A novel polyaminated and cross-linked chitosan bead templated by Ni^2＋ ions [P-C-CTS(Ni)] was prepared by introducing epichlorohydrin and polyethylene polyamine to enhance rigidity and increase the adsorption sites. The P-C-CTS(Ni) with a higher adsorption capacity was obtained. The adsorption properties of P-C-CTS(Ni) to Ni(II) were studied. The structures of semifinished products were determined by IR and XPS, which validated the synthesis of P-C-CTS(Ni) in desirable processes. The relationships between pH and adsorption capacities for nickel in the presence of citrate (Cit) ligands with nickel/citrate molar ratio 1∶1 (c_Ni＝c_Cit＝0.852 mmol•L^－1) were investigated, showing that the adsorption capacities of P-C-CTS(Ni) to Ni(II) which depended on pH in the presence of citrate ligands were distinctly different from those in the absence of the ligands. With the distributions of nickel species and citrate species being in function of pH in the corresponding conditions, the adsorption mechanisms of P-C-CTS(Ni) including both chelation and electrostatic attraction were discussed.

Key words: chitosan adsorbent; templated by Ni^2＋; polyamination, adsorption mechanism