A Reverse Beetle-Like Nanofibrous Membrane with Hybrid Wettability for High-Efficiency Separation of Oil-in-Water Emulsions

Creating a feasible membrane for treating stable emulsion wastewater with submicrometer-sized oil-in-water droplets is significant but constrained by low efficiency and high energy consumption. Herein, an innovative reverse beetle-like nanofibrous membrane with hybrid wettability was first constructed by a nonsolvent-induced phase separation technique. The obtained membrane consists of hydrophobic/underwater oleophilic submicrometer-sized humps and a hydrophilic/underwater oleophobic nanofibrous substrate, which endows the membrane with excellent capacity for tiny oil droplet capture and fast water permeation. Benefiting from the fascinating hybrid wettability, this membrane can effectively separate various oil-in-water emulsions with submicron-sized droplets and demonstrated a promising separation efficiency (≥99.0%) and a high permeation flux (506 L m–2 h–1) even when driven by gravity (∼1 kPa). This work provides a promising approach to develop next-generation membranes integrating high separation efficiency and low energy consumption for oil–water separation.