Effect of Cu2+ ions on bioleaching of marmatite

The effect of Cu2+ ions on bioleaching of marmatite was investigated through shake leaching experiments. The bacteria inoculated are a mixed culture of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Lepthospirillum ferrooxidans. The results show that zinc is selectively leached, and the addition of appropriate content of Cu2+ ions has positive effect on the bioleaching of marmatite. SEM and EDX analyses of the leaching residue reveal that a product layer composed of iron sulfide, elemental sulfur and jarosite forms on the mineral surface. The biooxidation of elemental sulfur is catalyzed by the Cu2+ ions, which eliminate the barrier to bioleaching of marmatite and keep low pH value. With the addition of 0.5 g/L Cu2+ ions, the maximum zinc extraction rate reaches 73% after 23 d at the temperature of 30 °C with the pulp density of 10%, while that of iron is only about 10%.