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

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 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 grew on the SSM surface exhibits a regular ortho-octahedral structure (200 nm) and had 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 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, SPU-66 composite membrane shows a broad application prospect in the field of oil-water separation, which can be used in various scenarios, such as drilling fluid treatment and offshore oil spills.