Validation of UV/persulfate as a PFAS treatment of industrial wastewater and environmental samples

Abstract

The contamination of natural water and industrial wastewater with per- and polyfluoroalkyl substances (PFAS) occurs globally. Thus, proper technologies are required to reduce PFAS in the environment and mitigate the adverse effects of these pollutants on human health and the environment. This study used a 23 full factorial design to evaluate the importance of operating factors including the level of persulfate (PS), the initial concentration of PFAS, and the time to the photochemical degradation of PFAS via ultraviolet irradiation at 185/254 nm assisted with persulfate (PS/UV method) in spiked solution. The method was then applied to break down PFAS in industrial wastewater, landfill leachate and groundwater samples using the highest factor levels applied in the 23 full factorial design. The results showed that the three investigated factors played an important role in the degradation of PFAS. The highest PFAS degradation was 57 % perfluorobutanoic acid (PFBA), 80 % perfluorooctanoic acid (PFOA) and 60 % perfluorooctane sulfonate (PFOS) using 10 mg L−1 PFAS, 5 g L−1 PS for 4 h. The defluorination also increased in the presence of PS but decreased in the presence of potassium hydrogen phthalate, nitrates, and chlorides. The PS/UV method decreased the concentration of PFAS in wastewater samples by 20–25 % PFOS and 13–15 % perfluorohexane sulfonate (PFHxS). PFAS degradation in wastewater improved with increasing treatment time. Under the PS/UV treatment, the degradation of major PFAS in groundwater was 94 % 6–2 FTS, 75 % PFOA, 62 % PFOS and 61 % PFHxS. The removal of major compounds in landfill leachate reached up to 12 % PFHxA, 32 % PFPeA, 56 % PFOA and 43 % PFOS. Our study indicated matrix effects leading to decreased PFAS degradation in different contaminated waters. The level of PS should also be controlled to an optimal value because higher levels led to a decrease in treatment efficiency.