[Adsorption of methylene blue from aqueous solution onto magnetic Fe3O4/ graphene oxide nanoparticles]

A simple ultrasound-assisted co-precipitation method was developed to prepare magnetic Fe3O4/graphene oxide (Fe3O4/ GO) nanoparticles. The characterization with transmission electron microscope (TEM) indicated that the products possessed small particle size. The hysteresis loop of the dried Fe3O4/GO nanoparticles demonstrated that the sample had typical features of superparamagnetic material. Batch adsorption studies were carried out to investigate the effects of the initial pH of the solution, the dosage of adsorbent, the contact time and temperature on the adsorption of methylene blue. The results indicated that the composites prepared could be used over a broad pH range (pH 6-9). The adsorption process was very fast within the first 25 min and the equilibrium was reached at 180 min. The adsorption equilibrium and kinetics data fitted well with the Langmuir isotherm model and the pseudo-second-order kinetic model. The adsorption process was a spontaneous and endothermic process in nature. The composite exhibited fairly high adsorption capacity (196.5 mg.g-1) of methylene blue at 313 K. In addition, the magnetic composite could be effectively and simply separated by using an external magnetic field, and then regenerated by hydrogen peroxide and recycled for further use. The results indicated that the adsorbent had a potential in the application of the dye wastewater treatment.