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Adsorbent
Kinds of Adsorbent Terms modified by Adsorbent Selected AbstractsBuchbesprechung: ADSORBENTS , Fundamentals and Applications.CHEMIE-INGENIEUR-TECHNIK (CIT), Issue 1-2 2004Von R. T. Yang No abstract is available for this article. [source] Bentonite as a Natural Adsorbent for the Sorption of Iron from the Ground Water Exploited from Aswan Area, EgyptGROUND WATER MONITORING & REMEDIATION, Issue 1 2004Gharib M. Taha Sorption of dissolved Fe2+ on bentonite was studied using a batch technique. The distribution coefficient, Kd, was evaluated for a bentonite-iron system as a function of contact time, pH, sorbent and sorbate concentrations, and temperature. Sorption results were interpreted in terms of Freundlich's and Langmuir's equations. Thermodynamic parameters for the sorption system were determined at three temperatures: 298°, 308°, and 318°K. The values of ,H°(-4.0 kjmol,1) and ,G°(-2.46 Kjmol,1) at 298°K (25°C) suggest that sorption of iron on bentonite is an exothermic and a spontaneous process. The ,G° value became less negative at higher temperatures and, therefore, less iron was sorbed at higher temperatures. The desorption studies with 0.01M CaCl2 and deionized water at iron loading on bentonite showed that more than 90 wt% of the iron is irreversibly sorbed, probably due to the fixation of the iron by isomorphous replacement in the crystal lattice of the sorbent. [source] Activated Carbon Adsorbent for the Aqueous Phase Adsorption of Amoxicillin in a Fixed BedCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2010N. J. R. Ornelas Abstract Equilibrium constant and mass transfer parameters are needed for the study of amoxicillin separation in any process involving adsorption in fixed beds. In this work, the adsorption of amoxicillin and 6-aminopenillanic acid in aqueous solution on activated carbon were studied using static adsorption tests. The adsorption capacity was found to be strongly dependent on the pH of the aqueous phase. The adsorption constants, overall mass transfer coefficients, and axial dispersion coefficients for amoxicillin and 6-aminopenillanic acid were determined, by moment analysis, from a series of step tests in a fixed bed packed with activated carbon. The total bed voidage and axial dispersion coefficient were estimated from blue dextran pulse test data at different flow rates. The results show that adsorption intensity increased with increasing temperature. Furthermore, the increasing trend of HETP with velocity suggests that axial dispersion and mass transfer resistance control the column efficiency. [source] Different Morphological Organic,Inorganic Hybrid Nanomaterials as Fluorescent Chemosensors and Adsorbents for CuII IonsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2008Soo Jin Lee Abstract Functionalized silica nanotubes (FSNT), functionalized mesoporous silica (FMS), and functionalized silica nanoparticles (FSNP-15) with an immobilized phenanthroline moiety as a fluorescent receptor were fabricated by a sol,gel reaction, and their binding abilities with metal ions were evaluated by fluorophotometry in water/acetonitrile (8:2, v/v) at pH 7. They selectively recognized Cu2+ ions among other metal cations such as Co2+, Cd2+, Hg2+, Ni2+, Fe3+, Ag+, Pb2+, and Zn2+, because the Cu2+ ion selectively binds to the nitrogen atoms of the phenanthroline moiety. Among the three silica nanomaterials with the immobilized receptor 1, the sensitivity of FSNT for Cu2+ ions is better than those of FMS and FSNP-15, indicating that the adsorption capacity for metal ions is dependent on the shape and surface area of the supporting nanomaterials. FSNT (10 mg) adsorb 75,% of the Cu2+ ions (2.0,×,10,4 mM) while FSNP-15 (10 mg) adsorb only 36,%. The detection limit of FSNT for Cu2+ ions was ca. 3.0,×,10,8M. FSNT and FMS can be easily renewed by treatment with a solution of HCl and tetrabutylammonium hydroxide. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Synthesis,Structure,Property Relationships for Hyperbranched Aminosilica CO2 AdsorbentsADVANCED FUNCTIONAL MATERIALS, Issue 23 2009Jeffrey H. Drese Abstract Hyperbranched aminosilica (HAS) adsorbents are prepared via the ring-opening polymerization of aziridine in the presence of mesoporous silica SBA-15 support. The aminopolymers are covalently bound to the silica support and capture CO2 reversibly in a temperature swing process. Here, a range of HAS materials are prepared with different organic loadings. The effects of organic loading on the structural properties and CO2 adsorption properties of the resultant hybrid materials are examined. The residual porosity in the HAS adsorbents after organic loading, as well as the molecular weights and degrees of branching for the separated aminopolymers, are determined to draw a relationship between adsorbent structure