Glomerulus Inspired Charged Nanofibrous Membrane for High-Efficient Micro/Nano-Emulsion Separation

Separating oil-in-water micro/nano-emulsions efficiently is a difficult task. Because of the wide droplet size distribution and high stability, superwetting membranes that utilize “size-sieving” separation mechanisms often face challenges to balance separation efficiency and flux, especially when dealing with nano-emulsions composed containing extremely small droplet sizes. In this study, a glomerulus-inspired multilayer nanofibrous membrane (GIM) is developed. The membrane is fabricated via sequential electrospinning with a gradient pore structure that gradually decreases from top to bottom. In addition, a hydrophilic surface coating with mixed charges is applied to the nanofibrous membrane, creating electrostatic interaction sites at the membrane interface that could interact with surfactants on the oil droplet surfaces. This process can promote droplet coalescence and accelerate demulsification. The glomerulus-inspired nanofibrous membrane can achieve efficient emulsion separation through stepwise coalescence and multi-level filtration. When GIM membranes separate emulsions across a wide droplet size range, the separation efficiency could be all larger than 99%, maintaining a higher separation flux at the same time. The separation flux could also be increases by approximately 2.5 times for conventional single-pore membranes. This emulsion separation strategy has provides an effective solution for the efficient treatment of industrial oily wastewater and broad application potential.