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

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 164o against water and 113o against oil, as well as a low sliding angle of 4.3o, 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.