TY - JOUR
T1 - Linking Thermodynamics to Pollutant Reduction Kinetics by Fe2+ Bound to Iron Oxides
AU - Stewart, Sydney M.
AU - Hofstetter, Thomas B.
AU - Joshi, Prachi
AU - Gorski, Christopher A.
N1 - Funding Information:
This work was supported by the U.S. National Science Foundation (Grant EAR-1451593 to C.A.G.) and by the Swiss National Science Foundation (Grant 200021_149283 to T.B.H.). We thank William Burgos for reviewing the manuscript prior to submission.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/5/15
Y1 - 2018/5/15
N2 - 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.
AB - 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.
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U2 - 10.1021/acs.est.8b00481
DO - 10.1021/acs.est.8b00481
M3 - Article
C2 - 29595255
AN - SCOPUS:85047302299
VL - 52
SP - 5600
EP - 5609
JO - Environmental Science & Technology
JF - Environmental Science & Technology
SN - 0013-936X
IS - 10
ER -