinity coefficients. The affinity coefficients calculated based on molar volumes, molecular polarizabilities, and molecular parachors were used to predict the isotherms based on four reference compounds (4.3≤KD≤6.8 Å). The results show that the affinity coefficients are independent of the calculation method if the reference and test adsorbates are from the same organic group. Choosing a reference adsorbate with a KD similar to that of the test adsorbate results in better prediction of the adsorption isotherm. The relative error between the predicted and the measured adsorption isotherms increases as the absolute difference in the kinetic diameters of the reference and test adsorbates increases. Finally, the proposed hypothesis was used to explain reports of inconsistent findings among published articles. The results from this study are important because they allow a more accurate prediction of adsorption capacities of adsorbents which allow for better design of adsorption systems. PMID:23044198

  13. Protein adsorption to multi-component glasses

    NASA Astrophysics Data System (ADS)

    Hall, Matthew Micah

    2003-07-01

    The adsorption of human serum albumin (HSA) to sodium silicate, soda lime silicate (SLS), and sodium aluminosilicate (SAS) glass microspheres was investigated using sodiumdodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in conjunction with a colloidal silver stain for visualization. The 30 Na2O·70 SiO2 composition could not be evaluated due to an apparent chemical interference that occurred during silver staining. This inhibitory effect was attributed to the extensive corrosion that occurred during the protein elution and caused an elevation in the pH of the solution. The remaining glass compositions were sufficiently durable for further study. The HSA adsorption capacity of SLS glass microspheres containing 70 and 80 mol% SiO2 increased as CaO was substituted for Na2O. An abrupt decrease in the HSA adsorption capacity was observed for SLS glasses containing 60 mol% SiO2. A similar trend was observed for the SAS glass microspheres, although the SAS glasses adsorbed less HSA than the SLS glasses containing equivalent molar percentages of SiO2. The initial increase in HSA adsorption capacity for SLS and SAS glasses containing 70 and 80 MOM SiO2 was attributed to the introduction of positive charges into the glass surfaces via Ca2+ and Al3+ cations. The decrease in HSA adsorption capacity for SLS and SAS glasses containing 60 mol% SiO2 may be due to an enhanced affinity between the glasses and HSA, resulting in a "flattened" conformation that limits the total accessible area for adsorption.

  14. Characterization of biochars derived from agriculture wastes and their adsorptive removal of atrazine from aqueous solution: A comparative study.

    PubMed

    Liu, Na; Charrua, Alberto Bento; Weng, Chih-Huang; Yuan, Xiaoling; Ding, Feng

    2015-12-01

    The physicochemical properties of biochars produced from soybeans (SBB), corn stalks (CSB), rice stalks (RSB), poultry manure (PMB), cattle manure (CMB), and pig manure (PgMB) and their adsorption characteristics of atrazine were investigated. The adsorption capacity increased with the increase of temperature and initial atrazine concentration. More atrazine was removed from basic solutions than acidic solutions, due to the effects of adsorption and hydrolysis. The Freundlich isotherm adsorption parameters indicated that the adsorption capacity decreased in the order SBB>RSB>CMB>CSB>PMB>PgMB, which is associated to the pore volume of biochars. The total pore volume and biochar pH were concluded to play important roles in determining the adsorption capacity, and they may have contributed to physical adsorption mechanisms dominating the overall adsorption process (the low activation energy for all of the biochars). Modified Freundlich and intraparticle diffusion models were used to describe the kinetics of the adsorption process. PMID:26364228

  15. Centrifugal Adsorption Cartridge System

    NASA Technical Reports Server (NTRS)

    Gonda, Steve R.; Tsao, Yow-Min D.; Lee, Wenshan

    2004-01-01

    The centrifugal adsorption cartridge system (CACS) is an apparatus that recovers one or more bioproduct(s) from a dilute aqueous solution or suspension flowing from a bioreactor. The CACS can be used both on Earth in unit gravity and in space in low gravity. The CACS can be connected downstream from the bioreactor; alternatively, it can be connected into a flow loop that includes the bioreactor so that the liquid can be recycled. A centrifugal adsorption cartridge in the CACS (see figure) includes two concentric cylinders with a spiral ramp between them. The volume between the inner and outer cylinders, and between the turns of the spiral ramp is packed with an adsorbent material. The inner cylinder is a sieve tube covered with a gas-permeable, hydrophobic membrane. During operation, the liquid effluent from the bioreactor is introduced at one end of the spiral ramp, which then constrains the liquid to flow along the spiral path through the adsorbent material. The spiral ramp also makes the flow more nearly uniform than it would otherwise be, and it minimizes any channeling other than that of the spiral flow itself. The adsorbent material is formulated to selectively capture the bioproduct(s) of interest. The bioproduct(s) can then be stored in bound form in the cartridge or else eluted from the cartridge. The centrifugal effect of the spiral flow is utilized to remove gas bubbles from the liquid. The centrifugal effect forces the bubbles radially inward, toward and through the membrane of the inner cylinder. The gas-permeable, hydrophobic membrane allows the bubbles to enter the inner cylinder while keeping the liquid out. The bubbles that thus enter the cylinder are vented to the atmosphere. The spacing between the ramps determines rate of flow along the spiral, and thereby affects the air-bubble-removal efficiency. The spacing between the ramps also determines the length of the fluid path through the cartridge adsorbent, and thus affects the bioproduct

  16. Assessing the Adsorption Properties of Shales

    NASA Astrophysics Data System (ADS)

    Pini, R.

    2014-12-01

    Fine-grained rocks, such as shales, contain a significant amount of nanopores that can significantly contribute to their storage capacity through the mechanism of adsorption. 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, thus leading to very low recovery efficiencies. Shales constitute also a great portion of so-called caprocks above potential CO2 sequestration sites; hereby, the adsorption process may limit the CO2 mobility within the cap-rock, thus minimizing leakage phenomena. Whether it is a reservoir or a caprock, 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 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. The data are analyzed by using thermodynamically rigorous measures of adsorption and a graphical method is applied for their interpretation. The density of the adsorbed phase is estimated and compared to data reported in the literature; the latter is key to disclose gas-reserves and/or potential storage capacity estimates. When evaluated against classic adsorbent materials, the adsorption mechanism in shales is further complicated by

  17. Adsorption analysis of ammonia in an aqueous solution

    SciTech Connect

    Arman, B.; Panchal, C.B.

    1993-08-01

    An analysis is carried out to determine the effects of the diffusional resistance on the rate of the adsorption of ammonia in an aqueous solution. A performance prediction model is developed to calculate the local rate of heat and mass transfer, including physical and thermodynamic property calculations of the mixture. An algorithm is developed for calculating the interfacial conditions. The local heat- and mass-transfer calculation is then incorporated into the performance prediction method for adsorption for a given geometry.

  18. Adsorption and excess fission xenon

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    The adsorption of Xe and Kr on lunar soil 10084 was measured by a method that employs only very low fractions of monolayer coverage. Results are presented as parameters for calculation of the Henry constant for adsorption as a function of temperature. The adsorption potentials are about 3 kcal/mole for Kr and 5 kcal/mole for Xe; heating the sample in vacuum increased the Xe potential to nearly 7 kcal/mole. Henry constants at the characteristic lunar temperature are about 0.3 cu cm STP/g-atm. These data were applied to consider whether adsorption is important in producing the excess fission Xe effect characteristic of highland breccias. Sorption equilibrium with a transient lunar atmosphere vented fission Xe produces concentrations seven orders of magnitude lower than observed concentrations. Higher concentrations result because of the resistance of the regolith to upward diffusion of Xe. A diffusion coefficient of 0.26 sq cm/sec is estimated for this process.

  19. Mono-layer BC2 a high capacity anode material for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Hardikar, Rahul; Samanta, Atanu; Han, Sang Soo; Lee, Kwang-Ryeol; Singh, Abhishek

    2015-04-01

    Mono-layer of graphene with high surface area compared to the bulk graphite phase, shows less Li uptake. The Li activity or kinetics can be modified via defects and/or substitutional doping. Boron and Nitrogen are the best known dopants for carbonaceous anode materials. In particular, boron doped graphene shows higher capacity and better Li adsorption compared to Nitrogen doped graphene. Here, using first principles density functional theory calculations, we study the spectrum of boron carbide (BCx) mono-layer phases in order to estimate the maximum gravimetric capacity that can be achieved by substitutional doping in graphene. Our results show that uniformly boron doped BC2 phase shows a high capacity of? 1400 mAh/g, much higher than previously reported capacity of BC3. Supported by Korea Institute of Science and Technology.

  20. Amino-functionalized mesoporous MCM-41 silica as an efficient adsorbent for water treatment: batch and fixed-bed column adsorption of the nitrate anion

    NASA Astrophysics Data System (ADS)

    Ebrahimi-Gatkash, Mehdi; Younesi, Habibollah; Shahbazi, Afsaneh; Heidari, Ava

    2015-11-01

    In the present study, amino-functionalized Mobil Composite Material No. 41 (MCM-41) was used as an adsorbent to remove nitrate anions from aqueous solutions. Mono-, di- and tri-amino functioned silicas (N-MCM-41, NN-MCM-41 and NNN-MCM-41) were prepared by post-synthesis grafting method. The samples were characterized by means of X-ray powder diffraction, FTIR spectroscopy, thermogravimetric analysis, scanning electron microscopy and nitrogen adsorption-desorption. The effects of pH, initial concentration of anions, and adsorbent loading were examined in batch adsorption system. Results of adsorption experiments showed that the adsorption capacity increased with increasing adsorbent loading and initial anion concentration. It was found that the Langmuir mathematical model indicated better fit to the experimental data than the Freundlich. According to the constants of the Langmuir equation, the maximum adsorption capacity for nitrate anion by N-MCM-41, NN-MCM-41 and NNN-MCM-41 was found to be 31.68, 38.58 and 36.81 mg/g, respectively. The adsorption kinetics were investigated with pseudo-first-order and pseudo-second-order model. Adsorption followed the pseudo-second-order rate kinetics. The coefficients of determination for pseudo-second-order kinetic model are >0.99. For continuous adsorption experiments, NNN-MCM-41 adsorbent was used for the removal of nitrate anion from solutions. Breakthrough curves were investigated at different bed heights, flow rates and initial nitrate anion concentrations. The Thomas and Yan models were utilized to calculate the kinetic parameters and to predict the breakthrough curves of different bed height. Results from this study illustrated the potential utility of these adsorbents for nitrate removal from water solution.

  1. Synthesis of Ordered Mesoporous Silica for Energy-efficient Adsorption Systems

    NASA Astrophysics Data System (ADS)

    Endo, Akira; Komori, Kou; Inagi, Yuki; Fujisaki, Satoko; Yamamoto, Takuji

    Energy-efficient adsorption systems, such as adsorption heat pump, desiccant cooling, humidity control system, and so on, are expected as a energy exchange process because they are able to utilize low temperature exhaust heat. As an adsorbent for such systems, materials with large adsorption capacity in the pressure range of practical operation are preferable. To enable the design and synthesis of materials with large heat storage capacity, the pore structure of adsorbents should be optimized for each systems. In this paper, we synthesized ordered mesoporous silica (MPS) with an arrow pore size distribution of around 2nm by a solvent evaporation method and evaluated their water adsorption properties. The adsorption isotherms for MPSs showed steep increase at a relative humidity corresponding to their pore size. Since MPSs have a large adsorption capacity than conventional materials in the relative humidity region of practical operation, they are expected for new adsorbents for energy-efficient adsorption systems.

  2. Adsorption behavior of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) on boehmite.

    PubMed

    Wang, Fei; Liu, Chengshuai; Shih, Kaimin

    2012-11-01

    Understanding the interaction of perfluorochemicals, persistent pollutants with known human health effects, with mineral compounds in surface water and groundwater environments is essential to determining their fate and transport. Kinetic experiments showed that adsorption equilibrium can be achieved within 48 h and the boehmite (AlOOH) surface is receptive to perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) adsorption. The adsorption isotherms estimated the maximum adsorption capacities of PFOS and PFOA on boehmite as 0.877 μg m(-2) and 0.633 μg m(-2), respectively. Compared to the adsorption capacity on γ-alumina, the abundant hydroxyl groups on boehmite surfaces resulted in the 2-3 times higher adsorption of PFOS and PFOA. Increasing solution pH led to a moderate decrease in PFOS and PFOA adsorption, owing to an increase in ligand exchange reactions and the decrease of electrostatic interactions. The presence of NaCl and CaCl(2) in solution demonstrated negative effects for PFOS and PFOA adsorption on boehmite surfaces, with potential mechanisms being electrical double layer compression, competitive adsorption of chloride, and the Ca(2+) bridging effect between perfluorochemicals. PMID:22897837

  3. Adsorption behavior of epirubicin hydrochloride on carboxylated carbon nanotubes.

    PubMed

    Chen, Zhe; Pierre, Dramou; He, Hua; Tan, Shuhua; Pham-Huy, Chuong; Hong, Hao; Huang, Jilong

    2011-02-28

    The aim of this study was to understand the interaction between carboxylated carbon nanotubes (c-CNTs) and anticancer agents and evaluate the drug-loading ability of c-CNTs. We prepared carboxylated multi-walled carbon nanotubes (c-MWNTs) with nitric acid treatment, then evaluated the adsorption ability of c-MWNTs as adsorbents for loading of the anticancer drug, epirubicin hydrochloride (EPI), and investigated the adsorption behavior of EPI on c-MWNTs. Unmodified multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) were included as comparative adsorbents. The results showed that carbon nanotubes were able to form supramolecular complexes with EPI via π-π stacking and possessed favorable loading properties as drug carriers. The Freundilich adsorption model was successfully employed to describe the adsorption process. Because of the high surface area and hydrogen bonding, c-MWNTs' adsorption efficiency was the highest and the most stable and their drug-loading capacity was superior to that of MWNTs. With the increase of pH, the adsorption capacity of EPI on the c-MWNTs increased. Low-temperature facilitated the adsorption. More rapid EPI adsorption rate and higher drug-loading ability were observed from c-MWNTs with smaller diameter. Moreover, the adsorption kinetics of EPI on c-MWNTs could be well depicted by using the pseudo-second-order kinetic model. PMID:21145959

  4. [Adsorption Behaviors of Lead on Multi-Walled Carbon Nanotube-Hydroxyapatite Composites].

    PubMed

    Zhang, Jin-li; Li, Yu

    2015-07-01

    Multi-walled carbon nanotube-hydroxyapatite composites (MWCNT-HAP) were employed as the sorbent to study the sorption characteristic of Pb (II) using batch experiments. Effects of dosage of adsorbent, pH, ionic strength, contact time, initial concentration of lead and temperature were investigated. The results indicated that the removal of lead to MWCNT-HAP composites was strongly dependent on dosage of adsorbent, pH, temperature, and independent of ionic strength. The maximum adsorption capacity of lead was about 716. 13 mg.g-1 at 20°C, with a solid/liquid ratio of 0.08 g.L-1, pH0 = 5.5 and an initial concentration of 100 mg.L-1. The adsorption of Pb(II) on MWCNT-HAP composites was a fast process and could reach the equilibrium within 60 minutes. Ninety percent of the maximum adsorption capacity could be reached in 30 minutes. The kinetic data were fitted to pseudo-second-order kinetic model reasonably well. The kinetic sorption of Pb(II) on MWCNT-HAP was well described by pseudo-second-order kinetic model. The negative free energy calculated from the temperature dependent sorption isotherms suggested that the sorption of Pb(II) on MWCNT-HAP composites was a spontaneous process, and high temperature favored the adsorption process. The higher correlation coefficient values (R2 = 0. 999 8 - 1. 000 0) of Langmuir isotherm model at different temperatures suggested that Langmuir model could be used to simulate the sorption of Pb(II) on MWCNT-HAP. The adsorption mechanism mainly involves surface complexation between the lead ions and the surface oxygen-containing functional groups of the MWCNT-HAP, dissolution of HAP and precipitation of pyromorphite [Pb10 (PO4)6 (OH) 2], ion exchange reaction between Pb2+ and Ca2+ of hydroxyapatite. PMID:26489325

  5. Utilization of activated carbon produced from fruit juice industry solid waste for the adsorption of Yellow 18 from aqueous solutions.

    PubMed

    Angin, Dilek

    2014-09-01

    The use of activated carbon obtained from sour cherry (Prunus cerasus L.) stones for the removal of a basic textile dye, which is Yellow 18, from aqueous solutions at different contact times, pH values and solution temperatures was investigated. The surface area and micropore volume of chemically modified activated carbon were 1704 m(2) g(-1) and 0.984 cm(3) g(-1), respectively. The experimental data indicated that the adsorption isotherms were well described by the Langmuir equilibrium isotherm equation and the calculated adsorption capacity was 75.76 mg g(-1) at 318 K. The adsorption kinetic of Yellow 18 obeys the pseudo-second-order kinetic model. The thermodynamic parameters were calculated to estimate the nature of adsorption. The activation energy of the system was calculated as 0.71-2.36 kJ/mol. According to these results, prepared activated carbon could be used as a low-cost adsorbent to compare with the commercial activated carbon for the removal of Yellow 18 from wastewater. PMID:24656549

  6. Ligand Functionalization in Metal-Organic Frameworks for Enhanced Carbon Dioxide Adsorption.

    PubMed

    Wang, Hao; Peng, Junjie; Li, Jing

    2016-06-01

    Ligand functionalization in metal-organic frameworks (MOFs) has been studied extensively and has been demonstrated to enhance gas adsorption and induce interesting gas adsorption phenomena. This account summarizes our recent study of three series of MOFs by ligand functionalization, as well as their carbon dioxide adsorption properties. While ligand functionalization does not change the overall structure of the frameworks, it can influence their gas adsorption behavior. In the first two series, we show how ligand functionalization influences the CO2 affinity and adsorption capacity of MOFs. We also show a special case in which subtle changes in ligand functionality alter the CO2 adsorption profile. PMID:27071491

  7. Preparation of activated carbon from a renewable bio-plant of Euphorbia rigida by H 2SO 4 activation and its adsorption behavior in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Gerçel, Özgül; Özcan, Adnan; Özcan, A. Safa; Gerçel, H. Ferdi

    2007-03-01

    The use of activated carbon obtained from Euphorbia rigida for the removal of a basic textile dye, which is methylene blue, from aqueous solutions at various contact times, pHs and temperatures was investigated. The plant material was chemically modified with H 2SO 4. The surface area of chemically modified activated carbon was 741.2 m 2 g -1. The surface characterization of both plant- and activated carbon was undertaken using FTIR spectroscopic technique. The adsorption process attains equilibrium within 60 min. The experimental data indicated that the adsorption isotherms are well described by the Langmuir equilibrium isotherm equation and the calculated adsorption capacity of activated carbon was 114.45 mg g -1 at 40° C. The adsorption kinetics of methylene blue obeys the pseudo-second-order kinetic model and also followed by the intraparticle diffusion model up to 60 min. The thermodynamic parameters such as Δ G°, Δ H° and Δ S° were calculated to estimate the nature of adsorption. The activation energy of the system was calculated as 55.51 kJ mol -1. According to these results, prepared activated carbon could be used as a low-cost adsorbent to compare with the commercial activated carbon for the removal textile dyes from textile wastewater processes.

  8. Specific cooling capacity of liquid nitrogen

    NASA Technical Reports Server (NTRS)

    Kilgore, R. A.; Adcock, J. B.

