HCl Solution (hcl + solution)

Distribution by Scientific Domains

Kinds of HCl Solution

  • m hcl solution

  • Selected Abstracts

    Determination of the Optimum Conditions for Zinc Extraction from Ore Containing Sphalerite by HCL Solutions

    Osman Nuri Ata
    Abstract The Taguchi method has been used to determine optimum conditions for the zinc and iron extraction from ore containing sphalerite by HCI solutions. After determining the important parameters in extraction efficiency, an experimental series with two steps was carried out. The optimum conditions for the first series of experiments were found to be reaction temperature 90°C, solid-to-liquid ratio 0.091 g/mL, acid concentration 25 mass%, particle size -100+200 mesh, stirring speed 300 rpm and reaction time 120 min. Under these conditions, zinc extraction efficiency from ore was approximately 60%. The optimum conditions for the second series of experiments were found to be reaction temperature 90°C, acid concentration 32.5 mass%, solid-to-liquid ratio 0.1 g/mL, and reaction time 180 min. Under these conditions, zinc extraction efficiency from the ore was approximately 100%. Alternative working conditions reducing the total cost were also determined. On a utilisé la méthode Taguchi pour déterminer les conditions optimales d'extraction du zinc et du fer d'un minerai contenant de la sphalérite par des solutions de HCl. Après avoir déterminé les paramètres importants dans l'efficacité de l'extraction, des séries expérimentales en deux étapes ont été réalisées. Les conditions optimales pour les premières séries d'expériences sont une température de réaction de 90°C, un rapport solides-liquide de 0,091 g/mL, une concentration acide de 25% en matière, une taille de particules de -100+200 mailles, une vitesse de mélange de 300 tr/min et un temps de réaction de 120 min. Dans ces conditions, l'efficacité de l'extraction du zinc du minerai est d'environ 60%. Les conditions optimales pour la deuxième série d'expériences sont une température de réaction de 90°C, une concentration acide de 32,5% en matière, un rapport solides-liquide de 0,1 g/mL et un temps de réaction de 180 min. Dans ces conditions, l'efficacité de l'extraction du zinc du minerai est d'environ 100%. En outre, on a déterminé d'autres conditions de travail permettant de réduire le coût total. [source]

    Development of a new hybrid technique for rapid speciation analysis by directly interfacing a microfluidic chip-based capillary electrophoresis system to atomic fluorescence spectrometry

    ELECTROPHORESIS, Issue 11 2005
    Feng Li
    Abstract This paper represents the first study on direct interfacing of microfluidic chip-based capillary electrophoresis (chip-CE) to a sensitive and selective detector, atomic fluorescence spectrometry (AFS) for rapid speciation analysis. A volatile species generation technique was employed to convert the analytes from the chip-CE effluent into their respective volatile species. To facilitate the chip-CE effluent delivery and to provide the necessary medium for subsequent volatile species generation, diluted HCl solution was introduced on the chip as the makeup solution. The chip-CE-AFS interface was constructed on the basis of a concentric "tube-in-tube" design for introducing a KBH4 solution around the chip effluent as sheath flow and reductant for volatile species generation as well. The generated volatile species resulting from the reaction of the chip-CE effluent and the sheath flow were separated from the reaction mixture in a gas-liquid separator and swept into the AFS atomizer by an argon flow for AFS determination. Inorganic mercury (Hg(II)) and methylmercury (MeHg(I)) were chosen as the targets to demonstrate the performance of the present technique. Both mercury species were separated as their cysteine complexes within 64 s. The precision (relative standard deviation, RSD, n = 5) of migration time, peak area, and peak height for 2 mg·L,1 Hg(II) and 4 mg·L,1 MeHg(I) (as Hg) ranged from 0.7 to 0.9%, 2.1 to 2.9%, and 1.5 to 1.8%, respectively. The detection limit was 53 and 161 µg·L,1 (as Hg) for Hg(II) and MeHg(I), respectively. The recoveries of the spikes of mercury species in four locally collected water samples ranged from 92 to 108%. [source]

    Comparison of the Heavy Metal Biosorption Capacity of Active, Heat-Inactivated and NaOH-Treated Phanerochaete chrysosporium Biosorbents

