Abstract: The change in the iron ion concentration, pH and Eh in the Fe³⁺ oxidization and bio-oxidation process of pyrite is studied by using Acidithiobacillus ferrooxidans. The results show that as Fe³⁺ will rapidly be consumed, it has a low oxidation rate for pyrite while the presence of bacteria can continuously oxidize Fe²⁺ into Fe³⁺, thus evidently accelerating the pyrite oxidation rate. Therefore, bio-oxidation has higher efficiency. Based on the indirect function mechanism and in light of the change law of pH and Eh in the bio-oxidation process of pyrite, it is suggested that the phase characteristics of pyrite bio-leaching can be divided into three phases, namely, phase I (inorganic oxidation of pyrite), phase II (bio-oxidation of Fe²⁺) and phase III (equilibrium bio-oxidation of pyrite).

Key words: Pyrite, Acidithiobacillus ferrooxidans, Bio-oxidation, Phase