Thiobacillus minerals

In the leaching process, bacteria such as Thiobacillus ferroxidans and those belonging to the Sulfolobus genera, play a major role in the oxidation reactions at moderate and higher temperatures respectively. The oxidation of sulfides by bacteria is typified by the reactions of pyrite, a common accessory mineral in primary copper ore bodies this reaction can be considered to proceed through two stages ... 

Oxidation of insoluble mineral sulfides to the usually water-soluble sulfates (PbS04 is an exception) can also be carried out in many cases by microbial leaching, that is, by the use of bacteria such as Thiobacillus fer-rooxidans which can use the sulfide-sulfate redox cycle to drive metabolic processes. The overall reaction still consumes oxygen... 

Bacteria may catalyze and considerably enhance the oxidation of pyrite and Fe(II) in water, especially under acidic conditions (Welch et al., 2000, 597). Many microbial species actually oxidize only specific elements in sulfides. With pyrite, Acidithiobacillus thiooxidans is important in the oxidation of sulfur, whereas Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans (formerly Thiobacillus fer-rooxidans) oxidize Fe(II) (Gleisner and Herbert, 2002, 140). Acidithiobacillus ferrooxidans obtain energy through Reaction 3.45 (Gleisner and Herbert, 2002, 140). The bacteria are most active at about 30 °C and pH 2-3 (Savage, Bird and Ashley, 2000, 407). Acidithiobacillus sp. and Leptospirillum ferrooxidans have the ability to increase the oxidation of sulfide minerals by about five orders of magnitude (Welch et al., 2000, 597). 

A variety of bacteria and other microorganisms, such as the archaeum Ferriplasma acidarmanus, may be actively involved in the oxidation of arsenopyrite (Gihring et al., 1999 Cruz et al., 2005 Barrett et al., 1993). Specifically, (Gihring et al., 1999) collected Thiobacillus caldus and Ferriplasma acidarmanus from acid mine drainage at Iron Mountain, California, USA. The mine drainage had a temperature of approximately 42 °C, a pH of 0.7, and contained about 50 mg L 1 of arsenic. T. caldus growths on the surfaces of arsenopyrite actually hindered the oxidation of the mineral, whereas F. acidarmanus was very tolerant of arsenic and accelerated the dissolution of arsenopyrite (Gihring et al., 1999). 

Some microorganisms can catalyze certain oxido-reduction reactions like the oxidation of iron and manganese in water, the oxidation of sulfur compounds, and oxidation-reduction of nitrogen compounds. Aerobic autotrophic bacteria of the type Thiobacillus can release soluble iron, copper, and sulfuric acid as sulphates into water. These organisms can be found everywhere in nature wherever an acidic environment is maintained in the presence of sulfide-containing minerals. 

SABA [Spherical Agglomeration-Bacterial Adsorption] A microbiological process for leaching iron pyrite from coal. The bacterium Thiobacillus ferrooxidans adsorbs on the surface of the pyrite crystals, oxidizing them with the formation of soluble ferrous sulfate. Developed by the Canadian Center for Mineral and Energy Technology, Ottawa. In 1990, the process had been developed only on the laboratory scale, using coal from eastern Canada. 

AMD is probably the most severe environmental problem that occurs on mine sites, It happens where mineral and coal deposits contain sulfide minerals, particularly pyrite (FeS2). When waste rock containing sulfides is exposed fo air, these minerals are oxidized, releasing sulfuric acid, The process is accelerated by bacteria such as Thiobacillus ferrooxidans that obtain energy from the oxidation reaction for their growth. The release of acid can cause the pH of... 

Edwards K. J., Bond P. L., and Banfield J. E. (2000a) Characteristics of attachment and growth of Thiobacillus caldus on sulphide minerals a chemotactic response to sulphur minerals Environ. Microbiol. 2, 324—332. 

Thiobacillus neapolitanus H2S, sulfide minerals, S(0), S2O3, S4O6... 

Many microorganisms form mineral acids (nitric and sulfuric) besides organic acids. Whenever sulfur is present, Thiobacillus spp. can oxidize the reduced sulfur compounds and produce sulfuric acid. In areas where intense nitrification is possible and where neutral or alkaline reactions occur, intense weathering by nitrifiers is also possible. 

Torma, A.E. and Legalt, G., 1973. Role de la surface des minerals sulfures lors de leur biodegradation par Thiobacillus ferrooxidans. Ann. Microbiol., 124A 111—121. 

Khalid, A.M. and Ralph, B.J., 1977. The Leaching behaviour of various zinc sulphide minerals with three Thiobacillus species. Conference Bacterial Leaching. GBF Monograph Series, No. 4 pp. 165—173. 

Tuovinen, O.H., Niemela, S.I. and Gyllenberg, H.G., 1971b. Effect of mineral nutrients and organic substances on the development of Thiobacillus ferrooxidans. Biotechnol. Bioeng., 13 517—527. 

Giudici-Orticoni MT, Leroy G, Nitschke W, Bmschi M (2000) Characterization of a new dihemic c(4)-type cytochrome isolated from Thiobacillus ferrooxidans. Biochem 39 7205-7211 Gustafsson JP (2001) The surface chemistry of imogolite. Clays Clay Minerals 49 73-80 Guthrie GD, Bish DL, Reynolds RC (1995) Modeling the X-ray diffraction pattern of opal-CT. Am Mineral 80 869-872... 

These reactions, in particular carbonate solvation, deplete the sulfuric acid content of the extraction solution. Later metal recovery from the solutions, however, returns an equivalent acid strength to the water. Also, Thiobacillus ferro-oxidans in the presence of air converts sulfide minerals to sulfates, which contributes to the acid content of the solvent when metal is recovered from the solution. 

The bacterium Thiobacillus ferrooxidans obtains its energy by means of reactions involving various minerals. As a result, it produces acid and an oxidizing solution of Fe ions, which can react with metals in crude ore. 

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