Application of Zero-valent Iron Nanoparticles for Environmental Clean Up - Advanced Materials for Agriculture, Food and Environmental Safety - page 406

Li and Zhang [57] explained the reduction of metal cations on the basis
of the standard oxidation-reduction potential of the metal ions. For metal
with E 0 very close to or more negative than that of iron (-0.41 V), such as
Zn(II) and Cd(II), the removal mechanism is sorption/surface complex
formation. For metals with E 0 greatly more positive than iron, for instance
Cu(II) and Hg(II), the removal mechanism is predominantly reduction.
Metals with E 0 slightly more positive than that of iron, as in case of Ni(II)
and Pb(II), can be immobilized at the nanoparticle surface by both sorp-
tion and reduction.

14.4 Pilot- and Field-Scale Studies

As the nFe 0 -based remediation approach has considerable benei ts over
conventional treatment technologies, a rapid transfer of nFe 0 technol-
ogy from laboratory to i eld-scale application has been done in the last
decade. Several in situ i eld demonstrations of nFe 0 technology have been
undertaken and are being developed to remediate contaminated soil and
groundwater. In general, there are two ways to employ nFe 0 in groundwater
and soil remediation: (i) through permeable reactive barriers (PRB), which
contain the reactive iron, and (ii) through injection well, wherein nanopar-
ticles establish a plume of reactive iron in subsurface environment.
Puls et al. [99] used Fe 0 in PRB for in situ remediation of groundwater
contaminated from an old chrome-plating facility located on an US Coast
Guard Air Station near Elizabeth City, North Carolina, and observed chro-
mate reduced to less than 0.01 mg L -1 . Wilkin et al. [100] also reported
Cr(VI) reduction in groundwater from 1500 μg L -1 to <1 μg L -1 in PRB
installed at US Coast Guard Support Center located near Elizabeth City,
North Carolina. Similar results were observed by Flury et al. [101] in PRB
installed at Willisau, Switzerland, for in situ treatment of groundwater con-
taminated from wood preserving industries.
Elliott and Zhang [102] studied i eld-scale dechlorination of trichloro-
ethene-contaminated groundwater through nFe 0 /Pd at an industrial and
manufacturing facility situated in Trenton, New Jersey, USA. As per their
report, ~ 890 L of nFe 0 /Pd suspension at concentration of 1.5 g/L on the
i rst day and 450 L of 0.75 g/L nFe 0 /Pd on subsequent days, was gravity
fed into trichloroethene-contaminated groundwater. h ey observed a
reduction ei ciency of about 96% over a 4 week period following injec-
tion. Another i eld test was carried out at an industrial facility located in
Research Triangle Park, North Carolina, wherein 1600 gallons of nFe 0 slurry
(1.9 g/L) were injected into the groundwater contaminated with volatile