Per- and polyfluoroalkyl substances (PFAS) are man-made compounds containing multiple carbon–fluorine bonds. The unique properties of this strong bond simultaneously make PFAS useful for a number of industrial and consumer applications, toxic to living organisms, and difficult to remediate. Because the pervasive pollution of water sources with PFAS occurs at low parts-per-trillion or parts-per-billion PFAS concentrations, specially formulated adsorbents with high PFAS affinity are needed to remediate contaminated drinking and wastewater. However, until recent years, the factors affecting adsorbents’ affinity for PFAS were unclear. Here we present one example of a PFAS adsorbent, based on β-cyclodextrin, that was intended to determine whether fluorophilicity plays a role in PFAS adsorption. As the PFAS adsorbent field has come to a better understanding of how to adsorb anionic PFAS, the next problem to surmount has become the question of what to do with PFAS-containing waste streams, whether wastewater, filtration retentate, contaminated filter media, aqueous film-forming foam (AFFF), contaminated soil, or other PFAS-related waste. PFAS degradation technologies, still in their infancy, have to this point mostly focused on easily scalable methods of injecting large amounts of energy into the PFAS-containing system. Significantly, the relevant degradation mechanisms are neither well-understood nor well-controlled. Here, we present a method that both degrades and defluorinates PFAS without speciating the PFAS into a distribution of intermediate-length fluorocarbon compounds. This method can degrade some PFAS compounds at temperatures as low as 40 °C. Computational investigations of the mechanism revealed a previously unrecognized defluorination pathway mediated by hydroxide-driven fluoride elimination. Systematic variations in the characterized byproducts support the computational results. This method is extended from the original perfluorocarboxylic acid substrates to branched perfluoroether carboxylates, and might be further extended to other classes of PFAS as methods to activate the headgroups of compounds such as perfluorosulfonic acids are developed. Other strategies for the continuation of this degradation work are also presented.

Creator

• Trang, Brittany

DOI

• https://doi.org/10.21985/n2-eg2x-we43

Subject

• Chemistry

Language

• en

Alternate Identifier

• http://dissertations.umi.com/northwestern:16178
• etdadmin_upload_920884

Keyword

• PFOA
• degradation
• PFAS
• mechanism
• cyclodextrin
• destruction

Date created

• 2022-01-01

Resource type

• Dissertation

Rights statement

• In Copyright