    E. Güri
    Abstract Three different kinds of Phanerochaete chrysosporium (NaOH-treated, heat-inactivated and active) biosorbent were used for the removal of Cd(II) and Hg(II) ions from aquatic systems. The biosorption of Cd(II) and Hg(II) ions on three different forms of Phanerochaete chrysosporium was studied in aqueous solutions in the concentration range of 50,700 mg/L. Maximum biosorption capacities of NaOH-treated, heat-inactivated and active Phanerochaete chrysosporium biomass were found to be 148.37,mg/g, 78.68,mg/g and 68.56,mg/g for Cd(II) as well as 224.67,mg/g, 122.37,mg/g and 88.26,mg/g for Hg(II), respectively. For Cd(II) and Hg(II) ions, the order of affinity of the biosorbents was arranged as NaOH-treated,> heat-inactivated,>,active. The order of the amount of metal ions adsorbed was established as Hg(II),>,Cd(II) on a weight basis, and as Cd(II),>,Hg(II) on a molar basis. Biosorption equilibriums were established in about 60,min. The effect of the pH was also investigated, and maximum rates of biosorption of metal ions on the three different forms of Phanerochaete chrysosporium were observed at pH,6.0. The reusability experiments and synthetic wastewater studies were carried out with the most effective form, i.e., the NaOH-treated Phanerochaete chrysosporium biomass. It was observed that the biosorbent could be regenerated using 10,mM HCl solution, with a recovery of up to 98%, and it could be reused in five biosorption-desorption cycles without any considerable loss in biosorption capacity. The alkali-treated Phanerochaete chrysosporium removed 73% of Cd(II) and 81% of Hg(II) ions from synthetic wastewater. [source]

    Large-Scale Synthesis, Annealing, Purification, and Magnetic Properties of Crystalline Helical Carbon Nanotubes with Symmetrical Structures,

    J. Tang
    Abstract Crystalline helical carbon nanotubes (HCNTs) are synthesized as the main products in the pyrolysis of acetylene at 450,°C over Fe nanoparticles generated by means of a combined sol,gel/reduction method. Transmission electron microscopy (TEM) images reveal that there are two HCNTs attached to each Fe3C nanoparticle, and that the two HCNTs are mirror images of each other. Annealing in Ar at 750,°C and purification by immersion in hot (90,°C) HCl solution do not significantly change the structure of the HCNTs, despite the partial removal of Fe nanoparticles by the latter treatment. The magnetic properties of the as-prepared, annealed, and purified HCNTs have been systematically examined. The annealed sample shows relatively high magnetization due to the ferromagnetic ,-Fe nanoparticles encapsulated in the HCNT nodes. In the case of HCl treatment, relatively pure HCNTs are obtained by the removal of ferromagnetic nanoparticles from the double-HCNT nodes. The effects of the amount of catalyst used in the synthesis process on the morphology and yield of the carbon products have also been investigated. [source]

    Facile and Selective Synthesis of 4-Methyl- and 4-Phenylthiosemicarbazide (=N -Methyl- and N -Phenylhydrazinecarbothioamide) Derivatives of Benzil (=1,2-Diphenylethane-1,2-dione)

    Abstract A selective synthesis of 4-methylthiosemicarbazide (=N -methylhydrazinecarbothioamide; 4a) derivatives by reaction with benzil (=1,2-diphenylethane-1,2-dione; 3) is described. The reaction conditions determined the condensation product formed. The most important factor was the acid used: in the presence of conc. HCl solution, the open-chain 2,:,1 compound 1a was exclusively obtained, whereas in the presence of 2M HCl, the cyclic 1,:,1 condensation product 2a was formed. The alcohol used, the presence of H2O, and the time of heating were additional crucial factors. The new cyclic compound 2a with a MeO group was exclusively formed when working under high-dilution conditions. The reaction with the 4-phenyl derivative 4b gave new cyclic compounds as the major products under all conditions used (Scheme). [source]

