Bacterial Population In Sulfide Nickel And Copper Ore Bioleaching System And Its Bioleaching Efficiency

Using Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans to leach sulphide ores is an economic technique to treat the low grade ores and tailing ores. This technique has been widely used in industry these days. In this research, an A. ferrooxidans strain named ynxd-1 was isolated form an acidic mine drainage (AMD) collected from a copper mine drainage in Yunnan.16S rRNA gene sequence analysis showed that ynxd-1 belonged to Acidithiobacillus ferrooxidans. The optimal temperature and pH value for growth were 30℃and 1.8-2.5,respectively. Copper ore iron slurry was used as medium to cultivate and enrichment ynxd-1, and its capability of oxidizing irons Fe2+was further studied. After 72h incubation, the oxidation efficiency rised to 98.2%, this showed that yndx-1 have the potential ability to leach mineral. After 28 days leaching, the leaching efficiency of low-grade Ni sulfide ore was up to 56.4%, where as the control (without yndx-1) was just 15.7%. ynxd-1 showed a high ability of bioleaching.In order to obtain Leptospirillum strains from AMD, enrichment temperature and pH value were changed to 30℃and 1.5-2.0, respectively, and plenty of arc-shaped, S-shaped, wave-like strains were observed by micrograph. According their special morphological characteristics, they could determine to be Leptospirillum strains.In order to compare the leaching efficiency of strain ynxd-1 and the mixture of strain ynxd-1 with Leptospirillum strains obtained above, they were used in the bioleaching of Low-grade Ni sulfide ore respectively. After bioleaching for 28 days, the leaching efficiency of strain ynxd-1 and the mixture of strain ynxd-1 with Leptospirillum strains were 56.4%and 62.4%, respectively.In order to investigate the relationship between the micro-organism population change and the leaching rate, fluorescence in situ hybridization (FISH) technique was used to monitor the succession population change in the low-grade Ni sulfide ore bioleaching system. The result showed that in the preparation of the sample, the bioleaching sample should fix on slide glass covered with gelatin at 37℃for 4 hours and hybridization temperature should keep at 46℃. In 0-20 days, the major bacteria in the bioleaching system were Acidithiobacillus ferrooxidans yndx-1 and the leaching rate was 45%. But after leaching for 25 days and more, the major microbiol population changed to be Leptospirillum strains. It was showed that the increase of Leptospirillum strains had a high relationship with the rise of leaching rate in the bioleaching system.Fluorescence in situ hybridization (FISH) technique would benefit to monitor the microbiol population change in the bioleaching system and finally helped to rise the leaching rate.