▎ 摘　　要

In the present work, graphene oxide was prepared by the modified Hummer's method for the effective removal of rhodamine B and Congo red from their aqueous solution. The synthesized graphene oxide was characterized by different techniques such as thermogravimetric/differential thermal analysis, scanning electron microscopy, Fourier transform infrared spectrometry and X-ray diffraction. It was found that among different models applied, the Langmuir isotherm model fitted the data very well for both the rhodamine B and Congo red dyes adsorption onto the graphene oxide. Moreover, Van't Hoff equation was used to calculate the various thermodynamic parameters such as, enthalpy (Delta H-o), entropy (Delta S-o) and Gibbs free energy (Delta G(o)) for both the selected dyes. The Delta H-o for rhodamine B and Congo red was found to be 4.18 kJ mol(-1) and 10.69 kJ mol(-1) whereas, Delta S-o was found to be 5.95 J mol(-1) K-1 and 8.80 J mol(-1) K-1 respectively. Similarly, the Gibbs free energy (Delta G(o)) was calculated to be -1.89 kJ mol(-1) and -2.78 kJ mol(-1) for rhodamine B and Congo red respectively. The thermodynamic studies indicated that the entire adsorption process was physisorption, endothermic and spontaneous in nature. The high adsorption affinity of the graphene oxide could be due to the electrostatic interaction between the positively charged surface of rhodamine B and negatively charged surface of graphene oxide. Further, this study depicts that the synthesized graphene oxide has a great potential to remove the dyes from waste water effectively.