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Technical
Note The role of chemolitotrophic
bacteria in an oxide copper ore heap leaching operation
The role of chemolitotrophic bacteria in the oxidation of copper sulfide
minerals in oxide copper ore heap leaching operation at Sarcheshmeh Copper
Mine has been investigated. It was determined that about 34% of the heap
copper content existed in the form of sulfide minerals, 1/3 of which has
been leached quit naturally, and the remaining copper as oxide ores. As
such, the heap considered in this study, consisted of a mixed sulfide and
oxide copper ore. Previous samplings from PLS of the heap showed there were
a significant amount of native chemolititrophic bacteria (more than
105cell/ml) which belonged to the genera Acidithiobacillus, Leptospirillum
and Sulfobacillus. To investigate a probable relation between the existence
of bacteria and the leached sulfide ores, several samples were taken from
different depths of a newly leached pad and analyzed for their bacterial
number, pH, oxidation-reduction potential (ORP), total soluble iron (TSI),
pyretic iron and copper content. It was found that bacteria had an important
effect on the heap pH, solution potential, and TSI from the top of the heap
down to the depth where enough oxygen could diffuse. As these are very
active oxidizing bacteria, they created favorable conditions (such as low pH
and high ORP values) for copper sulfide ore oxidation. Copper extraction
from sulfide ores in this chemical heap leach operation can then be
attributed to the bacterial activity especially at the top levels of the
heap. It is possible that the remaining sulfide copper ore in the heap can
be leached biologically after completion of chemical leaching. |
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