Adsorption of barium and radium on montmorillonite: A comparative experimental and modelling study

The widely favored option for the safe storage of high-level radioactive waste is a multi-barrier disposal system with clay-based geotechnical barriers e.g. bentonite. Montmorillonite as major constituent bentonite (up to 90 wt.-%) an important sink potentially released radionuclides. adsorption 226Ra and Ba on Na-montmorillonite (SWy-2) was investigated function pH (edges) concentration (isotherms) at different ionic strengths. often used chemical analogue due their closely related physical properties formation complete Ba/Ra solid solutions. experimental data could be quantitatively described by considering cation exchange reactions planar sites montmorillonite. To describe dependent Ra high strength pH, additional reaction involving surface complexation necessary. fitted selectivity coefficients (Kc) respect Na are very similar low (0.02 M), whereas higher (0.3 appears more selective.