Amphiphobic electrospun PTFE nanofibrous membranes for robust membrane distillation process

Membrane distillation (MD) has been identified as a promising technology to desalinate the saline wastewater owing to its unique advantages including its ability in treating hypersaline solutions, 100% (theoretical) solute rejection and mild operating conditions. However, polytetrafluoroethylene (PTFE) hydrophobic membranes used for MD process were prone to be wetted caused by fouling due to the amphiphilic organics in feed solution. Herein, we developed an effective approach to fabricate amphiphobic PTFE nanofibrous membrane with enhanced anti-wetting and anti-fouling. During which, polyacrylonitrile (PAN) fiber was co-electrospun into PTFE/PVA precursor membrane, and Stober method was adopted for in-situ growing of SiO2 nanoparticles (SiNPs). After sintering, the SiNPs were fixed on the surface of PAN and PTFE fibers through chemical bonds and adhesive forces, respectively, which constructed membrane surface micro/nano structure. And then, the trimethoxy (1H,1H,2H,2H-heptadecafluorodecyl) silane (17-FAS) was used to fluorinate SiNPs. The prepared PTFE membrane exhibited strong amphiphobicity with water contact angle of 166.9 degrees and oil contact angle of 134.5 degrees. The amphiphobic PTFE membranes behaved a stable flux and excellent salt rejection during the 24h MD experiment in treating hypersaline solution, saline containing surfactant and oily saline. Also, the membranes showed excellent stability and reusability in the three cycles test, showing good application prospect in MD process, especially in the harsh environment.