Enhanced oxidative leaching of copper-iron sulfides using photo-assisted electrochemical advanced oxidation processes

In this work, the effectiveness of electro-Fenton and photoelectro-Fenton processes for enhancing the oxidative leaching of copper-iron sulfide minerals such as chalcopyrite (CuFeS2) and bornite (Cu5FeS4) in aqueous suspension was investigated. Electro-Fenton experiments were conducted in an electrochemical reactor equipped with a boron-doped diamond anode and a carbon-polytetrafluoroethylene gas-diffusion electrode as a cathode. The results show that, after 3 h, CuFeS₂ and Cu₅FeS₄ reached Cu and Fe leaching rates of 20% and 26%, respectively. These findings demonstrate enhanced performance under mild conditions compared to conventional leaching processes. Additionally, UV–Vis light irradiation was evaluated to assess the contribution of light-induced mechanisms, including photocorrosion and photo-Fenton reactions, establishing that the enhancement in leaching yield was relatively less significant (≈5%). The involvement of radical species such as hydroxyl and sulfate radicals was evaluated using in-situ electron paramagnetic resonance spectroscopy. Furthermore, the role of physisorbed hydroxyl radicals was evaluated by using an active metal mixed oxide anode in place of boron-doped diamond anode. This study demonstrates that in-situ electro-generated H2O2, together with dissolved iron (Fe2+ and Fe3+) and copper ions (Cu2+), can trigger Fenton, and photo-Fenton mechanisms, thereby promoting the oxidative dissolution of sulfide minerals. These findings provide a proof of concept for a more sustainable and alternative approach to mineral resource leaching.