    1977-01-01

    The assumed cooling process and the method used to calculate the specific cooling capacity of liquid nitrogen are described, and the simple equation fitted to the calculated specific cooling capacity data, together with the graphical form calculated values of the specific cooling capacity of nitrogen for stagnation temperatures from saturation to 350 K and stagnation pressures from 1 to 10 atmospheres, are given.

  9. Adsorption studies of methylene blue dye on tunisian activated lignin

    NASA Astrophysics Data System (ADS)

    Kriaa, A.; Hamdi, N.; Srasra, E.

    2011-02-01

    Activated carbon prepared from natural lignin, providing from a geological deposit, was used as the adsorbent for the removal of methylene blue (MB) dye from aqueous solutions. Batch adsorption studies were conducted to evaluate various experimental parameters like pH and contact time for the removal of this dye. Effective pH for MB removal was 11. Kinetic study showed that the adsorption of dye was gradual process. Quasi equilibrium reached in 4 h. Pseudo-first-order, pseudo-second-order were used to fit the experimental data. Pseudo-second-order rate equation was able to provide realistic description of adsorption kinetics. The experimental isotherms data were also modelled by the Langmuir and Freundlich equation of adsorption. Equilibrium data fitted well with the Langmuir model with maximum monolayer adsorption capacity of 147 mg/g. Activated lignin was shown to be a promising material for adsorption of MB from aqueous solutions.

  10. Simultaneous determination of cation exchange capacity and surface area of acid activated bentonite powders by methylene blue sorption

    NASA Astrophysics Data System (ADS)

    Yener, Nilgün; Biçer, Cengiz; Önal, Müşerref; Sarıkaya, Yüksel

    2012-01-01

    To distinguish the ion exchanged and physically adsorbed methylene blue cations (MB+) on ionic surfaces, acid activated bentonite samples were used as porous adsorbents. A natural calcium bentonite (CaB) sample from Enez/Edirne, Turkey, was acid activated at 90 °C for 16 h with various HCl/CaB ratios. The irreversible exchange and physical adsorption of MB+ cations on the ionic solids have simultaneously occurred. The ion exchanged (mex) and physically adsorbed (mad) MB+ contents were obtained as the values of sorption capacity at c = 0 and the increase to a plateaus of adsorption isotherms, respectively. The mad value was taken to be monolayer adsorption capacity. Cation exchange capacity (CEC) and specific surface area (SMB) for each sample were calculated from the mex and mad values, respectively. Also, the BET specific surface areas (SBET) and pore size distribution were determined from low temperature nitrogen adsorption/desorption data. A linear correlation between the SMB and SBET values was found.

  11. Comparative evaluation of adsorption kinetics of diclofenac and isoproturon by activated carbon.

    PubMed

    Torrellas, Silvia A; Rodriguez, Araceli R; Escudero, Gabriel O; Martín, José María G; Rodriguez, Juan G

    2015-01-01

    Adsorption mechanism of diclofenac and isoproturon onto activated carbon has been proposed using Langmuir and Freundlich isotherms. Adsorption capacity and optimum adsorption isotherms were predicted by nonlinear regression method. Different kinetic equations, pseudo-first-order, pseudo-second-order, intraparticle diffusion model and Bangham kinetic model, were applied to study the adsorption kinetics of emerging contaminants on activated carbon in two aqueous matrices. PMID:26301850

  12. MOLECULAR OXYGEN AND THE ADSORPTION OF PHENOLS - EFFECT OF FUNCTIONAL GROUPS

    EPA Science Inventory

    This study reveals that the presence of molecular oxygen (oxic conditions) has a significant impact on the exhibited adsorptive capacity of granular activated carbon (GAC) for several phenolic compounds. The increase in the GAC adsorptive capacity under oxic conditions results f...

  13. New sorbents for olefin/paraffin separations by adsorption via {pi}-complexation

    SciTech Connect

    Yang, R.T.; Kikkinides, E.S.

    1995-03-01

    New adsorbents for olefin paraffin separation are synthesized by effective dispersion of Ag(I) and Cu(I) cations on substrates with hydrocarbon-phobic surfaces. These cations bind olefin molecules by a {pi}-complexation bond, a weak chemical bond. Ethane/ethylene and propane/propylene separations are considered. Cation exchange resins and CuCl/{gamma}-Al{sub 2}O{sub 3} are effective substrates. On the Ag(I) resin at 25 C and 1 atm, the equilibrium adsorption ratio for C{sub 2} H{sub 4}/C{sub 2}H{sub 6} = 9.2 and C{sub 2}H{sub 4} capacity = 1.15 mmol/g; the corresponding values for C{sub 3}H{sub 6}/C{sub 3}H{sub 8} = 10.4 and C{sub 3}H{sub 6} capacity = 1.29 mmol/g. The CuCl/{gamma}-Al{sub 2}O{sub 3} sorbent shows equally promising results. The sorption rates are pore-diffusion-controlled and rapid. The olefin selectivity, capacity, and rates are much higher than all previous attempts and are suitable for applications in cyclic adsorption processes. The equilibrium data are correlated with an isotherm equation that accounts for both physical adsorption and {pi}-complexation with energy, heterogeneity, using only two true fitting parameters. Molecular orbital calculations using a C{sub 6}H{sub 5}SO{sub 3}{sup {minus}} substrate indicate that the {pi}-complexation bond is contributed mainly by the donation of olefin {pi}-bond electrons to the empty s-orbital of the metal, while the d-{pi}* back donation contributes only 16%. Moreover, the relative order of the heats of adsorption is correctly predicted.

  14. Microemulsion synthesis of hydroxyapatite nanomaterials and their adsorption behaviors for Cr3+ ions

    NASA Astrophysics Data System (ADS)

    Gao, Y. L.; Wang, X. S.; Cui, H. H.; Mu, M. M.; Huang, F. Z.

    2016-05-01

    Hydroxyapatite (HAP) nanoparticles with different morphologies, such as nanorods, nanospheres, and their mixtures were successfully synthesized by microemulsion method with soluble additive. Their adsorption capacity for Cr3+ ion was investigated. Most of the Cr3+ were absorbed by HAP within 60 min. The adsorption capacity of the HAP nanospheres was the best, and the maximum Cr3+ removal ratio was 96.4%, revealing that the metal ions adsorption by HAP is dependent on the morphology of its particles.

  15. Adsorption of organic molecules at the mercury-solution interface: effect of anion specific adsorption on double layer properties. [Benzyl alcohol

    SciTech Connect

    Buckfelder, J.J. III

    1980-08-01

    Adsorption of iso-pentanol, pentanoic acid, and benzyl alcohol at the mercury-solution interface was studied in HC1O/sub 4/, H/sub 2/SO/sub 4/, NaNO/sub 3/, and NaF electrolytes. The Frumkin isotherm equation Ba = (theta/(1-theta))exp(2..cap alpha..theta) together with the implied charge vs. surface excess relation: q = (1-theta)q/sub w/ + thetaQ were used to analyze the experimental data. Linear charge vs surface excess plots were obtained for the aliphatic compounds over the entire potential region studied; for benzyl alcohol, plots were linear only at anodic potentials. The slopes of these lines agreed with those predicted by the above equation, with Q = C/sub org/(V-V/sub n/), for cathodic potentials. At potentials anodic to the electrocapillary maximum, deviations between experimental and theoretical slopes appeared. In the model proposed, the double layer consists of two parts. The layer closest to the surface is restricted to water molecules and specifically adsorbed ions. The second layer contains organic molecules exclusively; any charge necessary to balance the surface charge is considered to be in a monolayer adjacent to the organic layer. From the slope of the charge vs surface excess plots, it is possible to calculate the charge on the covered portion of the surface and then calculate the amount of specific adsorption. The relative amounts of specific adsorption are in agreement with known strengths of adsorption of the anions of the electrolyte. Capacity curves were also calculated and were in good agreement with experimental curves.

  16. Ti₃C₂ MXene as a high capacity electrode material for metal (Li, Na, K, Ca) ion batteries.

    PubMed

    Er, Dequan; Li, Junwen; Naguib, Michael; Gogotsi, Yury; Shenoy, Vivek B

    2014-07-23

    Two-dimensional (2-D) materials are capable of handling high rates of charge in batteries since metal ions do not need to diffuse in a 3-D lattice structure. However, graphene, which is the most well-studied 2-D material, is known to have no Li capacity. Here, adsorption of Li, as well as Na, K, and Ca, on Ti3C2, one representative MXene, is predicted by first-principles density functional calculations. In our study, we observed that these alkali atoms exhibit different adsorption energies depending on the coverage. The adsorption energies of Na, K, and Ca decrease as coverage increases, while Li shows little sensitivity to variance in coverage. This observed relationship between adsorption energies and coverage of alkali ions on Ti3C2 can be explained by their effective ionic radii. A larger effective ionic radius increases interaction between alkali atoms, thus lower coverage is obtained. Our calculated capacities for Li, Na, K, and Ca on Ti3C2 are 447.8, 351.8, 191.8, and 319.8 mAh/g, respectively. Compared to materials currently used in high-rate Li and Na ion battery anodes, MXene shows promise in increasing overall battery performance. PMID:24979179

  17. Adsorption of herbicides using activated carbons

    SciTech Connect

    Derbyshire, F.; Jagtoyan, M.; Lafferty, C.; Kimber, G.

    1996-10-01

    This work describes development of a series of novel activated carbon materials and their testing for possible water treatment applications by studying the adsorption of sodium pentachlorphenolate, PCP (a common herbicide/wood preservative). Although the application of activated carbons is an established technology for the treatment of public water supplies, there is a growing need for materials with higher selectivity and adsorptive capacities as well as high abrasion resistance. The materials that will be discussed include extruded wood-derived carbons with novel pore size distributions and high hardness, as well as activated carbon fiber composites. Comparisons will be made with commercial granular water treatment carbons.

  18. Adsorption of Methylene Blue from Aqueous Solutions by Polyvinyl Alcohol/Graphene Oxide Composites.

    PubMed

    Yang, Xiaoxia; Li, Yanhui; Du, Qiuju; Wang, Xiaohui; Hu, Song; Chen, Long; Wang, Zonghua; Xia, Yanzhi; Xia, Linhua

    2016-02-01

    As a new member of the carbon family, graphene oxide (GO) has shown excellent adsorption ability to micro-pollutants in aqueous solutions. However, its tiny size makes it difficult to be removed from aqueous solutions using the conventional separation methods, which limits its practical application in the environmental protection. In this study, polyvinyl alcohol (PVA) was used as carrier immobilizing GO, and novel PVA/GO composites were prepared. The morphology and physicochemical properties of the composites were characterized by SEM, FTIR and TGA analysis. The adsorption properties of methylene blue (MB) onto the composites were studied through investigating the experimental parameters such as solution pH, adsorbent dosage, contact time and temperature. The isotherm data were analyzed using the Langmuir, Freundlich and Dubinin-Radushkevich models. The calculated maximum adsorption capacity reached 476.2 mg/g at 50% GO content. The pseudo-first-order kinetic, pseudo-second-order kinetic and intra-particle diffusion models were used to explore the adsorption kinetics. The results showed that the dynamic data were fitted to the pseudo-second-order kinetic model. PMID:27433669

  19. Design and cost estimate for the SRL integrated hot off gas facility using selective adsorption

    SciTech Connect

    Pence, D T; Kirstein, B E

    1981-07-01

    Based on the results of an engineering-scale demonstration program, a design and cost estimate were performed for a 25-m/sup 3//h (15-ft/sup 3//min) capacity pilot plant demonstration system using selective adsorption technology for installation at the Integrated Hot Off Gas Facility at the Savannah River Plant. The design includes provisions for the destruction of NO/sub x/ and the concentration and removal of radioisotopes of ruthenium, iodine-129, tritiated water vapor, carbon-14 contaminated carbon dioxide, and krypton-85. The nobel gases are separated by the use of selective adsorption on mordenite-type zeolites. The theory of noble gas adsorption on zeolites is essentially the same as that for the adsorption of noble gases on activated charcoals. Considerable detail is provided regarding the application of the theory to adsorbent bed designs and operation. The design is based on a comprehensive material balance and appropriate heat transfer calculations. Details are provided on techniques and procedures used for heating, cooling, and desorbing the adsorbent columns. Analyses are also given regarding component and arrangement selection and includes discussions on alternative arrangements. The estimated equipment costs for the described treatment system is about $1,400,000. The cost estimate includes a detailed equipment list of all the major component items in the design. Related technical issues and estimated system performance are also discussed.

  20. Determination of surface-accessible acidic hydroxyls and surface area of lignin by cationic dye adsorption.

    PubMed

    Sipponen, Mika Henrikki; Pihlajaniemi, Ville; Littunen, Kuisma; Pastinen, Ossi; Laakso, Simo

    2014-10-01

    A new colorimetric method for determining the surface-accessible acidic lignin hydroxyl groups in lignocellulose solid fractions was developed. The method is based on selective adsorption of Azure B, a basic dye, onto acidic hydroxyl groups of lignin. Selectivity of adsorption of Azure B on lignin was demonstrated using lignin and cellulose materials as adsorbents. Adsorption isotherms of Azure B on wheat straw (WS), sugarcane bagasse (SGB), oat husk, and isolated lignin materials were determined. The maximum adsorption capacities predicted by the Langmuir isotherms were used to calculate the amounts of surface-accessible acidic hydroxyl groups. WS contained 1.7-times more acidic hydroxyls (0.21 mmol/g) and higher surface area of lignin (84 m(2)/g) than SGB or oat husk materials. Equations for determining the amount of surface-accessible acidic hydroxyls in solid fractions of the three plant materials by a single point measurement were developed. A method for high-throughput characterization of lignocellulosic materials is now available. PMID:25033327

  1. Molecular-Scale Study of Aspartate Adsorption on Goethite and Competition with Phosphate.

    PubMed

    Yang, Yanli; Wang, Shengrui; Xu, Yisheng; Zheng, Binghui; Liu, Jingyang

    2016-03-15

    Knowledge of the interfacial interactions between aspartate and minerals, especially its competition with phosphate, is critical to understanding the fate and transport of amino acids in the environment. Adsorption reactions play important roles in the mobility, bioavailability, and degradation of aspartate and phosphate. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR) measurements and density functional theory (DFT) calculations were used to investigate the interfacial structures and their relative contributions in single-adsorbate and competition systems. Our results suggest three dominant mechanisms for aspartate: bidentate inner-sphere coordination involving both α- and γ-COO(-), outer-sphere complexation via electrostatic attraction and H-bonding between aspartate NH2 and goethite surface hydroxyls. The interfacial aspartate is mainly governed by pH and is less sensitive to changes of ionic strength and aspartate concentration. The phosphate competition significantly reduces the adsorption capacity of aspartate on goethite. Whereas phosphate adsorption is less affected by the presence of aspartate, including the relative contributions of diprotonated monodentate, monoprotonated bidentate, and nonprotonated bidentate structures. The adsorption process facilitates the removal of bioavailable aspartate and phosphate from the soil solution as well as from the sediment pore water and the overlying water. PMID:26870876

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

    PubMed

    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

  3. The distribution and adsorption behavior of aliphatic amines in marine and lacustrine sediments

    SciTech Connect

    Wang, Xuchen; Lee, C. )

    1990-10-01

    The methylated amines - monomethyl-, dimethyl-, and trimethyl amine (MMA, DMA, TMA) - are commonly found in aquatic environments, apparently as a result of decomposition processes. Adsorption of these amines to clay minerals and organic matter significantly influences their distribution in sediments. Laboratory measurements using {sup 14}C-radiolabelled amines and application of a linear partitioning model resulted in calculated adsorption coefficients of 2.4-4.7 (MMA), 3.3 (DMA), and 3.3-4.1 (TMA). Further studies showed that adsorption of amines is influenced by salinity of the porewaters, and clay mineral and organic matter content of the sediment solid phase. Concentrations of monomethyl- and dimethyl amine were measured in the porewaters and the solid phase of sediment samples collected from Flax Pond and Lake Ronkonkoma (NY), Long Island Sound, and the coastal Peru upwelling area. These two amines were present in all sediments investigated. A clear seasonal increase in the solid-phase concentration of MMA and DMA in Flax Pond sediments was likely related to the annual senescence of salt marsh grasses, either directly as a source of these compounds or indirectly by providing additional exchange capacity to the sediments. The distribution of amines in the solid and dissolved phases observed in all sediments investigated suggests that the distribution of these compounds results from a balance among production, decomposition, and adsorption processes.

  4. Adsorption of heavy metal cations by Na-clinoptilolite: equilibrium and selectivity studies.

    PubMed

    Mihaly-Cozmuta, L; Mihaly-Cozmuta, A; Peter, A; Nicula, C; Tutu, H; Silipas, Dan; Indrea, Emil

    2014-05-01

    This paper summarizes the conclusions of experiments conducted on the adsorption of Cd(2+), Co(2+), Cu(2+), Mn(2+), Ni(2+), Pb(2+) and Zn(2+) onto zeolite. The focus of the experiments was to establish the influence of the initial pH of the contact solution as well as the selectivity of zeolite on the efficiency of the adsorption process. To this end, experimental adsorption isotherms were established for the pH values ranging from 1 to 4 by using the Na-form of clinoptilolite (particle size range 0.5-1 mm) as an adsorbent. Langmuir, Freundlich and Dubinin-Raduschkevich isotherm models were used to validate the experimental data and the Gibbs free energy was calculated based on the distribution coefficient. From the Langmuir model, correlations between the maximum adsorption capacity and selected physical-chemical parameters of the cations studied were established. The results of the experiments suggest that the selectivity of zeolite is strongly influenced by the pH of the contact solution, dehydration energy of cations, diffusion coefficient and the pH at which the precipitation of hydroxides occurs. PMID:24603029

  5. Probing the Adsorption Behavior of 4,5-Diazafluoren-9-one and Its Schiff Base Derivatives on SIlver and Gold Nanosurfaces Using Raman Spectroscopy, Density Functional Theory and Potential Energy Distribution Calculations

    NASA Astrophysics Data System (ADS)

    McCoy, Rhonda Patrice

    from the center ring was shortened because of metal-ligand coordination. These observations are correlated to the shifts in Raman frequencies; a decrease in bond length resulted in a shift to a higher vibrational energy. The surface-enhanced Raman spectrum of DAFO was obtained on silver colloids and gold nanorods. The resulting SER spectra were compared to their corresponding normal Raman spectra, there were changes in relative band intensities and there were bands shifted because of adsorption; these observations were used to probe orientation. Orientation is determined by applying surface selections rules developed by both Creighton and Moskovits. The rules indicate, when the vibrational modes assigned to out-of-plane modes are observed as enhanced in the SER spectrum, the ligand is considered parallel relative to the metal surface, and when the vibrational modes assigned to in-plane modes are observed as enhanced, the ligand is not parallel relative to the metal surface. The relative surface enhancement factors were calculated by normalizing the spectra and then by taking the ratio of ISERS/INR. Based on the enhancement factors, the bands assigned to in-plane modes exhibited the highest enhancement factors on the Au and Ag SER spectra. This observation suggests that DAFO is not parallel to the metal nano-surfaces. In the Ag SERS spectrum the bands with the highest enhancement factors were assigned to quadrant ring stretching and cyclopentone bending. Analysis of the carbonyl stretching frequency on the Ag spectrum revealed the frequency shifted to a lower vibrational energy. This shift has been ascribed to the carbonyl bond losing double bond character, which permits the interaction between the metal and the carbonyl oxygen. It was proposed the DAFO ligand is sandwiched between the silver hydrosol. The TER spectrum of DAFO was obtained; analysis of the spectrum revealed similarities to the Ag SERS spectrum. The carbonyl stretching frequency was lowered, the bands

  6. Adsorption Refrigeration System

    SciTech Connect

    Wang, Kai; Vineyard, Edward Allan

    2011-01-01

    Adsorption refrigeration is an environmentally friendly cooling technology which could be driven by recovered waste heat or low-grade heat such as solar energy. In comparison with absorption system, an adsorption system has no problems such as corrosion at high temperature and salt crystallization. In comparison with vapor compression refrigeration system, it has the advantages of simple control, no moving parts and less noise. This paper introduces the basic theory of adsorption cycle as well as the advanced adsorption cycles such as heat and mass recovery cycle, thermal wave cycle and convection thermal wave cycle. The types, characteristics, advantages and drawbacks of different adsorbents used in adsorption refrigeration systems are also summarized. This article will increase the awareness of this emerging cooling technology among the HVAC engineers and help them select appropriate adsorption systems in energy-efficient building design.

