Technical Note

The role of chemolitotrophic bacteria in an oxide copper ore heap leaching operation

S.A.S. Baghery1, A.R. Shahverdi2, M. Oliazadeh3, A.M. Alfantazi4,*

1 R & D Division, National Iranian Copper Industries Company, Rafsanjan, Iran
2 Biotechnology Dept., Faculty of Pharmacy, Tehran Medical Sciences University, Tehran, Iran
3 Faculty of Mining Engineering, Tehran University, Tehran, Iran
4 Department of Metals and Materials Engineeing, University of British Columbia, Vancouver, BC, Canada

Accepted 2 December 2004


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.

Keywords: Bioleaching, Sulfide minerals, Copper, Heap leaching

* Corresponding author
   E-mail : alfantaz@interchange.ubc.ca