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Sorbent
Kinds of Sorbent Terms modified by Sorbent Selected AbstractsH2xMnxSn3-xS6 (x,=,0.11,0.25): A Novel Reusable Sorbent for Highly Specific Mercury Capture Under Extreme pH ConditionsADVANCED FUNCTIONAL MATERIALS, Issue 7 2009Manolis J. Manos Abstract The H2xMnxSn3-xS6 (x,=,0.11,0.25) is a new solid acid with a layered hydrogen metal sulfide (LHMS). It derives from K2xMnxSn3,xS6 (x,=,0.5,0.95) (KMS-1) upon treating it with highly acidic solutions. We demonstrate that LHMS-1 has enormous affinity for the very soft metal ions such as Hg2+ and Ag+ which occurs via a rapid ion exchange process. The tremendous affinity of LHMS-1 for Hg2+ is reflected in very high distribution coefficient KdHg values (>106,mL g,1). The large affinity and selectivity of LHMS-1 for Hg2+ persists in a very wide pH range (from less than zero to nine) and even in the presence of highly concentrated HCl and HNO3 acids. LHMS-1 is significantly more selective for Hg2+ and Ag+ than for the less soft cations Pb2+ and Cd2+. The Hg2+ ions are immobilized in octahedral sites between the sulfide layers of the materials via Hg,S bonds as suggested by pair distribution function (PDF) analysis. LHMS-1 could decrease trace concentrations of Hg2+ (e.g. <100,ppb) to well below the acceptable limits for the drinking water in less than two min. Hg-laden LHMS-1 shows a remarkable hydrothermal stability and resistance in 6,M HCl solutions. LHMS-1 could be regenerated by treating Hg-loaded samples with 12,M HCl and re-used without loss of its initial exchange capacity. [source] Direct automatic determination of free and total anesthetic drugs in human plasma by use of a dual (microdialysis,microextraction by packed sorbent) sample treatment coupled at-line to NACE,MSELECTROPHORESIS, Issue 10 2009Gabriel Morales-Cid Abstract This paper reports for the first time the use of microextraction by packed sorbent in combination with CE. The combined system was used to determine anesthetic drugs in human plasma. A microdialysis fiber was coupled on-line to the microextraction unit in order to distinguish between free and total concentrations of drugs. The system was automated by connecting the microextraction unit to a syringe pump and interfacing it to a computer. The ensuing method allows the determination of 10,,g/L concentrations of free drugs and 1,,g/L concentrations of total drugs from only 200,,L of sample with an RSD of less than 9%. [source] Determination of flurbiprofen enantiomers in plasma using a single-isomer amino cyclodextrin derivative in nonaqueous capillary electrophoresis,ELECTROPHORESIS, Issue 17 2008Anne Rousseau Abstract A nonaqueous capillary electrophoresis (NACE) assay was developed for the separation and determination of flurbiprofen enantiomers in plasma samples using 6-monodeoxy-6-mono(3-hydroxy)propylamino-,-cyclodextrin as chiral selector. The nonaqueous background electrolyte was made up of 40,mM ammonium acetate in methanol (MeOH), and flufenamic acid was employed as internal standard. Solid-phase extraction was used for sample cleanup prior to the NACE separation. The NACE method reproducibility was optimized by evaluating different capillary washing sequences between runs. After having tested various conditions, trifluoroacetic acid (1,M) in MeOH was finally selected. Concerning the solid-phase extraction procedure, good and reproducible analyte recoveries were obtained using MeOH for protein denaturation and a polymeric phase combining hydrophobic interactions with anion exchange properties (Oasis® MAX) was selected as extraction sorbent. The method selectivity was not only demonstrated toward a blank plasma sample but also toward other non-steroidal anti-inflammatory drugs. The method was then successfully validated with respect to response function, trueness, precision, accuracy, linearity and limit of quantification. [source] Combined use of supported liquid membrane and solid-phase extraction to enhance selectivity and sensitivity in capillary electrophoresis for the determination of ochratoxin A in wineELECTROPHORESIS, Issue 7 2008Sara Almeda Abstract This paper proposes a novel strategy to enhance selectivity and sensitivity in CE, using supported liquid membrane (SLM) and off-line SPE simultaneously. The determination of ochratoxin A (OA) in wine has been used to demonstrate the potential of this methodology. In the SLM step, the donor phase (either a 20,mL volume of a standard solution at pH,1 or a wine sample at pH,8) was placed in a vial, where a micromembrane extraction unit accommodating the acceptor phase (1,mL water, pH,11) in its lumen was immersed. The SLM was constructed by impregnating a porous Fluoropore Teflon (PTFE) membrane with a water-immiscible organic solvent (octanol). In the off-line SPE step, the nonpolar sorbent (C-18, 4,mg) selectively retained the target ochratoxin, enabling small volumes of acceptor phase (1,mL) to be introduced. The captured analytes were eluted in a small volume of methanol (0.1,mL). This