Switchable superlyophobic CoAl-layered double hydroxide (LDH)-based mesh membranes for separation of various oil/water systems and removal of soluble organic pollutants

Abstract

Switchable surface wettability has attracted tremendous attention owing to its potential applications, but it is still thorny to construct under-liquid dual superlyophobic surfaces for reversible separation of emulsified oil/water mixtures and treatment of complex oily wastewater. In this work, a CoAl-LDH-based mesh membrane was prepared for switchable separation of emulsified oily wastewater. The interpenetrating CoAl-LDH nanosheets were grown on the stainless steel mesh (SSM) forming a micro-/nano hierarchical structure via a hydrothermal method, which endows the membrane with under-liquid dual superlyophobicity. The obtained CoAl-LDH membrane exhibited switchable separation capability for both oil/water mixtures and oil/water emulsions with high fluxes and efficiencies (99.7%). In addition, the CoAl-LDH membrane could not only separate but also photodegrade the oil-in-water (O/W) emulsions containing soluble organic pollutants. Interestingly, after introducing a ZnO nanorod layer, the LDH/ZnO membrane exhibited progressive removal efficiency (99%) and photodegradation efficiency (＞99%) for methylene blue (MB). The cycled and harsh condition tests also confirmed the stability and robustness of the prepared membranes. The excellent separation performance and photocatalytic property endow the membranes appealing to practical oil/water separation and oily wastewater treatment.