Efficient cleanup of highly viscous spilled oil using a fast solar-heating and super hydrophobic sponge

A solar-heating sponge, in which the polypyrrole (PPy) coating plays the role of photothermal converter and carbon nanotubes (CNTs) act as the thermal conductor, was fabricated. The sponge can effectively convert sunlight into heat and fast conduct heat so that the temperature can rise to 80 degrees C within 30 s under 1 sun irradiation. Besides, the temperatures of the other parts rise synchronously with the top surface, unlike most reported sponges which had temperature differences between different parts. This advantage can avoid the decrease of diffusion rate of the oil in application. The sponge also exhibits super hydrophobility with a high water contact angle of 151.2 degrees. The excellent solar-heating ability and hydrophobility make the sponge an efficient viscous oil adsorbent. The sponge can continuously and rapidly remove the spilled oil under solar irradiation. The coating composed of interconnected PPy nanosheets is firmly fixed on the surface of the elastic matrix via multiple H bonds. After 10 adsorption-desorption cycles, the adsorption capacity still maintains 97.2 %, without any change in hydrophobility. These advantages including fast solar-heating, super hydrophobility and high regenerability demonstrate that the sponge has great potential in oil spill treatment, especially highly viscous oils.