A novel multifunctional photocatalytic membrane based on ternary heterojunction TiO2@PDA@BiOBr for biochemical oily wastewater purification

Membrane separation technology is a promising alternative for oily wastewater purification. However, developing membrane for the purification of biochemical oily wastewater is still challengeable. To this aim, a novel multifunctional photocatalytic membrane of PTPB-8 is fabricated by sequentially loading of TiO2, polydopamine (PDA), and BiOBr onto polyacrylonitrile (PAN) nanofibers in situ. PTPB-8 is of water contact angle (WCA) ∼ 0° and underwater oil contact angle (UOCA) 154.7 ± 2.5°, allowing it with outstanding separation and anti-fouling capability, and good reusability for emulsion separation under gravity (i.e., separation efficiency >90 %, permeation flux >300 L m-2h−1, and flux recovery rate >82 % for n-hexane-in-water emulsion after 15 cycles). Under simulated solar light, the ternary heterojunction TiO2@PDA@BiOBr is catalytically active with generating active species and the charge transfer pathway follows the mechanism of Z-type heterojunction. Consequently, PTPB-8 can kill E. coli and S. aureus by ∼ 100 % and degrade tetracycline by >90 %. The application trial results have demonstrated the great potential of PTPB-8 in the purification of biochemical oily wastewater containing bacteria and antibiotics. This study will also give a new idea for enhancing the photocatalytic activity of heterojunctions by PDA decoration.