Assembly of MXene/ZnO heterojunction onto electrospun poly(arylene ether nitrile) fibrous membrane for favorable oil/water separation with high permeability and synergetic antifouling performance

Abstract

The two dimensional MXene nanosheets lamellar membranes have emerged as the promising candidates for oil/water separation. However, to deal with the large-scale discharge of complicated oily wastewater (including oils, organics, microorganism, etc), developing advanced membrane materials with high permeate flux and enhanced antifouling is still big challenge. Herein, the MXene/ZnO heterojunction was prepared by electrostatic attraction, which was modified by tannic acid (TA) and further self-assembled onto the poly (arylene ether nitrile) (PEN) fibrous mat to construct the multi-functional separation membrane (ZnO/M-TA@PEN fibrous composite membrane). In the hierarchical functional layer, the improved hydrophilicity of TA and the hierarchical micro-/nano-roughness build by ZnO NPs contributed to the super-hydrophilic/underwater super-oleophobic feature (WCA = 0°, UOCA>152°), leading to high separation efficiency and ultra-low oil adhesion. Uniquely, the decoration of ZnO NPs achieved the “intercalation effect” and effectively tuned the interlayer spacing between MXene nanosheets, which conquered the stacking problem of MXene nanosheets lamellar membrane and greatly enhanced the permeation flux of membrane. For separating various oil emulsions, the resulting ZnO/M-TA@PEN fibrous composite membrane displayed superior emulsion separation flux (1815.34 ± 44.73–2053.35 ± 42.62 L/m2·h) and separation efficiency (>99.4%), even in high-temperature and salty environments. More importantly, the heterojunction structure of MXene/ZnO hybrid endowed the fibrous composite membrane with enhanced antibacterial ability and photocatalytic self-cleaning performance toward the degradation of methylene blue, which realized the synergetic antifouling and favorable cycling ability of the fibrous composite membrane. This combination of anti-fouling and high permeability renders the membrane as attractive candidate for dealing with the oily wastewater containing multicomponent pollutants.