Perez, JPH, Freeman, HM orcid.org/0000-0001-8242-9561, Brown, AP orcid.org/0000-0001-9692-2154 et al. (5 more authors) (2020) Direct Visualization of Arsenic Binding on Green Rust Sulfate. Environmental Science and Technology, 54 (6). pp. 3297-3305. ISSN 0013-936X
Abstract
“Green rust” (GR), a redox-active Fe(II)–Fe(III) layered double hydroxide, is a potential environmentally relevant mineral substrate for arsenic (As) sequestration in reduced, subsurface environments. GR phases have high As uptake capacities at circum-neutral pH conditions, but the exact interaction mechanism between the GR phases and As species is still poorly understood. Here, we documented the bonding and interaction mechanisms between GR sulfate and As species [As(III) and As(V)] under anoxic and circum-neutral pH conditions through scanning transmission electron microscopy (STEM) coupled with energy-dispersive X-ray (EDX) spectroscopy and combined it with synchrotron-based X-ray total scattering, pair distribution function (PDF) analysis, and As K-edge X-ray absorption spectroscopy (XAS). Our highly spatially resolved STEM–EDX data revealed that the preferred adsorption sites of both As(III) and As(V) are at GR crystal edges. Combining this data with differential PDF and XAS allowed us to conclude that As adsorption occurs primarily as bidentate binuclear (2C) inner-sphere surface complexes. In the As(III)-reacted GR sulfate, no secondary Fe–As phases were observed. However, authigenic parasymplesite (ferrous arsenate nanophase), exhibiting a threadlike morphology, formed in the As(V)-reacted GR sulfate and acts as an additional immobilization pathway for As(V) (∼87% of immobilized As). We demonstrate that only by combining high-resolution STEM imaging and EDX mapping with the bulk (differential) PDF and extended X-ray absorption fine structure (EXAFS) data can one truly determine the de facto As binding nature on GR surfaces. More importantly, these new insights into As–GR interaction mechanisms highlight the impact of GR phases on As sequestration in anoxic subsurface environments.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2020 American Chemical Society. This is an author produced version of an article published in Environmental Science and Technology. Uploaded in accordance with the publisher's self-archiving policy. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Chemical & Process Engineering (Leeds) The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Earth Surface Science Institute (ESSI) (Leeds) |
Funding Information: | Funder Grant number Royal Society of Chemistry Not Known |
Depositing User: | Symplectic Publications |
Date Deposited: | 25 Feb 2020 11:26 |
Last Modified: | 20 Feb 2021 01:38 |
Status: | Published |
Publisher: | American Chemical Society |
Identification Number: | 10.1021/acs.est.9b07092 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:157636 |