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

Abstract

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 202.3m2/g, 1.212nm and 0.0613cm3/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 83.47wt.% 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 12.5nm. It was thermally stable; the differential thermogravimetric (DTG) analysis showed that only 17wt.% 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 0.934mg/g, 0.0116L/mg and 2.05×10−5mol2/kJ2 for the Freundlich, Langmuir and D–R models respectively.