A new approach to recover the valuable elements in black aluminum dross

Abstract

Black aluminum dross (BAD) is a solid hazardous waste produced during the remelting of aluminum alloy scrap and contains a large amount of aluminum and other valuable elements. However, the extraction of its high-value components is challenging because of its complex phase and chemical composition. In this paper, a new process for recovering aluminum and other valuable elements from BAD is reported, which consists of three steps, i.e., catalytic hydrolysis of aluminum nitride, calcination of the obtained aluminum hydroxide, and molten salt electrolysis to prepare aluminum alloy. Under the established optimal conditions for the hydrolysis of aluminum nitride, 4 wt% NaOH, a temperature of 90°C, a liquid-solid ratio of 6 mL g−1, and a reaction time of 3 hours, the recovery rates of nitrogen and chloride salts are 88.8% and 97.57%, respectively. Bayerite and pseudo-boehmite generated by the hydrolysis of aluminum nitride present in BAD were converted into γ-Al2O3 when calcining the material at 800°C for 2 hours resulting in a multi-metal oxide with high alumina content. Aluminum alloy was prepared by electrolysis of the material in the Na3AlF6-AlF3-Al2O3 electrolyte system. This innovative technology can recover 97% of aluminum and other valuable metals (including silicon) in BAD and is a new route to achieve clean and high-value recycling of BAD.