Synergistic effect of inorganic salt and AlN removal in the secondary aluminum dross during the roasting process

Abstract

This study investigated the synergistic transformations and interaction effects of inorganic salts with high-content (HS-SAD) and low-content (LS-SAD) and AlN in secondary aluminum dross (SAD) during the roasting process. The results demonstrated that the presence of inorganic salts significantly enhanced the oxidation of AlN in SAD. The removal efficiency of AlN in HS-SAD reached 95.8 % at 800 °C for 120 min, whereas in LS-SAD, it was 69.47 % at 1000 °C. The oxidation of AlN leads to the formation of a 25–45 nm alumina film, which hinders the further progression of the oxidation process. The presence of SO2 and SiO2 facilitated the low-temperature volatilization of inorganic salts, thereby limiting the formation of the alumina film. The partial melting of inorganic salts and the reaction of NaF with the alumina film, resulting in the formation of Na2O, destroyed the dense alumina film, exposing AlN. Following roasting at 800 °C and 1000 °C, the hazardous components in both HS-SAD and LS-SAD were effectively eliminated, and 92.93 % of the inorganic salts in HS-SAD were successfully recovered. Roasting at a mixing ratio of 1:1 at 900 °C for 120 min resulted in an 86.97 % removal efficiency of AlN. These findings offer valuable insights into the removal of AlN in SAD and the comprehensive utilization of SAD residue.