Robust reduced graphene oxide composite membranes for enhanced anti-wetting property in membrane distillation

The application of membrane distillation (MD) has been severely limited by membrane wetting, particularly when treating feed solutions having contaminants with low surface energy . Herein, inspired by the special anti-wetting properties of the graphene-based membrane, a simple and scalable approach has been developed to fabricate the anti-wetting composite membranes with a reduced graphene oxide (rGO) skin layer and a microporous polytetrafluoroethylene (PTFE) substrate. The anti-wetting mechanism of rGO was investigated using a quartz crystal microbalance with dissipation and also fluorescence microscope. The prepared rGO-PTFE composite membrane exhibited outstanding MD performance with high water flux of about 60 L·m −2  h −1 , excellent salt rejection (>99.9%) and robust anti-wetting properties when desalinating a 3.5 wt% NaCl feed solution with 0.8 mM sodium dodecyl sulfate (SDS) for 66 h at the temperature difference of 40 °C. Moreover, the rGO-PTFE composite membrane achieved an ultrahigh water flux of about 149 LMH and perfect salt rejection (100%) at a temperature difference of 60 °C, which is 1.2–3.5 times as high as the flux of the reported MD membranes. Our research provides a robust rGO composite membrane with high flux and anti-wetting properties in MD and offers some insightful understanding about the anti-wetting mechanism of rGO against SDS and water.