One-step preparation of efficient SiO2/PVDF membrane by sol-gel strategy for oil/water separation under harsh environments

The environmental pollution and resource loss caused by oil-water emulsion bring a severe threat to human's life. Superhydrophobic/superoleophilic membranes are considered as a wise choice for separating water-in-oil emulsions. However, the large-scale production of acid and alkali resistant, sustainable and efficient membranes remains an enormous challenge. In this study, a superhydrophobic/superoleophilic SiO 2 /PVDF (SP) membrane was prepared through facile sol-gel strategy in one step. Hydrophobic SiO 2 nanoparticles (NPs) were modified on PVDF membrane by hydrolysis and polycondensation reaction of tetraethyl orthosilicate (TEOS) and hexadecyltrimethoxysilane (HDTMS) as precursors. The low surface energy of the hydrophobic SiO 2 NPs and the micro/nano rough structures similar to the waxy protuberances of lotus leaves constructed by nano-SiO 2 played a crucial role in obtaining the superhydrophobic/superoleophilic property. The water contact angle (WCA) of the optimal SP membrane reached 152.4 ± 1.4°, while the oil droplets completely permeated the membrane in 1 s. Also, the fluxes of SP membrane for petroleum ether/water, n-hexane/water, and n-heptane/water were 3886 ± 140, 3551 ± 146 and 3763 ± 57 L m −2  h −1 , respectively, and the separation efficiencies were stable above 99.7%. Moreover, the SP membrane showed excellent separation effects and stability under different chemical environments. Most significantly, it also displayed anti-fouling performance like lotus leaves. The results indicated that its separation efficiency still remained above 97% after 20 cycles. Therefore, these outstanding results ensured the possibility of large-scale production and practical application of the SP membrane.