and performance. Humid adsorption working capacities and apparent adsorption kinetics are determined from experiments in a packed-bed flow system monitored by mass spectrometry. Dry adsorption isotherms are presented for one HAS adsorbent with a high amine loading at 35 and 75,°C. These combined results establish the relationships between adsorbent synthesis, structure, and CO2 adsorption properties of the family of HAS materials. [source] Synthesis of Novel Porous Magnetic Silica Microspheres as Adsorbents for Isolation of Genomic DNABIOTECHNOLOGY PROGRESS, Issue 2 2006Zhichao Zhang An improved procedure is described for preparation of novel mesoporous microspheres consisting of magnetic nanoparticles homogeneously dispersed in a silica matrix. The method is based on a three-step process, involving (i) formation of hematite/silica composite microspheres by urea-formaldehyde polymerization, (ii) calcination of the composite particles to remove the organic constituents, and (iii) in situ transformation of the iron oxide in the composites by hydrogen reductive reaction. The as-synthesized magnetite/silica composite microspheres were nearly monodisperse, mesoporous, and magnetizable, with as typical values an average diameter of 3.5 ,m, a surface area of 250 m2/g, a pore size of 6.03 nm, and a saturation magnetization of 9.82 emu/g. These magnetic particles were tested as adsorbents for isolation of genomic DNA from Saccharomyces cerevisiae cells and maize kernels. The results are quite encouraging as the magnetic particle based protocols lead to the extraction of genomic DNA with satisfactory integrity, yield, and purity. Being hydrophilic in nature, the porous magnetic silica microspheres are considered a good alternative to polystyrene-based magnetic particles for use in biomedical applications where nonspecific adsorption of biomolecules is to be minimized. [source] Selective Capture of Water Using Microporous Adsorbents To Increase the Lifetime of LubricantsCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 3 2009Eng-Poh Ng Abstract Long live lubricants: The selective capture of water from lubricants using nanosized microporous aluminophosphate (AEI) and aluminosilicate materials was studied. Nearly 98,% of the moisture was removed from the lubricating oil under ambient conditions, resulting in a significant improvement in the lubricating service lifetime. Moreover, both the lubricant and the microporous sorbents can be recovered and reused. The selective capture of water from lubricants using nanosized microporous aluminophosphate and aluminosilicate materials was studied with an aim to increase the lifetime of the lubricating mineral oil. The amount of water present in oxidized lubricating oil before and after treatment with microporous materials was studied by FTIR spectroscopy and determined quantitatively using the Karl Fischer titration method. Nanosized aluminophosphate revealed a high selectivity for water without adsorbing other additives, in contrast to nanosized aluminosilicates which also adsorb polar oxidation products and ionic additives. About 98,% of the initial moisture could be removed from the lubricating oil under ambient conditions, resulting in a significant improvement in the lubricating service lifetime. Moreover, no by-products are formed during the process and both the lubricant and the sorbents can be recovered and reused, thus the method is environmentally friendly. [source] Adsorptive Desulfurization and Denitrogenation of Refinery Fuels Using Mesoporous Silica AdsorbentsCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 4 2008Jun-Mi Kwon Adsorbed in what it's doing: Well-designed mesoporous silica adsorbents (see scheme) can contribute to the production of clean fuels through preferential adsorption of nitrogen- and sulfur-containing compounds from light gas oil and heavy catalytic naphtha in refinery streams. The adsorbent with Zr ions shows a higher adsorption capacity and affinity for sulfur compounds than its non-zirconia-containing counterpart. [source] Removal of Copper-phthalocyanine from Aqueous Solution by Cationically Templated MCM-41 and MCM-48 Nanoporous AdsorbentsCHINESE JOURNAL OF CHEMISTRY, Issue 11 2008Mansoor ANBIA The effect of cationic template on the adsorption of copper-phthalocyanine-3,4,,4,,,4,,,-tetrasulfonic acid tetrasodium salt [Cu(tsPc),4·4Na+] in MCM-41 and MCM-48 mesoporous materials was investigated, using cetyltrimethylammonium bromide (CTAB) as the cationic template and tetraethyl-orthosilicate as the silica source for synthesis of mesoporous materials. The properties of synthesized samples were characterized with XRD-low angle and scanning electron microscopy. The as-synthesized mesoporous samples were used for the separation of Cu(tsPc),4·4Na+ from aqueous solution, which showed very high adsorption capacity for it. [source] Voltammetric