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nanotimes News in Brief

Carbon Nanotubes // Nanotechnology for Water Filter

of Vienna, Austria, is currently carrying out research on how carbon nanotubes can be used in filters.

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They developed a method called “passive sampling”. Data produced by this new method are much more reliable for realistic applications as they include con- centrations likely to occur in the environment (ge- nerally very low). This was not possible with classical methods that can only deal with elevated concentra- tions.

First, the “passive sampling method” was developed which allows measuring the affinity of a category of carcinogenic contaminants – i.e. Polycyclic Aromatic Hydrocarbons (PAHs) – to carbon nanotubes. “Series of tests which use analytical chemistry and electron microscopy were performed with collaborators from the University of Utrecht in the Netherlands, to ensu- re that the method is suitable, reliable and optimised for carbon nanotubes,” illustrates Thilo Hofmann. Once validated, the “passive sampling method” was used to measure the affinity (absorption and adsorp- tion) of several contaminants (PAHs) to carbon nano- tubes over a very wide range of concentrations.

Another aspect investigated by the scientists of the Department for Environmental Geosciences is the phenomenon of competition between contaminants.

team of researchers at the Department of Environmental Geosciences at the University

Many chemicals often co-exist in the environment, especially in polluted bodies of water. If competition occurs, it means that a contaminant may not attach to carbon nanotubes if better competitors co-exist. Competition is not acceptable for filter application as the efficacy of the filter will vary according to the quantity and type of contaminants present. Studying competition also provides information on the mecha- nisms of sorption.

Using classical techniques with relatively high con- centrations showed that competition can be very strong when three PAHs co-exist with carbon na- notubes. Conversely, experiments with the “passive sampling method” at concentrations likely to occur in the environment showed that no competition occurs if 13 PAHs are considered together. This example highlights the importance of developing and using experimental methods to produce results relevant to environmental conditions. There are still many questions to answer to fully evaluate the potential of carbon nanotubes to clean polluted water.

“We keep on working on the subject and the results of our last experiments will be soon presented at international conferences,” concludes the environ- mental geoscientist, Thilo Hofmann.

11-06/07 :: June/July 2011