    Palladium and platinum sorption on a thiocarbamoyl-derivative of chitosan

    A. Butewicz
    Abstract Immobilizing thiourea onto chitosan allowed using the polymer for the recovery of platinum groups metals (PGMs) in acidic solutions (up to 1,2M HCl concentrations). At low HCl concentration protonated amine groups may sorb chloroanionic metal species (electrostatic attraction mechanism); however, most of sorption proceeds through chelation on sulfur containing groups (less sensitive to acidic conditions). The bi-site Langmuir equation was used for fitting sorption isotherms. The sorption of PGMs was weakly affected by the composition of the solution (presence of high concentration of anions and base metals). Maximum sorption capacities for Pd(II) and Pt(IV) ranged between 274 and 330 mg g,1 in 0.25M HCl solutions and decreased to 150,198 mg g,1 in 2M HCl solutions: Pd(II) sorption was systematically higher than Pt(IV) sorption. The pseudo-second rate equation was used for modeling the uptake kinetics. Agitation speed hardly affected uptake kinetics indicating that external diffusion resistance is not the rate controlling step. Desorption yield higher than 85% were obtained using thiourea in 0.1M HCl solution. The adsorbents could be reused for at least three cycles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Novel nanoporous membranes from regenerated bacterial cellulose

    Muenduen Phisalaphong
    Abstract Bacterial cellulose (BC) in an NaOH/urea aqueous solution was used as a substrate material for thefabrication of a novel regenerated cellulose membrane. The dissolution of BC involved swelling BC in a 4 wt % NaOH/3 wt % urea solution followed by a freeze,thaw process. The BC solution was cast onto a Teflon plate, coagulated in a 5 wt % CaCl2 aqueous solution, and then treated with a 1 wt % HCl solution. Supercritical carbon dioxide drying was then applied to the formation of a nanoporous structure. The physical properties and morphology of the regenerated bacterial cellulose (RBC) films were characterized. The tensile strength, elongation at break, and water absorption of the RBC membranes were 4.32 MPa, 35.20%, and 49.67%, respectively. The average pore size of the RBC membrane was 1.26 nm with a 17.57 m2/g surface area. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Extraction equilibria and separation of phenylalanine and aspartic acid from water with di(2-ethylhexyl)phosphoric acid

    Su-Hsia Lin
    Abstract The distribution equilibria of single and binary L -phenylalanine and L -aspartic acid between water and a kerosene solution of di(2-ethylhexyl)phosphoric acid (D2EHPA) were studied. It was shown that the distribution ratios of phenylalanine generally increased with increasing aqueous pH (2,5) in the D2EHPA concentration range 0.1,0.5 mol dm,3, but those of aspartic acid decreased with increasing solution pH. Different reaction stoichiometries were proposed for the extraction of phenylalanine and aspartic acid under the conditions studied. The extraction equilibrium constants were obtained. Competitive extraction in binary systems was more apparent in the pH range where the cationic form of amino acids was not predominant. The present results indicated that selective separation of phenylalanine to aspartic acid was possible with this cationic extractant when they were extracted at higher pH and stripped using higher acidity of HCl solution. Copyright © 2006 Society of Chemical Industry [source]

    Fast and optimized T1 mapping technique for the noninvasive quantification of gastric secretion

    Reto Treier MSc
    Abstract Purpose To evaluate the noninvasive quantification of gastric secretion volume after administration of a labeled viscous glucose solution by fast T1 mapping. Materials and Methods T1 values of a series of labeled and diluted glucose solutions were measured in vitro to characterize the interrelationship between T1 and contrast agent concentration (CGd) as well as the dependency of relaxivity and reference T1 (T10) on the macromolecular concentration. Abdominal T1 mapping in five healthy volunteers of different body mass index was performed after filling an intragastric balloon with a labeled and diluted glucose solution. In additional ex vivo experiments, T1 values of gastric (GJ) and duodenal juice (DJ) and 0.1 N HCl solution were determined. Results A linear relationship between relaxivity and macromolecular concentration and between T10 and macromolecular concentration was found. The in vitro T1,CGd calibration curve was successfully validated in all volunteers. T1 values of GJ, DJ, and HCl (2939 msec vs. 2858 msec vs. 2760 msec) were close to the T1 of water (,3000 msec). Conclusion The presented method allows one to noninvasively quantify the spatial distribution of gastric secretory products in the human stomach and provides a valuable tool for evaluating the efficacy of drugs to stimulate/inhibit gastric secretion. J. Magn. Reson. Imaging 2008;28:96,102. © 2008 Wiley-Liss, Inc. [source]

