Nanoscale Porous Materials for Water Treatment: Advances and Challenges - Nanotechnologies for Water Environment Applications - page 333

2006; Wiesner, 2006). Recently, some excellent reviews have summarized the synthesis,
properties, and environmental applications of INPs (Huber, 2005; Li et al., 2006;
Tratnyek and Johnson, 2006; Wiesner, 2006; Narr et al., 2007). We emphasize here on
some of the important properties of INPs, including the density and intrinsic reactivity of
surface sites and their applications in water treatment. These properties directly
influence the chemical behavior of such particles and, consequently, affect their
applications in water and wastewater treatment. In general, INP is prepared by reductive
precipitation of ferrous iron [Fe(II)] with sodium borohydride under controlled
conditions. Ferric iron (Fe +3 ) can be reduced according to the following reaction (Glavee
et al., 1995):

Fe(H 2 O) 6 3+ + 3BH 4 - + 3H 2 O = Fe o ↓ + 3B(OH) 3 + 10.5H 2 (1)

Figure 11.7 shows the TEM image of INP prepared in this way and the INP's
fast reaction for As(III) treatment (Kanel et al., 2005).

2.0

1.6

1.2

0.8

0.4

R 2 = 0.97

0.0

0 2 4 6 8 10

Concentration of NZVI (g/L)

50nm

Figure 11.7 (Left) INP; and (Right) removal of As(III) by INP (Kanel et al., 2005).

Based on synthesis techniques, INP surface properties and its porosity vary
which consequently affect INPs' adsorption properties. For example Kanel et al (2005)
prepared INP using the NaBH 4 reduction method under inert atmosphere and obtained
INPs with diameters of 5-100 nm and the surface area of 24.4 m 2 /g. It is observed
clearly from the TEM picture and XRD that INPs remain as core-shell structure, with the
outer layer being iron oxide and inner core zero valent state. This makes INPs a versatile
adsorbent to interact with various contaminants. Hence, there have been several
successful reports on applications of these INPs for water treatment using different
model contaminants, including As(III), As(V), Cr(III), TCE, PCE, NO3-, humic acids,
U(VI), etc. INPs have been found to degrade chlorinated hydrocarbons such as