Environmental Engineering Reference
In-Depth Information
increased the dechlorination rate by a factor of two as compared to the reaction system
with iron nanoparticles alone. It is worthy of note that Cr(VI) decreased the degradation
rate of carbon tetrachloride by iron nanoparticles. In comparison to the iron reduction
system in the absence of heavy metals, the dechlorination of carbon tetrachloride was
two times slower in the presence of 25 mg/L Cr(VI). This is consistent with previous
studies (Schlicker et al., 2000; Dries et al., 2005), suggesting a competitive effect
between the strong oxidant Cr(VI) and carbon tetrachloride in reaction with ZVI.
0.3
0.3
0.25
0.25
0.2
0.2
0.15
0.15
Nano Fe alone
Nano Fe alone
0.1
0.1
0.05
0.05
0
0
As 5+ Cr 6+ Cu 2+ Pb 2+
As 5+ Cr 6+ Cu 2+ Pb 2+
"T
"T
$S
$S
$V
$V
1C
1C
Heavy Metals
Heavy Metals
Figure 7.13 Effect of heavy metals on rates of the carbon tetrachloride degradation by
iron nanoparticles.
Both engineered and in situ formed bimetallic iron nanoparticles show a similar
performance in terms of the carbon tetrachloride degradation. As illustrated in Figure
7.14, the observed rate constant of carbon tetrachloride degradation for engineered and
in situ formed bimetallic Cu/Fe nanoparticles is 0.2 and 0.25 1/h, respectively. The latter
was formed in an aqueous solution containing 30 mg/L carbon tetrachloride and 25 mg/L
Cu(II) in the presence of 0.25 g iron nanoparticles. This suggests that implementation of
iron nanoparticles for remediation of mixed contamination with both chlorinated organic
contaminants and metallic ions is sufficient.
7.3.3
Mechanisms of Surface-Mediated Dechlorination
It is well-accepted that metal-mediated dechlorination is mainly a surface
 
 
Search WWH ::




Custom Search