Environmental Engineering Reference
In-Depth Information
in gas sensors, solar cells and non-linear optical systems. Iron oxide nanoparticles
like FeO (Iron oxide), Fe 3 O 4 (Magnetite), ʱ-Fe 2 O 3 (Hematite) and ʳ-Fe 2 O 3
(Maghemite)occurnaturally.Thesearefoundinbacteria,insects,weatheredsoils,
rocks,naturalatmosphereandpollutedaerosols(CornellandSchwertmann 1996 ).
Magnetite and maghemite minerals are used in different sectors owing to their mag-
neticpropertiesasferroluids(RajandMoskowitz 1990 )(Table 2 ). Fe 3 O 4 nanopar-
ticles have received regulatory approval as an antibacterial agent and can be applied
tolimitbacterialgrowth(Ramtekeetal. 2010 ).
Nanomaterials made of fluorescent semiconductor nanocrystals (~2-100 nm)
haveelectronicpropertiesbetweenthoseofbulksemiconductorsanddiscretemol-
ecules,andarereferredtoasQuantumdots(QDs)(Brus 2007 ). Such nanomaterials
include CdTe (cadmium telluride), CdSe/ZnS (cadmium selenide/zinc sulphide),
CdSe(cadmiumselenide),PbSe(leadselenide)andInP(indiumphosphide).These
QDsmaterialshavecertainsought-afterpropertiesthatincludeanarrowemission
band,wideexcitationwavelengthandphotostability.ThesepropertiesqualifyQDs
as a candidate for applications in biomedical imaging, specific cell membrane
receptortargeting(Alivisatos 2004 ; Chan et al. 2002 ;Lidkeetal. 2004 ), and use
with cellular biomolecules such as peroxisomes (Colton et al. 2004 ) and DNA
(Dubertret et al. 2002 ) (Table 2 ). QDs are used currently in the manufacture of
advanced flat panel LED displays, and are expected to be used for ultrahigh-density
datastorageandquantuminformationprocessing(Wuetal. 2004 ). Hence, it is clear
that the ENPs are rapidly gaining wider application in consumer products and in the
industrial sector. As a consequence of their growing popularity, production and
application, environmental releases of ENPs will increase.
3
Release Pathways of Engineered Nanoparticles
in the Environment
As for other metal or organic pollutants, nanoparticles are either intentionally or
accidentallyreleased,andcomefromeitherpointornon-pointsources(Fig. 2 ). Point
or stationary sources include production facilities and wastewater treatment plants.
Treatmentplantsaremajorpotentialsourcesofreleasefornanoparticles.Asoccurs
with other inorganic or organic pollutants that are concentrated for treatment in water
treatment plants, nanoparticles may interact with organic and inorganic matter to
formcomplexes,ornewcompounds(PandeyandKumar 1990 ). Thus, nanoparticles
may be retained and interact with other environmental constituents after passing
throughtreatmentprocedures.Gottschalketal.( 2009 ) predicted significant environ-
mental concentrations of nano- TiO 2 , ZnO, CNT, Ag and fullerene in USs, European
and Swiss treated plant effluents. The concentrations of such released nanoparticles
tendtobeintheng/Lrange.Moreover,theseauthorsexpectpotentialriskstoaquatic
organisms from release of Ag, TiO 2 andZnOnanoparticles(Gottschalketal. 2009 ).
Nonpointsourcereleasesmayoccurfromleachingor“wear”ofnanomaterial-
containingproductslikepaints,varnishes,cosmetics,andcleaningagentsthatare
Search WWH ::




Custom Search