2D nanoneedle-like ZnO/SiO2 Janus membrane with asymmetric wettability for highly efficient separation of various oil/water mixtures

Abstract

The offshore oil spills and the discharge of oily wastewater are not only doing harm to the economy but also disrupting our aquatic and biotic environment. In order to alleviate this serious situation, researchers have developed super-wettability membranes to achieve efficient oil-water separation. Among them, asymmetric wettability Janus membranes with unique selective permeable properties have received widespread attention. However, utilizing a facile and environment-friendly method to endow a material with Janus super wettability to realize high oil-water separation efficiency and selectivity is still a challenge. Herein, a low-cost strategy is used to electrodeposit flake Zn on the copper mesh. Super-hydrophilic ZnO can be grown on it by a simple hydrothermal method, and then the Janus membrane with asymmetric wettability can be obtained by spraying SiO2 and octadecanethiol modification. It is worth noting that at a suction pressure of 4 kPa, the separation efficiency of the light oil-water mixture can reach more than 99.99%, and the flux is up to 13067.5 L·m-2·h-1. Under the action of gravity, the separation efficiency of the heavy oil-water mixture can reach more than 99.80%, and the flux is about 2000 L·m-2·h-1. Undoubtedly, the Janus membrane can simplify the operation to achieve on-demand oil-water separation. Last but not least, it can still maintain good performance after acid-base corrosion, wear, and cyclic tests, thereby showing broad potential in the field of oil-water separation and environmental protection.