Abstract:The changes of pH, redox potential, concentrations of soluble iron ions and Cu²⁺ with the time of  bioleaching chalcopyrite concentrates by acidithiobacillus ferrooxidans were investigated under the different conditions of initial total-iron amount as well as mole ratio of Fe(III) to Fe(II) in the solutions containing synthetic extracellular polymeric substances (EPS). When the solution potential is lower than 650 mV (vs SHE), the inhibition of jarosites to bioleaching chalcopyrite is not vital as EPS produced by bacteria can retard the contamination through flocculating jarosites even if concentration of Fe(III) ions is up to 20 g/L but increases with increasing the concentration of Fe(III) ions; jarosites formed by bio-oxidized Fe³⁺ ions are more easy to adhere to outside surface of EPS space on chalcopyrite; the EPS layer with jarosites acts as a weak diffusion barrier to further rapidly create a high redox potential of more than 650 mV by bio-oxidizing Fe²⁺ ions inside and outside EPS space into Fe³⁺ ions, resulting in a rapid deterioration of ion diffusion performance of the EPS layer to inhibit bioleaching chalcopyrite severely and irreversibly.

Key words: extracellular polymeric substances; chalcopyrite; bioleaching; jarosites; redox potential