Oxidative dissolution of chalcopyrite by Thiobacillus ferrooxidans

The oxidative dissolution of research-grade chalcopyrite was characterized in respirometric and growth experiments with Thiobacillus ferrooxidans. In respirometric experiments with chalcopyrite, the pH of mineral salts medium increased to values that inhibited the oxygen uptake activity of T. ferroo xidans. In glycine-H2SO4 buffered medium the pH remained stable and oxygen uptake was not inhibited. In cultures growing with chalcopyrite as the sole source of energy, pH changes were only minor during the incubation. The re dox potential values increased to about 600 mV during the bacterial oxidati on of chalcopyrite in the presence and absence of additional Fe2+, while th ey remained at about 350 mV in abiotic control flasks. Iron in chalcopyrite was solubilized and oxidized to Fe3+ by T. ferrooxidans. In the abiotic co ntrols, by comparison, less iron was solubilized and it remained as Fe2+. J arosite was a major solid-phase product in T, ferrooxidans cultures. The so lubilization of copper from chalcopyrite in inoculated flasks was enhanced in the presence of additional Fe2+. Accumulation of S-0, reflecting partial oxidation of the S-entity of chalcopyrite, was apparent from the x-ray dif fraction analysis of solid residues from the inoculated flasks as well the abiotic controls.