Facile fabrication of superhydrophobic copper mesh for oil/water separation and theoretical principle for separation design

A facile fabrication method was developed to obtain the superhydrophobic copper mesh for oil/water separation. The fabrication process involves the oxidation of the copper mesh followed by low pressure annealing at low temperature. The latter treatment enhances the hydrophobicity of the mesh by the formation of the Cu₂O surface layer. This superhydrophobic mesh demonstrates high mechanical flexibility and the chemical stability. Moreover, the superhydrophobicity remains even for hot water drops (>90 °C), indicating its thermal stability. Because of high oil affinity and water repellency of this superhydrophobic mesh, the mixture of various organic solvents with water can be easily separated into individual components. The separation efficiencies for the oil/water mixture were above 99% even after 40 separation cycles. Also, it was successful for the separation of hexadecane/hot water (>90 °C) mixture. The separation performance is practically competent according to the water intrusion pressure and oil flux. Our superhydrophobic meshes are robust in harsh water conditions and can be employed as an efficient filtration membrane. Based upon the experimental results and capillarity model, the design principle for oil/water separation membranes was proposed as well.