Reduction of Fe(III)-oxide sorbents in suboxic and anoxic geochemical environments leads to release of Fe(II) and trace metal(loid)s to solution. The fate of these species is influenced by interactions with Al-bearing minerals in the soil matrix. We have shown that interactions of aqueous Fe(II) with aluminum-oxide at the near-neutral pH values typical of anoxic soil environments leads to rapid formation of Fe(II)-Al(III)-layered double hydroxides (Fe(II)-Al(III)-LDHs).1,2 The presence of aqueous arsenic may affect Fe(II) sorption onto Al-oxide, and, conversely, the formation of Fe(II)-Al(III)-LDH may impact the sorption of arsenic. Here, we conducted co-sorption studies of Fe(II) and arsenic species (As[III] and As[V]) in anoxic suspensions of γ-Al2O3 at pH 7.5 at various Fe(II) and As(III, V) concentrations, combining macroscopic kinetic experiments with synchrotron X-ray absorption spectroscopic (XAS) analyses. Our results show that Fe(II) and As(III) sorbed independently onto the γ-Al2O3 substrate, while Fe(II) and As(V) strongly interacted. The results demonstrate notable differences between single- and dual-sorbate systems as to the Fe(II) and As(V) sorption trends and mechanisms. The model systems assessed here improve our understanding of the geochemical fate of Fe(II) and As 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. 48, 4937-4945.

Co-sorption of Fe(II) with As(III) and As(V) at the solid-water interface of aluminum oxide

249th National Meeting (2015)

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