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 m(2)/g, 1.212 nm and 0.0613 cm(3)/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 (FOR) 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 degrees 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 K-f, b, and K-ads isotherm therm constants for were 0.934 mg/g, 0.0116 L/mg and 2.05 x 10(-5) mol(2)/kJ(2) for the Freundlich, Langmuir and D-R models respectively. (C) 2015 Elsevier B.V. All rights reserved.