Biomimetic superhydrophobic membrane for membrane distillation with robust wetting and fouling resistance

Membrane distillation (MD) is a promising membrane-based thermal process capable of desalinating highly saline water. However, its application is limited by fouling and wetting of commercial hydrophobic membranes. Inspired by the lotus leaf, we developed a biomimetic superhydrophobic polyvinylidene fluoride (PVDF) membrane for robust MD via self-assembly method. The hierarchical micro-nanoscale texture on the membrane surface was constructed by grafting the spherical polyvinylsilsesquioxane (PVSQ) nanoparticles onto micronsized silica particles (SiPs). The membrane surface energy can be simultaneously lowered due to the hydrophobic groups including vinyls and methoxyls created from the condensation reaction of the vinyltrimethoxysilane (VTMOS). The resulting membrane showed a very high water contact angle (similar to 160 degrees) and a low water sliding angle (<15 degrees), demonstrating the strong hydrophobicity that is expected for a lotus-leaf-like surface. Compared to the commercial PVDF membrane, the fabricated superhydrophobic membrane exhibited superior resistance against wetting by a surfactant (sodium dodecyl sulfate) and fouling by humic acid during MD experiments. Our results suggest that biomimetic superhydrophobic membranes can enhance the operational robustness of MD and facilitate the efficient use of MD for desalinating saline wastewaters in favor of beneficial water reuse and resource recovery.