PYRITE’S CRUCIAL ROLE IN COBRE LAS CRUCES ATMOSPHERIC LEACHING PROCESS

Since 2009, Cobre las Cruces (CLC) has operated a sustainable mining business near Seville, Spain, using advanced hydrometallurgical technologies to process secondary copper sulphide ores through atmospheric leaching in ferric sulphate media and utilizing oxygen sparging in a cascade of ten reactors. Unlike conventional copper smelters, the CLC hydrometallurgical process eliminates SO2 emissions and slags. The copper ore is directly ground and sent to atmospheric leaching reactors, enhancing copper extraction to 93-95%, ultimately producing 72,000 t/y of high-purity copper cathodes (99.999 wt.% Cu, Grade A). Reserves at the CLC deposit are approximately 16 million tonnes, predominantly containing chalcocite mineralization along with other copper-bearing species such as digenite and covellite, with pyrite making up over 70 wt.% of the ore. In the process, chalcocite reacts with ferric sulphate at about 90 ºC, releasing copper into the solution while reducing ferric ions to ferrous ions. Pyrite is crucial for achieving high copper leaching rates through its oxidation, which co-leaches iron and produces sulphuric acid. The CLC technology fosters pyrite oxidation, enhancing leaching kinetics and overall efficiency.