Single Adsorption Capacity of Methylene Blue on ZnO/C Nanosphere:Equilibrium, Kinetics and Mechanism

Abstract

Carbon-inorganic ZnO/C nanosphere hybrid materials was simply prepared by arc discharge method. The hybrid materials was characterized by field-emission scanning electron microscopy(FE-SEM), X-ray diffraction(XRD) and BET surface area. The adsorption property of methylene blue (MB) on ZnO/C nanosphere was carried out under the dark conditions. Results showed that the adsorption uptake increased as the increase of initial MB concentration and contact time, and the process reached equilibrium at the time of 150 min. Langmuir, Freundlich and Temkin isotherm were employed to describe the adsorption equilibrium. The isotherm study indicated that Langmuir model fitted well with the adsorption data, and a monolayer saturation capacity of 188.68 mg·g -1 was obtained. Kinetic models, Webbers pore diffusion model and Boyds equation were applied for the experimental data to study the adsorption mechanism. Results shows that the kinetics followed the pseudo-second order kinetic model and the adsorption process was controlled by film diffusion as opposed intraparticle diffusion mechanism. The results indicate that the ZnO/C nanosphere is also a promising material for the adsorption of MB from aqueous solutions.