Bioleaching of Sulfide Concentrates with Different Copper and Zinc Contents and Evaluation of Bioleach Residue Grade

Bioleaching of sulfide concentrates with different copper and zinc contents using two cultures of acidophilic chemolithotrophic microorganisms, which were grown at 30 and 35 degrees C, was studied. The average leaching rate of copper was shown to be directly dependent on the copper content in the concentrate. The leaching rate of zinc was found to depend not only on the zinc content but also on the copper content. At the same time, the specific leaching rate of copper varied insignificantly (28-45 mg/(g day)), while the change in the specific leaching rate of zinc was much more pronounced (107-319 mg/(g day)) and depended on the metal contents in the concentrates. Under all conditions of bioleaching, the specific rate of zinc extraction into the aqueous phase increased significantly with an increase in the copper content in the concentrates, which indicated galvanic interactions between sulfide minerals. The possibility of the obtainment of the copper concentrates containing negligible amounts of zinc after bioleaching of the concentrates, in which the content of copper exceeded that of zinc and was not less than 10%, was shown. Bioleaching of the concentrates containing more zinc than copper is impractical.