Environmental Engineering Reference
In-Depth Information
and the higher the quality of activated carbon, the higher its cost. Also, in
practice, activated carbon is employed more frequently for adsorption of
organic compounds rather than heavy metal ions. Magnetic nanoparticles
of er a green approach for the treatment of heavy metals containing waste-
water for management and sustainable development.
11.4 Magnetic Nanoparticles
h e special and superior properties of nanomaterials have attracted much
attention in the past two decades. Particularly, magnetic nanoparticles
(MNPs) with inherent magnetic properties and high surface-to-volume
ratio have continued to draw considerable interest because of their diverse
potential applications in biological, environmental and medical diagnostic
i elds. One of the rapidly emerging research subjects involving MNPs is their
application in biological systems, including their application in magnetic
resonance imaging (MRI), targeted drug delivery, rapid biological separa-
tion, biosensors, magnetic hyperthermia therapy [55, 56], and environmen-
tal applications. h e most commonly used magnetic particles are magnetite
(Fe
3
O
4
) and maghemite (γ-Fe
2
O
3
). Other types of magnetic particles are pure
metal (Fe and Co) and spinel-type ferromagnets (MeO.Fe
2
O
3
, where M =
Ni, Co, Mg, Zn, Mn). Due to their unique size, biocompatibility, low toxicity
and superparamagnetic properties, magnetic nanoparticles are emerging as
promising tools in various i elds such as physics, medicine, biology, envi-
ronmental and material science [54]. Several types of iron oxides have been
investigated recently in the i eld of nanosized magnetic particles (mostly
maghemite [γ-Fe
2
O
3
], or magnetite [Fe
3
O
4
], single domains of about 5-20
nm in diameter), among which Fe
3
O
4
is a very promising and popular can-
didate since its biocompatibility has already been proven [54]. Over the last
decades, numerous synthetic methods have been developed to synthesize
iron oxide nanoparticles including co-precipitation [57], sol-gel synthesis
[58], microemulsion synthesis [59], sonochemical reaction [60], hydro-
thermal reaction [61], thermal decomposition [62], laser pyrolysis [63], etc.
Among these reported methods, chemical co-precipitation may be the most
promising one because of its simplicity and high productivity.
11.4.1
Properties of Magnetic Nanoparticles
In contrast to bulk iron oxide, which is a multi-domain ferromagnetic
material (exhibits a permanent magnetization in the absence of a mag-
netic i eld), iron oxide magnetic nanoparticles smaller than approximately
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