Switchable wettability of nanostructured Co-Ni(OH)₂/Ni foam and high efficient oil-water separation

The more and more oily sewage from industry, shipping and domestic life greatly threaten our life and health. In this work, the porous Co-Ni(OH)(2)/Ni foam composites were prepared by a simple hydrothermal method and subsequent annealing at 200 C-degrees. The high surface energy and novel structure of nanocone array endowed the composite with superhydrophilicity and superoleophobicity. After the surface modification of stearic acid (STA) with low surface energy, the Co-Ni(OH)(2)/Ni@STA composites were endowed with superlipophilicity and superhydrophobicity due to the low surface energy of STA and special surface nanostructure. Meantime, two extreme wetting states can be switched by alternating 200 C-degrees calcination and STA surface modification. And the doping of Co element endows the composites with the excellent corrosion resistance. Based on the controllable switchable wetting performance of Co-Ni(OH)(2)/Ni composite, a three-way T-tube was designed for oil-water separation. Whether it is heavy oil or light oil, the device has high separation efficiency and excellent cyclic stability.