Study On Bioleaching Of Low-Grade Chalcopyrite Mutated By Mixed Bacteria And Utraviolet-Ray

With the development of bioleaching,people pay more attention to the bacteria which play important role in the course of bioleaching.The bacteria derive the energy required for its growth from the oxidation of Fe²⁺,S⁰,and other metal ions.The mixed bacteria can raise the bioleaching rate,thus mixed bacteria bioleaching has become one of hot research field today.Thiobacillus ferrooxidans(T.f)is one of the important bacteria in the course of bioleaching,in some special conditions moderately thermophilic bacteria(T.a)can reinforce the bioleaching ability of T.f.In this thesis,a strain of T.a was isolated from acid hot spring,and a preliminary investgation was made on it,the medium was as follows:9K+tryptone.The mixed bacteria(T.m)was made by T.f and T.a.The mixed condition was studied,and the bacteria were mutated by Utraviolet-ray,then the method of compound mutation with chemicals was used.We come to the conclusion that the mixing ratio of the two strains (T.f and T.a)is 1:2,the best mutation time is 120s,and the UV irradiation distance is 30cm.The results indicated that low temperature treatment was beneficial to increase positive mutation rate.The best time of compound mutation with NaNO₂ is 10min.The process of bioleaching chalcopyrite has been studied in this research by comparing the chalcopyrite leaching performance of single strains and mixed bacteria. The effect of pre-and post UV mutagenesis and compound mutation have been studied. The results show that the pulp density of 5%,inoculation amount 10%,pH2.0,and 30℃are the best condition for T.f and also the pulp density of 10%,inoculation amount 5%,pH2.0,and 30℃for T.m.The learching rate with pre-and post T.f is 14.65%and 20.14,increasing by 38%.Yet the learching rate with pre-and post T.m is 18.25%and 25.72%,increasing by 40%.Comparition between T.f and T.m only mutaed by UV mutagenesis and,compound mutation,it was found that leaching rate had little change. But compound mutation can reduce the repair rate of positive mutation obviously.