Intensification of Zinc Bioleaching from a Zinc–Iron Bearing Ore by Condition Optimization and Adding Catalysts

Zinc bioleaching from sphalerite associated with pyrite ore using Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidant was studied. The ore containing 3.4 wt% zinc and in some experiments its combination with sphalerite concentrate was prepared. The effect of culture media, pH, Fe2+ iron concentration, and the addition of different materials including shredded newspaper, starch, and sugar as a catalyst on the zinc bioleaching were evaluated. It was found that 9 K media, pH of 1.8, and 10 g L−1 Fe2+ iron concentration were optimum conditions. The catalysts acted as an electron acceptor for Fe3+ iron reduction. The amount of zinc bioleaching was obtained 88% for the ore and 95% for the second sample at the optimum pH of 1.8 in 18 days. The addition of starch and shredded newspaper increased the bioleaching rate of zinc. Also, the bioleaching time was decreased from 18 days to 10 and 13 days in the presence of shredded newspaper and starch, respectively.