    Synthesis of Titanate Derivatives Using Ion-Exchange Reaction

    Chul-Tae Lee
    Two types of titanate derivatives, layered hydrous titanium dioxide (H2Ti4O9·nH2O) and potassium octatitanate (K2Ti8O17) with a tunnellike structure, were synthesized using an ion-exchange reaction. Fibrous potassium tetratitanate (K2Ti4O9·nH2O) was prepared by calcination of a mixture of K2CO3 and TiO2 with a molar ratio of 2.8 at 1050°C for 3 h, followed by boiling-water treatment of the calcined products for 10 h. The material then was transformed to layered H2Ti4O9·nH2O through an exchange of K+ ions with H+ ions using HCl. K2Ti8O17 was formed by a thermal treatment of KHTi4O9·nH2O. Pure KHTi4O9·nH2O phase was effectively produced by a treatment of K2Ti4O9 with 0.005M HCl solution for 30 min. Thermal treatment at 250°,500°C for 3 h resulted in formation of only K2Ti8O17. [source]

    Inhibition of 304 stainless steel corrosion in acidic solution by Ferula gumosa (galbanum) extract

    M. Behpour
    Abstract The inhibition effect of the extract of galbanum (Ferula gummosa Boiss.) on the corrosion of 304 stainless steel in 2 M HCl solution was studied by weight loss measurements, Tafel polarization, and electrochemical impedance spectroscopy (EIS) methods. It was found that the inhibition efficiency (IE) increases as the extract concentration is increased. Tafel polarization method revealed the mixed mode inhibition of galbanum extract (GE) with predominant control of anodic reaction. The effect of temperature on the corrosion behavior of steel indicates that inhibition efficiency of the natural substance increases with the rise in temperature. At all temperatures, the adsorption of the extract components onto the steel surface was found to follow the Temkin adsorption isotherm. [source]

    Size and Aggregation of Corticosteroids Used for Epidural Injections

    PAIN MEDICINE, Issue 2 2008
    Richard Derby MD
    ABSTRACT Objective., The purpose of this study was to document particulate size in commonly used corticosteroid preparations. Inadvertent injection of particulate corticosteroids into a vertebral or foraminal artery can cause brain and spinal cord embolic infarcts and the size of the particles could be directly related to the chance that a clinically significant infarct would occur. One might assume that corticosteroids with particles significantly smaller than red blood cells might be safer. Design., The following four types of corticosteroid preparations were used in various solutions and evaluated under light microscopy: dexamethasone sodium phosphate injection, triamcinolone acetonide injectable suspension, betamethasone sodium phosphate and betamethasone acetate injectable suspension, and methylprednisolone acetate injectable suspension. Results., Dexamethasone sodium phosphate particle size was approximately 10 times smaller than red blood cells and the particles did not appear to aggregate; even mixed with 1% lidocaine HCl solution and with contrast dye, the size of the particles were unchanged. Triamcinolone acetonide and betamethasone sodium phosphate showed variable sizes; some particles were larger than red blood cells, and aggregation of particles was evident. Methylprednisolone acetate showed uniformity in size and the majority were smaller than red blood cells which were not aggregated, but the particles were densely packed. Conclusions., Compared with the particulate steroid solutions, dexamethasone sodium phosphate had particles that were significantly smaller than red blood cells, had the least tendency to aggregation, and had the lowest density. These characteristics should significantly reduce the risk of embolic infarcts or prevent them from occurring after intra-arterial injection. Until shown otherwise in clinical studies, interventionalists might consider using dexamethasone or another corticosteroid preparation with similar high solubility and negligible particle size when performing epidural injections. [source]

    Improvement of chemical stability of aqueous solution grown ZnO nanorods by aminosilane modification

