Functionalized bisphosphonate extractants: A structure-property relationship study

Nuclear power has been identified as a source of safe, sustainable and clean source of future domestic energy production in the United States. The proper development of this type of energy requires an efficiently solved problem of the management of the nuclear waste. Current commitment to a once-through nuclear cycle, with a deep geologic repository as a final destination of waste, requires effort to develop methods for the reduction of volume and radiotoxicity of the radioactive waste streams and their safe transport and storage. As a part of separation and transmutation initiative, where intensely radioactive and long-lived isotopes are isolated and transmuted to less hazardous radioisotopes, this dissertation attempts to evaluate structural features of a powerful class of solvent extraction reagents---substituted bisphosphonic acids. Bisphosphonic acids are powerful metal chelating reagents and their organic-soluble partial esters have proven to be effective for lanthanide and actinide solvent extraction. A systematic physico-chemical profiling, supported by solvent extraction studies, is used to develop a comprehensive picture of structure-extraction correlation for symmetrically substituted bisphosphonic acids. An optimal combination of the structural features that optimize metal ion extraction efficiency is presented in this dissertation. Specifically, ligand aggregation in non-polar diluents, ligand acidity and basicity, organic/aqueous distribution equilibria and steric effects are investigated individually for a variety of structurally modified bisphosphonates. The observed structure-property relationships are discussed in terms of possible applications in the nuclear waste processing.