Magnetite formation

Erythorbic acid and sodium erythorbate are very safe products, widely used in the food industry as antioxidants and alternatives to vitamin C. In the water treatment industry, they are strong reducing agents that reduce metal oxides and hydroxides to their more soluble ferrous forms and promote the passivation of boiler waterside surfaces (magnetite formation). 

Karlin R, Lyle M, Heath CR (1987) Authigenic magnetite formation in suboxic marine sediments. Nature 326 490-493... 

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

Under otherwise similar conditions, low oxidation rates appear to promote magnetite and goethite, whereas high rates favor lepidocrocite. Magnetite formation probably requires slow oxidation because complete dehydroxylation of the precursor (green rust) prior to complete oxidation is only possible if sufficient time is available if, on the other hand, complete oxidation is fast and precedes dehydroxylation, lepidocrocite forms in preference to magnetite (Schwertmann Taylor, 1977). Dehydroxylation and oxidation appear to be competing reaction steps. 

The details of enzymatic magnetite formation in bacteria, especially the valence and chemical form in which the Fe enters the cell, are still not fully understood. At low oxygen concentrations in the bacterial habitats dissolved Fe may exist in bivalent form, but Fe added as a soluble Fe " complex, such as Fe " citrate (Schuler Bauerlein, 1996) can also function as an Fe source. Within the cell, part of the Fe will then form a highly reactive Fe "oxide, probably ferrihydrite, which in turn, reacts with the dissolved Fe to form magnetite (Mann et al. 1989) by a via-solution process (Fig. 17.6) ... 

Cooper, D.C. Picardal, F. Rivera, J. Talbot, C. (2000) Zinc immobilization and magnetite formation via ferric oxide reduction by She-wanella putrefadens. Environ. Sci. Techn. 34 100-106... 

Perez, O.P. Umetsu,Y. (2000) ORP monitored magnetite formation from aqueous solutions at low temperatures. Hydrometallurgy 55 35-56... 

The carbon content of both reactors were similar and showed a slight decrease in concentration from the top to the middle of the reactor. Both reactors show an equivalent increase in magnetite concentration through the reactor bed (Figure 6). The relative crystallite size, as well as B.E.T, surface area and pore volumes for the samples from both stage reactors are similar. It is thus apparent that the sulphur plays no part in the magnetite formation,... 

Hong Y. and Eegley B., Jr. (1998) Experimental studies of magnetite formation in the solar nebula. Meteorit. Planet. Sci. 33, 1101-1112. 

By employing separate furnaces for smelting and converting, the Mitsubishi process allows better control of oxygen potential, and, hence, of magnetite formation. Oxygen efficiency in the converting furnace is 85 to 90%. 

Chaudhuri, S. K., Lack, J. G., and Coates, J. D. (2001). Biogenic magnetite formation through anaerobic biooxidation of Fe(II). Appl. Environ. Microbiol. 61, 2844-2848. 

Matsunaga T, Sakaguchi T, Tadokoro F (1991) Magnetite formation by a magnetic bacterium capable of growing aerobically. Appl Microbiol Biotechnol 35 651-655... 

Sakaguchi T, Burgess IG, Matsunaga T (1993) Magnetite formation by a sulphate-reducing bacterium. Nature (Fondon) 365 47-49... 

Chaudhry GR, MacGregor CH (1983) Cytochrome b from Escherichia coli nitrate reductase. Its properties and association with the enzyme complex. J Biol Chem 258 5819-5827 Chaudhry GR, Suzuki I, Lees H (1980) Cytochrome oxidase of Nitrobacter agilis isolation by hydrophobic chromatography. Can J Microbiol 26 1270-1274 Chaudhuri SK, Lack JG, Coates JD (2001) Biogenic magnetite formation through anaerobic biooxidation of Fe(II). Appl Environ Microbiol 67 2844—2848 Cheeseman P, Toms-Wood A, Wolfe RS (1972) Isolation and properties of a fluorescent-compound, Factor 420, from Methanobacterium strain M.o.H. J Bacteriol 112 527-531... 

The system Ca0-Fe203 is binary only in the part rich in calcium oxide. The mixture rich in iron, even heated in air, easily lost the oxygen at higher temperatures with the magnetite formation, in which part of iron is reduced to Fe(ll). Obviously, the iron reduction is much quicker in reducing atmosphere and then in the clinker-ing process even metallic iron can be formed (see Sect. 2.3.2 and 9.2). 

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