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Title: Reactivity of redox cycled Fe-bearing subsurface sediments towards hexavalent chromium reduction

Abstract

Structural Fe(II) in clay minerals and natural sediments is known to reduce Cr(VI) to Cr(III), but the effect of redox-cycled Fe-bearing natural sediments on Cr(VI) reduction kinetics is poorly understood. The objective of this study was to understand the kinetics and mechanisms of Cr(VI) reduction by Fe(II) in redox cycled natural sediment. Fe-bearing sediment was collected from the Ringold formation in the 300 area of Hanford, Washington, United States. Fe redox cycling of the sediment was accomplished via four cycles of bioreduction of structural Fe(III) in Hanford sediment and air oxidation of the resulting Fe(II). Bio-produced Fe(II) in Hanford sediment from each redox cycle was utilized to reduce Cr(VI) at three temperatures (10, 20 and 30 °C). The initial rate of Cr(VI) reduction generally increased with each redox cycle, which was more pronounced at high temperatures. The amount of Fe(II) oxidized to the amount of Cr(VI) reduced was close to the expected stoichiometric ratio of 3. Aqueous concentrations of Si, Al, and Fe revealed some dissolution of the sediment after reaction with Cr(VI). X-ray diffraction (XRD) and scanning electron microscopy (SEM) detected secondary mineral formation. Mössbauer data showed that the oxidation of Fe(II) was coupled with the reduction of Cr(VI)more » but no Fe-oxides/oxyhydroxides formed. Transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), XANES, and EXAFS were performed for representative reduced Cr solids that formed from reduction of Cr(VI) by sediment-associated Fe(II) at 30 °C. TEM revealed that the d-spacing of Cr-reacted montmorillonite at 30 °C, a dominant Fe-bearing mineral in Hanford sediment, expanded from 10 Å to 13 Å. This layer expansion was likely due to intercalation of reduced Cr(III) into the interlayer space of the montmorillonite structure. EELS exhibited an L2 absorption peak at 586.0 eV and an L3 absorption peak at 577.0 eV, suggestive of Cr(III) in a hydroxide mineral phase. Similarly, XANES and EXAFS analyses confirmed Cr(VI) reduction to Cr(OH) 3 at 30 °C and indicated an edge-sharing coordination of the Cr(III) octahedra to 2–3 other Cr or metal ions. Furthermore, this study has important implications for understanding the reactivity of clay-rich sediment towards Cr(VI) reduction at contaminated sites and the stability of the reduced Cr(III).« less

Authors:
 [1];  [2];  [1];  [3];  [4];  [4]; ORCiD logo [5];  [6];  [7]
  1. Miami Univ., Oxford, OH (United States)
  2. Miami Univ., Oxford, OH (United States); China Univ. of Geosciences, Beijing (China)
  3. Miami Univ., Oxford, OH (United States); Univ. of Alaska Anchorage, Anchorage, AK (United States)
  4. Univ. of Illinois at Urbana-Champaign, Champaign, IL (United States)
  5. Bulgarian Academy of Sciences, Sofia (Bulgaria); Argonne National Lab. (ANL), Argonne, IL (United States)
  6. Argonne National Lab. (ANL), Argonne, IL (United States)
  7. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23). Subsurface Biogeochemical Research; USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1526037
Grant/Contract Number:  
AC02-06CH11357
Resource Type:
Accepted Manuscript
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 252; Journal Issue: C; Journal ID: ISSN 0016-7037
Publisher:
The Geochemical Society; The Meteoritical Society
Country of Publication:
United States
Language:
English
Subject:
Fe-redox cycle; Hanford sediment; bioreduction G. sulfurreducens; chromium immobilization; kinetic study

