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Thermodynamic Characterization of Iron Oxide-Aqueous Fe(2+) Redox Couples.
Gorski, Christopher A; Edwards, Rebecca; Sander, Michael; Hofstetter, Thomas B; Stewart, Sydney M.
Afiliación
  • Gorski CA; Department of Civil & Environmental Engineering, Pennsylvania State University , 212 Sackett Building, University Park, Pennsylvania 16802, United States.
  • Edwards R; Department of Civil & Environmental Engineering, Pennsylvania State University , 212 Sackett Building, University Park, Pennsylvania 16802, United States.
  • Sander M; Institute of Biogeochemistry and Pollutant Dynamics (IBP), Swiss Federal Institute of Technology, ETH Zürich , 8092 Zürich, Switzerland.
  • Hofstetter TB; Institute of Biogeochemistry and Pollutant Dynamics (IBP), Swiss Federal Institute of Technology, ETH Zürich , 8092 Zürich, Switzerland.
  • Stewart SM; Eawag, Swiss Federal Institute of Aquatic Science and Technology , CH-8600 Dübendorf, Switzerland.
Environ Sci Technol ; 50(16): 8538-47, 2016 08 16.
Article en En | MEDLINE | ID: mdl-27427506
Iron is present in virtually all terrestrial and aquatic environments, where it participates in redox reactions with surrounding metals, organic compounds, contaminants, and microorganisms. The rates and extent of these redox reactions strongly depend on the speciation of the Fe2+ and Fe3+ phases, although the underlying reasons remain unclear. In particular, numerous studies have observed that Fe2+ associated with iron oxide surfaces (i.e., oxide-associated Fe2+) often reduces oxidized contaminants much faster than aqueous Fe2+ alone. Here, we tested two hypotheses related to this observation by determining if solutions containing two commonly studied iron oxides­hematite and goethite­and aqueous Fe2+ reached thermodynamic equilibrium over the course of a day. We measured reduction potential (EH) values in solutions containing these oxides at different pH values and aqueous Fe2+ concentrations using mediated potentiometry. This analysis yielded standard reduction potential (EH0) values of 768 ± 1 mV for the aqueous Fe2+­goethite redox couple and 769 ± 2 mV for the aqueous Fe2+­hematite redox couple. These values were in excellent agreement with those calculated from existing thermodynamic data, and the data could be explained by the presence of an iron oxide lowering EH values of aqueous Fe3+/Fe2+ redox couples.
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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Compuestos Férricos / Hierro Idioma: En Revista: Environ Sci Technol Año: 2016 Tipo del documento: Article País de afiliación: Estados Unidos Pais de publicación: Estados Unidos
Texto completo
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Imprimir
XML
PubMed Links
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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Compuestos Férricos / Hierro Idioma: En Revista: Environ Sci Technol Año: 2016 Tipo del documento: Article País de afiliación: Estados Unidos Pais de publicación: Estados Unidos