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Title: Adsorption and Reduction of Arsenate during the Fe 2+ -Induced Transformation of Ferrihydrite

Abstract

Iron (oxyhydr)oxides play an important role in controlling the mobility and toxicity of arsenic (As) in contaminated soils and groundwaters. Dynamic changes in subsurface geochemical conditions can impact As sequestration and remobilization since the fate of As is highly dependent on the dominant iron mineral phases present and, specifically, the pathways through which these form or transform. To assess the fate of arsenate [As(V)] in subsurface settings, we have investigated the Fe 2+-induced transformation of As(V)-bearing ferrihydrite (As(V)-FH) to more crystalline phases under environmentally relevant anoxic subsurface conditions. Specifically, we examined the influence of varying Fe 2+ (aq)/Fe(III) solid ratios (0.5, 1, 2) on the behavior and speciation of mineral-bound As species during the transformation of As(V)-FH to crystalline iron-bearing phases at circumneutral pH conditions. At all Fe 2+ (aq)/Fe(III) solid ratios, goethite (GT), green rust sulfate (GR SO4), and lepidocrocite (LP) formed within the first 2 h of reaction. At low ratios (0.5 to 1), initially formed GR SO4 and/or LP dissolved as the reaction progressed, and only GT and some unreacted FH remained after 24 h. At Fe 2+ (aq)/Fe(III) solid ratio of 2, GR SO4 remained stable throughout the 24 h of reaction, alongside GT and unreactedmore » As(V)-FH. Despite the fact that majority of the starting As(V)-FH transformed to other phases, the initially adsorbed As was not released into solution during the transformation reactions, and ~99.9% of it remained mineral-bound. Nevertheless, the initial As(V) became partially reduced to As(III), most likely because of the surface-associated Fe 2+-GT redox couple. The extent of As(V) reduction increased from ~34% to ~40%, as the Fe 2+ (aq)/Fe(III) solid ratio increased from 0.5 to 2. Overall, our results provide important insights into transformation pathways of iron (oxyhydr)oxide minerals in As contaminated, anoxic soils and sediments and demonstrate the impact that such transformations can have on As mobility and also importantly oxidation state and, hence, toxicity in these environments.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3];  [4];  [5]; ORCiD logo [6];  [7]
  1. GFZ German Research Center for Geosciences, Telegrafenberg, 14473 Potsdam, Germany, Department of Earth Sciences, Free University of Berlin, 12249 Berlin, Germany
  2. Nano-Science Center, Department of Chemistry, University of Copenhagen, 2100 Copenhagen, Denmark
  3. Institute of Applied Geosciences, Karlsruhe Institute of Technology, 76137 Karlsruhe, Germany
  4. GFZ German Research Center for Geosciences, Telegrafenberg, 14473 Potsdam, Germany, School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom
  5. Nano-Science Center, Department of Chemistry, University of Copenhagen, 2100 Copenhagen, Denmark, Geological Survey of Denmark and Greenland (GEUS), 1350 Copenhagen K, Denmark
  6. Federal Institute for Materials Research and Testing (BAM), 12205 Berlin, Germany
  7. GFZ German Research Center for Geosciences, Telegrafenberg, 14473 Potsdam, Germany, Department of Earth Sciences, Free University of Berlin, 12249 Berlin, Germany, School of Earth and Environment, University of Leeds, Leeds LS2 9JT, United Kingdom
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); European Commission (EC)
OSTI Identifier:
1543341
Alternate Identifier(s):
OSTI ID: 1545881
Grant/Contract Number:  
AC02-06CH11357; 675219
Resource Type:
Journal Article: Published Article
Journal Name:
ACS Earth and Space Chemistry
Additional Journal Information:
Journal Name: ACS Earth and Space Chemistry Journal Volume: 3 Journal Issue: 6; Journal ID: ISSN 2472-3452
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; arsenic; ferrihydrite; goethite; green rust; mineral transformation; XAS; XPS

