Detection and analysis of attached microorganisms on the mineral surface during bioleaching of pure chalcopyrite with moderate thermophiles

Moderate thermophiles were used to bioleach pure chalcopyrite and showed good performance of copper extraction in the stirred tank reactor. The attached microorganisms on the mineral surface were detected by atomic force microscope (AFM). The result showed that the attached cells could produce extracellular polymeric substances (EPS) rapidly. However, it was difficult to reduce or eliminate the EPS once it was produced, and thus the large amount of EPS at the later stage of bioleaching would mediate the formation of jarosite and block the continuous copper extraction. Furthermore, the number of attached cells on the mineral surface was enumerated as a function of time and the variation was rather different from that of free cell density in the bioleaching solution.

► The attached microorganisms on the chalcopyrite surface during bioleaching were detected by AFM.
► The bioleaching cells preferred to attach onto the mineral surface and produce EPS rapidly.
► The amount of EPS increased rapidly and could achieve to the maximum in only 10 days.
► The variation trend of attached cell amount was rather different from that of free cell density.