Environmental Engineering Reference
In-Depth Information
an ABC triblock polymer nanosphere template for maghemite formation [122]. In this
system, water-dispersible iron oxide nanoparticles with controlled sizes can be obtained
by changing the triblock polymer nanosphere template. Recently, polymer gels have also
been proposed for the fabrication of MNPs [123]. The nucleation and growth of iron oxide
are controllable by the constrained architectures of the polymer gel [124].
The fabrication of MNPs by incorporating the iron oxide particles inside polymer par-
ticles by
in situ
polymerization has also been developed [125]. For example, Pich et al. have
reported the preparation of magnetic composite particles by a two-step method [126]. In
the irst step, Fe
3
O
4
nanoparticles are prepared, and in the second step, they are encapsu-
lated into formed poly(styrene/acetoacetoxyethyl methacrylate) particles directly during
the polymerization process. The morphology of hybrid particles can be changed by chang-
ing the monomer/iron oxide ratio.
14.2.3.4 Other Strategies
Some classic and novel adsorbents, such as activated carbon and carbon nanotubes (CNTs),
have also been proposed as modiied media for the fabrication of multicomponent MNMs
because of their strong adsorption capacity onto toxic contaminants [127,128]. For example,
iron oxide/carbon magnetic composite has been prepared by using a facile
in situ
one-
pot template-free solvothermal reaction with the magnetic precursor of iron(III) in EG
media and mesoporous carbon [127]. Magnetic CNTs can be fabricated by Fenton's reagent
method without the addition of any cations. In this case, H
2
O
2
was added slowly into an
Fe
2+
salts solution mixed with puriied CNTs, and the resulting reactants were heated
under a nitrogen/hydrogen low to form magnetic CNTs, with Fe
2
O
3
nanoparticles uni-
formly dispersed on CNTs [128].
14.3 Iron-Based MNMs in Water Treatment
Today, various techniques have been proposed for water treatment, such as adsorption,
biotechnology, catalytic processes, membrane processes, ionizing radiation processes,
and magnetically assistant processes [8]. When it comes to selecting the optimal method
and material for practical applications, factors including quality standard, eficiency, and
expenditure must be taken into consideration [129,130]; those featured with lexibility,
high eficiency, reusability, environmental security and friendliness, and economic fea-
sibility [130,131]. Since magnetism is a unique and promising physical property that
independently helps in water puriication, so adsorption/catalysis procedures combined
with magnetic separation have been extensively proposed and developed for water treat-
ment and environmental cleanup [8,132]. The MNMs have been proven promising on
an industrial scale owing to their low cost, strong adsorption capacity, easy separation,
and enhanced capacity [133-135]. It has been reported that series of organic and inorganic
matters (e.g., metal ions, anti-inlammatory drugs, antibiotics, analgesics, pesticides, insec-
ticides, dyes, surfactants, carcinogens and phenolic compounds, etc.) can be effectively
removed from aqueous solutions by using MNMs. According to the removal mechanism,
these MNMs can be divided into two categories, i.e., adsorbents and catalysts. In many
cases, both adsorptive and catalytic processes are involved in practical water treatment.
