Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Polymers Si3Py(+)Cl(-) ( A) and Si4Py(+)Cl(-) (B), 3-n-propyl(3-methylpyridinium) silsesquioxane and 3-n-propyl(4-methylpyridinium) silsesquioxane chlorides, respectively, were prepared by the sol-gel processing method. The ion exchange capacities (mmol g(-1)) were 0.90 and 0.81 for ( A) and ( B) respectively. Considering the reaction nSiPy(+)Cl((s))(-) + M((sln))(2+) + 2Cl((sln))(-) reversible arrow (SiPy(+))(n)MCl(2+n)((s))(n-), the values of the stepwise equilibrium constants obtained were: (A) Cu(II): logK((2))(1)=4.14(0.03), logK((2))(2)= 2.91(0.04); Zn(II), logK((2))(1)= 3.3(0.3), logK((2))(2)= 4.9(0.3); (B) Cu(II): logK((2))(1)= 3.82(0.03), logK((2))(2)= 3.00(0.04); Zn(II), logK((2))(1)= 3.93(0.03), logK((2))(2)= 3.55(0.08), being K((2))(1) and K((2))(2) the equilibrium constants for adsorption of the species MCl(4)(2-) and MCl(3)(-), respectively. For adsorption of Zn(II) on Si3Py(+)Cl(-), K((2))(2) > K((2))(1), indicating positive cooperativity, i.e., the adsorption of MCl42- enhances the adsorption of MCl(3)(-) species on the adsorbent surface. For the other cations, K((2))(1) > K((2))(2), indicating that adsorption of MCl(4)(2-) depresses the adsorption of MCl(3)(-) species, indicating negative cooperativity.204744752Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [00-11103-5]