Leaching and Purification

Leaching and Purification

Leaching Zinc oxide (called Calcine) is leached by electrolyte containing sulphuric acid in reactors.

ZnO + H2SO4 = ZnSO4 + H2O

The solids remaining from the leaching process consist primarily of zinc iron compounds called ferrites. These solids are removed from the leaching process by filtering in a high pressure filter. The filtered cake is conveyed to the Dryer prior to export.

The solution containing the zinc sulphate is pumped to the Purification Plant. The purification process removes minor elements from the zinc sulphate solution prior to electrolysis. The purification is achieved by the addition of zinc dust (produced in the melting and casting plant), promoting cementation reactions such as

M2+ (liquid) + Zn (solid) = M (solid) + Zn2+ (liquid).

As a result, impure metals are converted to the solid form and separated from the zinc sulphate solution by filtering.

Solution is cooled in cooling towers to precipitate gypsum and the clear purified solution is then pumped to the Electrolysis Plant.

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