Citation Formats

Bishop, Michael E., Dong, Hailiang, Glasser, Paul, Briggs, Brandon R., Pentrak, Martin, Stucki, Joseph W., Boyanov, Maxim I., Kemner, Kenneth M., and Kovarik, Libor. Reactivity of redox cycled Fe-bearing subsurface sediments towards hexavalent chromium reduction. United States: N. p., 2019. Web. doi:10.1016/j.gca.2019.02.039.
Bishop, Michael E., Dong, Hailiang, Glasser, Paul, Briggs, Brandon R., Pentrak, Martin, Stucki, Joseph W., Boyanov, Maxim I., Kemner, Kenneth M., & Kovarik, Libor. Reactivity of redox cycled Fe-bearing subsurface sediments towards hexavalent chromium reduction. United States. doi:10.1016/j.gca.2019.02.039.
Bishop, Michael E., Dong, Hailiang, Glasser, Paul, Briggs, Brandon R., Pentrak, Martin, Stucki, Joseph W., Boyanov, Maxim I., Kemner, Kenneth M., and Kovarik, Libor. Wed . "Reactivity of redox cycled Fe-bearing subsurface sediments towards hexavalent chromium reduction". United States. doi:10.1016/j.gca.2019.02.039.
@article{osti_1526037,
title = {Reactivity of redox cycled Fe-bearing subsurface sediments towards hexavalent chromium reduction},
author = {Bishop, Michael E. and Dong, Hailiang and Glasser, Paul and Briggs, Brandon R. and Pentrak, Martin and Stucki, Joseph W. and Boyanov, Maxim I. and Kemner, Kenneth M. and Kovarik, Libor},
abstractNote = {Structural Fe(II) in clay minerals and natural sediments is known to reduce Cr(VI) to Cr(III), but the effect of redox-cycled Fe-bearing natural sediments on Cr(VI) reduction kinetics is poorly understood. The objective of this study was to understand the kinetics and mechanisms of Cr(VI) reduction by Fe(II) in redox cycled natural sediment. Fe-bearing sediment was collected from the Ringold formation in the 300 area of Hanford, Washington, United States. Fe redox cycling of the sediment was accomplished via four cycles of bioreduction of structural Fe(III) in Hanford sediment and air oxidation of the resulting Fe(II). Bio-produced Fe(II) in Hanford sediment from each redox cycle was utilized to reduce Cr(VI) at three temperatures (10, 20 and 30 °C). The initial rate of Cr(VI) reduction generally increased with each redox cycle, which was more pronounced at high temperatures. The amount of Fe(II) oxidized to the amount of Cr(VI) reduced was close to the expected stoichiometric ratio of 3. Aqueous concentrations of Si, Al, and Fe revealed some dissolution of the sediment after reaction with Cr(VI). X-ray diffraction (XRD) and scanning electron microscopy (SEM) detected secondary mineral formation. Mössbauer data showed that the oxidation of Fe(II) was coupled with the reduction of Cr(VI) but no Fe-oxides/oxyhydroxides formed. Transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), XANES, and EXAFS were performed for representative reduced Cr solids that formed from reduction of Cr(VI) by sediment-associated Fe(II) at 30 °C. TEM revealed that the d-spacing of Cr-reacted montmorillonite at 30 °C, a dominant Fe-bearing mineral in Hanford sediment, expanded from 10 Å to 13 Å. This layer expansion was likely due to intercalation of reduced Cr(III) into the interlayer space of the montmorillonite structure. EELS exhibited an L2 absorption peak at 586.0 eV and an L3 absorption peak at 577.0 eV, suggestive of Cr(III) in a hydroxide mineral phase. Similarly, XANES and EXAFS analyses confirmed Cr(VI) reduction to Cr(OH)3 at 30 °C and indicated an edge-sharing coordination of the Cr(III) octahedra to 2–3 other Cr or metal ions. Furthermore, this study has important implications for understanding the reactivity of clay-rich sediment towards Cr(VI) reduction at contaminated sites and the stability of the reduced Cr(III).},
doi = {10.1016/j.gca.2019.02.039},
journal = {Geochimica et Cosmochimica Acta},
number = C,
volume = 252,
place = {United States},
year = {2019},
month = {3}
}

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