Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Barely any nanosilver from consumer products in the water

18.04.2013
Environmental toxicology

Nanosilver in wastewater can cause severe environmental damage if it occurs as a metal. A study conducted within the scope of the National Research Programme "Opportunities and Risks of Nanomaterials" (NRP 64) now shows that nanosilver is quickly transformed into less problematic substances on its way to the wastewater treatment plant. In addition, it is efficiently retained in the sewage sludge so that only a small portion of it reaches the water systems.

Nanosilver is the show horse in the nanotechnology stable – not only does it hold great promise for the future, it is already contained in hundreds of consumer products today. Cosmetics, food packaging, disinfectants and cleaning agents are but some examples. Nanosilver is also commonly used in antibacterial socks and functional clothing. An estimated 300 tonnes or more of nanosilver are used each year the world over – and a substantial part of it enters the water cycle via wastewater. Within the scope of the National Research Programme "Opportunities and Risks of Nanomaterials" (NRP 64), a team led by Ralf Kägi from Eawag in Dübendorf has for the first time examined more closely (*) just what happens to nanosilver on its journey from the drainpipe to the wastewater treatment plant, and in what form it is eventually released into the environment.

Wastewater samples and laboratory experiments
The researchers took samples from the Swiss wastewater system in order to study how nanosilver is transported. In addition, they established through laboratory experiments what happens to nanosilver in wastewater or in the wastewater treatment plant. They discovered that nanosilver does not remain in its metallic form for very long: it is efficiently transformed into a silver sulfide salt. "We presume that sulfidation already largely takes place in the sewer channel," Kägi says. That's good news, because "these salt crystals cause much fewer problems, the silver is much less soluble in this form". Dissolved ions are the main reason why silver can be harmful to the environment and can stop bacteria from getting to work in the sewage sludge.

The Eawag researchers have for the first time clearly shown that nanosilver, too, is quickly transformed into silver sulfide – regardless of how the particles are coated. Until now this effect was only known from wastewater produced by the photo industry. Whether as metallic nanoparticles, as dissolved silver ions or as an insoluble silver saline deposit, the original form of the silver apparently does not play a crucial role in sulfidation. However, the salination speed depends heavily on the size of the particles: small nanosilver (10 nanometres) is very rapidly transformed, while larger particles may never fully sulfidise and may continue to release silver ions into the environment.

Efficiently removing silver from wastewater
The researchers were also able to show that approximately 95% of the nanoparticles are bound in the sewage sludge. Only 5% of the silver remains in the treated water. This percentage could be further reduced by using better particle filters. Venturing into the nano dimension would not be necessary, though: the sulfidised nanosilver aggregates almost entirely on large particles in the wastewater. With a reasonable effort, they could be removed more efficiently from the wastewater than is presently the case.

The study did not examine what happens to nanosilver in the sewage sludge thereafter. In Switzerland, it is not permissible to use sewage sludge on farmland, and most of the sludge is therefore burned. The heavy metals separated in this process should not be released into the environment in large quantities.

(*) Kägi Ralf, Voegelin Andreas, Ort Christoph, Sinnet Brian, Thalmann Basilius, Krismer Jasmin, Hagendorfer Harald, Elumelu Maline and Mueller Elisabeth. Fate and transformation of silver nanoparticles in urban wastewater systems (2013). Water Research: doi 10.1016/j.watres.2012.11.060
(available as a PDF from the SNSF; e-mail: com@snf.ch)

About NRP 64
The aim of the National Research Programme "Opportunities and Risks of Nanomaterials" (NRP 64) is to close research gaps so that the opportunities and risks of using nanomaterials can be more accurately assessed. The results of the 23 research projects will serve as a basis for the preparation of guidelines for the production, use and disposal of nanomaterials. This will support the development and application of safe technologies, optimise the benefits of using nanomaterials and minimise risk for humans and the environment. NRP 64 has a budget of CHF 12 million and will run until October 2016.


Contact
Dr. Ralf Kägi
Eawag
Überlandstrasse 133
Postfach 611
8600 Dübendorf
Switzerland
Tel.: +41 58 765 52 73
E-mail: ralf.kaegi@eawag.ch

Communication division | idw
Further information:
http://www.nfp64.ch
http://www.snsf.ch

More articles from Life Sciences:

nachricht Water forms 'spine of hydration' around DNA, group finds
26.05.2017 | Cornell University

nachricht How herpesviruses win the footrace against the immune system
26.05.2017 | Helmholtz-Zentrum für Infektionsforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>