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Dhanpat Rai, Andrew R. Felmy, Nancy J. Hess, V. L. LeGore, D. E. McCready

Thermodynamics of the U(VI)-Ca²⁺-Cl^--OH^--H₂O system: Solubility product of becquerelite

The solubility of synthetic becquerelite (Ca(UO₂)₆O₄(OH)₆·8H₂O) was determined in 0.02, 0.1, and 0.5 M CaCl₂ solutions and at pC_H⁺ values ranging from approximately 4 to 11. The presence of becquerelite in equilibrated samples was confirmed by a combination of techniques involving X-ray diffraction, total chemical composition, and analyses of solubility data. The solubility data were interpreted using Pitzer´s aqueous thermodynamic model and the thermodynamic data for U(VI) species available in the literature. The log of the solubility product for becquerelite [Ca(UO₂)₆O₄(OH)₆·8H₂O + 14H⁺ ↔ Ca²⁺ + 6UO₂²⁺ + 18H₂O] was determined to be 41.4±0.2. This value is similar to the values previously reported for other synthetic becquerelites, but is drastically different from a value reported for a natural sample.

Radiochimica Acta, Oldenbourg Wissenschaftsverlag

Print ISSN: 0033-8230
Volume: 90, 09/2002
Pages: 495

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