Iron reduction

Iron Reduction. The reduction of nitrophenols with iron filings or turnings takes place in weakly acidic solution or suspension (30). The aminophenol formed is converted to the water soluble sodium aminopheno1 ate by adding sodium hydroxide before the iron-iron oxide sludge is separated from the reaction mixture (31). Adjustment of the solution pH leads to the precipitation of aminophenols, a procedure performed in the absence of air because the salts are very susceptible to oxidation in aqueous solution. 

Insoluble red lakes are formed as by-products which decrease yields when 2-nitrophenol [88-75-5] is reduced with iron. Consequendy, the iron reduction of this nitro compound to 2-aminophenol is of minor industrial importance today. 

The industrial processes used for reduction are catalytic hydrogenation, iron reduction (aqueous neutral or acidic, or solvent), and sulfide reduction. 

Maintain a BW reserve of 0.75 to 1.25 ppm MEKO, using an iron reduction test. 

The quadrupole doublet has an isomer shift corresponding to iron in the ferric or Fe " state. After reduction in H2 at 675 K the catalyst consists mainly of metallic iron, as evidenced by the sextet, along with some unreduced iron, which gives rise to two doublet contributions of Fe " and Fe " in the centre. The overall degree of iron reduction, as reflected by the relative area under the bcc ion sextet, is high. Fischer-Tropsch synthesis at 575 K in CO and FI2 converts the metallic iron into the Flagg carbide, Fe5C2. The unreduced iron is mainly present as Fe ". Exposure of the carburized catalyst to the air at room temperature leaves most of the carbide phase unaltered but oxidizes the ferrous to ferric iron. 

DiChristina TJ (1992) Effects of nitrate and nitrite on dissimilatory iron reduction by Shewanella putrefaciens 200. J Bacteriol 174 1891-1896. 

Limestone Methanol Complexation Adsorption Bacterial sulfate and iron reduction Methane production... 

There is some evidence that the iron-sulfur protein, FhuF, participates in the mobilization of iron from hydroxamate siderophores in E. coli (Muller et ah, 1998 Hantke, K. unpublished observations). However, a reductase activity of FhuF has not been demonstrated. Many siderophore-iron reductases have been shown to be active in vitro and some have been purified. The characterization of these reductases has revealed them to be flavin reductases which obtain the electrons for flavin reduction from NAD(P)H, and whose main functions are in areas other than reduction of ferric iron (e.g. flavin reductase Fre, sulfite reductase). To date, no specialized siderophore-iron reductases have been identified. It has been suggested that the reduced flavins from flavin oxidoreductases are the electron donors for ferric iron reduction (Fontecave et ah, 1994). Recently it has been shown, after a fruitless search for a reducing enzyme, that reduction of Co3+ in cobalamin is achieved by reduced flavin. Also in this case it was suggested that cobalamins and corrinoids are reduced in vivo by flavins which may be generated by the flavin... 

Another possible route for reduction of the iron center is photoreduction. This has been studied in a variety of marine siderophore systems, such as aquachelin, marinobactin, and aerobactin (2), where it was demonstrated that photolytic reduction was due to a ligand-to-metal charge transfer band of the Fe(III)-siderophore complex, eventually resulting in reduction ofiron(III) and cleavage of the siderophore (31,154,155). This suggests a possible role for iron reduction in iron release (71,155). 

Okutman-Tas D, Pavlostathis SG (2007) The influence of iron reduction on the reductive biotransformation of pentachloronitrobenzene. Eur J Soil Biol 43 264—275... 

While the above discussion describes testing of aerobic microbial activity, the same scenario is applicable for anaerobic bioreactions. The primary difference is the analytical parameter. The uptake of carbon dioxide, nitrate degradation, sulfate reduction, or iron reduction may be monitored instead of oxygen utilization. 

Nealson, K. H., and C. R. Myers (1990), "Iron Reduction by Bacteria A Potential Role in the Genesis of Brandes Iron Formation", Amer. J. of Science 290, 35-45. 

Hansel CM, Benner SG, Neiss J, Dohnalkova A, Kukkadapu RK, Fendorf S (2003) Secondary mineralization pathways induced by dissimilatory iron reduction of ferrihydrite under advective flow. Geochim Cosmochim Acta 67 2977-2992... 

Nealson KH, Myers CR (1990) Iron reduction by bacteria a potential role in the genesis of banded iron formations. Amer Jour Sci 290A 35-45... 

Bell PE, Mills AL, Herman JS. 1987. Biogeochemical conditions favoring magnetite formation during anaerobic iron reduction. Appl Environ Microbiol 53 2610-16. 

Hanel JB. 2000. Thermophilic Iron Reduction. MS-thesis Univ. of Georgia, Athens, GA (US). 

Lovley DR, Beadecker M, Lonergan D, et al. 1989. Oxidation of aromatic contaminants coupled to microbial iron reduction. Nature 339 297-9. 

Tuccillo ME, Cozzarelli IM, Herman JS. 1999. Iron reduction in the sediments of a hydrocarbon-contaminated aquifer. Appl Geochem 14 655-67. 

A few examples of chemoautolithotrophic processes have been mentioned in this chapter, namely anaerobic methane oxidation coupled to sulfate reduction and the ones listed in Table 12.2 involving manganese, iron, and nitrogen. Another example are the microbial metabolisms that rely on sulfide oxidation. Since sulfide oxidation is a source of electrons, it is a likely source of energy that could be driving denitrification, and manganese and iron reduction where organic matter is scarce. 

Theoretical estimates of energy available from hydrothermal vent fluids for various chemosynthesis reactions used by vent microbes. Oxidative reactions are shown as dashed lines and reductive reactions as solid lines. Iron reduction provides too little energy to appear on plot. H2 oxidation was not calculated. Source From Leveille, R. J., and S. K. Juniper (2003). Biogeochemistry of Marine Systems, Blackwell Publications, pp. 238-292. 

Hydrogen oxidation Iron reduction H2 Organic acids N03- Fe - (oxyhydroxides) OO2 Organic acids Identified from molecular analyses Mesophilic bacteria and hyperthermophilic archaea... 

Iron reduction has been studied more intensively than manganese because of the greater abundance of iron in the natural enviromnent. However, because of their broadly similar chemistries, the processes involved are probably similar. 

Favre F, Tessier D, Abdehnoula M, Genin JM, Gates WP, Boivin P. 2002. Iron reduction and changes in cation exchange capacity in intermittently waterlogged soil. European... 

Ottow ICG. 1973. Bacterial mechanism of iron reduction and gley formation. In Schlicht-ing E, Schwertmann U, eds. Pseudogley and Gley. Weinheim International Soil Science Society, 29-35. 

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