Fabrication of 3D porous superhydrophobic sponges using plant polyphenol-Fe3+ complexes as adhesive and their applications in oil/water separation

A robust and 3D superhydrophobic composite sponge was facilely prepared by stable coating of multiple walled carbon nanotubes (MWCNTs) onto melamine sponge (MS) using polyphenol-Fe3+ complexes as the low-cost and efficient adhesives. The as-prepared superhydrophobic composite sponges featured ultra-low density, large porosity, high robustness and elasticity, as well as flame resistance. The loading of MWCNTs influenced the superhydrophobicity of sponge, and the optimized loading of MWCNTs was determined to be 3.0%, with a water contact angle of 159.8 degrees. The 3D superhydrophobic sponge exhibited high absorption capacity to a wide range of oils and organic solvents, up to 38-127 times of its own weight dependent on the variety of oil and organic solvent. After 10 recycles of repeative absorption, the loss of absorption capacity was as low as 0.9% per cycle. The 3D superhydrophobic sponge was also applied for continuous separation of spilled oil from water with a separation efficiency of 97%. Our approach could also be extended for coating other carbon materials on MS, including graphene and activated carbon. The resultant sponges were still superhydrophobic and exhibited high separation ability for immiscible oil/water mixture.