Civil Engineering Reference
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potential for global applicability. The embedding of nanopowders in a host
matrix would have the following advantages:
The agglomeration of the nanoparticles can be minimized and hence
better utilization of the desirable properties can be possible.
The support can provide a high concentration environment of target
contaminant species around the loaded nanoparticles by adsorption.
Therefore, the rate of reaction/sorption is enhanced.
The contaminants, after being reacted/oxidized on the nano surfaces, the
resulting toxic intermediates can also get adsorbed on the support and
as a result, they are not released in the air atmosphere to cause second-
ary pollution.
The potential sorption capability of the nanoparticle-support hybrid
can be maintained for a long time.
Most important, the recovery of nanoparticles would be easy from the
host matrix and therefore their reusability can be improved.
The possibility of secondary contamination of purifi ed product water
with the nanomaterials can be minimized.
Another most important property that can be incorporated in a hybrid
matrix is the option for treatment of contaminants of different kind by a
single system instead of addressing the contaminant sequentially. Here the
challenge will be to develop cost-effective and environmentally acceptable
separation and reactive media that can be deployed in composite packed-
bed reactors (Savage and Diallo, 2005) as shown in Fig. 16.11 for purifi cation
of water contaminated by mixtures of metal ions, organic solutes and
bacteria.
When we discuss the incorporation of nanomaterials onto a host matrix,
the immediate process/technology that comes to our mind is 'membranes'.
Membranes have gained an important place in chemical technology and are
used in a broad range of applications. The key property that is exploited is
the ability of a membrane to control the permeation rate of a chemical
species through the membrane. In separation applications, the goal is to
allow one component of a mixture to permeate across the membrane freely,
while hindering permeation of other components. A membrane system
separates an infl uent stream into two streams known as the permeate and
the concentrate. The permeate is the portion of the fl uid that has passed
through the semi-permeable membrane, whereas the concentrate stream
contains the constituents that have been rejected by the membrane. Mem-
brane separation processes enjoy numerous industrial applications with the
following advantages:
appreciable energy savings
environmentally benign
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