Citation Formats

Perez, Jeffrey Paulo H., Tobler, Dominique J., Thomas, Andrew N., Freeman, Helen M., Dideriksen, Knud, Radnik, Jörg, and Benning, Liane G. Adsorption and Reduction of Arsenate during the Fe 2+ -Induced Transformation of Ferrihydrite. United States: N. p., 2019. Web. doi:10.1021/acsearthspacechem.9b00031.
Perez, Jeffrey Paulo H., Tobler, Dominique J., Thomas, Andrew N., Freeman, Helen M., Dideriksen, Knud, Radnik, Jörg, & Benning, Liane G. Adsorption and Reduction of Arsenate during the Fe 2+ -Induced Transformation of Ferrihydrite. United States. doi:10.1021/acsearthspacechem.9b00031.
Perez, Jeffrey Paulo H., Tobler, Dominique J., Thomas, Andrew N., Freeman, Helen M., Dideriksen, Knud, Radnik, Jörg, and Benning, Liane G. Thu . "Adsorption and Reduction of Arsenate during the Fe 2+ -Induced Transformation of Ferrihydrite". United States. doi:10.1021/acsearthspacechem.9b00031.
@article{osti_1543341,
title = {Adsorption and Reduction of Arsenate during the Fe 2+ -Induced Transformation of Ferrihydrite},
author = {Perez, Jeffrey Paulo H. and Tobler, Dominique J. and Thomas, Andrew N. and Freeman, Helen M. and Dideriksen, Knud and Radnik, Jörg and Benning, Liane G.},
abstractNote = {Iron (oxyhydr)oxides play an important role in controlling the mobility and toxicity of arsenic (As) in contaminated soils and groundwaters. Dynamic changes in subsurface geochemical conditions can impact As sequestration and remobilization since the fate of As is highly dependent on the dominant iron mineral phases present and, specifically, the pathways through which these form or transform. To assess the fate of arsenate [As(V)] in subsurface settings, we have investigated the Fe2+-induced transformation of As(V)-bearing ferrihydrite (As(V)-FH) to more crystalline phases under environmentally relevant anoxic subsurface conditions. Specifically, we examined the influence of varying Fe2+(aq)/Fe(III)solid ratios (0.5, 1, 2) on the behavior and speciation of mineral-bound As species during the transformation of As(V)-FH to crystalline iron-bearing phases at circumneutral pH conditions. At all Fe2+(aq)/Fe(III)solid ratios, goethite (GT), green rust sulfate (GRSO4), and lepidocrocite (LP) formed within the first 2 h of reaction. At low ratios (0.5 to 1), initially formed GRSO4 and/or LP dissolved as the reaction progressed, and only GT and some unreacted FH remained after 24 h. At Fe2+(aq)/Fe(III)solid ratio of 2, GRSO4 remained stable throughout the 24 h of reaction, alongside GT and unreacted As(V)-FH. Despite the fact that majority of the starting As(V)-FH transformed to other phases, the initially adsorbed As was not released into solution during the transformation reactions, and ~99.9% of it remained mineral-bound. Nevertheless, the initial As(V) became partially reduced to As(III), most likely because of the surface-associated Fe2+-GT redox couple. The extent of As(V) reduction increased from ~34% to ~40%, as the Fe2+(aq)/Fe(III)solid ratio increased from 0.5 to 2. Overall, our results provide important insights into transformation pathways of iron (oxyhydr)oxide minerals in As contaminated, anoxic soils and sediments and demonstrate the impact that such transformations can have on As mobility and also importantly oxidation state and, hence, toxicity in these environments.},
doi = {10.1021/acsearthspacechem.9b00031},
journal = {ACS Earth and Space Chemistry},
issn = {2472-3452},
number = 6,
volume = 3,
place = {United States},
year = {2019},
month = {4}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1021/acsearthspacechem.9b00031

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Cited by: 8 works
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