procedure resulted in sample cleanup and concentration enhancement. The method was evaluated for accuracy and precision, and its RSD found to be 5%. The LODs for OA in the standard solutions and wine samples were 0.5 and 30,,g/L, respectively. The results obtained demonstrate that SLM combined with off-line is a good alternative to the use of immunoaffinity columns prior to CE analysis. [source] In-capillary solid-phase extraction,capillary electrophoresis for the determination of chlorophenols in waterELECTROPHORESIS, Issue 16 2006Luo-Hong Zhang Abstract A novel CE method combined with SPE in a single capillary was developed for analysis of chlorophenols in water. A frit of 0.5,mm was first made by a sol-gel method, followed by packing a SPE sorbent in the inlet end of the capillary. Two phenol derivatives, 2,4-dichlorophenol and 2,4,5-trichlorophenol, were used as the model compounds. By loading sample solutions into the capillary, the two chlorophenols were extracted into the sorbent. They were desorbed by injecting only about 4,nL of methanol. Finally, the analytes were separated by conventional CE. The technique provided a concentration enhancement factor of over 4000-fold for both chlorophenols. The detection limits (S/N,=,3) of 2,4-dichlorophenol and 2,4,5-trichlorophenol were determined to be 0.1,ng/mL and 0.07,ng/mL, respectively. For replicate analyses of 5,ng/mL of 2,4-dichlorophenol, within-day and between-day RSDs of migration time, peak height and peak area were in the range of 1.8,2.0%, 4.0,4.4% and 4.1,4.6%, respectively. The method shows wide linear range, acceptable reproducibility and excellent sensitivity, and it was applied to the analyses of spiked river water samples. The capillary packed with the SPE sorbents can be used for more than 400 runs without performance deterioration. [source] Validation of a modified Flory-Huggins concept for description of hydrophobic organic compound sorption on dissolved humic substancesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 9 2002Anett Georgi Abstract Sorption coefficients(KDOC) on dissolved organic matter (DOM) have been determined by means of solid-phase microextraction (SPME) for hydrophobic organic compounds (HOCs) of various classes, for example, polycyclic aromatic hydrocarbons (PAHs), noncondensed arenes, and alkanes. Relating the KDOC values obtained to the octanol-water partition coefficients of the solutes results in class-specific correlations. Obviously, PAHs have a higher affinity to DOM than other HOCs with equal KOW values. The different KDOC to KOW correlations can be combined into one general formula based on a modified Flory-Huggins concept. It permits the calculation of sorption coefficients from the solubility parameters (,) and KOW values of the solutes and the solubility parameter of the sorbent. The latter value, which is specific to the DOM under consideration, can be determined from a single measured sorption coefficient. By applying the proposed Flory-Huggins concept, which is based on the presumption of nonspecific interactions between HOCs and DOM, the different affinities of PAHs, noncondensed arenes, and alkanes to DOM can be accurately predicted. [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] Preparation and Characteristics of Esculin-Imprinted PolymersHELVETICA CHIMICA ACTA, Issue 6 2007Guo-Song Wang Abstract Four molecularly imprinted polymers (MIPs) were prepared in MeOH with esculin (=6,7-dihydroxycoumarin 6-(, - D -glucopyranoside)=6-(, - D -glucopyranosyloxy)-7-hydroxy-2H -1-benzopyran-2-one) as the imprinted molecule, methacrylic acid (=2-methylprop-2-enoic acid; MAA), acrylamide (=prop-2-enamide; AM), 4-vinylpyridine (=4-ethenylpyridine; 4-VP), or 2-vinylpyridine (=2-ethenylpyridine; 2-VP) as the functional monomer, respectively, as well as ethylene glycol dimethacrylate (=2-methylprop-2-enoic acid ethane-1,2-diyl ester; EGDMA) as the cross-linking agent. The interaction between the template and the functional monomers was investigated by fluorescence and UV spectrophotometry, respectively, which revealed the presence of esculin/monomer complexes in the stoichiometric ratio 1,:,2 in the pre-polymerization mixture. The resultant polymers were studied in equilibrium binding experiments to evaluate the recognition ability and the binding capacity towards esculin. The results showed that MIP1, prepared with MAA as the functional monomer, exhibited advantageous characteristics of high binding capacity, optimal imprinting effect, and good selectivity towards esculin. The Scatchard analysis indicated that there are two types of binding sites in MIP1, and its binding parameters including the apparent maximum numbers of binding sites and the dissociation constants were calculated. Finally, by packing an SPE column (SPE=solid-phase extraction) with MIP1, the esculin was separated and enriched successfully by this sorbent from samples of Cortex fraxini, and the average recovery was up to 74.7%. [source] Prediction of hemodialysis sorbent cartridge urea nitrogen capacity