Akaganeite formation

The log Kso value which is the only value available to date was found to be -3.04 + 0.05. The free energy of formation (-752.7 kj moC ) calculated from this Kso is very much lower than that of goethite which does not accord very well with the observed behaviour of the two oxides this suggests that the equation chosen by Biedermann and Chow to describe their reaction may not in fact apply to akaganeite. 

Bauer et ah, 1986). It is also a significant corrosion product of Fe alloy phases on Antarctic meteorites where its formation is induced by the chloride ions coming from airborne seaspray and/or volcanic activity (Buchwald and Clarke, 1989). In these meteorites, akaganeite is located adjacent to the corroding surface and beneath a layer of goethite/spinel into which it eventually transforms. 

One of these approaches is the formation of polysaccharide iron complexes (PIC), such as Niferex, a compound used in the treatment of iron deficiency anemia. PICs are formed by neutralization of FeCb-containing carbohydrate solutions with base. Mineral particles of roughly the same size as ferritin cores can be made. These contain iron in an octahedral enviromnent coordinated to oxygen. However, the long-range order of the polynuclear iron core is closer to that of akaganeite rather than ferrihydrite. ... 

Because of the similar thermodynamic stability of goethite and hematite, formation of hematite competes with nucleation of goethite which proceeds via dissolution of the ferrihydrite precursor. The lower the temperature, the more likely it is that goethite will form. Goethite nucleation can therefore be inhibited by preheating the oven and also all solutions before they are combined. The presence of chloride should be avoided because it promotes the formation of akaganeite (P-FeOOH). However, chloride concentrations below 0.02 M can be tolerated at temperatures of around 100 °C. 

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... 

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). 

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