Robust Zwitterionic Poly(imidazolium)-Coated PVDF Membrane for Oily Water Treatment with Antibacterial and Anti-Biofouling Performances

Abstract

Membrane fouling remains a major challenge during oily wastewater purification, resulting in reduced water flux and separation efficiency. Zwitterionic polymers have been introduced to the PVDF membrane and shown their fouling resistance ability. However, most current zwitterions lack bactericidal effects and tend to be fouled by the attachment of bacteria and biofilm formation in long-term service. Herein, a synthetic zwitterionic poly(imidazolium), poly(ZIM-co-VTS), was introduced onto the PVDF membrane by co-assembly with polydopamine (PDA) and tetraethyl orthosilicate (TEOS) as a silica source. The in situ covalent bond can be formed between the catechol from PDA and silanol groups from both TEOS and imidazole-based polymers. Further, Fe3+ cross-linking contributes to the robust chemical stability of modified PVDF. The as-prepared coating exhibits superhydrophilicity and underwater superoleophobicity under harsh conditions (pH = 1 and 13), remaining high separation efficiency (>99%) toward various surfactant-stabilized oil-in-water emulsions without an apparent water flux (>1013 L m–2 h–1 bar–1) decline. More importantly, the cationic imidazolium in poly(ZIM-co-VTS) endues the excellent bacterial killing efficiency toward Staphylococcus aureus (4.5 log10 reduction) and Escherichia coli (4.7 log10 reduction). The zwitterionic poly(imidazolium)-modified PVDF exhibited long-term durability with anti-biofouling properties and was a promising candidate for practical oily wastewater remediation.