Improved performance of a chitosan-based adsorbent for the sequestration of some transition metals

Polyethyleneimine (PEI) was chemically introduced onto chitosan by its reac tion with epoxide groups of grafted poly(glycidyl methacrylate) (poly(GMA)) chains for enhanced metal chelating properties and improved physical stabi lity in acidic conditions. Graft polymerization of poly(GMA) onto chitosan was initiated by Ce(IV) ammonium nitrate (CAN). Infrared spectroscopy revea led the presence of significant epoxide groups to confirm the success of bo th grafting and amination stages. Batch adsorption experiments showed the h igher affinity of the modified chitosan resin for Cu2+, Zn2+ and Pb2+. The capacity enhancement was even more pronounced in the case of Zn2+ and Pb2+, which exhibits more complicated three dimensional coordination requirement s. Optimum metal adsorption occurs at above pH 4. Regeneration of the resin with sulphuric acid-ammonium sulphate was also found to be feasible.