Abstract:The effects of several variables on the bioleaching of marmatite with pure L. ferrooxidans were investigated. The results show that zinc extraction increases with the decrease of pulp density. Adjusting pH to1.6 during the bioleaching process has a positive effect to the dissolution of marmatite. External addition of Fe³⁺ ions accelerates the bioleaching, while the concentration of additional Fe³⁺ over 2.5 g/L weakens the acceleration effect due to the inhibition effect on bacteria growth and the promotion of jarosite production. The electrochemical measurements were used to make further understanding on the dissolution of marmatite with and without additional Fe³⁺ in the presence of L. ferrooxidans. The experimental data illustrate that additional Fe³⁺ ions could increase the corrosion current density, which is favorable to zinc extraction. The EIS spectra show that rate-limiting step does not change when Fe³⁺ is added.

Key words: bioleaching; marmatite; electrochemical measurements; L. ferrooxidans