Detection of Lead(II) Using Amide-Cyclam- Functionalized Silica-Modified Carbon Paste ElectrodesELECTROANALYSIS, Issue 15 2009Stéphanie Goubert-Renaudin Abstract 2-(4,8,11-Triscarbamoylmethyl-1,4,8,11-tetraazacyclotetradec-1-yl)acetamide (TETAM) derivatives bearing 1, 2, or 4 silylated arms have been synthesized and grafted to the surface of silica gel and ordered mesoporous silica samples. The resulting organic-inorganic hybrids have been incorporated into carbon paste electrodes and applied to the preconcentration electroanalysis of Pb(II). The attractive recognition properties of these cyclam derivatives functionalized with amide pendent groups toward Pb(II) species and the highly porous structure of the adsorbents can be exploited for the selective and sensitive detection of the target analyte. Various parameters affecting the preconcentration and detection steps have been discussed with respect to the composition and pH of both accumulation and detection media, the nature of the adsorbent (number of silylated groups linking the macrocycle to silica, texture of materials), the accumulation time, and the presence of interfering cations. Under optimal conditions and for 2,min accumulation at open-circuit, the voltammetric response increased linearly with the Pb(II) concentration in a range extending from 2×10,7 to 10,5,M, while a longer accumulation time of 15,min afforded a linear calibration curve between 10,8 and 10,7,M with a detection limit of 2.7×10,9,M which is well below the European regulatory limit of lead in consumption water. [source] On-line concentration of peptides and proteins with the hyphenation of polymer monolithic immobilized metal affinity chromatography and capillary electrophoresisELECTROPHORESIS, Issue 11 2005Lingyi Zhang Abstract An iminodiacetic acid (IDA)-type adsorbent is prepared at the one end of a capillary by covalently bonding IDA to the monolithic rods of macroporous poly(glycidyl methacrylate,co -ethylene dimethacrylate). Cu(II) is later introduced to the support via the interaction with IDA. By this means, polymer monolithic immobilized metal affinity chromatography (IMAC) materials are prepared. With such a column, IMAC for on-line concentration and capillary electrophoresis (CE) for the subsequent analysis are hyphenated for the analysis of peptides and proteins. The reproducibility of such a column has been proved good with relative standard deviations (RSDs) of dead time of less than 5% for injection-to-injection and 12% for column-to-column (n = 3). Through application on the analysis of standard peptides and real protein samples, such a technique has shown promising in proteome study. [source] Integrated Enzymatic Synthesis and Adsorption of Isomaltose in a Multiphase Fluidized Bed ReactorENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 5 2006M. Ergezinger Abstract Dextransucrase catalyzes the formation of dextran, but also of numerous oligosaccharides from sucrose and different acceptors, if appropriate conditions are chosen. A process on a technical scale with immobilized enzyme was established to produce isomaltose, a disaccharide of industrial interest. Isomaltose is also a reactant for dextransucrase and has to be quickly taken out of the reaction solution. This was realized by integrated adsorption of isomaltose on zeolites. In the case of biotransformation the reactor works with a fluidized bed of immobilized enzyme and the in situ separation is realized with a suspension flow of adsorbent. This process was investigated experimentally and theoretically. With a design model consisting of hydrodynamics, kinetics of enzymatic synthesis, and thermodynamics of adsorption, a comparison was made between experimental and calculated data. [source] Association of europium(III), americium(III), and curium(III) with cellulose, chitin, and chitosanENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2006Takuo Ozaki Abstract The association of trivalent f-elements,Eu(III), Am(III), and Cm(III),with cellulose, chitin, and chitosan was determined by batch experiments and time-resolved, laser-induced fluorescence spectroscopy (TRLFS). The properties of these biopolymers as an adsorbent were characterized based on speciation calculation of Eu(III). The adsorption study showed that an increase of the ionic strength by NaCl did not affect the adsorption kinetics of Eu(III), Am(III), and Cm(III) for all the biopolymers, but the addition of Na2CO3 significantly delayed the kinetics because of their trivalent f-element complexation with carbonate ions. It also was suggested from the speciation calculation study that all the biopolymers were degraded under alkaline conditions, leading to their masking of the adsorption of Eu(III), Am(III), and Cm(III) on the nondegraded biopolymers. The masking effect was higher for cellulose than for chitin and