Abstract
The main focus of this work was to prepare graphene tin oxide composite as a novel adsorbent for the removal of hazardous anionic dye, Congo Red, from aqueous systems. The composite was prepared by a simple solvothermal method. The adsorbent was characterized via scanning electron microscopic analysis, energy-dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis. The energy-dispersive spectra of graphene tin oxide composite showed a high percentage of tin (62.11%) with a reduction in the percentage of carbon (47.45 to 13.75%) and oxygen (39.37 to 23.71%) suggesting that the composite has been successfully prepared. Fourier transform infrared spectroscopic analysis showed that the intensity of some absorption peaks like C=O, C=O and OH decreased which support the effective reduction in graphene oxide to graphene in the composite. Removal of Congo red by graphene tin oxide composite was carried out as a function of pH, dye initial concentration, contact time, temperature and adsorbent dose in batch mode. Optimum adsorption was observed in the pH range of 2 to 4 with contact time of 60 min. Langmuir and pseudo-second order kinetic model fitted very well the isotherm and kinetic data, respectively. The maximum uptake capacity determined by Langmuir model was observed to be 359.71 mg/g at 318 K. Thermodynamic investigations have shown endothermic and spontaneous nature of Congo red adsorption. Regeneration studies revealed that graphene tin oxide composite could be a viable and potential adsorbent for detoxification of dyes bearing wastewater.