Sorption of Eu(III) Onto MX-80 and Granite in Ca-Na-Cl Solutions

Jianan Liu¹, Shinya Nagasaki^1,*, Tianxiao (Tammy) Yang²

¹McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L7, Canada
²Nuclear Waste Management Organization, 22 St. Clair Ave. East, 4th Floor, Toronto, ON, M4T 2S3, Canada

Received 2025-03-02 ; Revised 2025-04-01 ; Approved 2025-05-26

Abstract

The sorption of Europium(III) (Eu(III)) on MX-80 bentonite and granite was systematically studied as a function of ionic strength (0.05 – 1 mol·kgw−1) and pHm (4–9) in Ca-Na-Cl solutions by batch experiments and 2-site protolysis no electrostatics surface complexation and cation exchange (2SPNE/CE) model. Eu(III) has often been used as a chemical analogue of plutonium(III) which is an important element of interest for the safety assessment of a deep geological repository (DGR) for nuclear waste. It was found that the sorption of Eu(III) on MX-80 and granite was dependent on pHm. The sorption of Eu(III) on MX-80 was dependent on ionic strength at pHm ≤ 6. The effect of ionic strength on the sorption of Eu(III) on granite was negligible. The 2SPNE/CE model simulation suggested that the ion exchange reaction might be the main sorption mechanism at low pHm, while the surface complexation reactions might be the dominant sorption mechanism at higher pHm for the sorption of Eu(III) on both MX-80 and granite.

Key Words : Europium, Sorption, MX-80, Granite, 2SPNE/CE