Fabrication of superhydrophobic PVDF membrane via catechol/polyamine co-deposition and SiO2 nanoparticles for membrane distillation

Due to the societal development and population growth, the crisis regarding fresh water resources has become increasingly prominent. As a membrane separation technology, Membrane distillation (MD) has emerged as a widely used in the recovery and utilization of fresh water. However, membrane wetting and membrane fouling have hindered the further application of MD. To address these challenges, this work provides a method for fabricating a superhydrophobic composite PVDF membrane using catechol(CA)/polyethyleneimine(PEI) co-deposition, sol-gel growth of SiO2 nanoparticles, and the grafting of long chain perfluorosilane. The surface average roughness of the superhydrophobic membrane was up to 113.04 nm under the optimum conditions. The contact angle of the modified membrane was up to 157.5°, and a sliding angle is 8.0°, confirming its conformity to the Cassie-Baxter model. In addition, the modified membrane not only improved fouling and wetting resistance but also maintained a water flux equivalent to that of the PVDF membrane membrane when treating feeds containing surfactant, organic pollutants, and high salinity. In conclusion, this study provides a simple and feasible method for preparing superhydrophobic modified membrane, which further improves the adaptability of MD process for complex feed systems.