Less hazardous and effective oxidant for solvent extraction of uranium in phosphoric acid solutions

Phosphoric acid is one of the secondary sources of uranium which provides significant contribution for the demand of uranium. The solvent extraction procedure has been normally employed for recovery of uranium from phosphoric acid. D2EPHA with TOPO mixture in Hydrocarbon diluents has been used as a solvent. Before the solvent extraction, uranium valence conditioning may be done bypassing air/O₂ and finishing with H₂O₂ addition. Oxidation reduction potential (ORP) of the acid should be >500 mV which is the suitable for solvent extraction. In the valence conditioning process, pre-treated phosphoric acid is conditioned for uranium valence states from +4 to +6 which is indicated by ORP values. On consideration to the hazardous nature of H₂O₂ and instability of ORP with the time, an effective and less hazardous oxidant is being need of the hour. In this juncture, fluoride ion which is always present with wet phosphoric acid may stabilise the fourth valence state of uranium (U⁴⁺) which is highly unstable in aqueous solutions. Hence, if we remove fluoride ion availability by complex formation with suitable metal ion, U⁴⁺ ion will automatically will oxidise to U⁶⁺ state (as UO₂ ²⁺ ion). Taking this point in to consideration, Al³⁺ ion which is forming strong complexes with fluoride ion was chosen and further study was carried out. In this study, Pre-treated phosphoric acid was added with different amounts of Al(NO₃)₃ solutions. ORP measured at different times. From the results obtained, it has shown that aluminium nitrate valence conditioning was effective in extraction of uranium in cycle I and cycle II