Simplified and robust adhesive-free superhydrophobic SiO2-decorated PVDF membranes for efficient oil/water separation

A simplified adhesive-free strategy for fabricating robust superhydrophobic polyvinylidene fluoride (PVDF) oil/water separation membranes was developed. SiO2 nanoparticles were strongly fixed to the surface of the “adhesive” PVDF membranes via delayed phase inversion. Oil/water filtration membranes with micro–nano coarse structures and low surface energies were obtained by adjusting the SiO2 concentration in a coagulation bath. The membrane structure was analyzed via Fourier transform IR and X-ray photoelectron spectroscopy. The evolution of the morphology, performance of the membranes, and the filtration properties were investigated using scanning electron microscopy and confocal scanning microscopy, among other techniques. The obtained SiO2-nanoparticle decorated PVDF membrane has a water contact angle of 157 ± 2° and an oil contact angle of 0 °. The superhydrophobic PVDF membranes had extremely high chloroform fluxes, over 10,000 L/(m2 h) at 0.9 bar, and could be used for the separation of oil–water mixtures and surfactant-stabilized water-in-oil emulsions. The separation efficiency (approximately 99.95% in terms of the oil purity in the filtrate) was high. Furthermore, the fabricated PVDF oil/water filtration membranes exhibited good stability and excellent recyclability (over 20 cycles). The proposed eco-friendly and straightforward strategy provides new insights for the development of practical oil/water filtration membranes.