Cooperative action of attached and planktonic cells during bioleaching of chalcopyrite with Sulfolobus metallicus at 70 °C

The catalytic influence of Sulfolobus metallicus in the bioleaching of chalcopyrite at 70 °C and pH 1.5 was studied in shake flask experiments. Leaching was conducted in an iron-free basal medium with a - 80 # + 120 # chalcopyrite sample, and was characterized from monitoring in solution the pH, Eh, copper and iron concentration, and cell population. In order to evaluate separately the influence of planktonic and attached cells on the catalytic process, in some experiments the microorganisms were prevented from reaching the chalcopyrite surface by keeping them in a chamber separated by a 0.1 Millipore membrane. In a complementary experimental series, the concentration of different sulfur species dissolved in the solution was determined with HPLC at different conditions, under nitrogen or air, abiotic or inoculated with S. metallicus. Maximum copper dissolution was reached when at least one fraction of the inoculated microorganisms were able to approach chalcopyrite surface. In this ca