Interaction mechanism of Cu2+, Fe3+ ions and extracellular polymeric substances during bioleaching chalcopyrite by Acidithiobacillus ferrooxidans ATCC2370

The extracellular polymeric substances (EPS) of Acidithiobacillus ferrooxidans ATCC 23270, and iron and copper enclosed in EPS were extracted by ultrasonication and centrifugation methods to determine the interaction mechanism of Cu2+, Fe3+ and EPS during bioleaching chalcopyrite. Generally, Cu2+ ions can stimulate bacteria to produce more EPS than Fe3+ ions. The mass ratio of Fe3+/Cu2+ enclosed in EPS decreased gradually from about 4:1 to about 2:1 when the concentration of Cu2+ ions increased from 0.01 to 0.04 mol/L. The amount of iron and copper bound together by EPS in ferrous-free 9K medium containing 1% chalcopyrite was about 2 times of that in 9K medium containing 0.04 mol/L Cu2+ ions. It was inferred that the EPS with jarosites on the surface of chalcopyrite gradually acted as a weak diffusion barrier for Cu2+, Fe3+ ions transference during bioleaching chalcopyrite.