A review on the P enrichment and recovery from steelmaking slag: Towards a sustainable P supply and comprehensive utilization of industrial solid wastes

Phosphorus (P) is one of the desirable nutrient elements for the growing of crops and is a non-renewable resource. The over-exploitation of high-grade phosphate rocks makes finding alternative P sources urgent for a sustainable and stable P supply. Steelmaking slag has been considered a potential P source due to its huge production and the increasing P content in slag with the utilization of low-grade iron ores. If the efficient separation of P from steelmaking slag is achieved, the obtained P can be used as the raw material for phosphate products, and the P-removal steelmaking slag can be reused as a metallurgical flux in steel plants, realizing the comprehensive utilization of steelmaking slag. To better understand the separation method and mechanism of P from steelmaking slag, this paper reviews: (1) the enrichment mechanism of P in steelmaking slag, (2) the methods of the P-rich phase separation from slag and P recovery, and (3) facilitating the enrichment of P in the mineral phase by cooling treatment and modification. Furthermore, some industrial solid wastes were selected as modifiers for steelmaking slag, which not only provided several valuable components but also significantly reduced treatment costs. Hence, a collaborative processing of steelmaking slag and other P-bearing industrial solid wastes is proposed, providing a new solution for P recovery and the comprehensive utilization of industrial solid wastes, achieving the sustainable development of steel and phosphate industries.