Asymmetric Wettability Janus Mesh via Electrostatic Printing for Selective Oil–Water and Emulsion Separation

Abstract

Janus mesh with two-sided asymmetric wettability shows high potential for selective oil–water and emulsion separation. However, it remains a challenge to construct Janus mesh structures with good stability and extremely asymmetric wettability. Herein, a novel Janus mesh with asymmetric wettability was structured by two different precursors, polydimethylsiloxane/zinc oxide (PDMS/ZnO) and zinc oxide–polyacrylonitrile/N,N-dimethylformamide (ZnO–PAN/DMF), by electrostatic printing, including electrostatic air spraying and electrostatic spinning. The prepared Janus mesh has special micro–nanostructures on two sides, including PDMS@ZnO and ZnO@PAN. On the basis of gravity, when the placement direction is changed, Janus mesh can effectively separate oil–water mixtures of different densities and surfactant-stabilized oil–water emulsions. Meanwhile, the obtained Janus mesh exhibited good separation efficiency (>96.3%) for various oil–water mixtures, and the flux was up to 2621 ± 30 L m–2 h–1. The Janus mesh was cycled 20 times with no weakening in separation efficiency, indicating satisfactory cycling stability. The Janus mesh displayed good stability under harsh conditions (acidic, alkaline, and high temperature). The Janus mesh can realize low energy input and long-lasting oil–water separation, which has widespread application prospects in intelligent oil–water separation. This top-down electrostatic printing strategy provides a way to construct Janus interface materials with practical applications.