Modified chitosan such as chitosan alpha-ketoglutaric acid (KCTS) and hydroxamated chitosan alpha-ketoglutaric acid (HKCTS) are successfully prepared. The resulting polymers were characterized by C-13 NMR and X-ray diffraction (XRD), respectively. A adsorption system was applied to study the adsorption of Zn(II) ion onto chitosan derivatives. The isothermal sorption kinetics of chitosan derivatives for Zn(II) ion has been investigated. The kinetics experimental data correlated well with the second-order kinetic model, indicating that the chemical sorption was the rate-limiting step. The adsorption mechanism of chitosan derivatives with Zn(II) was studied by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results indicated that the nitrogen in amino group and the oxygen in carboxyl group of KCTS were coordination atoms. N atom of amino group, O atom of hydroxamic acid and O atom of carbonyl group in HKCTS coordinated with Zn(OO). (C) 2007 Elsevier B.V. All rights reserved.