Shake flask and column bioleaching of a pyritic porphyry copper sulphide ore

The purpose of this study was to test the feasibility of using bacterial leaching to solubilize copper from a porphyry sulphide ore, a part of the Sarcheshmeh Copper Complex. The bulk ore sample contained 18% pyrite and 0.8% Cu mostly as secondary chalcocite and Cu oxides. Mineral microscopy showed that pyrite grains in this porphyry ore were coated by chalcocite. Conventional flotation could not be used for ore beneficiation because Cu-sulphide could not be selectively separated from pyrite and consequently the flotation concentrate contained too much Fe and less Cu. Hence bioleaching was tested as an alternative process for this ore. The bioleaching was tested with a consortium of mesophilic acidophiles comprising Leptospirillum and Acidithiobacillus spp., originally enriched from the Sarcheshmeh site. Several mineral salt formulations were tested in shake flask bioleaching experiments. These experiments resulted in 89–92% Cu yields with no discernible differences between the different formulations. Sterile controls representing chemical acid leaching resulted in about 60% Cu solubilization. For column bioleaching experiments, ore samples (~ 40 kg each; 75% − 12 mm) were agglomerated and treated with a schedule of 4 days of irrigation and 4 days of rest period. The column bioleaching tests yielded Cu recoveries of about 90%. The abiotic control had 50% Cu recovery. Thus the test results were favorable for using the bioleaching approach for this Cu-ore material.

► Bioleaching of a porphyry Cu ore was tested in shake flask and column experiments.
► The ore was rich in pyrite with mostly chalcocite coating of surfaces and fractures.
► About 90% of Cu content was leached by bacteria in shake flasks and columns.
► Several mineral salts solutions were tested but had little influence on Cu recovery.
► Ore agglomeration did not increase the recovery of Cu in column bioleaching.