Acceleration of Copper Leaching of Secondary Copper Sulfide Ores

The purpose of this study is to clarify the differences in leaching behavior among various kinds of secondary copper sulfide ores. Leaching experiments were carried out in a sulphuric acid solution at different pH values, temperatures and concentrations of ferric ion using three kinds of ores. The grain size of the copper minerals in these ores was measured by QEMSCAN™. Although copper minerals in these ores consisted mainly of chalcocite, copper leaching rates varied greatly depending on each ore. In particular, the difference of leaching rates was more than 4 times in the early leaching stage.In the case of the slower leaching rate, the copper extraction could be increased from 15% to 58% after 0.5 days at 40°C and initial pH of 1.0 with 250mg/l of additional ferric ion.In the case of the faster leaching rate, the leaching rate could be increased by increasing the temperature and/or decreasing pH. However, the increase of the leaching rate was almost independent of additional ferric ion throughout the leaching stage. Furthermore, it was found that the grain size of copper minerals in the case of the slower leaching rate was about 1.5 to two times as coarse as that in the case of the faster leaching rate. It is concluded that, from the standpoint of reaction efficiency, the copper leaching behavior in the early leaching stage would be very sensitive to the grain size of copper minerals more than other leaching factors.