Comparative study on the bioleaching, biosorption and passivation of copper sulfide minerals

The bioleaching, biosorption and passivation of five different types of copper sulfide minerals (djurleite, bornite, covellite, pyritic chalcopyrite, and porphyry chalcopyrite) by Acidithiobacillus ferrooxidans (At.f LD-1) were investigated in this paper. The bioleaching experiments showed that copper extraction followed the order djurleite > bornite > pyritic chalcopyrite > covellite > porphyry chalcopyrite. The bacterial adsorption experiments indicated that the bacterial adsorption quantity onto the five copper sulfide minerals had the same order as that of copper extraction. SEM analysis showed that bacterial distribution on the djurleite, bornite, and covellite was uniform and that on the pyritic chalcopyrite and porphyry chalcopyrite was uneven (distributed as continuous chain structure). Zeta potential analysis showed that the zeta potentials of copper sulfide minerals after interaction with At.f LD-1 cells changed to varying degrees. The variation degree of the zeta potentials of the five copper sulfide minerals showed the same order as the bacterial adsorption quantity on the five copper sulfide minerals. The main passivation layers on the residues of djurleite and bornite were both jarosite, and that the passivation layers on the residues of covellite, pyritic chalcopyrite, and porphyry chalcopyrite were Cu4S11, S8, and Cu4Fe2S9, respectively. The inhibition ability of passivation layers followed the order Cu4Fe2S9 > Cu4S11 > S8 > jarosite.