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A cellulose-based anion exchanger (Cell-AE) bearing the sN + HR 2 Clfunctional group was prepared through graft copolymerization of glycidyl methacrylate onto cellulose (Cell) in the presence of N,N′-methylenebisacrylamide as a cross-linker using benzoyl peroxide as the initiator, followed by amination and hydrochloric acid treatment. The adsorbent was characterized by infrared spectroscopy, scanning electron microscopy, surface area analysis, thermogravimetry, and potentiometric titrations. Batch experiments were performed to evaluate the adsorption efficiency of Cell-AE toward V(V) ions in aqueous solutions. The maximum removal was observed in the pH range of 4.0-6.0. The adsorption process achieved more than 99.6% V(V) removal from an initial concentration of 25.0 mg/L. Adsorption kinetic data were described by pseudo-second-order equation. The equilibrium data fitted very well with the Langmuir model, and the maximum adsorption capacity of Cell-AE toward V(V) was found to be 197.75 mg/g at 30 °C. Over 96.0% desorption of V(V) was achieved with 0.1 M NaOH solution.

BACKGROUND: The main aim of this study is to determine the sorptive potential of a novel anion exchanger, Fe(III)‐coordinated amino‐functionalized poly(glycidylmethacrylate)‐grafted TiO2‐densified cellulose (AM‐Fe‐PGDC) for arsenic(V) removal from aqueous solutions by batch technique. RESULTS: The adsorbent was characterized using infrared spectroscopy, powder X‐ray diffraction, scanning electron microscopy, thermogravimetry and potentiometric titrations. The effective pH for removal was 6.0. The adsorption rate was influenced by initial metal ion concentration and contact time. The equilibrium was achieved within 1.5 h and follows a pseudo‐second‐order kinetic model. The adsorption capacity for As(V) calculated using the Langmuir isotherm equation was 105.47 mg g−1. The AM‐Fe‐PGDC developed was used to remove As(V) from simulated groundwater. Regeneration experiments were attempted for four cycles using 0.1 mol L−1 NaCl solution. CONCLUSION: It was found that AM‐Fe‐PGDC is very efficient for the removal of As(V) from aqueous solutions. © 2012 Society of Chemical Industry

An organophilic calcined hydrotalcite (OHTC) was prepared by treating calcined hydrotalcite (HTC) with sodium dodecylbenzene sulphonate (an anionic surfactant) to achieve a high loading of thiol functionality through the immobilization of 2-mercaptobenzimidazole (MBI) as a chelating agent. The adsorbent (MBI-OHTC) obtained was characterized using XRD, FTIR, SEM, TG/DTG, surface area analysis and potentiometric titration. The adsorption of MBI-OHTC to remove Hg(II) ions from aqueous solutions was studied as a function of pH, contact time, metal ion concentration, ionic strength and adsorbent dose. The optimum pH range for the maximum removal of Hg(II) was 6.0-8.0. The maximum value of Hg(II) adsorption was found to be 11.63 and 21.52 mg g −1 for an initial concentration of 25 and 50 mg l −1 , respectively at pH 8.0. The equilibrium conditions were achieved within 3 h under the mixing conditions employed. A reversible pseudo-first-order used to test the adsorption kinetics. The adsorption mechanism consisted of external diffusion and intraparticle diffusion and the intraparticle mass transfer diffusion was predominated after 20 min of experiment. Extent of adsorption decreased with increase of ionic strength. The experimental isotherm was analyzed with two parameters (Langmuir and Freundlich) and three parameters (Redlich-Peterson) equations. The isotherm data were best modeled by the Freundlich isotherm equation. Complete removal (≈100%) of Hg(II) from 1.0 l of chlor-alkali industry wastewater containing 9.86 mg Hg(II) ions, was possible with 3 g of the adsorbent dose at pH 8.0. About 95.0% of Hg(II) can be recovered from the spent adsorbent using 0.1 M HCl.

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The present investigation was undertaken to evaluate the effectiveness of a new adsorbent prepared from coconut coir pith (CP), a coir industry-based lignocellulosic residue in removing metal ions from aqueous solutions. The adsorbent (PGCP-COOH) having a carboxylate functional group at the chain end was prepared by grafting polyacrylamide onto CP using potassium peroxydisulphate as an initiator and in the presence of N,N 0 -methylenebisacrylamide as a crosslinking agent. The adsorbent was characterized by infrared (IR) spectroscopy, thermogravimetry (TG), X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), and potentiometric titration. The adsorbent exhibits very high adsorption potential for the removal of Pb(II), Hg(II), and Cd(II) ions from aqueous solutions. The optimum pH range for metal ion removal was found to be 6.0-8.0. The adsorption process follows a pseudo-second-order kinetic model. The adsorption capacities for Hg(II), Pb(II), and Cd(II) calculated using the Langmuir isotherm equation were 254.52, 189.49, and 63.72 mg g À1 , respectively. Adsorption isotherm experiments were also conducted for comparison with a commercial carboxylate form cation exchanger. Different industry wastewater samples were treated by the PGCP-COOH to demonstrate its efficiency in removing heavy metals from wastewater. The reusability of the PGCP-COOH was also demonstrated using 0.2M HCl.

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