Study of Photocatalytic Degradation and Simultaneous Removal of a Mixture of Pollutant (MB and MG) Dyes: Kinetic and Adsorption Isotherm

Background: The major challenges faced by developing countries are the issues associated with various pollutants, such as dyes, pesticides, heavy metals, etc. Various materials and methods are available for the removal of these pollutants. Major research works have been performed on single pollutants, and rarely any research literature is available for a mixture of pollutants. This is one of the major reasons to carry out our research work in this field. Objectives: This study aimed to develop an efficient ZnO/GO nanocomposite as a photocatalyst, characterize it by PXRD, FT-IR, and TGA, and evaluate its catalytic activity by degradation of MG, MB and a mixture of both. Methods: In this study, GO was synthesized by the modified Hummer’s method. In this method, graphite powder was mixed with sulphuric acid and NaNO3. Then KMnO4 solution was added under continuous stirring. Excess KMnO4 was removed by H2O2 and the colour of the solution turned to be dark yellow. After proper washing and maintaining pH, the resulting material was dried at 60°C for 12h to obtain GO. GO was dispersed in ethanol, and 0.387g Zn(CH3COO)2.2H2O was added to it. The resulting mixture was sonicated, and a solution of NH3 was added very slowly by maintaining the pH of the solution at ~7. The resulting product was dried at 80°C and then calcined at 500°C for 2.5 h to get ZnO/GO nanocomposite. Results: The photodegradation of MG, MB and a mixture of MG and MB dyes was found to be 92.23%, 35.96%, and 66.22%, respectively, in 4-5 h. The degradation of the dyes was found to follow Secondorder kinetics with a multilayer absorption phenomenon. Conclusion: MB showed less degradation as compared to MG, but its photocatalytic activity enhanced after adding MG. This ZnO/GO nanocomposite seems to be a potential candidate to address the challenges associated with multi-pollutants, such as dyes.