Double-layer, mixed valence iron hydroxide minerals [FeII(1-x)FeIIIx(OH)2]x+ [x/nAn-.m/nH2O]x-, known as “green rusts” (GRs), have been investigated for their ability to intercalate anionic species (A) for application in diverse fields ranging from drug delivery to water treatment. Furthermore, GR is hypothesized to have played a role in the prebiotic chemistry during the Archean, the earliest period in Earth’s history. The implication of GR in the prebiotic metabolism of early Earth may have led to the synthesis of organic material while simultaneously acting as an accretionary agent priming conditions for abiogenesis. One research gap in GR chemistry lies with the controlled, strictly anaerobic synthesis of GR samples for subsequent comparison of chemical reactivity. Our research objectives are to investigate GR reactivity and structure as a function of various intercalated anions, with a focus on the reduction of nitrogen-containing species. A range of GR samples were synthesized with rigorously controlled pH and redox potentials, while under strict anaerobic conditions, leading to well-defined Fe2+/Fe3+ ratios, and avoiding over-oxidation and the formation of undesirable by-products common to other methods. The samples were characterized by X-ray powder diffraction (XRD) and infrared spectroscopy. The various forms of GR were found to possess significant differences in stability and reactivity, notably towards the reduction of nitrate/nitrite mixtures. Preliminary reduction product characterization and reaction rate determination were carried out. The results are discussed with a focus on prebiotic metabolism.

Green revolution: Reactive iron-containing minerals and prebiotic metabolism

251st National Meeting (2016)

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