Electrochemical behavior of uranium(VI) in 1-butyl-3-methylimidazolium chloride and in 0.05 M aliquat-336/chloroform

Alkali metal uranyl chloride (M2UO2Cl4 (M = Na or Cs)) was dissolved in 1-butyl-3-methylimidazolium chloride (bmimCl) and the redox behavior of uranyl ion present in the resultant solution was investigated by cyclic voltammetry at 343 K. The cyclic voltammogram consisted of a reduction wave occurring at the peak potential of -0.85 V, due to the reduction of U(VI) and two oxidation waves occurring at the peak potentials of -0.6 V and +0.2 V. Controlled potential electrolysis of uranium(VI) loaded bmimCl gave a black deposit, which was characterized as uranium oxide by EDXRF and XRD analysis. Extraction of uranium(VI) from nitric acid medium by 0.05 M tri-n-octylmethylammonium chloride (TOMAC) in chloroform was studied and the cyclic voltammogram of uranyl ion present in the extracted phase exhibited a single reduction (-0.8 V) and an oxidation wave (0.06 V) at 298 K. Controlled potential electrolysis of uranium(VI) loaded TOMAC at -1.0V also gave a black uranium oxide deposit similar to that observed in the previous case. The results indicated that uranyl ion in organic phase undergoes a single step two electron quasi-reversible reduction at the working electrode, which can be conveniently exploited for the direct recovery of uranium from the spent fuel or from high level liquid wastes.