Nanotechnology for domestic water purification - Nanotechnology in Eco-efficient Construction - page 370

The EZVI (emulsifi ed zero-valent iron) technology with nanoscale or
microscale iron was enhanced to address this limitation associated with the
conventional use of ZVI. Quinn et al. (2005) evaluated the performance of
nanoscale emulsifi ed zero-valent iron (nEZVI) to improve in-situ dehaloge-
nation of dense, non-aqueous phase liquids (DNAPLs) containing trichlo-
roethene (TCE) from groundwater. One of the applications of ZVI is the
removal and sorption of arsenic contamination from groundwater (Kanel
et al. , 2006). Nanopowder of ZVI as a fi ne powder cannot be used in fi xed-
bed columns unless they have granular shape (Guo and Chen, 2005).
Xu and Zhao (2007) used carboxy methyl cellulose (CMC) stabilized
ZVI nanoparticles to reduce Cr (VI) in aqueous media through batch and
continuous fl ow column study. They found that the stabilized ZVI nanopar-
ticle is more effective than the non-stabilized one for the removal of Cr
(VI). In the batch experiments, the reduction of Cr (VI) was improved from
24% to 90% as the dosage of ZVI increased from 0.04 to 0.12 g/L. In
another work, Xiong et al. (2007) studied the degradation of perchlorate in
water and illustrated the stabilized ZVI nanoparticles could increase per-
chlorate reduction rate by 53% in saline water (with concentration of NaCl
up to 6% w/w).
Giasuddin et al. (2007) investigated the removal of humic acid (HA) with
ZVI nanoparticles and also their interaction with As (III) and As (V).
Cheng et al. (2007) also applied ZVI nanoparticle and commercial form
of ZVI powder with different mesh sizes for the dechloronation of p-
chlorophenol from water. Comparison between those particles indicated
that the nanoscale was more effective for the reduction process.

Noble metal nanoparticles

The fi rst detailed report on the interaction of noble metal nanoparticles
with halocarbons appeared in 2003 (Nair and Pradeep, 2003). It was found
that noble metals at nanodimensions react with halocarbons in a manner
similar to other metals (i.e., reductive dehalogenation) leading to the forma-
tion of metal halide with no reaction byproducts. The reaction was later
extended to several halocarbons and was found to be completely effi cient
at room temperature.
The reaction of noble metal nanoparticles was studied with widely
used pesticides such as endosulfan (Nair et al. , 2003), malathion (Nair
and Pradeep, 2007) and chlorpyrifos (Nair and Pradeep, 2007). The noble
metal nanoparticles supported on alumina were very effective for the
removal of pesticides from solution. Realizing the fact that a number
of pesticides found in drinking water are organochlorine (e.g., simazine,
lindane, atrazine, etc.) or organosulfur pesticides (e.g., triazophos, quinal-
phos, etc.) or contain nitrogen-based functional groups (e.g., carbaryl,

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