Preparation of an omniphobic nanofiber membrane by the self-assembly of hydrophobic nanoparticles for membrane distillation

Abstract

An electrospun fiber membrane was prepared using polyamide 6 (PA6) to manufacture superhydrophobic and omniphobic nanofiber membranes for separation and purification processes that had excellent anti-fouling and anti-wetting performance. Trichloro(1H,1H,2H,2H-perfluorooctyl)silane (F-POSS) was used to treat the surface of PA6 with a fluorinated silane (F-silane) to impart a primary hydrophobic layer to the surface of the membrane. To enhance the hydrophobic properties of the membrane’s surface, a polyvinylidene fluoride (PVDF) coating solution was grafted to F-POSS to create PVDF-g-F-POSS. The PVDF-g-F-POSS agglomerated into nanoparticles on the membrane surface, which can decrease its wettability. As a result, the omniphobic property was improved, thereby modifying the contact angle between the feed solution and the membrane surface. In addition, by lowering the temperature sensitivity and surface tension of the liquid to improve its wetting retardation, the membrane could be used for membrane distillation. The contact angle of deionized water on the membrane was increased from 71° to 149° by the surface modification. The initial water flux was maintained for up to 20 cycles (162 h) due to the hydrophobicity of the membrane surface in the membrane distillation process. Ethylene glycol rejection of the omniphobic membrane was exhibited to be 100% for 200 h at 60 °C.