High-temperature Bacteria Combination Of Leaching Of Chalcopyrite And Bacterial Population Structure And Succession Laws

A high temperature-tolerating thermoacidophilic archae(Sulfolobus acidocaldarius; KY-2 strain)was isolated from water samples collected from a hot sulfur-containing spring in the Yunnan Province,and was used in bioleaching experiments of a low-grade chalcopyrite ore.The KY-2 grow at temperature ranging from 40 to 80℃,with 65℃being the optimum temperature,and at pH values of 1.5 to 4.0,with an optimum pH value of 2.0.The bioleaching experiments of the chalcopyrite ore were conducted in both laboratory batch bioreactors and leaching columns.The results obtained from the bioreactor experiments showed that the KY-2 bioleaching rate of copper reached 97%for a 12-day leaching period,while the bioleaching rate was 32.43%for Acidithiobacillus ferrooxidans (A.f)leaching for the same leaching time.In the case of column leaching,tests of a two-phase leaching(196days),that is,a two-month(56days)A.f leaching in the first phase, followed by a 140-day KY-2 leaching in the second phase were performed.The average leaching rate of copper achieved for the 140-day KY-2 leaching was 195mg/(L.d),while for the control experiments,it was as low as 78mg/(L.d)for the A.f leaching,indicating that the KY-2 possesses a more powerful oxidizing ability to the chalcopyrite than A.f.Therefore,it is suggested that the two-phase leaching process be applied to for the heap leaching operations,whereas,the KY-2 can be used in the second phase when the temperature inside the heap has increased,and the primary copper sulfide minerals have already been partially oxidized with A.f beforehand in the first phase.In order to find out the reaction mechanism of the bacteria with chalcopyrite,the bacterial population composition in a bioleaching system of a low grade copper sulphide ore consisting mainly of chalcopyrite was investigated.By using a 9K culture medium,14 pure strains of mesophiles were isolated from the batch stirred leaching pulp of the ore.It was found that the copper leaching efficiencies for these pure strains were all lower than before isolating,indicating that there exists a synergistic effect between these strains of the domestic bacteria in the batch stirred bioleaching process of the ore.It was also found that by the sequence analysis of 16S rDNA,three of the 14 strains,strain YK8,strain YK12 and strain YK14,which were random-sampled from the 14 strains,were highly relatived to Acidithiobacillus ferrooxidans,with 99%sequence similarity,though were very different in the oxidation power from each other.Therefore these three strains should be all identified as the species of Acidithiobacillus ferrooxidans,exhibiting the diversity of singleness of the bacteria community.The fact that the bacterial population composition of the batch stirred bioleaching system was dominated by the species of Acidithiobacillus ferrooxidans indicates that the mechanism of the bacterial oxidation in this case is a direct reaction.There were the marked differences of Fe²⁺oxidation rate of various pure strains at different period of time and notable change about the copper leaching efficiency for various bacteria induced by different culture medium containing different energy sources of the batch stirred bioleaching system.By the direct approach and PCR-DGGE analysis,these results indicate at molecular level that the batch stirred bioleaching pulp of the ore was inoculated and cultivated and transferred 5 times in Starkey culture medium containing sulfur powder(S°)as energy sources,whose dominant bacteria was Acidithiobacillus ferrooxidans A.f,rather than Acidithiobacillus thiooxidans A.t that people were used to think of.By the PCR-DGGE analysis,there were 6 bands in DGGE patterns of PCR amplified 16S rDNA(V3-V6)of bacterial sample of different period of time in column bioleaching process,such as 01 band,02 band,03 band,04 band and 05 band whose corresponding to bacteria all were Acidithiobacillus ferrooxidans A.f.The dominant bacteria in the column bioleaching process of a low grade copper sulphide ore consisting mainly of chalcopyrite was Acidithiobacillus ferrooxidans A.f.During the column bioleaching process of 63-day,the bacterial population succession took place.For all 6 bands corresponding to bacteria were Acidithiobacillus ferrooxidans A.f. The bacterial succession came about among bacterial strains of Acidithiobacillus ferrooxidans A.f.Using a 9K culture medium,3 pure strains of mesophiles were isolated which were random-sampled from the column bioleaching pulp of the ore.By the sequence analysis of 16S rDNA,it was found that 3 pure strains were highly relatived to Acidithiobacillus ferrooxidans,with 99%sequence similarity and all were identified as the species of Acidithiobacillus ferrooxidans A.f.These results were as same as the PCR-DGGE analysis and indicate that the dominant bacteria in the column bioleaching process of a low grade copper sulphide ore consisting mainly of chalcopyrite was Acidithiobacillus ferrooxidans A.f.During batch stirred bioleaching process using thermoacidophilic archae(KY-2),The Fe³⁺concentration in solution was very low at all the time,but copper leaching rate was very high.This case indicates that the mechanism of the thermoacidophilic archae oxidation is a direct reaction.In the early stages of the column bioleaching of a low grade copper sulphide ore consisting mainly of chalcopyrite,the secondary copper sulphide ore which is dissolved easily chose 02 band and 05 band corresponding to bacterial strains of Acidithiobacillus ferrooxidans A.f,the primary copper sulphide ore which is dissolved hardly selected 01 band, 02 band,03 band,04 band and 05 band corresponding to the bacterial strains of Acidithiobacillus ferrooxidans A.f.This study supports that the sulfur(S°)layer doesn't arise the passivation of chalcopyrite during batch stirred bioleaching process using thermoacidophilic archae(KY-2).The superficial layer of bioleaching residue of chalcopyrite consisted mainly of sulfur(S°)and didn't weaken the oxidation efficiency of thermoacidophilic archae for copper leaching rates were very high in whole bioleaching process.