Microbial respiration of Fe(III)-oxides and hydroxides in suboxic and anoxic aqueous geochemical environments results in release of aqueous Fe(II) into solution. The geochemical fate of released Fe(II) is at least partially influenced by Fe(II) sorption with mineral substrates of the soil matrix. Our previous work has shown rapid formation of Fe(II)-Al(III) layered double hydroxides (Fe(II)-Al(III)-LDHs) and Fe(II)-phyllosilicate during aqueous Fe(II) sorption onto ?-Al2O3and clay at the near-neutral pH values typical of anoxic soil environments. ?1,2 Dissolved organic compounds, which are abundant in reducing soil environments like wetlands, may impact Fe(II) sorption behavior by interacting with Fe(II) in solution or at the surface of mineral substrates. Here, we used batch sorption studies combined with extended X-ray absorption spectroscopy to study the effect of humic acids (HA) and fulvic acids (FA) on Fe(II) sorption reactions with clay and aluminum oxide substrates at pH 7.5 under anoxic conditions over reaction times up to 3 months. We observed that the addition of organic compounds reduced the extent and rate of Fe(II) sorption onto the mineral substrates, with specific effects varying with substrate type and the type of organic material (HA or FA) added. The model systems assessed here will improve our understanding of the geochemical fate of Fe(II) in suboxic and anoxic aqueous geochemical environments.(1) Elzinga, E. J. Formation of layered Fe(II)�Al(III)-hydroxides during reaction of Fe(II) with aluminum oxide. 2012.   Environ. Sci. Technol. 46, 4894-4901.(2) Zhu, Y.; Elzinga, E. J. Formation of layered Fe(II)-hydroxides during Fe(II) sorption onto clay and metal-oxide substrates. 2014  . Environ. Sci. Technol. (In revision).

Effect of organic compounds on Fe(II) sorption onto clay and aluminum oxide minerals

248th National Meeting (2014)

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