Improved metal affinity of chelating adsorbents through graft polymerization

Modification of cellulose for heavy metal adsorption was conducted by the graft polymerization of glycidyl methacrylate utilizing ceric ammonium nitrate initiator, followed by the reaction with polyethyleneimine to introduce nitrogenous ligands. Infrared (IR) spectra of the reaction intermediates and products qualitatively revealed the presence of significant functional groups. Low amine to epoxide ratio (2 amines/epoxide) from elemental analysis of the products confirmed the occurrence of crosslinking between PEI and poly(GMA) side chain. Comparisons between metal adsorption isotherms of poly(CGMAPEI) adsorbent and cellulose-PEI, a previously synthesized adsorbent having extensive PEI crosslinking with the matrix, showed a higher metal affinity in the former. Based on these properties, an adsorbent structure model where ligands acquire an improved mobility was suggested. Optimization experiments further revealed that the metal affinity of the this adsorbent is affected by the amount of initiator during polymerization.