Scalable fabrication of a robust asymmetric superwetting Janus mesh by facile spray-coating for oil–water emulsions separation

Abstract

Janus membrane with asymmetric wettability are emerging separation materials for the purification of emulsified oil–water mixtures, however, their poor mechanical durability and low-flux without external pressure severely limit their practical application. Herein, a robust superwetting Janus mesh demonstrating a high water contact angle (WCA) difference up to 157° was developed by simply spraying on the stainless steel mesh (SSM), via the superhydrophobic fluorocarbon resin/polyvinylidene fluoride/1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane modified titanium dioxide@carboxylated CNTs (FEVE/PVDF/F-TiO2@CNTs) layer and a superhydrophilic layer consisting epoxy resin/ethylene imine polymer/sodium perfluorooctanoate modified bentonite (EP/PEI/F-Bentonite). By carefully adjusting the surface polar-nonpolar molecule repulsion based on the two oppositely bond energy side and incorporating nano/microstructures to form a stable interfacial oiling/hydration layer, the robust Janus mesh achieved interface demulsification and gravity separation of emulsified oil–water mixtures. The prepared Janus SSM exhibited excellent gravity-driven separation performance, achieving a flux up to 1508.6 L m−2h−1 for water-in-oil (W/O) emulsions, and 843.1 L m−2h−1 for oil-in-water (O/W) emulsions. Additionally, it exhibited high separation efficiency with water rejection above 99.9 % and oil rejection above 99.7 %. Moreover, the prepared Janus mesh with fine uniform nano/microstructures and functionalized groups demonstrated notable reusability and mechanochemical stability after 10 cycles of O/W and W/O emulsion filtration, 100 cycles of sandpaper abrasion, and strong acid/alkali immersion for 7 d. Overall, this study expected to facilitate the fabrication of a robust asymmetric superwetting Janus mesh with enhanced separation properties for highly efficient oily wastewater treatment.