Changes of Electrode Potential in the Non-Oxidative Leaching

This study investigates the changes in electrode potential during the non-oxidative leaching of Lubin shale middlings using sulfuric acid, with a focus on determining the leaching kinetics and the electrochemical parameters at the mineral/solution interface. Simultaneous measurements of pH and redox potential were conducted using a platinum electrode and copper sulphide electrodes. The results indicate a significant decrease in the redox potential of the solution from +350 mV to +50 mV (Ag, AgCl) as pH increased during carbonate decomposition. This low redox potential serves as a barrier against the oxidation of copper sulphide minerals, ultimately preventing the release of Cu and Fe into the solution. The non-oxidative leaching process was found to be rapid and selective, leading to the effective decomposition of calcium and magnesium carbonates while saturating the leaching slurry with carbon dioxide. Additionally, it was observed that increasing the degree of carbonate decomposition from 50% to 100% markedly improved the liberation of metal-bearing minerals, which is beneficial for subsequent upgrading or leaching processes.