Reductive sorption of vanadium by iron monosulfide in seawater

Felicia J. Haase*, Colton J. Vessey, Ryo Sekine, Nicholas J.C. Doriean, David T. Welsh, Joseph A. Otte, Jessica Hamilton, Donald E. Canfield, Yun Wang, Enzo Lombi, William W. Bennett

*Corresponding author for this work

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Abstract

Vanadium (V) is a promising paleoredox tracer in ancient marine sediments due its range of possible oxidation states (+3 to +5) and its unique redox-sensitivity. However, the interactions between V and the sulfide minerals common under ancient depositional conditions remain poorly studied. Iron monosulfide (FeS) is the first sulfide phase to form in anoxic-sulfidic waters and sediments, and an important precursor for sedimentary pyrite. Here we investigate the adsorption of dissolved VV by freshly precipitated FeS under conditions relevant to marine waters. We report near complete removal of aqueous V (94–98%; ∼2 × 10−5 M) by FeS (1 g L−1) in anoxic seawater within 24 h. Synchrotron-based X-ray absorption spectroscopy (XAS) at the V and Fe K-edges shows that aqueous VV was rapidly (<60 s) reduced to solid-phase VIII during reductive sorption by FeS. Iron K-edge and X-ray diffraction data show that the products of the subsequent oxidation of VIII-bearing FeS were elemental sulfur and lepidocrocite. Solid-phase V was oxidized within 24 h from +2.97 to +4.0, with no loss of V to solution. EXAFS analysis suggests, based on the predominance of V┄Fe backscatters at ∼3.0 Å, that octahedral VIV may have been incorporated in the structure of lepidocrocite during its formation. These results provide valuable insight into the relationship of V and FeS in marine environments, including the adsorption mechanism and V speciation relevant to the fate of V during early diagenesis in marine sediments.

Original languageEnglish
Article number121983
JournalChemical Geology
Volume649
Number of pages15
ISSN0009-2541
DOIs
Publication statusPublished - 30. Mar 2024

Keywords

  • FeS
  • Incorporation
  • Lepidocrocite
  • Marine sediment
  • Paleoredox tracer
  • Vanadium

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