Environmental Engineering Reference
In-Depth Information
amounts of -FeOOH were coated on the surface of -Fe
2
O
3
nanoparticles, and the
related adsorption experiments were conducted. The magnetic nucleus was designated as
2 g and the coating mass was changed from 0 to 3 g, which can be controlled during the
synthesis of such materials. The coated nanoparticles were characterized by the TEM
and VAM techniques. The TEM images show the multidispersed circular particles with
a dimension of 15 nm but cannot distinguish coated materials from cores. The XRD
patterns as illustrated in Figure 9.8 show the presence of the -FeOOH, besides the
crystalline -Fe
2
O
3
. By comparison, -FeOOH showed the lower crystalline morphology
than -Fe
2
O
3
, since its main peaks are broader and lower than those of -Fe
2
O
3
.
300
-Fe2O3
250
-FeOOH
200
(b)
150
100
(a)
50
0
10
15
20
25
30
35
40
45
50
55
60
65
70
Degrees 2-Theta
Figure 9.8
XRD patterns of -FeOOH-coated -Fe
2
O
3
nanoparticles containing mass
ratio of (a) 0.5 and (b) 1 (Hu et al., 2007b).
Furthermore, the mass of coating did not change the pattern of XRD significantly.
The VSM curves in Figure 9.9 present typical magnetization loops for pure -Fe
2
O
3
and
the -FeOOH coated -Fe
2
O
3
, with no reduced remanence and coercivity observed. The
saturation moments of the -FeOOH coated -Fe
2
O
3
with mass ratios of 1 and 2 are 2.1
emu and 1.9 emu, respectively. The -FeOOH coating indeed decreased the magnetic
properties of the particles, while the extent of the decrease is comparable for the two
coating mass tested. This decrease is mainly attributed to the contribution of the volume
of the non-magnetic coating layer to the total sample volume.
Search WWH ::
Custom Search