| 1. |
- Karnachuk, Olia V, et al.
(författare)
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Sulfate reduction potential in sediments in the Norilsk mining area, northern Siberia
- 2005
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Ingår i: Geomicrobiology Journal. - Philadelphia : Taylor & Francis. - 0149-0451 .- 1521-0529. ; 22:1-2, s. 11-25
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to characterize the distribution and activity of sulfate-reducing bacteria in tailings and sediments impacted by effluents from mining and smelting operations in the Norilsk area in northern Siberia. The Norilsk mining complex involves three smelter operations, a hydrometallurgical plant, and extensive tailings areas located in the permafrost zone. Sulfate reduction rates measured with a (35)SO(4)(2-) tracer technique under various in-situ conditions ranged from 0.05 to 30 nmol S cm(-3) day(-1). Acetate and glucose addition greatly stimulated sulfate reduction, whereas lactate had less effect. The most pronounced stimulation of sulfate reduction (6.5-fold) was observed with phosphate amendment. Most-probable-number (MPN) counts of sulfate-reducing bacteria in media with glucose, ethanol, lactate, and acetate as electron donors were generally highest at around 10(7) cells ml(-1). The actual MPN counts varied with the sample, electron donor, and incubation conditions (pH 7.2 vs. pH 3.5; 28 degrees C vs. 4 degrees C). Enrichment cultures of sulfate-reducing bacteria were established from a sample that showed the highest rate of sulfate reduction. After multiple serial transfers, the dominant sulfate-reducers were identified by fluorescence in situ hybridization using genus and group-specific 16S rRNA-targeted oligonucleotide probes. Desulfobulbus spp. prevailed in ethanol and lactate enrichments and the Desulfosarcina-Desulfococcus group dominated in acetate and benzoate enrichments. Psychrophilic Desulfotalea-Desulfofustis and moderately psychrophilic Desulforhopalus spp. were identified in enrichments incubated at 4 degrees C, but they were also found in mesophilic enrichments.
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| 2. |
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| 3. |
- Dopson, Mark, et al.
(författare)
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Mineral and iron oxidation at low temperatures by pure and mixed cultures of acidophilic microorganisms.
- 2007
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Ingår i: Biotechnol Bioeng. - : Wiley. - 0006-3592 .- 1097-0290. ; 97:5, s. 1205-15
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Tidskriftsartikel (refereegranskat)abstract
- An enrichment culture from a boreal sulfide mine environment containing a low-grade polymetallic ore was tested in column bioreactors for simulation of low temperature heap leaching. PCR-denaturing gradient gel electrophoresis and 16S rRNA gene sequencing revealed the enrichment culture contained an Acidithiobacillus ferrooxidans strain with high 16S rRNA gene similarity to the psychrotolerant strain SS3 and a mesophilic Leptospirillum ferrooxidans strain. As the mixed culture contained a strain that was within a clade with SS3, we used the SS3 pure culture to compare leaching rates with the At. ferrooxidans type strain in stirred tank reactors for mineral sulfide dissolution at various temperatures. The psychrotolerant strain SS3 catalyzed pyrite, pyrite/arsenopyrite, and chalcopyrite concentrate leaching. The rates were lower at 5 degrees C than at 30 degrees C, despite that all the available iron was in the oxidized form in the presence of At. ferrooxidans SS3. This suggests that although efficient At. ferrooxidans SS3 mediated biological oxidation of ferrous iron occurred, chemical oxidation of the sulfide minerals by ferric iron was rate limiting. In the column reactors, the leaching rates were much less affected by low temperatures than in the stirred tank reactors. A factor for the relatively high rates of mineral oxidation at 7 degrees C is that ferric iron remained in the soluble phase whereas, at 21 degrees C the ferric iron precipitated. Temperature gradient analysis of ferrous iron oxidation by this enrichment culture demonstrated two temperature optima for ferrous iron oxidation and that the mixed culture was capable of ferrous iron oxidation at 5 degrees C. (c) 2006 Wiley Periodicals, Inc.
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| 4. |
- Dopson, Mark, et al.
