Synthesis of reduced graphene oxide and its application for the removal of anaionic dye TURQUOISE GN

Abstract

Although graphene oxide (GO) and its derivatives showed excellent adsorption capacities for dyes and heavy metals, its application is limited to cationic and commercially used dyes. In this article reduced graphene oxide (RGO) was prepared and applied for the adsorption of a commercially used anionic dye. GO was prepared from graphite powder by modified Hummer’s method and reduced to RGO by hydrazine hydrate. Characterization of prepared RGO was carried out by Raman spectroscopy, ESEM, XRD, elemental analysis and the surface charge was determined by zeta potential analysis. An anionic dye TURQUOISE GN (TGN) was used to investigate the adsorption capacity of prepared RGO. To know the adsorption properties of RGO, the effects of solution pH, dosage of adsorbent, concentration of the dye, adsorption time and temperature on adsorption capacity of RGO were also studied. The distribution of the adsorbate on the RGO surface was studied with both Langmuir and Freundlich isotherm models and it was found that it preferably followed Langmuir model. The theoretical maximum adsorption capacity was found to be 588.24 mg/g at pH 7. To find out the mechanism of the adsorption of TGN on RGO pseudo-first-order and pseudo-second order kinetic models were applied and the results fitted perfectly with the second-order kinetic model. The exhausted RGO was regenerated by treating with 2 % HCl followed by washing with demineralized water and showed moderate adsorption capacity.