chitosan, indicating that of the three, cellulose was degraded most significantly in alkaline solutions. Desorption experiments suggested that some portion of the adsorbed Eu(III) penetrated deep into the matrix, being isolated in a cavity-like site. The TRLFS study showed that the coordination environment of Eu(III) is stabilized mainly by the inner spherical coordination in chitin and by the outer spherical coordination in chitosan, with less association in cellulose in comparison to chitin and chitosan. These results suggest that the association of these biopolymers with Eu(III), Am(III), and Cm(III) is governed not only by the affinity of the functional groups alone but also by other factors, such as the macromolecular steric effect. The association of degraded materials of the biopolymers also should be taken into consideration for an accurate prediction of the influence of biopolymers on the migration behavior of trivalent f-elements. [source] Base-Induced Formation of Two Magnesium Metal-Organic Framework Compounds with a Bifunctional Tetratopic LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2008Pascal D. C. Dietzel Abstract Two coordination polymers constructed from magnesium and the tetratopic organic linker 2,5-dihydroxyterephthalic acid are reported, denominated CPO-26-Mg and CPO-27-Mg. The organic component carries two different types of protic functional groups. The degree of deprotonation of the organic component can be regulated by the amount of sodium hydroxide employed in the synthesis, thus determining which of the compounds forms. In CPO-26-Mg, only the carboxylic acid groups of the linker are deprotonated and take part in the construction of the three-dimensional framework. The structure is non-porous, and its topology is based on the PtS net. In CPO-27-Mg, both the carboxylic acid and the hydroxy groups are deprotonated and involved in the construction of a microporous three-dimensional framework which is based on a honeycomb motif containing large solvent-filled channels. The metal atoms are arranged in chiral chains along the intersection of the honeycomb and contain one water molecule in their coordination sphere, which allows for the creation of coordinatively unsaturated metal sites upon dehydration. CPO-27-Mg is a potentially useful lightweight adsorbent with a pore volume of 60,% of the total volume of the structure and an apparent Langmuir surface area of up to 1030 m2,g,1. Its thermal stability was investigated by thermogravimetry and variable-temperature powder X-ray diffraction, which shows framework degradation to commence at 160 °C in air, at 235 °C under nitrogen, and at 430 °C in a dynamic vacuum. Thermogravimetric dehydration and re-hydration experiments at miscellaneous temperatures indicate that it is possible to obtain open metal sites in CPO-27-Mg, but the water is more tightly bound in this material than in the previously reported isostructural nickel compound.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Influence of silica gel in production of diacylglycerol via enzymatic glycerolysis of palm oleinEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 6 2009Chiou Moi Yeoh Abstract Enzymatic glycerolysis was explored in this paper for the production of diacylglycerol (DAG) oils from palm olein. Three commercial enzymes, Lipozyme TL,IM, Lipozyme RM,IM and Novozym 435 were used for their ability to synthesize DAG in a solvent-free system. Novozym 435 was found to be the more effective enzyme, resulting in a high DAG production even in the absence of an adsorbent such as silica gel. The yields of DAG were between 43 and 50,wt-%. Lipozyme TL,IM and RM,IM, being supported on hydrophilic materials, require an adsorbent to allow slow release of glycerol for reaction with the enzyme and oil. In the absence of silica, no reaction was observed. The success of the reaction is therefore very dependent on the amount of silica used. The yields of DAG using Lipozyme TL,IM and RM,IM were 52 and 45,wt-%, respectively. In addition, the degree of reduction in tocopherols and tocotrienols appeared correlated with the efficacy of the glycerolysis reaction. Changes in the slip melting points and solid fat contents of the products are indicative of the reaction occurring. [source] Determination of surface area of soil by adsorption methodsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2002E. A. Ferreiro Summary How significant are estimates of surface areas of soils obtained by adsorption methods? To answer this we tested the applicability of an equation that relates monolayer coverage (N) of an adsorbent with the area (A) of adsorbate, NAz = k, for six soil samples using six adsorbates of different sizes. The data obtained confirm the validity of the equation with the z parameter ranging between 1.25 and 1.41. Hence each soil sample showed preferences towards small-sized