Design of photocatalytic self-cleaning poly (arylene ether nitrile)/nitrogen-doped Bi2O2CO3 composite membrane for emulsified oily wastewater purification

Abstract

Membrane separation technique offers unique advantages for treating the emulsified oily wastewater with the oil droplet diameter less than 20 µm. However, the complicated membrane fouling originating from oils and soluble matters pose the huge challenges to membrane separation technique, which has stimulated the development of advanced membrane materials. Herein, we reported the photocatalytic and super-wetting poly (arylene ether nitrile) (PEN) fibrous composite membrane with high permeability and enhanced anti-fouling ability. The nitrogen-doped Bi2O2CO3 (N-Bi2O2CO3) was prepared by low-temperature chemical modification method and modified by dopamine (DA)-polyethyleneimine (PEI), which was further self-assembled on porous PEN support backbone. The hydrophilicity provided by the cross-linking reaction between PDA and PEI and micro-/nano- rough surface constructed by the flower-like N-Bi2O2CO3 contributed to the super wetting properties (WCA=0°, UOCA>150°), which imparted the membrane with ultra-low oil adhesion. In particular, the arrangement of flower-like N-Bi2O2CO3 effectively regulated the water channel of membrane, further increasing the permeate flux. Therefore, the fibrous composite membranes showed superior separation flux (632.79–762.81 L·m−2·h−1) and separation efficiency (>99.16%) for various oil-in-water emulsions, even under harsh conditions (90 ℃ and 2 M NaCl solution). More importantly, the N-Bi2O2CO3 rendered the membrane excellent degradation rates for various dyes (MO: 95.53%, MeB: 96.40%, CV: 96.45%, CR: 87.14%), achieving favorable photocatalytic self-cleaning ability. This work opens an alternative strategy to fabricate fibrous composite membrane with synergistically enhanced anti-fouling for the treating complicated emulsified oily wastewater in petrochemical industry.