Synthesis of Porous Cross-Linked Grafted Chitosan and Its Application for Metal Ion Adsorption

A water-soluble intermediate bi-functional compound with thioureido and carboxyl groups was prepared by reacting chitosan with ammonium thiocyanate and chloroacetic acid. The intermediate compound was then cross-linked by epichlorohydrin to prepare a novel water-insoluble cross-linked chitosan aiming to be used as an adsorbent for heavy metal wastewater treatment. Both the intermediate compound and the cross-linked grafted chitosan (CGCTS) were characterized by using FTIR, SEM and specific surface area measurement. The analysis results indicated that the -COOH and -HN-C(S)-NH- COOH- groups have been grafted onto the chitosan molecular chain. The CGCTS displayed a porous structure with a pore size typically below 100 nm and a specific surface area of 90.6 m²/g. The synthesized porous chitosan demonstrated a good adsorption capability for Cu²⁺, Ni²⁺ and Co²⁺ ions. Regeneration study of the synthesized porous CGCTS showed no decrease in adsorption capability after three regeneration cycles.