The detoxification potential of ferric ions for bioleaching of the chalcopyrite associated with fluoride-bearing gangue mineral.

Fluoride toxicity to microorganisms was a predominant factor contributing to the failure of a commercial scale bioleach heap. An integrated control strategy for fluoride complexation without jarosite generation by stepwise adding ferric ions was first proposed to enable the bioleaching of the chalcopyrite associated with fluoride-bearing gangue mineral by Acidithiobacillus ferrooxidans. Chemical speciation calculation revealed that with the presence of Fe, the concentration of the main lethal fluoride to microorganism, HF, decreased dramatically. The pure culture study showed that the detrimental effect of fluoride on microorganism was eliminated by increasing the molar ratio of Fe/F to 3:1. Furthermore, chalcopyrite bioleaching experiment revealed the minimum Fe/F molar ratio that enabled the bioleaching was 6:1. Stepwise addition was an effective way to promote a balanced system and avoid the formation of jarosite caused by the excessive Fe. Above all, the introduction of Fe is a feasible method for reducing the fluoride toxicity during the bioleaching of chalcopyrite, shedding light on the industrial applications.