Effect of oxidation-reduction on the extraction of uranium from wet phosphoric acid by DEHPA/TOPO

Abstract

Uranium is recovered from wet phosphoric acid by DEHPA/TOPO in kerosene. Uranium is present in wet phosphoric acid in the tetravalent and hexavalent states but DEHPA/TOPO extracts uranium in the hexavalent state only. The ratio of U4+/U6+ depends on several factors such as the origin of the phosphate rock, the method of preparation of phosphoric acid and the presence of other impurities. Therefore it is important to oxidize the wet acid to convert all uranium to U6+ before extraction. Uranium is stripped from the solvent by a reverse process where a concentrated phosphoric acid is used under reducing conditions. This paper studies the oxidation of wet phosphoric acid from Homs plant/Syria by H2O2 oxidant and the effect of oxidation on extraction coefficientK. It also studies the reduction by iron and its effect on back extraction of uranium from the solvent to phosphoric acid.