1 research outputs found
Molecular Insights of Oxidation Process of Iron Nanoparticles: Spectroscopic, Magnetic, and Microscopic Evidence
Oxidation
behavior of nano-Fe<sup>0</sup> particles in an anoxic
environment was determined using different state-of-the-art analytical
approaches, including high resolution transmission electron microscopy
(HR-TEM) combined with energy filtered transmission electron microscopy
(EFTEM), X-ray absorption spectroscopy (XAS), and magnetic measurements.
Oxidation in controlled experiments was compared in standard double
distilled (DD) water, DD water spiked with trichloroethene (TCE),
and TCE contaminated site water. Using HR-TEM and EFTEM, we observed
a surface oxide layer (ā¼3 nm) formed immediately after the
particles were exposed to water. XAS analysis followed the dynamic
change in total metallic iron concentration and iron oxide concentration
for the experimental duration of 35 days. The metallic iron concentration
in nano-Fe<sup>0</sup> particles exposed to water, was ā¼40%
after 35 days; in contrast, the samples containing TCE were reduced
to ā¼15% and even to nil in the case of TCE contaminated site
water, suggesting that the contaminants enhance the oxidation of nano-Fe<sup>0</sup>. Frequency dependence measurements confirmed the formation
of superparamagnetic particles in the system. Overall, our results
suggest that nano-Fe<sup>0</sup> oxidized via the Fe<sup>0</sup> ā
FeĀ(OH)<sub>2</sub> ā Fe<sub>3</sub>O<sub>4</sub> ā (Ī³-Fe<sub>2</sub>O<sub>3</sub>) route and the formation of superparamagnetic
maghemite nanoparticles due to disruption of the surface oxide layer