Abstract
— In this work, the comparative effects of roasting and redox potential control on the dissolution of chalcopyrite (CuFeS₂) in chloride media using hydrochloric acid and magnetite as a redox mediator was investigated. Chalcopyrite samples were roasted at 400 °C, 600 °C, and 900 °C for 1.5 hours, followed by 8-hour leaching experiments conducted at 30 °C, 40 °C, 50 °C, and 60 °C. XRF analysis revealed that the unroasted sample contained high copper (26.26 %), iron (19.46 %), and sulfur (7.94 %), confirming its sulfide-rich composition. Roasting at 600 °C reduced Sulphur to 3.42 % and produced more reactive CuO and Fe₂O₃ phases, whereas at 900 °C, extensive oxidation formed refractory CuFe₂O₄, limiting reactivity. XRD confirmed these phase transformations, showing progressive oxidation with increasing temperature. Leaching tests demonstrated that roasting temperature and redox potential strongly influenced copper recovery. The highest copper recovery was obtained for the 600 °C roasted sample with magnetite assistance, reaching approximately 80–85 % Cu recovery at 60 °C, compared to 50–60 % for the 400 °C sample and 35–45 % for the 900 °C sample. Without magnetite, recoveries decreased significantly, with the 600 °C roast yielding only 60–70 % Cu and the 900 °C roast achieving 25–35 % Cu. SEM-EDS confirmed increased oxidation and porosity at 600 °C, while 900 °C produced dense oxide layers that hindered dissolution. The results indicate that roasting at 600 °C combined with magnetite redox control provides the optimal balance between structural oxidation and redox stability, maximizing copper extraction efficiency in chloride-based leaching systems.