Environmental Engineering Reference
In-Depth Information
water. For example, it has been reported that surface area normalized rate constants (
k
SA
)
from experiments with bimetallic Pd/Fe nanoparticles are typically 1-2 orders of
magnitude larger than those for nanoscale and microscale iron under similar conditions
(Lien and Zhang, 2001). The nanoparticle technology is considered well suited for
in-situ treatment of contaminant hot-spots given its high reactivity, portability, and
flexible deployment in the field (Elliott and Zhang, 2001; Zhang, 2003). In addition, the
focus is also on bimetallic microparticles as they may provide insights into the
development of advanced bimetallic nanomaterials.
Table 7.2
Application of zero-valent metals for treatments of various contaminants.
Process &
Metal Type
Pollutants
Reactions
References
Reduction:
ZVI, Aluminum,
Bimetals, Iron
Nanoparticles
Chlorinated
organic solvents
Nitrate
Heavy metals
(e.g., Cr
6+
, Cu
2+
)
Perchlorate
CCl
4
+ 2e
-
+H
+
CHCl
3
+ Cl
-
Matheson and
Tratnyek, 1994; Lien
and Zhang, 1999;
Lien 2005; Alowitz,
and Scherer, 2002;
Cheng et al., 1997;
Cao and Zhang,
2006; Moore et al.,
2003; Li and Zhang,
2007
→
NO
3
+ 8e
-
+ 7 H
2
O
NH
4
+
+ 10 OH
→
Cu
2+
+ 2e
-
Cu
0
→
ClO
4
-
+ 8H
+
+ 8e
-
Cl
-
+ 4H
2
O
→
Oxidation:
Sulfated
Aluminum, Iron
Nanoparticles,
ZVI
MTBE
Herbicides
As
3+
1. Reductive oxidation of dioxygen
2. Fenton's reaction
3. Others
Lien and Wilkin,
2002; Su and Puls,
2004; Joo et al.,
2005; Kanel et al.,
2005
Immobilization:
ZVI, Iron
Nanoparticles
Heavy metals
(e.g., Cr
3+
, As
3+
,
As
5+
)
1. Adsorption
2. Precipitation
3. Co-precipitation
Ponder et al., 2000;
Lien and Wilkin,
2005; Li and Zhang,
2007; Lien et al.,
2007
7.2
Micro-Sized Bimetallic Particles
The build-up of iron corrosion products at the iron surface declining its reactivity
toward contaminants and the increase in solution pH during the iron-mediated reaction
are the two major issues affecting the application of ZVI technology. This is because the
iron-mediated reaction involves iron corrosion that inevitably leads to increase in
solution pH and the formation of iron hydroxide precipitates:
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