The formation of jarosite in the presence of Acidithiobacillus ferrooxidans (A. ferrooxidans) was researched to ascertain the conditions of producing minimum precipitation. The effects of salt concentration and pH on the characteristics of jarosite formed in K 2 SO 4 /(NH 4 ) 2 SO 4 -FeSO 4 inorganic salt solution and 9K medium were studied by using the measurements of scanning electron microscope, X-ray diffraction, Fourierism transform infrared analysis, thermogravity/differential thermogravity analysis and particle size analysis to evaluate the product. The results indicate that the formation of jarosite begins when A. ferrooxidans reaches logarithmic growth phase in 9K medium, and a higher pH value is beneficial to the formation of jarosite. The jarosite formed in 9K medium has smaller and more concentrative particle size and smoother surface than that formed in inorganic salt solution.

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By using thiobacillus ferrooxidans (T. f) from Qixiashan, Hubei Province, China, the adsorption characteristics of T. f on surface of sulfide mineral were studied. The influences of adsorption time, pH value, temperature, initial inoculated concentration of bacteria, concentration of sulfide mineral powder, and variety of minerals on the adsorption characteristics were firstly investigated by using the ninhydrin colorimetric method, and the changes of contact angles and Zeta potentials of mineral surface during the bacterial adsorption were then determined. The results show that when the leaching experiments are performed for a long time from several days to a month, the maximal quantity of adsorption of T. f on the surface of pyrite is obtained under the following conditions: leaching for 20 d, pH value in range of 1 -2 and temperature at 30 "C, respectively; when the bio-leaching experiments are performed for a shorter leaching time, the maximal quantity of adsorption is obtained under the conditions: bio-leaching for 2 h, at 2.4X 107 cell/mL of initial inoculated bacteria concentration, and at 10% of mineral powder concentration; and the adsorption quantities are different form one sulfide mineral to another, and the adsorption of T. f on the surface of sulfide minerals includes three phases: increasing phase, stationary phase and decreasing phase.

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