Development of an efficient green process for extraction of copper from waste printed circuit boards using methanesulfonic acid and hydrogen peroxide

This study investigates the utilisation of an environmentally benign leaching reagent system comprising methanesulfonic acid (MSA) and hydrogen peroxide (H2O2) for efficient copper extraction from waste printed circuit boards (WPCBs) of end-of-life computers. The effects of MSA concentration, H2O2 concentration, and temperature were evaluated using a central composite design. The results demonstrate that peroxide-assisted MSA leaching can achieve a high copper leaching efficiency (93.5%). An increase in both MSA (0.20-1.00 M) and H2O2 (up to 2.00 M H2O2) concentrations positively influenced copper leaching. However, higher temperatures (>40 ℃) were found to negatively affect the process. Although elevated temperatures typically enhance reaction kinetics, excessive decomposition of H2O2 at higher temperatures limited the optimal leaching temperature to 40 °C. The method of H2O2 addition was also a critical factor in leaching efficiency. Direct addition (at the start of the leach test) of H2O2 resulted in a copper recovery of only 53.9%, whereas leaching under the same conditions (0.60 M MSA, 0.41 M H₂O₂, 5% (w/v) solids ratio) achieved 92% copper recovery after 3.5 hours. Additionally, an increase in solid content was found to reduce leaching efficiency. Iron and silver were observed to co-dissolve up to 85.2% and 76.7%, respectively, alongside copper during the leaching process. The synergistic effect of MSA and sulphuric acid (H2SO4) in the presence of H2O2 was also explored. This study demonstrates that MSA, under suitable conditions, can serve as an effective and environmentally friendly alternative to traditional inorganic acids such as H2SO4 for the leaching of WPCBs.