Construction of PP membranes with robust interfacial stability by ALD and fluorinated grafting for high salt solution distillation

In this work, PP-TSF superhydrophobic membrane was constructed by a triple layer on the PP membrane, containing titanium layer by atomic layer deposition, silica layer by sol-gel, and fluorine layer by chemical grafting. The titanium layer worked as a transition layer, increasing the binding stability between PP and the superhydrophobic layer, the silica layer provided more hydroxyl sites for superhydrophobic modification. Meanwhile, and the fluorine layer with low surface energy was the core of the superhydrophobic property. The microstructure, porosity, and pore diameter had no significant change after modification. The contact angle of the composite membrane was up to 158o, and the rolling angle was less than 10o. The hydrophobicity, self-cleaning properties, and surface roughness are significantly improved after modification. The salt retention of the high salt (15 wt%) was consistently higher than 99 % during the 21-h vacuum membrane distillation experiment.