Study on the release of GMZ bentonite colloids by static multiple light scattering technique

Bentonite has emerged as the most promising buffer backfill material for radioactive waste storage underground. As a result, research on the natural release, migration, and stability of bentonite colloids is crucial for underground repository containment and radioactive migration, among other things. In this paper, both FT-IR and Raman techniques were used together to characterize the oxygen-containing bonds present in the GMZ bentonite skeleton, and the natural release process of GMZ bentonite colloids was monitored and analyzed dynamically in real-time using static multiple light scattering techniques. In addition, the effect of different conditions on GMZ bentonite colloidal generation were studied in detail. The results showed that the GMZ bentonite was composed primarily of montmorillonite and had a large number of abundant groups on its surface that can act as hydroxylated groups. The nature colloidal release stage could be divided into the swelling stage, the rapid release stage, the slow release stage and the equilibrium stage. The potential of GMZ bentonite to generate colloids in Beishan water was dramatically reduced. In strongly alkaline conditions (NaOH, pH≥12), the generation and stability of the GMZ bentonite colloids are unfavorable because of the dominance of Na+. Both the decrease in ionic strength and the increase in temperature are favorable for the generation of GMZ bentonite colloids. This work contributes to a better understanding of the effects of different environments on bentonite erosion and the understanding of the colloid release mechanism. It will also provide a valuable reference for the safety assessment of radioactive HLW in deep geological repositories.