Electrochemical degradation of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in water with persulfate catalyst support

• Ti/BDD anode is better than Ti/IrO 2 in PFOA & PFOS treatment using EC/PS process. • The removal efficiencies of PFOA and PFOS were 93.32 % and 94.93 %, respectively. • The treated water complied with US EPA standards for drinking water quality. • SO 4 − participated in the first stage of the PFOA degradation, while OH involved later. • The hydrolysis pathway contributed mainly to the decomposition of PFOA. The application of emerging technologies in the treatment of urgent pollutants such as per-/polyfluoroalkyl substances (PFAS), especially perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), has become a prominent trend. Though biological solutions have not yet brought about the expected efficiency and economic value, advanced oxidation processes (AOPs) like electrochemical oxidation with persulfate catalyst (EC/PS) have shown great promise. In order to shorten the time and improve the efficiency of pollution treatment, this study applied advanced optimization methods such as Plackett-Burman (6 factors, 12 runs) and response surface methodology with central composite design (RSM-CCD) (3 variables, 20 runs). The objective is to optimize the treatment of PFOA and PFOS in artificial wastewater by the EC/PS process, resulting in higher efficiency and more practical application. The PFOA and PFOS concentrations were measured on liquid chromatography tandem mass spectrometry (LC/MSMS) system. The treated water quality and degradation pathway of PFOA by the EC/PS method were also shown. The experimental results showed that Ti/BDD was highly optimized in the removal of PFOA and PFOS using the EC/PS method. With the optimal conditions and parameters including current density (CD) at 9.5 mA/cm 2 , NaCl concentration at 2 g/L, and persulfate (PS) concentration at 4.2 g/L, the treatment efficiency of PFOA and PFOS of the prediction equations reached 93.32 % and 94.93 %, respectively. The quality of the treated water with parameters of PFOA, PFOS, chlorine (Cl 2 ), fluoride (F − ) was lower than the maximum value according to the EPA drinking water regulations [1], thereby showing that the potential for applying this technology in practice is very large. In addition, the main degradation pathway of PFOA was also demonstrated through hydrolysis reaction when recording by-products such as C 7 F 15 H ( m / z 370) and perfluoroheptanoic acid (PFHpA) (C 6 F 13 COO − , m / z 363) during the entire 60 min experiment. In conclusion, the EC/PS process can be applied to water treatment with the ability to almost completely remove PFOA.