  7. Efficient adsorption of phenanthrene by simply synthesized hydrophobic MCM-41 molecular sieves

    NASA Astrophysics Data System (ADS)

    Hu, Yun; He, Yinyun; Wang, Xiaowen; Wei, Chaohai

    2014-08-01

    Hydrophobic molecular sieve MCM-41 including surfactant template was synthesized by a simple method. The adsorption properties of this material toward phenanthrene were studied. The effects of adsorbent dose and pH value on the adsorption process as well as the adsorption mechanism and reuse performance were investigated. The template-containing MCM-41 showed a significant adsorption for phenanthrene, due to its hydrophobicity created by the surfactant template in MCM-41. The solution pH had little effect on the adsorption capacity. The adsorption kinetic could be fitted well with pseudo-second-order kinetic model. The adsorption equilibrium was fitted well by the linear model, and the adsorption process followed the liquid/solid phase distribution mechanism. The thermodynamic results indicated that the adsorption was a spontaneous and exothermic process.

  8. Assessment of Ethidium bromide and Ethidium monoazide bromide removal from aqueous matrices by adsorption on cupric oxide nanoparticles.

    PubMed

    Fakhri, Ali

    2014-06-01

    The present study was undertaken to develop an effective adsorbent and to study the adsorption of Ethidium bromide and Ethidium monoazide bromide from aqueous solution using the CuO nanoparticles. The characteristics of CuO nanoparticles were determined and found to have a surface area 89.59m(2)/g. Operational parameters such as pH, contact time and adsorbent concentration, initial concentration and temperature were also studied. The amount of removal increases with the increase in pH from one to seven and reaches the maximum when the pH is nine. Adsorption data fitted well with the Langmuir, Freundlich and Florry-Huggins models. The results show that the best fit was achieved with the Langmuir isotherm equation with maximum adsorption capacities of 0.868 and 0.662mg/g for Ethidium bromide and Ethidium monoazide bromide, respectively. The adsorption process was found to follow pseudo-second-order kinetics. The calculated thermodynamic parameters, namely ΔG, ΔH and ΔS showed that adsorption of Ethidium bromide and Ethidium monoazide bromide was spontaneous and endothermic under examined conditions. PMID:24630576

  9. Liquid phase adsorptions of Rhodamine B dye onto raw and chitosan supported mesoporous adsorbents: isotherms and kinetics studies

    NASA Astrophysics Data System (ADS)

    Inyinbor, A. A.; Adekola, F. A.; Olatunji, G. A.

    2016-04-01

    Irvingia gabonensis endocarp waste was charred (DNc) and subsequently coated with chitosan (CCDNc). Physicochemical characteristics of the two adsorbents were established, while Fourier transform infrared (FTIR), Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area methods were further employed for characterization. Efficiencies of the prepared adsorbents in the uptake of Rhodamine B (RhB) from aqueous effluent were investigated and adsorption data were tested using four isotherms and four kinetics models. The BET surface areas of the prepared adsorbent were 0.0092 and 4.99 m2/g for DNc and CCDNc, respectively, and maximum adsorption was recorded at pH between 3 and 4, respectively. While monolayer adsorption dominates the uptake of RhB onto DNc, uptake of RhB onto CCDNc was onto heterogeneous surface. The maximum monolayer adsorption capacities (q max) obtained from the Langmuir equation are 52.90 and 217.39 mg/g for DNc and CCDNc, respectively. Pseudo second order and Elovich kinetic models well described the kinetics of the two adsorption processes. The mean sorption energy (E) calculated from the D-R model and desorption efficiencies suggests that while the uptake of RhB onto DNc was physical in nature, for RhB-CCDNc system chemisorption dominates.

  10. Adsorption of chlorophenols on granular activated carbon

    SciTech Connect

    Yang, M.

    1993-12-31

    Studies were undertaken of the adsorption of chlorinated phenols from aqueous solution on granular activated carbon (Filtrasorb-400, 30 x 40 mesh). Single-component equilibrium adsorption data on the eight compounds in two concentration ranges at pH 7.0 fit the Langmuir equation better than the Freundlich equation. The adsorptive capacities at pH 7.0 increase from pentachlorophenol to trichlorophenols and are fairly constant from trichlorophenols to monochlorophenols. The adsorption process was found to be exothermic for pentachlorophenol and 2,4,6-trichlorophenol, and endothermic for 2,4-dichlorophenol and 4-chlorophenol. Equilibrium measurements were also conducted for 2,4,5-trichlorophenol, 2,4-dichlorophenol, and 4-chlorophenol over a wide pH range. A surface complexation model was proposed to describe the effect of pH on adsorption equilibria of chlorophenols on activated carbon. The simulations of the model are in excellent agreement with the experimental data. Batch kinetics studies were conducted of the adsorption of chlorinated phenols on granular activated carbon. The results show that the surface reaction model best describes both the short-term and long-term kinetics, while the external film diffusion model describes the short-term kinetics data very well and the linear-driving-force approximation improved its performance for the long-term kinetics. Multicomponent adsorption equilibria of chlorophenols on granular activated carbon was investigated in the micromolar equilibrium concentration range. The Langmuir competitive and Ideal Adsorbed Solution (IAS) models were tested for their performance on the three binary systems of pentachlorophenol/2,4,6-trichlorophenol, 2,4,6-trichlorophenol/2,4-dichlorophenol, and 2,4-dichlorophenol/4-chlorophenol, and the tertiary system of 2,4,6-trichlorophenol/2,4-dichlorophenol/4-chlorophenol, and found to fail to predict the two-component adsorption equilibria of the former two binary systems and the tertiary system.

  11. Effect of aging process on adsorption of diethyl phthalate in soils amended with bamboo biochar.

    PubMed

    Zhang, Xiaokai; Sarmah, Ajit K; Bolan, Nanthi S; He, Lizhi; Lin, Xiaoming; Che, Lei; Tang, Caixian; Wang, Hailong

    2016-01-01

    Biochar is a carbonaceous sorbent and can be used as a potential material to reduce the bioavailability of organic pollutants in contaminated soils. In the present study, the adsorption and desorption of diethyl phthalate (DEP) onto soils amended with bamboo biochar was investigated with a special focus on the effect of biochar application rates and aging conditions on the adsorption capacity of the soils. Biochar amendment significantly enhanced the soil adsorption of DEP that increased with increasing application rates of biochar. However, the adsorption capacity decreased by two aging processes (alternating wet and dry, and constantly moist). In the soil with low organic carbon (OC) content, the addition of 0.5% biochar (without aging) increased the adsorption by nearly 98 times compared to the control, and exhibited the highest adsorption capacity among all the treatments. In the soil with high OC content, the adsorption capacity in the treatment of 0.5% biochar without aging was 3.5 and 3 times greater than those of the treatments of biochar aged by alternating wet and dry, and constantly moist, respectively. Moreover, constantly moist resulted in a greater adsorption capacity than alternating wet and dry treatments regardless of biochar addition. This study revealed that biochar application enhanced soil sorption of DEP, however, the enhancement of the adsorption capacity was dependent on the soil organic carbon levels, and aging processes of biochar. PMID:26004250

  12. Adsorptive Removal and Adsorption Kinetics of Fluoroquinolone by Nano-Hydroxyapatite

    PubMed Central

    Chen, Yajun; Lan, Tao; Duan, Lunchao; Wang, Fenghe; Zhao, Bin; Zhang, Shengtian; Wei, Wei

    2015-01-01

    Various kinds of antibiotics, especially fluoroquinolone antibiotics (FQs) have been widely used for the therapy of infectious diseases in human and livestock. For their poorly absorbed by living organisms, large-scale misuse or abuse of FQs will foster drug resistance among pathogenic bacteria, as well as a variety of environmental problems when they were released in the environment. In this work, the adsorption properties of two FQs, namely norfloxacin (NOR) and ciprofloxacin (CIP), by nano-hydroxyapatite (n-HAP) were studied by batch adsorption experiments. The adsorption curves of FQs by n-HAP were simulated by Langmuir and Freundlich isotherms. The results shown that NOR and CIP can be adsorbed effectively by the adsorbent of n-HAP, and the adsorption capacity of FQs increase with increasing dosage of n-HAP. The optimum dosage of n-HAP for FQs removal was 20 g·L-1, in which the removal efficiencies is 51.6% and 47.3%, and an adsorption equilibrium time is 20 min. The maximum removal efficiency occurred when pH is 6 for both FQs. The adsorption isotherm of FQs fits well for both Langmuir and Freundlich equations. The adsorption of both FQs by n-HAP follows second-order kinetics. PMID:26698573

  13. Study the adsorption of phenol from aqueous solution on hydroxyapatite nanopowders.

    PubMed

    Lin, Kaili; Pan, Jiayong; Chen, Yiwei; Cheng, Rongming; Xu, Xuecheng

    2009-01-15

    In this study, the hydroxyapatite (HAp) nanopowders prepared by chemical precipitation method were used as the adsorbent, and the potential of HAp nanopowders for phenol adsorption from aqueous solution was studied. The effect of contact time, initial phenol concentration, pH, adsorbent dosage, solution temperature and adsorbent calcining temperature on the phenol adsorption, and the adsorption kinetic, equilibrium and thermodynamic parameters were investigated. The results showed that the HAp nanopowders possessed good adsorption ability to phenol. The adsorption process was fast, and it reached equilibrium in 2h of contact. The initial phenol concentration, pH and the adsorbent calcining temperature played obvious effects on the phenol adsorption capacity onto HAp nanopowders. Increase in the initial phenol concentration could effectively increase the phenol adsorption capacity. At the same time, increase in the pH to high-acidity or to high-alkalinity also resulted in the increase in the phenol adsorption capacity. Increase in the HAp dosage could effectively increase the phenol adsorption percent. However, the higher calcining temperature of HAp nanopowders could obviously decrease the adsorption capacity. The maximum phenol adsorption capacity was obtained as 10.33mg/g for 400mg/L initial phenol concentrations at pH 6.4 and 60 degrees C. The adsorption kinetic and the isotherm studies showed that the pseudo-second-order model and the Freundlich isotherm were the best choices to describe the adsorption behaviors. The thermodynamic parameters suggested that the adsorption of phenol onto HAp was physisorption, spontaneous and endothermic in nature. PMID:18573599

  14. Impact of salinity and dispersed oil on adsorption of dissolved aromatic hydrocarbons by activated carbon and organoclay.

    PubMed

    Younker, Jessica M; Walsh, Margaret E

    2015-12-15

    Adsorption capacity of phenol and naphthalene by powdered activated carbon (PAC), a commercial organoclay (OC) and a lab synthesized organoclay (BTMA) was studied using batch adsorption experiments under variable feed water quality conditions including single- and multi- solute conditions, fresh water, saline water and oily-and-saline water. Increasing salinity levels was found to reduce adsorption capacity of OC, likely due to destabilization, aggregation and subsequent removal of organoclay from the water column, but did not negatively impact adsorption capacity of PAC or BTMA. Increased dispersed oil concentrations were found to reduce the surface area of all adsorbents. This decreased the adsorption capacity of PAC for both phenol and naphthalene, and reduced BTMA adsorption of phenol, but did not negatively affect naphthalene removals by either organoclay. The presence of naphthalene as a co-solute significantly reduced phenol adsorption by PAC, but had no impact on organoclay adsorption. These results indicated that adsorption by PAC occurred via a surface adsorption mechanism, while organoclay adsorption occurred by hydrophobic or pi electron interactions. In general, PAC was more sensitive to changes in water quality than either of the organoclays evaluated in this study. However, PAC exhibited a higher adsorption capacity for phenol and naphthalene compared to both organoclays even in adverse water quality conditions. PMID:26259095

  15. Comparison of activation media and pyrolysis temperature for activated carbons development by pyrolysis of potato peels for effective adsorption of endocrine disruptor bisphenol-A.

    PubMed

    Arampatzidou, Anastasia C; Deliyanni, Eleni A

    2016-03-15

    Activated carbon prepared from potato peels, a solid waste by product has been studied for the adsorption of an endocrine disruptor, Bisphenol-A, from aqueous solutions. The potato peels biomass was activated with H3PO4, KOH and ZnCl2 in order the effect of the activation agent to be evaluated. The activated biomass was carbonized at 400, 600 and/or 800 °C in order the effect of carbonization temperature on the texture, surface chemistry and adsorption properties to be found. The activated carbons prepared were characterized by nitrogen adsorption, Scanning Electron Microscope, thermal analysis and Fourier Transform Infrared Spectroscopy. Equilibrium adsorption data followed both Langmuir and Freundlich isotherms. Adsorption followed second order rate kinetics. The adsorption capacity calculated from the Langmuir isotherm was found 454.62 mg g(-1) at an initial pH 3 at 25 °C for the phosphoric acid activated carbon carbonized at 400 °C that proved to be the best adsorbent. PMID:26707777

  16. Effect of DOM Size on Organic Micropollutant Adsorption by GAC.

    PubMed

    Kennedy, Anthony M; Summers, R Scott

    2015-06-01

    Granular activated carbon (GAC) adsorption of the micropollutants 2-methylisoborneol (MIB) and warfarin (WFN) at ng/L levels was investigated in five waters with isolated natural dissolved organic matter (DOM) held at a constant dissolved organic carbon concentration. Each water was evaluated for competitive adsorption effects based on the pretreatment of ultrafiltration, coagulation, and additional background micropollutants. Using the breakthrough with unfractionated DOM as a baseline, on average, the water with lower molecular weight (MW) DOM decreased MIB and WFN adsorption capacity by 59%, whereas the water with higher MW DOM increased MIB and WFN adsorption capacity by 64%. All waters showed similar decreasing MIB and WFN adsorption capacity with increasing empty bed contact time (EBCT), with more dramatic effects seen for the more strongly adsorbing WFN. On average, MIB and WFN adsorption kinetics were two times slower in the water with higher MW DOM compared to the water with lower MW DOM, as described by the intraparticle pore diffusion tortuosity. Increased adsorption competition from 27 micropollutants other than MIB and WFN at environmentally relevant concentrations had little to no effect on MIB and WFN breakthrough behavior. Any competitive effect from background micropollutants became indiscernible at longer EBCTs. PMID:25955134

  17. Adsorption of mercury on laterite from Guizhou Province, China.

    PubMed

    Yu, Xiaohong; Zhu, Lijun; Guo, Baiwei; He, Shouyang

    2008-01-01

    The adsorption behaviors of Hg(II) on laterite from Guizhou Province, China, were studied and the adsorption mechanism was discussed. The results showed that different mineral compositons in the laterite will cause differences in the adsorption capacity of laterite to Hg(II). Illite and non-crystalloids are the main contributors to enhancing the adsorption capacity of laterite to Hg(II). The pH of the solution is an important factor affecting the adsorption of Hg(II) on laterite. The alkalescent environment (pH 7-9) is favorable to the adsorption of Hg(II). The amount of adsorbed Hg(II) increases with increasing pH. When the pH reaches a certain value, the amount of the adsorbed Hg(II) will reach the maximum level. The amount of adsorbed Hg(II) decreases with increasing pH. The optimal pHs of laterite and kaolinite are 9 and 8, respectively. The optimal initial concentrations of Hg(II) on laterite and kaolinite are 250 and 200 microg/ml, respectively. The adsorption isotherms were described by the Langmuir model. The adsorption of Hg(II) on laterite is a quick process while that of Hg(II) on kaolinite is a slow reaction. Laterite from Guizhou Province is a promising environmental material which can be used in the removal of Hg(II) from wastewater. PMID:19202872

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

    PubMed

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

    2014-07-30

    The uptake of amitriptyline (AMI) from aqueous environment by Ca-montmorillonite (SAz-2) was studied in a batch system under different physicochemical conditions. The adsorbent was characterized by X-ray diffraction and Fourier transform infrared (FTIR) analyses. The AMI adsorption on SAz-2 obeyed the Langmuir isotherm with a capacity of 330mg/g (1.05mmol/g) at pH 6-7. The adsorption kinetics was fast, almost reaching equilibrium in 2h, and followed a pseudo-second-order kinetic model. Desorption of exchangeable cations correlated with the AMI adsorption well, indicating that cation exchange was the major mechanism. X-ray diffraction patterns showing significant expansions of the d001 spacing and characteristic FTIR band shifts toward higher frequencies after AMI adsorption onto SAz-2 indicated that the adsorbed AMI molecules were intercalated into the interlayers of the mineral. Thermodynamic parameters based on partitioning coefficients suggested that the AMI adsorption was an endothermic physisorption at high adsorption levels. At low and higher AMI adsorption levels, the intercalated AMI molecules take a horizontal monolayer and bilayer conformation, respectively. The higher adsorption capacity suggested that SAz-2 could be a good candidate to remove AMI from wastewater and would be an important environmental sink for the fate and transport of AMI in soils and groundwater. PMID:24373983

  19. Knudsen heat capacity

    SciTech Connect

    Babac, Gulru; Reese, Jason M.

    2014-05-15

    We present a “Knudsen heat capacity” as a more appropriate and useful fluid property in micro/nanoscale gas systems than the constant pressure heat capacity. At these scales, different fluid processes come to the fore that are not normally observed at the macroscale. For thermodynamic analyses that include these Knudsen processes, using the Knudsen heat capacity can be more effective and physical. We calculate this heat capacity theoretically for non-ideal monatomic and diatomic gases, in particular, helium, nitrogen, and hydrogen. The quantum modification for para and ortho hydrogen is also considered. We numerically model the Knudsen heat capacity using molecular dynamics simulations for the considered gases, and compare these results with the theoretical ones.

  20. EVALUATING CAPACITIES OF GAC PRELOADED WITH NATURAL WATER

    EPA Science Inventory

    Adsorption studies are conducted to determine how preloading a natural groundwater onto GAC affects the adsorption of cis-1,2-dichloroexthene in small-scale and pilot-scale columns. Capacities are determined from batch-isotherm tests, microcolumns, and pilot columns, which are p...

