Cesium immobilization in metakaolin-based geopolymers elucidated by 133Cs solid state NMR spectroscopy

20 October 2021, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Geopolymers are promising candidates for nuclear-waste immobilization, and more specifically for the immobilization of radioactive cesium. Low-Si metakaolin-based geopolymers cured at temperatures of 40°C in the presence of Cs ions generate a mixture of amorphous and crystalline phases including a Cs-bearing zeolite F phase. Using a combination of 133Cs solid-state NMR and X-ray powder diffraction measurements we were able to show that Cs preferentially binds to zeolite F even when zeolite F is not the dominant phase in the matrix. Moreover, post-leaching NMR experiments indicate that zeolite F binds Cs more efficiently than the remaining crystalline or amorphous phases. Tailoring geopolymer formulations so that a large fraction of zeolite F is generated may therefore be a promising route for the production of immobilization matrices for cesium.

Keywords

Nuclear waste management
133Cs solid state NMR

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