We first synthesized N-benzylidene chitosan (CTB) by the reaction of benzaldehyde with chitosan (CTS). Chitosan-dibenzo-18-crown-6 crown ether bearing Schiff-base group (CTBD) and chitosan-dibenzo-18-crown-6 crown ether (CTSD) were prepared by the reaction of 4,4'-dibromodibenzo-18-crown-6 crown ether with CTB and CTS, respectively. Their structures were confirmed by Fourier transform infrared spectral analysis and X-ray powder diffraction analysis. These novel crown ether crosslinked CTSs have space net structures with embedded crown ethers and contain the double structures and properties of CTS and crown ethers. They have stronger complexation with and better selectivity for metal ions than corresponding crown ethers and CTS. Moreover, these novel CTS derivatives can be used to separate and preconcentrate heavy or precious metal ions in aqueous environments. From this practical viewpoint, we studied the adsorption and selectivity properties of CTB, CTBD, and CTSD for Ag-1, Cu2+, Pb2+, and Ni2+. The experimental results showed that CTBD had better adsorption properties and higher selectivity for metal ions than CTSD. For aqueous systems containing Pb2+ -Ni2+ and Pb2+ -Cu2+, the selectivity coefficients of CTSD and CTBD were KPb2+/Ni2+ = 24.4 and KPb2+/Cu2+ = 41.4 and KPb2-/Ni2+ = 35.5 and KPb2+/Cu2+ = 55.3, respectively. (C) 2002 John Wiley Sons, Inc.