and sodium release from in vitro testsHEMODIALYSIS INTERNATIONAL, Issue 2 2008Benjamin P. ROSENBAUM Abstract In sorbent-based hemodialysis, factors limiting a treatment session are urea conversion capacity and sodium release from the cartridge. In vitro experiments were performed to model typical treatment scenarios using various dialyzers and 4 types of SORBÔ sorbent cartridges. The experiments were continued to the point of column saturation with ammonium. The urea nitrogen removed and amount of sodium released in each trial were analyzed in a multi-variable regression against several variables: amount of zirconium phosphate (ZrP), dialysate flow rate (DFR), simulated blood flow rate (BFR), simulated patient whole-body fluid volume (V), initial simulated patient urea concentration (BUNi), dialyzer area permeability (KoA) product, initial dialysate sodium and bicarbonate (HCO3i) concentrations, initial simulated patient sodium (Nai), pH of ZrP, creatinine, breakthrough time, and average urea nitrogen concentration in dialysate. The urea nitrogen capacity (UNC) of various new SORBÔ columns is positively related to ZrP, BFR, V, BUNi, and ZrP pH and negatively to DFR with an R2adjusted=0.990. Two models are described for sodium release. The first model is related positively to DFR and V and negatively to ZrP, KoA product, and dialysate HCO3i with an R2adjusted=0.584. The second model incorporates knowledge of initial simulated patient sodium (negative relationship) and urea levels (negative relationship) in addition to the parameters in the first model with an R2adjusted=0.786. These mathematical models should allow for prediction of patient sodium profiles and the time of column urea saturation based on simple inputs relating to patient chemistries and the dialysis treatment. [source] Electrosynthesized Surface-Imprinted Conducting Polymer Microrods for Selective Protein RecognitionADVANCED MATERIALS, Issue 22 2009Anna Menaker Novel surface-imprinted conducting polymer microrods are shown to selectively recognize the template protein, as demonstrated by competitive binding assays using fluorescence detection. The electrochemical template synthesis provides means for controlled fabrication and spatial confinement of the PEDOT/PSS polymer proposed in this work, which exhibits extraordinary low nonspecific interactions and is effectively turned into a selective protein sorbent upon imprinting. [source] Expression of HYAL2 mRNA, hyaluronan and hyaluronidase in B-cell non-Hodgkin lymphoma: Relationship with tumor aggressivenessINTERNATIONAL JOURNAL OF CANCER, Issue 2 2005Philippe Bertrand Abstract Hyaluronidases and their substrate, hyaluronan (HA), were mainly explored in solid tumors but rarely in hematologic malignancies. While HA involvement was demonstrated in invasion and metastasis in most cases of solid tumors, the role of hyaluronidases in cancer progression remains controversial. One of the hyaluronidases, HYAL2, is suspected to be involved in the first step of HA degradation. In this work, HYAL2 mRNA, HA and total hyaluronidases expression were examined in lymphoma tissue extracts and correlated to the lymphoma subtype. Real-time RT-PCR was performed to evaluate HYAL2 mRNA. HA and hyaluronidase were assayed by enzyme-linked sorbent assay. Our results showed that HYAL2 mRNA expression was correlated to lymphoma diagnosis (p = 6 × 10,3) and was significantly lower in high-grade lymphoma, i.e., diffuse large B-cell diffuse lymphomas (DLBCLs). Several forms of hyaluronidase were detected by zymography and total hyaluronidase activity detected in tissue extracts was not significantly different according to tumor grade. HA levels also correlated to lymphoma subtype (p = 1 × 10,5) and were higher in DLBCLs. Moreover, HYAL2 mRNA and HA expressions were inversely correlated (p = 0.035). HYAL2 gene is localized on chromosome 3p21, which contains candidates tumor suppressor genes. Our results suggest that HYAL2 may have a prognostic significance in lymphomas and an antioncogenic activity. Conversely, HA overexpression in high-grade lymphomas is in favor of its involvement in tumor development and could provide a useful target for lymphoma therapy using HA-binding peptides. [source] Stability study of inverse suspension copolymerization of 1,1,3,3-tetramethylguandium acrylate and N,N, -methylenebisacrylamideJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010Jie Dong Abstract In a previous study, we synthesized crosslinked P(TMGA- co -MBA) via an inverse suspension copolymerization of 1,1,3,3-tetramethylguandium acrylate (TMGA) and N,N,-methylenebisacrylamide (MBA) and found that the product is a good SO2 sorbent. However, the polymerization stability appeared to be poor under some reaction conditions and is far from being elucidated. In this study, the inverse suspension copolymerization was carried out using cyclohexane as solvent, Span60 as dispersant, and ammonium persulfate (APS) as initiator. The effects of the reaction conditions such as stirring speed, dispersant