Green Nanotechnology: The Solution to Sustainable Development of Environment - Environmental Sustainability: Role of Green Technologies - page 303

indicated that most of the nanoparticles were
present as Ag 2 S in the sludge and effl uent, which
points to the potential of silver nanoparticles in
wastewater treatment (Kaegi et al. 2011 ).

treatable by conventional chemical or biological
water treatment methods (Kuvarega et al. 2011 ).
Palladium-modifi ed nitrogen-doped titanium
oxide showed enhanced photocatalytic degrada-
tion of humic acid over TiON within a narrow
range of palladium concentration (Li et al.
2007a ). Pd-modifi ed WO 3 is an effi cient tool for
the decolorization of wastewater under solar light
(Liu et al. 2010 ). New biological methods have
been developed to recover precious metals from
waste streams and to concomitantly produce pal-
ladium nanoparticles on bacteria, that is, bio-Pd,
which serves as an effective catalyst for
dehalogenation of environmental contaminants,
hydrogenation, reduction, and CC reactions
(Hennebel et al. 2012 ).

6.3 Palladium Nanoparticles

Palladium nanoparticles have been synthesized
using coffee and tea extract at room temperature
(Nadagouda and Varma 2008 ). Reports for its
synthesis using broth of Cinnamomum camphora
leaf are also available (Yang et al. 2010 ). Reaction
of cyanobacterial biomass ( Plectonema borya-
num UTEX 485) with aqueous palladium (II)
chloride at 250 °C for up to 28 days produced
palladium nanoparticles (Lengke et al. 2007 ).
Oleylamine-mediated synthesis of palladium
nanoparticles was found useful for formic acid
oxidation in HClO 4 solution. The catalyst showed
no obvious activity degradation after 1,500 cyclic
voltammetry cycles under ambient conditions,
thereby holding promise as a highly active non-Pt
catalyst for fuel cell applications (Mazumder and
Sun 2009 ). Chemoselective hydrogenation of
nitroarenes has been possible by the use of car-
bon nanofi ber-supported palladium nanoparticles
(Takasaki et al. 2008 ). Catalytically active mem-
branes incorporated with microbially produced
palladium nanoparticles have been employed for
the removal of diatrizoate (Hennebel et al. 2010 ).
Remediation of trichloroethylene has been pos-
sible by use of bioprecipitated and encapsulated
palladium nanoparticles in a fi xed bed reactor
(Hennebel et al. 2009 ). Palladium nanoparticles
electrodeposited on carbon ionic liquid compos-
ite electrode are useful for electrocatalytic oxida-
tion of formaldehyde which is comparatively far
superior to many of the previously reported
formaldehyde sensors (Safavi et al. 2009 ).
Photooxidation of xylenol orange is possible in
the presence of palladium-modifi ed TiO 2 cata-
lysts, which is higher than the semiconducting
support, being infl uenced by the size of the pal-
ladium clusters on the support (Iliev et al. 2004 ).
Nitrogen/palladium-codoped TiO 2 enables
photocatalytic degradation in 3 h for eosin yel-
low, which is carcinogenic and usually not easily

6.4 Metal Oxide Nanoparticles

Milky latex of Calotropis procera and Aloe vera
extract has been used for the synthesis of “green”
zinc oxide nanoparticles which are used in
removal of arsenic from water (Tiwari et al. 2008 ;
Sangeetha et al. 2011 ). It serves as potential UV
absorbers for textiles and exhibits photocatalysis
that fi nds application in wastewater treatment,
degradation of dyes and other toxic compounds,
and soil remediation (Becheri et al. 2008 ).
Manganese-doped zinc oxide nanoparticles have
been employed in the photocatalytic degradation
of organic dyes (Ullah and Dutta 2008 ).
Nanocrystalline MgO, CaO, TiO 2 , and Al 2 O 3
adsorb polar organics such as aldehydes and
ketones in very high capacities and substantially
out perform the activated carbon samples that are
normally utilized for such purposes (Khaleel
et al. 1999 ; Lucas and Klabunde 1999 ). Many
years of research at Kansas State University, and
later at Nano Scale, have clearly established the
destructive adsorption capability of nanoparticles
toward many hazardous substances including
chlorocarbons, acid gases, common air pollut-
ants, dimethyl methylphosphonate (DMMP), and
paraoxon, 2-chloroethyl ethyl sulfi de (2-CEES)
and even military agents such as GD, VX, and
HD (Wagner et al. 1999 , 2000 , 2001 ; Rajagopalan
et al. 2002 ). Nanocrystalline metal oxides are