| Zinc-ferrite is an undesired compound which is unavoidably formed during the roasting process of marmatite ore and its low solubility in dilute sulfuric acid is one of the serious problem reducing the zinc recovery in the field of hydrometallurgy. The mechanism of zinc-ferrite formation, its leaching efficiency in various conditions and the effectiveness of partial reduction with carbon monoxide to the recovery rate were investigated for synthetic zinc-ferrite. Similar investigations were carried out for the roasted calcine from marmatite ores. The rate of zinc-ferrite formation closely followed Tammanns law and it was found that zinc oxide diffuse through the zinc-ferrite layer, reacting further with ferric oxide. The overall leaching rate of zine-ferrite in dilute sulfuric acid was inversely proportional to the particle size, therefore it was concluded that the roasting should be done in lower temperatures and shorter period as possible. By partial reduction of zinc-ferrite by carbon monoxide under 800℃, the ferrite was decomposed to zinc oxide and magnetite or wu¨stite, suggesting that the reduction procedure followed immediately after the roasting is effective to increase the zinc recovery. |
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