Preparation Janus membrane via polytetrafluoroethylene membrane modification for enhanced performance of vacuum membrane distillation desalination

In this study, we developed novel Janus membranes with multilevel hierarchical structures to prevent membrane pore wetting and enhance the performance for desalination simultaneously. Here, a Janus membrane with multilevel roughness was tailored via a polydopamine (PDA) coating followed by deposition of Fe3O4 nanoparticles and PDA sealing. These novel Janus membranes demonstrated outstanding antiwetting properties and salt rejection performances in comparison to pristine polytetrafluoroethylene (PTFE) membrane. Particularly, the specific flux of Janus membranes was maintained in a relatively stable state (0.6–0.7) after membrane cleaning with pure water, meanwhile, the permeate conductivity was maintained in the range of 0–30 µS/cm with the desalination rate of 99.9% during the vacuum membrane distillation (VMD) tests by using 6.98 wt.% feed solutions, indicating that these Janus membranes (i.e., P/Fe/P-PTFE membrane) can improve the performance for VMD desalination without membrane wetting throughout the test duration. Furthermore, we ascribed these Janus membranes’ superior performances to the coupled effects of super hydrophilicity brought about by PDA layer and self-healing mechanism provided by Fe3O4 nanoparticles. This work highlights the great potential of novel Janus membranes with multilevel hierarchical structures for water reclamation from challenging high-salinity wastewater through VMD.