Sorption of Pd on illite, MX-80 bentonite and shale in Na–Ca–Cl solutions

Abstract

This paper examines sorption of Pd(II) onto illite, MX-80 bentonite, and Queenston shale in Na–Ca–Cl solutions of varying ionic strength (IS) from 0.01 to 6.0 mol/L (M) and pHc ranging from 3 to 9 under atmospheric conditions. A 2-site protolysis non-electrostatic surface complexation and cation exchange model was applied to the Pd sorption onto illite and MX-80 using PHREEQC, and the model results were compared to the experimental ones obtained in this work. Surface complexation and cation exchange constants were estimated for both illite and MX-80 through the optimization process to bring the predicted distribution coefficients from the model into alignment with the experimentally derived values. These optimized surface complexation constants were compared to existing linear free energy relationships (LFER).

Keywords

• Sorption
• Sorption distribution coefficient
• 2SPNE SC/CE model
• PHREEQC
• Geological disposal
• Palladium