Effect of Nitrate Ions on Acidithiobacillus ferrooxidans-Mediated Bio-oxidation of Ferrous Ions and Pyrite.

Exploring the effects of nitrate ions (NO) on the bio-oxidation of Fe and pyrite will help reveal the actual mechanism of acid mine drainage (AMD) production. Long period shaking flask experiments were carried out in order to assess the effect of NO on the Acidithiobacillus ferrooxidans LX5 (A. ferrooxidans LX5)-mediated bio-oxidation of Fe and pyrite. In Fe bio-oxidation systems, A. ferrooxidans LX5 had stronger Fe oxidation capabilities in a NO-loaded solution than in a NO-free solution after 24 days, and the Fe bio-oxidation capacity of A. ferrooxidans LX5 acclimatized in solutions containing low concentrations (8.2-32.9 mmol/L) of NO was greater than when it was acclimatized in high NO concentration solutions (49.4-65.8 mmol/L). In pyrite bio-oxidation systems, in comparison with the system without NO, pyrite bio-oxidation efficiency was significantly increased when the NO concentration in the system was 8.2-16.5 mmol/L, and that the pyrite bio-oxidation efficiency in the system containing 8.2 mmol/L of NO was greater than that for the system with 16.5 mmol/L of NO. The pyrite bio-oxidation efficiency was inhibited when the NO concentration was above 32.9 mmol/L. The results from this study can be used to reveal the actual control behavior of NO on AMD production.