Environmental Engineering Reference
In-Depth Information
TABLE 4.4
Methods Used to Stabilize the Nanosized Zerovalent Irons
Particle
Sizes (nm)
Materials
Description
References
Surface modification
Carboxymethyl
cellulose
The OH functional group of carboxymethyl cellulose was
involved in the interaction with synthesized NZVI.
17.2-18.6
[119,129,130]
Guar gum
The mixing of RNIP with guar gum (MW 3000 kDa and
viscosity 0.5 g L
−1
) can prevent the aggregation and
ensure the mobility of RNIP in the subsurface
environment.
162 ± 5
[120,131]
Anionic
polyelectrolytes
The adsorbed polyelectrolytes can prevent the
aggregation of RNIP by the repulsion force of
electrostatic double layer, osmotic, and elastic-steric.
5-40
[117,132]
Polymer
modiication
RNIP modiied with poly(styrene sulfonate) (PSS),
chitosan, polyaspartate, and PV3A can prevent the
aggregation.
63-75
[113,122,123]
Supporters
Hydrophilic
carbon
The supporter-stabilized NZVI was produced by the
reduction of ferrous ion adsorbed on the hydrophilic
carbon.
30-100
[124]
Membrane
Polyacrylic acid, polyether sulfone, PMMA, PVDF, and
nylon 66 would be utilized as the supporter to stabilize
NZVI with the ethylene glycol as the cross-linker.
31-60
[126,133-135]
Magnetite
NZVI synthesized by the reduction of NaBH
4
was
attached to the Fe
3
O
4
surface due to the magnetic force.
This prevents the aggregation of NZVI.
1-100
[127]
Silica
TEOS and ferrous as the precursor of silica and iron are
mixed and then through the sol-gel mechanism and
reduction of NaBH
4
the silica incorporated with NZVI
was formed.
-
[128,136,137]
smaller and narrower distribution compared with those in the absence of a membrane
matrix. Complete dechlorination of TCE was achieved within 1 h by Ni/Fe nanoparticles
inside the PAA/PES membrane (
k
SA
= 0.1395 ± 0.006 L h
−1
m
−2
), while the excessive agglom-
eration of Ni/Fe nanoparticle without the protection of membrane results in less available
surface area and slow dechlorination rate (
k
SA
= 0.0378 ± 0.003 L h
−1
m
−2
).
The stability and reactivity of bimetallic nanoparticles also can be maintained using a
stabilizer. He et al. [146] developed a new strategy for stabilizing palladized iron (Pd/Fe)
nanoparticles with sodium carboxylmethyl cellulose (CMC) as a stabilizer. The complex-
ation between carboxylate groups with metals and the intermolecular hydrogen bond
between CMC and the Fe particle surface were identiied to be the major mechanisms
for stabilizing bimetallic nanoparticles to yield stable dispersions with sizes <17.2 nm.
Batch experiments showed that the
k
obs
for TCE dechlorination by CMC-stabilized Pd/
Fe nanoparticles was 17× higher than that by nonstabilized counterparts. Column tests
showed that the CMC-stabilized nanoparticles can be readily transported in a loamy-sand
soil and then eluted nearly completely (~98%) with three bed volumes of deionized water,
whereas the nonstabilized Pd/Fe nanoparticles were retained on the top of the soil column
[146]. In addition, the fresh CMC-stabilized nanoparticles offer a 2× greater
k
obs
value for
TCE dechlorination when compared with the starch-stabilized Pd/Fe nanoparticles [49].
