Tailored PVDF membrane with coordinated interfacial nano/micro-structure for enhanced membrane distillation

Abstract

Membrane distillation (MD) has attracted growing attention as a sustainable green membrane process technology for seawater and high saline water desalination, yet seriously challenged by the potential membrane wetting and fouling. Herein, a controllable approach to fabricate tailor-made MD membranes was proposed via combining in-situ growth of SiO2 nanoparticles with membrane surface activation and low surface energy substances. SiO2 nanoparticles distributed uniformly on the membrane surface and combined with the intrinsic microstructure of the membrane, a hybrid macro/micro-structure was constructed, further endowing the membrane with superhydrophobicity. The modified membranes exhibited excellent wetting-resistance properties and over 99.9 % salt rejection during vacuum membrane distillation (VMD) process. The surface wetting and anti-nucleation theory special for MD membranes was uncovered. This theory and VMD experiments synchronously indicated that the hybrid macro/micro structure with optimized nanoparticle size rendered the resulting fabricated membranes enhanced permeate flux and anti-fouling properties. The optimal L-F-3 membrane achieved high flux (16.08 kg/(m2·h)) under feed temperature of 60 °C with a water contact angle of 150° and LEP (liquid entry pressure) of 2.9 bar. Finally, the modified membranes possessed the enlarged effective evaporative surface and intensified the nucleation barrier as well as the interfacial nanoscale turbulent flow without potential scaling.