ZnO Nanorod Induced Omniphobic Polypropylene Membrane for Improved Antiwetting Performance in Membrane Distillation
Yurong Zhao, Xing Xing, Congbin Xu, Yali He, Yang Chen, Jianzhong Zheng, Zhiqiang Hu
Abstract
Maintaining hydrophobicity of the membrane in membrane distillation is vital for treating high-salinity feedwater containing surface active substances due to their wetting impact on the membrane. An effective approach to mitigate membrane wetting is to build rough nanostructures on a pristine membrane to render its surface omniphobic. Directly building nanostructures on polypropylene (PP), however, is challenging, as the material is chemically inert. In this study, a novel method was developed to physically plant ZnO seeds on the PP membrane above the material’s heat deflection temperature. A biomimetic nanostructure was then constructed on the membrane surface by growing fluorinated ZnO nanorods along the seeded PP substrate. The resulting omniphobic membrane exhibited a contact angle constantly above 160° against a test solution containing 50 g/L NaCl and 0.06 mM sodium dodecyl benzenesulfonate. Compared to the pristine PP membrane, the modified PP membrane showed a nearly complete salt rejection and much improved antiwetting capacity against the surfactant added in the test solution. The physical seeding method presented in this study is therefore a promising alternative approach to functionalize chemically inert polymeric substrates with constructed biomimetic nanostructures.