Selective Leaching of P from Steelmaking Slag in Sulfuric Acid Solution

Chuanming Du, Xu Gao, Shigeru Ueda, Shinya Kitamura

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


Steelmaking slag contains considerable quantities of valuable elements such as P and Mn; however, its intrinsic value has not been fully exploited. In steelmaking slag, P is primarily distributed in the 2CaO·SiO2–3CaO·P2O5 solid solution, which can be dissolved readily in the aqueous solution compared with other phases. To separate and recover P from steelmaking slag, selective leaching of the P-containing solid solution was proposed. In this study, sulfuric acid was used as the leaching agent to reduce production costs. The effects of the cooling method of the molten slag, valence of Fe in slag, pH, and particle size on the dissolution characteristic of steelmaking slag were investigated. To achieve an improved selective leaching of P, the molten slag should be oxidized into the Fe2O3-containing slag and cooled slowly. As the pH decreased, the dissolution of the slag was promoted, resulting in a higher extraction efficiency of P. The majority of the solid solution was separated without dissolving the Fe-rich magnesioferrite at pH 3, indicating an improved selective leaching of P. Through selective leaching, the P2O5 content in the residue decreased significantly. If the formation of CaSO4 can be suppressed, this residue has the potential to be reused in the steel plant. Decreasing the particle size increased the dissolution rate of slag. A shrinking core model was used to describe the kinetics of slag dissolution. The dissolution of P in the sulfuric acid solution was controlled by diffusion in the residue layer.

Original languageEnglish
Pages (from-to)594-605
Number of pages12
JournalJournal of Sustainable Metallurgy
Issue number4
Publication statusPublished - 2019 Dec 1


  • P recovery
  • P-containing solid solution
  • Selective leaching
  • Steelmaking slag

ASJC Scopus subject areas

  • Environmental Science (miscellaneous)
  • Mechanics of Materials
  • Metals and Alloys


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