posted on 2013-01-15, 00:00authored byChristopher
J. Miller, Andrew L. Rose, T. David Waite
The Fenton reaction, the oxidation of ferrous iron by
hydrogen
peroxide (H2O2), is typically assumed to be
a source of hydroxyl radical (HO•) in natural systems,
however, formation of HO• in this process is strongly
dependent upon solution pH and the ligand environment, with HO• only formed when Fe(II) is organically complexed.
In this study we examine the formation of HO• when
Fe(II)–NOM complexes are oxidized by H2O2 using phthalhydrazide as a probe for HO•. We demonstrate
that HO• formation can be quantitatively described
using a kinetic model that assumes HO• formation
occurs solely from the reaction of Fe(II)–NOM complexes with
H2O2, even though this reaction is sufficiently
slow to play only a negligible role in the overall oxidation rate
of total Fe(II). As such, NOM is seen to play a dual role in circumneutral
natural systems in stabilizing Fe(II) toward oxidation by H2O2 while enabling the formation of HO• through this oxidation process.