Ultralight, robustly compressible and super-hydrophobic biomass-decorated carbonaceous melamine sponge for oil/water separation with high oil retention

To address the high-cost hydrophobic modification of three dimensional commercial sponges, here natural cellulose nanocrystcals (CNCs) were employed to prepare ultralight, robustly compressible and super-hydrophobic biomass-decorated carbonaceous melamine (BCM) sponges by a facile immersing-adsorption-pyrolysis method. Due to the introduction of CNCs, originally pyrolyzed melamine sponges with super-hydrophilicity were changed into the ultralight BCM sponge (7.3 mg cm−3) with super-hydrophobicity and excellent mechanical property. Being applied to the oil/water separation, BCM sponges showed good oil selectivity, high oil absorption capacities up to 201 g/g or 94% of its own volume, and even high oil retention. Simultaneously, the excellent compressibility and good flame retardancy of BCM sponges ensured that the absorbed oil can be recovered by combustion and squeezing methods. Based on super-hydrophobicity, good flexibility and high porosity of BCM sponges, the spilled oils could be also consecutively collected from water surface to collecting vessels by our designed oil collection apparatus.