Selenium sorption on clays in synthetic groundwaters representing crystalline bedrock conditions

The sorption behaviour of selenium on kaolinite and illite minerals in synthetic groundwaters was evaluated using the mass distribution coefficient, Rd, obtained in batch sorption experiments. The applied solutions were model solutions of fresh water, brackish water, saline water and glacial meltwater. The distribution coefficient values for illite varied between (0.4–60) × 10−3 and (11–720) × 10−3 m3 kg−1 for kaolinite. No clear effect of ionic strength or calcium concentration on the sorption was observed. The aqueous speciation calculations and the nonelectrostatic surface complexation model applied were in good accordance with the measured Rd values at a neutral pH range.