Role of Pyrite in Selective Bioleaching of Metals from a Complex Sulphide Concentrate

Abstract

The copper concentrate is a kind of complex sulphide material containing minerals such as chalcopyrite, pyrite, pentlandite, pyrrhotite, etc. with valuable metals like 14% Cu, 10% Ni, 0.33% Co and 0.71% Mo. Bioleaching of copper concentrate was carried out in presence of Acidi-thiobacillus ferrooxidans and Acidithiobacillus thiooxi-dans isolated from the copper mine water to optimise the parameters. In order to understand the role of pyrite, selective bioleaching of 90% Ni and 61% Co was observed in presence of 10% pyrite in 60 days at 308K and 2pH with the particles of size < 50 m with unadapted culture. While recovery of 81% Ni, 45% Co and 5% Cu were achieved with the mixed size particles of ≤200 m in 60 days time under the above conditions. The selective bacterial dissolution of nickel and cobalt as compared to copper is governed by galvanic interaction between chalcopyrite and pentlandite-/pyrrhotite which is accelerated by the addition of pyrite in the concentrate.