Removal of Mn Ions by Biological Co-precipitation of Fe Ions

The behaviors of manganese ions during biological precipitation of iron ions by Acidithiobacillus ferrooxidans was investigated to remove the Mn ions from acid mine drainage. The effect of initial Fe2+ ion concentration with 900 g.m(-3), 4500 g.m(-3), and 9000 g.m(-3) on the removal of Mn ions was examined by measuring pH, ORP, and the concentrations of Fe and Mn ions. In the experiments with the Fe2+ concentration with 4500 g.m(-3) and 9000 g.m(-3), pH increased and then decreased by the oxidation of Fe2+ and the precipitation of Fe ions. In all solutions, ORP increased to 630 mV, and Fe concentration decreased with Fe precipitation. Adding NaOH increased the amount of Fe precipitate and the Mn removal ratio in the early stage but there was no significant effect as the experiments were proceeded.