RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

Competitive adsorption of molybdate, selenite, selenate, chromate, and sulfate onto γ-Al₂O₃ was investigated in the present study. Binary-solute systems of MoO₄²⁻/SeO₃²⁻, CrO₄²⁻/SO₄²⁻, and CrO₄²⁻/SeO₄²⁻ as well as single anion systems were evaluated for the relative influence on competitive adsorption on oxide surface. As would be expected, the adsorption density of each anion in the binary-solute systems decreases, as compared to the respective density in a single anion system. Furthermore, MoO₄²⁻ inhibits SeO₃²⁻ adsorption in acidic condition and that SO₄²⁻ or SeO₄²⁻ depresses CrO₄²⁻. The order of the relative retainment of anions on oxide surface is molybdate>selenite>selenate∼sulfate>chromate, which corresponds to the magnitude of the overall proton coefficient of the corresponding anions.