The effect of silver on the iron oxidizing ability of Thiobacillus fer
rooxidans was studied using electrochemical and other physicochemical
techniques, Electrochemical investigation was conducted using a method
based on change in redox potential, The rate of ferrous ion oxidation
is influenced by pH (optimum pH range is 1.7-2.0), microbial cell con
centration, and Fe(II) concentration. The mechanism of the bacterially
mediated oxidation of ferrous iron is found to be influenced by tempe
rature changes, In the vicinity of the optimum temperature (25 degrees
C), the reaction is likely to be controlled by the diffusion of Fe(II
) ions, whereas below the temperature range 18-25 degrees C, chemical
reaction may be the rate-controlling factor. Ag(I) is detrimental to t
he microbial oxidation of Fe(II). In the presence of 10 mg/l silver, t
he reaction may be chemically controlled over the temperature range 5.
5-25 degrees C, Inhibition of microbial Fe(II) oxidation in the presen
ce of silver may take place via a mixed mechanism in which silver may
bind with both the iron oxidizing enzyme(s) and the enzyme-Fe(II) comp
lex.