Recovering AlN from secondary aluminum ash using a novel triboelectric separation

ABSTRACT Secondary aluminum ash is a byproduct in the aluminum industry that contains valuable components, such as aluminum nitride (AlN) and aluminum oxide (Al2O3). AlN has excellent thermal and electrical properties and is widely used in various applications, making the recovery of AlN from secondary aluminum ash essential for both economic and environmental reasons. In this study, we developed a novel triboelectric separation technique to recover AlN from aluminum ash by investigating the tribocharging characteristics of the main components of secondary aluminum ash, Al2O3 and AlN. We studied the effects of tribocharging ball ratio, friction time, and stirring speed on the tribocharging of pure Al2O3 and AlN, using various materials such as polytef (PTFE), polypropylene (PP), polyvinyl chloride (PVC), copper (Cu), and stainless steel (SS) as tribocharging materials. We also examined the effects of friction medium ball ratio, friction medium material, rotational speed, and voltage on the triboelectric separation process. Our results showed that the charge-to-mass ratio for Al2O3 and AlN was 1.96 and −15.56 nC/g, respectively, the difference is largest, with a PTFE ball, a 1:5 ratio, a stirring speed of 290 n/min, and a tribocharging duration of 30 s. The triboelectric sequence of these friction materials was (+)PTFE, PP, Al2O3, SS, Cu, PVC, and AlN (-). To recover AlN from aluminum ash, PTFE should be chosen as the friction medium, and a friction medium ball ratio of 1:3, rpm rotation speed of 50, and voltage of 40kV should be used, resulting in an AlN grade of 89.25% and a significant increase in the recovery rate of AlN in the positive and negative electrode. Our findings demonstrate the feasibility of effective triboelectric separation of Al2O3 and AlN.