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Appl. Environ. Microbiol., Jul 1997, 2586-2592, Vol 63, No. 7
PI Harvey and FK Crundwell
The concentrations of ferrous and ferric ions change dramatically during
the course of the batch experiments usually performed to study the kinetics
of the bacterial oxidation of ferrous ions and sulfide minerals. This
change in concentration of the iron species during the course of the
experiment often makes it difficult to interpret the results of these
experiments, as is evidenced by the lack of consensus concerning the
mechanism of bacterial leaching. If the concentrations of ferrous and
ferric ions were constant throughout the course of the batch experiment,
then the role of the bacteria could be easily established, because the rate
of the chemical leaching should be the same at a given redox potential in
the presence and in the absence of bacteria. In this paper we report an
experiment designed to obtain kinetic data under these conditions. The
redox potential is used as a measure of the concentrations of ferrous and
ferric ions, and the redox potential of the leaching solution is controlled
throughout the experiment by electrolysis. The effects of ferrous, ferric,
and arsenite ions on the rate of growth of Thiobacillus ferrooxidans on
ferrous ions in this redox-controlled reactor are presented. In addition,
the growth of this bacterium on ferrous ions in batch culture was also
determined, and it is shown that the parameters obtained from the batch
culture and the redox-controlled batch culture are the same. An analysis of
the results from the batch culture indicates that the initial number of
bacteria that are adapted to the solution depends on the concentrations of
ferrous and arsenite ions.
Copyright © 1997, American Society for Microbiology
Growth of Thiobacillus ferrooxidans: a Novel Experimental Design for Batch Growth and Bacterial Leaching Studies
School of Process and Materials Engineering, University of the Witwatersrand, Johannesburg, South Africa
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