Superhydrophobic nanofiber membranes with 3D-network reinforced pore structure for membrane distillation

Abstract

Electrospun nanofiber membranes (ENMs) have garnered significant attention among researchers for membrane distillation (MD) in treating high-salinity wastewater due to their high water flux and low mass transfer resistance. However, a significant challenge in using ENMs for MD is membrane wetting, which results from the deformation of their weakly randomly overlaid nanofibers structure due to water flow shear forces. Herein, we focused on the membrane's structure and successfully prepared superhydrophobic nanofiber membranes with 3D-network reinforced pore structure by immersing PVDF ENMs in a mixed solution of polydimethylsiloxane (PDMS) and titanium dioxide nanoparticles (TNPs) after a hot-pressing treatment for impregnation and coating. The resulting membrane exhibits exceptional properties, including a high water contact angle (WCA) of 160.3°, a high liquid entry pressure (LEP) of 1.57 bar, and sustained structural integrity with an unchanged pore size distribution even after 5 h of water scouring. These characteristics contribute to a water flux of 39.3 kg·m−2·h−1 and an unexpectedly long durability of up to 102 h, along with an outstanding salt rejection exceeding 99.99 %. Moreover, the membrane demonstrates stable water flux and resistance to wetting when processing a 3.5 wt% NaCl solution containing 0.1 mM sodium dodecyl sulfate (SDS), underscoring its significant potential for MD applications.