  1. The adsorption mechanism of nortryptiline on C18-bonded discovery

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2005-08-01

    The adsorption isotherms of an ionizable compound, nortriptyline, were accurately measured by frontal analysis (FA) on a C{sub 18}-Discovery column, first without buffer (in an aqueous solution of acetonitrile at 15%, v/v of ACN), then with a buffer (in 28%, v/v ACN solution). The buffers were aqueous solutions containing 20 mM of formic acid or a phosphate buffer at pH 2.70. The linear range of the isotherm could not be reached with the non-buffered mobile phase using a dynamic range larger than 40,000 (from 1.2 x 10{sup -3} g/L to 50 g/L). With a 20 mM buffer in the liquid phase, the isotherm is linear for concentrations of nortriptyline inferior to 10{sup -3} g/L (or 3 {micro} mol/L). The adsorption energy distribution (AED) was calculated to determine the heterogeneity of the adsorption process. AED and FA were consistent and lead to a trimodal distribution. A tri-Moreau and a tri-Langmuir isotherm models accounted the best for the adsorption of nortriptyline without and with buffer, respectively. The nature of the buffer affects significantly the middle-energy sites while the properties of the lowest and highest of the three types of energy sites are almost unchanged. The desorption profiles of nortriptyline show some anomalies in relation with the formation of a complex multilayer adsorbed phase of acetonitrile whose excess isotherm was measured by the minor disturbance method. The C{sub 18}-Discovery column has about the same total saturation capacity, around 200 g of nortriptyline per liter of adsorbent (or 116 mg/g), with or without buffer. About 98-99% of the available surface consists in low energy sites. The coexistence of these different types of sites on the surface solves the McCalley's enigma, that the column efficiency begins to drop rapidly when the analyte concentration reaches values that are almost one hundred times lower than those that could be predicted from the isotherm data acquired under the same experimental conditions. Due to the

  2. Novel nano bearings constructed by physical adsorption

    PubMed Central

    Zhang, Yongbin

    2015-01-01

    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. PMID:26412488

  3. Novel nano bearings constructed by physical adsorption.

    PubMed

    Zhang, Yongbin

    2015-01-01

    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. PMID:26412488

  4. Adsorption of tetrahydrothiophene (THT) onto soils

    NASA Astrophysics Data System (ADS)

    Juriga, Martin; Kubinec, Róbert; Rajzinger, Ján; Jelemenský, Karol; Gužela, Štefan

    2014-08-01

    Adsorption is one of the major industrial separation technique nowadays. Although adsorption is most commonly used as a separation method, in some cases cause harmful and undesirable effects such as capture odorant from natural gas onto soil. In the event of an accident, the gas can leak from pipes in two ways - either directly into the surrounding air, or the soil where the odorant can be mostly absorbed depending of type of soil, water content and temperature. Design of experimental apparatus for measurement of breakthrough curves is studied in detail. Alternative arrangement of experimental apparatus, calibration of measuring devices, method of measurement and processing the data are narrowly discussed. Moreover, experimental measurements of breakthrough curves are presented. The actual measurement was made to identify the equilibrium adsorption capacity of THT (tetrahydrothiophene) onto soils. Experimental data were evaluated using Linear, Freundlich, Langmuir and Koble-Corrigan model.

  5. Novel nano bearings constructed by physical adsorption

    NASA Astrophysics Data System (ADS)

    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.

  6. CO2 adsorption on chemically modified activated carbon.

    PubMed

    Caglayan, Burcu Selen; Aksoylu, A Erhan

    2013-05-15

    CO2 adsorption capacity of a commercial activated carbon was improved by using HNO3 oxidation, air oxidation, alkali impregnation and heat treatment under helium gas atmosphere. The surface functional groups produced were investigated by diffuse reflectance infrared Fourier transform spectrometer (DRIFTS). CO2 adsorption capacities of the samples were determined by gravimetric analyses for 25-200°C temperature range. DRIFTS studies revealed the formation of carboxylic acid groups on the HNO3 oxidized adsorbents. Increased aromatization and uniform distribution of the Na particles were observed on the samples prepared by Na2CO3 impregnation onto HNO3 oxidized AC support. The adsorption capacities of the nonimpregnated samples were increased by high temperature helium treatments or by increasing the adsorption temperature; both leading to decomposition of surface oxygen groups, forming sites that can easily adsorb CO2. The adsorption capacity loss due to cyclic adsorption/desorption procedures was overcome with further surface stabilization of Na2CO3 modified samples with high temperature He treatments. With Na2CO3 impregnation the mass uptakes of the adsorbents at 20 bars and 25 °C were improved by 8 and 7 folds and at 1 bar were increased 15 and 16 folds, on the average, compared to their air oxidized and nitric acid oxidized supports, respectively. PMID:23500788

  7. Mercury adsorption properties of sulfur-impregnated adsorbents

    USGS Publications Warehouse

    Hsi, N.-C.; Rood, M.J.; Rostam-Abadi, M.; Chen, S.; Chang, R.

    2002-01-01

    Carbonaceous and noncarbonaceous adsorbents were impregnated with elemental sulfur to evaluate the chemical and physical properties of the adsorbents and their equilibrium mercury adsorption capacities. Simulated coal combustion flue gas conditions were used to determine the equilibrium adsorption capacities for Hg0 and HgCl2 gases to better understand how to remove mercury from gas streams generated by coal-fired utility power plants. Sulfur was deposited onto the adsorbents by monolayer surface deposition or volume pore filling. Sulfur impregnation increased the total sulfur content and decreased the total and micropore surface areas and pore volumes for all of the adsorbents tested. Adsorbents with sufficient amounts of active adsorption sites and sufficient microporous structure had mercury adsorption capacities up to 4,509 ??g Hg/g adsorbent. Elemental sulfur, organic sulfur, and sulfate were formed on the adsorbents during sulfur impregnation. Correlations were established with R2>0.92 between the equilibrium Hg0/HgCl2 adsorption capacities and the mass concentrations of elemental and organic sulfur. This result indicates that elemental and organic sulfur are important active adsorption sites for Hg0 and HgCl2.

  8. Adsorption of lead onto smectite from aqueous solution.

    PubMed

    Mhamdi, M; Galai, H; Mnasri, N; Elaloui, E; Trabelsi-Ayadi, M

    2013-03-01

    The purpose of this research is to study the effect of a new method of adsorption using membrane filtration to determine the maximum amount of lead adsorbed by clay and investigate the behavior of the clay after adsorption of the said metal. Treatment of wastewater contaminated with heavy metals depends on the characteristics of the effluent, the amount of final discharge, the cost of treatment, and the compatibility of the treatment process. The process of adsorption of heavy metals by clays may be a simple, selective, and economically viable alternative to the conventional physical-chemical treatment. This is justified by the importance of the surface developed by this material, the presence of negative charges on the said surface, the possibility of ion exchange taking place, and its wide availability in nature. The removal of lead from wastewater was studied by using the adsorption technique and using clay as the adsorbent. A method was optimized for adsorption through a membrane approaching natural adsorption. This new method is simple, selective, and the lead adsorption time is about 3 days. The various properties of clay were determined. It was observed that the cation exchange capacity of the clay was 56 meq/100 g of hydrated clay for the raw sample and 82 meq/100 g for the purified sample. The total surface area determined by the methylene blue method was equal to 556 and 783 m(2)/g for the raw and purified samples, respectively. The adsorption kinetics depends on several parameters. The Pb(II) clay, obeys the Langmuir, Freundlich, and the Elovich adsorption isotherms with high regression coefficients. The use of this adsorbent notably decreases the cost of treatment. It was concluded that clay shows a strong adsorption capacity on Pb(II), the maximum interaction occurring with purified clay treated at high concentration of lead. It is proposed that this adsorption through a membrane be extended for the treatment of effluents containing other metals. PMID

  9. ARSENIC TREATMENT BY ADSORPTIVE TECHNOLOGY

    EPA Science Inventory

    Presentation will discuss the removal of arsenic from drinking water using the adsorptive media treatment process. Fundamental information is provided on the design and operation of adsorptive media technology including the selection of the adsorptive media. The information cites...

  10. A Simple Adsorption Experiment

    ERIC Educational Resources Information Center

    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…

  11. An aminopyrimidine-functionalized cage-based metal-organic framework exhibiting highly selective adsorption of C2H2 and CO2 over CH4.

    PubMed

    Jiao, Jingjing; Dou, Li; Liu, Huimin; Chen, Fengli; Bai, Dongjie; Feng, Yunlong; Xiong, Shunshun; Chen, De-Li; He, Yabing

    2016-09-14

    There has been considerable interest in adsorptive separation of C2H2/CH4 and CO2/CH4 gas mixtures due to its industrial significance and scientific challenge. In this work, we have designed and synthesized a bent diisophthalate ligand functionalized with aminopyrimidine groups, and constructed via a solvothermal reaction, a porous copper-based framework. Single-crystal X-ray diffraction studies show that the framework is a three-dimensional network containing three different types of polyhedral nanocages, which are stacked together to form two distinct types of one-dimensional channels along the crystallographic c axis. The compound after activation shows exceptionally high C2H2 and CO2 uptakes of 211 and 120 cm(3) (STP) g(-1) at 295 K and 1 atm, as well as impressive adsorption selectivities towards C2H2 and CO2 over CH4. High C2H2 and CO2 uptake capacities as well as significant adsorption selectivities of C2H2 and CO2 over CH4 imply potential applications in the adsorptive separation and purification of C2H2/CH4 and CO2/CH4 gas mixtures, which have been verified by column breakthrough experiments. Several important binding sites for C2H2 and CO2 in ZJNU-54 were revealed by quantum chemical calculations, demonstrating that the organic linkers in ZJNU-54 form unique structures that facilitate the adsorption of C2H2, while the amine groups and the Lewis basic pyrimidine-ring nitrogen sites in the organic linker improve the adsorption energies for CO2, finally leading to the increase of adsorption capacities for these two gas molecules. This work provides an efficient strategy for incorporating specific functional groups into cage-based MOFs for generating new adsorbents for highly selective gas storage and separation. PMID:27483189

  12. Adsorption of aniline and toluidines on montmorillonite

    SciTech Connect

    Essington, M.E. )

    1994-09-01

    Bentonite clay liners are commonly employed to mitigate the movement of contaminants from waste disposal sites. In order to assess the ability of clay liner material to restrict the mobility of amine compounds under a variety of chemical conditions and to further elucidate amine adsorption characteristics, the adsorption of aniline and o-, m-, and p-toluidine on Ca[sup 2+]- and K[sup +]-saturated Wyoming bentonite (SWy-1) was investigated. Adsorption experiments were performed under conditions of varied pH and ionic environment. Amine adsorption on montmorillonite is pH dependent. Maximum amine adsorption occurs when solution pH is approximately equal to the pK[sub a] of the anilinium ion deprotonation reaction (pH 4.45-5.08). An amine adsorption envelope results from the combined influence of increasing anilinium ion and anilinium-aniline complex formation (as pH decreases to the pK[sub a]) and amine competition with H[sup +] for surface sites, decreasing anilinium-aniline complex concentration, and decreasing aniline available for water bridging with exchangeable Ca[sup 2+] and K[sup +] (as solution pH decreases below the pK[sub a]). For any given amine, maximum adsorption increases with decreasing ionic strength. Maximum amine adsorption is greater in the Ca[sup 2+] systems than in the K[sup +] systems at equivalent cation charge and reflects the formation of an amine water bridge with the exchangeable Ca[sup 2+]. Amine adsorption is also greater in chloride systems compared with sulfate systems at comparable cation concentrations, possibly due to the formation of aqueous anilinium-sulfate complexes. The amine compounds are retained mainly by bentonite through a cation exchange process, the capacity of the clay to adsorb the amine compounds being a significant percentage of the exchange capacity at the pK[sub a]. However, amine retention decreases with increasing pH and is minimal at solution pH values greater than 7. 19 refs., 6 figs.

  13. Modeling Adsorption Processes: Issues in Uncertainty, Scaling, and Prediction

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Adsorption of contaminant species to mineral surfaces is largely responsible for the retardation of radionuclides in the subsurface environment. However despite much research effort, the advancement of models that can be used to successfully calculate or predict adsorption is still somewhat limited...

  14. Adsorption kinetics and thermodynamics of acid Bordeaux B from aqueous solution by graphene oxide/PAMAMs.

    PubMed

    Zhang, Fan; He, Shengfu; Zhang, Chen; Peng, Zhiyuan

    2015-01-01

    Graphene oxide/polyamidoamines dendrimers (GO/PAMAMs) composites were synthesized via modifying GO with 2.0 G PAMAM. The adsorption behavior of the GO/PAMAMs for acid Bordeaux B (ABB) was studied and the effects of media pH, adsorption time and initial ABB concentration on adsorption capacity of the adsorbent were investigated. The optimum pH value of the adsorption of ABB onto GO/PAMAMs was 2.5. The maximum adsorption capacity increased from 325.78 to 520.83 mg/g with the increase in temperature from 298 to 328 K. The equilibrium data followed the Langmuir isotherm model better than the Freundlich model. The kinetic study illustrated that the adsorption of ABB onto GO/PAMAMs fit the pseudo-second-order model. The thermodynamic parameters indicated that the adsorption process was physisorption, and also an endothermic and spontaneous process. PMID:26398038

  15. Fluorocarbon adsorption in hierarchical porous frameworks.

    PubMed

    Motkuri, Radha Kishan; Annapureddy, Harsha V R; Vijaykumar, M; Schaef, H Todd; Martin, Paul F; McGrail, B Peter; Dang, Liem X; Krishna, Rajamani; Thallapally, Praveen K

    2014-01-01

    Metal-organic frameworks comprise an important class of solid-state materials and have potential for many emerging applications such as energy storage, separation, catalysis and bio-medical. Here we report the adsorption behaviour of a series of fluorocarbon derivatives on a set of microporous and hierarchical mesoporous frameworks. The microporous frameworks show a saturation uptake capacity for dichlorodifluoromethane of >4 mmol g(-1) at a very low relative saturation pressure (P/Po) of 0.02. In contrast, the mesoporous framework shows an exceptionally high uptake capacity reaching >14 mmol g(-1) at P/Po of 0.4. Adsorption affinity in terms of mass loading and isosteric heats of adsorption is found to generally correlate with the polarizability and boiling point of the refrigerant, with dichlorodifluoromethane > chlorodifluoromethane > chlorotrifluoromethane > tetrafluoromethane > methane. These results suggest the possibility of exploiting these sorbents for separation of azeotropic mixtures of fluorocarbons and use in eco-friendly fluorocarbon-based adsorption cooling. PMID:25006832

  16. Fluorocarbon adsorption in hierarchical porous frameworks

    NASA Astrophysics Data System (ADS)

    Motkuri, Radha Kishan; Annapureddy, Harsha V. R.; Vijaykumar, M.; Schaef, H. Todd; Martin, Paul F.; McGrail, B. Peter; Dang, Liem X.; Krishna, Rajamani; Thallapally, Praveen K.

    2014-07-01

    Metal-organic frameworks comprise an important class of solid-state materials and have potential for many emerging applications such as energy storage, separation, catalysis and bio-medical. Here we report the adsorption behaviour of a series of fluorocarbon derivatives on a set of microporous and hierarchical mesoporous frameworks. The microporous frameworks show a saturation uptake capacity for dichlorodifluoromethane of >4 mmol g-1 at a very low relative saturation pressure (P/Po) of 0.02. In contrast, the mesoporous framework shows an exceptionally high uptake capacity reaching >14 mmol g-1 at P/Po of 0.4. Adsorption affinity in terms of mass loading and isosteric heats of adsorption is found to generally correlate with the polarizability and boiling point of the refrigerant, with dichlorodifluoromethane >chlorodifluoromethane >chlorotrifluoromethane >tetrafluoromethane >methane. These results suggest the possibility of exploiting these sorbents for separation of azeotropic mixtures of fluorocarbons and use in eco-friendly fluorocarbon-based adsorption cooling.

  17. Fluorocarbon adsorption in hierarchical porous frameworks

    SciTech Connect

    Motkuri, RK; Annapureddy, HVR; Vijaykumar, M; Schaef, HT; Martin, PF; McGrail, BP; Dang, LX; Krishna, R; Thallapally, PK

    2014-07-09

    Metal-organic frameworks comprise an important class of solid-state materials and have potential for many emerging applications such as energy storage, separation, catalysis and bio-medical. Here we report the adsorption behaviour of a series of fluorocarbon derivatives on a set of microporous and hierarchical mesoporous frameworks. The microporous frameworks show a saturation uptake capacity for dichlorodifluoromethane of >4 mmol g(-1) at a very low relative saturation pressure (P/P-o) of 0.02. In contrast, the mesoporous framework shows an exceptionally high uptake capacity reaching >14 mmol g(-1) at P/P-o of 0.4. Adsorption affinity in terms of mass loading and isosteric heats of adsorption is found to generally correlate with the polarizability and boiling point of the refrigerant, with dichlorodifluoromethane >chlorodifluoromethane >chlorotrifluoromethane >tetrafluoromethane >methane. These results suggest the possibility of exploiting these sorbents for separation of azeotropic mixtures of fluorocarbons and use in eco-friendly fluorocarbon-based adsorption cooling.

  18. Poliovirus Adsorption by 34 Minerals and Soils

    PubMed Central

    Moore, Rebecca S.; Taylor, Dene H.; Sturman, Lawrence S.; Reddy, Michael M.; Fuhs, G. Wolfgang

    1981-01-01

    The adsorption of radiolabeled infectious poliovirus type 2 by 34 well-defined soils and mineral substrates was analyzed in a synthetic freshwater medium containing 1 mM CaCl2 and 1.25 mM NaHCO3 at pH 7. In a model system, adsorption of poliovirus by Ottawa sand was rapid and reached equilibrium within 1 h at 4°C. Near saturation, the adsorption could be described by the Langmuir equation; the apparent surface saturation was 2.5 × 106 plaque-forming units of poliovirus per mg of Ottawa sand. At low surface coverage, adsorption was described by the Freundlich equation. The soils and minerals used ranged from acidic to basic and from high in organic content to organic free. The available negative surface charge on each substrate was measured by the adsorption of a cationic polyelectrolyte, polydiallyldimethylammonium chloride. Most of the substrates adsorbed more than 95% of the virus. In general, soils, in comparison with minerals, were weak adsorbents. Among the soils, muck and Genesee silt loam were the poorest adsorbents; among the minerals, montmorillonite, glauconite, and bituminous shale were the least effective. The most effective adsorbents were magnetite sand and hematite, which are predominantly oxides of iron. Correlation coefficients for substrate properties and virus adsorption revealed that the elemental composition of the adsorbents had little effect on poliovirus uptake. Substrate surface area and pH, by themselves, were not significantly correlated with poliovirus uptake. A strong negative correlation was found between poliovirus adsorption and both the contents of organic matter and the available negative surface charge on the substrates as determined by their capacities for adsorbing the cationic polyelectrolyte, polydiallyldimethylammonium chloride. PMID:6274259

  19. Adsorption behavior of heavy metals on biomaterials.

    PubMed

    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

  20. Selective adsorption mechanisms of antilipidemic and non-steroidal anti-inflammatory drug residues on functionalized silica-based porous materials in a mixed solute.

