Effect of templating agents on the properties and membrane distillation performance of TiO2-coated PVDF membranes

Porous polyvinylidene fluoride membranes were coated with TiO2 and 1H,1H,2H,2H-perfluorododecyltrichlorosilane (FTCS) to create superhydrophobic surfaces for membrane distillation. The effect of the templating agents used in the sol-gel for TiO2 deposition was investigated. Results indicated that the use of a templating agent resulted in porous, multi-level microstructures. The final microstructure, nanostructure, wettability and desalination performance of the membranes were affected by both the physical and chemical properties of the templating agent. Coatings which did not use a templating agent resulted in greater deposition of TiO2, but lacked the hierarchical structure of their templated counterparts, leading to lower overall hydrophobicity. All modified membranes displayed a significant improvement in salt rejection, indicating a substantial reduction in pore wetting. Membranes templated with polyethylene glycol were found to have the optimum properties for desalination via membrane distillation.