Nanoscale Porous Materials for Water Treatment: Advances and Challenges - Nanotechnologies for Water Environment Applications - page 353

synthesize catalytically active and redox sensitive catalysts coating on silica substrate,
which led to high removal rates. The synthesis of porous TiO 2 nanoparticles has
increased the surface area of these nanoparticles, which enables them to remove more
contaminants in the presence of light than that of conventional TiO 2 (Narr et al., 2007).
Discovery of nanoporous bioactive materials such as Ag 0 has helped to enhance the
removal capacity of bacteria using these materials. Zerovalent iron is a common
material used for groundwater remediation. ZVI-NPM (INPs) are much more effective
than that of conventional ZVI. The INP surface can be modified for groundwater
treatment such as arsenic. The surface area of S-INPs is about 3 times higher than INPs.
This led to increased removal of contaminants. Kanel et al. (2005) found that the surface
normalized rate constant of As(III) on INPs is about 3 orders of magnitude greater than
ZVI. Similarly, the arsenic attached on nano iron oxides can be removed using a small
strength magnet (Yavuz et al., 2006).
The nano iron and INPs are not mobile, and thus, has limited use. Hence, surface
modified INPs have been developed and tested for removal of arsenic and TCE (Schrick
et al., 2004; Li et al., 2006; Kanel and Choi, 2007; Kanel et al., 2007b). The S-INPs can
be used as a CRB material to treat deep groundwater contaminants. While there are
some studies to test S-INPs ( Schrick et al., 2004; Kanel and Choi, 2007; Kanel et al.,
2007b) as a CRB material in column experiments, more research in pilot and field scale
is needed in the future. Kanel et al. (2007) studied S-INPs transport in a 2-D porous
media packed tank and found that the S-INPs moves like a tracer without significant
retardation and driven by the density of the particles (Kanel et al., 2007a). It is also
found that the density effect cannot be distinguished by column experiments; hence,
more studies are needed in 2-D systems.
The applicability of NPM has been proven; further development is needed in the
targeted synthesis of new materials with specific and selective properties for known
applications. New NPM suitable for in-situ and ex-situ applications in water treatment
will definitely attract further special attention in the forthcoming years. We envision that
NPM will become critical components in industrial and public water purification
systems as more progress is made toward the synthesis of new NPM that are cost-
effective, efficient and environmental friendly for use.