Silanization enabled superhydrophobic PTFE membrane with antiwetting and antifouling properties for robust membrane distillation

A superhydrophobic polytetrafluoroethylene (PTFE) membrane (water contact angle 158 ± 5o) was fabricated based on a commercial microporous membrane by surface silanization and fluorination. The engineered PTFE membrane was characterized by various techniques, including scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, laser scanning confocal microscopy, a liquid-liquid porometer, water vapor permeation and contact angle measurements. The prepared PTFE membrane showed a slightly decreased average pore size of 0.37 μm, and thus an increased penetrating pressure of 0.38 MPa compared with the pristine commercial membrane. The developed superhydrophobic PTFE membrane had a very low surface energy of 1 mJ/m2, only one third of that of the unmodified commercial membrane. The characterization and membrane distillation (MD) separation results showed that the superhydrophobic PTFE membrane had significantly enhanced antiwetting and antifouling performances compared with the pristine commercial membrane. The developed new PTFE membrane also displayed excellent antifouling, antiwetting and long-term stability during the treatment of real challenging landfill leachate of high salinity and high organics by MD. The fabricated PTFE membrane with simultaneously antiwetting and antifouling properties opens a new avenue for treating challenging waste liquids via MD. This study also provides an important strategy to develop superhydrophobic simultaneously antiwetting and antifouling membranes for stable long-term MD applications.