Environmental Engineering Reference
In-Depth Information
The products were continually heated in an oven at 250
o
C for 2 h in order to oxidize the
Fe(II) to Fe(III). Finally, Cu-, Mg-, Zn-, and Ni-doped -Fe
2
O
3
nanoparticles containing
Fe/(Fe + Me) of 10 mol% were obtained.
For Al-doped Fe
3
O
4
with 10 mol% Al, part of FeCl
3
should be replaced by AlCl
3
,
and hence, the molar ratio of FeCl
2
: AlCl
3
: FeCl
3
should be 10:3:17. To produce X (X =
7.5, 9.3, 11, 13.1) molar percentage of Al-doped -Fe
2
O
3
nanoparticles, amounts of
AlCl
3
, FeCl
2
and FeCl
3
salts with a molar ratio of 3X:1:(2-3X) were prepared with the
same procedures used for producing divalent metal doped -Fe
2
O
3
. The chemical
reaction is expressed as follows:
XAlCl
3
+ FeCl
2
+ (2-X)FeCl
3
+ 8NaOH FeAl
X
Fe
(2-X)
O
4
(s)
+ 4H
2
O + 8NaCl
(Eq. 9.6)
9.4
Nanoparticles Characterizations
9.4.1 Characterization of -Fe
2
O
3
The transmission electron microscopy (TEM) micrograph in Figure 9.2 reveals that the
-Fe
2
O
3
synthesized using the sol-gel method was multidispersed with an average
diameter of around 15 nm, like Fe
3
O
4
. The crystalline structure of the prepared
nanoparticles was verified by X-ray diffraction
(
XRD). From Figures 9.3, XRD peaks of
the crystallite match well with the -Fe
2
O
3
standard before and after Cr(VI) adsorption.
Figure 9.2 TEM Image of -Fe
2
O
3
.
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