Adsorptive removal of cationic and anionic dyes using graphene oxide

This paper presents the results of comparative study on the application of graphene oxide (GO) for the adsorptive removal of crystal violet (CV) and methyl orange (MO) in batch mode. GO, synthesised from graphite, was characterised by field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy, point of zero charge (pH_PZC) and ultra violet (UV) spectroscopy. Dispersion of GO in water revealed the conversion of hydrophobic graphite into hydrophilic. Performance with regard to adsorption of CV and MO on GO was evaluated at different values of the operational parameters such as contact time between GO and the dye molecules, dosage of GO, and initial concentration and pH of the dye solution. Uptake and percentage removal of the dyes increased with increase in contact time and adsorbent dosage, but declined with increase in initial concentration of the dye. Experimental data on the uptake of dye molecules by GO showed good fit with the Freundlich isotherm model and the pseudo second order kinetic model. The maximum uptake by GO was higher for CV (207.4 mg/g) than that for MO (37.2 mg/g). Results indicate that GO is an effective adsorbent for the removal of CV but not for MO.