THE CATALYTIC EFFECT OF SOME CATIONS ON THE BIOLOGICAL LEACHING OF A SPANISH COMPLEX SULFIDE

The bacterial leaching process of a bulk concentrate of a complex sulphide, in the presence of various ions of differing concentrations in the leaching solution (Ag (I), Hg (II), Co (II), Bi (III), As (V) and Ru (III)), were studied in order to compare the catalytic effect of these cations on the dissolution rate of the non-ferrous metals contained in the starting mineral, mainly Cu and Zn. Trace metal ions modify the electrochemical behavior of solids, however the literature provides very little information concerned with this topic. The sequence of catalytic effectiveness of the different ions on the dissolution of copper was: Ag (I) much greater than Hg (II) > Co (II) > Bi (III) > As (V) > Ru (III) almost-equal-to reference. For the dissolution of zinc the order was: Bi (III) greater-than-or-equal-to Co (II) almost-equal-to Ru (III) greater-than-or-equal-to Hg (11) > As (V) almost-equal-to Ag(I) almost-equal-to reference. Previously, and only with the cation Ag (I), the influence of pulp density was studied in order to select the optimum value of this variable, at which all of the subsequent experiments were carried out. Similarly, the kinetic constants were obtained for those tests which gave the highest recovery of metal with each catalyst.