Phosphorous Recovery from Ca2SiO4–Ca3P2O8 Solid Solution By Carbothermic Reduction

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Steelmaking slag is considered as a promising phosphorus resource as it contains the phosphorus in a condensed phase of Ca2SiO4–Ca3P2O8 solid solution (C2S–C3P)ss. In the present study, the carbothermic reduction of (C2S–40 mol% C3P)ss at 1573 K was carried out to understand the phosphorus removal mechanism by varying reduction temperature, external gas flow rate, amount of graphite, and concentration of Ca3P2O8 in (C2S–C3P)ss. The carbothermic reduction proceeded as a zero-order reaction when the temperature was 1573 K, despite the P2O5 concentration decrease with the reduction time. At temperatures less than 1473 K, the reduction did not occur. Based on the XRD analysis of the reduced (C2S–C3P)ss samples, it was found that carbothermic reduction of the C2S–C3P solid solution proceeded by the decomposition of the C2S–C3P solid solution into CaO and C2S with the removal of phosphorus, but not by a uniform decrease of the phosphorous throughout the C2S–C3P solid solution. The overall reduction degrees were found to be independent of the reduction rate (zero-order reaction) and the P2O5 concentration in the (C2S–C3P)ss. From these independencies, the rate-controlling step of the carbothermic reduction of (C2S–C3P)ss was concluded to be the Boudouard reaction. Graphical Abstract: [Figure not available: see fulltext.].

Original languageEnglish
Pages (from-to)459-469
Number of pages11
JournalJournal of Sustainable Metallurgy
Issue number2
Publication statusPublished - 2021 Jun


  • CaSiO–CaPO solid solution
  • Carbothermic reduction
  • Lattice parameter
  • Phosphorus recovery
  • Yellow phosphorous

ASJC Scopus subject areas

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


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