    PubMed

    Suriyanon, Nakorn; Permrungruang, Jutima; Kaosaiphun, Jidanan; Wongrueng, Aunnop; Ngamcharussrivichai, Chawalit; Punyapalakul, Patiparn

    2015-10-01

    The selective adsorption mechanisms of naproxen (NAP), acetaminophen (ACT), and clofibric acid (CFA) on silica-based porous materials were examined by single and mixed-batch adsorption. Effects of the types and densities of surface functional groups on adsorption capacities were determined, including the role of hydrophobic and hydrophilic dissolved organic matters (DOMs). Hexagonal mesoporous silica (HMS), superparamagnetic HMS (HMS-SP) and SBA-15 were functionalized and applied as adsorbents. Compared with powdered activated carbon (PAC), amine-functionalized HMS had a better adsorption capacity for CFA, but PAC possessed a higher adsorption capacity for the other pharmaceuticals than HMS and its two derivatives. In contrast to PAC, the adsorption capacity of the mesoporous silicas varied with the solution pH, being highest at pH 5. Electrostatic interactions and hydrogen bonding were found to be the main mechanisms. Increase in grafted amine group density on silica surfaces can enhance the CFA adsorption capacity. Further, hydrophilic DOM can decrease CFA adsorption capacities on amino-grafted adsorbents by adsorption site competition, while hydrophobic DOM can interfere with CFA adsorption by the interaction between hydrophobic DOM and CFA. Finally, in a competitive adsorption study, the adsorption capacity of hydrophilic adsorbents for acidic pharmaceuticals varied with their pKa values. PMID:26025186

  1. Optimization of salt adsorption rate in membrane capacitive deionization.

    PubMed

    Zhao, R; Satpradit, O; Rijnaarts, H H M; Biesheuvel, P M; van der Wal, A

    2013-04-01

    Membrane capacitive deionization (MCDI) is a water desalination technique based on applying a cell voltage between two oppositely placed porous electrodes sandwiching a spacer channel that transports the water to be desalinated. In MCDI, ion-exchange membranes are positioned in front of each porous electrode to prevent co-ions from leaving the electrode region during ion adsorption, thereby enhancing the salt adsorption capacity. MCDI can be operated at constant cell voltage (CV), or at a constant electrical current (CC). In this paper, we present both experimental and theoretical results for desalination capacity and rate in MCDI (both in the CV- and the CC-mode) as function of adsorption/desorption time, salt feed concentration, electrical current, and cell voltage. We demonstrate how by varying each parameter individually, it is possible to systematically optimize the parameter settings of a given system to achieve the highest average salt adsorption rate and water recovery. PMID:23395310

  2. A review on chitosan-based adsorptive membranes.

    PubMed

    Salehi, Ehsan; Daraei, Parisa; Arabi Shamsabadi, Ahmad

    2016-11-01

    Membrane adsorbents have emerged as powerful and attractive tools for the removal of hazardous materials such as dyes and heavy metal ions, mainly in trace amounts, from water resources. Among membrane adsorbents, those prepared from or modified with chitosan biopolymer and its derivatives are cases of interest because of chitosan advantages including biocompatibility, biodegradability, nontoxicity, reactivity, film and fiber forming capacity and favorable hydrophilicity. This review is oriented to provide a framework for better insight into fabrication methods and applications of chitosan-based adsorptive membranes. Critical aspects including thermokinetic analyses of adsorption and regeneration capacity of the membrane adsorbents have been also overviewed. Future of chitosan-based adsorptive membranes might include efforts for the improvement of mechanical stability and reusability and also most targeted application of appropriate copolymers as well as nanostructures in preparing high performance adsorptive membranes. PMID:27516289

  3. Adsorption of aqueous copper on peanut hulls

    NASA Astrophysics Data System (ADS)

    Davis, Kanika Octavia

    , scanning electron microscopy images coupled with energy dispersive X-ray spectroscopy showed that the percentage of copper on the modified hulls (2.5 %) was greater than on the unmodified hulls (1.6 %). This study concluded that the adsorption of copper using peanut hulls is a potential method for wastewater treatment and delignification and oxidation of the hulls increases the adsorption capacity approximately three-fold.

  4. First-principles analysis of defect-mediated Li adsorption on graphene.

    PubMed

    Yildirim, Handan; Kinaci, Alper; Zhao, Zhi-Jian; Chan, Maria K Y; Greeley, Jeffrey P

    2014-12-10

    To evaluate the possible utility of single layer graphene for applications in Li ion batteries, an extensive series of periodic density functional theory (DFT) calculations are performed on graphene sheets with both point and extended defects for a wide range of lithium coverages. Consistent with recent reports, it is found that Li adsorption on defect-free single layer graphene is not thermodynamically favorable compared to bulk metallic Li. However, graphene surfaces activated by defects are generally found to bind Li more strongly, and the interaction strength is sensitive to both the nature of the defects and their densities. Double vacancy defects are found to have much stronger interactions with Li as compared to Stone-Wales defects, and increasing defect density also enhances the interaction of the Stone-Wales defects with Li. Li interaction with one-dimensional extended defects on graphene is additionally found to be strong and leads to increased Li adsorption. A rigorous thermodynamic analysis of these data establishes the theoretical Li storage capacities of the defected graphene structures. In some cases, these capacities are found to approach, although not exceed, those of graphite. The results provide new insights into the fundamental physics of adsorbate interactions with graphene defects and suggest that careful defect engineering of graphene might, ultimately, provide anode electrodes of suitable capacity for lithium ion battery applications. PMID:25394787

  5. Microscopic Theory of Hysteretic Hydrogen Adsorption in Nanoporous Materials

    SciTech Connect

    Kang, J.; Wei, S. H.; Kim, Y. H.

    2010-01-01

    Understanding gas adsorption confined in nanoscale pores is a fundamental issue with broad applications in catalysis and gas storage. Recently, hysteretic H{sub 2} adsorption was observed in several nanoporous metal-organic frameworks (MOFs). Here, using first-principles calculations and simulated adsorption/desorption isotherms, we present a microscopic theory of the enhanced adsorption hysteresis of H{sub 2} molecules using the MOF Co(1,4-benzenedipyrazolate) [Co(BDP)] as a model system. Using activated H{sub 2} diffusion along the small-pore channels as a dominant equilibration process, we demonstrate that the system shows hysteretic H{sub 2} adsorption under changes of external pressure. For a small increase of temperature, the pressure width of the hysteresis, as well as the adsorption/desorption pressure, dramatically increases. The sensitivity of gas adsorption to temperature changes is explained by the simple thermodynamics of the gas reservoir. Detailed analysis of transient adsorption dynamics reveals that the hysteretic H{sub 2} adsorption is an intrinsic adsorption characteristic in the diffusion-controlled small-pore systems.

  6. Adsorption of 4-n-Nonylphenol and Bisphenol-A on Magnetic Reduced Graphene Oxides: A Combined Experimental and Theoretical Studies.

    PubMed

    Jin, Zhongxiu; Wang, Xiangxue; Sun, Yubing; Ai, Yuejie; Wang, Xiangke

    2015-08-01

    Adsorption of 4-n-nonylphenol (4-n-NP) and bisphenol A (BPA) on magnetic reduced graphene oxides (rGOs) as a function of contact time, pH, ionic strength and humic acid were investigated by batch techniques. Adsorption of 4-n-NP and BPA were independent of pH at 3.0- 8.0, whereas the slightly decreased adsorption was observed at pH 8.0-11.0. Adsorption kinetics and isotherms of 4-n-NP and BPA on magnetic rGOs can be satisfactorily fitted by pseudo-second-order kinetic and Freundlich model, respectively. The maximum adsorption capacities of magnetic rGOs at pH 6.5 and 293 K were 63.96 and 48.74 mg/g for 4-n-NP and BPA, respectively, which were significantly higher than that of activated carbon. Based on theoretical calculations, the higher adsorption energy of rGOs + 4-n-NP was mainly due to π-π stacking and flexible long alkyl chain of 4-n-NP, whereas adsorption of BPA on rGOs was energetically favored by a lying-down configuration due to π-π stacking and dispersion forces, which was further demonstrated by FTIR analysis. These findings indicate that magnetic rGOs is a promising adsorbent for the efficient elimination of 4-n-NP/BPA from aqueous solutions due to its excellent adsorption performance and simple magnetic separation, which are of great significance for the remediation of endocrine-disrupting chemicals in environmental cleanup. PMID:26161689

  7. Adsorption of 2,4,6-trinitrotoluene on carboxylated porous polystyrene microspheres

    NASA Astrophysics Data System (ADS)

    Ye, Zhengfang; Meng, Qingqiang; Lu, Shengtao

    2012-02-01

    Large-pore-size (150 nm) polystyrene (PSt) microspheres were carboxylated with phthalic anhydride (PA) through Friedel-Crafts acetylation to study the adsorption of 2,4,6-trinitrotoluene (TNT) on this material from aqueous solution. The scanning electron microscope (SEM) images and mercury porosimetry measurements (MPM) of the microspheres showed that the pore structure was unchanged during the reaction. High adsorption capacity (11.2 mg g-1 of suction-dried adsorbent) and adsorption rate (33.9 mg g-1 h-1) for TNT were observed during the study. As shown by the adsorption isotherm, the adsorption of TNT on PA-PSt can be described by the Freundlich adsorption equation, indicating heterogeneous adsorption process. On-column adsorption of TNT on PA-PSt and elution indicated that TNT can be completely removed from aqueous solution and condensed into acetone.

  8. Application of activated carbon derived from scrap tires for adsorption of Rhodamine B.

    PubMed

    Li, Li; Liu, Shuangxi; Zhu, Tan

    2010-01-01

    Activated carbon derived from solid hazardous waste scrap tires was evaluated as a potential adsorbent for cationic dye removal. The adsorption process with respect to operating parameters was investigated to evaluate the adsorption characteristics of the activated pyrolytic tire char (APTC) for Rhodamine B (RhB). Systematic research including equilibrium, kinetics and thermodynamic studies was performed. The results showed that APTC was a potential adsorbent for RhB with a higher adsorption capacity than most adsorbents. Solution pH and temperature exert significant influence while ionic strength showed little effect on the adsorption process. The adsorption equilibrium data obey Langmuir isotherm and the kinetic data were well described by the pseudo second-order kinetic model. The adsorption process followed intra-particle diffusion model with more than one process affecting the adsorption process. Thermodynamic study confirmed that the adsorption was a physisorption process with spontaneous, endothermic and random characteristics. PMID:21179969

  9. Adsorption of As(III) and As(V) onto colloidal microparticles of commercial cross-linked polyallylamine (Sevelamer) from single and binary ion solutions.

    PubMed

    Kyzas, George Z; Siafaka, Panoraia I; Kostoglou, Margaritis; Bikiaris, Dimitrios N

    2016-07-15

    This work investigates the removal of arsenic ions in trivalent (As(III)) or pentavalent form (As(V)) from single-component and binary (equal initial ion concentrations) aqueous solutions using commercial cross-linked polyallylamine (namely as Sevelamer) as adsorbent. This is the first work in literature regarding the application of that commercial material as adsorbent for ions. Sevelamer (SVL) is a widely known pharmaceutical compound and the existence of primary and secondary amino groups (with different ratios) in its molecule increases its adsorption potential. For this purpose can be easily proposed as potential sorbent. The adsorption evaluation was based on the pH-effect (optimum pH=6, where As(III) and As(V) removal was 69 and 86%, respectively), isotherms and kinetic curves. The maximum theoretical adsorption capacity (Qm) was 86 and 133mg/g for single-component solutions of As(III) and As(V), respectively. The respective values for binary mixtures of the same concentration (100mg/L) were 84 and 116mg/g, respectively (calculated after fitting to Langmuir-Freundlich isotherm model at 20°C). A novel kinetic interpretation based on the raw experimental kinetics data was also developed. Although adsorption of As(III) and As(V) occurs mainly at different sites, there is an interdependence in their adsorption kinetics. It was found that adsorption from the binary mixtures is a two-stage process. The adsorption mechanism of SVL and arsenic ions interaction was elucidated using FTIR spectroscopy before and after adsorption. SEM images and XRD patterns (the material was amorphous both before and after arsenic adsorption indicating that the mechanism did not alter its physical state) were also taken for the characterization of SVL before and after arsenic adsorption. The adsorption mechanism was mainly attributed to the electrostatic interactions between negatively As ions and positively charged amino groups of SVL. For this reason, As(V) adsorption is higher than

  10. Adsorption of ammonium dinitramide (ADN) from aqueous solutions. 1. Adsorption on powdered activated charcoal.

    PubMed

    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

  11. Adsorption of cadmium by biochar derived from municipal sewage sludge: Impact factors and adsorption mechanism.

    PubMed

    Chen, Tan; Zhou, Zeyu; Han, Rong; Meng, Ruihong; Wang, Hongtao; Lu, Wenjing

    2015-09-01

    Static equilibrium experiments were carried out to investigate the impact factors and the mechanism of cadmium adsorption on biochar derived from municipal sewage sludge. An appropriate dosage of biochar is sufficient; in the experiment, 0.2% is the optimal dosage for the largest removal capacity, while the removal capacity of biochar reduces with the increasing dosage. pH is another dominant factor of the adsorption process. The removal capacity of biochar is lower than 20 mg·g(-1) when the solution initial pH is lower than 2 pH units, comparatively retaining more than 40 mg·g(-1) at the solution initial pH higher than 3 pH units. Temperature has weak influence on the adsorptive performance. The main mechanism of the adsorption process of biochar for cadmium mainly involves (1) surface precipitation by forming insoluble cadmium compounds in alkaline condition, and (2) ion exchange for cadmium with exchangeable cations in the biochar, such as calcium ions. PMID:25966459

  12. Enhanced Li capacity in functionalized graphene: A first principle study with van der Waals correction

    NASA Astrophysics Data System (ADS)

    Chouhan, Rajiv K.; Raghani, Pushpa

    2015-09-01

    We have investigated the adsorption of Li on graphene oxide using density functional theory. We show a novel and simple approach to achieve a positive lithiation potential on epoxy and hydroxyl functionalized graphene, compared to the negative lithiation potential that has been found on prestine graphene. We included the van der Waals correction into the calculation so as to get a better picture of weak interactions. A positive lithiation potential suggests a favorable adsorption of Li on graphene oxide sheets that can lead to an increase in the specific capacity, which in turn can be used as an anode material in Li-batteries. We find a high specific capacity of ˜860 mAhg-1 by functionalizing the graphene sheet. This capacity is higher than the previously reported capacities that were achieved on graphene with high concentration of Stone-Wales (75%) and divacancy (16%) defects. Creating such high density of defects can make the entire system energetically unstable, whereas graphene oxide is a naturally occurring substance.

  13. Synthesis of Fe3O4/Polyacrylonitrile Composite Electrospun Nanofiber Mat for Effective Adsorption of Tetracycline.

    PubMed

    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

  14. Effects of Humidity Swings on Adsorption Columns for Air Revitalization: Modeling and Experiments

    NASA Technical Reports Server (NTRS)

    LeVan, M. Douglas; Finn, John E.

    1997-01-01

    Air purification systems are necessary to provide clean air in the closed environments aboard spacecraft. Trace contaminants are removed using adsorption. One major factor concerning the removal of trace contaminants is relative humidity. Water can reduce adsorption capacity and, due to constant fluctuations, its presence is difficult to incorporate into adsorption column designs. The purpose of the research was to allow for better design techniques in trace contaminant adsorption systems, especially for feeds with water present. Experiments and mathematical modeling research on effects of humidity swings on adsorption columns for air revitalization were carried out.

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

    PubMed

    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

  16. Enhanced adsorption of quaternary amine using modified activated carbon.

    PubMed

    Prahas, Devarly; Wang, M J; Ismadji, Suryadi; Liu, J C

    2014-01-01

    This study examined different methodologies to modify activated carbon (AC) for the removal of quaternary amine, tetramethylammonium hydroxide (TMAH), from water. Commercial carbon (WAC) was treated by nitric acid oxidation (NA-WAC), silica impregnation (SM-WAC0.5), and oxygen plasma (P10-WAC), and their characteristics and adsorption capacity were compared. The Langmuir model fitted the equilibrium adsorption data well under different pH. The maximum adsorption capacity of WAC was 27.77 mg/g, while those of NA-WAC, SM-WAC 0.5, and P10-WAC were 37.46, 32.83 and 29.03 mg/g, respectively. Nitric acid oxidation was the most effective method for enhancing the adsorption capacity of TMAH. Higher pH was favorable for TMAH adsorption. Desorption study revealed that NA-WAC had no considerable reduction in performance even after five cycles of regeneration by 0.1 N hydrochloric acid. It was proposed that electrostatic interaction was the main mechanism of TMAH adsorption on activated carbon. PMID:24845325

  17. Hybrid adsorptive membrane reactor

    DOEpatents

    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.

  18. Hybrid adsorptive membrane reactor

    NASA Technical Reports Server (NTRS)

    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.

  19. Assessing the adsorption properties of shales

    NASA Astrophysics Data System (ADS)

    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

  20. [Toluene, Benzene and Acetone Adsorption by Activated Carbon Coated with PDMS].

    PubMed

    Liu, Han-bing; Jiang, Xin; Wang, Xin; Yang, Bing; Xue, Nan-dong; Zhang, Shi-lei

    2016-04-15

    To improve the adsorption selectivity of volatile organic compounds ( VOCs) , activated carbon ( AC) was modified by polydimethylsiloxane (PDMS) and characterized by BET analysis and Boehm titration. Dynamic adsorption column experiments were conducted and Yoon-Neslon(Y-N) model was used to identify adsorption effect for toluene, beuzene and acetone on AC when relative humidity was 0%, 50% and 90%, respectively. The results showed that the BET area, micropore volume and surface functional groups decreased with the PDMS modification, and surface hydrophobicity of the modified AC was enhanced leading to a lower water adsorption capacity. The results of dynamic adsorption showed that the adsorption kinetics and capacity of Bare-AC decreased with the increase of relative humidity, and the adsorption capacities of PDMS coated AC were 1.86 times (toluene) and 1.92 times (benzene) higher than those of Bare-AC, while a significant improvement of adsorption capacity for acetone was not observed. These findings suggest that polarity of molecule can be an important influencing factor for adsorption on hydrophobic surface developed by PDMS. PMID:27548948

  1. Adsorption of tetracycline from aqueous solutions onto multi-walled carbon nanotubes with different oxygen contents

    PubMed Central

    Yu, Fei; Ma, Jie; Han, Sheng

    2014-01-01

    Oxidized multi-walled carbon nanotubes (MWCNTs) with different oxygen contents were investigated for the adsorption of tetracycline (TC) from aqueous solutions. As the surface oxygen content of the MWCNTs increased, the maximum adsorption capacity and adsorption coefficient of TC increased to the largest values and then decreased. The relation can be attributed to the interplay between the nanotubes' dispersibility and the water cluster formation upon TC adsorption. The overall adsorption kinetics of TC onto CNTs-3.2%O might be dependent on both intra-particle diffusion and boundary layer diffusion. The maximum adsorption capacity of TC on CNTs-3.2%O was achieved in the pH range of 3.3–8.0 due to formation of water clusters or H-bonds. Furthermore, the presence of Cu2+ could significantly enhanced TC adsorption at pH of 5.0. However, the solution ionic strength did not exhibit remarkable effect on TC adsorption. In addition, when pH is beyond the range (3.3–8.0), the electrostatic interactions caused the decrease of TC adsorption capacity. Our results indicate that surface properties and aqueous solution chemistry play important roles in TC adsorption on MWCNTs. PMID:24937315

  2. Adsorption characteristics of haloacetonitriles on functionalized silica-based porous materials in aqueous solution.

    PubMed

    Prarat, Panida; Ngamcharussrivichai, Chawalit; Khaodhiar, Sutha; Punyapalakul, Patiparn

    2011-09-15

    The effect of the surface functional group on the removal and mechanism of dichloroacetonitrile (DCAN) adsorption over silica-based porous materials was evaluated in comparison with powdered activated carbon (PAC). Hexagonal mesoporous silicate (HMS) was synthesized and functionalized by three different types of organosilanes (3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane and n-octyldimethysilane). Adsorption kinetics and isotherm models were used to determine the adsorption mechanism. The selective adsorption of five haloacetonitriles (HANs) in the single and mixed solute systems was also studied. The experiments revealed that the surface functional groups of the adsorbents largely affected the DCAN adsorption capacities. 3-Mercaptopropyl-grafted HMS had a high DCAN adsorption capacity compared to PAC. The adsorption mechanism is believed to occur via an ion-dipole electrostatic interaction in which water interference is inevitable at low concentrations of DCAN. In addition, the adsorption of DCAN strongly depended on the pH of the solution as this related to the charge density of the adsorbents. The selective adsorption of the five HANs over PAC was not observed, while the molecular structure of different HANs obviously influenced the adsorption capacity and selectivity over 3-mercaptopropyl-grafted HMS. PMID:21752539

  3. Adsorption of tetracycline from aqueous solutions onto multi-walled carbon nanotubes with different oxygen contents

    NASA Astrophysics Data System (ADS)

    Yu, Fei; Ma, Jie; Han, Sheng

    2014-06-01

    Oxidized multi-walled carbon nanotubes (MWCNTs) with different oxygen contents were investigated for the adsorption of tetracycline (TC) from aqueous solutions. As the surface oxygen content of the MWCNTs increased, the maximum adsorption capacity and adsorption coefficient of TC increased to the largest values and then decreased. The relation can be attributed to the interplay between the nanotubes' dispersibility and the water cluster formation upon TC adsorption. The overall adsorption kinetics of TC onto CNTs-3.2%O might be dependent on both intra-particle diffusion and boundary layer diffusion. The maximum adsorption capacity of TC on CNTs-3.2%O was achieved in the pH range of 3.3-8.0 due to formation of water clusters or H-bonds. Furthermore, the presence of Cu2+ could significantly enhanced TC adsorption at pH of 5.0. However, the solution ionic strength did not exhibit remarkable effect on TC adsorption. In addition, when pH is beyond the range (3.3-8.0), the electrostatic interactions caused the decrease of TC adsorption capacity. Our results indicate that surface properties and aqueous solution chemistry play important roles in TC adsorption on MWCNTs.

