Facile preparation of durable superhydrophobic-superoleophilic mesh using simple chemical oxidation for oil-water separation under harsh conditions

Considering severe damage to environment and human beings caused by the increasing oily wastewater, much progress has been made toward applying superhydrophobic-superoleophilic meshes to various oil-water separation processes with high separation efficiency and flux, especially metallic meshes. However, previously reported methods to prepare superhydrophobic metallic meshes involved unfriendly spray emissions, poor robustness of mesh surface, or extra applied energy requirement. Additionally, most of such meshes utilized for oil-water separation lost their superhydrophobicity when exposed to hot water or strong corrosive solutions. Herein, a durable superhydrophobic stainless steel (SS) mesh was presented using a simple, cost-effective chemical oxidation for the gravitydriven separation of oil-water mixtures under harsh conditions. The irregular microscale bullet-hole-like pits covered with nanoscale villous textures that formed on the mesh wires and fluoroalkylsilane (FAS) molecules endowed such mesh with superhydrophobicity and superoleophilicity. And the separation of heavy or light oil-water mixtures with high separation efficiency and purity was realized using the as-prepared mesh. More importantly, this mesh exhibited good resistance to hot water or corrosive solutions, and was used for corresponding separation of dichloromethane and these harsh environmental liquids with separation efficiencies beyond 96.0%. Moreover, the as-prepared mesh still maintained a separation efficiency above 95.0% and stable reusability after 70 times of repeated separation, and its superhydrophobicity also remained even when exposed to air, immersed into extreme liquids or abraded. This durable superhydrophobic SS mesh developed in this work can be practically used as a highefficient functional mesh for the separation of oil-water mixtures under various harsh conditions.