Bioleaching of arsenic and heavy metals from mine tailings by pure and mixed cultures of Acidithiobacillus spp.

Microbial removal of heavy metals in mine tailings from a Cu–Ag mine in the Philippines was investigated. Effect of bacterial strains on bioleaching and fractionation of heavy metals were also studied. Single and mixed cultures of Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans were used separately to compare efficiency of metal solubilization. The results showed that mixed cultures were more efficient than each bacterium for Cu and As, while A. ferrooxidans demonstrated faster extraction efficiency for Mn and Zn. The results of sequential extraction for residues indicated that pure bacteria and mixed cultures mediated occurrence mode of heavy metals in different ways.