Chemisorption of some divalent cations on silica modified through the reaction of pentane-2,4-dione with 3-propylethylenediamine silica gel

The reaction of 3-propylethylenediamine groups covalently bonded to silica gel with pentane-2,4-dione in benzene resulted in a modified surface having 11.4·10⁻⁴ mol g⁻¹ of ligand sites which adsorb the divalent cations Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ from ethanol solution with maximum adsorptions of 5.0·10⁻⁴ mol g⁻¹, 2.0·10⁻⁴ mol g⁻¹, 5.0·10⁻⁴ mol g⁻¹ and 5.9·10⁻⁴ mol g⁻¹, respectively. The adsorption isotherms are very similar in shape for all the cations and conform to the Langmuir model. The complexes formed on the surface have a molar composition or one cation to two anchored groups of Schiff bases and the geometries of the complexes are similar to those obtained in solution.