Rates and mechanism of Fe(II) oxidation at nanomolar total iron concentrations

D. W. King, H. A. Lounsbury, Frank J Millero

Research output: Contribution to journalArticle

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Abstract

A fully automated luminol-based chemiluminescence system has been developed for rapid analysis of Fe(II) at natural levels. Using this system, the rates of Fe(II) oxidation in 0.7 M NaCl have been measured for nanomolar concentrations of Fe(II) over the pH range 7.0-8.3. When the production and decomposition of H2O2 in the system were considered, measured rates at these levels were in excellent agreement with a model based on previously reported rate constants determined using micromolar levels of Fe(II). These results show that O2 - and OH+ intermediates produced as a result of Fe(II) oxidation remain effective as Fe(II) oxidants in these controlled conditions. The chemical model for Fe(II) oxidation also allows prediction of steady- state H2O2 and O2 - concentrations that result from the oxidation of micromolar levels of Fe(II). The concentration of both species increases exponentialty with increasing pH. At pH 8.2, the predicted H2O2 and O2 - concentrations are 220 and 2.3 nM, respectively. The predicted H2O2 concentrations are in excellent agreement with laboratory measurements. These results suggest that significant concentrations of H2O2 and O2 - should be present at the oxic-anoxic interface of marine environments where micromolar levels of Fe(II) are in contact with dissolved oxygen.

Original languageEnglish (US)
Pages (from-to)818-824
Number of pages7
JournalEnvironmental Science and Technology
Volume29
Issue number3
DOIs
StatePublished - 1995

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Iron
oxidation
iron
Oxidation
Luminol
Chemiluminescence
Dissolved oxygen
Oxidants
oxidant
marine environment
Rate constants
dissolved oxygen
decomposition
Decomposition
rate
prediction

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Science(all)
  • Environmental Chemistry
  • Earth and Planetary Sciences(all)

Cite this

Rates and mechanism of Fe(II) oxidation at nanomolar total iron concentrations. / King, D. W.; Lounsbury, H. A.; Millero, Frank J.

In: Environmental Science and Technology, Vol. 29, No. 3, 1995, p. 818-824.

Research output: Contribution to journalArticle

King, D. W. ; Lounsbury, H. A. ; Millero, Frank J. / Rates and mechanism of Fe(II) oxidation at nanomolar total iron concentrations. In: Environmental Science and Technology. 1995 ; Vol. 29, No. 3. pp. 818-824.
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