[Ssaninfo] Research on silver nanoparticles in sewage sludge
cstalberg at ccalternatives.org
Thu Dec 1 06:03:50 EST 2011
Researchers identify silver nanoparticles in sewage sludge of wastewater
(Nanowerk Spotlight) Silver nanoparticles are one of the most extensively
used type of nanoparticles in consumer products due to the unique
antibacterial activity of silver. There have been raising environmental
concerns over their adverse ecological effects, along with ionic silver
potentially released from the particles...
"Secondly, the presence of silver sulfide nanocrystals in sewage sludge
materials is now identified, and it is necessary to investigate the
time-dependent changes in their chemical and physical properties when they
enter different environments later in their life. For example, this would be
the case for using the sewage sludge materials containing silver sulfide on
agricultural lands as a soil amendment."
Transformation of Silver Nanoparticles in Sewage Sludge
The release and environmental fate of nanoparticles throughout the life
cycle of "nanoenabled" goods is an area of growing research interest. In the
first known field study of the fate of silver nanoparticles in the
wastewater treatment system, researchers now report these nanoparticles
transform into silver sulfide in the sludge produced by sewage treatment
plants.1 This new information about the life cycle of silver nanoparticles
provides a starting point for further exploring their impact on the
Silver has been used as an antimicrobial agent for millennia,2 and the
increased surface area offered by the nanoparticle form of the metal offers
greater germ-killing capacity.3 Today, manufacturers add silver
nanoparticles to hundreds of consumer products, including food storage
containers, clothing, computer keyboards, cosmetics, pillows, cell phones,
and medical appliances.4
In general, silver sulfide is highly insoluble and settles out of water.7
But no one knows if silver sulfide nanoparticles behave in the same way.
Properties of metals can change dramatically as particle size decreases.3
"It's hard to predict whether the solubility of nanoparticles will increase,
decrease, or stay the same," Kim says. The bioavailability, toxicity, and
reactivity of silver sulfide nanoparticles also are unknown.
If silver sulfide nanoparticles do prove toxic, the environmental
implications could be unfavorable. Antimicrobial nanoparticles could
adversely impact desirable microorganisms that decompose waste in sewage
treatment plants, says Murray McBride, director of the Cornell Waste
Management Institute. Furthermore, McBride says, nanosized silver sulfide
applied to agricultural land could oxidize in soils and release toxic silver
ions that kill beneficial soil microorganisms.
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