Superhydrophobic (polyvinylidene fluoride-co-hexafluoropropylene)/ (polystyrene) composite membrane via a novel hybrid electrospin-electrospray process

Abstract A novel hybrid electrospin-electrospray process was introduced to manipulate the membrane hierarchical structure towards enhanced surface superhydrophobicity and structural integrity. In this study, the two-nozzle mode was used to simultaneously electrospin PH (polyvinylidene fluoride-co-hexafluoropropylene) fibers and electrospray PS (polystyrene) beads to prepare a PH-PS composite membrane, during which fibers and beads alternatingly deposited and entangled together on the collector. Upon using the optimized PS solvent and PS content, the optimal PH-PS membrane exhibited superhydrophobicity (water contact angle of 157.6°) and good structural integrity, benefiting from the combination of the tough PH network and the interspersed porous irregular PS beads, as well as their homogeneous blending and good adhesion during this advantageous hybrid electrospin-electrospray process. In addition to superhydrophobicity, the PH-PS composite membrane was also endowed with a uniform pore distribution and high porosity, leading to a greatly enhanced liquid entry pressure of water (LEPw). Once applied in the direct contact membrane distillation (DCMD) process, it showed high desalination robustness and excellent anti-wetting performance with stable flux and high salt rejection under harsh feed conditions, providing great potential in practical desalination applications.