concentration, and temperature on the polymerization stability and particle size were systematically examined. It is found that the polymerization stability is a strong function of these parameters. Stable crosslinked poly(TMGA- co -MBA) particles from micrometer to millimeter diameters were synthesized under optimized conditions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Preparation and sorption studies of ,-cyclodextrin/epichlorohydrin copolymersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Dawn Y. Pratt Abstract ,-Cyclodextrin (,-CD) copolymer materials were synthesized by reacting different mole ratios (1 : 15, 1 : 25 and 1 : 35) of ,-CD with epichlorohydrin (EP). The products were characterized using N2 porosimetry, Fourier Transform Infrared spectroscopy, 13C CP-MAS NMR spectroscopy, thermogravimetry analysis, elemental (C and H) analysis, and scanning electron microscopy. The sorption properties in aqueous solution were studied using p-nitrophenol (PNP) with UV,Vis spectrophotometry. Sorption isotherms were obtained at pH 4.6 and three temperatures (22, 35, and 45°C) and at pH 10.3 at 22°C. The isotherms were analyzed using the BET isotherm model and the sorption parameters provided estimates of the surface area, sorption capacity, and isosteric heats of sorption for each polymeric material. The estimated surface areas are as follows: 58.2, 52.1, and 90.1 m2/g at pH 4.6. At pH 10.3, the estimated surface areas are 44.2, 40.5, and 58.5 m2/g, respectively. The removal efficiency of PNP by the polymeric materials ranged between 4.5 and 58% for the conditions investigated whereas the isosteric heats ranged between ,24.5 and ,13.6 kJ/mol. Removal efficiencies were concluded to strongly depend on the sorption conditions such as pH, temperature, and the relative amounts of sorbent and dye in aqueous solution. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Removal of heavy metals and cyanide from gold mine wastewaterJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2010Mike A. Acheampong Abstract This paper reviews the technology and biotechnology to remove heavy metals (such as copper, arsenic, lead and zinc) and cyanide from contaminated wastewater. The paper places special emphasis on gold mine wastewater and the use of low cost materials as sorbent. Various biological as well as physicochemical treatment processes are discussed and compared on the basis of costs, energy requirement, removal efficiency, limitations and advantages. Sorption using natural plant materials, industrial and agricultural waste has been demonstrated to have the potential to replace conventional methods for the removal of heavy metals because of its cost effectiveness, efficiency and the local availability of these materials as biosorbent. The parameters affecting sorption, such as initial ion concentration, pH, sorbent dosage, particle size and temperature, are discussed. The overall treatment cost of metal and cyanide contaminated wastewater depends on the process employed and the local conditions. In general, technical applicability, cost-effectiveness and plant simplicity are the key factors in selecting the most suitable treatment method. Copyright © 2010 Society of Chemical Industry [source] Sorption of copper by a highly mineralized peat in batch and packed-bed systemsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2010Marta Izquierdo Abstract BACKGROUND: The performance of peat for copper sorption was investigated in batch and fixed-bed experiments. The effect of pH was evaluated in batch experiments and the experimental data were fitted to an equilibrium model including pH dependence. Hydrodynamic axial dispersion was estimated by tracing experiments using LiCl as a tracer. Six fixed-bed experiments were carried out at copper concentrations between 1 and 60 mg dm,3 and the adsorption isotherm in dynamic mode was obtained. A mass transport model including convection,dispersion and sorption processes was applied for breakthrough curve modelling. RESULTS: Maximum uptake capacities in batch mode were 22.0, 36.4, and 43.7 mg g,1 for pH values of 4.0, 5.0, and 6.0, respectively. Uptake capacities in continuous flow systems varied from 36.5 to 43.4 mg g,1 for copper concentrations between 1 and 60 mg dm,3. Dynamic and batch isotherms showed different shapes but a similar maximum uptake capacity. Sorbent regeneration was successfully performed with HCl. A potential relationship between dispersion coefficient and velocity was obtained with dispersion coefficients between 5.00 × 10,8 and 2.95 × 10,6 m2 s,1 for water velocities ranging between 0.56 × 10,4 and 5.03 × 10,4 m s,1. The mass transport model predicted both the breakpoints and the shape of the breakthrough curves. CONCLUSIONS: High retention capacities indicate that peat can be used as an effective sorbent for the treatment of wastewater containing copper ions. Copyright © 2009 Society of Chemical Industry [source] Recovery of pyruvic acid with weakly basic polymeric sorbentsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2008Shaokai