Iodine-assisted chalcopyrite leaching in ferric sulfate media: Kinetic study under fully controlled redox potential and pH

Abstract

The addition of iodide has been found to significantly accelerate chalcopyrite leaching in ferric sulfate media at ambient conditions. Solution potential is the principal factor determining the leaching performance through controlling the iodine speciation. In order to develop a kinetic equation that incorporates the iodine speciation, a series of leaching tests were carried out in specially-designed sealed reactors that allows the solution potential together with other leaching parameters to be fully controlled. The experimental results showed that the rate of copper dissolution was increased by increasing the solution potential in the range of 669 to 769 mV vs. SHE), increasing the total iodide concentration in the range of 50 to 200 mg/L, and increasing the temperature between 25 and 40 °C. The formation of elemental sulfur and jarosite did not hinder the leaching reaction. A kinetic model was developed that relates the rate of copper extraction to the solution potential with a reaction order of 0.32, the diiodine concentration with a reaction order of 1.17, and temperature with an activation energy of 43.1 kJ/mol. The kinetic analysis supported that the leaching process was controlled by surface chemical reaction.