Integrated device based on cauliflower-like nickel hydroxide particles-coated fabrics with inverse wettability for highly efficient oil/hot alkaline water separation.

In this paper, we report for the first time the fabrication of cauliflower-like Ni(OH)2 particles-coated fabrics with inverse special wettability via a facile hydrothermal method. The coated fabric is superhydrophilic in air and superoleophobic underwater, which can be changed into superhydrophobicity after being modified by long-chain fatty acid. After the superhydrophilic fabric is wetted by water in advance, hot alkaline water can be removed from the light oil/water mixture driven by gravity. Also, heavy oil can be removed from the heavy oil/hot alkaline water mixture under the action of gravity using superhydrophobic fabric. The separation efficiencies of the two fabrics for different mixtures of hot alkaline water and light or heavy oil are more than 95.8%. Furthermore, a two-way separation device was designed via integrating a pair of fabrics with opposite wettability. The device can continuously separate oil and water at the same time from oil/hot alkaline water mixture via one-step route with high separation efficiency without consideration of the density of the oil. Moreover, the superhydrophilic fabric is capable of separating various oil-in-water emulsions. We believe that the as-prepared fabrics and the designed device may find wide application in separating oil from alkaline water.