Mineralogical and hydrochemical effects on adsorption removal of cesium-137 and strontium-90 by kaolinite

Adsorption characteristics of the nuclides onto kaolinite were investigated by batch experiment under various pH conditions and concentrations of groundwater cations (Ca2+, Mg2+, K+ and Na+) and anions (HCO3-, CO32- and SO42-). Adsorption removal Cs-137 and Sr-90 by kaolinite greatly increased as the concentration of groundwater cations increased from 10(-5) to 10(-1) M. In contrast, the pH exerted a small effect on the adsorption of Cs-137 and Sr-90 onto kaolinite. The zeta potential of kaolinite particles showed a negative increase of amphoteric surface charge with increasing pH. The adsorption behavior of Sr-90 was also highly dependent on the concentration of bicarbonate. The thermodynamic saturation index indicated that bicarbonate exerts great effect on strontium adsorption by the precipitation of a strontianite (SrCO3) and a change in pH.