Robust Citric Acid-Crosslinked PVA/PVDF Janus Membranes for Membrane Distillation

Membrane distillation (MD) is a promising desalination technique. However, commercial membranes usually suffer from wetting and fouling issues, which hinder their wide applications. In this study, we coat a polyvinylidene fluoride (PVDF) membrane with a hydrophilic polyvinyl alcohol (PVA) and a citric acid (CA) mixed layer to fabricate PVA-CA/PVDF Janus membranes. A polydopamine (PDA) layer is used to enhance the adhesion between the PVA-CA layer and the PVDF membrane. Compared with the pristine PVDF membrane, the PVA-CA/PVDF Janus membrane shows excellent anti-wetting and anti-fouling performance without sacrificing water flux, significantly enhancing the efficiency of MD processes. The anti-wetting capacity of the Janus membrane stems from the rejection of surfactants through size exclusion and high liquid entry pressure by the PVA-CA layer. Its anti-fouling property is attributed to underwater superoleophobicity of the PVA-CA layer. Furthermore, the PVA-CA/PVDF Janus membrane exhibits superior performance in desalinating natural seawater and treating artificial industrial wastewater, demonstrating its remarkable versatility. The Janus membrane developed in this work shows great potential for applications in MD and wastewater treatment. Highlights Fabrication of robust PVA-CA/PVDF Janus membranes featuring a hydrophilic PVA-CA layer and a hydrophobic PVDF layer. PVA-CA/PVDF Janus membranes show strong resistance to wetting and fouling for membrane distillation. PVA-CA/PVDF Janus membranes enable long-term and efficient treatment of seawater and artificial industrial wastewater.