Preparation of superhydrophobic PVDF composite membrane via catechol/polyamine co-deposition and Ag nanoparticles in-situ growth for membrane distillation

Membrane distillation (MD) has gained widespread attention in desalination and wastewater treatment. However, membrane fouling and membrane wetting seriously hinder its further development and industrial application. This work provides a method for preparing superhydrophobic modified membranes for MD through mussel-inspired coating, in-situ growth of nanoparticles and modification of low surface energy substances. The copolymerization of catechol and polyethyleneimine produced a poly(catechol/polyamine) layer rich in catechol groups and amino groups, which realized the in-situ reduction of silver nanoparticles and constructed a micro-nano rough structure. The resulting superhydrophobic modified membrane with an average roughness of 314.78 nm has a static water contact angle of 151.6 ± 2.5° and a sliding angle of 9.6°. The superhydrophobic membrane showed a membrane flux increase of more than 20% compared with the pristine PVDF and exhibited stable membrane flux and high salt rejection (>99.9%) when processing saline feeds containing surfactants, oily substances, organic pollutants and high concentration salts, indicating the excellent anti-wetting and anti-fouling properties. The superhydrophobic modified membrane prepared in this study improves the adaptability of the MD process and provides a promising candidate for membrane modification methods for MD.