Date of Award

2014

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Chemistry

Second Advisor

Copyright © 2014 Daniel Stephen Kissel

Third Advisor

Doctor of Philosophy (PhD)

Abstract

Nuclear energy, which has historically been considered an alternative energy solution in the United States, is regaining support as an efficient means of energy production. The viability of nuclear energy for the future, however, will remain suspect until issues involving the waste created are fully addressed in the next generation of advanced nuclear fuel cycles. The TALSPEAK process, developed at Oak Ridge National Laboratory, is a classic solvent extraction technique that employs a series of analytical separations in an effort to remove radioactive contaminants from spent nuclear fuel (SNF) and recover uranium in high purity. This separation utilizes a polyaminocarboxylic acid and a phosphorous extractant to separate trivalent actinides (An(III)s) from trivalent lanthanides (Ln(III)s). Conversely, issues with these reagents have hampered TALSPEAK's implementation as an industrial scale solution. The process requires a high concentration of lactic acid to facilitate phase separations, and the An(III)/Ln(III) separation factor is too low to achieve the purity required for artificial transmutation. Artificial transmutation involves steady neutron irradiation, which is impossible in the presence of Ln(III)s because of large neutron capture cross-sections. It is therefore critical to develop superior solvent extractants that effectively separate An(III)s from Ln(III)s.

The present study focuses on the design, synthesis, characterization and analysis of advanced polyaminocarboxylic acids and their metal complexes in an effort to identify potential TALSPEAK-type extractants with superior separation properties. A facile, higher yield synthesis of these ligands and their complexation of trivalent metal ions (Co(III), Al(III), Ga(III), and In(III)), and selected lanthanides are reported. The polyaminocarboxylic acids and their trivalent metal complexes were characterized by elemental analysis, mass spectrometry, IR spectroscopy and NMR spectroscopy. Quantum mechanical calculations were performed to obtain the relative stabilities of the three possible geometric isomers for pseudo-octahedral polyaminocarboxylate metal complexes in solution. The calculations were supported by X-ray crystallographic data obtained for different Co(III) and Ga(III) polyaminocarboxylate complexes. Advanced 2D NOESY and classic 1D NMR spectroscopy were used to differentiate experimentally between cis- (C1 symmetry) and both trans- (C2 symmetry) isomers. IR spectroscopy was used to investigate the nature of carboxylate binding for metal complexes isolated in the solid state.

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