Sequential recovery of uranium oxides by electrolysis of M2WO4-M2W2O7-UO2WO4 melts (M = Li, Na, K, Cs)

The effect of the electrolyte composition and solvent salt cation on the oxygen coefficient of the cathode product (O/U atomic ratio) and on the main characteristics of potentiostatic electrolytic deposition of UO₂ (cathode current efficiency, current density, product deposition rate) in sequential recovery of uranium oxides from electrolytes of the system M₂WO₄-M₂W₂O₇-UO₂WO₄ (M = Li, Na, K, Cs) in air was examined. The dependence of the oxygen coefficient of the cathode product on the electrolyte composition and solvent salt cation does not differ essentially from that observed previously in short experiments with low melt depletion of U. The current efficiency, initial current density, and product deposition rate decrease with the electrolyte depletion of U. The results obtained are satisfactorily accounted for in terms of the model of ionic composition of uranyl-containing oxide salt electrolytes, based on the concept of complexation and stepwise solvolysis of uranyl ions, taking into account formation of lower valence forms of U due to chemical corrosion of the cathode product.