Research and Development on Utilization of Steelmaking Slag and Recovery of Valuable Slag Elements

In Japan, approximately 14 million tons of steelmaking slag were generated in FY2023. Owing to its excellent mechanical properties, steelmaking slag has been primarily used in construction materials, such as roadbeds. However, these applications are predicted to decrease, making it necessary to find new ways to utilize the slag. Steelmaking slag contains many components beneficial for plant growth, such as calcium, silicon, iron, and phosphorus. Technologies are being developed for marine and agricultural applications, including seabed restoration and yield improvement in rice cultivation. Laboratory-scale experiments have confirmed the elution of these components, the propagation of organisms, and the promotion of plant growth. Some of these findings have begun to be implemented in practical applications through on-site testing. At the same time, since steelmaking slag contains significant amounts of essential elements for society, such as manganese and phosphorus, research is being conducted to selectively recover these valuable elements. In particular, various separation methods have been reported for phosphorus recovery, taking advantage of the physical and chemical properties of the mineral phases in steelmaking slag. These methods include flotation separation, magnetic separation, capillary action, redox reactions, solution reactions, and combined processes. This report summarizes the current status of steelmaking slag and the progress of research and development for its utilization.