Bio-inspired robust superhydrophobic-superoleophilic polyphenylene sulfide membrane for efficient oil/water separation under highly acidic or alkaline conditions

The separation of water-in-oil emulsions in harsh environment (strong acid/alkali) is a challenging subject. In this study, we prepared a superhydrophobic-superoleophilic polyphenylene sulfide (PPS) membrane by the mixture of hydrophobic SiO2 nanoparticles, diphenyl ketone (DPK), benzoin (BZ) and PPS via thermally induced phase separation (TIPS) technology. This superhydrophobic membrane displayed a lotus leaf-like micro-nano structure, and it could be used for oil/water separation in strong acidic or alkaline environment. The hydrophobic SiO2 nanoparticles played a key role in the membrane structure evolution and its performance. When SiO2 content was 4 wt%, the pure water contact angle of the prepared superhydrophobic-superoleophilic membrane reached 156.9° and the oil contact angle achieved 0°. The fluxes of water-in-oil emulsions (kerosene, toluene and chloroform) reached 1926, 3150 and 3416 L/(m2·h), respectively. However, the fluxes of their surfactant-stabilized water-in-oil emulsions declined to 531, 685 and 724 L/(m2·h), respectively, due to the great stability of surfactant-stabilized emulsions. Most importantly, all the water rejection rates exceeded 99.9% when the PPS membranes modified with 4 wt% hydrophobic SiO2 nanoparticles. In addition, the PPS-SiO2 hybrid membranes exhibited excellent self-cleaning antifouling performance, cycling performance and superior acid/alkali resistance.