Development of a novel hydrophilic SiO2/PVDF Janus membrane via different modification methods for robust antiwetting and antifouling membrane distillation

The development of novel membrane distillation (MD) membranes with high resistance to wetting and fouling has a great importance for the treatment of surfactant or oil-containing wastewater. In this study, superwettable Janus membranes were produced using hydrophilic silica nanoparticles (SiO2 NPs) via blending phase inversion (M1), delayed phase inversion (M2), and spray coating (M3) methods. Scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM/EDS) and Fourier transform infrared spectrometry (FTIR) analysis showed that SiO2 NPs were successfully deposited on the top layers of the membranes, while no SiO2 NPs were detected on the bottom layers. Furthermore, underwater superoleophobic properties were achieved for M2 and M3 membranes, while M1 membrane showed a satisfactory underwater oleophobicity. In MD filtration tests, the M2 membrane exhibited the highest membrane wetting and fouling resistance, followed by the M1 membrane. However, the sprayed SiO2 NPs coating layer on the M3 membrane did not remain stable, resulting in a similar permeate water flux and rejection profiles to the pristine membrane after a short time. This study indicates that Janus membranes fabricated by blending and delayed phase inversion methods could be a strong candidate in MD for the treatment of complex wastewater containing surfactants and oil.