RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

Uranyl sorption on samples from the vicinity of two uranium ore deposits was studied using a batch adsorption technique, and the results modelled using the surface complexation ap-proach. The use of a synthetic groundwater spiked with an artificial uranium isotope (²³⁶U) enabled adsorption to be mea-sured together with desorption of the natural uranium in the samples. The amount of ²³⁸U taking part in sorption interactions was estimated from the isotope exchange between ²³⁶U and ²³⁸U. This "accessible" fraction comprised approximately 20 per cent of the uranium in the samples, and the use of this amount rather than the total uranium content was more realistic for modelling purposes. Although the surface complexation model was only applied to sorption on the amorphous iron component of these complex samples, it gave a reasonable de-scription of experimental results.