Controlled oxygen functional groups on reduced graphene using rate of temperature for advanced sorption process

The graphenes prepared by a thermal reduction of graphite oxide (GO) at various temperatures were evaluated as a sorbent for the removal of methylene blue (MB) from aqueous environment. The thermally reduced graphenes (TRGs) were prepared by thermal reduction of the dry GO in a furnace adjusted at four different temperatures of 500, 700, 900 and 1100 degrees C. The transparency and the thickness of the TRGs decreased as the reduction temperature increased from 500-1100 degrees C derived from oxygen-containing functional groups of GO. The X-ray diffraction (XRD) peak of GO is shifted from 25.9 degrees to lower angles with decreases in the thermal reduction temperature. Also, the interlayer spacing (I) calculated from the XRD result decreased in the following order: L-TRG-(500) > L-TRG-(700) > L-TRG-(900) > L-TRG-(1100). The increased ratio of D band to G band (I-D/I-G) with the conversion of graphite to GO revealed the increasing disorder due to the oxidation. The increasing thermal reduction temperature increased the fraction of the C-C/C = C bonds with decreasing oxygen-containing functional groups as compared those of GO. The TRG prepared at the reduction temperature of 700 degrees C (TRG-700) exhibited a superior MB sorption capacity of 474.7 mg g(-1), which is far larger than the previously reported values ( < 200 mg.g(-1)) for MB adsorption by reduced GO. These results suggested that an appropriate balance of oxygen-containing functional groups and the delocalized Tc electronic structure on TRGs is essential for the effective adsorption of MB having aromatic, ionic and polar characters.