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.

Research paper

Tweet

EPA plans ten hearings on water rule rewrite
Washington (UPI) Aug 25, 2017
The Environmental Protection Agency announced today it is taking its first steps to rewrite the Waters of the United States regulation under the Trump Administration. The EPA announced today, in a notice to be published Monday in the Federal Register, that 10 teleconference meetings will be held to gather information on its plans to change the rule, which is intended to reduce water pol ... read more

Related Links
American Association for the Advancement of Science
Water News - Science, Technology and Politics

Thanks for being here; We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain. With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords. Our news coverage takes time and effort to publish 365 days a year. If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.
SpaceDaily Contributor $5 Billed Once credit card or paypal		SpaceDaily Monthly Supporter $5 Billed Monthly paypal only