Feasibility of Bioaugmentation with Iron/Sulfur Oxidizing Acidophiles to Enhance Copper Bioleaching from a Flotation Copper Ore

The feasibility of one strategy of bioaugmentation was assessed to enhance copper extraction from chalcopyrite. Bioaugmentation consisted of the re-addition of one iron/sulfur oxidizing acidophile (Acidithiobacillus caldus, Ferroplasma thermophilumorLeptospirillum ferriphilum) into the early stage (on the 5thday) of the bioleaching system. The strain selection and inoculum concentration of bioaugmentation were separately investigated by comparing changes in the bioleaching performance and leached solid residues. Results indicated that bioaugmentation with three augmented strains synergistically promoted the total microbial growth and increased the cell numbers, and then accelerated the iron/sulfur oxidation, thereby catalytically regenerated the copper leaching agents of Fe3+and H+compared to the unamended control. Finally, an enhancement in copper extraction was detected and moreover positively correlated with the introducing cell numbers. Particularly, re-addition ofL.ferriphilumon the 5thday showed the best improvement in copper leaching, which remarkably shortened the incubation time (12 days) of almost full copper extraction while only 85.8% of copper was leached after 24 days in the control. Therefore, bioaugmentation could be a useful bio-remedy to improve the bioleaching kinetics and level of copper ore.