2025 Theses Doctoral

Exploration of Room Temperature Leaching Methods of Chalcopyrite-based Copper Concentrates

Kim, Charles

This doctoral thesis focuses on the development of low-energy, high-yield hydrometallurgical processes of extracting copper to meet the increasing demands due to global transition towards carbon-free energy. This thesis investigates two room-temperature leaching methods – vanadium reductive leaching and cerium oxidative leaching – as alternatives to traditional high-temperature oxidative leaching methods of chalcopyrite-based copper concentrates.

For the vanadium reductive leaching method, this study focused on the improvement of leaching kinetics across different mineral compositions and the development of a continuous reactor to evaluate the processing rate. Results reveal rapid reaction kinetics and high copper recovery yields across a range of mineral compositions, with improved performance with the addition of FeSO₄ in the leach solution. The processing rate was competitive against the incumbent leaching processes, making vanadium leaching a promising candidate for industrial scale-up, despite requiring H₂S gas treatment.

For the cerium oxidative leaching method, this study focused on the improvement of leaching kinetics and the analysis of the leaching reaction and the solid products to overcome the passivation of the copper concentrates. While more environmentally friendly compared to vanadium leaching process, the kinetics were less favorable, and the process faced limitations due to the high consumption and low solubility of Ce⁴⁺.

Second, process flow diagrams, reactor sizing, and energy requirement calculations were developed for both methods. Vanadium leaching required significantly smaller reactors and lower power outputs, confirming its scalability and economic feasibility.

Third, the electrochemical and chemical air oxidation regeneration methods of Ce³⁺ were explored. The results indicate that chemical air oxidation method faces challenges due to the consumption of unrecoverable acids and bases, and the overall intense conditions required for the dissolution of Ce(OH)₄ to Ce⁴⁺. Although limited by the solubility of Ce³⁺ in sulfate media, the electrochemical regeneration method was found to be more feasible.

In conclusion, this thesis presents a comprehensive comparison of two room-temperature leaching strategies for copper recovery. Vanadium-based reductive leaching emerges as the more practical and scalable option for commercial deployment. Future research should prioritize leachant regeneration, environmental risk mitigation, and pilot-scale validation to accelerate the adoption of these low-temperature hydrometallurgical technologies.