A review on lead slag generation, characteristics, and utilization

Lead slag is produced by the primary and secondary lead industry. The large amount of lead slag discharge causes environmental problems. Reducing the toxicity and increasing utilization of lead slag are important measures to solve the negative impact of lead slag on the environment. Here, we review the lead slag physical and chemical characteristics, as well as environmental impacts. This review focuses on the utilization of lead slag: recovery of metals and used for construction materials. Various processes for metal recovery including pyrometallurgical, hydrometallurgical, and bioleaching methods are summarized. Coal-based direct reduction is a typical pyrometallurgical technology for recovering metals from lead slag, which has the characteristics of high recovery efficiency, high energy consumption and suitable for industrial production. Chloride, acetic acid, and HNO3-based leaching systems are mainly used in hydrometallurgy of lead slag. The waste reagents and residues produced in hydrometallurgy process inevitably increase the environmental risk. Bioleaching is an environmentally friendly technology, but it is currently limited to laboratory scale. We also discuss the utilization of lead slag in construction materials. The use of lead slag in road construction and concrete will cause environmental risk of leaching toxic elements. The utilization rate of lead slag in cement clinker is extremely low. Geopolymers and glass-ceramics have good stabilization effect on toxic elements. However, the extensive use of alkaline activators limits the large-scale application of geopolymers. High energy consumption of glass-ceramics should be considered. Finally, the limitations and prospects for future research of lead slag utilization are also considered.