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

    PubMed

    Wang, Li; Wang, Aiqin

    2008-12-15

    A series of surfactant-modified montmorillonites (MMT) were prepared using octyltrimethylammonium bromide (OTAB), dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB) and stearyltrimethylammonium bromide (STAB), and the organification of MMT was proved by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron micrographic (SEM) and transmission electron microscope (TEM). The adsorption of Congo Red (CR) anionic dye from aqueous solution onto surfactant-modified MMT was carried out. Compared with MMT, the adsorption capacity of surfactant-modified MMT for CR was greatly enhanced and MMT modified with CTAB (2.0 CEC) exhibited the higher adsorption capacity. The effects of pH value of the dye solution, adsorption temperature, adsorption time and the initial dye concentration on the adsorption capacity of CR on CTAB-MMT have been investigated. The results showed that the adsorption kinetic of CR on CTAB-MMT could be best described by the pseudo-second-order model and that the adsorption isotherm of CR was in good agreement with the Langmuir equation. The IR spectra and SEM analysis also revealed that the adsorption of CTAB-MMT was a chemical adsorption process between CTAB and the NH(2), -N=N- and SO(3) groups of CR. PMID:18400385

  5. Atrazine adsorption removal with nylon6/polypyrrole core-shell nanofibers mat: possible mechanism and characteristics

    NASA Astrophysics Data System (ADS)

    Yang, Bi-Yi; Cao, Yang; Qi, Fei-Fei; Li, Xiao-Qing; Xu, Qian

    2015-05-01

    A functionalized nylon6/polypyrrole core-shell nanofibers mat (PA6/PPy NFM) was prepared via situ polymerization on nylon6 electrospun nanofibers mat (PA6 NFM) template and used as an adsorbent to remove atrazine from aqueous solutions. The core-shell structure of PA6/PPy NFM can be clearly proved under scanning electron microscope (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The effects of initial solution pH and ionic strength, as well as the comparison of the adsorption capacity of functionalized (PA6/PPy NFM) and non-functionalized (PA6 NFM) adsorbent, were examined to reveal the possible adsorption mechanism. The results indicated that π-π interaction and electrostatic interaction should play a key role in the adsorption process. The kinetics and thermodynamics studies also further elucidated the detailed adsorption characteristics of atrazine removal by PA6/PPy NFM. The adsorption of atrazine could be well described by the pseudo-second-order equation. The adsorption equilibrium data was well fitted with the Freundlich isotherm model with a maximum adsorption capacity value of 14.8 mg/g. In addition, the increase of adsorption rate caused by a temperature increase could be felicitously explained by the endothermic reaction. The desorption results showed that the adsorption capacity remained almost unchanged after six adsorption/desorption cycles. These results suggest that PA6/PPy NFM could be employed as an efficient adsorbent for removing atrazine from contaminated water sources.

  6. AgII doped MIL-101 and its adsorption of iodine with high speed in solution

    NASA Astrophysics Data System (ADS)

    Mao, Ping; Qi, Bingbing; Liu, Ying; Zhao, Lei; Jiao, Yan; Zhang, Yi; Jiang, Zheng; Li, Qiang; Wang, Jinfeng; Chen, Shouwen; Yang, Yi

    2016-05-01

    In order to improve the adsorption speed of iodine from water, MIL-101 with extra-large specific surface area (3054 m2/g) was chosen as a base material, and then, Ag was doped into MIL-101 to enhance its adsorption capacity through an incipient-wetness impregnation method. With the characterization of SEM-EDS, TEM, XRD, XPS, TGA, IR, and BET techniques, the resulting Ag was identified to be stay in the framework of MIL-101 stably in the form of AgII (generally, AgII cation is not stable). However, after the adsorption of I- anions, AgII stay in the cages of MIL-101 in the form of AgI/AgI3. It is important to note that, all adsorbents show high adsorption speed of iodine in solution. The equilibrium adsorption time of the adsorbents were acquired by only a few minutes, which can be attributed to its large BET surface area. An interesting note is that, when the doping amount of Ag is less than 9%, the iodine anions adsorption capacity of Ag@MIL-101 is greater than its theoretical adsorption capacity. It shows that both physical adsorption and chemical adsorption are existed in the adsorption process. This study hopefully leads to a new and highly efficient Ag-based adsorbent for iodide adsorb from solutions.

  7. Density functional study of the cysteine adsorption on Au nanoclusters

    NASA Astrophysics Data System (ADS)

    Pérez, L. A.; López-Lozano, X.; Garzón, I. L.

    2009-04-01

    The adsorption of the cysteine amino acid (H-SCβH2-CαH-NH2-COOH) on the Au55 cluster is investigated through density functional theory calculations. Two isomers, with icosahedral (Ih) and chiral (C1) geometries, of the Au55 cluster are used to calculate the adsorption energy of the cysteine on different facets of these isomers. Results, only involving the S(thiolate)-Au bonding show that the higher adsorption energies are obtained when the sulfur atom is bonded to an asymmetrical bridge site at the facet containing Au atoms with the lowest coordination of the C1 cluster isomer.

  8. Immobilization of Acetobacter aceti on cellulose ion exchangers: adsorption isotherms

    SciTech Connect

    Bar, R.; Gainer, J.L.; Kirwan, D.J.

    1986-08-01

    The adsorptive behavior of cells of Acetobacter aceti, ATCC 23746, on DEAE-, TEAE-, and DEHPAE-cellulose ion exchangers in a modified Hoyer's medium at 30 degrees Centigrade was investigated. The maximum observed adsorption capacities varied from 46 to 64 mg dry wt/g resin. The Langmuir isotherm form was used to fit the data, since the cells formed a monolayer on the resin and exhibited saturation. The equilibrium constant in the Langmuir expression was qualitatively correlated with the surface charge density of the resin. The adsorption was also ''normalized'' by considering the ionic capacities of the resins. The exceptionally high normalized adsorption capacity of ECTEOLA-cellulose, 261 mg dry/meq, may be explained by an interaction between the cell wall and the polyglyceryl chains of the exchanging groups in addition to the electrostatic effects. The effect of pH on the bacterial adsorption capacity of ECTEOLA-, TEAE-, and phosphate-cellulose resins was studied and the pH of the bacteria was estimated to be 3.0. 17 references.

  9. Adsorption of fluoride to UiO-66-NH2 in water: Stability, kinetic, isotherm and thermodynamic studies.

    PubMed

    Lin, Kun-Yi Andrew; Liu, Yu-Ting; Chen, Shen-Yi

    2016-01-01

    To provide safe drinking water, fluoride in water must be removed and adsorption processes appear to be the most widely used method. Metal organic frameworks (MOFs) represent a new class of adsorbents that have been used in various adsorption applications. To study the adsorption mechanism of fluoride to MOFs in water and obtain related adsorption parameters, we synthesized a zirconium-based MOF with a primary amine group on its ligand, named UiO-66-NH2. The kinetics, adsorption isotherm and thermodynamics of fluoride adsorption to UiO-66-NH2 were investigated. The crystalline structure of UiO-66-NH2 remained intact and the local structure of zirconium in UiO-66-NH2 did not change significantly after being exposed to fluoride. The kinetics of the fluoride adsorption in UiO-66-NH2 could be well represented by the pseudo second order rate law. The enthalpy of the adsorption indicates that the F(-) adsorption to UiO-66-NH2 was classified as a physical adsorption. However, the comparison between the adsorption capacities of UiO-66-NH2 and UiO-66 suggests that the fluoride adsorption to UiO-66-NH2 might primarily involve a strong interaction between F(-) and the metal site. The fluoride adsorption capacity of UiO-66-NH2 was found to decrease when pH>7. While the presence of chloride/bromide ions did not noticeably change the adsorption capacity of UiO-66-NH2, the ionic surfactants slightly affected the adsorption capacity of UiO-66-NH2. These findings provide insights to further optimize the adsorption process for removal of fluoride using zirconium-based MOFs. PMID:26397913

  10. Adsorption of Pyrene onto the Agricultural By-Product: Corncob.

    PubMed

    Li, Xiaojun; Tong, Dongli; Allinson, Graeme; Jia, Chunyun; Gong, Zongqing; Liu, Wan

    2016-01-01

    The adsorption behavior of pyrene on corncob was studied to provide a theoretical basis for the possible use of this material as an immobilized carrier for improving the bioremediation of PAH-contaminated soil. The results were as follows. Kinetic experiments showed that the adsorption processes obeyed a pseudo-second-order model. The intraparticle diffusion of Weber-Morris model fitting showed that the film and intraparticle diffusions were the key rate-limiting processes, and the adsorption process mainly consisted of three steps: boundary layer diffusion and two intra-particle diffusions. Experimental adsorption data for pyrene were successfully described by the adsorption-partition equilibrium model. The maximum adsorption capacity at 25°C was 214.8 μg g(-1). The adsorption contribution decreased significantly when the Ce/Sw (the equilibrium concentration/solubility in water) was higher than 1. Adsorption decreased with increased temperature. Based on the above results, the corncob particles could be helpful in the bioremediation of pyrene-contaminated soil. PMID:26573838

  11. Adsorption and desorption characteristics of arsenic onto ceria nanoparticles

    NASA Astrophysics Data System (ADS)

    Feng, Qinzhong; Zhang, Zhiyong; Ma, Yuhui; He, Xiao; Zhao, Yuliang; Chai, Zhifang

    2012-01-01

    The rapid increase in the use of engineered nanoparticles [ENPs] has resulted in an increasing concern over the potential impacts of ENPs on the environmental and human health. ENPs tend to adsorb a large variety of toxic chemicals when they are emitted into the environment, which may enhance the toxicity of ENPs and/or adsorbed chemicals. The study was aimed to investigate the adsorption and desorption behaviors of arsenic on ceria NPs in aqueous solution using batch technique. Results show that the adsorption behavior of arsenic on ceria NPs was strongly dependent on pH and independent of ionic strength, indicating that the electrostatic effect on the adsorption of these elements was relatively not important compared to surface chemical reactions. The adsorption isotherms fitted very well to both the Langmuir and Freundlich models. The thermodynamic parameters (Δ H 0 , Δ S 0 , and Δ G 0 ) for the adsorption of arsenic were determined at three different temperatures of 283, 303, and 323 K. The adsorption reaction was endothermic, and the process of adsorption was favored at high temperature. The desorption data showed that desorption hysteresis occurred at the initial concentration studied. High adsorption capacity of arsenic on ceria NPs suggests that the synergistic effects of ceria NPs and arsenic on the environmental systems may exist when they are released into the environment.

  12. EFFECT OF MOLECULAR OXYGEN ON THE ACTIVATED CARBON ADSORPTION OF NATURAL ORGANIC MATTER IN OHIO RIVER WATER

    EPA Science Inventory

    Recently published data show that the adsorptive capacity of granular activated carbon for phenois increases significantly in the presence of molecular oxygen (Vidic, Suidan,Traegner and Nakhla, 1990). in this study, the effect of molecular oxygen on the adsorptive capacity of a...

  13. High Efficiency Adsorption Chillers: High Efficiency Adsorption Cooling Using Metal Organic Heat Carriers

    SciTech Connect

    2010-10-01

    BEETIT Project: PNNL is incorporating significant improvements in materials that adsorb liquids or gases to design more efficient adsorption chillers. An adsorption chiller is a type of air conditioner that is powered by heat, solar or waste heat, or combustion of natural gas. Unlike typical chillers, this type has few moving parts and uses almost no electricity to operate. PNNL is designing adsorbent materials at the molecular level with at least 3 times higher refrigerant capacity and up to 20 times faster kinetics than adsorbents used in current chillers. By using the new adsorbent, PNNL is able to create a chiller that is significantly smaller, has twice the energy efficiency, and lower costs for materials and assembly time compared to conventional adsorption chillers.

  14. Adsorption of atrazine on soils: model study.

    PubMed

    Kovaios, Ilias D; Paraskeva, Christakis A; Koutsoukos, Petros G; Payatakes, Alkiviades Ch

    2006-07-01

    The adsorption of the widely used herbicide atrazine onto three model inorganic soil components (silica gel, gamma-alumina, and calcite (CaCO(3)) was investigated in a series of batch experiments in which the aqueous phase equilibrated with the solid, under different solution conditions. Atrazine did not show discernible adsorption on gamma-alumina (theta=25 degrees C, 3.8adsorption from solutions was found for silica gel suspensions. The adsorption isotherms obtained for atrazine uptake on silica gel particles were best fitted with the Freundlich model. An increase of the ionic strength of the electrolytic solution induced an increase of the surface concentration of atrazine on silica gel, indicating significant electrostatic interactions between atrazine and silica gel particles, possibly through interaction with the surface silanol groups of the solid substrate. Increase of the pH value of the electrolyte solution from 6 to 9 considerably decreased the amount of atrazine adsorbed on the silica gel substrate. Decrease of the solution pH from 6 to 3 had only a slight effect on the surface concentration of the adsorbed atrazine. The adsorption of atrazine on silica gel increased when the temperature was decreased from 40 to 25 degrees C, an indication that the adsorption is exothermic. The calculated enthalpy of adsorption ( approximately 10 kJ/mol) indicates that the uptake at the solid-liquid equilibrium pH (6.1) was largely due to physisorption. PMID:16556447

  15. Synthesis and utilization of a novel carbon nanotubes supported nanocables for the adsorption of dyes from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Jiang, Xinyu; Chen, Xiaoqing

    2015-09-01

    Using multiwalled carbon nanotubes(MWCNTs) as mechanical support and glucose as carbon resource, a hydrothermal carbonization route was designed for the synthesis of MWCNTs@carbon nanocables with tunable diameter and length. MWCNTs are firstly used as templates for the formation of carbon-rich composite nanocables, and the diameter of the nanocables could be tailored through adjusting the hydrothermal time or the ratio of MWCNTs and glucose. Owing to abundant superficial oxygen-containing functional groups, porous surface and remarkable reactivity, the as-synthesized nanocables are capable of efficiently adsorbing cationic dye methylene blue (MB) and crystal violet (CV). Furthermore, the optimum adsorption conditions, kinetics, adsorption isotherms and adsorption thermodynamics of dyes were studied systematically. Additionally, the maximum adsorption capacities calculated from data analysis (298.5 mg/g for MB and 228.3 mg/g for CV) are significant higher than those of raw MWCNTs and some other adsorbents reported previously, which provides strong evidence for using MWCNTs@carbon nanocables as adsorbent to remove dyes from aqueous solutions.

  16. Introduction of π-complexation into porous aromatic framework for highly selective adsorption of ethylene over ethane.

    PubMed

    Li, Baiyan; Zhang, Yiming; Krishna, Rajamani; Yao, Kexin; Han, Yu; Wu, Zili; Ma, Dingxuan; Shi, Zhan; Pham, Tony; Space, Brian; Liu, Jian; Thallapally, Praveen K; Liu, Jun; Chrzanowski, Matthew; Ma, Shengqian

    2014-06-18

    In this work, we demonstrate for the first time the introduction of π-complexation into a porous aromatic framework (PAF), affording significant increase in ethylene uptake capacity, as illustrated in the context of Ag(I) ion functionalized PAF-1, PAF-1-SO3Ag. IAST calculations using single-component-isotherm data and an equimolar ethylene/ethane ratio at 296 K reveal that PAF-1-SO3Ag shows exceptionally high ethylene/ethane adsorption selectivity (Sads: 27 to 125), far surpassing benchmark zeolite and any other MOF reported in literature. The formation of π-complexation between ethylene molecules and Ag(I) ions in PAF-1-SO3Ag has been evidenced by the high isosteric heats of adsorption of C2H4 and also proved by in situ IR spectroscopy studies. Transient breakthrough experiments, supported by simulations, indicate the feasibility of PAF-1-SO3Ag for producing 99.95%+ pure C2H4 in a Pressure Swing Adsorption operation. Our work herein thus suggests a new perspective to functionalizing PAFs and other types of advanced porous materials for highly selective adsorption of ethylene over ethane. PMID:24901372

  17. Adsorption of diethyl phthalate ester to clay minerals.

    PubMed

    Wu, Yanhua; Si, Youbin; Zhou, Dongmei; Gao, Juan

    2015-01-01

    Phthalate esters are a group of plasticizers, which have been widely detected in China's agricultural and industrial soils. In this study, batch adsorption experiments were conducted to investigate the environmental effects on the adsorption of diethyl phthalate ester (DEP) to clay minerals. The results showed that DEP adsorption isotherms were well fitted with the Freundlich model; the interlayer spacing of K(+) saturated montmorillonite (K-mont) was the most important adsorption area for DEP, and di-n-butyl ester (DnBP) was limited to intercalate into the interlayer of K-mont due to the bigger molecular size; there was no significant effect of pH and ionic strength on DEP adsorption to K-mont/Ca-mont, but to Na-mont clay. The adsorption to kaolinite was very limited. Data of X-ray diffraction and FTIR spectra further proved that DEP molecules could intercalate into K-/Ca-mont interlayer, and might interact with clay through H-bonding between carbonyl groups and clay adsorbed water. Coated humic acid on clay surface would enhance DEP adsorption at low concentration, but not at high concentration (eg. Ce>0.26 mM). The calculated adsorption enthalpy (ΔHobs) and adsorption isotherms at varied temperatures showed that DEP could be adsorbed easier as more adsorbed. This study implied that clay type, compound structure, exchangeable cation, soil organic matter and temperature played important roles in phthalate ester's transport in soil. PMID:25150972

  18. Adsorption of CO Molecules on Si(001) at Room Temperature

    NASA Astrophysics Data System (ADS)

    Seo, Eonmi; Eom, Daejin; Kim, Hanchul; Koo, Ja-Yong

    2015-03-01

    Initial adsorption of CO molecules on Si(001) is investigated by using room-temperature (RT) scanning tunneling microscopy (STM) and density functional theory calculations. Theoretical calculations show that only one adsorption configuration of terminal-bond CO (T-CO) is stable and that the bridge-bond CO is unstable. All the abundantly observed STM features due to CO adsorption can be identified as differently configured T-COs. The initial sticking probability of CO molecules on Si(001) at RT is estimated to be as small as ~ 1 x 10-4 monolayer/Langmuir, which is significantly increased at high-temperature adsorption experiments implying a finite activation barrier for adsorption. Thermal annealing at 900 K for 5 min results in the dissociation of the adsorbed CO molecules with the probability of 60-70% instead of desorption, indicating both a strong chemisorption state and an activated dissociation process. The unique adsorption state with a large binding energy, a tiny sticking probability, and a finite adsorption barrier is in stark contrast with the previous low-temperature (below 100 K) observations of a weak binding, a high sticking probability, and a barrierless adsorption. We speculate that the low-temperature results might be a signature of a physisorption state in the condensed phase.

