Removal of AlN from secondary aluminum dross by pyrometallurgical treatment

A new process of AlN removal from secondary aluminum dross (SAD) by pyrometallurgical treatment with added cryolite was applied for solving the problem of recycling the secondary aluminum dross. The response surface methodology (RSM) was used to design experiments and optimize parameters. The results show that adding the appropriate amount of cryolite can effectively promote the oxidation of AlN in the SAD, and too much cryolite will reduce the promotion effect. The effects of roasting temperature and cryolite on the denitrification rate are the most significant (p < 0.0001) followed by holding time. Predicted values of the denitrification rate are found to be in good agreement with experimental values (R2 = 0.9894 and $$R_{\text{adj}}^2=0.9775$$ , which confirms the validity of the model employed. The optimum conditions of roasting temperature of 750 °C, holding time of 194 min, mass fraction of cryolite of 17.7% are obtained according to the quadratic model. Under these conditions, the maximum actual denitrification rate reaches 94.71% and the AlN content in the SAD is only 0.55 wt%. The unfired brick with compressive strength of 18.62 MPa (GB/T 2542-2012) was prepared based on the roasted SAD.