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

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