Discerning the roles of various reactive oxygen species on PFOA degradation

Abstract Perfluorooctanoic acid (PFOA) is a widely distributed persistent organic pollutant in the environment. In recent years, various advanced oxidation processes (AOP) have been explored to degrade PFOA in aqueous solution, but the roles of reactive oxygen species (ROS) such as hydroxyl radical (·OH), superoxide anion radical (O 2 · − ), and hydroperoxide anion (HO 2 − ) on PFOA degradation were not clear or with even controversial conclusions. Here, we investigated three AOP systems, including the catalytic hydrogen peroxide process, the electro-Fenton system, and the anodic oxidation process, capable of producing different ROS, for PFOA degradation. Essentially no fluoride ion was detected after the reaction if only homogeneous free ·OH, O 2 · − , and HO 2 − were present in the system indicating their ineffectiveness in PFOA degradation. Further experiments demonstrated that valence band holes (h + ) and adsorbed hydroxyl radicals (·OH) on the anode surface governed the electrochemical mineralization of PFOA. In addition, the simultaneous TOC removal and defluorination by anodic oxidation degradation using a boron-doped diamond (BDD) electrode implied that the intermediates of PFOA degradation were rapidly decomposed on the electrode surface. This research provides insights on the role of ROS during PFOA degradation by AOP technologies.