Removal of Methylene Blue Dye by Metal Free Adsorption and Photodegradation Method Using Different Reduction Grades of Graphene Oxide

Organic pollutant and dyes released into the environment by industries have been highly harmful and toxic for humans as well as for the environment. Graphene oxide (GO) and its reduction form, one of the allotropes of carbon family, were investigated for the removal of pollutant dyes. GO nano-powder was synthesized using an improved version of Hummer’s method and further thermally reduced at different temperatures 125, 150, 175, and 200 °C in the vacuum ambient. An intense (002) diffraction peak was observed at 2θ=9.136° for the pristine GO in the X-ray diffraction spectra which is gradually shifted towards the higher angles with the reduction, and it disappeared if the GO sample reduced at 200°C. I D /I G ratio for GO nano-powder in the Raman spectra decreased from 0.94 to 0.76 due to reduction. GO shows a characteristic absorption band at 3395 cm -1 in Fourier transform infra-red spectra corresponding to stretching of hydroxyl (–OH) group, this peak is flattened with the thermal reduction but not eliminated completely. The band gap of pristine GO significantly reduced from 2.31 to 0.73 eV with the reduction as measured by UV-Vis diffuse reflectance spectrophotometer. Dye adsorption and photocatalytic degradation behaviour of the pristine GO and reduced graphene oxides (rGOs) was examined towards methylene blue dye for 10 mg of GO/rGOs powder in 50 ml of 50 ppm solution by UV-Vis absorption spectroscopy. Pristine GO showed potential adsorption capacity and dye was degraded up to 85.78% within 15 minutes and around 97% after 4 hrs. Meanwhile, highest 47.58% photocatalytic degradation of Methylene blue was achieved for the rGO sample reduced at 150°C in the presence of visible light of 100 watt.