RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

The effect of component hydroxide and oxide interaction on Cd²⁺ and SO₄²⁻ adsorption in suspensions of Al(OH)₃/SiO₂ was modeled using two kinds of surface site distributions ncorporated in the triple-layer surface complexation model. The mixed site distribution assumes that Al(OH)₃ surface sites are uniformly distributed on the SiO₂ surface with the overall surface potential contributed by both Al(OH)₃ and SiO₂ surface ites. The patch site distribution assumes that two kinds of surfaces are present on the particle and that the double layer ssociated with one surface does not affect surface reactions on the other. Enhanced Cd²⁺ adsorption and reduced SO₄²⁻ adsorption at low Al to SiO₂ ratios were modeled using the mixed site distribution. The modeling results suggest that the change in surface potential caused by the formation of Al(OH)₃ on SiO₂ surface has significant effects on Cd²⁺ and SO₄²⁻ adsorption.