Study of the preparation of γ-Al2O3 nano-structured hierarchical hollow microspheres with a simple hydrothermal synthesis using methylene blue as structure directing agent and their adsorption enhancement for the dye

The gamma-Al2O3 nano-structured hierarchical hollow microspheres were prepared with a simple hydrothermal synthesis using methylene blue as structure directing agent and the structure directing agent was removed after the gamma-Al2O3 samples were calcinated at 600 degrees C for 2 h. The microstructural and properties of the prepared gamma-Al2O3 samples were characterized by X-ray diffraction (XRD), TEM, BET, FT-IR. The static adsorption of gamma-Al2O3 for methylene blue was conducted. The results showed that when 20 mg (the molar ratio of Al3+ to structure directing agent was 56:1) of structure directing agent was used, the gamma-Al2O3 samples were prepared with that the specific surface area increased by 31% and the maximum adsorption capacity for methylene blue was 8.38 mg/g, increased by 61%. In addition, the adsorption equilibrium isotherms model and adsorption kinetics model were investigated. The adsorption of gamma-Al2O3 for methylene blue is best fitted with Langmuir adsorption model, the kinetic process of adsorption can be described by the pseudo-second-order kinetic model. This study demonstrates the microstructure of gamma-Al2O3 can be effectively controlled and the adsorption properties of it is improved using template synthesis with a proper amount of methylene blue as structure directing agent. (C) 2015 Elsevier B.V. All rights reserved.