Tailoring pore size and interface of superhydrophobic nanofibrous membrane for robust scaling resistance and flux enhancement in membrane distillation

Electrospun nanofibrous membrane with ultrafine nanofibers, high porosity, and interconnected pores has attracted significant attention in high-flux membrane distillation (MD). However, the comparatively large pore size and low liquid entry pressure (LEP) of nanofibrous membranes often result in severe membrane scaling and wetting. In this work, superhydrophobic nanofibrous membranes with tailored membrane pore size and interface were successfully fabricated via sequential electrospinning and electrospraying approaches. Results revealed that the decreased membrane pore size and increased interface evaporation area could synchronously mitigate membrane scaling and improve water flux. Besides, the water recovery of the membrane could be further increased with the aid of antiscalant, e.g., polymer polyacrylic acid, toward treating a nearly saturated gypsum solution. The excellent concentration performance was attributed to the cooperation of the antiscalant that inhibits the nuclei formation and the engineered surface that reduced the adhesion between the membrane interface and gypsum crystals. Notably, the resultant membrane also showed a high initial flux of ∼40 L m−2 h−1 and high salts rejection efficiency of ∼100% in a continuous concentration process for over 100 h. Our study provides a promising methodology for preparing novel membrane surfaces to treat hypersaline wastewaters meeting the minimal/zero liquid charge target.