Biomedical Engineering Reference
In-Depth Information
7.4.1 Remediation Nanotechnologies
7.4.1.1 Nanoscale Zero-Valent Iron
Nanoscale zero-valent iron (nZVI) has been widely used for environmen-
tal remediation due to its low cost. Its application in packed bed reactors
and permeable reactive barriers has been widely reported in the literature.
The material has been established as an effective reducing agent for a wide
variety of environmental contaminants [24]. A tentative list of these contami-
nants is given in Table 7.1.
The nZVI particles can remain reactive in soil and water for long periods
(>4-8 weeks) [24]. They react rapidly, when applied
in situ
, achieving very
fast decontamination rates (trichloroethylene [TCE] reduction of up to 99%
in few days after slurry injection) [24]. nZVI is typically mixed with water to
form slurry, which can be injected into the contaminated plume. Compared
with similar
in situ
methods, nZVI allows remediation at greater depths,
which is very important in case the target site is covered by buildings.
In contrast to all benefits, a significant weakness of the nZVI technology is
that the hydrophilic behavior of the iron particles allows for the cleanup of
aqueous phases only, which excludes the possibility for dense nonaqueous
phase liquid (DNAPL) remediation [24].
TABLE 7.1
Common Environmental Contaminants that Can Be Transformed by Nanoscale
Iron Particles
Chlorinated Methanes
Trihalomethanes
Carbon tetrachloride (CCl
4
), chloroform
(CHCl
3
), chloromethane (CH
3
Cl),
dichloromethane (CH
2
Cl
2
)
Bromoform (CHBr
3
), dibromochloromethane
(CHBr
2
Cl), dichlorobromomethane
(CHBrCl
2
)
Chlorinated Benzenes
Chlorinated Ethenes
Hexachlorobenzene (C
6
Cl
6
),
pentachlorobenzene (C
6
Cl
5
),
tetrachlorobenzenes (C
6
Cl
4
),
trichlorobenzenes (C
6
H
3
Cl
3
),
dichlorobenzenes (C
6
H
4
Cl
2
), chlorobenzene
(C
6
H
5
Cl)
Tetrachloroethene (C
2
Cl
4
), trichloroethene
(C
2
HCl
3
),
cis
-dichloroethene (C
2
H
2
Cl
2
),
trans
-dichloroethene (C
2
H
2
Cl
2
),
dichloroethene (C
2
H
2
Cl
2
), vinyl chloride
(C
2
H
3
Cl)
Pesticides
Other Polychlorinated Hydrocarbons
DDT (C
14
H
9
Cl
5
), lindane (C
6
H
6
Cl
6
)
Dioxins, pentachlorophenol (C
6
HCl
5
O), PCBs
Organic Dyes
Other Organic Contaminants
Orange II (C
16
H
16
N
2
NaO
4
S), chrysoidine
(C
12
H
13
ClN
4
), tropaeolin O (C
12
H
9
N
2
NaO
5
S)
N
-nitrosodimethylamine (C
4
H
10
N
2
O), TNT
(C
7
H
5
N
3
O
6
)
Heavy Metal Ions
Inorganic Anions
(
)
, As
AsO
3
−
(
)
, perchlorate
Mercury (Hg
2+
), nickel (Ni
2+
), silver (Ag
+
),
cadmium (Cd
2+
)
Dichromate
Cr
2
−
(ClO
-4
), nitrate (NO
-3
)
Source:
Zhang, W.,
J. Nanopar. Res.
, 5, 323, 2003. With permission.
