Electrochemical and leaching studies to better understand the role of ethylene glycol in the oxidative acid dissolution of chalcopyrite

•Ethylene glycol (EG) in H2SO4 leach solutions does not increase CuFeS2 oxidation.•EG adsorption on the CuFeS2 surface deters H2O2 dismutation, diminishing consumption.•Presence of surfactants (EG, Tween 80 & 20) does not alter the dissolution mechanism.•Improvements in CuFeS2 dissolution may be due to decreases in interfacial tension. It has been demonstrated that the combined use of organic compounds and acidic peroxide solutions greatly improves the dissolution kinetics of chalcopyrite. Among the additives employed, ethylene glycol (EG) is one of the most attractive for operating at moderate temperatures (20–50 °C). However, the role of EG in the leaching process is still not clearly understood, which limits optimization and industrial scale-up. For this reason, in this investigation, an electrochemical study was undertaken, using both a solid chalcopyrite (SE-Cp) electrode coupled to a rotating disk, as well as a chalcopyrite concentrate carbon paste electrode (CPE-CCp). Leaching experiments were also performed with EG and several other organic compounds, comparing the copper dissolved in each case. The results, in the mixed potential range of 0.55–0.75 V, showed that the presence of EG did not increase chalcopyrite oxidation. However, EG adsorption on the surface of the sulfide is sufficient to hinder hydrogen peroxide dismutation, the main cause of H2O2 decomposition in EG-free acidic solutions; at the same time, decreasing the interfacial tension favors chalcopyrite contact with the solution. Finally, the formation of similar products on the chalcopyrite surface, suggest that the organics additives do not alter the dissolution mechanism.