Technetium-99 is identified as an element of interest for the safety assessment of a deep geological repository for used nuclear fuel. The sorption behavior of Tc(IV) onto MX-80 and granite in Ca-Na-Cl solutions of varying ionic strength (0.05–1 mol·kgw−1 (m)) and across a pHm range of 4–9 was studied in this paper. Sorption of Tc(IV) was found to be independent of ionic strength in the range of 0.05 to 1 m for both MX-80 and granite. Sorption of Tc(IV) on MX-80 increased with pHm from 4 to 7 and then decreased with pHm from 8 to 9. Sorption of Tc(IV) on granite gradually increased with pHm from 4 to 8 and then became almost constant or slightly decreased with pHm from 8 to 9. A 2 site protolysis non-electrostatic surface complexation and cation exchange sorption model successfully simulated sorption of Tc(IV) on MX-80 and granite. Optimized values of surface complexation constants (log K0) are proposed.

1. Introduction
2. Experimental
    2.1 Materials
    2.2 Sorption Experiment
3. Results and Discussion
    3.1 Sorption Kinetics
    3.2 Sorption on MX-80
    3.3 Sorption on Granite
4. Conclusions
Conflict of Interest
Acknowledgements
REFERENCES

• Shinya Nagasaki(McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L7, Canada) Corresponding author
• Zhiwei Zheng(McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L7, Canada)
• Jianan Liu(McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L7, Canada)
• Jieci Yang(McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L7, Canada)
• Tammy (Tianxiao) Yang(Nuclear Waste Management Organization, 22 St. Clair Ave. East, 4th Floor, Toronto, ON, M4T 2S3, Canada)