Application of a Site-Binding, Electrical, Double-Layer Model to Nuclear Waste Disposal

摘要

A site-binding, electrical, double-layer adsorption model has been applied to adsorption of Cs for both a montmorillonite clay and powdered SiO sub 2 . Agreement between experimental and predicted results indicates that C/sub s/ exp + is adsorbed by a simple cation-exchange mechanism. Further application of a combination equilibrium thermodynamic model and site-binding, electrical, double-layer adsorption model has been made to predict the behavior of U(VI) in solutions contacting either the montmorillonite clay or powdered SiO sub 2 . Experimentally determined U solution concentrations have been used to select what is felt to be the best available thermodynamic data for U under oxidizing conditions. Given the existing information about the probable U solution species, it was possible to determine that UO sub 2+2 is most likely adsorbed by cation-exchange at pH 5. At higher values (pH 7 and 9), it was shown that UO sub 2 (OH) sub 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 (either because of enhanced sorption or lowered solubility); however, the mechanism responsible for this behavior has not been determined. (ERA citation 06:031709)