adsorbates for which the product NA (calculated surface area) is inversely related to the size of adsorbate. We also demonstrated that the equation has roots in the Langmuir adsorption equation. [source] Calcite-specific coupling protein in barnacle underwater cementFEBS JOURNAL, Issue 24 2007Youichi Mori The barnacle relies for its attachment to underwater foreign substrata on the formation of a multiprotein complex called cement. The 20 kDa cement protein is a component of Megabalanus rosa cement, although its specific function in underwater attachment has not, until now, been known. The recombinant form of the protein expressed in bacteria was purified in soluble form under physiological conditions, and confirmed to retain almost the same structure as that of the native protein. Both the protein from the adhesive layer of the barnacle and the recombinant protein were characterized. This revealed that abundant Cys residues, which accounted for 17% of the total residues, were in the intramolecular disulfide form, and were essential for the proper folding of the monomeric protein structure. The recombinant protein was adsorbed to calcite and metal oxides in seawater, but not to glass and synthetic polymers. The adsorption isotherm for adsorption to calcite fitted the Langmuir model well, indicating that the protein is a calcite-specific adsorbent. An evaluation of the distribution of the molecular size in solution by analytical ultracentrifugation indicated that the recombinant protein exists as a monomer in 100 mm to 1 m NaCl solution; thus, the protein acts as a monomer when interacting with the calcite surface. cDNA encoding a homologous protein was isolated from Balanus albicostatus, and its derived amino acid sequence was compared with that from M. rosa. Calcite is the major constituent in both the shell of barnacle base and the periphery, which is also a possible target for the cement, due to the gregarious nature of the organisms. The specificity of the protein for calcite may be related to the fact that calcite is the most frequent material attached by the cement. [source] Solid-phase aroma concentrate extraction (SPACEÔ ): a new headspace technique for more sensitive analysis of volatilesFLAVOUR AND FRAGRANCE JOURNAL, Issue 3 2004Masashi Ishikawa Abstract The SPACEÔ (solid-phase aroma concentrate extraction) method is a modi,ed version of the SPME (solid-phase micro extraction) technique for headspace analysis, with increased area of the adsorbent to enable more sensitive analysis of volatiles. The SPACEÔ rod used in the technique is fabricated from stainless steel coated with an adsorbent mixture, consisting mainly of a graphite carbon. Initially, the SPACEÔ rod is ,xed in the head of a closed ,ask, where it adsorbs the aroma. Next, the rod is thermally desorbed on-line with a high-resolution gas chromatography,mass spectrometer (HRGC,MS). In the present experiments, SPACEÔ sampling reproducibility was determined by analysing a standard mixture and roasted coffee beans. The SPACEÔ rod collected the analytes with good reproducibility, with the exception of high polar compounds. Similar analyses of coffee powder were performed by SPME and other methods for comparison with the SPACEÔ method. The SPACEÔ method proved to have superior capabilities with high concentrations, and it produced a well-balanced chromatogram. Copyright © 2004 John Wiley & Sons, Ltd. [source] Synthesis,Structure,Property Relationships for Hyperbranched Aminosilica CO2 AdsorbentsADVANCED FUNCTIONAL MATERIALS, Issue 23 2009Jeffrey H. Drese Abstract Hyperbranched aminosilica (HAS) adsorbents are prepared via the ring-opening polymerization of aziridine in the presence of mesoporous silica SBA-15 support. The aminopolymers are covalently bound to the silica support and capture CO2 reversibly in a temperature swing process. Here, a range of HAS materials are prepared with different organic loadings. The effects of organic loading on the structural properties and CO2 adsorption properties of the resultant hybrid materials are examined. The residual porosity in the HAS adsorbents after organic loading, as well as the molecular weights and degrees of branching for the separated aminopolymers, are determined to draw a relationship between adsorbent structure and performance. Humid adsorption working capacities and apparent adsorption kinetics are determined from experiments in a packed-bed flow system monitored by mass spectrometry. Dry adsorption isotherms are presented for one HAS adsorbent with a high amine loading at 35 and 75,°C. These combined results establish the relationships between adsorbent synthesis, structure, and CO2 adsorption properties of the family of HAS materials. [source] Computational study of a novel continuous solar adsorption chiller: performance prediction and adsorbent selectionINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2007Evan Voyiatzis Abstract A novel solar adsorption chiller intended for domestic use is presented. The chiller can be integrated with existing solar systems based on flat plate collectors, and, contrary to commercial chillers, it operates continuously. A detailed analysis of both the simple and the heat-integrated cycle is carried out so as to select the optimal adsorbent and operating conditions. The employed integral thermodynamic model takes into account the inert masses that limit the performance of the chiller, such as the metal frame, the thermo-fluid, and the non-adsorbed steam, by introducing heat capacity effects. Given the adsorption equilibrium data, the energy balances, the performance, and the useful thermal loads of the system can be calculated at any operating conditions. The results indicate that silica gel Type A is a more efficient adsorbent compared to silica gel Type RD or Type 3A. Furthermore, the total porosity has a slight effect on system performance, while optimal operation can be achieved when the condenser temperature is less than 326 K and the evaporator temperature greater than 280 K. Copyright © 2006 John Wiley & Sons, Ltd. [source] Potential uses and applications of treated wine waste: a reviewINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 5 2006Ioannis S. Arvanitoyannis Summary Recently, there has been an upsurge in the exploitation of the waste materials generated by the wine industry. Wine waste is characterised by the presence of natural antioxidants much safer than synthetic antioxidants. Wine waste-derived antioxidants have been recently used in the food industry. Moreover, wine waste can be potentially used as soil conditioner, as adsorbent for heavy metals, for fertiliser and for pullulan production. This review aims at presenting the most important and economically viable applications of treated wine waste. [source] Therapeutic effects of long-term administration of an oral adsorbent in patients with chronic renal failure: two-year studyINTERNATIONAL JOURNAL OF UROLOGY, Issue 1 2005NOBUYOSHI TAKAHASHI Abstract Background:, Kremezin is an oral adsorbent that attenuates the progression of chronic renal failure by removing uremic toxins and their precursors from the gastrointestinal tract. Previously two clinical studies based on reciprocal serum creatinine levels (1/Scr) have confirmed the efficacy of Kremezin (Kureha Chemical, Tokyo, Japan) in undialyzed patients who had been followed up for 6 months or 1 year. This is the first report to evaluate the therapeutic effects of long-term administration (2 years.) of Kremezin in undialyzed patients. Methods:, Kremezin was given to 48 enrolled undialyzed patients with a median Scr level of 4.3 mg/dL. Rates of decline of 1/Scr, as well as the time for Scr level to reach 10 mg/dL, the critical value requiring dialysis, were compared before and after administration of Kremezin. Results:, During the 2-year therapeutic period, 1/Scr gradients were significantly attenuated (P = 0.0083), and the estimated time to dialysis was prolonged from 16.3 ± 16.3 months to 29.8 ± 24.1 months (P = 0.002). When the patients were divided into two groups, based on of systolic blood pressure (SBP), defined by the World Health Organization (WHO) classification, a significantly smaller number of patients in the low blood pressure group (SBP < 160 mmHg) were introduced to dialysis (P = 0.0005), and the estimated time to dialysis was significantly extended in the low blood pressure group (P = 0.0125). Conclusion:, In addition to the control of blood pressure in undialyzed patients, Kremezin has additive salutary effects to halt the progressive loss of renal function, resulting in the delay of dialysis. [source] A study of the mechanisms of divalent copper binding to a modified cellulose adsorbentJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010David William O'Connell Abstract A modified cellulose material was prepared by grafting glycidyl methacrylate to cellulose (Cell- g -GMA) with subsequent functionalization with imidazole (Cell- g -GMA-imidazole). This latter compound was used in the adsorption of copper from aqueous solution. The mechanism of Cu(II) binding onto the cell- g -GMA-imidazole was investigated at the molecular level using scanning electron microscopy (SEM), Fourier transform infrared (FTIR), x-ray photoelectron spectroscopy (XPS), energy dispersive x-ray analysis (EDX) and X-ray diffraction (XRD). FTIR and Raman spectroscopy provided an insight into the extent to which perturbation of the imidazole ring occurred following adsorption of the metal while XPS spectra indicated the binding of Cu(II) ions to nitrogen atoms by the appearance of additional binding energy peaks for nitrogen on the cellulose- g -GMA-imidazole sample post adsorption. The EDX technique provided clear evidence of the physical presence of both the copper and sulfate on the cellulose- g -GMA-imidazole material post adsorption. XRD analysis further confirmed the presence of a copper species in the adsorbent material as copper sulfate hydroxide (Cu3(OH)4SO4 - antlerite). The XRD studies further suggest that the overall extent of Cu(II) adsorption is not alone a combination of true metal chelation as suggested by FTIR, Raman and XPS, but also a function of surface precipitation of the polynuclear copper species. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Preparation and adsorption behavior of a cellulose-based, mixed-mode adsorbent with a benzylamine ligand for expanded bed applicationsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Dong Gao Abstract A novel mixed-mode expanded bed adsorbent with anion-exchange properties was explored with benzylamine as the functional ligand. The cellulose composite matrix, densified with stainless steel powder, was prepared with the method of water-in-oil suspension thermal regeneration. High activation levels of the cellulose matrix were obtained with allyl bromide because of the relative inertness of the allyl group under the conditions of the activation reaction. After the formation of the bromohydrin with N -bromosuccinimide and coupling with benzylamine, the activated matrix was derived to function as a mixed-mode adsorbent containing both hydrophobic and ionic groups. The protein adsorption capacity was investigated with bovine serum albumin as a model protein. The results indicated that the prepared adsorbent could bind bovine serum albumin with a high adsorption capacity, and it showed salt tolerance. Effective desorption was achieved by a pH adjustment across the isoelectric point of the protein. The interactions between the cell and adsorbent were studied, and the bioadhesion was shielded by the adjustment of the salt concentration above 0.1M. Stable fluidization in the expanded bed was obtained even in a 2% (dry weight) yeast suspension. The direct capture of target proteins from a biomass-containing feedstock without extra dilution steps could be expected with the mixed-mode adsorbent prepared in this work, and this would be especially appropriate for expanded bed adsorption applications. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] A study on the sorption of NO3, and F, on the carboxymethylated starch-based hydrogels loaded with Fe2+ ionsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Ghanshyam S. Chauhan Abstract Using the principle of geochemistry of fluoride, green and cost effective anion adsorbents were developed for the removal of F, from water systems. The scheme was further applied for the removal of NO3, also. Carboxymethylated starch functionalized through network formation with acrylamide was used as adsorbent, and the resultant hydrogels were loaded with Fe2+ ions to generate anchorage for the anions. Sorption of Fe2+ was studied as a function of different factors such as time, temperature, pH, and ion strength. The network having the highest Fe2+ uptake was loaded with the Fe2+ ions under optimum conditions and used for the sorption of F, and NO3,. High efficiency has been observed for F,, as even up to 100% uptake has been observed within just 10 minutes. The support shows high selectivity for NO3,, which was used as anion reference. Thermodynamics of sorption confirms low order and low energy processes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Optimization and analysis of nickel adsorption on microwave irradiated rice husk using response surface methodology (RSM)JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2009Magesh Ganesa Pillai Abstract BACKGROUND: The removal of heavy metals using adsorption techniques with low cost biosorbents is being extensively investigated. The improved adsorption is essentially due to the pores present in the adsorbent. One way of improving the porosity of the material is by irradiation of the precursor using microwaves. In the present study, the adsorption characteristics of nickel onto microwave-irradiated rice husks were studied and the process variables were optimized through response surface methodology (RSM). RESULT: The adsorption of nickel onto microwave-irradiated rice husk (MIRH) was found to be better than that of the raw rice husk (RRH). The kinetics of the adsorption of Ni(II) from aqueous solution onto MIRH was found to follow a pseudo-second-order model. Thermodynamic parameters such as standard Gibbs free energy (,G°), standard enthalpy (,H°), and standard entropy (,S°) were also evaluated. The thermodynamics of Ni(II) adsorption onto MIRH indicates that it is spontaneous and endothermic in nature. The response surface methodology (RSM) was employed to optimize the design parameters for the present process. CONCLUSION: Microwave-irradiated rice husk was found