Oil spills and an increasing demand for the treatment of industrial oily wastewater are driving the need for continuous large-scale oil/water separation processes. Herein, we report a nanofibrous cellulosic membrane (NFC membrane) for the continuous high-flux separation of large amounts of oil/water mixtures. The NFC membrane was fabricated using wet electrospinning, a facile yet effective method for stacking nanofibrous membranes with uniform porous structures on a substrate. Owing to its cellulosic nature, the membrane showed excellent underwater superoleophobicity along with robust chemical stability and was able to separate oil/water mixtures at efficiencies exceeding 99%. Repetitive oil/water separations could be performed using a single membrane, during which the oil content in the filtrate remained extremely low (30 kPa) that allowed not only gravity-driven but also pressure-driven separation of oil/water mixtures. The separation flux reached 120 000 L m⁻² h⁻¹ during pressure-driven separations, which is a very promising feature for actual applications such as the large-scale treatment of industrial oily wastewater.

Stable superhydrophobic meshes with a biomimetic hierarchical structure were fabricated via simple electropolymerization and chemical polymerization processes. Because the multi-scale hierarchical structure provides a stable superhydrophobic state by maintaining a Cassie state, these meshes have high static and dynamic waterproof capabilities.