H Naderi - Department of Mining and Metallurgical Engineering, Yazd University, Yazd, Iran
M Abdollahy - Mining Engineering Department, Faculty of Engineering, Tarbiat Modares University, Tehran, Iran
N Mostoufi - School of Chemical Engineering, College of Engineering, University of Tehran, Tehran, Iran

Kinetics of the chemical leaching of chalcocite from a low-grade copper ore in a ferric sulfate medium wasinvestigated using the constrained least square optimization technique. The experiments were carried out fordifferent particle sizes in both the reactor and column at constant Eh, pH, and temperature. The leaching rateincreased with increase in the temperature. About 50% of the Cu recovery was obtained after 2 hours ofreactor leaching at 75 o C using the -0.5 mm size fraction. Also about 50% of the Cu recovery was obtainedafter 60 days of column leaching for the +4-8 mm size fraction. For the fine-particle leaching, the firstleaching step was fast, and the rate controlling step was diffusion through the liquid film. The resultsobtained show that as the leaching proceeds, the chemical reaction control appears. Finally, accumulation ofthe elemental sulfur layer in the solid product together with the jarosite precipitate causes change in thecontrolling mechanism to solid diffusion. For the coarse-particle leaching, diffusion through the solidproduct appeared from the initial days of leaching.

Leaching, Chalcocite, Kinetic Study, Shrinking Core Model (SCM)