Structural integrated hydrophilic-omniphobic Janus membrane by synchronous fluorination/reverse interfacial polymerization for durable membrane distillation

Traditional hydrophobic membranes are susceptible to membrane fouling and wetting of membrane pores, limiting the application of membrane distillation (MD) technology in water recovery under increasingly complex water conditions. To address these challenges, we designed a structural integrated hydrophilic-omniphobic Janus membrane via synchronous fluorination/reverse interfacial polymerization (SF/R-IP) based on roughening modified polyvinylidene fluoride (PVDF) nanofibrous membrane. During the SF/R-IP process, not only piperazine (PIP) from the upper aqueous phase solution reacted with trimethylchloroform (TMC) from the lower organic phase solution to form polyamide layer (PA) through IP reaction, the modified PVDF substrate would also be fluorinated synchronously by 1H,1H,2H,2H-perfluorotriethoxysilane (PFDTES) in organic phase. As a consequence, a novel Janus membrane with an ultrathin hydrophilic PA surface layer partially inter-embedded onto an omniphobic substrate was featured, and this special inter-embedding adhesion endowed the Janus membrane excellent structural integrity. The optimized Janus membrane combined the anti-wetting performance of an omniphobic membrane with the oil contamination resistance of the hydrophilic layer and the high permeability of nanofibrous substrate, demonstrating considerable vapor flux (31.1 kg m −2  h −1 ) and complete salt rejection (99.99%) during a long-term (80 h) DCMD experiments using surfactant sodium dodecyl sulfate (SDS)-stabilized oil-in-water (O/W) saline emulsion as the feed solution, and could fully recover optimal flux and continue stable operation after flushing. This study would provide a new strategy in designing high-performance MD membranes and enable robust applications of MD facing the challenges of membrane fouling and wetting.