Azacrown ether chitosan (CTSC) was synthesized by the reaction of chitosan with N-allyl benzo 15-crown-5 crown ether. Azacrown ether crosslinked chitosan (CCTSC) was prepared by the crosslinked reaction of CTSC and epichlorodydrin. Their structures were confirmed by infrared spectral analysis and X-ray diffraction analysis. The adsorption properties of CTSC and CCTSC for metal ions were also investigated. The experimental results showed that the two chitosan derivatives not only had a good capacity to adsorb Pd2+ and Ag+ but also was highly selective for Pd2+ and Ag+ in the coexistence system containing other metal ions. At 20 degrees C +/- 1 degrees C and pH = 4, the adsorption capacity of CTSC and CCTSC for Pd2+ was 186.1 and 173.1 mg/g, respectively; and for Ag+ was 90.2 and 56.5 mg/g, respectively. The selectivity coefficients were K-Ag(+)/N-1(21) = 6.99, KAg+/(Cu2+) = infinity, KPd2+/Pb2+ = 35.38, KPd2+/Cu2+ = infinity for CTSC and KAg+/Ni2+ = 10.66, KAg+/Cu+ = infinity, KPd2+/Pb2+ = 85.45, KPd2+/Cu2+ = infinity for CCTSC. (c) 2006 Wiley Periodicals, Inc.