Effect of silver on the ferrous iron oxidizing ability of Thiobacillus ferrooxidans

The effect of silver on the iron oxidizing ability of Thiobacillus ferrooxidans 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 concentration, and Fe(II) concentration. The mechanism of the bacterially mediated oxidation of ferrous iron is found to be influenced by temperature 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 the microbial oxidation of Fe(II). In the presence of 10 mg/l silver, the reaction may be chemically controlled over the temperature range 5.5-25 degrees C, Inhibition of microbial Fe(II) oxidation in the presence 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) complex.