Stable construction of superhydrophobic surface on polypropylene membrane via atomic layer deposition for high salt solution desalination

A facile and effective strategy, integrating atomic layer deposition (ALD) with photo-deposition, is developed to fabricate uniform a superhydrophobic surface on the membrane for high salt solution desalination. More specifically, a titanium interlayer was prepared by accurately controlled ALD on polypropylene (PP) microporous membrane, then a superhydrophobic modification was constructed on titanium interlayer by covalent silica deposition with nano silane emulsion (NMES). The ALD can uniformly coat an ultrathin TiO2 nanoparticle layer on the PP membrane surface by chemical adsorption, and photo-deposition assembles a stable composite layer reacting with TiO2 nanoparticles. It shows that the contact angle of the PP/TiO2-NMES composite membrane is higher than 150°, which exhibited an excellent anti-wetting capacity in high salt (15 wt%) vacuum membrane distillation. Moreover, the chemically stable bonding between the superhydrophobic layer and the PP membrane made the composite membrane to demonstrate its stability in long-term scaling experiments. Our work provides a viable bottom-up synthesis scheme to tailer and optimizes the inorganic layer on the inert polymeric surface.