    Ken-ichi Ogata
    Abstract Aiming at stable biosensing operation, aqueous-grown ZnO nanorods on sapphire substrates were examined their chemical stability against the immersion in HCl solution. Density and diameter of the ZnO nanorods were remained but their height was shortened when immersed with aminosilane modification while bare ZnO nanorods were completely disappeared after 5 min immersion, indicating that the aminosilane modification is useful to improve the chemical stability of ZnO nanolods even though the membrane by the silanezation process is not fully stable to HCl solution. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Effect of acids on in situ polyaniline film formation

    Prof MM Ayad
    Abstract The chemical oxidation of aniline with ammonium persulfate (APS) to form polyaniline (PANI) films has been studied in different aqueous acid media such as sulfuric, nitric, phosphoric and acetic acids. A comparison was made between the yields of PANI film deposition during the polymerization from these media with the corresponding one obtained previously from aqueous HCl solution. The degradation of the formed PANI films at the beginning of polymerization obtained at the higher concentrations of HCl is absent when the other acids under consideration were used. The effect of acid concentration on the yield and growth rate of the PANI film was studied. The variation in the yield and growth rate of the polymer films at different acid concentrations was explained on the basis of the electrostatic repulsion and the screening effects. Copyright © 2004 Society of Chemical Industry [source]

    Treatment of Perchlorate-Contaminated Groundwater Using Highly Selective, Regenerable Ion-Exchange Technology: A Pilot-Scale Demonstration

    REMEDIATION, Issue 2 2002
    Baohua Gu
    Treatment of perchlorate-contaminated groundwater using highly selective, regenerable ion-exchange technology has been recently demonstrated at Edwards Air Force Base, California. At an influent concentration of about 450 ,g/l ClO4,, the bifunctional anion-exchange resin bed treated approximately 40,000 empty bed volumes of groundwater before a significant breakthrough of ClO4, occurred. The presence of relatively high concentrations of chloride and sulfate in site groundwater did not appear to affect the ability of the bifunctional resin to remove ClO4,. The spent resin bed was successfully regenerated using the FeCl3,HCl regeneration technique recently developed at the Oak Ridge National Laboratory, and nearly 100 percent of sorbed ClO4, was displaced or recovered after elution with as little as about two bed volumes of the regenerant solution. In addition, a new methodology was developed to completely destroy ClO4, in the FeCl3,HCl solution so that the disposal of perchlorate-containing hazardous wastes could be eliminated. It is therefore anticipated that these treatment and regeneration technologies may offer an efficient and cost-effective means to remove ClO4, from contaminated groundwater with significantly reduced generation of waste requiring disposal. © 2002 Wiley Periodicals, Inc. [source]

    Leaching characteristics of heavy metals in fly ash from a Chinese coal-fired power plant

    Xun Gong
    Abstract China is the largest coal ash producer in the world. Hydraulic ash transport systems are used in most coal-fired power plants, which lead to serious water pollution due to leaching of trace elements. The investigation on the leaching behavior of trace contaminants from coal ash is critical to environmental risk assessments. Batch leaching tests have been performed on the fly ash collected from each field of the electrostatic precipitator (ESP) of a coal-fired power plant to study the leaching characteristics of Cd, Cr, Pb and V. Leaching solutions included HCl solution of initial pH = 4 and NaOH solution of pH = 10. The liquid/solid (L/S) ratio was about 4:1 in all leaching tests. Fourteen leaching time intervals were selected, ranging from 15 min to 7 days. The results show that under studied experimental conditions, Cr has a relatively higher leachability in the acid-leaching solution, while Pb has a higher leachability in the alkaline solution. With the increase of leaching time, the leachability of Cr in each ash sample increases obviously. Within the same time interval, Cr in the ash sample from the last field of ESP has the highest leachability. The concentration of Cd in FA3 is the highest, but the leachability of Cd for FA3 is not the highest among the three ash samples. The concentration of V in FA1 is the highest; no increased trend with leaching time has been found in the experiment. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

