Improving chalcopyrite biodissolution form low grade Indian copper ore by microbial consortia

Abstract

Using a consortium of bacteria such as Acidithiobacillus ferrooxidans (A.ferrooxidans) and Acidithiobacillus thiooxidans (A.thiooxidans), isolated in Silverman and Lundgren Media from the source mine water, the biodissolution of copper from untapped lean ores of Malanjhkhand Copper Project (MCP), India was investigated. Inocula of both iron-oxidizing and sulfur-oxidizing bacteria in the ratio of 4:1 (A.ferrooxidans to A.thiooxidans) were used as such (without adaptation on the ore) for the bio-leaching of copper from the low grade chalcopyrite ore (0.27% Cu) of granite origin. In general, the efficiency of the microbiological process is often low because this mineral is one of the most refractory ores of copper for bacterial attack. A maximum copper recovery of 69.4% was obtained in 30 days at 1.5 pH, 35oC temperature, 10% (w/v) pulp density with particles of <50 µm size. High copper recovery at 1.5 pH may be correlated with an increase in redox potential from 340-642 mV and increase in bacterial population from 3x107 to 6.07x108 cells/mL in 30 days. This research has shown the possibility to enhance the leachability of chalcopyrite to achieve high copper extraction in the presence of a consortium of mesophiles. Importance of using A.thiooxidans as a part of consortium in facilitating copper solubilization is also highlighted in the paper.