Semiconductor-electrochemical aspects of bacterial leaching. I. Oxidation of metal sulphides with large energy gaps

Tributsch, H.; Bennett, J. C.

doi:10.1002/jctb.280310176

Cited by 68 publications

(13 citation statements)

References 21 publications

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“…This conclusion can be deduced directly from the relationship between the solubility product of the sulphide and the estimated bacterial activity (Figure 1). If semiconductors with an excess of holes (CU~S, CuS) are excluded from these considerations, the experimental data fit to a dependence, which can approximately be described as: log CB= -a log Kso (1) in which CB is the estimated bacterial concentration and KSO is the solubility product of the sulphide which is defined as:…”

Section: Discussionmentioning

confidence: 99%

Semiconductor-electrochemical aspects of bacterial leaching. Part 2. Survey of rate-controlling sulphide properties

Tributsch¹,

Bennett²

1981

J. Chem. Technol. Biotechnol.

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Sixteen metal sulphides with widely differing solid state, chemical and electrochemical properties have been investigated with respect to their suitabilityasanenergy source for Thiobucillus ferrooxiduns. The most critical rate-determining parameter for bacterial oxidation (in the absence of any electron acceptors, e.g. Fe3+) was the solubility product of the sulphide. Deviations from the systematic dependence are, however, observed when a large concentration of the holes are present in the semiconducting sulphide (p-type conduction), or when holes are generated through electron extraction from the sulphide surface (e.g. by Fe3+). The experimental results are consistent with a mechanism in which Th. ferrooxiduns utilises H+ and Fe3+ as catalytic agents which break surface bonds by chemical and electrochemical mechanisms, respectively. They are subsequently recycled while the bacterium oxidises the generated surface products, -SHS-and SO, etc., to sulphate. On the basis of the derived mechanism it should be possible to estimate and predict the suitability of sulphides for bacterial oxidation and to analyse the influence of crystalline quality and impurities, as well as the composition of the solution, on the rate of oxidation.

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Section: Discussionmentioning

confidence: 99%

Semiconductor-electrochemical aspects of bacterial leaching. Part 2. Survey of rate-controlling sulphide properties

Tributsch¹,

Bennett²

1981

J. Chem. Technol. Biotechnol.

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“…The oxidation products in the case of FeS 2 and MoS 2 con-sisted of up to 90% sulfate and about 1 to 2% polythionates. Because the valence bands of FeS 2 and MoS 2 are derived only from the metal orbitals, the valence bands do not contribute to the chemical bond between the metal and the sulfur moiety in the crystal (2,25). Consequently, these metal sulfides are degradable only by an oxidizing attack, e.g., by iron(III) ions.…”

mentioning

confidence: 99%

“…Consequently, these metal sulfides are degradable only by an oxidizing attack, e.g., by iron(III) ions. None of these compounds is soluble in acid (proton attack) (21,25,26). Furthermore, both metal sulfides consist of pairs of sulfur atoms.…”

mentioning

confidence: 99%

Bacterial Leaching of Metal Sulfides Proceeds by Two Indirect Mechanisms via Thiosulfate or via Polysulfides and Sulfur

Schippers

Sand

1999

Appl Environ Microbiol

678

239

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The acid-insoluble metal sulfides FeS2, MoS2, and WS2 are chemically attacked by iron(III) hexahydrate ions, generating thiosulfate, which is oxidized to sulfuric acid. Other metal sulfides are attacked by iron(III) ions and by protons, resulting in the formation of elemental sulfur via intermediary polysulfides. Sulfur is biooxidized to sulfuric acid. This explains leaching of metal sulfides by Thiobacillus thiooxidans.

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“…The acidophilic, iron(II) ion-oxidizing bacteria Thiobacillus ferrooxidans and Leptospirillum ferrooxidans are the most important mesophiles for the extraction of metals from sulfidic ores by bioleaching (13,27). Little is known about the interfacial processes leading to the degradation of metal sulfides (26), because of a complex interaction of electrochemical, biochemical, and surface-specific mechanisms (25,33). Extracellular polymeric substances (EPS) mediate the contact between the bacterial cell and the sulfidic energy source, having a pivotal role in organic film formation and bacterium-substratum interactions (28).…”

mentioning

confidence: 99%

Importance of Extracellular Polymeric Substances fromThiobacillus ferrooxidansfor Bioleaching

Gehrke

Telegdi

Thierry

et al. 1998

Appl Environ Microbiol

401

132

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Leaching bacteria such as Thiobacillus ferrooxidansattach to pyrite or sulfur by means of extracellular polymeric substances (EPS) (lipopolysaccharides). The primary attachment to pyrite at pH 2 is mediated by exopolymer-complexed iron(III) ions in an electrochemical interaction with the negatively charged pyrite surface. EPS from sulfur cells possess increased hydrophobic properties and do not attach to pyrite, indicating adaptability to the substrate or substratum.

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Semiconductor-electrochemical aspects of bacterial leaching. I. Oxidation of metal sulphides with large energy gaps

Cited by 68 publications

References 21 publications

Semiconductor-electrochemical aspects of bacterial leaching. Part 2. Survey of rate-controlling sulphide properties

Semiconductor-electrochemical aspects of bacterial leaching. Part 2. Survey of rate-controlling sulphide properties

Bacterial Leaching of Metal Sulfides Proceeds by Two Indirect Mechanisms via Thiosulfate or via Polysulfides and Sulfur

Importance of Extracellular Polymeric Substances fromThiobacillus ferrooxidansfor Bioleaching

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