Mechanism of bioleaching chalcopyrite by Acidithiobacillus ferrooxidans in agar-simulated extracellular polymeric substances media

Abstract

The mechanism of leaching chalcopyrite by Acidithiobacillus ferrooxidans (A. ferrooxidans) in agar-simulated extracellular polymeric substances (EPS) media was investigated. The results indicate that bacterial EPS can release H⁺ and concentrate Fe³⁺; Fe²⁺ is movable between agar-simulated EPS phase and bulk solution phase, but it is difficult for Fe³⁺ to move due to its hydroxylation and EPS complex action; A. ferrooxidans first prefer Fe²⁺ as energy to metabolize compared with chalcopyrite, and a suitable simulated EPS environment for bacterial living is at about pH 1.8; the iron precipitates and jarosites formed by a lot of biologically oxidized Fe³⁺ cover the simulated EPS easily and form an impermeable deposit acting as a limited barrier of ion transport that attenuates the aggressiveness of the bioleaching attack. The EPS layer blocked by iron precipitates or jarosites is responsible for the chalcopyrite passivation.

Keywords

Acidithiobacillus ferrooxidans / chalcopyrite / agar-simulated EPS media / bioleaching / mechanism

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