Superhydrophilic and underwater superoleophobic zirconium-based metal–organic framework composite stainless steel mesh for oil–waterseparation

Abstract

Zirconium-based metal–organic frameworks (UiO-66) have a multistage pore structure, high specific surface area and excellent hydrophilic/oleophobic properties, which are promising in the field of oil–water separation. In this study, zirconium-based metal–organic framework composite stainless steel mesh (SPU-66) was prepared by in situ growth of UiO-66 on stainless steel mesh (SSM) using polydopamine (PDA) as an intermediate layer. The water contact angle (WCA) and underwater oil contact angle (UWOCA) measurements of the SPU-66 composite membrane proved that the membranes have superhydrophilic/underwater superoleophobic properties (WCA <5°, UWOCA = 156 ± 1°), which allow for the efficient separation of different oil–water mixtures. The surface morphology, chemical structure and wetting behaviour of SPU-66 were characterized using XRD, SEM, EDS, FTIR, XPS and contact angle tests. The results show that UiO-66 grown on the SSM surface exhibits a regular ortho-octahedral structure (200 nm) and has a high crystallinity. Driven by gravity, the composite membrane exhibited high separation efficiency and separation flux for six different types of oils, with a separation efficiency of 98% ± 0.2% for low-viscosity oils (n-hexane, gasoline, and methylene chloride) and 97% ± 0.3% for high-viscosity oils (diesel, paraffin, and white oil). The wettability mechanism of the SPU-66 composite membrane was analysed through the material surface free energy theory and capillary force separation model to reveal its oil–water separation mechanism. In addition, the composite membrane maintains excellent chemical and mechanical stability under harsh environmental conditions. In conclusion, the SPU-66 composite membrane shows broad application prospects in the field of oil–water separation, and can be used in various scenarios, such as drilling fluid treatment and offshore oil spills.