Acid Leaching for Phosphorus Separation from the Co-Processing of Dephosphorization Slag and Basic Oxygen Furnace Slag: Kinetics Investigation

Abstract

To realize efficient P removal and resource utilization of steelmaking slag, a synthetic slag with appropriate basicity was produced by co-processing the practical dephosphorization slag and basic oxygen furnace slag. The selective leaching behavior and dissolution kinetics of P were investigated. The results indicated that the P dissolution efficiency and reaction rate were significantly influenced by the variety in stirring rate and pH. However, the decreasing solid/liquid ratio and particle size can significantly enhance the reaction rate while exerting a slight impact on the P dissolution efficiency. The leaching temperature had less influence on both P dissolution efficiency and reaction rate. Under the optimal leaching conditions, the leaching reaction of the P-condensed phase primarily occurred within the initial 3 minutes, and finally, the P dissolution efficiency reached 87.5%, with an extremely low Fe dissolved amount. After leaching, the Fe-rich residue, comprising large amounts of Fe2O3, MgO, and MnO, can be reutilized as raw material or flux agents in steel plants. Furthermore, it was found that the selective leaching of P was controlled by diffusion through the product layer, with the apparent activation energy of 5.02 kJ/mol. The semi-empirical equation has been established.

Keywords: phosphorus removal, leaching kinetics, De-P slag, BOF slag, comprehensive utilization