Acid-leaching separation of phosphorus from the BOF slag modified with Al2O3

Abstract

Basic oxygen furnace (BOF) slag, a main byproduct of steelmaking, contains large quantities of beneficial components. Its recycling inside the metallurgical process is considered as the optimal utilization method; however, the existence of P2O5 makes this goal difficult to achieve. In this study, to achieve efficient separation of P, the BOF slag was modified by Al2O3 addition and the dissolution behavior of P from slag was investigated in the HCl solution. The results showed that the dissolution ratio of P reached 86.3 % by Al2O3 modification, which also suppressed the dissolution of valuable metal elements from BOF slag resulting from the formation of insoluble Ca2(Fe1−xAlx)2O5 and MgFeAlO4 phases. The thermodynamic analysis shows that Fe3+ ions are the most easily combined with phosphate to form precipitation, leading to a low P dissolution ratio. It demonstrates that suppressing the dissolution of Fe3+ ions is the key to separating P from BOF slag. After leaching at pH 1, residue D contains 42.75 % Fe2O3, 34.08 % CaO, and only 0.17 % P2O5 content, which can be reused as a flux in steel plants, achieving the high effective utilization of steelmaking slag.