Solvent Extraction of Iron in Zinc Hydrometallurgy

This paper presents an alternative method for removing iron from zinc sulfate process liquors through solvent extraction, rather than the conventional precipitation of jarosite, goethite, or hematite. The aim is to integrate leaching and solvent extraction steps in a hydrometallurgical zinc plant without the necessity for external alkali addition. The process begins with leaching zinc from solid zinc calcine using an organic solution containing an acid liquid cation exchanger, resulting in the loading of the organic phase with organic zinc salt through direct interaction with zinc oxide. The resulting residue is transitioned to a hot acid leach circuit where the remaining zinc oxide and zinc ferrites dissolve, producing an aqueous zinc and iron sulfate solution. In subsequent solvent extraction, iron is exchanged with zinc from the organic phase. The use of the commercial carboxylic acid Versatic 10 demonstrates high efficiency for this integrated leaching and solvent extraction process, yielding high-purity iron oxide precipitated from the organic phase while allowing for the regeneration of the acid for reuse in leaching.