Changes in key chemical parameters in different deficient bioleaching systems.

(A): pH; (B): Eh; (C): Sulfate ions; (D): Ferrous ions; (E): Ferric ions; (F) Planktonic and attached biomass; (G) μx of planktonic and attached cells. Note: the pH of leachate during bioleaching was measured before the pH-1.5 adjustment by 6 M HCl every two days.