Environmental Engineering Reference
In-Depth Information
4. I NERTIZATION BY C HEMICAL R EACTION
The waste material containing heavy metal (cadmium) can be inertized or
neutralized by the following chemical method:
Concentrated aqueous solution of orthophosphoric acid and an alkaline
salt are mixed in themolar ratio of 1:5 to 5:1, followed by addition ofwater to
make a homogenous paste. In this homogenous paste, calcium hydroxide
and/or calcium oxide is add and theresultant homogenous paste air dried
(Graziano, 2003). The material thus obtained is fit fordisposal according to
local environmental legislation (Figure 5)
Figure 5. Intertization by Chemical Reaction.
The above mentioned conventional techniques are in use for inertization
of cadmium. However, these techniques have their own inherent limitations,
such as less efficiency, sensitive operating conditions, and production of
secondary sludge requiring further, costly disposal (Ahluwalia and Goyal,
2005). These disadvantages, together with the need for a more economical and
effective method for recovery of metal from wastewater, have resulted in the
development of alternative separation technologies. One such alternative is
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