Isolation of Acidithiobacillus ferrooxidans strain Z1 and its mechanism of bioleaching copper from waste printed circuit boards

BACKGROUND Waste printed circuit boards (PCBs) are solid hazardous materials and may pose serious problems to the environment and human health. Bioleaching has been used to recover metal from waste PCBs. This study aims to isolate an effective Acidithiobacillus ferrooxidans strain and investigate its bioleaching mechanism during the process. RESULTS An A. ferrooxidans strain Z1 with average 0.2307 g L−1 h−1 ferrous ion oxidation rate was isolated from self-prepared mixed culture of acidophilic bacteria. After 7 days, 96% of the copper was extracted from metal concentrates by A. ferrooxidans at an initial Fe2+ concentration of 12 g L−1. Protons produced by the ionization of sulfuric acid and the hydrolysis Fe3+ played only a slight role in the extraction of copper. Dialysis bag experiments show 81.43% of copper was leached out by bioleaching without dialysis bag compared with 47.90% in the encapsulated bioleaching system. CONCLUSION An A. ferrooxidans strain with effective ferrous ion oxidation rate and high copper leaching efficiency was isolated. The extraction of copper was mainly through the indirect oxidation process via ferric ions biogenerated by A. ferrooxidans. Both contact and non-contact mechanisms led to the dissolution of copper from waste PCBs. © 2014 Society of Chemical Industry