Phosphorus removal from steelmaking slag by selective leaching in the steel pickling waste liquor

• Published in: Minerals engineering 2024-11, Vol.218, p.109051, Article 109051
• Main Authors: Yu, Yao-hui, Du, Chuan-ming, Wang, Jian-guo, Lu, Jian-qiang
• Format: Article
• Language: English
• Subjects: Comprehensive utilization; Leaching; P removal; Steel pickling waste liquor; Steelmaking slag
• ISSN: 0892-6875
• DOI: 10.1016/j.mineng.2024.109051

[Display omitted] •Leaching of P from steelmaking slag in the steel pickling waste liquor was feasible.•FePO4 precipitated from leachate when the Fe3+ content in the SPWL was high.•Lowering pH and Fe3+ content contributed to the selective leaching of P.•After leaching in the SPWL, a P-removal residue was obtained. Steelmaking slag and steel pickling waste liquor (SPWL) are two kinds of by-products in steel plants. The existence of phosphorus (P) in steelmaking slag is the main factor affecting its reuse within the steelmaking process. To remove P from steelmaking slag with a low-cost method, selective leaching was proposed by using SPWL as a leaching agent. SPWL generally contains a small amount of Fe3+ ions, and thus the effect of Fe3+ content in SPWL on the dissolution behavior (especially P element) of steelmaking slag was investigated, as well as the pH value and steelmaking slag type. The dissolution ratios of P from various slags in the SPWL containing 500 ppm Fe3+ exceeded 95 % at pH 1.5 while those of Fe, Mn, and Al were very low, exhibiting satisfied selective leaching of P. Increasing pH value and Fe3+ content (in SPWL) resulted in a decreasing P dissolution ratio while exerting an insignificant effect on the dissolution of other elements. The FeHPO4+ was predicted as the predominant species during leaching and the transformation of FeHPO4+ to FePO4 could be present. When the SPWL containing 800 ppm Fe3+ was used, FePO4 was observed in the residues after leaching at pH 2.0, resulting in a worse removal of P from slag. However, the residues including massive valuable components had an extremely low P content after leaching in the SPWL containing 500 ppm Fe3+ at pH 1.5, which can be used as a flux in the metallurgical process. To ensure a high P removal rate from steelmaking slag and to prevent FePO4 precipitation during leaching, a relatively low pH and Fe3+ content in the SPWL are necessary.