Individual iron oxides

This section considers aspects and examples of the dissolution behaviour of individual iron oxides. Additional data are listed in Table 12.3 for a range of experimental conditions. As yet, characteristic dissolution rates carmot be assigned to the various iron oxides (Blesa Maroto, 1986). There are, however, some consistent differences between oxides with considerable stability differences, hence a comparison of the oxides is included here. In addition, the reactivity of any particular oxide may vary from sample to sample, depending on its source (natural or synthetic) and the conditions under which it formed. To illustrate this. Table 12.4 summarizes conditions and results from dissolution experiments in which a range of samples of the same oxide was compared. How the properties of the sample influence its dissolution behaviour is still not fully understood. A thorough characterization of the samples by solid state analysis, e. g. by EXAFS, to provide a basis for understanding the dissolution behaviour is, therefore, desirable. 

Oxide Substitution No. of samples Surface area m g Dissolving medium TfC) Model Reaction rate Activation energy (kj mot ) Author 

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Table 1. Parameters of 57Fe Mossbauer spectra recorded form the Fe2O3-In2O3 composites and individual iron oxides annealed at 300 °C.

Other research groups reported the modification of the surfaces of iron oxides by hydrophilic macromolecules such as PVA and proteins. In this work, Lee et al. carried out a coprecipitation of iron salts in an aqueous solution of PVA to form a stabilized dispersion. They reported a decreasing crystallinity of iron oxide particles accompanying the increase of the concentrations of PVA, while the morphology and particles size remained unchanged. Other studied materials to encapsulate individual iron oxide nanoparticles or small clusters via polymerization methods involved natural polymers - or albumins. ... 

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