Processing of chalcopyrite ore by heap leaching and flotation

This study explored the processing of chalcopyrite ore through heap leaching followed by flotation. Crushed and agglomerated chalcopyrite ore was subjected to bacterially-assisted leaching at ambient temperature in columns that ranged in height from 1 m to 5 m. > 50% extraction was obtained after 16 months. Chalcopyrite leaching was affected only by time, not irrigation rate, acid delivery rate, or column height. This indicated that chalcopyrite heap leaching was reaction-limited rather than transport-limited, and therefore relatively impervious to scale. The findings suggest that chalcopyrite could be leached in substantially taller heaps, releasing proportionally greater quantities of copper, without sacrificing recovery. Leaching of the chalcopyrite ore had little effect on its floatability, as indicated by rougher flotation testing. The maximum flotation recoveries, RMAX, were 90% and 88% for the ore and leached residues, respectively. The combined leach/float recoveries were greater than the individual copper recoveries from leaching and flotation alone. This was simply due to the initial leaching step recovering some of the copper that would have been inevitably lost to flotation tailings. Such a leach/float approach may actually benefit from the low reactivity of chalcopyrite, which ensures that leaching would never be so extensive as to affect the later floatability of the mineral.