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

Abstract

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.