Environmental Engineering Reference
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mainly present as maghemite along with some goethite. Upon controlled
H
2
treatment, the iron oxides were reduced to metallic iron with higher
magnetization of composite. h e adsorption of Cu
2+
, Cr
3+
and Zn
2+
from
aqueous solutions on the 3:1 zeolite:Fe oxide composite was investigated.
h e adsorption capacity was in the order of Cr
3+
> Cu
2+
> Zn
2+
.
9.3.4
Metal Oxides-Based Nanocomposites
Research on metal oxides-based nanocomposites is an important strategy
to overcome the drawbacks of binary metal oxide absorbents. Mahmoud
et
al.
[82] prepared novel nanosorbents by surface impregnation of magnetic
nano-iron oxide (Nano-Fe
3
O
4
) with nano-silicon oxide (Nano-SiO
2
) for the
formation of (Nano-Fe
3
O
4
-SiO
2
) sorbent. h e material was further func-
tionalized with target nitrogen donor atoms via covalent surface binding
and immobilization of triethylenetetramine (TETA) for the formation of
(Nano-Fe
3
O
4
-SiO
2
-TETA) sorbent. h e average particle size was found in
the range of 14-40 nm based on the SEM analysis. h e nanosorbents were
examined to evaluate their selectivity and ei ciency in removal of Cu(II)
and Pb(II) from water samples by the batch equilibrium and micro-col-
umn techniques. Nano-Fe
3
O
4
-SiO
2
-TETA sorbent was identii ed by a high
Cu(II) sorption capacity (480 μ mol g
-1
) in pH 7.0, while Nano-Fe
3
O
4
and
Nano-Fe
3
O
4
-SiO
2
sorbents were characterized by high ai nity to Pb(II).
Mahapatra
et al.
[83] prepared Fe
2
O
4
-Al
2
O
3
nanocomposite i ber using
electrospinning method metal ions from aqueous solution. Firstly, boehm-
ite nanoparticle was synthesized by sol-gel method and was impregnated
in PVP-Iron acetylacetonate solution in a ratio of 1:1:2. h is boehmite-
impregnated polymer solution was electrospun to form nanocomposite
polymer i ber. Iron oxide alumina mixed nanocomposite i ber was character-
ized by UV-vis-DRS, IR, SEM-EDX and TEM. h e removal percentage metal
was found in the order of Cu
2+
< Pb
2+
< Ni
2+
< Hg
2+
. h e maximum sorption
capacities by applying the Langmuir equation were found to be 4.98 mg/g for
Cu
+2
, 32.36 mg/g for Ni
+2
, 23.75 mg/g for Pb
+2
and 63.69 mg/g for Hg
+2
ions.
Lee
et al.
[84] reported hydrothermal preparation of l ower-like TiO
2
-
graphene oxide (GO-TiO
2
) hybrid by stirring a titanium oxide precursor
in isopropyl alcohol with GO colloidal solution. h e GO-TiO
2
hybrid was
applied for the removal of heavy metal ions from water. h e l ower-like
TiO
2
on GO structure signii cantly improved the removal ei ciency of
heavy metals. At er 6 h and 12 h of hydrothermal treatment at 100
C, the
GO-TiO
2
hybrid adsorption capacities of heavy metal ions were respec-
tively 44.8 ± 3.4 and 88.9± 3.3 mg/g for removing Zn
2+
, 65.1± 4.4 and 72.8
± 1.6 mg/g for removing Cd
2+
and 45.0 ± 3.8 and 65.6 ± 2.7 mg/g for remov-
ing Pb
2+
at pH 5.6. In contrast, colloidal GO under identical conditions
°
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