Fabrication of Superhydrophobic Polyvinylidene Fluoride Composite Membrane via Mussel-Inspired Coating and -FeOOH Nanorods for Brine Treatment in Membrane Distillation

Membrane distillation (MD) is a low-grade heat-driven water treatment technology that possesses certain advantages in desalinating highly concentrated brine. However, the occurrence of membrane wetting and fouling problems limits its further development. In this study, by adopting polyphenolamine chemistry with synergistic nanoparticles, a polyvinylidene fluoride-modified membrane with superhydrophobicity was produced for membrane distillation. A catechol/polyethylenimine (CA/PEI) coating was first applied to the membrane surface using a deposition method, and then a rough micronanostructure was constructed superficially by beta-FeOOH nanorods, and finally a low-surface energy fluorosilane material was used for surface modification. This yielded a superhydrophobic membrane with a static water contact angle of 158.7(degrees) and a sliding angle of only 7.0(degrees). In treating the 35 g/L NaCl solution, the membrane flux of the modified membrane decreased only by 10.8% compared with the original membrane. When treating brine raw materials containing surfactants, oily substances, organic pollutants, and high concentrations of salts, the modified membrane flux was consistent, and the salt removal ratio was always higher than 99.99%, indicating its excellent resistance to wetting and pollution.