A kinetic model of the oxidative dissolution of brannerite, UTi2O6
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Bronwyn S. Thomas
Summary
The aqueous dissolution of synthetic brannerite (UTi2O6) in an open atmosphere has been investigated. Previous data in the literature have been combined with new experimental work, dealing with the release of uranium from brannerite as a function of solution pH and aqueous carbonate species, in oxygenated solutions. From these data we have developed a conceptual model for uranium release from brannerite consisting of two reaction steps: oxidation of surface uranium(IV) atoms, and subsequent detachment of U(VI) atoms into solution, which is catalysed by surface coordination with protons (acidic media) or carbonate species (alkaline media in equilibrium with the atmosphere). A kinetic rate law is derived for this simple reaction mechanism and fitted to experimental data. The resulting predictive equation for uranium release qualitatively describes the pH-dependent behaviour observed in experiment, and quantitatively gives an upper limit for uranium release from brannerite over a range of conditions and experiment types.
© 2003 Oldenbourg Wissenschaftsverlag GmbH
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Articles in the same Issue
- Chemical identification and properties of element 112
- Einsteinium chemistry in the gas phase: exploring the divalent character of heavy actinides
- Temperature dependence and effect of oxide anion on the americium chemistry in the molten LiCl-KCl eutectic
- Speciation of uranium(VI) at the solid/solution interface: sorption modeling on zirconium silicate and zirconium oxide
- A kinetic model of the oxidative dissolution of brannerite, UTi2O6
- Limiting transport properties of lanthanide and actinide ions in pure water
- Determination of Mo(VI), Ru(III), Re(VII) and NO3- in the solutions of nuclear fuel cycle by capillary electrophoresis
- Application of microanalytical techniques to the study of aqueous ion sorption phenomena on mineral surfaces
