The sorption of Eu on MX-80 bentonite in Na–Ca–Cl solutions is investigated at a molal proton concentration (pHm) range of 3 to 10 and an ionic strength (I) range of 0.1 to 6 m (mol·kgw−1). The sorption equilibrium of Eu on MX-80 is achieved within 14 to 21 d at I = 0.1 and 6 m. The sorption distribution coefficient (Kd) values of Eu for MX-80 increase as pHm increases from 3 to 6 for all I values, and they are independent of pHm between 8 and 10 at I ≥ 0.5 m. Meanwhile, at I = 0.1 m, the Kd value at pHm = 10 is slightly lower than those at pHm = 8 and 9. The Kd values are not affected by the I values between 0.5 m and 6 m, whereas the Kd value at I = 0.1 m is greater than those at I ≥ 0.5 m, except at pHm = 10. A two-site protolysis nonelectrostatic surface complexation and cation exchange sorption model is applied to the Eu sorption data for I ≤ 4 m, and the equilibrium constants of the sorption reactions are estimated.

1. Introduction
2. Experimental
    2.1 Materials
    2.2 Sorption Experiment
3. Results and Discussion
4. Conclusions
Acknowledgements
REFERENCES

• Jieci Yang(McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L7, Canada)
• Joshua Racette(McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L7, Canada)
• Fabiola Guido Garcia(McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L7, Canada)
• Shinya Nagasaki(McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L7, Canada) Corresponding author
• Tammy Yang(Nuclear Waste Management Organization, 22 St. Clair Ave. East, 4th Floor, Toronto, ON, M4T 2S3, Canada)