Perfluoroalkyl substances (PFAS) are a class of highly recalcitrant and persistent compounds that pose a serious health concern as groundwater contaminants. PFAS are desirable commercial surfactants used in many everyday products due to their water and grease resistant properties, but this chemical resistance along with the strength of the C-F bond make them resilient to typical remediation strategies. Remediation approaches fall under two categories, destructive techniques and concentrate then remediate techniques (nondestructive). One such promising technique for destructive PFAS remediation is chemical oxidation using activated persulfate, which has shown promise for other groundwater contaminants such as pesticides, pharmaceuticals, and other organics. Previous work computationally investigating persulfate oxidation identified a principal mechanism for degrading perfluorooctanoic acid (PFOA) however no degradation has been shown for perfluorooctanesulfonic acid (PFOS). Therefore, in this work we have performed density functional theory (DFT) calculations to identify how chemical structure effects the primary oxidation reaction mechanism for several PFAS. The effect of chain length (e.g. C4 vs. C6 vs. C8) and polar head group (e.g. CO<sub>2</sub> vs. SO<sub>3</sub>) on the key oxidation electron transfer step were evaluated in several aqueous solvation regimes. Marcus theory was employed for studying the critical oxidation electron transfer step initiating PFAS decomposition. The results from this systematic study will help build a reaction model for PFAS oxidation and provide further understanding for how variation in PFAS structure effects the oxidation degradation mechanism.

Elucidating the effect of chemical structure on the PFAS oxidation decomposition pathway

ACS Spring Meeting 2021

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