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.