Engineering multi-level structured electrospun nanofiber Janus membrane for direct contact membrane distillation

The membrane distillation (MD) has been considered as an attractive technique for the desalination and water treatments. However, the membrane with the superhydrophobic surface is still urgently needed for the wide application of MD process. Inspired by nature, the membranes with the highly porous structure have been fabricated by electrospinning to enhance the water vapor permeation in MD process. In this work, a hydrophobic layer with the hierarchical reentrant architecture was fabricated by electrostatically depositing silicon dioxide (SiO₂) nanoparticles on the surface of polyvinylidenefluoride electrosprayed layer followed by the fluorination treatment. The properties of hydrophobic layers were evaluated by varying the electrospraying time and SiO₂ loading amount. The optimal membrane had a water contact angle value of 145.7° and surface roughness of ∼275 nm, demonstrating a water flux of 21.2 L^.m^−2.h⁻¹ and superior salt rejection of >99.9 % when 3.5 wt% NaCl solution was used as the feed solution and the temperature difference was set as 40 °C. The membrane showed an excellent operation stability and effective mitigation in scaling and fouling tendency. The prepared membrane could be applied as a good candidate for the MD-based water treatment processes.