Environmental Engineering Reference
In-Depth Information
2.3. Gaseous Cadmium Waste
Volcanic action is considered to be a major contributor for the presence of
atmospheric cadmium and results from the vast amount of matter discharged,
together with the enrichment of cadmium in the volcanic aerosol.
Other natural sources of atmospheric cadmium include ocean sprays,
forest fires and the release of metal-enriched particles from terrestrial
vegetation. A notable exception is that of certain carboniferous shales found in
various parts of the world which are enriched with cadmium. The soils derived
from these deposits and the vegetation growing in the soils also contain
elevated cadmium levels (Hutton et al., 1987).
Higher levels of cadmium may be found in soil or water near industrial
areas or hazardous waste sites. High levels of cadmium in surface soils usually
result from cadmium particles settling from the air. Soils near roads may
contain high levels of cadmium from vehicular exhaust.
In short, this metal is a serious cause of environmental degradation.
Therefore, it is necessary to alleviate cadmium from all kind of wastes.
Keeping these views in the mind, there could be two possible solutions to
escape from cadmium exposure.
First, recovery of cadmium metal from cadmium containing products,
such as batteries and others and recycle or reuse. Secondly, solidify and
inertize the cadmium containing waste. The former solution is present with
restriction as a limited amount of cadmium could be reused and the total
amount of cadmium could not be recovered. Thus, the inertization of cadmium
metal is the best and ultimate solution to cope up with the adverse
environmental effects of cadmium (Figure 2).
The details of recovery and reuse of cadmium has already been described
in detail in the previous Chapters.
The present chapter discusses types of cadmium enriched waste generated
and various options to inertize cadmium containing waste which would
contribute to the sustainable and safe use of cadmium in modern times.
Several methods for the treatment of cadmium enriched waste have been
described in literature, such as chemical and surface chemistry processes
which include precipitation, adsorption, membrane processes, ionic exchange,
floatation, and others (Kefala et al., 1999; Selatnia et al., 2004). Although
some techniques are available for inertization of cadmium, however, it
depends upon the physical property of cadmium waste. Solid cadmium waste
might be directly inertized but if it is present in liquid or gaseous state, it has
to be first converted into solid state. The solid cadmium waste would be then
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