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Leaching
of Zinc Sulfide by Thiobacillus ferrooxidans: Applied
and Environmental Microbiology, Dec 1999, p 5285-5292 This
paper reports the results of leaching experiments conducted with
and without Thiobacillus ferrooxidans at the same conditions in
solution. The extent of leaching of ZnS with bacteria is significantly
higher than that without bacteria at high concentrations of ferrous
ions. A porous layer of elemental sulfur is present on the surfaces
of the chemically leached particles, while no sulfur is present
on the surfaces of the bacterially leached particles. The analysis
of the data using the shrinking-core model shows that the chemical
leaching of ZnS is limited by the diffusion of ferrous ions through
the sulfur product layer at high concentrations of ferrous ions.
The analysis of the data shows that diffusion through the product
layer does not limit the rate of dissolution when bacteria are present.
This suggests that the action of T. ferrooxidans in oxidizing the
sulfur formed on the particle surface is to remove the barrier to
diffusion by ferrous ions.
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