Bioleaching of a Copper Sulphide Concentrate by two different Strains of Acidophilic Bacteria

Two strains of acidophilic Thiobacillus generae, one isolated from the water of a copper mine and another, a pure culture have been used for the processing of a sulphidic copper concentrate with 14.13% Cu, 10.04% Ni, 0.33% Co, 0.71% Mo, 2.28% Fe, 36.4% S and 1.72% 5102 generated at UCIL Jaduguda, India. The concentrate has chalcopyrite and pentlandite as the major phases along with pyrite, pyrrhotite, violarite, millerite and moly-bdenite as the minor phases. The unadapted isolated culture of Acidithiobacillus ferrooxidans dissolved 41%
Ni and 35% Co at 308K and pH 2.0 in 60 days from the mixed
size (<200 gm) particles. Pyrite (10 wt%) was found to be an effective additive resulting in bioleaching of 81% Ni and 45% Co under above condition; biorecovery being high (90% Ni and 61% Co) from the finest size particles (<50 /an). A. ferrooxidans strains of another source (OU, Hyderabad) adapted over copper concentrate serially for four times at 2.3 pH and used for leaching, improved the kinetics showing biorecovery of 83% Ni and 88% Co in
30 days only with the mixed size particles.