Nanoscale Porous Materials for Water Treatment: Advances and Challenges - Nanotechnologies for Water Environment Applications - page 335

oxide/hydroxide precipitation. SEM pictures clearly show a growth of a fine urchin-like
crystallite (7 days), which may lead to an apparent amorphous phase (60 days). The
very thin crystallites (about 100 nm long by 20 nm wide) are expected to be
energetically unstable and should in turn disappear to be replaced by more stable phases
according to the Gay-Lussac-Oswald ripening rule (Kanel et al., 2005).
Figure 11.9 (a) SEM image of pristine NZVI, and As (III) sorbed on NZVI for (b) 7, (c)
30 and (d) 60 days, respectively. Reaction conditions: 100 mg/L As(III) adsorbed on 50
g/L NZVI in 0.01 M NaCl at pH 7, 25 o C (Kanel et al., 2005).
Recently, INPs in bimetallic form (by coupling with Pb, Ni, Zn, etc.) have
emerged great attention. This makes it possible to increase catalytic properties as well as
to remove redox sensitive contaminants more effectively (Schrick et al., 2002; Zhang,
2003; Kanel et al., 2005; Nurmi et al., 2005). These kinds of composites have a lot of
potential for the removal of various contaminants by different means; the mechanism
includes adsorption, oxidation/reduction, ion exchange, etc. In this way, these
nanoparticles can reduce/degrade a variety of organic pollutants (e.g., chlorinated
alkanes and alkenes, chlorinated benzenes, pesticides, organic dyes, nitro aromatics,
PCBs) and inorganic anions (e.g., nitrates) in aqueous solutions to less toxic and
recalcitrant by-products (Li et al., 2006). Application of bimetallic Fe 0 nanoparticles