Mussels-inspired design a multi-level micro/nano re-entrant structure amphiphobic PVDF membrane with robust anti-fouling for direct contact membrane distillation

Abstract

Membrane distillation has been widely used for effluent purification as a promising desalination technology, however, severe inorganic and organic fouling has typically hindered its practical large-scale application. In this study, we developed a facile strategy for fabricating an amphiphobic polyvinylidene fluoride(PVDF) membrane with a slippery surface. First, a bioinspired adhesive based on a polydopamine (PDA) layer is deposited on the membrane surface as an intermediate layer, providing an active anchor for nanoparticles (NPs). Subsequently, micro/nano SiO₂ particles were in-situ grown on the membrane surface using the sol-gel method to construct the re-entrant structure, which was then fluorinated with 17-chain fluorosilane (17-FAS). The intermediate layer inspired by dopamine polymerization significantly improved the stability of SiO₂ Nanoparticles. The amphiphobic membrane has a unique multi-level micro/nano re-entrant structure that provides a robust repellent ability against contaminants. The resultant amphiphobic membrane exhibited contact angles of 164^o against water and 113^o against oil, as well as a low sliding angle of 4.3^o, demonstrating excellent water and organic matter repellency. Although the initial flux of the amphiphobic membrane is lower than that of the pristine membrane. The amphiphobic membrane exhibited comprehensive anti-fouling and anti-wetting properties with steady flux and significant salt rejection in the desalination process when CaSO₄ and HA were added to the brine feed. This suggests that the modified amphiphobic membrane has a promising potential for long-term direct contact membrane distillation (DCMD) practical application.