Electrochemical Oxidative Degradation of Perfluorooctanoic Acid in Organic Media

Electrochemical methods are promising strategies for the degradation of per- and polyfluoroalkyl substances (PFASs) but are currently not well developed for non-aqueous conditions relevant for PFAS sorbent regeneration without resorting to specialized electrode materials. We report the electrochemical degradation of perfluorooctanoic acid (PFOA) with tetramethylammonium hydroxide (TMAOH) using reticulated vitreous carbon (RVC) electrodes in acetonitrile. Under anodic oxidation, PFOA is converted to fluoride and shorter-chain perfluoroalkyl carboxylates, which were characterized and quantified using 19F nuclear magnetic resonance (NMR) spectroscopy, high-performance liquid chromatography-mass spectrometry (HPLC-MS), gas chromatography-mass spectrometry (GC-MS), and ion chromatography methods. The reaction mechanism is hypothesized to involve a direct electrooxidative decarboxylation followed by subsequent radical hydroxylation and alpha-fluoride elimination to form shorter-chain perfluorinated carboxylic acids. Under these electrochemical methods, PFOA undergoes near-complete conversion to form fluoride ions and small amounts of short-chain PFASs. However, under the reported conditions, we observed a significant loss in fluorine balance, which we attribute to the formation of volatile byproducts. This non-aqueous electrochemical approach to perfluoroalkyl carboxylic acid mineralization offers new insights into PFAS degradation mechanisms and shows potential for pollutant remediation under room temperature conditions utilizing inexpensive reagents and electrode materials.