The preparation and anion exchange properties of 3-n-propyl(4-methylpyridinium) silsesquioxane chloride polymer are described. This new polymer was prepared by the sol-gel processing method and is designated as SiPic(+)Cl(-). It is insoluble in water and showed an anion exchange capacity of 1.46 x 10(-3) molg(-1). The adsorption isotherms of ZnCl2, CdCl2 and HgCl2 were determined from aqueous solutions and the adsorption equilibria simulations fit the model of fixed bidentate centers with the absence of lateral interactions and energetic heterogeneity between them. The metal ions diffuse into the solid solution interface and are dominantly present as MCl42- species for Zn(II), MCl42- and MCl3- species for Cd(II) and MCl3- species for Hg(II). (c) 2006 Elsevier Inc. All rights reserved.