Environmental Engineering Reference
In-Depth Information
To examine whether the -FeOOH was coated on the -Fe
2
O
3
nanoparticles via
surface precipitation or formed precipitate independently during the synthesis process,
the magnetic separation of the -FeOOH-coated -Fe
2
O
3
and pure -FeOOH was
investigated. The -FeOOH-coated -Fe
2
O
3
nanoparticles with a mass ratio of 1.0 were
first mixed with water and then tested for magnetic separation using a magnet. It was
found that the nanoparticles were completely separated from the solution within 30 sec
as shown in Figure 9.10a. To distinguish the -FeOOH from -FeOOH-coated -Fe
2
O
3
,
the same separation test was conducted with a mixture of -FeOOH, -FeOOH-coated -
Fe
2
O
3
and water. One can see from Figure 9.10b that the sample was turbid with a
certain amount of the particles attracted by the magnet. After sedimentation for 5 h, it
was still turbid and some of particles were settled at the bottom of the beaker (Figure
9.10c). The attracted particles and the settled particles were confirmed, using XRD, to be
-FeOOH-coated -Fe
2
O
3
and -FeOOH, respectively. Since the -FeOOH is weakly
magnetic, it cannot be separated with a small magnet. Thus, it can be deduced that the -
FeOOH was coated on the -Fe
2
O
3
cored rather than becoming precipitate independently.
Figure 9.9
Hysteresis loops of uncoated and -FeOOH-coated -Fe
2
O
3
nanoparticles
(Hu et al., 2007b).
Search WWH ::
Custom Search