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Dissertation/Thesis Abstract

Electrical Capacitance and Adsorption of Uranyl Peroxide Clusters and Photocatalytic Application of Uranium-Doped TiO2
by Liu, Yi, Ph.D., University of Notre Dame, 2017, 152; 13836265
Abstract (Summary)

Nuclear energy is a source of electricity without carbon dioxide emission. Uranium is a major component in nuclear fuel and radioactive waste, and is the heaviest element naturally available in large quantities. Uranium is also a major environmental contaminant at many former mine sites, as well as Cold War weapons production facilities.

Hexavalent uranium is relatively soluble in aqueous systems, and its fate is heavily impacted by the details of its complex solution speciation. Over the past decade a complex family of uranyl peroxide nanoscale cage clusters have been developed that have potential applications in the nuclear fuel cycle, and may impact the environmental fate of uranium in specific conditions. The behavior of uranyl peroxide clusters, such as solubility, stability, speciation, and aggregation are essential to control clusters in solution.

The electrical capacitance of uranyl peroxide clusters in water has been measured, and provides information concerning the electrical double layer formed in dilute cluster solutions. Cyclic voltammetry was used to study the relationship between effective capacitance and cluster concentration of uranyl peroxide cluster solutions of U60 (Li48+mK12(OH) m[UO2(O2)(OH)]60(H2O) n, m≈20, n≈310 in the solid state). The study indicated that dissociation of counter cations from clusters impacts the capacitance of the resulting cluster solutions.

Decontamination of soluble uranyl peroxide clusters U60 and U24Pp ([(UO2)24(O2)24(P 2O7)12]48-) by SBA-15, a mesoporous sorbent, was investigated. Characterization techniques, including Raman spectroscopy, electrospray ionization mass spectroscopy, transmission electron microscopy (TEM), and N2 adsorption/desorption were utilized to analyze the interaction between the uranyl peroxide clusters and SBA-15. The sorption kinetics and isotherms were studied to explore and compare the impacts of the structures of these two clusters.

The impact of doping uranium in TiO2 relative to its photocatalytic performance under natural sunlight was examined. Uranium-doped TiO2 were prepared, and the crystal structure and oxidation states of uranium were systematically characterized. The influence of the band gap energy and oxidation states of uranium on the photocatalytic performance of Rhodamine B degradation was found to be significant.

Indexing (document details)
Advisor: Burns, Peter C.
Commitee: Burns, Peter C., Camden, Jon, Lieberman, Marya
School: University of Notre Dame
Department: Chemistry and Biochemistry
School Location: United States -- Indiana
Source: DAI-B 80/06(E), Dissertation Abstracts International
Subjects: Chemistry, Inorganic chemistry, Materials science
Keywords: Decontaminent, Electrical double layer, Photocatalysis, Semiconductor, Uranyl peroxide cluster
Publication Number: 13836265
ISBN: 978-0-438-83398-2
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