Iron surface functional groups

Adsorption of cations on iron oxides (Table 11.3) may be specific or non specific. With non specific adsorption, there is at least one water molecule between the adsorbing species and the surface functional group. Specific adsorption involves interaction with deprotonated surface hydroxyl groups to form mono- and bi-nuclear, inner sphere complexes, i.e. 

Iron oxides in the finely divided form have the power to promote (catalyse) a range of redox and photochemical reactions (Tab. 11.7). The preliminary step is the adsorption of the reacting species on the iron oxide. This may be followed either by direct reaction with the Fe surface atoms or surface functional groups or the surface may promote reaction between the adsorbed species and a solution species such as dissolved oxygen. 

Bargar, J. R., Brown, G. E. Jr, and Parks, G. A. 991b). Surface complexation of Pb(ll) at oxide water interfaces II. XAFS and bond valence determination of mononuclear Pb(II) sorption products and surface functional groups on iron oxides. Geochim. Cosmochim. Acta 61, 2639-52. 

The work performed to date with tricarbonyl(cyclohexadienyl)iron adducts of enzymes has established the principles that IR-based experiments can be used to study the reactivity and properties of enzyme surface functional groups, but there is much left to be done in this area. Electrospray MS results (see for example ref [97]) are needed to count the number of surface groups that have been derivatized, and establish whether the gradual increase in intensity of the signal from the adduct is a consequence of random derivatization of all the available surface lysines, and reflects a progressive order of kinetic reactivity of lysines in different... 

The oxide surface has structural and functional groups (sites) which interact with gaseous and soluble species and also with the surfaces of other oxides and bacterial cells. The number of available sites per unit mass of oxide depends upon the nature of the oxide and its specific surface area. The specific surface area influences the reactivity of the oxide particularly its dissolution and dehydroxylation behaviour, interaction with sorbents, phase transformations and also, thermodynamic stability. In addition, specific surface area and also porosity are crucial factors for determining the activity of iron oxide catalysts. 

Sulfide catalysts have been dispersed directly on the coal surface. Very high dispersion on the catalyst may allow direct interactions between the catalyst and solid coal. The first application of this approach utilized molten chloride as the starting material. Later, oil- and water-soluble iron precursors were impregnated or ion exchanged onto the coal surface through the interaction with oxygen functional groups (56 -60). 

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