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With rapidly development metallurgical industry , the mine producing more and more tailings and bringing environmental problems Increasingly prominent, In the mine development, microbial leaching technology has been widely studied and applied.In microbial leaching technology,Acidithiobacillus ferrooxidans（At.f）and Acidithiobacillus thiooxidans（At.t） mixed Thiobacillus species with complementary promoting role,At.f is one of the dominant bacteria in the course of bioleaching, in certainconditions At.t bacteria can enhance the role of bacteria leaching. In this study, we used At.f and At.t mixed bacteria leaching Yangla Copper mine tailing,the mixed bacteria obtained by enrichment and pure culture on pyrite acidic water form Fengjie. Experiment, added different concentrations of citric acid and Ag2SO4 to the extraction system , studied on the change of leaehing rate by different pulp concentration. Experimental test Ev, pH, Fe2+ and Cu2+ in the leaching system,studied citric acid, Ag2SO4, pulp concentration and other factor on the impact of leaching system,for the mixed bacteria are uesed leaching Copper mine tailings research and application provides a theoretical basis.In this study, Acidithiobacillus ferrooxidans （At.f） and Acidithiobacillus thiooxidans （At.t） mixed bacteria are uesed leaching brass tailings. Experimental bacteria from the pyrite Fengjie acid water collection,After enrichment and pure cultur,the same amount of bacteria added in the leaching experiment, Experiment added to different concentrations of citric acid to enhance their leaching rate.The results show that: in a certain range of citric acid concentration can promote of chalcopyrite bioleaching tailings.On the early ,because the bacteria adapt to the new environment, which began to use the nutrients to growth and reproduction, the number of bacteria rapid increase and its oxidation enhanced, the various parameters of bioleaching system are changes very fast.Citric acid concentration of 0.5%, the system leaching results were better, leaching rate is relatively high. After a month of extraction experiments show that: when the bacterial concentration is 10%, and the slurry concentration is 1% the leaching effects are best , leaching rates were generally high. when add the citric acid concentration is 0.1%, the highest rate of leaching is to 37.8%. After adding the catalyst Ag2SO4, the leaching experimental results show that the overall leaching effects are better, indicating that Ag+promote on the leaching of chalcopyrite tailings is obvious . We found that the concentration of Ag+added is 0.01%, the leaching effect is the best and the corresponding leaching is higher.After the end Extraction,the ferrous oxidation rate of the system is about 90%, indicating that the bacterial activity is very strong and with highly oxidized, that is to say leaching results is best.Overall, when added Ag+, the system leaching effect has increased obviously and the leaching rate significantly increase , the highest leaching rate is 75.4%. The results showed that in a certain concentration range, add Ag+ on the promotion of chalcopyrite bioleaching tailings is obvious.
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