Dual Superlyophobic Copper Foam with Good Durability and Recyclability for High Flux, High Efficiency, and Continuous Oil–Water Separation

Traditional oil–water separation materials have to own ultrahigh or ultralow surface energy. Thus, they can only be wetted by one of the two, oil or water. Our experiment here demonstrates that the wettability in oil–water mixtures can be tuned by oil and water initially. Hierarchical voids are built on commercial copper foams with the help of hydrothermally synthesized titanium dioxide nanorods. The foams can be easily wetted by both oil and water. The water prewetted foams are superhydrophilic and superoleophobic under oil–water mixtures, meanwhile the oil prewetted foams are superoleophilic and superhydrophobic. In this paper, many kinds of water–oil mixtures were separated by two foams, prewetted by corresponding oil or water, respectively, combining a straight tee in a high flux, high efficiency, and continuous mode. This research indicates that oil–water mixtures can be separated more eco-friendly and at lower cost.