Solution silicates can polymerize on iron oxide and affect the phase stability and morphology of iron oxides in aquatic systems.  Silicate polymerization on goethite with varying crystal morphology was studied using XPS. The Si 2s BE peak shifts to higher value with increasing surface silicate concentrations (GSi), indicating a higher degree silicate polymerization.  At low GSi the Si 2s BE was higher on goethite with smaller particle size indicating disordered surfaces promote silicate oligomerization compared to the predominantly 110 faces of the larger acicular needles. In contrast at high GSi the Si 2s BE was higher on the acicular needles, reflecting the preferred formation of 3 dimensional silicate polymers on 021 faces. This reasoning was supported by considering the geometric constraints of silicate polymerization and the arrangement of FeO6 octahedra on goethite 110 and 021 faces.  It suggests crystal structure and morphology influence silicate polymerization on goethite and vice versa.

Silicate polymerization on goethite differing in morphology: An X-ray photoelectron spectroscopy investigation

244th National Meeting (2012)

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