Leaching of chalcopyrite in cupric chloride solution

Outokumpu HydroCopper (TM) technology was developed by Outokumpu Research. It is a novel copper production method based on the efficient leaching properties of cupric chloride solutions. The leaching is operated at atmospheric pressure, near the boiling point of water in a stirred reactor and the pH is kept between 1.5 and 2.5. In the present work, an electrochemical study of the dissolution behaviour of chalcopyrite, the most common copper mineral, was made in a concentrated sodium chloride solution (250 g/L) with cupric ion concentrations varied in the range 0.09-26.6 g/L. The effects of pH (1-3) and temperature (70-90 degrees C) were also measured. The rotating disk electrode technique was used to determine the rate-controlling step in the leaching process. The increase in the dissolution rate was observed to be proportional to the increase in the temperature and to the cupric ion concentration with [Cu2+]> 9 g/L. With [Cu2+]< g g/L, the cupric ion concentration did not affect the leaching rate. In order to investigate the reaction products of the chalcopyrite dissolution, the electrodes were analysed by scanning electron microscopy. The results suggested that iron oxides, hydroxides and chlorides gathered on the chalcopyrite surface at higher pHs. At lower pHs, chalcopyrite passivated and a sulfur-rich layer was detected on the surface. (c) 2004 Published by Elsevier B.V.