Electrospun nanofiber membranes incorporating fluorosilane-coated TiO₂ nanocomposite for direct contact membrane distillation

The electrospinning technique as a method for fabricating hydrophobic membranes for membrane distillation (MD) has received much attention in recent times. In this study, TiO₂ functionalized with 1H,1H,2H,2H-perfluorooctyltriethoxysilane was added directly to the dope solution for electrospinning in order to increase the hydrophobicity of the resulting MD membranes. Three concentrations (10%, 15% and 20%) of polyvinylidene fluoride-co-hexafluoropropylene (PH) dope solution were used for electrospinning with various amounts of TiO₂ (1%, 5% and 10%) to generate nanofibers. The electrospun nanofiber membrane (ENM) of 20% PH with 10% TiO₂ exhibited the highest surface hydrophobicity (contact angle=149°) resulting from good dispersion of the TiO₂ particles, while the highest liquid entry pressure of 194.5 kPa was observed for the ENM comprising 10% PH with 10% TiO₂ due to its reduced pore sizes. Furthermore, the ENMs containing 10% TiO₂ exhibited better flux and stable salt rejection than commercial and ENMs without TiO₂. Notably, there was no severe wetting in the 20% PH ENM with 10% TiO₂ over seven days of operation, despite the high salt concentration (7.0 wt% NaCl) of the feed water.