Fe3S4/persulfate-based pre-oxidation for mitigating membrane fouling and enhancing synergistic perfluorooctanoic acid removal: Influence of pH and persulfate types

Aerobic granular sludge membrane system (AGSMS) represents a new wastewater reuse treatment technology. However, the challenges of membrane fouling and limited micropollutant removal efficiency significantly impact its potential for further application. Consequently, this study aimed to address these concerns by employing Fe3S4/persulfate pretreatment to mitigate membrane fouling and enhance perfluorooctanoic acid (PFOA) removal in AGSMS. The effects of pH and persulfate types were investigated by assessing membrane flux, fouling resistance, membrane characterization, and effluent properties. Results showed that optimal mitigation of membrane fouling and removal of PFOA were achieved using Fe3S4-activated PMS at a pH of 6. The primary mechanism for Fe3S4-activated PMS involved the generation of SO4 center dot and 1O2. Moreover, the fouling mechanism transitioned from cake layer fouling and intermediate blocking fouling to complete blocking fouling in the presence of Fe3S4/PMS. The application of extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory revealed that at pH 6.0, there was a significant increase in the energy barrier for both foulant-membrane and foulant-foulant interactions, leading to an effective mitigation of membrane fouling. Correlation analysis demonstrated a significant influence of polysaccharides and total phosphorus concentration on mitigating membrane fouling. Furthermore, pH played a crucial role in mitigating membrane fouling as well as pollutant removal by influencing both coexisting ion states in solution and catalyst properties. This study offers valuable insights for future research and provides essential theoretical guidance for large-scale applications of AGSMS technology in wastewater treatment.