Effect of Fe2+/T.Fe Ratio on the Dissolution Behavior of P from Steelmaking Slag with High P2O5 Content
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Steelmaking slag with high P2O5 content is generated when using high-P iron ores. This slag primarily consists of a CaO–SiO2–FeO–Fe2O3–P2O5 system and is regarded as a potential P source. To separate and recover P, selective leaching of the P-concentrated solid solution from steelmaking slag was employed. To determine the appropriate slag composition for selective leaching, it is necessary to clarify the influence of the molar ratio of Fe2+ to total Fe (Fe2+/T.Fe) on the dissolution behavior of steelmaking slag. This study found that as the Fe2+/T.Fe ratio in slag increased, the P2O5 content in the solid solution decreased, while the mass fraction of the solid solution increased; therefore, most of the P was still distributed in the solid solution. During leaching, citric acid showed an enhanced capacity to dissolve P from slag. When nitric acid is used as leaching agent, leaching should be conducted at a lower pH to achieve a leaching performance similar to that of citric acid. Because the presence of FeO in the solid solution deteriorated its dissolution, the dissolution ratio of P decreased significantly with the increasing Fe2+/T.Fe ratio in slag. By contrast, the dissolution of Fe was promoted. This was attributed to a higher dissolution of the CaO–SiO2–FeO matrix phase compared with the CaO–SiO2–Fe2O3 matrix phase. Therefore, to achieve a better selective leaching of P, steelmaking slag should be oxidized to lower the Fe2+/T.Fe ratio below 0.1.
KeywordsHigh-P iron ores Steelmaking slag Fe2+/T.Fe Selective leaching C2S–C3P solid solution
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On behalf of all authors, the corresponding author states that there is no conflict of interest.
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