Surface Complexation Modeling of Yb(III) and Cs(I) Sorption on Silica

This study employs a surface complexation model to elucidate the sorption behaviors of ytterbium (Yb) and cesium (Cs) on silica surfaces, critical for understanding their immobilization in geological contexts. The primary objective is to determine the surface acidity constants and complexation constants relevant to these two cations. Methodologically, the study involves a sequential extraction of surface acidity constants, revealing a logarithmic constant (Ka) of 7.60 for the surface–solution interface. This is followed by the assessment of cation sorption through deriving specific complexation constants, displaying a log K of 16.2 for Yb and 2.05 for Cs, with considerations for competitive sorption with sodium (Na), which exhibits a log K of 2.2. Results indicate that the modeled sorption reactions effectively capture the dynamics of Yb and Cs interaction with silica, emphasizing the comparative sorption affinities and the influence of competing ions in the environmental stability of these radionuclides. This research underscores the significance of silica as a prevalent mineral in the geosphere and contributes to the broader discourse on radionuclide migration and containment strategies.