Abstract: Graphite oxide (GO) with high cation exchange capacity was prepared with potassium persulfate as the expansion agent and potassium permanganate as the oxidant by an expansion-oxidation method in one step. Scanning electron microscopy, X-ray diffraction , Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the morphology, structure, and the type and content of oxygen containing functional groups of the samples. As a result, the intercalating expansion treatment with K₂S₂O₈ could effectively inhibit the peroxide phenomenon of GO, making the slice layer thinner and the oxidation degree more evenly. With the increase of potassium persulfate dosage, the ratio of epoxy groups to hydroxyl and the relative content of carboxyl in the structure of GO increases, so does the cation exchange capacity. However, when the dosage of potassium persulfate is too high, the ratio of epoxy groups to hydroxyl becomes lower, leading to the decrease of the cation exchange capacity. When the mass ratio of potassium persulfate to graphite is 5∶1, the obtained GO has a high degree of oxidation and a more uniform oxidation, and the ratio of hydroxyl group to epoxy group is the highest. The cation exchange capacity of GO is 579.5 mmol/100 g.

Key words: Graphite oxide, Potassium peroxodisulfate, Expansion-oxidation method in one step, Oxygen-containing functional group, Cation exchange capacity