Direct Dissolution and Electrochemical Investigation of Cerium and Uranium in Ionic Liquid

by Janelle Droessler

Institution: University of Nevada – Las Vegas
Year: 2016
Keywords: Cerium; Electrochemistry; Ionic Liquid; Neodymium; Separations; Uranium; Chemistry; Radiochemistry
Posted: 02/05/2017
Record ID: 2117101
Full text PDF: http://digitalscholarship.unlv.edu/thesesdissertations/2662


The solubility, coordination and speciation of f-elements in ionic liquids (ILs) has been the focus of numerous studies because the purely ionic systems have unique physical properties that can be exploited in comparison to aqueous, organic, or molten salt systems. Ionic liquids are thermally stable, have negligible vapor pressure, and are electrochemically stable at negative potentials that encompass the reduction potential of actinide species. Literature has suggested that the properties of ILs could potentially be utilized in the nuclear fuel cycle for separations and reprocessing. However, the solubility of f-elements in ILs has been significantly lower compared to traditional solvents. Additionally, further research is needed to understand the soluble f-element species in ILs and their electrochemical behavior. Methods of direct dissolution for cerium carbonate and uranium carbonate and oxide species into the IL, n-trimethyl-n-butylammonium bis(trifluoromethanesulfonyl)imide [Me3NnBu][TFSI], were developed. These demonstrate pathways for introducing f-elements into ILs without the use of extra synthesis routes. The reduction/oxidation of soluble cerium and uranium (uranyl) species in IL is examined at Au, Pt, and GC (glassy carbon) electrodes. Multi-wave voltammetry is consistent with the reductive deposition from the IL solution. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) confirm the deposition of cerium and uranium species at Au electrodes. Finally, an initial study of the separation of uranium from a lanthanide in ILs was attempted. The ability to electrodeposit and separate uranium from a mixture of uranium/neodymium in three ILs using electrochemical methods was investigated. The ILs contained the same TFSI anion and different cations. Electrochemical deposits obtained from the different ILs were rinsed and dissolved into 1 M HClO4 for UV-Vis spectroscopy and ICP-AES analysis to determine the concentration of uranium relative to neodymium in the initial solutions and resulting deposits. Advisors/Committee Members: Kenneth Czerwinski, David Hatchett, Ralf Sudowe, Patricia Paviet, Jacimaria Batista.