Production of High Purity α- and γ-Alumina From Aluminum Dross

Abstract

Aluminum dross (AD) is a hazardous solid industrial tailing which is generated during aluminum and aluminum alloys production. The AD imposes very serious ecological and environmental problems. So, finding an appropriate solution to reduce, reuse, and recycle the AD is of upmost importance. This work elucidates production and characterization of high purity α- and γ-alumina from the AD. These two high value-added products were produced through a multi-step hydrometallurgy-based process including acid leaching of the AD, co-precipitation of metal hydroxides from the obtained leach liquor, selective re-dissolution of precipitated aluminum hydroxides in caustic soda solution, re-precipitation of aluminum hydroxide, and calcination. As a consequence of the proposed process, the aluminum hydroxide gel was firstly precipitated from sodium aluminate-rich liquor by adjusting the pH at 12.0. Finally, the aluminum hydroxide gel was calcined at 700 and 1200°C for 2 h to obtain γ- and α-alumina, respectively. The as-produced alumina materials were characterized using Zn-back titration, X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy, nitrogen sorptometry, filed emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The XRD pattern revealed a crystal size of 10.8 and 29.7 nm for γ- and α-alumina, respectively. A purity of more than 98% was achieved through Zn-back titration for both products. The nitrogen sorptometry disclosed that the as-prepared γ- and α-alumina exhibited specific surface areas of 147 and 11 m2/g, respectively. Overall, the results suggest a promising recycling solution to the environmental concerns of the waste, as well as gaining economic benefits.