An electrochemical study of galena concentrate in perchlorate medium at pH 2.0:: the influence of chloride ions

An electrochemical study of galena flotation concentrates in solutions of perchlorate and chloride ions at pH 2 has been carried out, through the use of carbon paste electrodes and cyclic voltammetry. The analysis of the voltammetric results indicates that in perchlorate solutions the galena is oxidized forming several products dependent on the applied potential. When the potential is below to 0.54 V/saturated calomel electrode (SCE), Pb(II) and elementary sulfur are formed. Galena oxidation to higher oxidation state of sulfur (e.g, thiosulfate and sulfate) requires a higher overpotential (E > 0.8 V vs. SCE), in the presence of perchloric acid, while in chloride medium a considerable lower overpotential is needed. From this reaction, the Pb(II) reacts with the chloride ions in order to form a lead-chloride complex that could precipitate depending on the concentration of chloride in solution and also could remain adsorbed on the galena particle surface. In the chloride media, the galena is reduced into metallic lead and hydrogen sulfide. (C) 2000 Elsevier Science Ltd. All rights reserved.