Environmental Engineering Reference
In-Depth Information
However, during the leachate characterization period, we noticed a very high COD
(50,000-67,900 mg/l), indicating acetogenic-phase characteristics on a few occasions [16]. It
is obvious that the uncontrolled dumping of the waste can yield similar results due to an
irregular degradation pattern of the waste. The manual mixing of the waste can inluence
reporting of high concentration of nutrients such as nitrate-nitrogen, ammonia-nitrogen,
and phosphate. In addition, most of the chemical constituents tested exceeded the permis-
sible levels of wastewater discharge in the country [59].
37.3.2 Characterization of Nanoparticles
37.3.2.1 Starch-Coated NZVI
XRD patterns of prepared S-NZVI are shown in Figure 37.2. According to Figure 37.2, the
characteristic peak at 44.7° indicates the crystallization of Fe
0
for S-NZVI [52]. In addition
to iron, a very faint peak observed at below 8.0°
possibly suggests a trace of green rust, and
broad peaks around 20° and 35° suggest the presence of some ferrihydrite as a result of
oxidation. The BET surface area of the S-NZVI was recorded as 136.0 m
2
/g, indicating very
high surface area-to-volume ratio. The TEM images of S-NZVI are shown in Figure 37.2.
Accordingly, it is clear that Fe
0
particles are present in nanoscale and appear in spheroidal
shape. Furthermore, the needle- or cubic shape-like structures can be due to the presence
of trace amounts of goethite and maghemite.
37.3.2.2 Iron Oxide Nanoparticles
The crystal structure of the synthesized IONPs was investigated by XRD using Cu K
α
radiation.
As shown in Figure 37.3, the XRD pattern of the synthesized nanoparticles was well matched
with the “γ” phase of the iron oxide (γ-Fe
2
O
3
) crystalline [60]. There are six characteristic peaks
at 2⊖
= 31.7°, 36.7°, 41.1°, 53.4°, 57.0°, and 62.6°, corresponding to the Miller indices of γ-Fe
2
O
3
at
(220), (311), (400), (422), (511), and (440), respectively [61]. The BET surface area of the IONP was
recorded as 150.0 m
2
/g [62]. TEM data in Figure 37.3 indicate that the γ-Fe
2
O
3
nanoparticle has a
(a)
(b)
Metallic iron
200
150
100
Ferrihydrite
50
Metallic iron
100 nm
0
20
30
40
50
60
70
80
2θ
FIGURE 37.2
XRD pattern (a) and TEM image (b) for synthesized starch-stabilized NZVI. Peaks refer to ferrihydrite and
metallic iron. Scale bar represents 100 nm, and aggregation of spherical shape nanoparticles is imaged.
