In order to study the mechanism for bacteria leaching of pitchblende

several leaching experiments were conducted

including three powder leaching experiments with bacteria and iron

with bacteria and without iron

without bacteria and iron

and two specimen leaching experiments with bacteria and without iron

without bacteria and iron. Variations in the concentrations of bacteria

ferrous ions

total iron ions and uranium ions

pH value and redox potential of the leaching solutions were monitored in the powder leaching systems. The contents of O

Mg

K

P

S

Fe and U in the tailings from powder leaching experiments were analyzed and the surface morphology of the samples after leaching were observed. Results of the powder leaching experiments show that Acidithiobacillus ferrooxidans can effectively oxidize ferrous ions

sulfur in reduction state and elemental sulfur

resulted in the increase in redox potential and the decrease in pH value. In the leaching system with bacteria and iron

the leaching of uranium from the ore can be accelerated and the leaching rate is increased with the higher concentrations of bacteria and total iron ions

the lower pH value and the higher redox potential. Although the concentration of the total iron ions is relatively low in the leaching system with bacteria and without iron

the bacteria can also accelerate the leaching of uranium from the ore and increase the leaching rate. Results of the specimen leaching experiments indicate that the pitchblende ore has been directly oxidized by the bacteria

since corrosion pits can be observed on the specimen surface in the leaching system with bacteria and without iron. Corrosion pits have not been observed on the specimen surface in the leaching system without bacteria and iron.