Omniphobic PTFE based Hollow Fiber Membrane with ZnO Nanoparticles Deposition via Universal Spray Technique

This investigation aimed to enhance the hydrophobicity of a polytetrafluoroethylene (PTFE) hollow fiber membrane, transforming it into an omniphobic surface. This was achieved by coating the membrane with a mixture of zinc oxide nanoparticles (ZnO-NPs) and polyvinylidene fluoride-cohexafluoropropylene (PVDF-HFP) using the universal spray technique. The membrane's morphology and performance were evaluated based on the number of spray cycles, which influenced the coating thickness on the membrane surface. The spraying process was varied up to 4 cycles to determine the membrane with the most effective deposition of ZnO NPs in terms of water contact angle and liquid entry pressure (LEPw). Results indicated that the membrane spray-coated up to 4 cycles, denoted as PTFE-4, exhibited a rough hierarchical re-entrant morphology, imparting omniphobic characteristics. The optimized membrane demonstrated a high water contact angle of 170° and a liquid entry pressure of 2.6 bar. Fourier-transform infrared (FTIR) and energy dispersive analysis of X-rays (EDX) confirmed the successful chemical integration of ZnO NPs onto the commercial membrane. This research holds significance for the future of membrane distillation in treating wastewater containing low surface tension pollutants.