Electrochemical study of the catalytic influence of Sulfolobus metallicus in the bioleaching of chalcopyrite at 70 °C

Abstract

The catalytic influence of Sulfolobus metallicus in bioleaching of chalcopyrite at 70 °C and pH 1.7 was characterized from studies of anodic dissolution of a chalcopyrite concentrate at constant potential. Experiments were conducted in iron-free nutrient medium which minimized the influence of jarosites formation on the process. The use of a novel electrochemical technique enabled the simultaneous determination of copper dissolution rate and the number of electrons involved in the dissolution reaction. This experimental approach permitted to monitor the degree of the oxidation of reduced sulfur compounds and assess its influence on the copper dissolution kinetics. Experimental results showed that in bioleaching of chalcopyrite with S. metallicus there is an efficient process of oxidation of residual sulfur compounds, i.e. sulfur and polysulfides, formed during the chemical dissolution of the sulfide. This oxidative process contributes to a dramatic increase in copper dissolution rate with respect to that obtained in chalcopyrite dissolution under simple indirect bacterial action. Oxidation of reduced sulfur compounds in the presence of S. metallicus involves the participation of a mechanism of chemical catalysis triggered by the presence of dissolved oxygen in solution.