Estudo eletroquímico a partir de traços de íons metálicos encontrados em soluções recicladas de baterias chumbo-ácido.

Abstract

Despite the rapid improvement in its performance in the last decades, lead-acid battery still presents some problems, being one of the main the decomposition of the water molecule causing the evolution of hydrogen in the negative plate during the load, increasing the risk of explosion and consumption of electrolyte water. Contaminant metal ions can act as electrocatalysts facilitating the evolution of hydrogen on the surface of the lead electrode. The influence of Cu2+, Mn2+ and Fe3+ metal ions present in recycled electrolytic solutions, and the synergistic effect of these ions, on the potential of hydrogen evolution on the negative electrode of lead-acid batteries. The results provided with the aid of potentiodynamic polarization and chronopotentiometry techniques showed that all the metal ions studied displaced the evolution potential of this gas to more anodic values, facilitating the evolution of the hydrogen on the surface of the negative electrode, being the synergic effect of ions greater emphasis. The technique of cyclic voltammetry made it possible to understand the performance of the metallic ions in the studied system, demonstrating the ease of adsorption of Cu2+ ions on the surface of the electrode, while the electrochemical impedance spectroscopy characterized the double electric layer of the system studied by means of an electric circuit equivalent, evidencing that there is strong accumulation of the ionic species in the adsorbed layer of lead sulphate. All the results showed a strong influence of the metal ions in the evolution of the hydrogen gas on the negative electrode, indicating that these species must have their concentrations minimized to enable processes of reuse of the acid solution of lead-acid batteries.