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Outperforming nature's water filtration ability with nanotubes

Date:
August 24, 2017
Source:
American Association for the Advancement of Science
Summary:
At just the right size, carbon nanotubes can filter water with better efficiency than biological proteins, a new study reveals.
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At just the right size, carbon nanotubes can filter water with better efficiency than biological proteins, a new study reveals. The results could pave the way to new water filtration systems, at a time when demands for fresh water pose a global threat to sustainable development.

A class of biological proteins, called aquaporins, is able to effectively filter water, yet scientists have not been able to manufacture scalable systems that mimic this ability. Aquaporins usually exhibit channels for filtering water molecules at a narrow width of 0.3 nanometers, which forces the water molecules into a single-file chain.

Here, Ramya H. Tunuguntla and colleagues experimented with nanotubes of different widths to see which ones are best for filtering water. Intriguingly, they found that carbon nanotubes with a width of 0.8 nanometers outperformed aquaporins in filtering efficiency by a factor of six.

These narrow carbon nanotube porins (nCNTPs) were still slim enough to force the water molecules into a single-file chain. The researchers attribute the differences between aquaporins and nCNTPS to differences in hydrogen bonding -- whereas pore-lining residues in aquaporins can donate or accept H bonds to incoming water molecules, the walls of CNTPs cannot form H bonds, permitting unimpeded water flow.

The nCNTPs in this study maintained permeability exceeding that of typical saltwater, only diminishing at very high salt concentrations. Lastly, the team found that by changing the charges at the mouth of the nanotube, they can alter the ion selectivity. This advancement is highlighted in a Perspective by Zuzanna Siwy and Francesco Fornasiero.


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Materials provided by American Association for the Advancement of Science. Note: Content may be edited for style and length.


Journal Reference:

  1. Ramya H. Tunuguntla, Robert Y. Henley, Yun-Chiao Yao, Tuan Anh Pham, Meni Wanunu, Aleksandr Noy. Enhanced water permeability and tunable ion selectivity in subnanometer carbon nanotube porins. Science, Vol. 357, Issue 6353, pp. 792-796 DOI: 10.1126/science.aan2438

Cite This Page:

American Association for the Advancement of Science. "Outperforming nature's water filtration ability with nanotubes." ScienceDaily. ScienceDaily, 24 August 2017. <www.sciencedaily.com/releases/2017/08/170824141241.htm>.
American Association for the Advancement of Science. (2017, August 24). Outperforming nature's water filtration ability with nanotubes. ScienceDaily. Retrieved March 28, 2024 from www.sciencedaily.com/releases/2017/08/170824141241.htm
American Association for the Advancement of Science. "Outperforming nature's water filtration ability with nanotubes." ScienceDaily. www.sciencedaily.com/releases/2017/08/170824141241.htm (accessed March 28, 2024).

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