Influence Of PH On Bioleaching Of Chalcopyrite By Using Moderately Thermophilic Mixed Microorganisms

Although great progress has been made in biometallurgy,few studies focus on microbial ecology in bioleaching systems.Especially in some bioleaching process,the information on microbial community structure and population dynamics as will as the interactions between the microorganisms is unclear.This paper purposes to regulate and optimize bioleaching pocess by studying the conections of pH with leaching parameters and microbial ecology.Chalcopyrite concentrate was leached by moderately thermophilic mixed microorganism,including Acidithiobacillus caldus,Leptospirillum ferriphilum,Sulfobacillus acidophilus,Sulfobacillus thermosulfidooxidans et.al.in a stirred tank bioreactor operated at 45℃.There were three experiments,keeping the stirred speed and the count of air pumped invariable.The temperature was always 45℃,leaching time was about 30 days in every experiment.The first experiment was not controlled pH;the second one was controlled pH as 2.5±0.2 at all the time;the third one was controlled pH as 1.2±0.2 at the whole pocess.In three experiments the changes of pH,Eh and concentration of metal ion were detected.Synchronously the method of Polymerase Chain Reaction-Restriction Fragment Length Polymorphism(PCR-RFLP) was used to analyze the succession of bacterial community.On the 8^th,the 16^th, the 24^th and the 30^th d,leachates were sampled to extract microorganism's DNA for analysis.The results show that copper recovery was 26.2%when pH was not controlled while it was 19.8%and 19.7%when pH was controlled at 2.5±0.2 and 1.2±0.2,respectively.pH can influence the production of jarosite.A lot of jarosite was produced at pH 2.5±0.2 while much less jarosite was produced at pH 1.2±0.2.And when pH was not controlled,the situation was between the above two conditions.The results indicate that only two species,At.caldus and L. ferriphilum were detected.Microbial diversity was simple in stirred tank bioreactor.pH has great influences on community structure of microorganism.When pH was not controlled,at the beginning of bioleaching process, At.caldus was the predominant species,accounted for 96%of the whole community.With the process of leaching,L.ferriphilum gradually increased and replaced At.caldus,and accounted for 69%in the later stage of bioleaching.When pH was controlled,L.ferriphilum was always the predominant species.The abundance of At.caldus in the community at pH 2.5±0.2 was higher than the situation at pH 1.2±0.2.