The oxidation of Fe(II) in NaCl-HCO3 - and seawater solutions in the presence of phthalate and salicylate ions

A kinetic model

J. Magdalena Santana-Casiano, Melchor González-Dávila, Frank J Millero

Research output: Contribution to journalArticle

63 Citations (Scopus)

Abstract

The oxidation of Fe(II) by molecular oxygen in NaCl-HCO3 - and natural seawater solutions and in the presence of phthalic and salicylic acid has been studied at different pHF and Fe(II)-organic compounds ratios. These two compounds have been selected as simple organic model compounds in order to describe the effect of organic ligands on the oxidation rates of Fe(II) in the environment. A kinetic model including the speciation of Fe(II) and the organic species interacting with the major ions in solution was developed to describe the oxidation rate in any media. The model successfully describes Fe(II) behavior in both NaCl-bicarbonate solutions and seawater in the absence and in the presence of the selected compounds. The second-order rate constants for oxidation of the different species by oxygen are the same for all the experimental conditions studied; the speciation of the species accounts for the differences observed for each selected media. The Fe(OH)2 species is the most significant contributor to the overall oxidation rate in 0.002 m NaHCO3 solution, concentration found in natural seawater. Phthalate ion decreases the Fe(II) oxidation rate in the selected media, while salicylate ion increases oxidation as a result of the formation of the Fe(II)-salicylate complex. The oxidation rate for the Fe(II)-phthalate is close to zero accounting for the lower rate than in pure Fe(II) solution. Salicylate ion forms a 1:1 complex with an oxidation rate kL = 6.62 105 ± 300 M-1 min -1. The higher rate is probably related to the formation of a stable Fe(III)-salicylate complex.

Original languageEnglish (US)
Pages (from-to)27-40
Number of pages14
JournalMarine Chemistry
Volume85
Issue number1-2
StatePublished - Feb 2004

Fingerprint

salicylate
Salicylates
phthalate
Seawater
Ions
seawater
oxidation
kinetics
Oxidation
Kinetics
ion
rate
phthalic acid
oxygen
salicylic acid
Molecular oxygen
Bicarbonates
Organic compounds
bicarbonate
ligand

Keywords

  • Fe(II)
  • Kinetic model
  • Oxidation
  • Phthalic acid
  • Salicylic acid
  • Speciation

ASJC Scopus subject areas

  • Chemistry(all)
  • Oceanography

Cite this

The oxidation of Fe(II) in NaCl-HCO3 - and seawater solutions in the presence of phthalate and salicylate ions : A kinetic model. / Santana-Casiano, J. Magdalena; González-Dávila, Melchor; Millero, Frank J.

In: Marine Chemistry, Vol. 85, No. 1-2, 02.2004, p. 27-40.

Research output: Contribution to journalArticle

Santana-Casiano, JM, González-Dávila, M & Millero, FJ 2004, 'The oxidation of Fe(II) in NaCl-HCO3 - and seawater solutions in the presence of phthalate and salicylate ions: A kinetic model', Marine Chemistry, vol. 85, no. 1-2, pp. 27-40.
Santana-Casiano, J. Magdalena ; González-Dávila, Melchor ; Millero, Frank J. / The oxidation of Fe(II) in NaCl-HCO3 - and seawater solutions in the presence of phthalate and salicylate ions : A kinetic model. In: Marine Chemistry. 2004 ; Vol. 85, No. 1-2. pp. 27-40.
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