An Electrochemical and Leach Study of the Oxidative Dissolution of Chalcopyrite in Ammoniacal Solutions

Chalcopyrite is the most abundant copper sulphide and is notable for its stability, which complicates its hydrometallurgical treatment, particularly in atmospheric leaching. As ore grades decline and concentration cost rises, there is a pressing need to reassess hydrometallurgical methods, especially heap leaching, due to their economic and environmental advantages. Key processing strategies for chalcopyrite include ferric sulphate, chloride, and ammoniacal systems. While the ferric sulphate approach requires thermophilic microorganisms for atmospheric efficiency and the chloride system has gained attention in heap leaching, the ammonia system remains largely underutilized, with existing studies largely dating back over four decades. This research demonstrates that ammonia systems, in conjunction with an oxidant, effectively leach copper from chalcopyrite. The ammoniacal leaching process is critically dependent on surface mass transfer, often examined in high-pressure scenarios utilizing oxygen as the oxidizing agent. This study encompasses the design of leach reactors employing agitation techniques, which facilitate the removal of an iron-based passivating layer on the mineral surface, thereby enhancing leaching efficacy under controlled conditions.