Reduced graphene-based superhydrophobic sponges modified by hexadecyltrimethoxysilane for oil adsorption

A superhydrophobic/superoleophilic material was prepared by coating hexadecyltrimethoxysilane-grafted reduced graphene oxide on the skeleton of a melamine sponge (HDTMS/rGO-MF) via a low-cost and simple method. The structure of HDTMS/rGO-MF was confirmed by scanning electron microscopy/energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. HDTMS/rGO-MF showed repellency to water and affinity to oil, with a water contact angle of 153.2 degrees and oil contact angle of nearly 0 degrees. Owing to its hierarchical pore structure and superhydrophobicity, the absorption capacities of HDTMS/rGO-MF for various oils and organic solvents were 8.79-20.85 g/g. Additionally, HDTMS/rGO-MF could be successfully reused through absorption-squeezing and absorption-distillation cycles, due to its chemical and mechanical stability. Thus, HDTMS/rGO-MF was used in an oil-collecting device with the assistance of a pump or a funnel, and achieved recovery rates of 50 %-90 % for various organic solvents. In particular, the recovery of chloroform reached 97 % after 10 cycles of filtration-separation. Moreover, HDTMS/rGO-MF increased the transparency of the n-hexane-in-water and toluene-in-water emulsion.