Nano-structure construction of porous membranes by depositing nanoparticles for enhanced surface wettability

Two-dimensional nano-structures are successfully constructed on the pore surfaces of porous membranes by depositing nanoparticles for enhanced surface wettability in this study, in order to obtain improved oil–water separation performance of membranes. Shirasu porous glass (SPG) membranes are used as the substrate membranes, and the two-dimensional nano-structures are constructed by depositing SiO2 nanoparticles onto the membrane pore surfaces, with which the smooth membrane surfaces turn into nano-structured concavo-convex rough surfaces. Chlorotrimethylsilane (CTMS) are grafted on the nano-structured membranes to achieve the membrane surface hydrophobicity and oleophilicity, while perfluorinated surfactants (f-PEG) are grafted on the membranes to achieve the surface hydrophilicity and oleophobicity. The formation and microstructures of the prepared membranes are investigated by employing scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS), and the relationship between the two-dimensional nano-structures and the surface wettability is explored by measuring the water/oil contact angle of membranes. The results show that, the SiO2 nanoparticles are uniformly and compactly deposited on the membrane pore surfaces, and the nano-structured architectures on the membrane surfaces could efficiently enhance the surface wettability of both CTMS-grafted and f-PEG-grafted membranes. Both CTMS-grafted and f-PEG-grafted nano-structured SPG membranes exhibit satisfactory performance of oil–water separation including separation of O/W emulsions. The results provide valuable guidance for designing and fabricating efficient membranes for oil–water separation.