Recycling of aluminum dross for producing calcinated alumina by microwave plasma

Abstract

Due to the excellent engineering property, aluminum has become an important material for processing industries. As the demand of aluminum increased, a large amount of waste aluminum dross has been generated during the aluminum smelting process. The aluminum dross contained aluminum nitride and would cause odor while being disposed in landfill, making the aluminum dross disposal a tough issue. Therefore, the aluminum dross was mostly stored in the original plants. The objective of this study is to develop an economically-feasible and environmentally-friendly technology to recover aluminum dross. In this study, the original aluminum dross was collected from the secondary smelting aluminum dross factories with 33.6% Al. The aluminum dross was dissolved with 3 M NaOH at 50 °C for 60 min to form NaAl(OH)4 solution. The NaAl(OH)4 was then transformed to aluminum hydroxide by adding H2SO4. Then, the aluminum hydroxide was filtered, washed, and dried. The thermogravimetric analysis and X-ray powder diffraction analysis result show that the main crystal phase of aluminum hydroxide (intermediate product) is boehmite. The aluminum hydroxide powder was calcined at 700 °C for 5 min by an atmospheric-pressure microwave plasma to produce Al2O3. The result show that this process can reduce environmental pollution and recycle aluminum as recoverable form.