Electrochemistry of soluble UO22+ from the direct dissolution of UO2CO3 in acidic ionic liquid containing water

[Display omitted] ► The direct dissolution of uranyl carbonate into wet ionic liquid containing HTFSI was achieved. ► The soluble species from the dissolution UO2CO3 in water and IL containing HTFSI was probed using UV/vis spectroscopy. ► Electrochemical deposition of UO2 from IL was achieved at an Au electrode in the presence of water. ► The deposition of UO2 at Au was confirmed using SEM/EDX analyses. The direct dissolution of UO2CO3 in neat and “wet” ionic liquid (IL) trimethyl-n-butylammonium bis(trifluoromethansulfonyl)imide [Me3NnBu][TFSI] is examined. The ionic liquid serves as both the solvent for the direct dissolution of UO2CO3(s) and the electrolyte solution for the electrochemical analysis of the soluble uranyl species. The solubility data indicate that displacement of the CO32− occurs slowly due to the low concentration of protons available from residual water in the pristine IL. Enhanced dissolution of UO2CO3 through the formation of carbonic acid H2CO3 is achieved after the addition of acid, bis(trifluoromethanesulfonyl)amide (HTFSI) and water. The soluble uranyl cation can then coordinate with the TFSI anion in place of the displaced CO32− anion following the decomposition of carbonic acid and purging of CO2(g) and water from the IL. The solubility of UO2CO3 was examined using liquid scintillation counting of 233U for the pristine ionic liquid. The “wet” ionic liquid containing HTFSI and soluble UO2CO3 was evaluated using UV/vis spectroscopy before and after dissolution. The electrochemical deposition of uranium species from ionic liquid was evaluated using cyclic voltammetry. The potential mediated deposition of uranium species was achieved and verified using scanning electron microscopy (SEM) and the solid uranium deposits were evaluated using energy dispersive X-ray emission spectroscopy (EDX).