In this paper the adsorption thermodynamics properties of new type chitosan crosslinked by aldehyde and epichlorohydrin (AECTS) for Ni(II) and the influence of Ni(II) on the AECTS structure and performance were investigated. The structure of adsorption products was characterized by Fourier transform IR, WAXD, TGA and DSC. The influence of different medium on adsorption was also studied. The results showed that AECTS adsorbed Ni(II) mainly by complexation, the experimental data fit well into the Langmuir adsorption isotherm and the process obeyed the formation of monolayer adsorption. Compared with chitosan, the main reasons that AECTS may adsorb more Ni(II) are its crystallinity decrease and porosity increase which make the adsorption site adsorb Ni(II) more easily. Compared with AECTS, the structure and properties of AECTS-Ni(II) have been markedly changed. Its crystallinity and generally thermal stability decreased. The metal ion had evident catalyzing function to the decomposition of AECTS main chains but represented marked fire-retardant function to the residue decomposition of AECTS in air at about 500 ℃. The effect decreased in the folloning of media on adsorption process HCl＞CdCl₂＞MgCl₂＞NaCl. HCl and CdCl₂ made the adsorption quantity of AECTS acutely decrease, while MgCl₂ made the adsorption quantity of AECTS slightly increase and NaCl almost had no influence. Their effect mechanism was analyzed and discussed.

Key words: crosslinked chitosan, Ni(II), complexation, adsorption mechanism, medium