Electrochemical Transformations of Perfluoroalkyl Acid (PFAA) Precursors and PFAAs in Groundwater Impacted with Aqueous Film Forming Foams

Abstract

While oxidative technologies have been proposed for treatment of waters impacted by aqueous film forming foams (AFFFs), information is lacking regarding the transformation pathways for the chemical precursors to the perfluoroalkyl acids (PFAAs) typically present in such waters. This study examined the oxidative electrochemical treatment of poly- and perfluoroalkyl substances (PFASs) for two AFFF-impacted groundwaters. The bulk pseudo first order rate constant for PFOA removal was 0.23 L h A; for PFOS, this value ranged from 0.084 to 0.23 L h A. Results from the first groundwater studied suggested a transformation pathway where sulfonamide-based PFASs transformed to primarily perfluorinated sulfonamides and perfluorinated carboxylic acids (PFCAs), with subsequent defluorination of the PFCAs. Transient increases in the perfluorinated sulfonamides and PFCAs were observed. For the second groundwater studied, no transient increases in PFAAs were measured, despite the presence of similarly structured suspected PFAA precursors and substantial defluorination. For both waters, suspected precursors were the primary sources of the generated fluoride. Assessment of precursor compound transformation noted the formation of keto-perfluoroalkanesulfonates only in the second groundwater. These results confirm that oxidation and defluorination of suspected PFAA precursors in the second groundwater underwent transformation via a pathway different than that of the first groundwater, which was not captured by total oxidizable precursor assay.

Photochemical transformation of perfluoroalkyl acid precursors in water using engineered nanomaterials

“…PrePFAAs have been detected in rivers, lakes, sediments, wastewater treatment plant (WWTP) effluents, and other environments (Chen et al, 2019, Gebbink et al, 2016, Schaefer et al, 2018, Wang et al, 2015.…”

US Department of Defense–Funded Research on Treatment of Per‐ and Polyfluoroalkyl Substance–Laden Materials

“…Analysis of groundwater from AFFF fire training source areas has revealed that a large fraction of the total organic fluorine remains unmeasurable via conventional analytical methods (Schaefer et al 2019). A groundwater sample from a DoD fire training source area was tested for the standard 24 PFAS analytes, total oxidizable precursors (TOPs), and also for total organic fluorine via combustion ion chromatography (TOF–CIC).…”

Understanding and Managing the Potential By‐Products of PFAS Destruction

“…, ), electrochemical treatment (Schaefer et al. ; Soriano et al ; Schaefer et al ; Pica et al. ; Schaefer et al ), and sonolysis (Vecitis et al ; Campbell et al.…”

“…The first (primary) is a direct electron transfer at the surface of the anode (Zhuo et al ). This makes the anode a design parameter, with many sources suggesting that boron‐doped diamond anodes are more advantageous than mixed metal oxide anodes due to their commercial availability, high reactivity, low adsorptivity, and ability to defluorinate a wide range of PFAS (Trautmann et al ; Schaefer et al ; Soriano et al ; Schaefer et al ; Schaefer et al ). This direct electron transfer from the PFAS molecule to the anode is theorized to be a sequential defluorination process that may generate short‐chain PFAAs (Gomez‐Ruiz et al ).…”