Environmental Engineering Reference
In-Depth Information
Wa n g
et al.
[95] have developed a novel amino-functionalized Fe
3
O
4
@
SiO
2
magnetic nanomaterial with a core-shell structure for the adsorp-
tive removal of heavy metals from aqueous solutions. h e average particle
sizes of Fe
3
O
4
, Fe
3
O
4
@SiO
2
, and Fe
3
O
4
@SiO
2
-NH
2
were observed to be
13.4, 16.6 and 18.4 nm, respectively. High adsorption ai nity for aqueous
Cu(II), Pb(II), and Cd(II) was achieved through the complexation of metal
ions by amino groups grat ed on the silica surface of the nanomaterial,
and the adsorption was not much impacted by the presence of cosolute of
humic acid or alkali/earth metal ions. h us, the result observed shows that
core-shell structure of the nanoadsorbent formed by a magnetite wrapped
with an inert silica layer provides ease of magnetic separation and protec-
tion from acid leaching in regeneration. h ese unique characteristics of
synthesized Fe
3
O
4
@SiO
2
-NH
2
nanoparticles give a high potential for ef ec-
tive and rapid removal of toxic metal ions in water treatment.
Very recently, Song
et al.
[96] prepared polyrhodanine-encapsulated
magnetic nanoparticles via one-step chemical oxidation polymeriza-
tion and investigated their potential for adsorptive removal of heavy
metal ions from aqueous solutions. h e TEM images showed that the
polyrhodanine-encapsulated magnetic nanoparticles were synthesized
with an average diameter of ca. 10 nm. Typically, 5.0 mg of the PR-MNPs
was added into 10 mL of Hg(II) ion solution (80 mg/L) at a pH value of 4.0.
h en, the prepared samples were shaken at 350 rpm using a mechanical
shaker at 25
C in a batch mode. At er a desired contact time, the PR-MNPs
were removed from the solution using an external magnetic i eld. An
inductively coupled plasma (ICP) analysis was observed for the residual
Hg(II) ion concentration in the aqueous media. Similarly, the adsorption
capacities of Cd(II), Mn(II), and Cr(III) ions were also determined. It was
found that the adsorption capacity increases sharply with an increase in pH
from 2.0 to 4.0, but increases slightly with a pH rise from 4.0 to 8.0. h is
means that the concentration of H
+
ion signii cantly af ects the adsorption
behavior of PR-MNPs. h e negative surface charge enhances the ai nity to
positively charged metal ions. h e increment rate of adsorption capacity
diminished in the pH range of 4.0 to 8.0. h e highest Hg(II) ion adsorp-
tivity was 94.5% at the initial mercury ion concentration of around 1.3
mg/L. Parameters of two isotherm models, Langmuir and Freundlich, were
tested for the adsorption of Hg(II) ion onto the PR-MNPs. Comparing the
R
2
value and
F
-test result of both models, it was concluded that the exper-
imental data were well i tted to the Freundlich model, which suggests the
heterogeneous metal ion adsorption activity. h is may result from the dif-
ferent adsorption sites (oxygen, nitrogen, and sulfur groups) of polyrhoda-
nine-magnetic nanoparticles that have dif erent metal-binding energies.
°
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