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dc.contributor.advisorVyas, Shubham
dc.contributor.authorCarre-Burritt, Asa E.
dc.date.accessioned2022-10-07T22:01:00Z
dc.date.available2022-10-07T22:01:00Z
dc.date.issued2022
dc.identifierCarreBurritt_mines_0052E_12362.pdf
dc.identifierT 9312
dc.identifier.urihttps://hdl.handle.net/11124/15395
dc.descriptionIncludes bibliographical references.
dc.description2022 Spring.
dc.description.abstractPer- and polyfluoroalkyl substances (PFAS) are highly-fluorinated anthropogenic organic compounds that have been integral to technologies ranging from nuclear isotope separation to hydrocarbon fire suppression formulations ever since their production began at scale nearly a century ago. Their extensive production and application led to ubiquitous occurrence in the environment and biota. Eventually, epidemiological hazards were reported for certain PFAS, leading to a torrent of research pouring forth investigating the relationships between PFAS, humans, and the human habitat. There is now consensus that the proliferation of PFAS throughout the biosphere is an issue that must be addressed. Herein, Chapter 1 introduces PFAS history and properties, then discusses their life cycle considerations. Thousands of different PFAS are expected to environmentally transform into perfluoroalkyl carboxylic acids (PFCAs). These compounds are strong acids that typically exist as conjugate-base anions at environmentally relevant pH, making them water soluble and causing drinking water to be notable mechanism of human exposure. Dealing with PFCA-contaminated water is difficult and conventional water treatment technologies are considered insufficient. Using sulfate radical anion (SO4•–) produced from persulfate (S2O82–) activation is an alternative approach that has been extensively investigated, in particular for in-stiu aqueous PFCA degradation. There have been disparate observations for the influence of pH on activated persulfate PFCA oxidation efficiency. Chapter 2 describes laser flash photolysis experiments used to measure absolute rate constants (k°s) for PFCA oxidation by SO4•– at variable pH values. k°s were similar, suggesting that SO4•– scavenging by other matrix constituents is one likely culprit for previous mixed results. In addition, density functional theory (DFT) calculations were performed to investigate literature hypotheses that SO4•– protonation at low pH promotes PFCA oxidation. Results suggested that aqueous SO4•– protonation is thermodynamically unfavorable. Chapter 3 describes a DFT study on modeling SO4•– in aqueous media for accurate thermodynamic property predication. Including a large number of explicit water molecules alongside a dielectric continuum implicit solvent model improved standard reduction potential (E°) predictions relative to the empirical value. pH effects were also investigated: DFT models incorporating a proton and a new interpretation of the chemical literature both suggested that the SO4•– aqueous E° is largely pH independent. On the basis of tabulated E° values, it was hypothesized that in a proton-bearing redox couple, hydroxyl radical (OH•) is another transient radical that can oxidize PFCAs: reactivity that has been contested extensively. In Chapter 4, photochemically produced OH• in a low-pH aqueous matrix was found to oxidize protonated PFCAs, suggesting an H-atom abstraction mechanism. Alternative electron transfer reactivity was investigated according to Marcus theory using energies from DFT calculations. Results were consistent with an H-atom abstraction vs. single-electron transfer mechanism. Finally, a summary of major conclusions and future outlooks for this collection of work is presented in Chapter 5.
dc.format.mediumborn digital
dc.format.mediumdoctoral dissertations
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado School of Mines. Arthur Lakes Library
dc.relation.ispartof2022 - Mines Theses & Dissertations
dc.rightsCopyright of the original work is retained by the author.
dc.subjectAOP
dc.subjectenvironmental remediation
dc.subjectLFP
dc.subjectPFAS
dc.subjectPFCA
dc.titleTale of how two transient radicals destroy persistent perfluoroalkyl carboxylic acids, The
dc.typeText
dc.date.updated2022-10-01T01:10:14Z
dc.contributor.committeememberEberhart, Mark E.
dc.contributor.committeememberSellinger, Alan
dc.contributor.committeememberStrathmann, Timothy J.
thesis.degree.nameDoctor of Philosophy (Ph.D.)
thesis.degree.levelDoctoral
thesis.degree.disciplineChemistry
thesis.degree.grantorColorado School of Mines


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