Per- and poly-fluorinated alkyl substances (PFAS) are a class of surfactants used in a wide range of industrial and consumer goods. However, their ubiquity, usage, and chemical resistance gives rise to harmful environmental exposure and bioaccumulation throughout nature. Techniques for PFAS remediation are under heavy investigation and include both nondestructive and destructive approaches. Experimentally, induced degradation of PFAS via reduction has shown success degrading both PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonic acid), two of the most high-profile PFAS chemicals, making it an exciting destructive remediation technique. Furthermore, reduction of PFAS using hydrated electrons has been observed, however the degradation mechanism of PFAS reduction is still unknown. Two major reaction channels are proposed for reduction induced PFAS degradation, concerted and stepwise bond dissociation, and the channels are highly dependent on the chemical structure. In addition, dissociation can occur at C-F bonds, C-C bonds, or involve the polar head group, increasing the complexity of the reduction process. In this study we have investigated PFAS reduction using density functional theory (DFT) to gain insight into the reduction mechanism. Using pervious experimental data, Marcus Theory and Saveant’s dissociative electron transfer theory have been benchmarked for nondissociative and dissociative reaction channels, respectively. Moreover, the electron transfer theories have been applied to investigate how the PFAS chemical structure affect the reduction and subsequent degradation reactions. Finally, the established computational protocol has been applied to dimeric PFAS systems to assess the effect of premicellar aggregation on reduction. The results of this study will be presented.

PFAS degradation via reduction by hydrated electron: A computational perspective

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ACS Fall 2022

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