  19. Breakthrough CO₂ adsorption in bio-based activated carbons.

    PubMed

    Shahkarami, Sepideh; Azargohar, Ramin; Dalai, Ajay K; Soltan, Jafar

    2015-08-01

    In this work, the effects of different methods of activation on CO2 adsorption performance of activated carbon were studied. Activated carbons were prepared from biochar, obtained from fast pyrolysis of white wood, using three different activation methods of steam activation, CO2 activation and Potassium hydroxide (KOH) activation. CO2 adsorption behavior of the produced activated carbons was studied in a fixed-bed reactor set-up at atmospheric pressure, temperature range of 25-65°C and inlet CO2 concentration range of 10-30 mol% in He to determine the effects of the surface area, porosity and surface chemistry on adsorption capacity of the samples. Characterization of the micropore and mesopore texture was carried out using N2 and CO2 adsorption at 77 and 273 K, respectively. Central composite design was used to evaluate the combined effects of temperature and concentration of CO2 on the adsorption behavior of the adsorbents. The KOH activated carbon with a total micropore volume of 0.62 cm(3)/g and surface area of 1400 m(2)/g had the highest CO2 adsorption capacity of 1.8 mol/kg due to its microporous structure and high surface area under the optimized experimental conditions of 30 mol% CO2 and 25°C. The performance of the adsorbents in multi-cyclic adsorption process was also assessed and the adsorption capacity of KOH and CO2 activated carbons remained remarkably stable after 50 cycles with low temperature (160°C) regeneration. PMID:26257348

  20. [Adsorption characteristics of f2 bacteriophages by four substrates in constructed wetland].

    PubMed

    Chen, Di; Zheng, Xiang; Wei, Yuan-Song; Yang, Yong

    2013-10-01

    Performance of f2 phages adsorption by four substrates including anthracite coal, steel slag, zeolite and forsterite was investigated through batch and dynamic experiments. Results of batch experiments showed that the removal efficiency of f2 phages by these four substrates was in the order of anthracite > steel slag > forsterite approximately zeolite. The adsorption of f2 phages by anthracite experienced fast, medium and slow stages, and the removal efficiency of f2 phages increased gradually with the increase of anthracite dosage, e. g. the optimized dosage of anthracite was 8.0 g at a solid/liquid ratio of 1:12.5 (m/V). The isothermal adsorption of all four substrates was described with Freundlich and Langmuir isothermal adsorption equation very well, and the adsorption of f2 phages by both anthracite and steel slag fitted pseudo-second order adsorption kinetics at their theoretical adsorption capacities of 3. 35 x 10(8) PFU.g-1 and 2.56 x 10(8) PFU.g-1, respectively, nearly the same as the equilibrium adsorption capacities obtained under the experiment conditions. And the liquid diffusion process was a rate-limiting step of the adsorption of f2 phage by both anthracite and steel slag, but not the only one. The results of dynamic adsorption experiments showed that the adsorption process of f2 phages in the three adsorption columns including anthracite, steel slag and zeolite experienced four stages of adaption, adsorption, pulse adsorption and adsorption equilibrium, and the total removal rates of f2 phages were more than 2. 55 Ig. PMID:24364309

  1. Amine-modified SBA-15 and MCF mesoporous molecular sieves as promising sorbents for natural antioxidant. Modeling of caffeic acid adsorption.

    PubMed

    Moritz, Michał; Geszke-Moritz, Małgorzata

    2016-04-01

    This work presents a detailed study of caffeic acid adsorption on mesoporous SBA-15 and MCF silicas functionalized with (3-aminopropyl)triethoxysilane (APTES) and 3-[2-(aminoethylamino)propyl]trimethoxysilane (AEAPTMS). Synthesized mesoporous adsorbents were characterized using different analytical techniques such as N2 sorption, XRD, TEM, SEM and FT-IR. The adsorption studies of caffeic acid were conducted in various organic solvents. Moreover, the effect of water content in 2-propanol-water mixture on adsorption efficiency was investigated. The experimental data were best fitted to the Langmuir equation, followed by the Temkin, Dubinin-Radushkevich and Freundlich models. The maximum adsorption capacity values calculated from the Langmuir model demonstrated that SBA-15 and MCF silicas modified with AEAPTMS revealed better adsorption properties toward caffeic acid (192.3 and 161.3mg/g, respectively) as compared to the materials modified with APTES (125.0 and 113.6 mg/g, respectively). The obtained results indicate that both SBA-15 and MCF silicas functionalized with AEAPTMS and APTES are promising materials for the entrapment of caffeic acid. PMID:26838867

  2. Iron modified bentonite: Enhanced adsorption performance for organic pollutant and its regeneration by heterogeneous visible light photo-Fenton process at circumneutral pH.

    PubMed

    Gao, Yaowen; Guo, Yongzhao; Zhang, Hui

    2016-01-25

    Iron modified bentonite (FeMB) was prepared and used as an inexpensive adsorbent to rapidly remove organic pollutant (Rhodamine B, RhB) from aqueous solution. The iron modification significantly improved the adsorption performance of FeMB for RhB and permitted an easy separation of FeMB from the treated effluent. The equilibrium adsorption studies indicated that the dye molecules obeyed Langmuir type of adsorption with the calculated maximum adsorption capacity of 168.13 mg g(-1) for FeMB. The heterogeneous photo-Fenton process operated at circumneutral pH in the presence of visible light irradiation was found to be effective for the regeneration of the spent FeMB. Furthermore, the regeneration efficiency of as high as 79% was still achieved after 5 consecutive adsorption-regeneration cycles. Considering that, the visible light photo-Fenton approach could be applied as an excellent alternative for regenerating clay-based adsorbents by avoiding the use of dissolved iron salts. PMID:26448496

  3. Adsorption of phenanthrene on natural snow.

    PubMed

    Domine, Florent; Cincinelli, Alessandra; Bonnaud, Elodie; Martellini, Tania; Picaud, Sylvain

    2007-09-01

    The snowpack is a reservoir for semivolatile organic compounds (SVOCs) and, in particular, for persistent organic pollutants (POPs), which are sequestered in winter and released to the atmosphere or hydrosphere in the spring. Modeling these processes usually assumes that SVOCs are incorporated into the snowpack by adsorption to snow surfaces, but this has never been proven because the specific surface area (SSA) of snow has never been measured together with snow composition. Here we expose natural snow to phenanthrene vapors (one of the more volatile POPs) and measure for the first time both the SSA and the chemical composition of the snow. The results are consistent with an adsorption equilibrium. The measured Henry's law constant is H(Phen)(T) = 2.88 x 10(22) exp(-10660/7) Pa m2 mol(-1), with Tin Kelvin. The adsorption enthalpy is delta H(ads) = -89 +/- 18 kJ mol(-1). We also perform molecular dynamics calculations of phenanthrene adsorption to ice and obtain AHads = -85 +/- 8 kJ mol(-1), close to the experimental value. Results are applied to the adsorption of phenanthrene to the Arctic and subarctic snowpacks. The subarctic snowpack, with a low snow area index (SAI = 1000), is a negligible reservoir of phenanthrene, butthe colder Arctic snowpack, with SAI = 2500, sequesters most of the phenanthrene present in the (snow + boundary layer) system. PMID:17937278

  4. Theoretical study on the adsorption of carbon dioxide on individual and alkali-metal doped MOF-5s

    NASA Astrophysics Data System (ADS)

    Ha, Nguyen Thi Thu; Lefedova, O. V.; Ha, Nguyen Ngoc

    2016-01-01

    Density functional theory (DFT) calculations were performed to investigate the adsorption of carbon dioxide (CO2) on metal-organic framework (MOF-5) and alkali-metal (Li, K, Na) doped MOF-5s. The adsorption energy calculation showed that metal atom adsorption is exothermic in MOF-5 system. Moreover, alkali-metal doping can significantly improve the adsorption ability of carbon dioxide on MOF-5. The best influence is observed for Li-doping.

  5. Introduction of π-Complexation into Porous Aromatic Framework for Highly Selective Adsorption of Ethylene over Ethane

    SciTech Connect

    Li, Baiyan; Zhang, Yiming; Krishna, Rajamani; Yao, Kexin; Han, Yu; Wu, Zili; Ma, Dingxuan; Shi, Zhan; Pham, Tony; Space, Brian; Liu, Jian; Thallapally, Praveen K.; Liu, Jun; Matthew, Chrzanowski; Ma, Shengqian

    2014-06-05

    We report herein a strategy of incorporating air stable Ag(I) ions into water stable, high surface area porous organic polymer (POP) affording significant increase in ethylene uptake capacity and extremely high Qst for ethylene (over 100 kJ/mol at low ethylene load-ing) as illustrated in the context of Ag(I) ion functionalized PAF-1, PAF-1-SO3Ag. IAST calculations using single-component-isotherm data and equimolar ethylene/ethane ratio at 296 K reveal PAF-1-SO3Ag shows exceptionally high ethylene/ethane adsorption selectivi-ty (Sads: 27 to 125), far surpassing benchmark zeolite and any other MOF reported in literature. This alongside excellent water/air stability, high ethylene uptake capacity, and mild regeneration requirements make PAF-1-SO3Ag hold promise for adsorption-based eth-ylene/ethane separations, paving a way to develop Ag(I) ion function-alized POPs as a new platform for highly selective adsorption of eth-ylene over ethane.

  6. Ag(I) Ion Functionalized Porous Organic Polymers As a New Platform for Highly Selective Adsorption of Ethylene over Ethane

    SciTech Connect

    LI, Baiyan; Zhang, Yiming; Ma, Dingxuan; Wu, Zili; Ma, Shengqian

    2014-01-01

    We report herein a strategy of incorporating air stable Ag(I) ions into water stable, high surface area porous organic polymer (POP) affording significant increase in ethylene uptake capacity and extremely high Qst for ethylene (over 100 kJ/mol at low ethylene load-ing) as illustrated in the context of Ag(I) ion functionalized PAF-1, PAF-1-SO3Ag. IAST calculations using single-component-isotherm data and equimolar ethylene/ethane ratio at 296 K reveal PAF-1-SO3Ag shows exceptionally high ethylene/ethane adsorption selectivi-ty (Sads: 27 to 125), far surpassing benchmark zeolite and any other MOF reported in literature. This alongside excellent water/air stability, high ethylene uptake capacity, and mild regeneration requirements make PAF-1-SO3Ag hold promise for adsorption-based eth-ylene/ethane separations, paving a way to develop Ag(I) ion function-alized POPs as a new platform for highly selective adsorption of eth-ylene over ethane.

  7. Adsorption of Pb(2+) from aqueous solution using spinel ferrite prepared from steel pickling sludge.

    PubMed

    Fang, Binbin; Yan, Yubo; Yang, Yang; Wang, Fenglian; Chu, Zhen; Sun, Xiuyun; Li, Jiansheng; Wang, Lianjun

    2016-01-01

    In this paper, spinel ferrite with high crystallinity and high saturation magnetization was successfully prepared from steel pickling sludge by adding iron source and precipitator in the hydrothermal condition. The obtained spinel ferrite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), vibrating sample magnetometer (VSM), and Zeta potential methods and investigated as an adsorbent for removal of Pb(2+) from aqueous solution. Batch experiments were performed by varying the pH values, contact time, temperature and initial metal concentration. The result of pH impact showed that the adsorption of Pb(2+) was a pH dependent process, and the pH 5.8 ± 0.2 was found to be the optimum condition. The achieved experimental data were analyzed with various kinetic and isotherm models. The kinetic studies revealed that Pb(2+) adsorption onto spinel ferrite followed a pseudo-second order model, and the Langmuir isotherm model provided the perfect fit to the equilibrium experimental data. At different temperatures, the maximum Pb(2+) adsorption capacities calculated from the Langmuir equation were in the range of 126.5-175.4 mg/g, which can be in competition with other adsorbents. The thermodynamic results showed that the spinel ferrite could spontaneously and endothermically adsorb Pb(2+) from aqueous solution. The regeneration studies showed that spinel ferrite could be used five times (removal efficiency (%) >90%) by desorption with HNO3 reagent. PMID:26942534

  8. Adsorption and desorption of U(VI) on functionalized graphene oxides: a combined experimental and theoretical study.

    PubMed

    Sun, Yubing; Yang, Shubin; Chen, Yue; Ding, Congcong; Cheng, Wencai; Wang, Xiangke

    2015-04-01

    The adsorption and desorption of U(VI) on graphene oxides (GOs), carboxylated GOs (HOOC-GOs), and reduced GOs (rGOs) were investigated by batch experiments, EXAFS technique, and computational theoretical calculations. Isothermal adsorptions showed that the adsorption capacities of U(VI) were GOs > HOOC-GOs > rGOs, whereas the desorbed amounts of U(VI) were rGOs > GOs > HOOC-GOs by desorption kinetics. According to EXAFS analysis, inner-sphere surface complexation dominated the adsorption of U(VI) on GOs and HOOC-GOs at pH 4.0, whereas outer-sphere surface complexation of U(VI) on rGO was observed at pH 4.0, which was consistent with surface complexation modeling. Based on the theoretical calculations, the binding energy of [G(···)UO2](2+) (8.1 kcal/mol) was significantly lower than those of [HOOC-GOs(···)UO2](2+) (12.1 kcal/mol) and [GOs-O(···)UO2](2+) (10.2 kcal/mol), suggesting the physisorption of UO2(2+) on rGOs. Such high binding energy of [GOs-COO(···)UO2](+) (50.5 kcal/mol) revealed that the desorption of U(VI) from the -COOH groups was much more difficult. This paper highlights the effect of the hydroxyl, epoxy, and carboxyl groups on the adsorption and desorption of U(VI), which plays an important role in designing GOs for the preconcentration and removal of radionuclides in environmental pollution cleanup applications. PMID:25761122

  9. Preparation of granular activated carbons from yellow mombin fruit stones for CO2 adsorption.

    PubMed

    Fiuza, Raildo Alves; Medeiros de Jesus Neto, Raimundo; Correia, Laise Bacelar; Carvalho Andrade, Heloysa Martins

    2015-09-15

    Stones of yellow mombin, a native fruit of the tropical America and West Indies, were used as starting materials to produce activated carbons, subsequently used as adsorbent for CO2 capture. The carbonaceous materials were either chemically activated with HNO3, H3PO4 and KOH or physically activated with CO2. The carbon samples were characterized by SEM, EDX, TG/DTA, Raman spectroscopy, physical adsorption for textural analysis and by acid-base titrations. The CO2 adsorption capacity and adsorption cycles were investigated by TG. The results indicate that the capacity of CO2 adsorption may be maximized on highly basic surfaces of micropores smaller than 1 nm. The KOH activated carbon showed high and stable capacity of CO2 adsorption after 10 cycles. PMID:26182993

  10. Investigating the potential of functionalized MCM-41 on adsorption of Remazol Red dye.

    PubMed

    Santos, Danilo Oliveira; de Lourdes Nascimento Santos, Maria; Costa, José Arnaldo Santana; de Jesus, Roberta Anjos; Navickiene, Sandro; Sussuchi, Eliana Midori; de Mesquita, Maria Eliane

    2013-07-01

    The modification of MCM-41 was performed with 3-aminopropropyltrimethoxysilane. The structural order and textural properties of the synthesized materials were studied by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetry/differential thermogravimetry, nitrogen adsorption, and desorption analysis. The adsorption capacity of NH2-MCM-41 was studied with Remazol Red dye. The following parameters were studied in the adsorption process: pH, temperature, adsorbent dosage, and initial concentration. The desorption process was studied in different concentrations of NaOH solutions. The Freundlich isotherm model was found to be fit with the equilibrium isotherm data. Kinetics of adsorption follows the modified Avrami rate equation. The maximum adsorption capacity was estimated to be 45.9 mg g(-1), with removal of the dye of 99.1%. The NH2-MCM-41 material exhibited high desorption capacity with 98.1%. PMID:23334547

  11. TECHNICAL NOTE: ADSORPTION CAPACITY OF GAC FOR SYNTHETIC ORGANICS

    EPA Science Inventory

    Isotherms are presented for 58 compounds in distilled-deionized water, filtered river water, and filtered groundwater. The compounds, which ranged from volatile organics to insecticides, are either regulated or being considered for regulation by the US Environmental Protection Ag...

  12. [Study on treatment of methylene blue wastewater by fly ash adsorption-Fenton and thermal regeneration].

