Bimetallic Nanoparticles - Nanotechnologies for Water Environment Applications - page 160

Roberts, 1998), and bimetallic complexes (e.g., Pd/Fe, Pd/Zn) (Muftikian et al., 1995;
Grittini et al., 1995; Fennelly and Roberts, 1998; Cheng and Wu, 2000; Liou et al.,
2005).

Table 7.1 Standard reduction potential for selected metals (Lide, 1993).
Half-reaction Standard Reduction Potential (V)

Li + + e - → Li

-3.05

Na + + e -

-2.71

→ Na

Mg 2+ + 2e - → Mg

-2.37

Al 3+ + 3e - → Al

-1.66

Mn 2+ + 2e - → Mn

-1.18

Zn 2+ + 2e -

-0.76

→ Zn

Fe 2+ + 2e - → Fe

-0.44

Co 2+ + 2e - → Co

-0.28

Ni 2+ + 2e - → Ni

-0.25

2H + + 2e - → H 2

0.00

Cu 2+ + 2e - → Cu

+0.34

Ag + + e - → Ag

+0.80

Pd 2+ + 2e -

+0.95

→ Pd

The promising ZVI technology has been further enhanced when the iron
nanoparticle technology was first developed in 1996. The research group at Lehigh
University has actively investigated the ability of iron and bimetallic (e.g., Pd/Fe and
Ag/Fe) nanoparticles to degrade a wide variety of contaminants including chlorinated
compounds (Zhang et al., 1998; Lien and Zhang, 1999, 2001, 2005), polychlorinated
biphenyls (PCBs) (Wang and Zhang, 1997), chlorinated benzenes (Xu and Zhang, 2000),
perchlorate (Cao et al., 2005), and heavy metals (Cao and Zhang, 2006; Li and Zhang,
2007) in both laboratory studies and field applications. In these studies, the average
particle diameter of the nanoscale iron was 50-100 nanometers (nm) versus
approximately 10 micrometers ( m) or larger for commercially available iron powder

(i.e., microscale iron). The much larger specific surface area of the nanoparticles (e.g.,
35 m 2 /g versus < 1 m 2 /g) translates into significantly enhanced reactivity, as the zero
valent metal degradation reactions are surface mediated.

μ

Taken together, the use of zero-valent metals including iron filings, zero-valent
aluminum, bimetals, nanoscale iron, and bimetallic nanoparticles has been shown a great
success in treatments of various contaminants (Figure 7.1). In general, zero-valent
metals have various functionalities for remediation of contaminants. As shown in Table
7.2, they may serve as a reductant for the reductive degradation of chlorinated organic
solvents (e.g., Matheson and Tratnyek, 1994; Lien, 2005), nitrate (Cheng et al., 1997;