Bioleaching of silver sulfide

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To examine the application of Thiobacillus ferrooxidans in the leaching of silver sulfide, effect of silver ion on the ferrous ion and elemental sulfur oxidation activities of T. ferrooxidans was investigated.11 strains of T. ferrooxidans used in this study were isolated from the waters of sulfide mineral mines and a smelter in Japan.Silver ion inhibited ferrous ion oxidation activity of T. ferrooxidans. Oxidation rate decreased as silver concentration increased. Maximum silver concentration that bacteria could oxidize. 90% of ferrous ion(initial concentration 4.0x10^<-2>mol/1)at is from 0. llppm to 0.28ppm. A Copper tolerant strain that grew, -in the mediums with gradually increasing copper concentration up to-13g/l had higher silver tolerance. The strain oxidized 90% of ferrous ion at the silver concentration of l. Oppm. A nickel tolerant strain that grew in the medium with gradually increasing nickel concentration up to log/l had less silver tolerance.Elemental sulfur oxidation activity of T. ferrooxidans was inhibited at the silver concentration of 5ppm. An adapted strain that grew in the medium with gradually increasing silver concentration oxidized elemental sulfur at the silver concentration of 5ppm.