Insights into the leaching behavior of pollucite glass-ceramics at the initial stage

HL Yang and SQ Ma and SJ Zhao and QK Wang and XH Liu and PG He and DC Jia and Y Zhou, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 106, 657-670 (2023).

DOI: 10.1111/jace.18726

Pollucite has been proposed as an ideal candidate material for addressing the critical challenge of the safe trapping of the Cs-137 radionuclide. However, its detailed corrosion mechanism remains elusive. In this work, we performed reactive and ab initio molecular simulations to explore the leaching behavior of Cs+ from pollucite glass-ceramics at the initial stage. The nonbridging oxygen ions on the surface are protonated at first, followed by the release of Cs+ associated with these oxygen ions. For the glass phase, the inner Cs+ could leach out due to the interaction with water molecules, whereas only the Cs+ present at the surface leach out for pollucite, confirming its remarkable chemical stability. The hydrolysis of Si/Al-O bonds in pollucite is thermodynamically unfavorable, and Al-O bonds are the weak spots. Moreover, the migration barriers of Cs+ in pollucite were calculated by the climbing image nudged elastic band method, and the high barriers reveal that pollucite immobilizes Cs+ stably. This study paves the way for predicting the long-term safety of a nuclear waste immobilization repository.

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