Unpowered oil absorption by a wettability sponge based oil skimmerElectronic supplementary information (ESI) available. See DOI: 10.1039/c6ra19571g

Oil spills seriously pollute the environment and cause huge economic losses. Recently, materials with extreme wettability are widely used for oil/water separation. However, the existing methods have drawbacks including complicated and costly fabrication processes for oil/water separation materials, limited oil collecting capacity and reduced oil/water separation efficiency after being polluted by oil, etc. Therefore, an efficient and low-cost method for oil spill collection is urgently needed. We proposed a one-step immersion method to fabricate an oil spill absorption material. Superhydrophobicity and superoleophilicity were obtained by a common polyurethane sponge after being immersed into a cupric stearate solution and drying process. Water droplets can be supported as a spherical shape with a contact angle above 155.5° and can easily roll off from the surface, while hexane, hexadecane, diesel oil, peanut oil and lubricating oil can spread completely on the modified sponge. The prepared sponge can maintain water repellency after continuous oil spill collection for more than 4 h. A large-scale oil skimmer was designed to collect oil spills by employing the extreme wettability sponge and was successfully used for the collection of floating diesel oil, peanut oil, and lubricating oil on water. This method is simple, low cost and mass-producable, and the obtained oil skimmer possesses a high oil collection capacity, excellent durability and recyclability. Therefore, it has application prospects for the collection of oil spills on the sea or under other harsh conditions. Superhydrophobic-superoleophilic sponges equipped on oil skimmers are obtained after being immersed in a copper stearate solution.