Abstract

The development and implementation of the copper Solvent Extraction (SX) process enabled an expansion in the options for treating copper ores to include processes such as the leaching of oxides in heaps and dumps. This expansion was then further extended into secondary sulfides of copper thanks to the development of bioleaching. Combined with electrowinning (EW), these two methods allowed a significant increase in copper cathode production from approximately 50,000 tonnes a year in the 1970s to almost 4M tonnes by 2015. The two process innovations behind leaching (the development of ketoxime resins by General Mills) and bioleaching (work on ferro-oxidant archaea organisms) changed the way copper deposits were evaluated, opening the opportunity to produce metal economically from oxide minerals and low-grade secondary sulfides.

Now copper cathode production is expected to decrease due to the depletion of copper oxides and secondary sulfide reserves. In the case of Chile for example, production of SX-EW copper peaked at over 2M tonnes in 2009 while the projected production for 2031 is only 0.5M tonnes. This would leave significant idle production capacity, a phenomenon that is also expected to occur in several of the main copper cathode producing countries in the coming years.  

This idle SX-EW capacity could be used for the hydrometallurgical processing of low-grade chalcopyrite ores, a mineral that contains approximately 70% of the copper available in the Earth's crust. However, processing of chalcopyrite is currently characterized by slow and incomplete leaching. There is consensus that the oxidation reaction is inhibited by the formation of a passivating layer on the surface of chalcopyrite, but there is no agreement on the nature and composition of this layer.

In recent years several hydrometallurgical processes have been developed, on a laboratory and pilot scale, to extract copper from chalcopyrite in heaps. These include, optimized bioleaching, leaching with additives, chloride-assisted leaching and leaching with other reagents. However, none of these processes has been applied successfully at commercial scale except for the Jetti Process. 

Jetti Resources has developed a catalytic technology that interrupts and prevents the formation of the passivating layer, which allows heap leaching to be applied to low-grade primary sulfide minerals economically. This technology was first applied at the Pinto Valley Mine in May 2019, where copper production was increased by more than 100% per irrigated area.

The copper industry benefitted from the developments of SX and bioleach which enabled cathode production to grow to represent up to 25% of world copper production at its peak. Depletion of the resources amenable to traditional leach methods is now resulting in a decline of cathode production offering the opportunity of idle capacity available for technologies such as Jetti’s that have proven to successfully leach copper from primary sulfides. 

Innovation in extractive processes has been key to providing the metals that humanity has needed to support civilization. The current challenge of supplying the copper that an electrified society requires can only be met by adopting new technologies that allow access to resources previously considered as stranded or waste.