Enhanced mitigation of membrane fouling in AGMBR through the Fe3S4/PMS pre-oxidation system: The pivotal role of pH and its underlying mechanisms

In this study, an innovative ferric tetrasulfide/peroxymonosulfate (Fe 3 S 4 /PMS) pre-oxidation system was integrated into an aerobic granular membrane bioreactor (AGMBR) to alleviate membrane fouling. The role and underlying mechanisms associated with solution pH was also investigated. The results demonstrated that under optimal conditions (pH 6.0, 0.2 g/L Fe 3 S 4 , and 2.0 mM PMS), pre-oxidation treatment significantly reduced the total membrane fouling resistance by 98 % and shifted the fouling mechanism from cake layer fouling to pore blocking fouling. Moreover, pre-oxidation treatment at pH 6.0 enhanced the energy barrier between foulants-membrane and foulants-foulants, thereby alleviating membrane fouling. The key reactive oxygen species were identified as •OH, SO 4 • – , and 1 O 2 with contributions of 7.03 %, 46.62 %, and 22.38 %, respectively. Furthermore, phosphates significantly inhibited the performance of Fe 3 S 4 /PMS oxidation system for mitigating membrane fouling; however, decreasing solution pH alleviated this inhibition effect. Additionally, an inhibiting effect on coating metal oxide or hydroxide on catalyst surface was observed along with variation in surface charge properties of Fe 3 S 4 when pH was decreased to 6.0, which further promoted activation of PMS for mitigating membrane fouling. This study provides a robust theoretical foundation for employing Fe 3 S 4 /PMS pre-oxidation in AGMBR to alleviate membrane fouling issues which represents an important engineering advancement.