Linking Thermodynamics to Pollutant Reduction Kinetics by Fe2+ Bound to Iron Oxides

Sydney M. Stewart, Thomas B. Hofstetter, Prachi Joshi, Christopher A. Gorski

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51 Scopus citations


Numerous studies have reported that pollutant reduction rates by ferrous iron (Fe2+) are substantially enhanced in the presence of an iron (oxyhydr)oxide mineral. Developing a thermodynamic framework to explain this phenomenon has been historically difficult due to challenges in quantifying reduction potential (EH) values for oxide-bound Fe2+ species. Recently, our group demonstrated that EH values for hematite- and goethite-bound Fe2+ can be accurately calculated using Gibbs free energy of formation values. Here, we tested if calculated EH values for oxide-bound Fe2+ could be used to develop a free energy relationship capable of describing variations in reduction rate constants of substituted nitrobenzenes, a class of model pollutants that contain reducible aromatic nitro groups, using data collected here and compiled from the literature. All the data could be described by a single linear relationship between the logarithms of the surface-area-normalized rate constant (kSA) values and EH and pH values [log(kSA) = -EH/0.059 V - pH + 3.42]. This framework provides mechanistic insights into how the thermodynamic favorability of electron transfer from oxide-bound Fe2+ relates to redox reaction kinetics.

Original languageEnglish (US)
Pages (from-to)5600-5609
Number of pages10
JournalEnvironmental Science and Technology
Issue number10
StatePublished - May 15 2018

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • Environmental Chemistry


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