Embedded interlocking membrane interface enables highly stable and water-permeable membrane distillation of hypersaline wastewater

The lack of robust distillation membranes to resist scaling/wetting remains a significant barrier to applying membrane distillation (MD) for hypersaline wastewater treatment. Constructing a functional surface layer was demonstrated to be a promising strategy against membrane scaling/wetting. However, conventional surface coating processes could increase water transport resistance and low compatibility between the surface layer and hydrophobic substrate, deteriorating membrane efficacies and stabilities. Herein, we successfully developed a surfactant-tailored PVDF/PVA composite membrane (SPCM) with a robust embedded interlocking structure. SPCM not only exhibited outstanding mechanical stabilities and anti-scaling/wetting capabilities during hypersaline wastewater treatment but also showed marvelous water permeability (exceeding the intrinsic permeability of hydrophobic substrate, ∼17 %). We systematically investigated the effect of surfactant integration on the microstructural evolution and operational efficacies of functional surface layers. Detailed mechanisms of water transport enhancement were revealed by instrument characterization and experimental design. The embedded structure of surface layer, which decreased the water transfer distance and enhanced the evaporation area at the gel-layer/hydrophobic-substrate interface, was demonstrated to be the key to water flux enhancement. Besides, the post-treatment could further optimize the chemical structure of hydrogel networks and increase the proportion of intermediate water (IW) at the evaporation interface, facilitating water evaporation. SPCM also demonstrates outstanding efficiency and stability in the long-term cycle concentration of desulfurization wastewater. The high mechanical stability and exceptional operational efficiency of the SPCM, combined with the simplified membrane preparation process, endowed the SPCM with tremendous application potential for hypersaline water treatment.