Effect of pyrite on bioleaching of arsenopyrite

In order to clarify the function of pyrite in arsenopyrite bioleaching, pure pyrite and arsenopyrite were used to prepare a pulp system for studying the effect of the pyrite-to-arsenopyrite mass ratio and particles size of pyrite on the leaching rate and oxidation state of arsenic. The results show that the leaching rate of arsenic increases with increasing the mass fraction of pyrite and decreases with increasing the particle size of pyrite. When the mass ratio of pyrite to arsenopyrite is 10:2 and the particles size of pyrite is less than 74 μm, the highest leaching rate of arsenic is 97.7%, which is about 43.18 % higher than that of the arsenopyrite bioleaching without pyrite. The pyrite can accelerate the transform of As(Ⅲ) to As(Ⅴ), which reduces the toxicity of pulp and makes the bioleaching system have higher bacterial density, lower pH, higher oxidation-reduction potential, and generates galvanic effect with arsenopyrite. Therefore, the bioleaching efficiency of arsenopyrite can be promoted by adding pyrite.