Research progress on the characteristics of secondary aluminum dross and its detoxification and utilization

Secondary aluminum dross is a typical hazardous solid waste inevitably generated during aluminum production and processing. It contains not only a large amount of AlN, chlorine salts, fluoride and other hazardous substances, but also about 40% of aluminum, which is a potential aluminum resource with great utilization value. The sources and properties of secondary aluminum dross, as well as the progress of research on the harmless and resourceful utilization, are reviewed in this paper. The research results show that the pyrometallurgical process focuses on achieving large-scale utilization of secondary aluminum dross with high processing efficiency, and the common products include cement, refractory materials, calcium aluminate refining agent, ceramic heat storage ball and so on. However, due to the large amount of volatilization of salts, the pyrometallurgical process suffers from high energy consumption, serious corrosion of equipment, and large restrictions on the composition of raw materials. The hydrometallurgical process, on the other hand, focuses on achieving the harmlessness of secondary aluminum dross, which is an environmentally friendly and more inclusive detoxification of raw materials. However, the acid and alkali leaching process has a large amount of waste liquid discharge, and the water leaching process has incomplete removal of AlN, which requires further disposal. Efficient detoxification and large-scale high-value utilization of secondary aluminum dross can not only solve the potential environmental risks caused by hazardous solid waste stockpiling, but also realize the maximum utilization of aluminum resources, which is of great significance to the ecological environment and the healthy development of the aluminum industry. It is recommended that the secondary aluminum dross be resourced according to its salt content and categorized for disposal. Meanwhile, the utilization of secondary aluminum dross in high value-added fields such as calcium aluminate refining slag, ceramic heat storage ball and refractory materials is strengthened.