During the last few decades, significant advances have been made in understanding the reaction of Fe(II) with Fe(III) oxyhydroxides. Recent data, however, suggests that Fe(II)-catalyzed recrystallization of goethite might be a one and done process. Here we investigate whether exposure to Fe(II) inhibits Fe(II)-goethite electron transfer and whether this inhibition is reversible. We used a series of sequential isotope experiments in combination with <sup>57</sup>Fe Mossbauer spectroscopy and wet chemical extractions. Our results revealed that exposure to Fe(II) inhibits electron transfer and with longer Fe(II) exposure times less electron transfer occurs. X-ray absorption and magnetic circular dichroism spectroscopy (XAS/XMCD) suggest that reaction with Fe(II) decreases the dichroism at the surface of goethite which may indicate that maturing or annealing of the new goethite layer makes it less susceptible to electron transfer. Interestingly though, when the layer of sorbed Fe(II) is removed by a buffer or acid wash or by air oxidation, electron transfer is mostly restored, indicating that transient geochemical fluctuations may restore Fe(II)-goethite electron transfer.

Fe(II) inhibits Fe(II)-goethite electron transfer

2019 Spring National Meeting

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