Robust dual-layered omniphobic electrospun membrane with anti-wetting and anti-scaling functionalised for membrane distillation application

A robust dual-layer superhydrophobic and omniphobic electrospun nanofiber membrane was developed for membrane distillation application, especially with feed that contains surfactant and dissolved organic compounds. 1H, 1H, 2H, 2H-Perfluomoctyltriethoxysilane (FAS) functionalising of the electmspun polyvinylidene fluoride-co-hexafluoropropylene (E-PVDF-HFP) membrane, followed by surface grafting with FAS-functionalised zinc oxide (ZnO) nanoparticles, achieved low membrane water sliding angle with re-entrant morphologies on the membrane surface. Field-emission scanning electron microscopy with energy-dispersive X-ray images revealed the regular and uniform formation of re-entrant structures due to the ZnO nanoparticles. The optimised 25% w/w ZnO (ePFP-25Z) membrane achieved the highest contact angles for water (>161 degrees), oil (131.5 degrees +/- 1.8 degrees) and ethanol (131 degrees +/- 2.9 degrees), had the lowest surface energy (0.75 +/- 0.43 mN m(-1)) and high surface roughness (3.26 mu m). The ePFP-25Z membrane maintained a stable membrane distillate flux and salt rejection (>99.9%) even after 80 h operation with 0.1 mM sodium dodecyl sulphate in super-saline solution (1 M NaCl). Anti-scaling and anti-wetting properties were illustrated in the presence of the dissolved organic compounds humic acid and alginate in super-saline feed.

Automated summary

A robust dual-layer superhydrophobic and omniphobic electrospun nanofiber membrane was developed for membrane distillation application, showcasing excellent anti-scaling and anti-wetting properties even in the presence of surfactants and dissolved organic compounds. Surface modification with perfluorinated silane and zinc oxide nanoparticles contributed to the high contact angles for water, oil, and ethanol, as well as maintaining stable membrane distillate flux and salt rejection under harsh conditions.