Although we've seen some interesting alternatives being developed, for now the most commonly-used water filtration media are silicon gels and activated carbon. These materials can only be used once, however, after which they're discarded. By contrast, not only can filters made with carbon nanotubes be reused, but they're also reportedly more effective at removing organic pollutants.
Led by John-David Rocha and Reginald Rogers, scientists at Rochester Institute of Technology started by creating high-quality, single-walled carbon nanotubes – carbon nanotubes are microscopic rolled-up sheets of graphene, which in turn is a one-atom-thick sheet of carbon atoms linked together in a honeycomb pattern.
These nanotubes were then sorted according to whether they were of the semiconducting or metallic type. The semiconducting tubes were subsequently incorporated into thin carbon-paper-like sheets, which were used to filter tainted water. Because carbon nanotubes repel water, no water molecules stuck to the material. This left it free to adsorb more organic contaminants.
Once the sheets were saturated with trapped particles, they could simply be placed in a microwave oven for five minutes – this caused the contaminants to evaporate, leaving the sheets ready to be used again.
"This type of application has not been done before," says Rogers. "Nanotubes used in this respect is new."
A paper on the research was recently published in the journal Environmental Science Water: Research and Technology.
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