Microstructure design and construction of anti-wetting and anti-fouling multifunctional Janus membrane for robust membrane distillation

• Theoretical relationship between wettability and microstructure was derived. • An anti-wetting and anti-fouling multifunctional Janus membrane was fabricated. • Membrane fouling and wetting propensity were evaluated via interaction force probe. • Janus membrane guaranteed a robust MD for SOPW hypersaline wastewater treatment. • The synergistic effect was crucial to Janus membrane outstanding MD performance. Membrane wetting and fouling were main restrictions for the industrial application of membrane distillation (MD), especially in the presence of surfactants or oily substances. Herein, a novel anti-wetting and anti-fouling multifunctional Janus membrane was designed by optimization of the size of reentrant structure and position of hydrophilic layer. The theoretical relationships between wettability and the microstructure of the Janus membrane was derived mathematically. A facile approach was applied for the dual-layer bioinspired membrane fabrication by a two-step electrospray strategy. The resultant composite structure presented high omniphobicity (water contact angle of omniphobic sub-surface was 159.3 ± 1.1°) and underwater superoleophobicity (underwater oil contact angle of hydrophilic top surface was 152.7 ± 0.5°). Meanwhile, the wettability of the fabricated Janus membrane kept robust in a broad pH range of 1–14. During continuous MD treatment for emulsified oily hypersaline solution, the Janus membrane exhibited stable permeate flux and salt rejection (around 100%). It was speculated that the hydration effect of hydrophilic top layer coupled with the cavitation and slip boundary effects of the reentrant structure might be the key reasons for the robust anti-wetting and anti-fouling performances. Significantly, this novel bioinspired Janus membrane was believed as a candidate for treating challenging wastewaters such as the shale oils produced-water, and also had high potential in paving the way for industrial application of MD.