THE BIOLEACHING OF DIFFERENT SULFIDE CONCENTRATES USING THERMOPHILIC BACTERIA

The bioleaching of different mineral sulfide concentrates with thermop hilic bacteria (genus Sulfolobus) was studied. Since the use of this t ype of bacteria in leaching systems involves stirring and the control of temperature, the influence of the type of stirring and the pulp den sity on dissolution rates was studied in order to ascertain the optimu m conditions for metal recovery. At low pulp densities, the dissolutio n kinetic was favored by pneumatic stirring, but for higher pulp densi ties, orbital stirring produced the best results. A comparative study of three differential concentrates, one mixed concentrate, and one glo bal concentrate was made. Copper and iron extraction is directly influ enced by bacterial activity, while zinc dissolution is basically due t o an indirect mechanism that is activated in the presence of copper io ns. Galvanic interactions between the different sulfides favors the se lective bioleaching of some phases (sphalerite and chalcopyrite) and l eads to high metal recovery rates. However, the formation of galvanic couples depends on the type of concentrate.