Date of Award

December 2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

Mark Dietz

Abstract

Solid sorbents have been applied to the separation of radionuclides since the advent of nuclear technology itself. First used for the cleanup and storage of radionuclides remaining from nuclear testing and nuclear power plants, these materials (e.g., inorganic and organic ion-exchange resins) were used to create solid nuclear waste forms as a way of reducing the potential for environmental contamination arising from storage of liquid wastes. The invention of nuclear medicine, which coincided with the introduction of nuclear technology, led to the need for high purity radionuclides for human use. One of the most widely used radionuclides in nuclear medicine is 99mTc, and its parent radionuclide, 99Mo has long been available only from foreign producers. Recently, there has been growing interest in the United States in developing a domestic source of 99Mo. The process for the separation of 99Mo from 235U fission product solution relies on TiO2, an inorganic sorbent. In this work, it was found that simple electrostatic adsorption does not explain retention of most ions on the sorbent, instead a more complex coordinated copolymerization is likely occurring. Despite this, chromatographic experiments yielded new solution conditions that affect a better separation compared to what is currently employed. In an effort to create a predominantly column-based 99Mo separation and purification process, a new extraction chromatographic (EXC) material employing CYANEX® 600 was prepared to replace or supplement the Cintichem Process, decreasing processing time and reducing the overall complexity of the separation process. Detailed acid and temperature dependencies presented a set of conditions for which a column containing the new Mo resin could be used to completely separate 99Mo from the Cintichem elements, providing quantitative recovery, which has not yet been seen using other sorbents. Once 99Mo is separated and purified from a 235U fission solution, a final separation must occur where 99mTc, generated from the decay of 99Mo, must be separated from 99Mo. A modern approach to that separation uses a solid sorbent, aqueous biphasic extraction chromatographic (ABEC) resin, which is based on solid sorbent-functionalized traditional liquid-liquid aqueous biphase separations. In this body of work, a new EXC material is created by impregnating one phase of an aqueous biphase in a support, and when contacted with the opposing phase, forms a solid supported aqueous biphase (SSABS). That SSABS is applied for the separation of 99mTc from 99Mo and the performance compared to ABEC. The experimental results reveal that SSABS may be a viable alternative to ABEC, showing equal performance to ABEC while also being more tunable than because the polymer phase impregnated within SSABS can be easily modified. Finally, it was previously reported that ABEC can also be used for environmental remediation, removing dyes from textile waste effluent. SSABS was studied as a dye extraction material and the performance compared to that of ABEC. It was found that SSABS showed not only greater extraction efficiency for nearly all dyes studied, but also the increased performance was aided by the synergism found to occur between the polymer-rich phase and the Amberlite XAD-16 support used.

Available for download on Saturday, December 23, 2023

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