Page 24 - Environmental Nanotechnology Applications and Impacts of Nanomaterials

10 Nanotechnology as a Tool for Sustainability

be viewed as vehicles for both electricity generation and water fabrica-
tion. Nanoscale control of membrane architecture may yield membranes
of greater selectivity and lower cost in both water treatment and water
fabrication. Principles of membrane processes are summarized in
Chapter 9, and examples of the use of nanomaterials to create new
membrane systems are described.
The ability to tailor surfaces for reactivity suggests that nanomateri-
als may find considerable use as adsorbents. Polymeric nanomaterials
can be adapted to molecular templating methods to create adsorption
sites that recognize a specific contaminant. Nanobio conjugates such as
antibodies attached to mineral nanoparticles have been made to complex
specific contaminants and also allow for quantitative measurements.
While nanobio conjugates have been focused largely on analytical tech-
niques and medical applications, it is possible to imagine adsorbent/
measurement systems that allow adsorbency for a targeted contaminant
to be optimally dosed as a function of the level of contaminant in the water.
Stimulated in part by research on health effects from low levels of
arsenic exposure and changes in drinking water standards, there is an
extensive body of literature growing on the use of various iron nanopar-
ticles for arsenic adsorption. Nanostructured ferric oxides (derived in
some cases from ferroxanes), magnetite (for subsequent magnetic sep-
aration), maghemite, mackinawite, and other forms of iron have been
investigated. These materials can be easily integrated into existing
treatment trains and the most promising materials are likely to see
widespread use in potable water treatment. Chapter 10 focuses on the
development of iron-based nanomaterials as adsorbents for contami-
nants such as arsenic.

Potential impacts of nanomaterials
on organisms and ecosystems
Possible risks associated with nanomaterial exposure may arise during
nanomaterial fabrication, handling of nanomaterials in subsequent pro-
cessing to create derivative products, product usage, and as the result
of postusage or waste disposal practices. The quantities of nanomate-
rials produced per year are large and increasing rapidly. Current pro-
duction capacities for C 60 fullerene are in excess of 2,000 tons per year,
while the carbon nanotube production capacity in 2006 is in the hun-
dreds of tons per year. These volumes are small compared with the pro-
duction of more conventional TiO 2 nanoparticles, silica nanoparticles and
other materials with a longer history of commercialization. This level
of production, fueled by growing markets for products that incorporate
these materials, will inevitably lead to the appearance of nanomateri-
als in air, water, soils, and organisms.