A 3D Janus stainless steel mesh bed with high efficiency and flux for on-demand oil-in-water and water-in-oil emulsion separation

Abstract

Janus materials with asymmetric wettability have attracted wide attention in oil/water separation due to the ability to remove water or oil on demand. In this work, a Janus stainless steel mesh (SSM) combining superhydrophilicity and high hydrophobicity was prepared through in-situ growth of polydopamine (PDA) and SiO2, phase interface deposition of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (PFOTS) on one side and floating deposition of polydopamine/polyethyleneimine (PDA/PEI) on the other side. Relying on the unidirectional water transportation ability, the Janus SSM could efficiently separate light/heavy oil/water mixtures on demand with a water removal rate of 7000 L·m−2·h−1 and an oil removal rate of 46,000 L·m−2·h−1. Based on this, a three-dimensional (3D) Janus SSM bed was designed by controllable assembling single piece of Janus SSM and 20 pieces of superhydrophilic SSM with in situ grown PDA@SiO2 nanoparticles (PDA@SiO2 SSM). The 3D Janus SSM bed showed excellent emulsion separation ability due to its long irregular permeation channels to make emulsified liquid droplets continuously collide, agglomerate and demulsificate. For oil-in-water emulsion, the separation efficiency could reach 99.31% and the flux was higher than 2864 L·m−2·h−1. For water-in-oil emulsion, the separation efficiency was over 99.68% and the permeation flux could reach 7072 L·m−2·h−1. With these excellent performances, the 3D Janus SSM bed was believed to be able to bring important contributions to the modern industrial oil/water separation process.