Oxidation of Contaminants by Iron
Nanoparticles in the Presence of Oxygen
Elemental iron (Fe0),
which is also referred to as zero-valent iron, has been used to reduce
halogenated solvents and other chemical contaminants that often are
present in groundwater. Zero-valent iron usually is used for
contaminant removal in the absence of oxygen, because oxygen competes
with the iron for reactive sites on the iron. While the
presence
of oxygen slows the rate of reductive reactions, we have found that the
reaction of oxygen and zero-valent iron also can result in contaminant
oxidation through a complex series of reactions, such as those depicted
below:
Figure 1: Oxidation of iron by oxygen and organic compounds (R) by
oxygen.
We are currently examining the potential for
using
ZVI nanoparticles to produce strong oxidants. We have found
that
when ZVI is exposed to oxygen it can be used to degrade many different
types of organic contaminants (Keenan and Sedlak 2008a).
However,
the reactions tend to be inefficient, and only a small fraction of the
ZVI is converted into oxidants. We have found two ways of
increasing the yield of oxidants: adding iron-complexing ligands
(Keenan and Sedlak, 2008b) and adding athe catalyst POM (Lee et al.
2008). We are currently exploring ways of employing these
findings in the development of a heterogeneous catalyst that can be
used in water treatment systems. We also are
studying the
effects of ZVI reactions on biological systems because ZVI might be
useful for disinfection of water and the reactions may provide insight
into damage to cells casued by exposure to fine particles.
Figure 2:
Effect of polyoxometalate on the formation of formaldehyde from the
oxidation of methanol.
For more information see:
- Keenan C.R. and Sedlak D.L. (2008b)
Ligand-enhanced oxidant generation by nanoparticulate zero-valent iron.
Environ. Sci.
Technol., in press. DOI:10.1021/es801438f
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The Fate of
Hormones in the Aquatic Environment
Use of Iron to Control Methylmercury Formation
in Wetland Sediments
Oxidation of
Contaminants by Iron Nanoparticles in the Presence of Oxygen
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