Synthesis of γ-cyclodextrin/chitosan composites for the efficient removal of Cd(II) from aqueous solution

The synthesis of chitosan-graft-gamma-cyclodextrin (Ch-g-gamma-CD) using persulfate/ascorbic acid redox system was done and characterized by FTIR, XRD, TGA and SEM/EDX. The optimum yield of the copolymer was obtained using 16 x 10(-3) M y-cyclodextrins (gamma-CD), 2.8 x 10(-2) M ascorbic acid (AA), 1.8 x 10(-2) M K2S2O8 and 0.1 g chitosan in 25 mL of 2% aqueous formic acid at 45 +/- 0.2 degrees C. The highest percent grafting samples were evaluated for cadmium metal ion (Cd(II)) removal from the aqueous solutions where the sorption capacities were found proportional to the grafting extent. The sorption was pH and concentration dependent where, pH = 8.5 was found to be the optimum value. The adsorption data were modeled using Langmuir and Freundlich isotherms. The equilibrium data followed the Langmuir isotherm model with maximum sorption capacity of 833.33 mg/g. The influence of electrolytes, sodium chloride (NaCl) and sodium sulphate (Na2SO4) on Cd(II) uptake was also studied. Desorption of the cadmium loaded Ch-g-gamma-CD was accomplished with 0.01 N H2SO4. The adsorbent exhibited high reusability and could be successfully recycled for nine cycles where in the ninth cycle 27% adsorption was feasible. (C) 2011 Elsevier B.V. All rights reserved.