Effects of forced aeration on community dynamics of free and attached bacteria in copper sulphide ore bioleaching

In order to obtain better bioleaching efficiency, bacterial community dynamics and copper leaching with applying forced aeration were investigated during low-grade copper sulphide bioleaching. Results illustrated appropriate aeration yielded improved bacteria concentrations and enhanced leaching efficiencies. The highest bacteria concentration and Cu²⁺ concentration after 14-day leaching were 7.61×10⁷ cells•mL^-1 and 704.9 mg•L^-1, respectively, when aeration duration was 4 h•d^-1. The attached bacteria played a significant role during bioleaching from day 1 to day 7. However, free bacteria dominated the bioleaching processes from day 8 to day 14. This is mainly caused by the formation of passivation layer through Fe³⁺ hydrolysis along with bioleaching, which inhibited the contact between attached bacteria and ore. Meanwhile, 16S rDNA analysis verified the effect of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidanson on bioleaching process. The results demonstrate the importance of free and attached bacteria in bioleaching.