Copper leaching from primary sulfides: Options for biological and chemical extraction of copper

The primary sulfide minerals of copper have been difficult to leach for the purpose of direct copper extraction. In particular, chalcopyrite has been observed to undergo a type of "passivation" under a variety of oxidative leaching conditions. Over the last 10-15 years, a variety of biological and chemical leaching processes have emerged for overcoming the passivation of chalcopyrite. A number of these processes are now entering commercial production or are approaching this status. The BIOCOP(TM) process of BHP Billiton has now been commercialized at the Alliance Copper plant in Chile. The Total Pressure Oxidation technology has been implemented by Phelps Dodge at Bagdad, Arizona. The Mt. Gordon copper process and the Sepon copper process both use autoclave processes in the overall metallurgical circuit. In the Mt. Gordon circuit, the autoclave was used to leach copper while at Sepon the autoclave is used to produce acid and ferric sulfate to meet the requirements of an atmospheric leach. CESL and CVRD have completed a feasibility study to apply the CESL copper process in Brazil. PLATSOL(TM) technology for copper, nickel, cobalt and precious metal recovery is now under final feasibility study for application by PolyMet Mining at the NorthMet deposit in Minnesota, USA. The number of available options for copper recovery from primary sulfides is multiplying. In addition to the above options utilizing stirred reactor leaching, a number of heap leach options for primary sulfides are also emerging. For this paper, the various processes for copper extraction from concentrate were reviewed, including the underlying mechanisms of leaching, followed by a comparison of the advantages and disadvantages of selected process options. (C) 2006 Elsevier B.V. All rights reserved.