With the rapid development of economy, petrochemical industry, machinery manufacturing, metallurgy, catering and other industries discharge a large amount of oily wastewater every year, resulting in serious environmental pollution and ecological destruction. The work aims to fabricate durable oil-water separation materials for oily sewage treatment by a facile method. In this experiment, ZnCo2O4 nano-needle arrays were prepared by hydrothermal annealing method on 304 stainless steel mesh substrates (ZnCo2O4-SSM). The surface morphology, composition and wettability of the ZnCo2O4-SSM were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The contact angle test results showed that the water contact angle of ZnCo2O4-SSM in air was 0° and underwater oil contact angle was greater than 155°, indicating superhydrophilic/underwater superoleophobic property. Therefore, when the ZnCo2O4-SSM surfaces contact with the oil-water mixture or emulsion, the oil and water can be effectively separated. Through the oil-water separation experiments, it is found that ZnCo2O4-SSM can efficiently separate several kinds of oil-water mixtures and oil-in-water emulsions under its gravity at room temperature. The separation efficiency of oil-water mixture is greater than 99.8%, and the flux is 3 861-6 114 L/(m2·h). The separation efficiency of oil-in-water emulsion is greater than 99.5%, and the flux is 231-322 L/(m2·h). ZnCo2O4-SSM has recycling stability, and the separation efficiency can still reach more than 99.8% after 30 times of continuous separation of the kerosene-water mixture. The underwater anti-oil-fouling property of ZnCo2O4-SSM is also demonstrated. A stream of light oil (n-hexane) is quickly ejected to the ZnCo2O4-SSM surface and the oil can bounce off the ZnCo2O4-SSM surface instantly without any oil droplets remaining. Furthermore, the heavy oil (CCl4) ejected to the ZnCo2O4-SSM all slips off during the ZnCo2O4-SSM lifting process, and there is no residue. More importantly, the ZnCo2O4-SSM shows superior excellent long-term stability, mechanical durability, and high corrosive environment durability. The underwater oil contact angle (UOCA) does not decrease during air storage for 10 months, indicating the excellent long-term stability of ZnCo2O4-SSM. The underwater oil contact angle (UOCA) is slightly reduced, but it remains underwater superhydrophobic property after dragging 200 cm length. The result shows the good mechanical durability. The underwater oil contact angle and surface morphology of ZnCo2O4-SSM have no obvious change after the immersion test in corrosive medium, including strong corrosion environment (strong acid, pH=1; strong alkali, pH=14; high salt, 3.5wt.% NaCl) and mild environment (neutral and weak acid and alkali). The result confirms that the material has excellent corrosion resistance. In summary, stainless steel mesh serves as a substrate for oil-water separation, which overcomes the disadvantage of poor mechanical strength. The highly chemically stable ZnCo2O4 is employed as a micro-nano structure to improve the durability of the separated materials. The ZnCo2O4-SSM with micro/nanostructures fabricated by the hydrothermal-annealing treatment shows excellent oil-water mixture and oil-in-water emulsion separation performance. Meanwhile, the treatment method is simple, efficient, feasible, and environmentally friendly. Considering the excellent separation performance, durability, and facile preparation, the material shows good potential application prospects in the separation of industrial oily wastewater. © 2024 Chongqing Wujiu Periodicals Press. All rights reserved.
