Antimonite Complexation with Thiol and Carboxyl/Phenol Groups of Peat Organic Matter

doi:10.1021/acs.est.9b00495

Title: Antimonite Complexation with Thiol and Carboxyl/Phenol Groups of Peat Organic Matter

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Abstract

Peatlands and other wetlands with abundant natural organic matter (NOM) are important sinks for antimony (Sb). While formation of Sb(III) sulfide phases or Sb(III) binding to NOM are discussed to decrease Sb mobility, the exact binding mechanisms remain elusive. Here, we reacted increasing sulfide concentrations with purified model peat at pH 6, forming reduced organic sulfur species, and subsequently equilibrated the reaction products with 50 μM of antimonite under anoxic conditions. Sulfur solid-phase speciation and the local binding environment of Sb were analyzed using X-ray absorption spectroscopy. We found that 85% of antimonite was sorbed by untreated peat. Sulfide-reacted peat increased sorption to 98%. Shell-by-shell fitting of Sb K-edge X-ray absorption fine structure spectra revealed Sb in untreated peat bound to carboxyl or phenol groups with average Sb–carbon distances of ~2.90 Å. With increasing content of reduced organic sulfur, Sb was progressively coordinated to S atoms at distances of ~2.45 Å and Sb–carbon distances of ~3.33 Å, suggesting increasing Sb–thiol binding. Iterative target factor analysis allowed exclusion of reduced inorganic Sb–sulfur phases with similar Sb–sulfur distances. In conclusion, even when free sulfide concentrations are too low for formation of Sb–sulfur precipitates, peat NOM can sequester Sb in anoxic, sulfur-enriched environments.

Authors:

Besold, Johannes ^[1]; Kumar, Naresh ^[2];

^[3]; Pacheco, Juan Lezama ^[4];

^[4];

^[1]

Bayreuth Univ., Bayreuth (Germany)
Stanford Univ., Stanford, CA (United States); Univ. of Vienna, Vienna (Austria)
Institute of Resource Ecology, Dresden (Germany)
Stanford Univ., Stanford, CA (United States)

Publication Date:: 2019-04-11

Research Org.:: SLAC National Accelerator Lab., Menlo Park, CA (United States)

Sponsoring Org.:: USDOE

OSTI Identifier:: 1529259

Grant/Contract Number:: AC02-76SF00515; DAAD 57315737; DAAD 57314604; PL 302/20-1

Resource Type:: Accepted Manuscript

Journal Name:: Environmental Science and Technology

Additional Journal Information:: Journal Volume: 53; Journal Issue: 9; Journal ID: ISSN 0013-936X

Publisher:: American Chemical Society (ACS)

Country of Publication:: United States

Language:: English

Citation Formats


                    Besold, Johannes, Kumar, Naresh, Scheinost, Andreas C., Pacheco, Juan Lezama, Fendorf, Scott, and Planer-Friedrich, Britta. Antimonite Complexation with Thiol and Carboxyl/Phenol Groups of Peat Organic Matter.  United States: N. p., 2019. 
        Web.  doi:10.1021/acs.est.9b00495.

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                    Besold, Johannes, Kumar, Naresh, Scheinost, Andreas C., Pacheco, Juan Lezama, Fendorf, Scott, & Planer-Friedrich, Britta. Antimonite Complexation with Thiol and Carboxyl/Phenol Groups of Peat Organic Matter.  United States.  doi:10.1021/acs.est.9b00495.

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                    Besold, Johannes, Kumar, Naresh, Scheinost, Andreas C., Pacheco, Juan Lezama, Fendorf, Scott, and Planer-Friedrich, Britta. Thu .  
        "Antimonite Complexation with Thiol and Carboxyl/Phenol Groups of Peat Organic Matter".  United States.  doi:10.1021/acs.est.9b00495.  https://www.osti.gov/servlets/purl/1529259.

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@article{osti_1529259,

  title        = {Antimonite Complexation with Thiol and Carboxyl/Phenol Groups of Peat Organic Matter},

  author       = {Besold, Johannes and Kumar, Naresh and Scheinost, Andreas C. and Pacheco, Juan Lezama and Fendorf, Scott and Planer-Friedrich, Britta},

  abstractNote = {Peatlands and other wetlands with abundant natural organic matter (NOM) are important sinks for antimony (Sb). While formation of Sb(III) sulfide phases or Sb(III) binding to NOM are discussed to decrease Sb mobility, the exact binding mechanisms remain elusive. Here, we reacted increasing sulfide concentrations with purified model peat at pH 6, forming reduced organic sulfur species, and subsequently equilibrated the reaction products with 50 μM of antimonite under anoxic conditions. Sulfur solid-phase speciation and the local binding environment of Sb were analyzed using X-ray absorption spectroscopy. We found that 85% of antimonite was sorbed by untreated peat. Sulfide-reacted peat increased sorption to 98%. Shell-by-shell fitting of Sb K-edge X-ray absorption fine structure spectra revealed Sb in untreated peat bound to carboxyl or phenol groups with average Sb–carbon distances of ~2.90 Å. With increasing content of reduced organic sulfur, Sb was progressively coordinated to S atoms at distances of ~2.45 Å and Sb–carbon distances of ~3.33 Å, suggesting increasing Sb–thiol binding. Iterative target factor analysis allowed exclusion of reduced inorganic Sb–sulfur phases with similar Sb–sulfur distances. In conclusion, even when free sulfide concentrations are too low for formation of Sb–sulfur precipitates, peat NOM can sequester Sb in anoxic, sulfur-enriched environments.},

  doi          = {10.1021/acs.est.9b00495},

  journal      = {Environmental Science and Technology},

  number       = 9,

  volume       = 53,

  place        = {United States},

  year         = {2019},

  month        = {4}

}

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DOI: 10.1021/acs.est.9b00495

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