A recent publication (http://dx.doi.org/10.1016/j.gca.2013.11.044) from the Gadgil Lab uncovers how bivalent cations and oxyanions control the structure of Fe(III) precipitates generated from Fe(II) oxidation. The authors found that the presence of co-existing bivalent cations (Ca2+, Mg2+) and oxyanions (P, As(V), Si) during Fe(II) oxidation and Fe(III) polymerization changes the Fe(III) phase from a “pseudo” lepidocrocite (γ-FeOOH) with low sheet-stacking coherence to a nanoscale oxyanion-rich Fe(III) polymer. The results from this research have application across multiple disciplines ranging from low-cost drinking water treatment to the transport and fate of contaminants and nutrients in natural and engineered systems. This is one of the first studies to reveal the intermediate-ranged structure of nanocrystalline, oxyanion-rich Fe(III) polymers, the structures of which continue to be debated in the environmental geochemistry literature.
Structure of Fe(III) precipitates generated by the electrolytic dissolution of Fe(0) in the presence of groundwater ions. Case M. van Genuchten, Jasquelin Peña, Susan E. Amrose, Ashok J. Gadgil (2014). Geochimica et Cosmochimica Acta.
The full article can be found at this link