Radium sorption on biotite; surface complexation modeling study

The sorption of Ra on Olkiluoto biotite in the context deep geological disposal spent nuclear fuel was studied with isotherm batch experiments. Ba used as an analog for experiments and modeling studies. A wide concentration range Ra/Ba studies (2.6 × 10?9 M to 1 10?3 M) addition four different reference groundwaters salinity types ranging from fresh saline. Experimental results show that both saline groundwaters, distribution coefficients tend decrease higher concentrations Ba. With one groundwater, increased due significant coprecipitation Ra. were consistently approximately order magnitude lower than groundwater. PHREEQC multi-site complexation model coupled optimization tool Python interpret experimental results. Molecular CASTEP code implemented into Materials Studio update more realistic site density data. It observed while predicts well concentrations, auxiliary reactions disrupt high concentrations. modeled coefficient data can be safety case calculations Finland Sweden.