Preparation of Sulfur-Free Exfoliated Graphite by a Two-Step Intercalation Process and Its Application for Adsorption of Oils

The sulfur-free exfoliated graphite (EG) was prepared by a two-step chemical oxidation process, using natural flake graphite (NFG) as the precursor. The first chemical intercalation process was carried out at a temperature of 30°C for 50 min, with the optimum addition of NFG, potassium permanganate, and perchloric acid in a weight ratio of 1 : 0.4 : 10.56. Then, in the secondary intercalation step, dipotassium phosphate was employed as the intercalating agent to further increase the exfoliated volume (EV) of EG. NFG, graphite intercalation compound (GIC), and EG were characterized by scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD), Fourier transform infrared spectrometer (FTIR), BET surface area, and porosity analyzer. Also, the uptakes of crude oil, diesel oil, and gasoline by EG were determined. Results show that perchloric acid and hydrogen phosphate are validated to enter into the interlayer of graphite flake. The obtained EG possesses a large exfoliated volume (EV) and has an excellent affinity to oils; thus, the material has rapid adsorption rates and high adsorption capacities for crude oil, diesel oil, and gasoline.

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