Effect of structure-directing agents on facile hydrothermal preparation of hierarchical γ-Al2O3 and their adsorption performance toward Cr(VI) and CO2

Hierarchical flower-like and sphere-like mesoporous gamma-Al2O3 microparticles were successfully prepared by a facile hydrothermal method followed by a calcination process using sodium aluminate as aluminum source, urea as precipitating agent, and Pluronic F127 (EO106PO70EO106), polyacrylic acid sodium (PAAS), and mixed F127-PAAS as structure-directing agents (SDAs), respectively. Effects of the SDAs on the phase structure, morphology, textural properties, surface alkaline, and the adsorption performance toward Cr(VI) and CO2 of the as-prepared samples were comparatively studied by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), N-2 adsorption-desorption, CO2 temperature programmed desorption (CO2-TPD), and UV-Vis spectrophotometric method. The results indicate that the sphere-like gamma-Al2O3 obtained by using F127 as the SDA shows the best adsorption performance toward Cr(VI) with a high adsorption rate of 95% and adsorption capacity of 5.7 mg/g when the adsorption reaches equilibrium for 4 h at room temperature. However, the flower-like gamma-Al2O3 obtained by using PAAS as the SDA has the biggest CO2 adsorption capacity of 1.04 mmol/g at room temperature. This work provides a simple and practical way to prepare potentially bifunctional gamma-Al2O3 adsorbent for the removal of pollutants in water and air treatment from cheap sodium aluminate by using different SDAs. (c) 2013 Elsevier Inc. All rights reserved.