Synthesis, characterization and adsorption study of nano-sized activated alumina synthesized from kaolin using novel method

Synthesis and characterization of nano-sized activated alumina from kaolin using an innovative three-step method are presented. Adsorption study of the as-synthesized activated alumina using phenol solution as absorbate was carried out. The Brunauer–Emmett–Teller (BET) specific surface area, pore diameter and pore volume of the as-synthesized activated alumina were 202.3 m2/g, 1.212 nm and 0.0613 cm3/g respectively. Chemical, mineralogical, morphological and thermal analyses of the as-synthesized activated alumina were carried out using X-ray fluorescence (XRF), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The as-synthesized activated alumina possessed 83.47 wt.% Al2O3. Its XRD pattern possessed characteristic peaks gamma phase of alumina. The as-synthesized activated alumina possessed nano-size morphology; having crystal size value of 12.5 nm. It was thermally stable; the differential thermogravimetric (DTG) analysis showed that only 17 wt.% mass depletion was observed for heating from 30 to 900 °C. Adsorption isotherm of the as-synthesized activated alumina using Freundlich, Langmuir and Dubinin–Radushkevich (D–R) models, gave coefficients of determination of 0.948, 0.962 and 0.867 respectively. The Kf, b, and Kads isotherm constants for were 0.934 mg/g, 0.0116 L/mg and 2.05 × 10− 5 mol2/kJ2 for the Freundlich, Langmuir and D–R models respectively.