On-demand oil/water separation of 3D Fe foam by controllable wettability

•The controllable wettability surface was fabricated on Fe foam.•The conversion was achieved by modification and annealing alternately.•The wetting behavior was useful for the gravity-driven oil/water separation.•The superhydrophobic surface presented excellent mechanical and chemical stability.

Oily pollution has become a worldwide problem due to the increasing of oil spill accidents as well as the discharge of oily wastewater. Material with superhydrophobic or underwater superoleophobic characteristic to deal with oily pollution have been reported frequently, but material with controllable wettability transition properties were still few been reported. Herein, we presented a facile, efficient, economical method to prepare a superwetting Fe foam that could achieve controllable wettability transition by modification and annealing alternately. The modified foam showed superhydrophobic and superoleophilic properties (oil-removing mode), which can be used for the filtration of heavy oil in the oil/water mixtures. With the annealing treatment, the as-prepared sample exhibited superhydrophilic/underwater superoleophobic characters (water-removing mode), which allowed water to pass through but blocked light oil. Besides, the as-prepared foam could separate various oil/water mixtures and show high separation efficiency. We are hoping that the controllable wettability filtration sample could realize on-demand oil/water separation and provide a new idea to solve the oil pollution problem.

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