Optimal Si/al molar ratio achieves ultra-high CeO₂ loading and enhanced stability for nuclear waste immobilization in...

Glass matrices with high waste load capacity, stability, and economic viability holds significant technological implications for efficient and safe nuclear waste immobilization. Aluminosilicate glasses with various Si/Al molar ratios were successfully prepared by incorporating Al₂O₃ into natural granite, effectively enabling precise regulation of the Si/Al ratios and overcoming the challenge of achieving complete vitrification. Here, we report a glass waste form with ultra-high CeO₂ loading (up to 20 wt%) that exhibits excellent structural stability. At a Si/Al molar ratio of 3:1, cerium can incorporate into the glass network by forming Ce-O bonds through coordination with oxygen atoms in the [AlO₆] units. [AlO₆] is converted to more stable [AlO₄], thereby enhancing the stability of the glass. Up to 20 wt% CeO₂ (9.62 mol%) can be fully incorporated into the glass system, where approximately 79.71 % of the bridging oxygen atoms form stable Si-O-Si and [AlO₄] units, contributing to a structurally robust glass network. The Ce-O bond length in the glass matrix is shorter (2.27 Å) than in CeO₂, confirming enhanced coordination stability and aligning with superior chemical durability and mechanical properties. This work highlights the critical role of the Si/Al molar ratio and establishes low-cost granite could serve as a viable host material for nuclear waste immobilization.