Fabrication of robust surfaces with special wettability on porous copper substrates for various oil/water separations

We fabricated robust superhydrophilic or superhydrophobic films on porous copper substrates including copper mesh and copper foam for various oil/water separations. By simple acid etching and replacement reaction, a composite film comprised of copper and silver (denoted as Cu@Ag) with superhydrophilic and underwater superoleophobic properties was prepared. After modification with n-dodecanethiol (DDT), the superhydrophobic and superoleophilic film (denoted as Cu@Ag@DDT) with excellent mechanical stability and chemical stability was then obtained. Both the Cu@Ag coated mesh and the Cu@Ag@DDT coated mesh exhibited efficient separation for various immiscible oil/water mixtures. Importantly, the Cu@Ag coated foam and the Cu@Ag@DDT coated foam respectively realized the separation of surfactant-stabilized oil-in-water and water-in-oil emulsions because of the combination of their opposite wettability for water and oils and individual cage-like structure. The facile strategy presented here provides a novel approach for diverse oil/water separations in practice.