Biofilm forming and leaching mechanism during bioleaching chalcopyrite by Thiobacillus ferrooxidans

摘要

The mechanism of attachment and leaching of thiobacillus ferrooxidans (T. f.) on chalcopyrite were studied. The shaking flasks with bacteria were observed by SEM. The process of T. f attached to the surface of the mineral sample and the biofilm forming were described. The promoting role of the biofilm for bioleaching was discussed. The existence of Fe~(2+) in the exopolysaccharide layer of T. f was demonstrated by EM (electronic micro-scope) cell-chemistry analysis. These results show that under the proper growth condition of bacteria, bioleaching of chalcopyrite results in the formation of complete biofilm after 2 - 3 weeks. There are iron ions in the Outer layer polymer of T. f., which provides the micro-environment for themselves, and can guaruntee the energy needed for the bacteria growth in the biofilm. At the same time, Fe~(3+) ions produced oxidize sulfide which brings about the increase of both growth rate of the bacterial and leaching rate of sulfide minerals.