Superhydrophobic-omniphobic membrane with anti-deformable pores for membrane distillation with excellent wetting resistance

Abstract

Wetting induced by salt-scaling and surfactants is the Achilles heel of membrane distillation, especially for concentration of high salinity wastewater. Herein, we rationally developed a membrane with robust wetting resistance by integrating superhydrophobic-omniphobic surface and anti-deformable pores into one system. The membrane was first developed by electrospinning, which was then modified with surface roughness, and followed by coating of polydimethylsiloxane to weld the intersecting fibers and fluoroalkylsilane to lower the membrane surface energy. The product exhibits excellent wetting resistance when concentrating the high salinity NaCl solution from 20 to 38 wt% (saturation condition), the simulated reverse osmosis concentrated water, the gypsum and the low-surface-tension high salinity wastewater. Moreover, the mechanism of membrane wetting resistance was also systematically discussed based on the experiment and computer simulation. It reveals that the superhydrophobic-omniphobic surface could stabilize the surface-bound air layer chemically, thus reducing the contact of crystals and surfactant with the membrane surface. Simultaneously, the anti-deformable pore also helps it overcome the asymmetrical hydraulic disturbance on enlarging membrane pore size, thus stabilizes the surface-bound air layer structurally. The presented development will provide a platform to understand and achieve wetting and scaling inhibition MD membrane for high salinity wastewater treatment.