Study On Bioleaching Of Chalcopyrite By Acidithiobacillus Ferrooxidans

Because of over-exploited mineral resources and the decreasing of easy-handle mineral, the demand for efficient use of low-grade minerals is more urgent. Bioleaching is a cross subject of biotechnology and metallurgy engineering, which provides an important method for solving the resource scarcity problem. It also meets the requirements of resources and environmental, so this green metallurgy technology will have a brilliant future.Taken Acidithiobacillus ferrooxidans(A.ferrooxidans) as object of the research, this paper identified the experimental strains by molecular biology and studied its culture to achieve high efficiency. And then studied the differences of chalcopyrite leaching system under different conditions and determined the key factors to improve the chalcopyrite leaching rate. Finally, a sulfur-oxidizing bacteria with low pH tolerant was screened from mines, promising to be applied in mixed bioleaching of chalcopyrite.Extraction the 16S rDNA gene from the experimental strains CUMT-1 and identified it by molecular biology. The strains CUMT-1 is similar with A.ferrooxidans ATCC23270 by 100%.Efficient culture of A.ferrooxidans by fed-batch culture was studied. First, optimized the culture conditions of A.ferrooxidans in flask and determined the strategies of fed-batch phase is maintain the Fe2+in the concentration range of 4g/L to 8g/L. When feeding in 9K medium and sulfide minerals medium, the conversion rate and production intensity will be increased while the specific growth rate doesn't decrease. The biomass reached 4×108 cells/mL within 39h when feeding in 9K medium, and the conversion rate and production intensity increased by 32% and 128% respectively, compared to the batch culture. But when feeding in sulfide minerals medium, a better outcomes was achieved. The biomass was 6.25×108 cells/mL after 39h of incubation, and the conversion rate and production intensity increase was 80% and 259% respectively when compared to the batch culture.Starting from microbial growth and metabolisms, chalcopyrite leaching was studied and then determined the key factors for chalcopyrite leaching. By comparing the bioleaching and chemical leaching, a result that the leaching of chalcopyrite is mainly mediated by microorganism is clear. The best inoculum volume is 10% which was confirmed by single factor analysis, in that situation the biomass of A.ferrooxidans which oxidizing sulfide was highest and the leaching rate for the highest 17%. After acclimated, the leaching rate increased to 25%. If further removing the jarosite in inoculum, the leaching rate is higher, as 30%. The microbial metabolisms, biomass and the jarosite generation and coating were the key factors which affected the chalcopyrite leaching rate after analysis of the above bioleaching experiments.A new strain with bioleaching function was found and identified. A sulfur-oxidizing bacteria with low pH tolerant was screened from the pregent solution pond of Zijinshan Gold-copper Mine located in Fujian province. The isolate was identified as Acidithiobacillus sp. based on the 16S rDNA sequence alignment and phylogenetic tree analysis. And the strains also have higher sulfur oxidation rate even the medium pH is less than 1, that feature would benefit chalcopyrite leaching.