Application of Zero-valent Iron Nanoparticles for Environmental Clean Up - Advanced Materials for Agriculture, Food and Environmental Safety - page 403

He et al. [24] reported that the degradation ei ciency of CMC-stabilized
Fe-Pd nanoparticles for trichloroethylene is ~17 times faster than their
non-stabilized counterparts in terms of rate constant. In one more study
conducted with para-nitrochlorobenzene, CMC-stabilized Fe-Pd nanopar-
ticles were reported four times more ei cient than non-stabilized nFe 0
[86]. Zhou et al. [87] successfully demonstrated the potential of CMC-Fe 0 /
Pd nanoparticles for dechlorination of 2,4-dichlorophenoxyacetic acid to
phenoxyacetic acid.
The long-term stability of nFe 0 can also be enhanced by immobi-
lizing it in a support. The immobilization of nFe 0 with some support
could simultaneously provide three advantages. The first one lies with
the ability of supporting material to control the growth of nanopar-
ticle as well as aggregation; the second one is related to the protection
provided to nanoparticles against oxidation and hydrolysis in water;
the third one is the preconcentration of the target contaminant around
nFe 0 via adsorption on the surface of supporting material, which in turn
enhances the overall reactivity of nFe 0 . In addition, supported nanopar-
ticles are more convenient in terms of their real application [64, 65].
Park et al. [88] successfully immobilized nFe 0 on an ion-exchange resin
sphere, which not only combats the problem of agglomeration but also
reduces the amount of ammonia produced during nitrate reduction,
which is otherwise a major limitation for nFe 0 . Zhang et al. [89] pro-
posed kaolin as an ideal support for nFe 0 and demonstrated its use in
removing Pb(II) from aqueous solution. Cellulose acetate, activated
carbon, bentonite, resin, etc., have been successfully used as supporting
agent for nFe 0 [64, 65, 90-92].
h e entrapment of iron in calcium alginate beads [93, 94] or chitosan
beads [95] serves the purpose of preventing oxidation and agglomera-
tion without compromising the reactivity of nFe 0 . Krajangpan et al. [96]
revealed that alginate gel cluster acts as a bridge that binds the nFe 0 par-
ticles together. Kim et al. [97] immobilized nFe 0 in alginate bead to inves-
tigate the degradation of trichloroethylene (TCE). h e study reported
that the iron released from alginate bead is <3% of the loaded iron. Liu
et al. [98] utilized epichlorohydrin (ECH) as crosslinker to improve the
mechanical strength of chitosan-nFe 0 (CS-nFe 0 ) beads. In comparison to
CS-nFe 0 beads, ECH-CS-nFe 0 beads were found to possess higher ther-
mal stability. Liu et al. [98] further demonstrated that ECH-CS-nFe 0 beads
could be regenerated and reused by washing with dilute HCl. h e contami-
nants which are successfully degraded by stabilized or supported nFe 0 are
displayed in Table 14.2.