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Solubility of U(VI) in chloride solutions. II. The stable oxides/hydroxides in alkaline KCl solutions: Thermodynamic description and relevance in cementitious systems

Neşe Çevirim-Papaioannou, Ezgi Yalçıntaş

2018enuraniumsolubilitythermodynamicscementhydrolysis

Abstract

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The solubility of U(VI) was investigated under undersaturation conditions in various concentrations of KCl–KOH solutions across a pH range of 7.5 to 14.6. Throughout the experiments, which were conducted under an Ar atmosphere at a temperature of (22 ± 2)°C, it was confirmed through XRD, quantitative chemical analysis, SEM–EDS, and TG–DTA that K2U2O7·1.5H2O(cr) is the solid phase that controls solubility in all systems at pH ≥ 9.5. Below this pH, the data suggested the presence of sub-stoichiometric phases. The concentration of uranium in equilibrium with K2U2O7·1.5H2O(cr) exhibited pH-independent behavior up to pH ≈ 11, showing a defined slope of +1 (log [U] vs. pH) at pH ≥ 11. These findings align with earlier reports of UO2(OH)3– and UO2(OH)42− species. The solubility product was derived from the combination of solubility data and past hydrolysis schemes, resulting in log *K°s,0{0.5K2U2O7·1.5H2O(cr)} = (12.0 ± 0.2). Derived SIT ion interaction coefficients for UO2(OH)3– and UO2(OH)42− with K+ enhance the thermodynamic database for U(VI), aiding in the calculations related to nuclear waste disposal in scenarios influenced by significant K concentrations and applicable redox conditions.

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Cite This Work

@article{9c14c9bd-c3f9-4c8a-adf9-b0cc1be1ff3b,
  title={Solubility of U(VI) in chloride solutions. II. The stable oxides/hydroxides in alkaline KCl solutions: Thermodynamic description and relevance in cementitious systems},
  author={Neşe Çevirim-Papaioannou and Ezgi Yalçıntaş},
  year={2018},
  language={en}
}
TY  - JOUR
TI  - Solubility of U(VI) in chloride solutions. II. The stable oxides/hydroxides in alkaline KCl solutions: Thermodynamic description and relevance in cementitious systems
AU  - Neşe Çevirim-Papaioannou
AU  - Ezgi Yalçıntaş
PY  - 2018
LA  - en
ER  -

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