How is iron removed from zinc sulfate solution during zinc processing?

In the context of zinc processing, the removal of iron from the zinc sulfate solution is a critical first stage of purification required to ensure the efficiency of the subsequent electrolysis process.1

Iron is removed from the solution as a solid residue in one of the following forms:1

• Jarosite: A basic ferric sulfate.1
• Goethite: An iron oxide mineral.1
• Hematite: An iron oxide mineral.1

This removal process is essential because the presence of impurities in the electrolyte can lower the hydrogen overvoltage, which would otherwise interfere with the successful deposition of zinc onto the cathode. Once the iron has been removed, the solution undergoes a second stage of purification involving cementation with zinc dust to eliminate other metallic impurities, such as copper, nickel, cadmium, cobalt, and germanium.1