The dissolution of copper from chalcopyrite was investigated in the presence of hydrogen peroxide and ethylene glycol. Hydrogen peroxide was used as oxidant in the leaching process. Addition of a small amount of ethylene glycol significantly improved the copper dissolution. The copper leaching mechanism was established by examining the influence of various parameters on the reaction rate in the presence of ethylene glycol. The effect of temperature on the reaction kinetics suggests that the leaching reaction follows the surface reaction-controlled model. The linear relationship between the log of reaction rate constant and log of particle radius supports the proposed reaction model. The reaction order was calculated with respect to hydrogen peroxide which indicates that hydrogen peroxide has greater influence on the leaching kinetics. Stirring speed and sulfuric acid concentration are not important variables. Most of the sulfide ions were transformed to elemental sulfur during the reaction. The elemental sulfur was present on the surface of chalcopyrite residue as discrete crystalline particles instead of a coating of continuous film which causes the passivation of chalcopyrite surface. Ethylene glycol was found to stabilize the hydrogen peroxide at elevated temperature which could be another reason for enhanced recovery. (C) 2007 Elsevier Ltd. All rights reserved.