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

Polyethyleneimine (PEI) was chemically introduced onto chitosan by its reaction with epoxide groups of grafted poly(glycidyl methacrylate) (poly(GMA)) chains for enhanced metal chelating properties and improved physical stability in acidic conditions. Graft polymerization of poly(GMA) onto chitosan was initiated by Ce(IV) ammonium nitrate (CAN). Infrared spectroscopy revealed the presence of significant epoxide groups to confirm the success of both grafting and amination stages. Batch adsorption experiments showed the higher 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 requirements. Optimum metal adsorption occurs at above pH4. Regeneration of the resin with sulphuric acid-ammonium sulphate was also found to be feasible.