ELECTROCHEMICAL ASPECTS OF ZINC-SULFIDE LEACHING BY THIOBACILLUS-FERROOXIDANS

It is proposed that the bioleachability of a zinc sulfide flotation concentrate is influenced by the electrochemical behavior of ZnS. The overall reaction of bio-oxidation: ZnS+ 2O2 bacteria --> ZnSO4 was found to involve a number of intermediate electrochemical reactions, as indicated by the cyclic voltammetric measurements using carbon paste-ZnS working electrodes. The solubilization of ZnS during leaching is solid-state diffusion controlled, as indicated by chronopotentiometric and chronoamperometric measurements. The activation energy of the solid-state-diffusion process was determined by Sand's method to be 21.3 kJ.