Adsorption of Phosphate and Arsenate on Polynuclear Aluminum-Oxalate Precipitate: Spectroscopic and Adsorption Investigations

Aluminum organic coprecipitates play important roles in the transport of oxyanions in soil environment. Al₁₃-Oxalate precipitate representing common aluminum organomineral components in soil environment was prepared to investigate the adsorption behavior of phosphate and arsenate on noncrystalline aluminum precipitate. Important thermodynamic parameters (ΔG, ΔH and ΔS) of adsorption reactions were evaluated using macroscopic adsorption data and equations. The low values of active energy of arsenate and phosphate adsorption reactions (Ea = 21.9KJ·moL^-1 and 10.6 KJ·moL^-1, respectively) indicate that the adsorption reaction basically is a diffusion process. The XPS studies indicate that phosphate has stronger chemical interaction with substrate than arsenate. FTIR spectroscopic studies have provide evidence for the formation of two different types of complexes in substrate.