Huang Abstract BACKGROUND: Carboxylic acids are among the most important substances that can be manufactured from biomass. However, the recovery of carboxylic acids from fermentation broths presents a challenging separation problem. To avoid the production of waste salts and net consumption of chemicals in the calcium carboxylate salt process, the use of reversible chemical complexation with polymeric sorbents and extractants is attractive for carboxylic acid recovery. Pyruvic acid is widely used in the manufacture of medicines, pesticides and foodstuffs and can be produced by fermentation. Since the acidity of pyruvic acid (pKa = 2.49) is stronger than that of normal carboxylic acids, and as few reports on the recovery of pyruvic acid are available, the sorption of pyruvic acid from aqueous solution on two types of weakly basic polymeric sorbent, tertiary amine D301R and primary amine D392, was investigated over a wide pH range and at various salt (MgSO4) concentrations. RESULTS: Overloading adsorption of pyruvic acid on both weakly basic polymeric sorbents occurred, with the overloading of D392 being greater than that of D301R. The adsorption of pyruvic acid on both sorbents was greatly affected by the solution pH and the salt concentration in the aqueous phase. An overloading model was able to predict the experimental uptake data very well. CONCLUSION: Solution pH is one of the most important operating conditions, and both polymeric sorbents D392 and D301R can be used to recover pyruvic acid from dilute aqueous solution with high efficiency at a solution pH around 2. The uptake by D392 is greater than that by D301R owing to steric hindrance of the tertiary amine. Copyright © 2008 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] Removal of toxic metal ions from aqueous systems by biosorptive flotationJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2002Anastasios I Zouboulis Abstract Biosorptive flotation was used as a combined operation for the simultaneous abstraction of nickel, copper and zinc ions from aqueous streams. Laboratory-scale batch experiments, as well as pilot-scale continuous experiments, have been conducted. Grape stalks, a by-product of the winery industry, were used as sorbent material. The experimental procedure consisted of two consecutive stages: (i) biosorption, and (ii) flotation. The possibility of reusing biomass, after appropriate elution, was also examined. The main parameters examined were biomass concentration, particle size of sorbent, surfactant concentration, pH and flocculation. Flotation removals, following laboratory-scale experiments, were found to be in the order of 100, 85 and 70% for copper, zinc and nickel, respectively. In pilot-scale experiments, biomass sorption capacities were determined as 25 for copper, 81 for zinc and 7,µmol,dm,3 for nickel. The order of biomass affinity regarding the studied metals was Cu,>,Zn,>,Ni. Short retention time and high effectiveness suggest that biosorptive flotation is a promising treatment process for the removal of toxic metals from contaminated aqueous solutions. © 2002 Society of Chemical Industry [source] Application of a carbon sorbent for the removal of cadmium and other heavy metal ions from aqueous solutionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2002I El-Shafey Abstract Treatment of flax shive with sulfuric acid produces a carbonaceous material that has been used to remove metal ions from aqueous solution. Metal ions including Cd(II), Cu(II), Cr(III), Co(II), Ni(II), Zn(II) and Pb(II) have been investigated for kinetic behaviour and sorption capacities. These metal ions show fast sorption kinetics following a first order rate equation. Cadmium was chosen as representative of these metal ions and a detailed study was carried out. The effect of pH on sorption was studied and it was found that maximum uptake occurred above pH 3,7, sorption was accompanied by release of protons into the solution and a ratio of [H+] released to [Cd2+] sorbed of approximately 2 was found. The sorption capacity showed no significant increase with increase of temperature. The presence of other metal ions such as K+, Na+, Mg2+ and Ca2+ decreases the Cd(II) capacity, indicating competition for the ion exchange sites. Successive sorption of Cd(II) shows that the capacity exceeds the monolayer capacity calculated from the Langmuir equation. Column studies showed good performance over a total of seven cycles of loading/stripping. These studies indicate that the sorption mechanism for these metal ions is related to a reversible ion exchange process on the carbon surface. © 2002 Society of Chemical Industry [source] Sorption of tannic acid on zirconium pillared clayJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2002P Vinod Abstract Zirconium pillared clay (PILC) was prepared using montmorillonite as the base clay. Adsorption of tannic acid (tannin) was studied by a batch equilibrium technique, as a function of adsorbate concentration, temperature, pH, agitation speed, particle