    Degradation patterns of tetracycline antibiotics in reverse micelles and water

    Hongkee Sah
    Abstract The objective of this study was to determine the chemical stability of tetracycline and oxytetracycline hydro-chlorides in reverse micelles. Their reverse micellar solutions were prepared using cetyltrimethylammonium bromide, water and ethyl formate. The aqueous solutions of the tetracycline antibiotics were also prepared for comparison. The reverse micellar and aqueous solutions were stored at 37C. Samples were analyzed by high performance liquid chromatography. When evaluation was performed on an aqueous tetracycline HCl solution, its half-life was estimated to be 329 h. Its chemical stability was not improved after being dissolved in the reverse micelles, and a similar half-life of 330 h was observed. However, there were noticeable differences between the two systems in terms of degradation kinetics and degradation byproducts. On the other hand, oxytetracycline HCl was unstable in water so that its half-life was only 34 h. Very interestingly, pronounced improvement in stability was attained with the reverse micellar system: upon dissolving in the reverse micelles, its half-life was increased to 2402 h. There were also marked differences in degradation patterns and mechanisms of oxytetracycline HCl in water and the reverse micelles. Our study indicates that the reverse micellar system has potential applications in solubilizing and stabilizing oxytetracycline HCl, thereby contributing to the development of its dosage forms. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    Ni2+ removal from aqueous solutions using conditioned clinoptilolites: Kinetic and isotherm studies

    Semra Çoruh
    Abstract The aim of this study is to investigate the effects of conditioning with NaCl and HCl solutions on removal of Ni2+ ions from aqueous solutions using natural clinoptilolite. Batch studies were performed to evaluate the effects of various parameters such as chemically conditioning, adsorbent amount, contact time, initial pH of the solution, mixing temperature, and initial metal ions. The results clearly showed that the conditioning improved both the exchange capacity and the removal efficiency. Langmuir, Freundlich, Temkin, and Dubinin-Kaganer-Radushkevich (DKR) isotherm models were adopted to describe the adsorption isotherms. Adsorption isotherms of Ni2+ ions could be best modeled by Langmuir equation. Three simplified models including pseudo-second-order, intraparticle diffusion and Elovich were used to test the adsorption kinetics. These results indicate a significant potential for the natural and conditioned clinoptilolites as an adsorbent/ion-exchange material for heavy metal removal. © 2008 American Institute of Chemical Engineers Environ Prog, 2009 [source]

    H2xMnxSn3-xS6 (x,=,0.11,0.25): A Novel Reusable Sorbent for Highly Specific Mercury Capture Under Extreme pH Conditions

    Manolis 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]

    Palladium and platinum sorption on a thiocarbamoyl-derivative of chitosan

    A. Butewicz
    Abstract Immobilizing thiourea onto chitosan allowed using the polymer for the recovery of platinum groups metals (PGMs) in acidic solutions (up to 1,2M HCl concentrations). At low HCl concentration protonated amine groups may sorb chloroanionic metal species (electrostatic attraction mechanism); however, most of sorption proceeds through chelation on sulfur containing groups (less sensitive to acidic conditions). The bi-site Langmuir equation was used for fitting sorption isotherms. The sorption of PGMs was weakly affected by the composition of the solution (presence of high concentration of anions and base metals). Maximum sorption capacities for Pd(II) and Pt(IV) ranged between 274 and 330 mg g,1 in 0.25M HCl solutions and decreased to 150,198 mg g,1 in 2M HCl solutions: Pd(II) sorption was systematically higher than Pt(IV) sorption. The pseudo-second rate equation was used for modeling the uptake kinetics. Agitation speed hardly affected uptake kinetics indicating that external diffusion resistance is not the rate controlling step. Desorption yield higher than 85% were obtained using thiourea in 0.1M HCl solution. The adsorbents could be reused for at least three cycles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Pyrazole functionalized organo-ceramic hybrids for noble metal separations

