Superhydrophobic wrinkled skin grown on polypropylene membranes enhances oil-water emulsions separation

It is urgent to explore new materials having high-efficiency separation performance for oil-water emulsions with low cost in the view of protecting environmental ecology. In this study, a facile procedure, consisting of the anchoring sites insertion tandem with wrinkled skin growth, was developed to manufacture a superhydrophobic wrinkled skin-covered polypropylene (PP) membranes through UV grafting and interfacial polymerization. The monomer octadecyltrichlorosilane (OTS) is immobilized on the amine-group anchoring sites on PP surface through covalent bonding, and the immobilized octadecyl tails facilitate the growth of superhydrophobic wrinkled skin, as characterized by FTIR, XPS and SEM, etc. Such wrinkled skin-covered structure improves the tortuosity of membrane and is beneficial for the membranes to contact with the emulsion fully and strengthen the demulsification effect. The prepared membrane shows superior water repellency and excellent separation performance for both immiscible oil-water mixtures and water-in-oil emulsions containing surfactant, with the retention rate of more than 99%. In addition, the wrinkled skin-covered PP membrane has good resistance to solvents and abrasion resistance due to the strong chemical bonding between the superhydrophobic structure and the PP membranes. Therefore, the newly proposed superhydrophobic wrinkled skin-covered PP membranes have promising practical applications in the field of oil-water separation.