Selective extraction of aluminum from coal-bearing kaolinite by room-temperature mechanochemical method for the preparation of γ-Al2O3 powder

Coal-bearing kaolinite (CBK) is a solid waste generated during coal production. Despite being a potential source of aluminum, CBK presents a great challenge in terms of Al recovery. To tackle this challenge, we used a room temperature mechanochemical method based on mechanical grinding and sulfuric acid treatment. Ground samples were characterized by X-ray diffraction, thermogravimetry and Fourier transform infrared spectroscopy to reveal that the degree of kaolinite amorphization increased with grinding time, mirrored by the concomitantly increasing Al extraction efficiency. An extraction efficiency of 100% was obtained after 12-h grinding (resulting in complete kaolinite amorphization) and 2-h leaching with 3 M sulfuric acid and the leached aluminum could be readily recovered from the leaching liquor as Al-2(SO4)(3)center dot 18H(2)O using ethanol as a precipitant. Thermal decomposition of the Al-2(SO4)(3)center dot 18H(2)O at 900 degrees C could produce gamma-Al2O3 powder with a purity of 97.56% and a surface area of 206.9 m(2). g(-1). (C) 2017 Elsevier B.V. All rights reserved.