Electrochemical degradation of a C6-perfluoroalkyl substance (PFAS) using a simple activated carbon cathode

Abstract

This scoping study investigates the ability of an inexpensive, commercially available granular activated carbon (GAC) to sorb and conduct electrical charge to achieve reductive defluorination of a 6-carbon (C6) PFAS; (E)-perfluoro(4-methylpent-2-enoic acid) (PFMeUPA) as well as perfluorooctane sulfonic acid (PFOS). PFMeUPA is analogous to saturated, branched perfluorohexanoic acid. The results indicate PFMeUPA undergoes electrochemical reduction at an applied cell potential of 10 V in the absence of an electron shuttling catalyst, such as vitamin B₁₂, that is typically required for reductive defluorination reactions_. The rate of reduction was found to increase with decreasing reduction potential and increased temperature until −1.4 V vs. SHE. Less than 10% of the PFOS was reductively defluorinated, suggesting that more work is required to apply this technology for linear PFAS reduction. This is the first study to investigate the ability of a PFAS to undergo electrochemical reduction using an inexpensive GAC electrode in the absence of a catalyst or UV light. The results provide insight into the optimum conditions required for reductive defluorination of more recalcitrant PFAS, and ultimately have relevance to inexpensive, non-destructive on- or off-site treatment processes for PFAS-contaminated GAC.