Abstract
It is known that silver ions accelerate the dissolution of copper in the bacterial leaching of chalcopyrite. The enhancement effect of silver ions is attributed to the formation of silver sulfide on the surface of chalcopyrite. The presence of chloride ions would affect the enhancement effect of silver ions because silver ions precipitate as silver chloride with chloride ions. The purpose of this work was to study the effect of chloride ions on the bacterial leaching of flotation concentrates of chalcopyrite and sphalerite using Thiobacillus ferrooxidans with the addition of silver ions. Results obtained are summarized as follow,
(1) The addition of up to 100mg/l chloride ions enhanced the bacterial leaching of copper from a chalcopyrite flotation concentrate at the initial silver concentration of 50mg/l. The copper dissolution was accelerated with the addition of silver chloride powder.
(2) The yield of zinc from a sphalerite flotation concentrate after the bacterial leaching of 20 days decreased with increase in the initial silver concentration. The addition of silver ions hindered the oxidation of sphalerite with ferric ions. Chloride ions weakened the negative effect of silver ions on the bacterial leaching of sphalerite.
