Award Date

5-1-2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

First Committee Member

Kenneth Czerwinski

Second Committee Member

David Hatchett

Third Committee Member

Ralf Sudowe

Fourth Committee Member

Patricia Paviet

Fifth Committee Member

Jacimaria Batista

Number of Pages

177

Abstract

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.

Keywords

Cerium; Electrochemistry; Ionic Liquid; Neodymium; Separations; Uranium

Disciplines

Chemistry | Radiochemistry

File Format

pdf

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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