Optimizing Wet Hydrolysis for Nitrogen Removal and Alumina Recovery from Secondary Aluminium Dross (SAD)

Secondary aluminum dross is a solid waste generated after removing aluminum from industrial aluminum slag (primary aluminum dross), which is included in the European Hazardous Waste List because of harmful substances such as aluminum nitride. More and more SAD is being directly disposed of in landfills, which will not only harm the ecological environment and human health, but also cause resources. Under the background of green and low-carbon circular economy, nitrogen removal and resource recycling of SAD are very important environmental pollution, resource and the economic benefits of the aluminum industry. In this study, a new method was introduced to explore the interaction between various factors in the denitrification process by using the response surface method, and the optimal denitrification process conditions were predicted and determined by a regression equation that is, the denitrification rate of SAD was 99.98% at the reaction time of 263 min, reaction temperature of 95 ℃ and concentration of 6.5 wt.%. Furthermore, the content of Al₂O₃ in SAD was successfully elevated to 98.43% through the reaction carried out in a 10 wt.% NaOH solution system at the controlled temperature of 90 °C for 5 h. It was summarized that the wet treatment methodology can efficiently eliminate aluminum nitride (AlN) from SAD and heighten the Al₂O₃ grade to meet metallurgical standards. This research is expected to eliminate the adverse impact of SAD on the environment and its safety risks, and provide an innovative method for the sustainable resource utilization of SAD.