Studies on leaching of massive rich copper ore in acidic ferric sulfate solutions

Representative samples of Küre (Turkey) massive rich copper ore were leached in acidic ferric sulfate solutions in order to recover copper and its associated metals (Zn, Co, Ni) present in the ore. The effects of leaching time, ferric ion concentration, acid concentration, solid/liquid ratio, temperature and silver sulfaste addition on metal leaching recoveries were investigated. Optimum leaching conditions and leaching kinetics were determined. Formation of elemental sulfur, which creates a diffusion barrier, was elucidated. In order to remove the retarding effect of elemental sulfur, silver ions were introduced to the leach medium and significant improvements were observed, especially in copper dissolution. Activation energies were found to be 36.7 kJ/mole for Cu and 43.3 kJ/mole for Zn dissolutions. The rate-controlling step was found as the diffusion of ferric ions into the solution filling the pores of sulfur layer formed on the surface of partially leached ore particles.