EFFECT OF SOME METAL IONS FOUND IN RECYCLED BATTERY SOLUTIONS ON THE HYDROGEN EVOLUTION REACTION POTENTIAL

Although lead-acid batteries contain about 11 to 30% by weight of electrolyte, the reuse of sulfuric acid solutions raises many questions for the electric accumulator industry concerning the advantages of the process, mainly due to the influence of these solutions on performance of batteries. At the end of the battery's life, the electrolyte has critical amounts of contaminating metal ions that can decrease the hydrogen production overvoltage, increasing water loss and decreasing its electrical performance. In the present work, the influence of Cu2+, Mn2+ and Fe3+ ions present in reused electrolytic solutions, and their synergy, on the hydrogen evolution potential in the lead-acid battery negative electrode was investigated. The mode of action of these contaminants was also investigated by cyclic voltammetry and electrochemical impedance. The results showed that all the metal ions displace the potential of evolution of this gas to less cathodic values, indicating that these species must have their concentrations minimised to allow acid solution reuse in lead-acid batteries without significant loss of performance.