Adsorption of metal halides from ethanol solutions by a 3-n-propylpyridiniumsilsesquioxane chloride-coated silica gel surface

3-n-Propylpyridiniumsilsesquioxane chloride polymer, abbreviated as SiPy+Cl−, was used to coat a porous silica gel, SiO2, surface to form the chemically modified solid SiO2/SiPy+Cl−. The resulting polymer film was well adhered to the surface and presented an ion exchange capacity of 0.74 mmolg−1. Metal halides, MClz [M = Fe(III), Cu(II), and Zn(II)], were adsorbed by the modified solid from ethanol solutions as neutral species by forming the surface anionic complexes described by the equation: mSiO2/SiPy+Cl−+ MClz⇄ (SiO2/SiPy+)m[MClz+m]m−, where the [MClz+m]m− species adsorbed on the surface are FeCl4−, ZnCl42−, and CuCl42−. Accurate estimates of the specific sorption capacities and the heterogeneous stability constants of the immobilized metal complexes were determined with the aid of computational procedures.