Pyrometallurgical process and multipollutant co-conversion for secondary aluminum dross: a review

A considerable amount of secondary aluminum dross is generated in the aluminum refining process. Secondary aluminum dross (SAD) is hazardous waste because of its constituent pollutants, such as AlN, fluoride, chloride, and heavy metal pollutants. SAD treatment can be categorized into thermal and wet methods. The thermal process has attracted considerable research attention because of its simplicity and ability to prepare Al–Mg spinels, refractory materials, and ceramics and recover alumina during the treatment. However, at this stage, SAD pyrolysis processes are typically focused on the removal of single pollutants. Limited studies have explored the simultaneous removal of various pollutants and their interactions. This study focused on the pyroprocess in the SAD treatment process and investigated the SAD mechanism in the preparation of Al–Mg spinel, refractories, ceramics, and recycled alumina. Furthermore, the conversion of AlN, fluoride, chloride salts, and heavy metals, which are the main pollutants generated in the thermal reaction of SAD, and their control mechanisms were analyzed. The synergistic mechanism of SAD denitrification∖chlorine salt and fluoride fixation∖heavy metal was studied through the reaction mechanism of similar component minerals in the pyroprocess for improving the high-value utilization of SAD and scientific prevention and control of secondary pollution. Finally, the feasibility of preparing ceramic pellets from aluminum dross (AD) was evaluated. The results of the study can provide crucial development directions for SAD utilization.