Environmental Engineering Reference
In-Depth Information
nanoparticles by co-precipitation route, two stages are mainly involved,
a short burst of nucleation occurs when the concentration of the species
reaches critical supersaturation, and then, there is a slow growth of the
nuclei by dif usion of the solutes to the surface of the crystal. To fabri-
cate monodisperse iron oxide magnetic nanoparticles, these two key stages
should be separated, i.e., nucleation should be avoided during the period
of enlargement.
During the last few years, signii cant advances in preparing monodis-
perse magnetite nanoparticles of dif erent sizes have been made by the use
of organic additives as stabilization or functionalization agents. Recently, a
novel magnetic nanoadsorbent for the removal of Cu
2+
was i rst developed
by the surface modii cation of chitosan-coated magnetic nanoparticles
(CCMNPs) with
α
-ketoglutaric acid (
α
-KA), which is a natural, inexpen-
sive, harmless and environmentally-friendly biological reagent containing
active functional groups like carboxyl groups [67]. h e TEM pattern of
γ
-Fe
2
O
3
shows monodisperse rodlike and rhombohedral shape with the
particle sizes of 110 and 10 nm, respectively, while the TEM picture of
the CCMNPs shows discrete spherical shape. It was earlier reported that
the shapes of the Fe
2
O
3
products are rodlike to spherical, and the particle
size of the sample had been clearly changed at er modii cation by the sur-
factants. h e TEM images also reveal that the CCMNPs synthesized in this
study are multidispersed with a mean diameter of around 30 nm, and no
marked aggregation occurs. It can be clearly seen that the chitosan coat-
ing process signii cantly altered the morphology of
γ
-Fe
2
O
3
nanoparticles.
It has been shown that the
γ
-Fe
2
O
3
nanoparticles were coated by the chi-
tosan, and the prepared CCMNPs exhibited good distribution.
Ta i
et al.
[68] fabricated magnetic porous microspheres of Fe
3
O
4
@
poly(methylmethacrylate-co-divinylbenzene) by a simple strategy of
co-precipitation reaction. h e magnetic microspheres materials, consist-
ing of polymer-coated iron oxide nanoparticles, were synthesized by the
modii ed suspension polymerization of methacrylate and divinylbenzene
in the presence of a magnetic l uid. h e large surface area and stabilized
magnetic porous polymeric microspheres of Fe
3
O
4
@poly(methylmeth-
acrylate-co-divinylbenzene) were used in the adsorptive removal of phe-
nol from aqueous solution. It had been observed that the distribution of
the oleic acid-coated Fe
3
O
4
nanoparticles is comparatively uniform; in
addition, the oleic acid-coated magnetite nanoparticles easily aggregate.
Recent studies showed that oleic acid is an excellent candidate for the sta-
bilization of magnetic Fe
3
O
4
and
γ-
Fe
2
O
3
nanoparticles [68, 69].
Hong
et al.
[70] demonstrated that precipitation of Fe
3
O
4
nanoparticles
with NH
4
OH instead of NaOH gives a better crystallinity, higher saturation
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