Specific Adsorption of Oxidants and Reductants

The binding of a reductant or oxidant species to form an inner-spheric surface complex changes its electronic structure and thus influences its reductive and oxidative reactivity. As a consequence the following differences in thermodynamic and kinetic properties between dissolved and adsorbed species may be observed (Wehrli et al., 1989). 

Schematic illustration on the specific adsorption on Fe-minerals of oxidants and reductants directly or through ligand bridges. The formation of these surface complexes (which is usually fast) facilitates the subsequent electron transfer. 

Inert M(III) cations will exchange their ligands faster once they are adsorbed to an oxide surface. 

The electron transfer from the ligand to the central metal ion (e.g., Mn(IV,III)I 

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