PVDF-interlayered Janus PTFE membrane for anti-wetting/fouling membrane distillation

Membrane distillation (MD) holds promise for treating high-salinity wastewater due to its salt tolerance and high rejection efficiency. However, membrane wetting and fouling severely impede its practical application. To address these challenges, this study proposes a strategy for fabricating a Janus PTFE membrane by introducing a PVDF interlayer, which enables stable unilateral hydrophilic modification of the superhydrophobic electrospun PTFE nanofibrous substrate. The key aspect of this design lies in the significantly enhanced adhesion between the low-surface-energy PTFE substrate and the hydrophilic TA-APTES-TEOS coating, achieved through the molecular compatibility of the PVDF interlayer. The designed Janus membrane represents a synergistic combination of the favorable porous structure of the PTFE substrate—which ensures high water vapor flux—and functional surface wettability, integrating the anti-wetting property of the superhydrophobic base with the anti-fouling capability of the underwater superoleophobic coating (UOCA 155°). This synergistic design conferred simultaneous anti-wetting and anti-fouling properties during MD operation. The resulting Janus membrane exhibited outstanding performance in treating hypersaline oily wastewater, maintaining a stable flux of 17.5 ± 0.5 kg·m⁻²·h⁻¹ and salt rejection exceeding 99.99 %. This work provides new insights for developing high performance PTFE membranes for MD applications.