[an error occurred while processing this directive]
Skip to Main Content

Latest News

Advertise Here
September 21, 2010

The Fate of Silver Nanoparticle Waste

Water Quality: Silver in our cosmetics and clothes can end up as silver sulfide nanoparticles in sewer sludge

Sarah Webb

NANOPRODUCTS Clothing, cosmetics, food containers and even plush toys incorporate silver nanoparticles for their antibacterial abilities. Shutterstock
NANOPRODUCTS Clothing, cosmetics, food containers and even plush toys incorporate silver nanoparticles for their antibacterial abilities.
  • Print this article
  • Email the editor

Latest News

October 28, 2011

Speedy Homemade-Explosive Detector

Forensic Chemistry: A new method could increase the number of explosives detected by airport screeners.

Solar Panel Makers Cry Foul

Trade: U.S. companies complain of market dumping by China.

Novartis To Cut 2,000 Jobs

Layoffs follow similar moves by Amgen, AstraZeneca.

Nations Break Impasse On Waste

Environment: Ban to halt export of hazardous waste to developing world.

New Leader For Lawrence Livermore

Penrose (Parney) Albright will direct DOE national lab.

Hair Reveals Source Of People's Exposure To Mercury

Toxic Exposure: Mercury isotopes in human hair illuminate dietary and industrial sources.

Why The Long Fat?

Cancer Biochemistry: Mass spectrometry follows the metabolism of very long fatty acids in cancer cells.

Text Size A A

Manufacturers have incorporated silver nanoparticles into more than 200 consumer products, including clothing and cosmetics, because of their antibacterial properties. Now researchers analyzing sewer sludge provide the first evidence that silver leaching from these consumer products transforms into silver sulfide nanoparticles in wastewater treatment plants (Environ. Sci. Technol., DOI: 10.1021/es101565j). The findings provide scientists with important new information about the life cycle of these nanomaterials.

Despite their widespread use, scientists know little about how nanomaterials move from manufactured products into the environment and what their impact might be. Based on a 2009 Environmental Protection Agency study of publicly-owned wastewater treatment facilities, Michael Hochella and his colleagues at Virginia Polytechnic Institute & State University knew that all these facilities had silver in their sludge. However, identifying and characterizing tiny particles among myriad organic compounds presented a daunting challenge.

So the Virginia Tech researchers decided to use x-ray transmission electron microscopy, an extremely sensitive technique that can identify both composition and structure. With micrographs of sludge from a Midwest treatment plant, they identified nanoparticles 5 to 20 nm in diameter and determined that the particles had a 2-to-1 silver-to-sulfur ratio. The scientists also obtained a crystal structure to confirm that the particles were Ag2S.

The nanomaterials likely entered the treatment plant in the form of silver nanoparticles, Hochella says, and then transformed into silver sulfide, because wastewater plants contain high concentrations of sulfide and silver readily binds to sulfur. Hochella adds that this work underscores some of the complexity in studying environmental effects of nanoparticles: "What we start with is not what ends up in nature."

The finding is remarkable, says Samuel Luoma of the University of California, Davis and an emeritus scientist with the U.S. Geological Survey. "It's one of the first times we've found a way to detect silver nanoparticles in the environment," he says.

The observations also point out the growing use of these nanomaterials, Luoma adds: "We're using enough of these silver nanoparticles in commercial products that they're already starting to show up in waste treatment facilities."

But their environmental impact is still unclear. The conversion of silver to silver sulfide within waste treatment plants could be good news for the environment, Luoma says. Bulk silver sulfide is highly insoluble in water, particularly when compared with silver ions. But even if silver sulfide nanoparticles are not traveling through water, he adds, these materials could still enter the ecosystem via animals who consume particles in the sludge.

Researchers also don't know how much incoming silver ends up as silver sulfide. The Virginia Tech researchers next plan to analyze samples from each stage of the treatment process at the same wastewater plant.

Chemical & Engineering News
ISSN 0009-2347
Copyright © 2011 American Chemical Society
  • Print this article
  • Email the editor

Services & Tools

ACS Resources

ACS is the leading employment source for recruiting scientific professionals. ACS Careers and C&EN Classifieds provide employers direct access to scientific talent both in print and online. Jobseekers | Employers

» Join ACS

Join more than 161,000 professionals in the chemical sciences world-wide, as a member of the American Chemical Society.
» Join Now!