Award Date

December 2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

First Committee Member

David Hatchett

Second Committee Member

Frederic Poineau

Third Committee Member

Kenneth Czerwinski

Fourth Committee Member

Alexander Barzilov

Number of Pages

178

Abstract

Procuring F-element metals is no simple task and often requires the use of caustic and hazardous materials at high temperatures. These materials are invaluable for a variety of scientific missions ranging from the elucidation of fundamental properties, as fast spectrum nuclear fuel forms, to pit production modernizing our nuclear stockpiles. Metallic actinide materials are essential to strategic and critical materials recovery, the nuclear energy sector, and weapons production. Room temperature electrolysis is envisioned as a process to recover laboratory scale (milligram to gram) quantities of actinide metals. This process closes the uranium chemical loop allowing the reclamation of materials for continued laboratory use. Ionic liquids (IL) at ambient temperature are used to electrochemically reduce and deposit uranium as a gateway element to other actinides. Reactions designed to enhance the solubility of uranium in the IL produce several species including truly anhydrous U(TFSI)3•3THF, UO2(TFSI)2•3THF and a second reporting of hexavalent UO2I4-2 anion found for the first time coordinated to the IL cation. These compounds are evidenced by UV/vis and RAMAN spectroscopy, TGA – DSC, SCXRD and EXAFS analyses. Uranium metal electrodes are characterized and used for the electro-reduction of uranium IL species. Controlled potential electrolysis and differential pulsed amperometry are investigated as electrolytic techniques for metal deposition. Variation in potential pulse frequency show changes in the nature of the collected deposits. Extended periods of electrolysis are required to collect milligram amounts of material and define solid electrode deposition as a low throughput method. High potential applications to radioactive materials exemplify the robustness of the IL as a stable radiolytic and electrochemical medium suitable for modified separations processes. The obtained deposits are finely divided and loosely fixed to the electrode surface which react quickly and complicate metal phase determination. Efforts were extended to establish an electrochemical amalgamation and thermal vacuum mercury extraction system within an inert atmosphere environment. The custom glovebox, contains both an electro-amalgamation station and a high temperature vacuum furnace. The electro-amalgamation system is tested with aqueous pH buffered and non-aqueous (IL) media. Proof of principle is verified through the recovery of gold and cerium amalgams. Alterations to the furnace vacuum level and temperature ramp rate have enabled metal recovery without losses to distillational sputtering. Thermal extraction has recovered milligram amounts of both metal-mercury condensate and purified metals.

Keywords

Actinide; Anhydrous; Electrochemistry; Metal; Radiochemistry; Uranium

Disciplines

Analytical Chemistry | Chemistry | Inorganic Chemistry

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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