NUK - logo
E-viri
Celotno besedilo
Recenzirano Odprti dostop
  • Spectroscopic identificatio...
    Yorkshire, Antonia S; Stennett, Martin C; Walkley, Brant; Provis, John L; Townsend, Luke T; Haigh, Latham T; Hyatt, Neil C; Mottram, Lucy M; Corkhill, Claire L

    Scientific reports, 02/2023, Letnik: 13, Številka: 1
    Journal Article

    Portland cement-based grouts used for radioactive waste immobilisation contain a Ca- and Si-rich binder phase, known as calcium-silicate-hydrate (C-S-H). Depending on the blend of cement used, the Ca/Si ratio can vary considerably. A range of C-S-H minerals with Ca/Si ratios from 0.6 to 1.6 were synthesised and contacted with aqueous U(VI) at 0.5 mM and 10 mM concentrations. Solid-state Si MAS-NMR spectroscopy was applied to probe the Si coordination environment in U(VI)-contacted C-S-H minerals and, in conjunction with U L -edge X-ray absorption spectroscopy analysis, inferences of the fate of U(VI) in these systems were made. At moderate or high Ca/Si ratios, uranophane-type uranyl silicates or Ca-uranates dominated, while at the lowest Ca/Si ratios, the formation of a Ca-bearing uranyl silicate mineral, similar to haiweeite (Ca(UO ) Si O (OH) ·3H O) or Ca-bearing weeksite (Ca (UO ) Si O ·10H O) was identified. This study highlights the influence of Ca/Si ratio on uranyl sequestration, of interest in the development of post-closure safety models for U-bearing radioactive waste disposal.