RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

A site-binding, electrical, double-layer adsorption model was applied to adsorption of Cs for both a montmorillonite clay and powdered SiO₂. Agreement between experimental and predicted results indicates that Cs⁺ is adsorbed by a simple cation-exchange mechanism. Further application of a combination equilibrium thermodynamic model and site-binding, electrical, double-layer adsorption model was made to predict the behavior of U(VI) in solutions contacting either the montmorillonite clay or powdered SiO₂. Given the existing information about the probable U solution species, it was possible to determine that UO₂²⁺ is most likely adsorbed by cation-exchange at pH 5. At higher values (pH 7 and 9), it was shown that UO₂(OH)₂⁰ is probably the most strongly adsorbed U solution species. It was also found that high NaCl solution concentrations at higher pH values lowered U concentrations.