Environmental Engineering Reference
In-Depth Information
18,000
16,000
SS
TS
14,000
12,000
10,000
R
2
= 0.28
8000
6000
R
2
= 0.63
4000
2000
0
0
100
200
300
Total iron concentration (mg L
-1
)
FIGURE 4.6
Correlation of total iron concentrations with total solid (TS) and suspended solid (SS) concentrations. (Cited
from Wei YT et al.,
J Hazard Mater
, 211, 373,
2012.)
The injection dose of nZVI is largely inluenced by geochemical conditions in the
groundwater. The optimum geochemical conditions of groundwater for nZVI applica-
tions, including DO, ORP, pH, and permeability, have been proposed (2-4). The nZVI in
the groundwater tends to modify the geochemical conditions that facilitate the biotic and/
or abiotic degradation of contaminants [27,154-156]. In general, the presence of nZVI tends
to lower ORP, reduce DO, and increase pH. By monitoring the change of geochemical vari-
ables, the effective zone created by nZVI may be mapped. However, some cases reported
conlicting results as no signiicant change of these variables after the nZVI injection was
observed [157]. Other factors that may be used to map the effective zone and monitor the
mobility of nZVI are total iron concentration, dissolved iron concentration, total solid, and
suspended solid. Unlikely the secondary variables, e.g., ORP, pH, and DO, these factors
are more directly related to nZVI if one can conirm that the solid and iron ions originated
from nZVI [154]. We suggest that iron-based suspended solid may be a relatively reliable
indicator in monitoring the effective zone and the mobility of nZVI according to the ield
study in Taiwan (Figure 4.6).
To improve the longevity, reactivity, and dosage eficiency of nZVI injection, a novel
type of nZVI has recently been developed and applied in several of Taiwan's sites contami-
nated with chlorinated hydrocarbons [162]. This novel technology calls for the embedding
of nZVI into a tunable porous supporter with high particle loading of >90%, best suitable
for design and operation of the cutoff barrier of the contamination plume. Preliminary
results are very encouraging, which will be published soon.
4.9 Conclusion Remarks
In this review, we have extensively reviewed and discussed the fabrication methods and
physicochemical properties of nZVI. Several parameters, including particle size, pH value,
metal ion concentrations, and co-contaminants, are found to signiicantly inluence the
reactivity of the nZVI toward the reduction of priority pollutants. The use of bimetallic