to be a suitable adsorbent for the removal of nickel(II) ions from aqueous solutions. The adsorption capacity of the rice husk was found to be 1.17 mg g,1. The optimized parameters for the current process were found as follows: adsorbent loading 2.8 g (100 mL),1; Initial adsorbate concentration 6 mg L,1; adsorption time 210 min.; and adsorption temperature 35 °C. Copyright © 2008 Society of Chemical Industry [source] Adsorption of fulvic acids from aqueous solutions by carbon nanotubesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2007Shu-Guang Wang Abstract Carbon nanotubes (CNTs) were used as adsorbent to remove fulvic acids (FA) from aqueous solutions. The adsorption capacity of CNTs for FA can reach 24 mg g,1 at 5 °C and equilibrium concentration of 18 mg dm,3. The kinetic and thermodynamic parameters, such as rate of adsorption, standard free energy changes (,G0), standard enthalpy change (,H0) and standard entropy change (,S0), have been obtained. Acidic conditions (pH = 2,5) favor FA removal. An increase in the ionic strength or the addition of divalent cations increase the adsorption of FA dramatically (FA = 60 mg dm,3). An increase in the maximum adsorbed amount of FA was observed when treating FA in synthetic seawater. Desorption studies reveal that FA can be easily and quickly removed from CNTs by altering the pH values of the solution. Good adsorption capacity and quick desorption indicate that CNTs are a promising adsorbent to remove FA from aqueous solutions. Copyright © 2007 Society of Chemical Industry [source] A modified cellulose adsorbent for the removal of nickel(II) from aqueous solutionsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2006David W O'Connell Abstract A series of adsorption studies was carried out on a glycidyl methacrylate- modified cellulose material functionalised with imidazole (Cellulose- g -GMA-Imidazole) to assess its capacity in the removal of Ni(II) ions from aqueous solution. The study sought to establish the effect of a number of parameters on the removal of Ni(II) from solution by the Cellulose- g -GMA-Imidazole. In particular, the influence of initial metal concentration, contact time, solution temperature and pH were assessed. The studies indicated a Ni(II) uptake on the Cellulose- g -GMA-Imidazole sorbent of approximately 48 mg g,1 of nickel from aqueous solution. The adsorption process fitted the Langmuir model of adsorption and the binding process was mildly endothermic. The kinetics of the adsorption process indicated that nickel uptake occurred within 400 min and that pseudo-second order kinetics best describe the overall adsorption process. Nickel(II) adsorption, recovery and re-adsorption studies indicated that at highly acidic pH values the adsorbent material becomes unstable, but in the range pH 3,6, the adsorbent is stable and shows limited but significant Ni(II) recovery and re-adsorption capability. Copyright © 2006 Society of Chemical Industry [source] Comparative studies of Oryza sativa L. husk and chitosan as lead adsorbentJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2006Mohamed Mohamed Daud Zulkali Abstract The adsorption capacity of two low-cost adsorbents, Oryza sativa L. husk and chitosan, was studied. Lead solution was used as the adsorbate. The effect of initial lead concentration, pH, temperature, weight of adsorbent, particle size and contact time on lead uptake was investigated. It was found that the isotherm data were well described by the Freundlich isotherm for both adsorbents. The adsorption capacities of rice husk and chitosan were 5.69 and 8.31 mg g,1, respectively. It was shown that chitosan was more effective than rice husk. Copyright © 2005 Society of Chemical Industry [source] Novel hydrogel composite for the removal of water-soluble cationic dyeJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2006Li-Ming Zhang Abstract A novel hydrogel composite was prepared by incorporating Laponite RDS clay into poly(acrylic acid- co - N -vinyl-2-pyrrolodone) hydrogel during in - situ polymerization, and investigated with respect to its adsorption kinetics and isotherm toward Crystal Violet, a widely used cationic dye. It was found that the adsorption kinetics of Crystal Violet onto the hydrogel composite was consistent with the pseudo-second-order model. Compared with pure hydrogel, the hydrogel composite is characterized by greater amounts being adsorbed at equilibrium, and a higher rate constant and initial adsorption rate. By analyzing the experimental data using the Langmuir isotherm equation, an enhanced adsorption capacity was found for the hydrogel composite. Such material is expected to be a good adsorbent for water pollutants such as cationic dyes and treatment of these organic contaminants from wastewater. Copyright © 2006 Society of Chemical Industry [source] | |||||||||||||||||||||||||||||||||||||