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From uranothorites to coffinite: a solid solution route to the thermodynamic properties of USiO4
- Source :
- Inorganic Chemistry, Inorganic Chemistry, 2013, 52 (12), pp.6957-6968. ⟨10.1021/ic400272s⟩, Inorganic Chemistry, American Chemical Society, 2013, 52 (12), pp.6957-6968. ⟨10.1021/ic400272s⟩
- Publication Year :
- 2013
-
Abstract
- Experiments on the solubility of intermediate members of the Th(1-x)U(x)SiO4 solid solution were carried out to determine the impact of Th-U substitutions on the thermodynamic properties of the solid solution and then allow extrapolation to the coffinite end member. The ion activity products in solutions equilibrated with Th(1-x)U(x)SiO4 (0 ≤ x ≤ 0.5) were determined by dissolution experiments conducted in 0.1 mol·L(-1) HCl under Ar atmosphere at several temperatures ranging from 298 to 346 K. For all experiments, dissolution was congruent, and a constant composition of the aqueous solution was reached after 50-200 days of dissolution. The solubility product of thorite was determined (log *K(S,ThSiO4) = -5.62 ± 0.08) whereas the solubility product of coffinite was estimated (log *K(S,USiO4) = -6.1 ± 0.2). The stoichiometric solubility product of Th(1-x)U(x)SiO4 reached a maximum value for x = 0.45 ± 0.05. In terms of the standard Gibbs free energy of dissolution, solid solutions dissolve more spontaneously than the end members. The standard Gibbs free energy associated with the formation of thorite, coffinite, and intermediate members of the series were then evaluated. The standard Gibbs free energies of formation were found to increase linearly with the uranium mole fraction. Our data at low temperature clearly show that uranothorite solid solutions with x0.26, thus coffinite, are less stable than the mixture of binary oxides, which is consistent with qualitative evidence from petrographic studies of uranium ore deposits.
- Subjects :
- Aqueous solution
Chromatography
Chemistry
Analytical chemistry
Solubility equilibrium
[CHIM.INOR]Chemical Sciences/Inorganic chemistry
010402 general chemistry
010502 geochemistry & geophysics
01 natural sciences
0104 chemical sciences
Gibbs free energy
Inorganic Chemistry
symbols.namesake
symbols
[CHIM.CRIS]Chemical Sciences/Cristallography
[CHIM]Chemical Sciences
Coffinite
Physical and Theoretical Chemistry
Solubility
Dissolution
[CHIM.RADIO]Chemical Sciences/Radiochemistry
Stoichiometry
ComputingMilieux_MISCELLANEOUS
0105 earth and related environmental sciences
Solid solution
Subjects
Details
- ISSN :
- 1520510X and 00201669
- Volume :
- 52
- Issue :
- 12
- Database :
- OpenAIRE
- Journal :
- Inorganic chemistry
- Accession number :
- edsair.doi.dedup.....82627c0bb150b1952e4936b874504d9a
- Full Text :
- https://doi.org/10.1021/ic400272s⟩