The chemically crosslinked metal-complexed chitosans were synthesized by using the ion-imprinting method from a chitosan with four metals (Cu(II), Zn(II), Ni(II) and Pb(II)) as templates and glutaraldehyde as a crosslinker. The influences of adsorption conditions, including molar ratio, of crosslinker/chitosan and pH changes, were studied. They were used to investigate for comparative adsorptions of Cu(II), Zn(II), Ni(II) and Pb(II) ions in an aqueous medium. They were demonstrated the comparative adsorptions of Cu(II), Zn(II), Ni(II) and Pb(II) ions in the orders of the adsorbed amounts with templates: Cu(II)similar to Pb(lI)>Zn(II)similar to Ni(II), Zn(II)>Cu(II)similar to Pb(II)>Ni(II), Ni(II)>Pb(II)>Zn(II)>Cu(II) and Pb(II) similar to Cu(II) > Zn(II) > Ni(II), respectively. In addition, the dynamical study showed to be well followed the second-order kinetic equation in the adsorption process. At the same time, the equilibrium adsorption data were fitted in three adsorption isotherm models, namely, Langmuir, Freundlich, and Dubinin-Radushkevich to show very good fits in the Langmuir isotherm equation for the monolayer adsorption process. The most important aspect of the chemically crosslinked metal-complexed chitorsans with glutaraldehyde demonstrated to afford a higher adsorption capacity, and a more efficient adsorption toward metals in an aqueous medium. (C) 2008 Elsevier B.V. All rights reserved.