Iron reducing environments

Sihcon irons are very resistant to oxidizing and reducing environments, and resistance depends on the formation of a passive film. These irons are widely used in siilfuric acid service, since they are unaffec ted by siilfuric at all strengths, even up to the boihng point. 

The high temperatures of coal char oxidation lead to a partial vaporization of the mineral or ash inclusions. Compounds of the alkali metals, the alkaline earth metals, silicon, and iron are volatilized during char combustion. The volatilization of silicon, magnesium, calcium, and iron can be greatly enhanced by reduction of their refractory oxides to more volatile forms (e.g., metal suboxides or elemental metals) in the locally reducing environment of the coal particle. The volatilized suboxides and elemental metals are then reoxidized in the boundary layer around the burning particle, where they subsequently nucleate to form a submicron aerosol. 

Reduction of monocyclic aromatic nitro compounds has been demonstrated (a) with reduced sulfur compounds mediated by a naphthoquinone or an iron porphyrin (Schwarzenbach et al. 1990), and (b) by Fe(II) and magnetite produced by the action of the anaerobic bacterium Geobacter metallireducens (Heijman et al. 1993). Quinone-mediated reduction of monocyclic aromatic nitro compounds by the supernatant monocyclic aromatic nitro compounds has been noted (Glaus et al. 1992), and these reactions may be signihcant in determining the fate of aromatic nitro compounds in reducing environments (Dunnivant et al. 1992). 

Heijman CG, C Holliger, M A Glaus, RP Schwarzenbach, J Zeyer (1993) Abiotic reduction of 4-chloronitro-benzene to 4-chloroaniline in a dissimilatory iron-reducing enrichment culture. Appl Environ Microbiol 59 4350-4353. 

Ganesh R, KG Robinson, GD Feed, GS Sayler (1997) Reduction of hexavalent uranium from organic complexes by sulfate- and iron-reducing bacteria. Appl Environ Microbiol 63 4385-4391. 

Lovley DR, DJ Lonergan (1990) Anaerobic oxidation of toluene, phenol, and -cresol by the dissimilatory iron-reducing organism, GS-15. Appl Environ Microbiol 56 1858-1864. 

Fleming EJ, EE Mack, PG Green, DC Nelson (2006) Mercury methylation from unexpected sources molybdate-inhibited freshwater sediments and an iron-reducing bacterium. Appl Environ Microbiol 72 457-464. 

Jahn MK, SB Haderlin, RU Meckenstock (2005) Anaerobic degradation of benzene, toluene, ethylbenzene, and o-xylene in sediment-free iron-reducing enrichment cultures. Appl Environ Microbiol 71 3355-3358. 

After calcinations, the precipitated iron catalyst is composed of a mixture of iron oxide phases before activation. The exact nature of this phase is not critical for the discussion and will be referred to in general as an oxide phase. During activation the catalyst is subjected to a reducing environment that will lead to the formation of either metallic iron if pure hydrogen is used or some iron carbide if the reduction is done with either CO or syngas. During reduction with a gas... 

Markwiese, J.T., J.S. Meyer, and PJ.S. Colberg. 1998. Copper tolerance in iron-reducing bacteria implications for copper mobilization in sediments. Environ. Toxicol. Chem. 17 675-678. 

The first consideration was the speciation and distribution of the metal in the sediment and water. Benthic organisms are exposed to surface water, pore water and sediment via the epidermis and/or the alimentary tract. Common binding sites for the metals in the sediment are iron and manganese oxides, clays, silica often with a coating of organic carbon that usually accounts for ca. 2% w/w. In a reducing environment contaminant metals will be precipitated as their sulfides. There is not necessarily a direct relationship between bioavailability and bioaccumulation, as digestion affects the availability and transport of the metals in animals, in ways that differ from those in plants. 

Lovley DR, Phillips EJP (1988) Novel mode of microbial energy metabolism organic carbon oxidation coupled to dissimilatory reduction of iron or manganese. App Environ Microbio 54 1472-1480 Lovley DR, Stolz JF, Nord Jr GL, Phillips EJP (1987) Anaerobic production of magnetite by a dissimilatoiy iron-reducing microorganism. Nature 330 252-254... 

F. (2000) Dissimilatory iron-reducing bacteria can influence the reduction of carbon tetrachloride by iron metal. Environ. Sd. Techn. 34 2461-2464... 

Fendorf S. (2001) Iron promoted reduction of chromate by dissimilatory iron-reducing bacteria. Environ. Sd. Techn. 35 522-527... 

Conditions that are conducive to the accumulation and decay of plant residues, and therefore conducive to the formation of coal, are typically associated with water-saturated and reducing environments. Consequently, a large portion of the trace elements associated with the mineral fraction of coal are expected to occur in reduced forms, primarily as sulphides or carbonates. However, because of its abundance compared to sulphur, it is unlikely that the complete reduction of iron oxides to iron sulphide would ever occur. Therefore, the presence of Fe oxides, and trace... 

Hofstetter, T. B., C. G. Heijman, C. Holliger, and R. P. Schwarzenbach, Complete reduction of TNT and other (poly)nitroaromatic compounds under iron-reducing subsurface conditions , Environ. Sci. Technol., 33, 1479-1487 (1999). 

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