Biochar-induced alterations in Acidithiobacillus ferrooxidans activity and its impact on Cd(II) and As(III) adsorption from acid mine drainage

Due to continuing mining activities, Cd(II) and As(III) contamination in acid mine drainage (AMD) has become a major environmental challenge. Currently, there is increasing focus on the use of biochar to mitigate AMD pollution. However, the impact of biochar on the process of Fe(II) oxidation by Acidithiobacillus ferrooxidans (A. ferrooxidans) in AMD systems has not been determined. In this study, we investigated the effects of introducing biochar and biochar-leachate on Fe(II) biooxidation by A. ferrooxidans and on the removal of Cd(II) and As(III) from an AMD system. The results showed that the biochar-leachate had a promoting effect on Fe(II) biooxidation by A. ferrooxidans. Conversely, biochar inhibited this process, and the inhibition increased with increasing biochar dose. Under both conditions (c(A. ferrooxidans) = 1.4 × 107 copies mL–1, m(FeSO4·7H2O):m(biochar) = 20:1; c(A. ferrooxidans) = 7.0 × 107 copies mL–1, m(FeSO4·7H2O):m(biochar) = 5:1), the biooxidation capacity of A. ferrooxidans was severely inhibited, with Fe(II) oxidation efficiency reaching a value of only 20