Sprayed superamphiphilic copper foams for long term recoverable oil-water separation

Superamphiphilic copper foams were prepared by one-step spraying a water-borne solution of hydroxyl-functionalized multi-wall carbon nanotubes and melamine formaldehyde. Water or oil droplets can spread on the coating rapidly and completely in air; meanwhile, oil droplets underwater can retain quasi-spheres without any penetration all the time (superoleophobic underwater), and so the water droplets underoil can do (superhydrophobic underoil). The superamphiphilic copper foams which prewetted by water can effectively separate oil and water solely driven by gravity, showing high separation efficiency and water flux (> 5000 L m− 2 h− 1) for a series of oil-water mixtures. Furthermore, the as-prepared copper foams exhibited outstanding mechanical durability in the long-term mechanical wear process and excellent chemical stability under a series of harsh environment conditions, including strong acid and strong base. Meanwhile, The samples still retained the underwater superoleophobic property after 4 separation-water backwash cycles (> 140 continuous separation repetitions) with the separation efficiency always remaining above 95%, which indicated the excellent recoverability and recyclability.