    PubMed

    Bai, Yu-Jie; Zhang, Ai-Li; Zhou, Ji-Ti

    2012-07-01

    The physicochemical properties of water-washed fly ash (FA) and acid modified fly ash (M-FA) were investigated. The adsorption of methylene blue by FA and M-FA were studied by batch experiments. Two methods, Fenton-drive oxidation regeneration and thermal regeneration, were used for regeneration of the used FA and M-FA. The result showed that the rate of adsorption process followed the second order kinetics and the adsorption followed Langmuir isotherms. The adsorption equilibrium time was 30 min, and the equilibrium adsorption capacity of FA and M-FA were 4.22 mg x g(-1) and 5.98 mg x g(-1) respectively. The adsorption capability of M-FA was higher than that of FA. In the range of pH 2-12, the adsorption capacity of M-FA increased with the increase of pH, whereas the adsorption capacity of FA decreased slowly until the pH 8 and then increased. Electrostatic adsorption was the major factor on the adsorption capacity. Around 61% and 55% percentage regeneration (PR) were obtained for FA and M-FA respectively when 78.4 mmol x L(-1) H2O2 and 0.72 mmol x L(-1) Fe2+ were used. When the condition of thermal regeneration was 400 degrees C and 2 h, a positive correlation can be found between the PRs of FA and regeneration times, the PRs were 102%, 104% and 107% in three cycles of adsorption-thermal regeneration process. However a negative correlation can be found between the PRs of M-FA and regeneration times, the PRs were 82%, 75% and 74% in three cycles of adsorption-thermal regeneration process. The PR of FA was higher than that of M-FA, and thermal regeneration was superior to Fenton-drive regeneration. PMID:23002621

  13. A first-principles study of sodium adsorption and diffusion on phosphorene.

    PubMed

    Liu, Xiao; Wen, Yanwei; Chen, Zhengzheng; Shan, Bin; Chen, Rong

    2015-07-01

    The structural, electronic, electrochemical as well as diffusion properties of Na doped phosphorene have been investigated based on first-principles calculations. The strong binding energy between Na and phosphorene indicates that Na could be stabilized on the surface of phosphorene without clustering. By comparing the adsorption of Na atoms on one side and on both sides of phosphorene, it has been found that Na-Na exhibits strong repulsion at the Na-Na distance of less than 4.35 Å. The Na intercalation capacity is estimated to be 324 mA h g(-1) and the calculated discharge curve indicates quite a low Na(+)/Na voltage of phosphorene. Moreover, the diffusion energy barrier of Na atoms on the phosphorene surface at both low and high Na concentrations is as low as 40-63 meV, which implies the high mobility of Na during the charge/discharge process. PMID:26051226

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

    PubMed

    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

  15. Adsorption mechanism of acids and bases in reversed-phase liquid chromatography in weak buffered mobile phases designed for liquid chromatography/mass spectrometry

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2009-01-01

    The overloaded band profiles of five acido-basic compounds were measured, using weakly buffered mobile phases. Low buffer concentrations were selected to provide a better understanding of the band profiles recorded in LC/MS analyses, which are often carried out at low buffer concentrations. In this work, 10 {micro}L samples of a 50 mM probe solution were injected into C{sub 18}-bonded columns using a series of five buffered mobile phases at {sub W}{sup S}pH between 2 and 12. The retention times and the shapes of the bands were analyzed based on thermodynamic arguments. A new adsorption model that takes into account the simultaneous adsorption of the acidic and the basic species onto the endcapped adsorbent, predicts accurately the complex experimental profiles recorded. The adsorption mechanism of acido-basic compounds onto RPLC phases seems to be consistent with the following microscopic model. No matter whether the acid or the base is the neutral or the basic species, the neutral species adsorbs onto a large number of weak adsorption sites (their saturation capacity is several tens g/L and their equilibrium constant of the order of 0.1 L/g). In contrast, the ionic species adsorbs strongly onto fewer active sites (their saturation capacity is about 1 g/L and their equilibrium constant of the order of a few L/g). From a microscopic point of view and in agreement with the adsorption isotherm of the compound measured by frontal analysis (FA) and with the results of Monte-Carlo calculations performed by Schure et al., the first type of adsorption sites are most likely located in between C{sub 18}-bonded chains and the second type of adsorption sites are located deeper in contact with the silica surface. The injected concentration (50 mM) was too low to probe the weakest adsorption sites (saturation capacity of a few hundreds g/L with an equilibrium constant of one hundredth of L/g) that are located at the very interface between the C{sub 18}-bonded layer and the bulk

  16. Isotherms for Water Adsorption on Molecular Sieve 3A: Influence of Cation Composition

    DOE PAGESBeta

    Lin, Ronghong; Ladshaw, Austin; Nan, Yue; Liu, Jiuxu; Yiacoumi, Sotira; Tsouris, Costas; DePaoli, David W.; Tavlarides, Lawrence L.

    2015-06-16

    This study is part of our continuing efforts to address engineering issues related to the removal of tritiated water from off-gases produced in used nuclear fuel reprocessing facilities. In the current study, adsorption equilibrium of water on molecular sieve 3A beads was investigated. Adsorption isotherms for water on the UOP molecular sieve 3A were measured by a continuous-flow adsorption system at 298, 313, 333, and 353 K. Experimental data collected were analyzed by the Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm model. The K+/Na+ molar ratio of this particular type of molecular sieve 3A was ~4:6. Our results showed that themore » GSTA isotherm model worked very well to describe the equilibrium behavior of water adsorption on molecular sieve 3A. The optimum number of parameters for the current experimental data was determined to be a set of four equilibrium parameters. This result suggests that the adsorbent crystals contain four energetically distinct adsorption sites. In addition, it was found that water adsorption on molecular sieve 3A follows a three-stage adsorption process. This three-stage adsorption process confirmed different water adsorption sites in molecular sieve crystals. In addition, the second adsorption stage is significantly affected by the K+/Na+ molar ratio. In this stage, the equilibrium adsorption capacity at a given water vapor pressure increases as the K+/Na+ molar ratio increases.« less

  17. Isotherms for Water Adsorption on Molecular Sieve 3A: Influence of Cation Composition

    SciTech Connect

    Lin, Ronghong; Ladshaw, Austin; Nan, Yue; Liu, Jiuxu; Yiacoumi, Sotira; Tsouris, Costas; DePaoli, David W.; Tavlarides, Lawrence L.

    2015-06-16

    This study is part of our continuing efforts to address engineering issues related to the removal of tritiated water from off-gases produced in used nuclear fuel reprocessing facilities. In the current study, adsorption equilibrium of water on molecular sieve 3A beads was investigated. Adsorption isotherms for water on the UOP molecular sieve 3A were measured by a continuous-flow adsorption system at 298, 313, 333, and 353 K. Experimental data collected were analyzed by the Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm model. The K+/Na+ molar ratio of this particular type of molecular sieve 3A was ~4:6. Our results showed that the GSTA isotherm model worked very well to describe the equilibrium behavior of water adsorption on molecular sieve 3A. The optimum number of parameters for the current experimental data was determined to be a set of four equilibrium parameters. This result suggests that the adsorbent crystals contain four energetically distinct adsorption sites. In addition, it was found that water adsorption on molecular sieve 3A follows a three-stage adsorption process. This three-stage adsorption process confirmed different water adsorption sites in molecular sieve crystals. In addition, the second adsorption stage is significantly affected by the K+/Na+ molar ratio. In this stage, the equilibrium adsorption capacity at a given water vapor pressure increases as the K+/Na+ molar ratio increases.

  18. Sub-ambient carbon dioxide adsorption properties of nitrogen doped graphene

    SciTech Connect

    Tamilarasan, P.; Ramaprabhu, Sundara

    2015-04-14

    Carbon dioxide adsorption on carbon surface can be enhanced by doping the surface with heterogeneous atoms, which can increase local surface affinity. This study presents the carbon dioxide adsorption properties of nitrogen doped graphene at low pressures (<100 kPa). Graphene was exposed to nitrogen plasma, which dopes nitrogen atoms into carbon hexagonal lattice, mainly in pyridinic and pyrrolic forms. It is found that nitrogen doping significantly improves the CO{sub 2} adsorption capacity at all temperatures, due to the enrichment of local Lewis basic sites. In general, isotherm and thermodynamic parameters suggest that doped nitrogen sites have nearly same adsorption energy of surface defects and residual functional groups. The isosteric heat of adsorption remains in physisorption range, which falls with surface coverage, suggesting the distribution of magnitude of adsorption energy. The absolute values of isosteric heat and entropy of adsorption are slightly increased upon nitrogen doping.

  19. Enhanced adsorptive removal of toxic dyes using SiO2 nanofibers

    NASA Astrophysics Data System (ADS)

    Batool, S. S.; Imran, Z.; Hassan, Safia; Rasool, Kamran; Ahmad, Mushtaq; Rafiq, M. A.

    2016-05-01

    Electrospinning method was used to synthesize porous SiO2 nanofibers. The adsorption of Methyl Orange and Safranin O by porous SiO2 nanofibers was carried out by varying the parameters such as pH, contact time, adsorbent dose, dye concentration, and temperature. Equilibrium adsorption data followed Langmuir isotherms. Kinetic adsorption followed second-order rate kinetics model. The maximum adsorption capacity for Methyl Orange and Safranin O was found to be 730.9 mg/g and 960.4 mg/g, respectively. Acidic pH was favorable for the adsorption of Methyl Orange while basic pH was favorable for the adsorptions of Safranin O. Modeling study suggested the major mode of adsorption, while thermodynamic study showed the endothermic reactions. This effort has pronounced impact on environmental applications of SiO2 nanofibers as auspicious adsorbent nanofibers for organic material from aqueous solution.

  20. Chitosan/maghemite composite: a magsorbent for the adsorption of methyl orange.

    PubMed

    Obeid, Layaly; Bée, Agnès; Talbot, Delphine; Ben Jaafar, Soukeina; Dupuis, Vincent; Abramson, Sébastien; Cabuil, Valérie; Welschbillig, Mathias

    2013-11-15

    In this study, magnetic beads were prepared by encapsulation of magnetic nanoparticles in epichlorohydrin cross-linked chitosan beads. Their adsorption characteristics were assessed by using methyl orange (MO) as an adsorbate. MO adsorption onto chitosan beads was found to be optimal in the pH range of 3-5. The adsorption isotherm was well described by the Langmuir model and showed high MO adsorption capacity (2.38 mmol/g, i.e. 779 mg/g). MO adsorption kinetics followed a pseudo-second-order kinetic model, indicating that adsorption was the rate-limiting step. At 0.305 mmol/L, only 19 min was required to reach 90% adsorption and 50% of the MO was adsorbed in 2 min. Desorption studies of MO using NaOH showed the reusability of the magsorbent. No release of iron species was observed at pH>2.4. PMID:23998368

  1. A review of heavy metal adsorption by marine algae

    NASA Astrophysics Data System (ADS)

    Jin-Fen, Pan; Rong-Gen, Lin; Li, Ma

    2000-09-01

    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.

  2. High capacity carbon dioxide sorbent

    SciTech Connect

    Dietz, Steven Dean; Alptekin, Gokhan; Jayaraman, Ambalavanan

    2015-09-01

    The present invention provides a sorbent for the removal of carbon dioxide from gas streams, comprising: a CO.sub.2 capacity of at least 9 weight percent when measured at 22.degree. C. and 1 atmosphere; an H.sub.2O capacity of at most 15 weight percent when measured at 25.degree. C. and 1 atmosphere; and an isosteric heat of adsorption of from 5 to 8.5 kilocalories per mole of CO.sub.2. The invention also provides a carbon sorbent in a powder, a granular or a pellet form for the removal of carbon dioxide from gas streams, comprising: a carbon content of at least 90 weight percent; a nitrogen content of at least 1 weight percent; an oxygen content of at most 3 weight percent; a BET surface area from 50 to 2600 m.sup.2/g; and a DFT micropore volume from 0.04 to 0.8 cc/g.

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

    PubMed

    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 (<1kDa) were found to be the major contributors to the significant reduction in PFC adsorption capacity, while large-molecular-weight compounds (>30kDa) had much less effect on PFC adsorption capacity. PMID:22609392

  4. Influence of Inorganic Ions on Aggregation and Adsorption Behaviors of Human Adenovirus

    EPA Science Inventory

    In this study, we investigated the influence of inorganic ions on the aggregation and deposition (adsorption) behavior of human adenovirus (HAdV). Experiments were conducted to determine the surface charge and size of HAdV and viral adsorption capacity of sand in different salt c...

  5. Modeling selenium (IV and VI) adsorption envelopes in selected tropical soils using the constant capacitance model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The adsorption of selenium (Se) on soil is important due to the relevance of Se to environmental and health issues. The adsorption of Se(IV) and Se(VI) was evaluated on soil samples from São Paulo state, Brazil, as a function of varying pH, and the experimental data were fitted to the constant capac...

  6. Experimental study of water adsorption on activated carbons

    SciTech Connect

    Salame, I.I.; Bandosz, T.J. |

    1999-01-19

    Two carbons of different origins (wood and coal) were oxidized with nitric acid. The materials were characterized using sorption of nitrogen. Boehm titration, and potentiometric titration. The water adsorption isotherms were measured at various temperatures close to ambient (relative pressure from 0.001 to 0.3). From these isotherms heats of adsorption were calculated using virial equation. The results showed that the isosteric heats of water adsorption are affected by surface chemical heterogeneity only at low surface coverage. The shapes of heats obtained indicate strong water-water interactions as a result of adsorption on secondary sites and cluster formation. In all cases the limiting heat of adsorption equal to the heat of water condensation (45 kJ/mol) was obtained.

  7. Adsorption and separation of proteins by a smectitic clay mineral.

    PubMed

    Ralla, Kathrin; Sohling, Ulrich; Riechers, Daniel; Kasper, Cornelia; Ruf, Friedrich; Scheper, Thomas

    2010-09-01

    The adsorption of proteins by a smectitic clay mineral was investigated. The clay used in this study is a mixture of montmorillonite and amorphous SiO(2). Due to the high porosity the montmorillonite units are accessible for protein adsorption. The amorphous silica prevents the montmorillonite from swelling and allows column packing. Protein adsorption was performed at different pH under static conditions. Furthermore, static capacities were determined. The material reveals high adsorption capacities for proteins under static conditions (270-408 mg/g), whereby proteins are mainly adsorbed via electrostatic interactions. The Freundlich isotherm is suggested as an adsorption model. For desorption a pH shift was found to be most effective. Binding and elution of human serum albumin and ovalbumin were tested under dynamic conditions. Dynamic capacities of about 40 mg/g for ovalbumin at 764 cm/h were found. The clay mineral provides suitable properties for the application as cost-efficient, alternative separation material. PMID:20340034

  8. Adsorption of pesticides from water by functionalized organobentonites.

    PubMed

    Cruz-Guzmán, Marta; Celis, Rafael; Hermosín, M Carmen; Koskinen, William C; Cornejo, Juan

    2005-09-21

    Replacement of natural inorganic cations of clay minerals with organic cations has been proposed as a strategy to improve the adsorptive capacity of clay minerals for organic compounds, including pesticides. The organic cations most commonly used for this purpose have been quaternary ammonium ions containing alkyl or aryl chains without specific functional groups. In this work, we evaluated the ability of two bentonites (SWy-2 and SAz-1) exchanged with four natural organic cations containing diverse functional groups (L-carnitine, L-cysteine ethyl ester, L-cystine dimethyl ester, and thiamine) as adsorbents of pesticides varying in their chemical structures (simazine, hexazinone, triadimefon, alachlor, carbaryl, and imazethapyr). For comparison purposes, the adsorptive properties of two "classical" organobentonites, hexadecyltrimethylammonium- and phenyltrimethylammonium-exchanged bentonites, were also determined. Most organobentonites displayed higher affinity for the pesticides than the untreated bentonites, but the improvement in adsorption capacity varied depending on the characteristics of the pesticide and the interlayer organic cation. Triadimefon, carbaryl, and imazethapyr displayed the highest affinity for carnitine (K(f) = 229-2377)-, thiamine (K(f) = 83-354)-, and cystine (K(f) = 96-100)-treated bentonites, respectively, whereas alachlor was adsorbed similarly by all organobentonites. In general, pesticide adsorption-desorption hysteresis was greater for adsorbents with the highest adsorption capacities. The results demonstrate that selective modification of smectitic clay minerals with natural organic cations containing appropriate functional groups can be a useful strategy to improve their performance for the removal of specific pesticides from the environment. PMID:16159179

  9. Adsorption of ciprofloxacin on surface-modified carbon materials.

    PubMed

    Carabineiro, S A C; Thavorn-Amornsri, T; Pereira, M F R; Figueiredo, J L

    2011-10-01

    The adsorption capacity of ciprofloxacin (CPX) was determined on three types of carbon-based materials: activated carbon (commercial sample), carbon nanotubes (commercial multi-walled carbon nanotubes) and carbon xerogel (prepared by the resorcinol/formaldehyde approach at pH 6.0). These materials were used as received/prepared and functionalised through oxidation with nitric acid. The oxidised materials were then heat treated under inert atmosphere (N2) at different temperatures (between 350 and 900°C). The obtained samples were characterised by adsorption of N2 at -196 °C, determination of the point of zero charge and by temperature programmed desorption. High adsorption capacities ranging from approximately 60 to 300 mgCPxgC(-1) were obtained (for oxidised carbon xerogel, and oxidised thermally treated activated carbon Norit ROX 8.0, respectively). In general, it was found that the nitric acid treatment of samples has a detrimental effect in adsorption capacity, whereas thermal treatments, especially at 900 °C after oxidation, enhance adsorption performance. This is due to the positive effect of the surface basicity. The kinetic curves obtained were fitted using 1st or 2nd order models, and the Langmuir and Freundlich models were used to describe the equilibrium isotherms obtained. The 2nd order and the Langmuir models, respectively, were shown to present the best fittings. PMID:21733541

  10. Direct Observation of Xe and Kr Adsorption in a Xe-selective Microporous Metal Organic Framework

    DOE PAGESBeta

    Chen, Xianyin; Plonka, Anna M.; Banerjee, Debasis; Krishna, Rajamani; Schaef, Herbert T.; Ghose, Sanjit; Thallapally, Praveen K.; Parise, John B.

    2015-05-22

    We found that the cryogenic separation of noble gases is energy-intensive and expensive, especially when low concentrations are involved. Metal–organic frameworks (MOFs) containing polarizing groups within their pore spaces are predicted to be efficient Xe/Kr solid-state adsorbents, but no experimental insights into the nature of the Xe–network interaction are available to date. Here we report a new microporous MOF (designated SBMOF-2) that is selective toward Xe over Kr under ambient conditions, with a Xe/Kr selectivity of about 10 and a Xe capacity of 27.07 wt % at 298 K. Single-crystal diffraction results show that the Xe selectivity may be attributedmore » to the specific geometry of the pores, forming cages built with phenyl rings and enriched with polar -OH groups, both of which serve as strong adsorption sites for polarizable Xe gas. The Xe/Kr separation in SBMOF-2 was investigated with experimental and computational breakthrough methods. These experiments showed that Kr broke through the column first, followed by Xe, which confirmed that SBMOF-2 has a real practical potential for separating Xe from Kr. Our calculations showed that the capacity and adsorption selectivity of SBMOF-2 are comparable to those of the best-performing unmodified MOFs such as NiMOF-74 or Co formate.« less

  11. Direct Observation of Xe and Kr Adsorption in a Xe-selective Microporous Metal Organic Framework

    SciTech Connect

    Chen, Xianyin; Plonka, Anna M.; Banerjee, Debasis; Krishna, Rajamani; Schaef, Herbert T.; Ghose, Sanjit; Thallapally, Praveen K.; Parise, John B.

    2015-05-22

    We found that the cryogenic separation of noble gases is energy-intensive and expensive, especially when low concentrations are involved. Metal–organic frameworks (MOFs) containing polarizing groups within their pore spaces are predicted to be efficient Xe/Kr solid-state adsorbents, but no experimental insights into the nature of the Xe–network interaction are available to date. Here we report a new microporous MOF (designated SBMOF-2) that is selective toward Xe over Kr under ambient conditions, with a Xe/Kr selectivity of about 10 and a Xe capacity of 27.07 wt % at 298 K. Single-crystal diffraction results show that the Xe selectivity may be attributed to the specific geometry of the pores, forming cages built with phenyl rings and enriched with polar -OH groups, both of which serve as strong adsorption sites for polarizable Xe gas. The Xe/Kr separation in SBMOF-2 was investigated with experimental and computational breakthrough methods. These experiments showed that Kr broke through the column first, followed by Xe, which confirmed that SBMOF-2 has a real practical potential for separating Xe from Kr. Our calculations showed that the capacity and adsorption selectivity of SBMOF-2 are comparable to those of the best-performing unmodified MOFs such as NiMOF-74 or Co formate.

  12. GRANULAR ACTIVATED CARBON ADSORPTION AND FLUID-BED REACTIVATION AT MANCHESTER, NEW HAMPSHIRE

    EPA Science Inventory

    Treatment performances of virgin and reactivated GAC were evaluated during three reactivation-exhaustion cycles by measuring total organic carbon (TOC), trihalomethanes (THM), and trihalomethane formation potential (THMFP). GAC adsorptive capacity was measured using traditional t...

  13. Adsorption of Cr(III) from acidi