Coordination and electrochemical behavior of U(VI) in dicyanamide ionic liquid

Abstract

The coordinating ability of the dicyanamide (DCA−) anion has been exploited for dissolving the uranyl nitrate in ionic liquid medium composed of 1-butyl-3-methylimidazolium dicyanamide (C4mImDCA) and N-butyl-N-methylpyrrolidinium dicyanamide (C4mPyDCA). The DCA− anion can act as either monodentate or bidentate ligand and therefore it can displace the nitrate ion from the uranyl coordination sphere, resulting in the formation of a wide variety of uranyl complexes in ionic liquid medium at different mole ratios of DCA− to uranium. The coordination environment of uranyl ion in those cases was investigated by Raman and FTIR spectroscopy and the abundances of various uranyl species were determined. The electrochemical benign properties of C4mImDCA and C4mPyDCA, in tandem with the reasonable solubility of uranyl nitrate in these ionic liquids has been utilized in the present study for understanding the redox behaviour of UO22+ in C4mImDCA and C4mPyDCA. The electrochemical behaviour of UO22+ was studied at glassy carbon working electrode at different temperatures by cyclic voltammetry. The diffusion coefficient of uranyl ion in ionic liquid medium was determined at various temperatures and compared with other ionic liquid systems.