Nanoparticles for Treatment of Chlorinated Organic Contaminants - Nanotechnologies for Water Environment Applications - page 111

4.6 Conclusions

1) Having a higher specific surface area, nanoscale zero-valence iron (NZVI)

particles have much better TCE degradation activity than that of microscale zero-
valence iron. The high reactivity of NZVI particles allows them to rapidly
degrade TCE and PCE into harmless or less harmful degradation products.

2) NZVI particles have presented different degradation activities even though they

possess similar particle sizes and surface areas. Such differences are likely
attributed to the difference of the physical structural property of NZVI particles,
such as the amorphous disorder structure vs the crystalline structure. Depending
on the purposes of groundwater remediation, NZVI particles with appropriate
structure property have great potential to degrade aliphatic chlorinated
compounds including TCE and PCE in contaminated groundwater.

3) Unlike microscale ZVI that can only dechlorinate PCBs at a high temperature,

NZVI is capable of dechlorinating PCBs to biphenyl rapidly and effectively at
room temperature. The application of NZVI would likely facilitate the complete
degradation of PCBs in the environment.

4) NZVI may be too reactive and quickly lose its high reactivity when the particles

agglomerate together due to a high surface-to-volume ratio. The mobility and,
hence, the efficiency of NZVI may be limited when applied in the field.
Currently research is toward the development and application of catalyzed Fe
materials (i.e., Fe/Pd) and other metals such as Mg and Zn (i.e., Mg/Pd and
Zn/Pd), which have been proven capable of dechlorinating PCBs at room
temperature. A large-scale application of palladized bimetallic systems is
currently impossible because of its extremely high cost.

5) The cost of synthesizing NZVI will become affordable with the development of

nanotechnology. Further research should be made into the studies of
carriers/containers of NZVI to eliminate its disadvantages and promote the high
remediation capacity of NZVI in environmental remediation.

4.7 References

Abraham, W. R., Nogales, B., Golyshin, P. N., Pieper, D. H., and Timmis, K. N. (2002).
"Polychlorinated biphenyl-degrading microbial communities in soils and
sediments." Current Opinion in Microbiology , 5(3), 246-253.
Agarwal, S., Al-Abed, S. R., and Dionysiou, D. D. (2007). "Enhanced corrosion-based
Pd/Mg bimetallic systems for dechlorination of PCBs." Environmental Science
and Technology , 41(10), 3722-3727.
Alder, A., Oppenhelmer, S., and Young, L. (1993). "Reductive dechlorination of
polychlorinated-biphenyls in anaerobic sediments." Environmental Science &
Technology , 27(3), 530-538.