Environmental Engineering Reference
In-Depth Information
Toxic elements like zinc (8.24+0.0755), lead (1.9±0.023%), sulphur
(12.23±0.2%), cadmium (317±23.8ppm), chromium (178±24.7 ppm), copper
(1043±25.7 ppm) are found to be higher than in CCRs and clay. This result has
been supported by the earlier work (Hage and Schuing, 2000; Romero and
Rincon, 1997).
The microstructure of jarosite waste, CCRs and clay particles are shown in
Figure 5. It is evident from the SEM studies that jarosite waste and CCRs
collected from the ash pond are non-uniform in structure and shape as
compared to ash collected through electrostatic precipitator which has
spherical, hollow shaped particles. It is revealed from this microstructure that
most of the jarosite waste particles are irregular in shape with multiple humps.
The surface of the particles found smooth and large lumps containing lot of
porosity. However, the particles are made of flaky particles with some binder.
Further, particle surface irregularities indicate that these particles have got
good binding properties with other foreign materials. Clay particles are
irregular in shape with sharp edges and most of them are non-uniform in shape
and are expected to provide good packing.
3.1.2. Mineralogical, Radioactivity and Leachate Characteristics of
Jarosite Waste and CCRs
The mineral phases in the jarosite waste, CCRs and clay are shown in
Figure 6. The major mineral phase in jarosite is Potassium Iron Sulphate
Hydroxide {KFe
3
(SO
4
)
2
(OH)
6}and
Iron Sulphate Hydrate {2Fe
2
O
3
SO
3
.
5H
2
O}. In CCRs the dominant phases are quartz {SiO2}, mullite {3Al
2
O
3
2SiO
2} and hematite {Fe
2
O
3
}.
Dominant mineral phases in clay are cistobalite
quartz {SiO
2
} and kaolinite
{Al
2
O
3
, 2SiO
2
, 2H
2
O}.
Table 7 shows the radioactivity level of hazardous jarosite waste and
CCRs and compared with the upper limits commonly present in normal
building materials. The radioactivity level of Indian jarosite waste and CCRs
are found to be almost similar or less than that of normal soil. The upper limits
of naturally occurring radio nuclides such as
232
Th (parent radio nuclide of
228
Ac),
226
Ra and
40
K in CCRs and jarosite waste are below the concentrations
reported elsewhere (UNSCEAR, 1982; Vijayan, 1999; Asokan et al., 2005 &
2007) and those in normal building materials (Moghissis, 1978; Rama-
chandran and Mishra, 1990).
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