Iron oxyhydroxide FeOOH

Shah Singh, S. Kodama, H. (1994) Effect of the presence of aluminum ions in iron solutions on the formation of iron oxyhydroxides (FeOOH) at room temperature under acidic environment. Clays Clay Min. 42 606—613... 

Guo, X., Du, Y Chen, F. el al. (2007a) Mechanism of removal of arsenic by bead cellulose loaded with iron oxyhydroxide (f -FeOOH) EXAFS study. Journal of Colloid and Interface Science, 314(2), 427-33. 

Fig. 8 Molecular orbital depiction of the concept of band-gap energies with corresponding molecular orbital transitions for the Fe(III) oxyhydroxides. The photon action spectra [134,230] for photochemical reactions [136,141,143] of the iron oxyhydroxides (i.e., a-Fe2C>3, a-FeOOH, /S-FeOOH and y-FeOOH) indicate that the most effective electron transition leading to photocatalysis or photoreduction is the O2- to Fe3+ transition shown schematically above...

This approach successfully described the experimental results of several adsorption studies with various metal ions and oxide substrates ( 2). In addition, one can make predictive calculations of metal ion uptake, if the surface parameters of an oxide/elec-trolyte can be estimated. For example. Figure 4 shows predicted and experimental adsorption behavior of Cd(II) on amorphous iron oxyhydroxide. Surface stability constants for Cd(II) were estimated ( ) from an experimental study of Cd(II) uptake by a-FeOOH (21, %). 

The highest residual traces of Cr(VI) occur in the anodic sections of the experimental cells. Cr(VI) removal from aqueous solutions is enhanced by the presence of ferric iron oxyhydroxide phases, as Cr(VI) adsorbs onto FeOOH (e.g. Aoki and Munemori, 1982 Mesuere and Fish, 1992a,b Mukhopadhyay, Sundquist, and Schmitz, 2007). The amount of released by anodic electrode dissolution primarily depends on the applied current and the duration of the passage of the current through the electrodes (e.g. Mukhopadhyay, Sundquist, and Schmitz, 2007). Differences in the lateral extent of iron mineralization in the three experiments illustrate that the buffering capacity of the soils influenced the spatial extents of the zone of Cr(VI) reduction and complementary alkaline zone. The Warwick soil (experiment A) operated at half the applied voltage to experiments B and C, experienced the furthest advance of iron mineralization from the anode array, quickly developed a sharp pH jump, and attained the most acidic conditions. Collectively, these attributes indicate that the Warwick soil had a comparatively low buffering capacity relative to the other two soils examined. 

Pyrite crystals that oxidize in an environment with a near-neutral pH and with enough alkalinity to neutralize the acid produced by the oxidation reaction typically become replaced by a mixture of iron oxyhydroxide minerals, mostly goe-thite (FeOOH). This mixture is sometimes referred to as limonite . 

Kim J, Nielsen U, Grey C (2008) Local environments and lithium adsorption on the iron oxyhydroxides lepidocrocite (gamma-FeOOH) and goethite (alpha-FeOOH) A H-2 and Li-7 solid-state MAS NMR study. J Am Chem Soc 13CK4) 1285-1295... 

Membranes can act as both active and passive templates for the formation of well-defined nanostructures in a number of ways. In the biological realm, they have a limited role in the formation of nanowires, where virus capsids are much more effective, as described elsewhere in this volume (see Viruses as Self-Assembled Templates, Self-Processes). An interesting exception that takes place close to the membranes of living cells is the formation of iron oxyhydroxide (akaganeite, /1-FeOOH) in a natural ecosystem, in which polysaccharides are shown to be important as they are contained in the filaments of the inorganic material. It is believed that the sugar is extruded from the cell and then acts as a template to promote the formation of the mineral. On the other hand, entirely synthetic lipids can be used for the preparation of pipes of organically functionalized layered materials—clays —in... 

Pyrrhotite (FeSi+ c) is ferrimagnetic and a common accessory mineral in rocks and a representative of iron sulphides. Representatives of iron oxyhydroxides are goethite a-FeOOH and lepidocrocite y-FeOOH. 

A number of other iron oxyhydroxide phases exist for iron(III), although there are limited, if any, thermodynamic data for these phases. Lemire et al. (2013) do list an enthalpy of formation for akaganeite, -FeOOH(s). 

In the anoxic zone, heterotrophic respiration of particulate Mn02 and Fc203 or FeOOH causes manganese and iron to be reduced to Mn (aq) and Fe (aq). As dissolved ions, these trace metals diffuse through the pore waters. The ions that diffuse upwards will reenter the oxic zone, where they react with O2 to reform the oxyhydroxides. This produces a metal-enriched layer that lies just above the redox... 

De Endredy, A.S. (1963) Estimation of free iron oxides in soils and clays by a photolytic method. Clay Min. Bull. 5 209-217 de Faria, D.L.A. Venancio Silva, S. de Oliveira, M.T. (1997) Raman Microspectroscopy of some iron oxides and oxyhydroxides. J. Raman Spectrosc. 28 873-878 De Grave, E. Vandenberghe, R.E. (1986) 57Fe Mossbauer effect study of well-crystallized goethite (a-FeOOH) Hyp. Interact. 28 643-646... 

Laberty and Navrotsky (1998) determined the enthalpies of formation of a number of iron oxide and oxyhydroxide polymorphs. Data are listed in Table 2 which also compares the enthalpy relations among aluminum, iron, and manganese. It is evident that the Fe oxyhydroxide phases are much less stable relative to the anhydrous ferric phase (hematite) than are the aluminum oxyhydroxides relative to corundum. This is consistent with the much more frequent observation of hematite than of corundum in the field. It is also evident that the iron phases are as rich in polymorphism as the aluminum phases. It is clear that the enthalpy differences for both anhydrous (AI2O3, Fe203, Mn02) and hydrous (AlOOH, FeOOH, MnOOH) polymorphs are small, setting the stage for nanoscale stability crossovers. 

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