Preparation of under-liquid superamphiphobic Cu₂O films and selective separation performance of oil-water emulsions

In order to achieve the selective separation of oil-water emulsions by under-liquid superamphiphobic materials, the prepared samples were fabricated by considering two aspects: substrate pore size and wettability, to deal with the phenomenon of difficult separation of oil-water emulsions. In this paper, we used electrochemical constant potential deposition method to deposit the Cu₂O film with the rough structure on the surface of stainless steel mesh (SSM), which abbreviated as Cu₂O@SSM. The prepared sample of Cu₂O@SSM showed the typical characteristics of under-liquid superamphiphobic, and it can easily separate the lotion without the modification of low surface energy materials. According to the size screening effect, the pore size was reduced by coating Cu₂O on stainless steel mesh with different meshes, so as to explore the effect of Cu₂O@SSM film with different pore sizes on the separation performance of emulsion. Besides, the surface morphology, composition, and wetting performance of the products were characterized using the scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and contact angle measurement, respectively. The water and oil droplets on the surface of Cu₂O@SSM showed both superhydrophilic and superoleophilic state with contact angle near to 0° in air. Moreover, the contact angle of underwater superoleophobic and underoil superhydrophobicity exceeded 150°, indicating an under-liquid dual superlyophobic state. By pre-wetting the prepared sample surface with water or oil, the adaptive wettability Cu₂O@SSM sample can realize the selective separation of oil-water lotion, and the separation efficiency of oil-water lotion is more than 96 %. The Cu₂O@SSM film shows the typical selective separation behaviors, which provides a new idea for the selective separation of oil/water emulsions.