Perth Laboratory – Public Seminar Series 2007

Mining copper with extremophilic microbes

Jason Plumb, Rebecca Hawkes, Christina Haddad, Matthew Stott, Helen Watling (CSIRO),
David Readett (Minara Resources Limited) and

Peter Franzmann
Program Leader
Urban and Industrial Water Program
CSIRO Land and Water

Thursday 8 November 2007 at 3.30pm, CSIRO Auditorium

Abstract

About 20% of world copper production is now recovered biologically by heap bioleaching of chalcocite (Cu₂S). Chalcopyrite (CuFeS₂) is a much more significant resource of copper-mineral sulfide, however economic biological copper recovery from chalcopyrite is more problematic. Recovery rates and yields of copper from chalcopyrite in heap bioleach operations have not been great enough to make chalcopyrite heap bioleaching an economically attractive investment for the mining industry generally, although much laboratory and field testing is underway.

The rate of bioleaching of copper from chalcopyrite slows during its oxidation, at about the same time that jarosite precipitates form on the mineral surface. Bioleaching of chalcopyrite can be very rapid in the laboratory if thermophilic Archaea are used.

At industrial scale, the microbiology of higher temperature chalcocite bioleach operations has been investigated by both culture and culture-independent techniques, at the Nifty Copper Mine in the Pilbara region of Western Australia, and the Monywa Project operated by the Myanmar Ivanhoe Copper Company in Myanmar. Although temperatures near 70°C were reached in a heap at the Nifty Copper Mine, thermophiles were absent. Moderate thermophiles that operate up to a maximal temperature of ca. 63°C populated both commercial operations. Sulfobacillus spp. occurred in both, and a new moderately thermophilic species of Ferroplasma occurred in great numbers in the Myanmar operation, along with members of the species Acidithiobacillus caldus and Leptospirillum ferriphilum.

Hyperthermophilic bioleaching Archaea that grow optimally at 70°C or greater have been isolated from many geothermally heated natural environments and some of our own chalcopyrite-oxidising strains operate across the temperature range of 50 to 80°C. Some, such as the newly described Archaeon, Acidianus sulfidivorans, grow at extremely low pH (down to pH 0.35). Definitive reports of hyperthermophilic Archaea in commercial copper heap bioleach operations have not been made, although there is a paucity of information in the public domain on the microbial ecology of commercial heap bioleach operations. Hyperthermophilic Archaea are used in commercial tank bioleach operations using concentrates, although the tanks are inoculated with the appropriate strains. Successful application of hyperthermophiles for economic chalcopyrite bioleaching awaits better understanding of their physiology and ecology, and their integration into the engineered environment of a heap.

About the speaker

Peter Franzmann completed his PhD at the University of Queensland in 1983. He then worked on Antarctic microbial ecology in Australia, Antarctica and Germany before joining CSIRO in 1994 to work on urban and industrial water issues. Peter currently leads CSIRO Land and Water's Urban and Industrial Water Program.

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