Effect of introduction of exogenous strain Leptospirillum ferriphilum YSK on functional gene expression,structure,and function of indigenous consortium during pyrite bioleaching

Leptospirillum ferriphilum YSK was added to a native consortium of bioleaching bacteria including Acidithiobacillus caldus,A.thiooxidans,A.ferrooxidans,Sulfobacillus thermosulfidooxidans,Acidiphilium spp.,and Ferroplasma thermophilum cultured in modified 9K medium containing 0.5%(W/V)pyrite.The bioleaching efficiency markedly increased.Changes in community structure and gene expression were monitored with real-time PCR and functional gene arrays.Dynamic changes that varied in different populations in the consortium occurred after the addition of L.ferriphilum YSK,with growth of A.caldus S1,A.thiooxidans A01,Acidiphillum spp.DX1-1 promoted the growth of Ferroplasma L1,inhibited that of S.thermosulfidooxidans ST,and exerted little effect on that of A.ferrooxidans CMS.Genes encoding ADP heptose,phosphoheptose isomerase,glycosyltransferase,biotin carboxylase,and protoheme ferrolyase from L.ferriphilum,acetyl-CoA carboxylase from Acidiphillum spp.,and doxD from A.caldus were up-regulated in 0-20 h.Genes encoding lipid A disaccharide synthase LpxB,glycosyl transferase,and ADP heptose synthase from A.ferrooxidans were up-regulated in 0-8 h and then down-regulated in 8-20 h.Genes encoding ferredoxin oxidoreductase from Ferroplasma sp.were up-regulated in 0-4 h,down-regulated in 4-16 h,and again up-regulated in 16-20 h.CbbS from A.ferrooxidans was down-regulated in 0-20 h.

In situ characterization of natural pyrite bioleaching using electrochemical noise technique

An in situ characterization technique called electrochemical noise（ECN） was used to investigate the bioleaching of natural pyrite.ECN experiments were conducted in four active systems（sulfuric acid,ferric-ion,9k culture medium,and bioleaching solutions）.The ECN data were analyzed in both the time and frequency domains.Spectral noise impedance spectra obtained from power spectral density（PSD）plots for different systems were compared.A reaction mechanism was also proposed on the basis of the experimental data analysis.The bioleaching system exhibits the lowest noise resistance of 0.101 MΩ The bioleaching of natural pyrite is considered to be a bio-battery reaction,which distinguishes it from chemical oxidation reactions in ferric-ion and culture-medium（9k） solutions.The corrosion of pyrite becomes more severe over time after the long-term testing of bioleaching.

Study on bioleaching of refractory gold ore (Ⅰ)──Mechanism on bioleaching of pyrite by Thiobacillus ferrooxidans

The variation of main parameters including ion concentration, pH value, potential and biomass was examined in bioleaching pyrite. The pH value of the solution decreased obviously. Most of T.ferrooxidans adhered to the surface of pyrite. The surface properties of pyrite and leached products were determined by SEM, EDS and XRD. Pyrite was corroded selectively by T.ferrooxidans and sulfur in pyrite was leached preferentially. The primary product for bioleaching pyrite was jarosite. Based on these results, it can be found that pyrite is oxidized mainly through the direct role of T.ferrooxidans . A band model for bioleaching pyrite was built, by which the bioleaching process was explained theoretically. The model shows that the holes, which are injected into the valence band of pyrite through adhered T.ferrooxidans , result from dissolved oxygen in the solution.

An experimental study of pyrite bio-leaching as a way to control spontaneous combustion

Bio-leaching of pyrite by native strains of acidophilic bacteria was examined by laboratory scale tests. Three groups of batch trials in agitated flasks and three continuous column leaching tests were performed. The leaching ability and efficiency of native bacteria was greatly improved by adaptation of the bacteria to the test conditions. These cultivated bacteria were then used for the leaching process. The changes in solution pH, Eh, Fe2~ concentration, and sulfate ion concentration were monitored throughout the tests. A portion of the pyritic sulfur is transformed into soluble sulfate ion. The desulfur- ization ratio of＇42.6g was obtained in a flask shaking test and a ratio of 39.4g was obtained during column leaching. A weight gain test was performed on leached and unleached samples by exposing the samples to humid air for several days. A smaller weight gain of the bio-leached samples indicates that removing sulfur from the sulphide ore helps reduce its oxidation rate and the potential for spontaneous combustion.