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Etude de la spéciation de l'uranium(VI) dans les solutions d'acide phosphorique et de sa récupération par extraction liquide-liquide

Abstract : Because small amounts of uranium are present in phosphate rocks, wet phosphoric acids may contain up to 300 ppm of uranium(VI). Therefore, such acids are a cost-effective unconventional source of this metal. Its recovery is a challenge for metallurgical firms which must develop reliable and selective solvent extraction processes. Such processes need to know the chemical equilibria involved in the extraction process, the speciation of uranium and its thermodynamics in solution. These two last points have been investigated in this work. Firstly, the most probable species of uranium(VI) in phosphoric acid solutions have been selected thanks to a detailed review of the literature. Then, a thermodynamic model founded on an equation of state for electrolytes has been built according these hypotheses. It has been validated with speciation data coming from original ATR-IR spectroscopy measurements. Finally, the composition of the aqueous phosphoric acid solutions and the activity coefficients obtained have been combined with a chemical model of uranium(VI) extraction into an organic phase containing a synergistic mixture of bis(2-ethylhexyl)phosphoric acid (D2EHPA) and tri-n-octylphosphine oxide (TOPO) in order to represent the variation of the distribution coefficient of uranium(VI) with H3PO4 concentration. This model had been previously developed at Chimie ParisTech at a given concentration of H3PO4 (i.e., 5,3 mol/L), but in the present study we have tested its validity in an extended range of phosphoric acid concentrations (i.e., 1-7 mol/L) and improved it.
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Submitted on : Wednesday, December 16, 2015 - 12:25:32 AM
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  • HAL Id : tel-01244583, version 1



Adrien Dartiguelongue. Etude de la spéciation de l'uranium(VI) dans les solutions d'acide phosphorique et de sa récupération par extraction liquide-liquide. Chimie. ENSTA ParisTech, 2014. Français. ⟨tel-01244583⟩



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