Kinetics of copper dissolution in the purification of molybdenite concentrates by sulfidation and leaching

Molybdenum is found in low quantities in copper porphyries as the mineral molybdenite. In the processing of these ores, a bulk copper-molybdenum concentrate is produced, from which molybdenite is separated by differential flotation. However, complete separation of molybdenum from copper by flotation is difficult, and molybdenum concentrates produced by this route require a further step of chemical purification to reduce their copper content. This paper is concerned with a novel process of chemical purification of molybdenite concentrate containing 3.4% Cu and 3.04% Fe where chalcopyrite is the main impurity. The process involves a sulfidation of the molybdenite concentrate with S2(g) at 380 °C followed by a leaching stage with H2SO4–NaCl–O2. The leaching of the sulfidized molybdenite concentrate for 90 min at 100 °C dissolved 96% of the copper which yielded a final concentrate with less than 0.2% Cu. Molybdenite dissolution was negligible in this leaching media, and less than 20% Fe was dissolved. The kinetics of copper dissolution from the sulfidized concentrate was analyzed using the shrinking core model for chemical reaction control. Activation energy of 52.5 kJ/mol was calculated for the temperature range of 70 °C–100 °C.