The oxidation of iron(II) with oxygen in NaCl brines

J. Michael Trapp, Frank J. Millero

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Abstract

The oxidation of nanomolar levels of iron(II) with oxygen has been studied in NaCl solutions as a function of temperature (0 to 50∈°C), ionic strength (0.7 to 5.6 mol·kg-1), pH (6 to 8) and concentration of added NaHCO3 (0 to 10 mmol·kg-1). The results have been fitted to the overall rate equation: d[Fe(II)]/dt = -kapp [Fe(II)][O2] The values of k app have been examined in terms of the Fe(II) complexes with OH- and CO 3 2- . The overall rate constants are given by: kappFe2+kFeFe(OH)+k Fe(OH)+ αFe(OH)2 kFe(OH)2+ αFe(CO3)2k Fe(CO3)2 where α i is the molar fraction and k i is the rate constant of species i. The individual rate constants for the species of Fe(II) interacting with OH - and CO 3 2- have been fitted by equations of the form: ln kFe2+ = 21.0+0.4I0.5 - 5562/T ln k FeOH = 17.1+1.5I0.5 - 2608/T ln kFe(OH)2 = -6.3-0.6I0.5+6211/T ln kFe(CO3)2 = 31.4+5.6 0.5-6698/T These individual rate constants can be used to estimate the rates of oxidation of Fe(II) over a large range of temperatures (0 to 50∈°C) in NaCl brines (I=0 to 6 mol·kg-1) with different levels of OH- and CO 3 2- .

Original languageEnglish (US)
Pages (from-to)1479-1493
Number of pages15
JournalJournal of Solution Chemistry
Volume36
Issue number11-12
DOIs
StatePublished - Dec 1 2007

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Keywords

  • Brines
  • Fe(II)
  • NaCl
  • Oxidation

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Physical and Theoretical Chemistry

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