Magnetite FejO

Pit mouth A membrane of magnetite (FejO ) and rust (FeOOH) is formed, which prevents the intermingling of the acid anolyte and alkaline catholyte, by the following steps ... 

Few comparative studies have been made on the reductive dissolution of different mineral phases. In one such study, the order of reaction with seven organic and transition metal reductants was found to be the same hematite (a-Fe203)>magnetite (FejO,/,)>nickel ferrite (NiFe204) (43). Magnetite is an interesting case, since both Fe(III) and Fe(II) are present in the lattice prior to reaction. Evidence indicates that Fe(IIl) sites reduced to Fe(II) sites by redox reaction dissolve more quickly than Fe(II) sites originally present in the mineral lattice (6). 

Stewart, C. (1985) Spectral and other physicochemical properties of submicron powders of hematite (a-Fe203), maghemite (y-Fe203), magnetite (FejO ), goethite (a-FeOOH), and lepidocrocite (y-FeOOH). J. Geophys. Res., 90, 3126-44. 

Iron is extracted from ores hematite (FcjOj), magnetite (FejO, limonite... 

Recent advances in polyaniline (PANI) composites with oxides of transition metals such as titanium dioxide (TiO ), vanadium pentoxide (V Oj), chromium(III) oxide Crfif, manganese dioxide (MnO ), ferrous oxide (FeO), ferric oxide (Fe Oj), magnetite (FejO ), cobalt(II,III) oxide (Co O ), nickel oxide (NiO), cuprous oxide (CUjO), cupric oxide (CuO), zinc oxide (ZnO), yttrium oxide zirconium... 

Table 9.12 The Sonogashira coupling reactions catalyzed by nanoparticles of paramagnetic magnetite FejO [29c].

The crushed ore on a horizontal band conveyor passes a magnetic drum. Nonmagnetic gangue minerals fall vertically, but magnetic minerals such as magnetite, FejO,, follow the drum longer and fall into a separate container. 

M9 Magnetite FejO or rather, to separate divalent from trivalent iron,... 

The most significant observation concerns the comparison of the XRD spectra for the samples prepared by conventional way and in SC-CO (FP-6 and FPSK-5) and heated at 250°C, and the models shown in Figure 8 (c). We may conclude from Figure 8(a)-(c) that the only crystalline phase presents in the samples if that of magnetite FejO and there is an excellent match between the experimental data and FejO model. 

In nature most metals have a greater tendency to exist in ores than as neutral metals. Therefore, when metals are mined they are already in oxidized states. To be useful in industry, they must be reduced to the neutral metals. Iron, for example, is most commonly foimd in the minerals hmonite (FeO), hematite (Fe Oj), magnetite (FejO ), or in iron ores mixed with other metals. With hmonite, metallic iron is produced in a blast furnace by reacting FeO with carbon monoxide (CO) at elevated temperatures, as shown ... 

Figure 4.15 illustrates the E-pH diagram for iron at 25°C in the presence of water or humid environments. This diagram was calculated by considering all possible reactions associated with iron in wet or aqueous conditions listed in Table 4.13, excluding therefore drier forms of corrosion products such as magnetite (FejO ) or iron (ferric) oxide (Fe Oj). The various stability regions for these drier corrosion products are shown in Fig. 4.16 where the predominant compounds and ions are also indicated. 

The effect of oxygen and pH on the corrosion rate of steel at two temperatures is shown in Fig. 8.7 [11]. In a broad range of about pH 5 to 9, the corrosion rate can be expressed simply in terms of the amount of DO present (e.g., micrometer per year per milliliter DO per liter of water). At about pH 4.5, acid corrosion is initiated, overwhelming the corrosion rate by DO. At about pH 9.5 and above, deposition of insoluble ferric hydroxide, FelOHlj, or magnetite, FejO, tends to slow down the corrosion attack. Amphoteric metals such as aluminum, zinc, and lead, are however additionally sensitive to high pH situations and show a corrosion rate increase in alkaline enviromnents. Figure 8.8 compares the behavior of steel and aluminum as a function of pH. 

The lUPAC definition for a functional polymer is a polymer that bears specified chemical groups or polymer that has specified physical, chemical, biological, pharmacological, or other uses which depend on specific chemical groups [3]. The functional polymers are of two basic types intrinsically and extrinsically functional polymer. Intrinsically functional polymers are where the polymers themselves offer a unique range of properties for different applications, while extrinsically functional polymers are those composite materials containing dispersed fine particles of a functional material, such as magnetite (FejO ), carbon black in a conventional polymer. 

In the specific case of iron or steel exposed to dry or humid air, a very thin oxide film composed of an inner layer of magnetite (FejO ) forms, covered by an outer layer of FeOOH (rust). " Atmospheric corrosion rates for iron are relatively high and exceed those of other structural metals. They range (in pm/ year) from 4 to 65 in rural, 26 to 104 in marine, 23 to 71 in urban and 26 to 175 in industrial areas. ... 

Table 11.26 Data for the solubility constant of magnetite, FejO fs) (FeO-FejOjfs)) (reaction (11.15)).

Hemingway, B.S. (1990) Thermodynamic properties for bunsenite, NiO, magnetite, FejO, and hematite, FejOj, with comments on selected oxygen buffer reactions. Am. Mineral., 75, 781—790. 

---