    AICHE JOURNAL, Issue 10 2005
    Jun S. Lee
    Abstract A series of pyrazole-functional adsorbents is synthesized by sol,gel processing technology and used to study the extraction characteristics for palladium, platinum, and gold chlorides from leaching solutions. An organosilicon compound, N-(trimethoxysilylpropyl)-pyrazole, is synthesized as the functional precursor for these adsorbents. Hydrothermal treatments for the gelled materials alter pore characteristics without chemical property changes. To study adsorptive extraction of Pd(II), Pt(IV), and Au(III) chlorides, the hydrothermally treated adsorbent is used. The experimental results show that this adsorbent has high Pd(II) uptake capacity (1.41 mmol/g), strong selectivity for Pd(II) chloride over Pt(IV) and Au(III) chlorides, and no reactivity for Cu(II) and Fe(II) in 2.0 M HCl solutions. The material also has sustainable stability over repeated metal loading and stripping in a short column. In addition to the experimental studies, the adsorption processes in batch and packed column systems are successfully modeled by using a pore diffusion model and presented. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source]

    Chromotropic acid-functionalized polyurethane foam: A new sorbent for on-line preconcentration and determination of cobalt and nickel in lettuce samples

    Valfredo Azevedo Lemos
    Abstract A chromotropic acid-functionalized polyurethane foam has been developed for use in an on-line preconcentration system for cobalt and nickel determination. The packing material was prepared by covalent coupling of chromotropic acid with the polyurethane foam through an azo group. Co and Ni ions were sorbed in the minicolumn, from which they could be eluted directly to the nebulizer-burner system of a flame atomic absorption spectrometer. Elution of cobalt and nickel from the minicolumn can be accomplished with 0.50 and 0.75 M HCl solutions, respectively. The enrichment factors obtained were 22 (Co) and 27 (Ni), for 60 s preconcentration time, and 57 (Co) and 59 (Ni), if a preconcentration time of 180 s was used. Under the optimum conditions, the proposed procedure allowed the determination of metals with detection limits of 0.43 (cobalt) and 0.52 ,g/L (nickel), respectively, on using preconcentration periods of 180 s. The accuracy of the developed procedure was evaluated by analysis of the certified reference materials NIST 1515 Apple Leaves and NIST 1570a Spinach Leaves. The method was applied to the analysis of lettuce samples. The contents of cobalt in the samples analyzed varied from 0.75 to 0.98 ,g/g. Nickel was not detected in the lettuce samples. [source]

    Spectroscopic and thermal studies of poly[(N -vinylimidazole)- co -(maleic acid)] hydrogel and its quaternized form

    Nursel Pekel
    Abstract BACKGROUND: In this study, poly[(N -vinylimidazole)- co -(maleic acid)] (poly(VIm/MA)) hydrogels were prepared by ,-irradiation of ternary mixtures of N -vinylimidazole,maleic acid,water using a 60Co ,-source. Spectroscopic and thermal analyses of these hydrogels as a function of protonation showed that the results are consistent with the existence of an H-bridged complex when the imidazole rings are partially protonated. Finally, the efficiency and binding trends of Cu2+, Co2+, Cd2+ and Pb2+ ions with both protonated and unprotonated poly(VIm/MA) hydrogels were determined. RESULTS: Gelation of 90% was reached at around 180 kGy dose at the end of irradiation. The poly(VIm/MA) hydrogels synthesized were further protonated in HCl solutions with different concentrations. Hydrogels originally showed 450% volumetric swelling; this ratio reached 1900% after protonation at pH = 5.0. Fourier transform infrared spectral changes in the +NH stretching region (3200,3600 and 1173 cm,1) and the ring mode deformation at 915 cm,1 are consistent with the formation of an H-bridged complex between the protonated and unprotonated imidazole rings upon partial protonation. Similar changes were obtained from NMR spectra of both the protonated and unprotonated forms of the hydrogels. CONCLUSION: Protonated and unprotonated hydrogels have been used in heavy metal ion adsorption studies for environmental purposes. Adsorption decreased with decreasing pH value due to the protonation of the VIm ring. The adsorption of Me2+ ions decreased in the order Cu2+ > Co2+ > Cd2+ > Pb2+, which is related to the complexation stability as well as the ionic radius of the metal ions. These results show that P(VIm/MA) hydrogels can be used efficiently to remove heavy metal ions from aqueous solutions. However, the protonated form is a bad choice for heavy metal ion adsorption due to electrostatic repulsion forces; it can nevertheless be assumed to be a good choice for anion adsorption from environmental waste water systems. Copyright © 2007 Society of Chemical Industry [source]