High-conductivity microfiltration membranes incorporated with ionic liquids and their superior anti-fouling effectiveness

Abstract

Electric membrane bioreactor (E-MBR) for wastewater treatment and water purification has attracted significant interest due to its remarkable performance in fouling mitigation. The performance is much relevant to the electric and physicochemical properties of the conductive membranes in E-MBR. This study proposed a facile method to prepare a conductive membrane with low electrical resistance and enhanced hydrophilicity. Oxidative polymerization of pyrrole doping with ionic liquids was conducted on the surface of polyvinylidene fluoride (PVDF) membranes. Among the studied ionic liquids, 1-butyl-3-vinylimidazolium tetrafluoroborate (BVIMBF4) was the most suitable in this work. The electrical resistance of the PVDF membrane modified by pyrrole and BVIMBF4 (PPy-BVIMBF4/PVDF membrane) was as low as 9.76 Ω/sq, and its water contact angle reduced from 81° to 45°. In the fast-filtration tests, these conductive microfiltration membranes exhibited high rejections of Cu2+ ions (~85%) and Ni+ ions (~65%) and enhanced antifouling performance during the bovine serum albumin filtration with the application of an electric field. A long-term E-MBR operation demonstrated that the transmembrane pressure (TMP) rise and the flux decline of the PPy-BVIMBF4/PVDF membrane were significantly alleviated due to its improved conductivity and hydrophilicity. Its total membrane resistance for water transport was only 27% of the base PVDF membranes under a minute electric field of 0.8 V/m. Overall, the incorporation of ionic liquids in the oxidative polymerization of pyrrole offers a novel and effective strategy in conductive membrane fabrication and serves as an excellent method in fouling mitigation in MBR.