Efficient extraction of phosphate from dephosphorization slag by hydrochloric acid leaching
2022
Du, Chuan-ming | Yu, Yao-hui | Jiang, Liu-dong | Yu, Jing-kun
Phosphorus is an indispensable nutrient element in agriculture and its reserves are limited. To secure a sustainable supply of phosphorus, phosphate recovery from dephosphorization slag generated in steelmaking was considered a promising solution. In this study, acid leaching was adopted to separate the P-concentrating solid solution from dephosphorization slag. Selective leaching of P from slags with various basicity in the hydrochloric acid solution and chemical precipitation of phosphate ions in the leachate were investigated. Increasing slag basicity facilitated the enrichment of P₂O₅. Large amounts of Ca, Si, and P were leached from slag, whereas the leaching of Fe was negligible. The leaching efficiency of P increased with slag basicity. At pH 3, the leaching efficiency of P from slag with high basicity reached 96.8% while that of Fe was nearly zero. Almost all the P-concentrating solid solution was dissolved without significant dissolution of the Fe-bearing matrix phase and magnesioferrite. After leaching, the residue containing 57.8% Fe₂O₃ can be reutilized as a metallurgical feedstock. Through chemical precipitation, a precipitate containing 35.1% P₂O₅ was recovered from the leachate, which can be used as a phosphate fertilizer. The total recovery efficiency of P from dephosphorization slag in this process reached 95.8%.
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