Enhanced hydrolysis of aluminium nitride from secondary aluminum dross through combination of wet-stirred milling and alkaline leaching

Abstract Deep hydrolysis for removing hazardous aluminium nitride (AlN) from secondary aluminum dross (SAD) remains a challenge nowadays. Enhanced hydrolysis of AlN from SAD through a combination of wet-stirred milling and alkaline leaching is investigated in the present study, which has not been reported before. SAD is activated during wet-stirred milling just with water by reducing the grain size and increasing the active surface area. Leaching with NaOH dissolves the hydrolysis products (AlOOH, Al(OH)3) to expose reactive sites of unhydrolyzed AlN, contributing to the enhanced hydrolysis process. Results indicate that by utilizing optimized conditions (10 min wet milling, 5 wt.% NaOH solution, L/S ratio of 2, 75 ℃ temperature, and 120 min duration), 98.3% of AlN is removed from SAD. The kinetic analysis indicates that the hydrolysis process is controlled by both diffusion and chemical reactions, with the activation energy calculated to be 31.0 kJ/mol. After undergoing this enhanced hydrolysis process, the residue, which consisted primarily of Al2O3 and Al(OH)3,can be recycled as Al concentrate. The technology has been already applied in a pilot plant and achieved a favorable effect in practical applications. Statement of Novelty Efficient hydrolysis for removing hazardous aluminium nitride (AlN) from secondary aluminum dross (SAD) remains a challenge nowadays. An enhanced hydrolysis process for removing AlN from SAD has been developed and reported in this study. The results demonstrate that the progress is highly efficient and can be performed using a combination of wet-stirred milling and alkaline leaching. This solution has not been reported before, and relevant patent authorization has been obtained by our research group. The technology has been already applied in a pilot plant that processes 20000 tons of SAD per year, achieving a favorable effect in practical applications, facilitating the disposal of waste and the protection of environment.