(författare)
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Silicate mineral dissolution during heap bioleaching
- 2008
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Ingår i: Biotechnology and Bioengineering. - : Wiley. - 0006-3592 .- 1097-0290. ; 99:4, s. 811-820
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Tidskriftsartikel (refereegranskat)abstract
- Silicate minerals are present in association with metal sulfides in ores and their dissolution occurs when the sulfide minerals are bioleached in heaps for metal recovery. It has previously been suggested that silicate mineral dissolution can affect mineral bioleaching by acid consumption, release of trace elements, and increasing the viscosity of the teach solution. In this study, the effect of silicates present in three separate samples in conjunction with chalcopyrite and a complex multi-metal sulfide ore on heap bioleaching was evaluated in column bioreactors. Fe2+ oxidation was inhibited in columns containing chalcopyrite samples A and C that leached 1.79 and 1.11 mM fluoride, respectively but not in sample B that contained 0.14 mM fluoride. Microbial Fe2+ oxidation inhibition experiments containing elevated fluoride concentrations and measurements of fluoride release from the chalcopyrite ores supported that inhibition of Fe2+ oxidation during column leaching of two of the chalcopyrite ores was due to fluoride toxicity. Column bioleaching of the complex sulfide ore was carried out at various temperatures (7-50 degrees C) and pH values (1.5-3.0). Column leaching at pH 1.5 and 2.0 resulted in increased acid consumption rates and silicate dissolution such that it became difficult to filter the leach solutions and for the leach liquor to percolate through the column. However, column temperature (at pH 2.5) only had a minor effect on the acid consumption and silicate dissolution rates. This study demonstrates the potential negative impact of silicate mineral dissolution on heap bioleaching by microbial inhibition and liquid flow.
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| 5. |
- Kaksonen, Anna H., et al.
(författare)
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Biological iron oxidation and sulfate reduction in the treatment of acid mine drainage at low temperatures
- 2008
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Ingår i: Psychrophiles. - Berlin : Springer. - 9783540743347 - 9783540743354 ; , s. 429-454
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Bokkapitel (refereegranskat)abstract
- Acid mine drainage (AMD) is the result of exposure of sulfidic seams to the oxidizing and leaching action of water—rain water, humidity, and groundwater— and is exacerbated by microorganisms that catalyze the solubilization of sulfide minerals by the regeneration of Fe3+ and oxidation of their dissolution products as the source of energy. Typical AMD has a low pH and a high sulfate and ferric iron concentration although other metals may also be present. The chemical composition of AMD varies with sulfide minerals associated with coal and metal mines. At low pH, ferric iron in AMD participates in the leaching action, as shown for pyrite (FeS2) and chalcopyrite (CuFeS2).
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| 6. |
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| 7. |
- Kupka, Daniel, et al.
(författare)
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Oxidation of elemental sulfur, tetrathionate and ferrous iron by the psychrotolerant Acidithiobacillus strain SS3.
- 2009
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Ingår i: Research in Microbiology. - : Elsevier BV. - 0923-2508 .- 1769-7123. ; 160:10, s. 767-774
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Tidskriftsartikel (refereegranskat)abstract
- Mesophilic iron and sulfur-oxidizing acidophiles are readily found in acid mine drainage sites and bioleaching operations, but relatively little is known about their activities at suboptimal temperatures and in cold environments. The purpose of this work was to characterize the oxidation of elemental sulfur (S(0)), tetrathionate (S4O6(2-)) and ferrous iron (Fe2+) by the psychrotolerant Acidithiobacillus strain SS3. The rates of elemental sulfur and tetrathionate oxidation had temperature optima of 20 degrees and 25 degrees C, respectively, determined using a temperature gradient incubator that involved narrow (1.1 degrees C) incremental increases from 5 degrees to 30 degrees C. Activation energies calculated from the Arrhenius plots were 61 and 89 kJ mol(-1) for tetrathionate and 110 kJ mol(-1) for S(0) oxidation. The oxidation of elemental sulfur produced sulfuric acid at 5 degrees C and decreased the pH to approximately 1. The low pH inhibited further oxidation of the substrate. In media with both S(0) and Fe2+, oxidation of elemental sulfur did not commence until all available ferrous iron was oxidized. These data on sequential oxidation of the two substrates are in keeping with upregulation and downregulation of several proteins previously noted in the literature. Ferric iron was reduced to Fe2+ in parallel with elemental sulfur oxidation, indicating the presence of a sulfur:ferric iron reductase system in this bacterium.
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