Controllable Generation of Sulfate and Hydroxyl Radicals to Efficiently Degrade Perfluorooctanoic Acid in Cathode-Dominated Electrochemical Process

Sulfate radical-based advanced oxidation process (SO4•–-AOP) has been considered as a potential PFOA treatment option. The synergistic effect of SO4•– and hydroxyl radicals (HO•) favors the mineralization of PFOA. However, research regarding the optimal PFOA degradation pathway with controllable SO4•– and HO• is limited. Here, we proposed a cathode-mediated electrochemical process for efficiently removing PFOA through the in situ generation of SO4•– and HO•. Iron–nickel codoped carbon aerogel (FexNiC) were designed as cathode for synergistically activating peroxymonosulfonate (PMS) and oxygen (O2). Fe0.6NiC with optimized CSO4•- (0.385 mM) and CHO• (0.175 mM) exhibited high PFOA degradation efficiency (83.8%), TOC removal (75.9%), and defluorination rate (63.6%). DFT calculations and experimental studies confirmed that SO4•–-involved steps promote one-electron transfer from ionic C7F15COO– to SO4•–, and HO•-involved steps yield short-chain PFCAs. The actual application for pretreatment and deep-treatment of fluorochemical wastewater in the conventional treatment systems promoted the PFOA mineralization efficiency. It can be preferable to optimize the ratio of CSO4•- and CHO• in this cathode-mediated electrochemical process to rapidly and economically mineralize PFOA.