A three-dimensional porous metal foam with selective-wettability for oil-water separation

The development of selective-wettability surfaces of porous materials is important for oil spill cleanup. A new type of oil-water separation material has been prepared through a three-dimensional (3-D) extension of a biologically inspired two-dimensional (2-D) material. In this, a simple solution-immersion method is used to construct a super-oleophilic and super-hydrophobic surface on the metallic skeleton of a copper foam, onto which a nanosheet structure is formed that differs greatly from previous nanoscale needle-based materials. This 3-D copper foam is demonstrated to be capable of supporting a maximum height of accumulated water of 5.5 cm prior to oil wetting and 1.5 cm after oil wetting. Furthermore, the foam is capable of efficient oil-water separation, despite losing its super-hydrophobicity during the process. This has given important new insight into the mechanism of separation, in that super-oleophilicity is clearly important to achieving good separation. The selective-wettability of this porous metal foam is expected to extend the range of metal-based oil-water separation materials from 2D metal meshes to more complex 3-D metal structures.