Extremely asymmetric wettability, high wetting selectivity, instantaneous superwetting behaviors (low transmembrane resistance), and superior resistance to chemicals and solvents are needed for Janus membranes for switchable oil/water separation. However, it is still challenging to obtain Janus membranes with such properties. In this study, a surface with metastable hydrophobicity is constructed on one side of the chemically stable superhydrophilic TiO 2 @PPS membrane by adjusting the hydrophobization depth and the morphology of the hydrophobic layer via a water−oil interfacial grafting. The prepared Janus membrane exhibits a high water contact angle difference of ∼150°between its two surfaces with maintaining the superior penetrability of the original membrane, which makes it capable to separate both oil-in-water and waterin-oil emulsions with high fluxes and accuracy. The separation efficiency is higher than 98% for the separation of the two kinds of emulsions. The fluxes of the surfactant-free toluene-in-water and water-in-toluene emulsions are up to 6.4 × 10 2 and 9.5 × 10 2 L m −2 h −1 , respectively. Furthermore, the Janus membrane exhibits desirable antifouling performance and reusability during usage.

Separation of emulsified water/oil mixtures is a worldwide concern. However, poor chemical and solvent resistance of general polymeric membranes limit these membranes for application in the separation process. In this study, a poly(phenylene sulfide) (PPS) porous membrane with a rough concave topographic feature was fabricated, which exhibited excellent superoleophilicity and under-oil superhydrophobicity. The membrane is capable of separating both surfactant-free and surfactant-stabilized emulsions with a high flux. All of the water contents of the treated oils were below 300 ppm. The excellent water resistance property and cycling performance support the PPS membrane displaying an excellent reusability. Additionally, this PPS membrane was also certified to be used in strong solvents for a long time. In conclusion, the successful application of the thermally induced phase separation (TIPS) method may provide a new approach to fabricate the PPS membrane and improve its properties, and the application of the PPS membrane to separate water-in-oil emulsions is promising in practical applications.

The efficient treatment of oil–water emulsions in extreme environments, such as strongly acidic and alkaline media, remains a widespread concern. Poly­(phenylene sulfide) (PPS)-based porous membranes with excellent resistance to chemicals and solvents are promising for settling this challenge. However, the limited hydrophilicity and the poor hydrated ability of the hydrophilic PPS (h-PPS) membranes reported in the literature prevents them from separating oil–water emulsions with high efficiency, large fluxes, and good antifouling performances. In this study, a firm rough TiO2 layer is constructed on a h-PPS membrane via electrostatic assembly to improve the surface hydrophilization. The introduction of the TiO2 layer increases the wetting selectivity and decreases the oil adhesion, which makes it capable to efficiently treat oil-in-water emulsions (efficiency > 98%). Most importantly, the underwater critical oil intrusion pressure almost doubled after the incorporation of the TiO2 layer, which allows the membrane to withstand pressurized filtration, achieving a high flux of ∼4000 L m–2 h–1. This is more than 2 orders of magnitude larger than the flux of the reported h-PPS. Furthermore, the TiO2@h-PPS membrane displays long-term stability in separating oil–water emulsions in strong acid and strong alkali, showing a promising prospect for the treatment of strongly corrosive emulsions.

No abstract