Electrodeposition of metallic uranium at near ambient conditions from room temperature ionic liquid

The electrochemical behavior of U(IV) in the room temperature ionic liquid (RTIL), N-methyl-N-propylpiperidinium bis(trifluoromethylsulfonyl)imide (MPPiNTf2), was investigated to evaluate the feasibility of using the RTIL for non-aqueous reprocessing application. In this context, the rate of dissolution of uranium oxide (UO2) in HNTf2 was studied at 353 K. The dissolution of UO2 in HNTf2 was rapid; nearly 50% of UO2 dissolved within 3 h and more than 95% dissolved in 25 h. The resultant solution was dried, diluted with MPPiNTf2 and the electrochemical behavior of U(IV) in MPPiNTf2 was studied at 373 K at platinum, glassy carbon and stainless steel electrodes. The cyclic voltammograms of U(IV) in MPPiNTf2 at platinum and glassy carbon electrodes consisted of four cathodic waves occurring at a peak potentials of −0.7 V (Fc/Fc+), −1.4 V, −2.2 V and −2.7 V. Controlled potential electrolysis of a solution of U(IV) in MPPiNTf2 at −2.8 V (Fc/Fc+) resulted in the deposition of metallic uranium, which was confirmed by X-ray diffraction and scanning electron microscopy.