Investigating the effect of polarity reversal of the applied current on electrochemical degradation of per-and polyfluoroalkyl substances

Advanced electrochemical oxidation methods have demonstrated significant potential in degrading per- and polyfluoroalkyl substances (PFAS). However, the widespread application of these techniques is impeded by the long term performance and the limited service life of electrodes. This study introduces a novel approach by investigating the impact of polarity reversal (PR) of the applied current on the electrochemical degradation of perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), 6:2 fluorotelomer sulfonate (6:2 F TS), and aqueous film-forming foam (AFFF) samples. A laboratory-scale electrochemical cell equipped with two titanium sub-oxide (Ti₄O₇) electrodes is used for the experimental investigation. The results indicate 6-h direct current (DC) operation causes fouling and ageing of the electrode (anode) such as the formation of titanium oxide (TiO₂). The application of PR effectively mitigates fouling and aging, leading to an enhanced mass transfer and an improved long-term defluorination of PFOA, PFOS, 6:2 FTS, and AFFF samples. The investigation also suggests that PR can help to reduce the energy consumption by ∼13%. Overall, the application of PR emerges as a promising and practical strategy to augment the electrochemical degradation of PFAS, addressing critical issues related to electrode stability and longevity.