Development of Robust Fluorinated SiO₂/PVDF Composite Hollow Fiber Membrane for Bromine Resources Recovery from Brine via Membrane Distillation

In this study, a superhydrophobic composite hollow fiber membrane consisting of a fluorinated silicification layer (fSiO₂) upon a poly(vinylidene fluoride) (PVDF) substrate was developed via in situ silicification integrated with surface hydrophobic modification for bromine resources recovery from brine via membrane distillation (MD). The re-entrant hierarchical structure was established via surface silicification, after which (1H,1H,2H,2H-heptadecafluorodecyl) silane was introduced to transfer the surface property to be hydrophobic by reducing the surface energy with long fluorinated chains. The resultant fSiO₂/PVDF composite membrane exhibited a superhydrophobic property with a water contact angle of 147°, which effectively prevents wetting when conducting MD, and performed a high permeating flux of 0.62 kg·m^-2·h^-1. In a long-term stability test of 10-day operation duration, the fSiO₂/PVDF composite membrane remained decent, with flux declines of 1.8% and 38.3% when treated by the aqueous bromine solution and real brine, respectively. This work sheds insight into the fabrication of novel inorganic/organic composite membranes for bromine resource extraction from brine.