Abstract

• Environmental pollution as a result of rapid development of technologies is one of the serious global concerns. Dyes are usually used in textile manufacturing and are one of the major contaminations in water. Thus, from an environmental point of view, the removal of dyes is of great concern, and recent applications using graphene oxides showed high adsorption ability. Graphene oxide (GO) is a highly effective absorbent of methylene blue (MB) and can be used to remove from aqueous solution. Two different graphene oxides (LGO and CGO) were synthesized from two different graphite sources by using modified Hummer method. Local graphite sample (LGP) was collected from Lin-yaung-chi mine and commercial graphite powder (CGP) was purchased from local chemical shop. The crystalline structures of different graphite varieties and prepared graphene oxides were also characterized by XRD. The optical properties of each graphite and prepared graphene oxides were characterized by UV-Vis spectrometer. The analysis of FT IR spectra was performed to investigate functional groups of graphite and the prepared GO. The surface morphologies of each graphite and prepared graphene oxides were characterized by scanning electron microscope (SEM). Graphene oxide is a material containing functional groups such as carboxyl, carbonyl, epoxy and hydroxyl, that can adsorb cationic dyes. Factors such as initial concentration of dye (MB), the dosage, temperature, contact time, rpm and pH were evaluated. The adsorption capacities of methylene blue on CGO and LGO were nearly 99% under the optimal conditions (dosage = 0.1 g, MB concentration 30 ppm, contact time = 60 min, temperature 35 ºC, rpm = 150 and pH=8). Results show that the adsorption equilibrium, the removal efficiencies were higher than 99 % and the solution can be decolorized to nearly colourless. Results show that GO is an effective adsorbent being used to treat effluents contaminated with dyes.