Mitigation of natural organic matter fouling of electrified membranes by pre-coagulation strategies to improve bisphenol A treatment performance

Membrane fouling is one of the issues that hinder the widespread application of electrified membranes. This study focuses on mitigating membrane fouling caused by natural organic matter (NOM) through pre-coagulation techniques. The effectiveness of pre-coagulation was evaluated based on the flux and removal efficiency of electrified membranes. Pre-coagulation can remove a portion of NOM and reduce the negative surface charge of residual NOM, thereby reducing the attachment of NOM to the surface of electrified membranes. As a result, pre-coagulation effectively increased the flux of electrified membranes for treating water samples containing NOM. Additionally, pre-coagulation alleviated the decrease in surface current density of electrified membranes caused by NOM pollution, leading to improved bisphenol A (BPA) removal performance. The effectiveness of pre-coagulation in enhancing membrane performance depends on the choice of coagulant. Compared to polyferric chloride (PFC), PFC-cationic polyacrylamide composite coagulants (PFC-CPAM) facilitated the aggregation of NOM into larger flocs with a branched structure, demonstrating a stronger capability to mitigate membrane fouling. However, it should be noted that the presence of CPAM may result in irreversible internal fouling due to the polarization effect induced by the electric field. Moreover, when the weight ratio of PFC to CPAM was 1:1, the flocs became overly dense, resulting in reduced flux. This study provides valuable insights for the application of pre-coagulation techniques in mitigating fouling issues in electrified membranes.