size of the adsorbent and ionic strength. The process of uptake is governed by diffusion controlled first-order reversible rate kinetics. The higher uptake for the pH range 4.0,6.0 was attributed to external hydrogen bonding between phenolic-OH groups of tannin molecules and the hydrogen bonding sites on the clay. The removal of tannin by adsorption was found to be >99.0% depending on the initial concentration in the pH range of 4.0,6.0. The process involves both film and pore diffusion to different extents. The effects of solute concentration, temperature, agitation speed and particle size on the diffusion rate were investigated. Tannin uptake was found to increase with ionic strength due to the compression of diffuse double layers. The applicability of Langmuir and Freundlich isotherm models has been tested. The maximum adsorption capacity of PILC was found to be 45.8,µmol,g,1 of clay and the affinity constant is 2.9,×,10,2,dm3,µmol,1 at 30,°C. Thermodynamic parameters such as ,G,°,,H,° and ,S,° were calculated to predict the nature of adsorption. The isosteric enthalpies of adsorption were also determined and found to decrease with increasing surface coverage. Regeneration with hot water (60,°C) has been investigated for several cycles with a view to recovering the adsorbed tannin and also restoring the sorbent to its original state. Copyright © 2001 Society of Chemical Industry [source] Performance improvement of a combined double-way thermochemical sorption refrigeration cycle with reheating processAICHE JOURNAL, Issue 2 2010Tingxian Li Abstract A reheating process is proposed aimed at improving the system performance of a combined double-way thermochemical sorption thermodynamic cycle based on adsorption and resorption refrigeration. The reheating process causes an increase in the driving equilibrium temperature difference, which promotes the reaction rate and thus improves the global conversion of sorbent. Experimental results showed that the proposed reheating process is an effective technique for improving the performance of the combined double-way cycle. The improvement in the COP ranged between 12 and 48% in the different cycle conditions, when compared with the combined double-way cycle without reheating. The low pseudo-evaporation temperature and high heat sink temperature can further improve the system performance. The COP obtained with the combined double-way cycle without reheating was 0.57, when the heat sink, evaporation, and pseudo-evaporation temperatures were 25, 10, and 10°C, respectively. However, at the same cycle conditions, the COP increased to 0.64 when the proposed reheating process was introduced in the combined double-way sorption cycle. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Application of the random pore model to the carbonation cyclic reactionAICHE JOURNAL, Issue 5 2009Gemma Grasa Abstract Calcium oxide has been proved to be a suitable sorbent for high temperature CO2 capture processes based on the cyclic carbonation-calcination reaction. It is important to have reaction rate models that are able to describe the behavior of CaO particles with respect to the carbonation reaction. Fresh calcined lime is known to be a reactive solid toward carbonation, but the average sorbent particle in a CaO-based CO2 capture system experiences many carbonation-calcination cycles and the reactivity changes with the number of cycles. This study applies the random pore model (RPM) to estimate the intrinsic rate parameters for the carbonation reaction and develops a simple model to calculate particle conversion with time as a function of the number of cycles, partial pressure of CO2, and temperature. This version of the RPM model integrates knowledge obtained in earlier works on intrinsic carbonation rates, critical product layer thickness, and pore structure evolution in highly cycled particles. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Steam reactivation of a spent sorbent for enhanced SO2 capture in FBCAICHE JOURNAL, Issue 12 2006Fabio Montagnaro Abstract The regeneration by steam hydration of the sulfur capture ability of spent sorbent particles from Fluidized Bed Combustion (FBC) is addressed. The process is characterized in terms of effectiveness of sorbent reactivation, hydration degree, particle sulfation pattern, development of accessible porosity, and extent of particle attrition and fragmentation. Steam reactivation experiments were carried out in a lab-scale atmospheric FBC at 250°C for 10, 30, and 180 min with 0.05 MPa steam partial pressure. The effectiveness of sorbent reactivation was assessed by reinjecting the reactivated material into the FB reactor operated at 850°C under simulated desulfurization conditions and following the degree of calcium conversion and the attrition rate along with resulfation. The experimental results indicated that steam reactivation is effective in renewing the SO2 uptake ability of the exhausted sorbent particles. The regeneration mechanism based on the swelling upon hydration of the unreacted core, the generation of fissures and cracks, and the consequent development of accessible porosity is confirmed for the limestone under scrutiny. In addition to this, a remarkable result was that steam hydration induces, for the sorbent under investigation, a pronounced sulfur redistribution throughout the particle cross-section, which provides another pathway to the enhancement of the sulfur capture ability of the reactivated sorbent. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Solid phase peptide synthesis on epoxy-bearing methacrylate monolithsJOURNAL OF PEPTIDE SCIENCE, Issue 12 2004E. Vlakh Abstract Monoliths based on a copolymer of glycidyl methacrylate (GMA) and ethylene dimethacrylate (EDMA) can be used directly as sorbents for affinity chromatography after solid phase peptide synthesis. The quality of the synthesized products, the amount of grown peptides on a support and the reproducibility of the process must be considered. A determination of the quantity of the introducing ,-Ala (and, consequently, the total amount of synthesized peptide) was carried out. Three peptides complementary to recombinant tissue plasminogen activator (t-PA) have been synthesized using Fmoc-chemistry on GMA-EDMA disks. The peptidyl ligands were analysed by amino acid analysis, ES-MS and HPLC methods. The affinity binding parameters were obtained from frontal elution data. The results were compared with those established for GMA-EDMA affinity sorbents formed by the immobilization of the same but separately synthesized and purified ligands. The immobilization on GMA-EDMA disks was realized using a one-step reaction between the amino groups of the synthetic ligand and the original epoxy groups of monolithic material. The affinity constants found for two kinds of sorbent did not vary significantly. Finally, the directly obtained affinity sorbents were tested for t-PA separation from a cellular supernatant. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd. [source] Selectivity effects on series reactions by reactant storage and PSA operationAICHE JOURNAL, Issue 11 2000Adriaan J. Kodde This work evaluates adsorptive reactors used to improve the operation of a sequential reaction scheme, , for the total removal of A from a stream with an excess of B. In the adsorptive-reactor concept, the reactor is filled with a physical mixture of catalyst and an adsorbent, the latter being thermodynamically selective toward primary reactant A. In this case, the sorbent is periodically regenerated using the principles of pressure swing adsorption and purged with secondary reactant D. This concept is restricted to low temperatures to have sufficient adsorption capacity. Improved reaction selectivity arises from the accumulation of A in the unit. The reaction of A maximizes the driving force for regeneration and thus accelerates the regeneration half-cycle. The adsorptive reactor is compared to a conventional plug-flow reactor (PFR) and to PSA and PFR units in series. Reaction selectivity improved and pure B recovered over these alternative reactors under realistic conditions. The volume-based productivity is lower than that of PFR, but higher than that of PSA. The purge-gas flow rate can be manipulated to balance the sorption flux and reaction rate, thereby maximizing the conversion of A. The influence of differences in sorption kinetics is discussed and the required sorbent characteristics are identified. [source] Preparation and characterization of highly polar polymeric sorbents from styrene,divinylbenzene and vinylpyridine,divinylbenzene for the solid-phase extraction of polar organic pollutantsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2003Núria Fontanals Abstract This article explores the synthesis of styrene,divinylbenzene resins with different surface areas and the influence of these surface areas on their performance in the solid-phase extraction of polar compounds from water samples. As expected, increasing the surface areas increases the retention capability of polar compounds. To improve the retention properties, we have used 4-vinylpyridine instead of styrene in the polymerization and evaluated the influence of the sorbent polarity and surface area on the retention properties. We have found that a compromise is required between the percentage of 4-vinylpyridine, which increases the polarity of the sorbent, and the percentage of divinylbenzene, which increases the surface area. In the solid-phase extraction of polar compounds, the results are best for a polymer containing 2.14% N and having a surface area of 710 m2/g. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1927,1933, 2003 [source] Magnesium oxide microspheres as a novel solid-phase extraction sorbent for the determination of benzo[a]pyrene in environmental water samplesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 12 2010Jing Jin Abstract Magnesium oxide microspheres were developed as a novel SPE sorbent for the determination of benzo[a]pyrene (BaP), one of the most potent carcinogenic agents, in environmental water samples. The parameters controlling the extraction efficiency, such as elution volume, flow rate, pH values, and breakthrough volume, were investigated in detail. Considering the facile preparation and satisfying recovery, a corresponding analytical method has been developed to determine the concentration of BaP in real tap water, river water, and seawater. The recoveries for the spiked BaP were excellent (94,101%). [source] Membrane protected conductive polymer as micro-SPE device for the determination of triazine herbicides in aquatic mediaJOURNAL OF SEPARATION SCIENCE, JSS, Issue 8 2010Habib Bagheri Abstract A micro-SPE technique was developed by fabricating a rather small package including a polypropylene membrane shield containing the appropriate sorbent. The package was used for the extraction of some triazine herbicides from aqueous samples. Solvent desorption was subsequently performed in a microvial and an aliquot of extractant was injected into GC-MS. Various sorbents including aniline- ortho -phenylene diamine copolymer, newly synthesized, polypyrrole, multiwall carbon nanotube, C18 and charcoal were examined as extracting media. Among them, conductive polymers exhibited better performance. Influential parameters including extraction and desorption time, desorption solvent and the ionic strength were optimized. The developed method proved to be rather convenient and offers sufficient sensitivity and good reproducibility. The detection limits of the method under optimized conditions were in the range of 0.01,0.04,ng/mL. The RSDs at a concentration level of 0.1,ng/mL were obtained between 4.5 and 9.3% (n=5). The calibration curves of analytes showed linearity in the range of 0.05,10,ng/mL. The developed method was successfully applied to the extraction of selected triazines from real water samples. The whole procedure showed to be conveniently applicable and quite easy to manipulate. [source] Selective preconcentration of volatile mercaptans in small SPE cartridges: Quantitative determination of trace odor-active polyfunctional mercaptans in wineJOURNAL OF SEPARATION SCIENCE, JSS, Issue 21 2009Laura Mateo-Vivaracho Abstract A general procedure for the selective preconcentration and purification of mercaptans has been developed. Mercaptans are strongly retained in a small (20,mg) SPE cartridge containing p- hydroxymercurybenzoate. The cartridge can then be rinsed with relatively high volumes of polar (water/methanol mixtures) and non-polar (pentane or pentane/ether mixtures) rinsing solutions to remove nearly all volatile compounds lacking a thiol functionality. Retained analytes are further eluted with a small volume of an organic solvent containing 1,4-dithioerythritol. Some basic aspects of the strategy, such as the retention of p -hydroxymercurybenzoate in the sorbent and its stability versus different rinsing and eluting systems, have been studied in depth. Light sulfur compounds contained in water or wine, including mercaptans such as methanethiol or thioethers, such as diethyl sulfide, can be quantitatively extracted, although only mercaptans can be quantitatively recovered if a polar rinsing is applied. The strategy has been applied to the GC-MS quantitative determination of some trace polyfunctional mercaptans that are key aromas in wine, such as 2-methyl-3-furanthiol, 2-furfurylthiol, 4-mercapto-4-methyl-2-pentanone, 3-mercaptohexyl acetate or 3-mercaptohexanol. The developed method reaches detection limits in the ng/L range and has a satisfactory analytical behavior, being quite simple and fast. [source] Determination of banned Sudan dyes in food samples by molecularly imprinted solid phase extraction-high performance liquid chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 19 2009Claudio Baggiani Abstract A method for molecularly imprinted SPE of banned Sudan azo-dyes from food samples was investigated. The molecularly imprinted polymer was obtained by suspension polymerization using 1-(4-chlorophenyl)azonaphthalen-2-ol as the mimic template. The molecular recognition properties of imprinted beads were evaluated for use as a SPE sorbent, in order to develop a selective extraction protocol for the Sudan class of dyes. The optimized extraction protocol resulted in a reliable molecularly imprinted SPE (MISPE) method suitable for HPLC analysis. It was selective for the main analyte, Sudan I, and the related azo-dyes Sudan II, III, IV, Sudan Red B, and Sudan Red 7B, while the permitted azo-dyes Allura Red AC, Neococcin, and Sunset Yellow FCF were not extracted. The method was tested for Sudan I, II, III, and IV in five different food samples (hot chilli pepper, hot chilli tomato sauce, sausage, tomato sauce, and hard boiled egg yolk) at three concentration levels (15, 100, and 300 ,g/g). It demonstrated itself to be insensitive to the presence of different complex matrices, precise, accurate, and with good recovery rates (85,101%). The LOD and LOQ were satisfactory for most analytical determinations. [source] | ||||||||||||||||||||||||||||||||||