Respirometry studies of bioleaching of low-grade chalcopyrite ore using six acidophilic strains

Respirometry was used to study the growth and activity of six pure cultures of acidophilic bioleaching strains grown on a concentration series of low-grade chalcopyrite ores under various pH conditions. Sulfolobus metallicus, Acidithiobacillus ferrooxidans, Acidianus brierleyi and Leptospirillum ferriphilum were able to grow on a very low-grade ore (equivalent to 0.1% Cu content). However, the two sulphur-oxidising bacteria Acidithiobacillus caldus and Acidithiobacillus thiooxidans grew poorly on the low-grade ore. Growth rates of all strains, except for perhaps S. metallicus at highest ore grades, displayed growth that was limited by substrate availability on this low-grade ore (0.5% Cu content in the ore). The decrease in solution pH from 3.0 to 1.0 enhanced both the cell growth and Cu dissolution.

► Growth of bioleaching strains on low-grade chalcopyrite was studied. ► CO2 consumption indicated growth kinetics of autotrophic bioleaching strains. ► Growth of most strains was limited by substrate availability. ► Minimum ore grade required for growth was 0.1–0.3% Cu depending on the strain. ► Decrease in solution pH enhanced cell growth and Cu dissolution.