Melamine-derived carbon sponges for oil-water separation

The elaboration and characterization of hydrophobic melamine-based sponges are presented. Sponges were obtained by single-step carbonization of commercial melamine foam having a 3D interconnected network. We show that optimized sponges can be elaborated from a simple pyrolysis treatment with rather low temperatures of 500–600 °C. These materials exhibited excellent absorption capacities (they absorbed 90 to 200 times their own weight), a very high porosity of 99.5%, a low density around 7 mg/cm3 and water contact angles ranging from 120° to 140° close to superhydrophobicity. The relationship between hydrophobicity and physicochemical evolution on heat treatment (carbonization process, diffusion of additives, porosity evolution) was studied in detail. The as-prepared carbon sponges are compressible up to 80% with a Young’s modulus ranging from 0.58 kPa to 0.80 kPa, and keep part of their elastic properties after a hundred compression-decompression cycles. The carbonized sponges were characterized by thermogravimetric analysis (TGA), infra-red spectroscopy (FTIR), Raman spectroscopy, elemental analysis (EA), X-ray photoelectron spectroscopy (XPS) and scanning electronic microscopy (SEM). These characteristics make these materials promising absorbents for water depollution: oil-spill clean-ups or removal of oils and organic solvents from water, especially for the recovering of the pollutant by simple squeezing of the absorbent.