Environmental Engineering Reference
In-Depth Information
Other full-scale applications include remediation of polychlorinated eth-
enes (PCE, TCE, DCE) contaminated sites located in Hořice and Písečná,
Czech Republic, using nFe
0
alone
[108]. Yan
et al.
[109]
have compiled
several other i eld and pilot studies which have already been done or are
still in progress.
14.5
Transport of nFe
0
in Environment
Over the past years, an increasing concern regarding the transport of nFe
0
in diverse matrices has been noticed. h e reason could be attributed to the
poor colloidal stability of nFe
0
. As soon as the nanoparticles come in con-
tact with the matrix, they undergo collisions with soil grains/sediments/
aquifer materials and are subjected to adsorption, dispersion and retarda-
tion, thereby limiting their transport through matrix [110]. In addition,
their tendency towards aggregation has caused a major setback for
in situ
remediation applications. To achieve satisfactory
remediation in subsur-
face environment, it is important to improve the transport properties of
nFe
0
. h e mobility of iron nanoparticles can be enhanced via meeting two
requirements: (i) by preventing the aggregation of nanoparticles, and (ii)
by reducing the attachment of nanoparticles to matrix. In view of this, sev-
eral research groups have tested various types of surface modii ers such as
surfactants, polymers, etc., to enhance the transport of nFe
0
in contami-
nated site. For instance, poly(acrylic acid) and anionic hydrophilic carbon
form reduce aggregation among nanoparticles via electrostatic repulsion
and enhance transport of nFe
0
through soil- and sand-packed columns
[111]. Similarly, poly(vinyl alcohol-co-vinyl acetate-co-itaconic acid)
(PV3A) and triblock copolymer also increase the stability and subsurface
mobility potential of nFe
0
[112, 113].
He
et al.
[24] investigated the mobility of CMC-stabilized nFe
0
and non-
stabilized nFe
0
in glass column packed with 2.7 mL loamy soil sand bead
through column breakthrough and elution tests. In contrast to non-sta-
bilized nFe
0
, it was found that stabilized nFe
0
readily passes through the
column, and is completely dispersed in the soil. Further, ~98% of stabilized
nFe
0
eluted with three bed volumes of deionized water indicated that reten-
tion of stabilized nanoparticles in soil is irreversible. Vechhia
et al.
[114]
investigated the transport of micro- and nanoscale Fe
0
through 0.46m-long
sand-packed column in the presence of xanthan gum and obtained high
elution concentration (>0.94 for micro- and >0.88 for nano-Fe
0
respec-
tively) and recoveries (95% for micro- and 92% for nano-Fe
0
respectively)
for both. Cameselle
et al.
[115] carried out a comparison study with eight
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