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

Abstract

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 °C. The transparency and the thickness of the TRGs decreased as the reduction temperature increased from 500–1100 °C derived from oxygen-containing functional groups of GO. The X-ray diffraction (XRD) peak of GO is shifted from 25.9° to lower angles with decreases in the thermal reduction temperature. Also, the interlayer spacing (l) calculated from the XRD result decreased in the following order: ƖTRG-500 >ƖTRG-700 >ƖTRG-900 >ƖTRG-1100. The increased ratio of D band to G band (ID/IG) 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 CC/C = C bonds with decreasing oxygen-containing functional groups as compared those of GO. The TRG prepared at the reduction temperature of 700 °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 π electronic structure on TRGs is essential for the effective adsorption of MB having aromatic, ionic and polar characters.