Abstract
The addition of iodine is known to significantly accelerate chalcopyrite leaching in ferric sulfate media. Previous studies on heap leaching of chalcopyrite-bearing ores have shown significant increases in copper extraction from chalcopyrite when small amounts of iodine are present in the leach solution. This study aims to develop an atmospheric stirred tank leaching process that incorporates iodine to enhance chalcopyrite leaching kinetics. Thermodynamic calculations were first performed to determine the stability region of iodine species as a function of the ferric-to-ferrous ratio in the system studied. Due to possible evaporation loss and material corrosion, kinetic studies were conducted in a specially designed, fully sealed stirred reactor. Two chalcopyrite samples with different copper grades and mineralogical characteristics were used to evaluate the effects of leaching parameters on copper extraction. The results show that copper extraction increased by approximately 60% within 48 h in the presence of iodine compared with in the absence of iodine. Moreover, the rate of copper extraction increased at a higher temperature, total iodide concentration, and initial solution potential up to a certain extent. It was also found that the high rate of copper dissolution could be maintained by replenishing the system with fresh oxidant or by adding chloride to the sulfate system. A kinetic model was then developed to correlate the copper dissolution rate with these parameters.