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Nanotechnology for Clean Water

Worldchanging guest writers David Zaks and Chad Monfreda are graduate research assistants at the Center for Sustainability and the Global Environment at UW-Madison where they study how human activities affect our planet.

wssboydrinking.jpg We live on the Blue Planet, but 97% of Earth's water lies in the oceans. Salt water can neither be drunk nor used for farming. Therefore, a cheap, efficient method to turn seawater into freshwater is something of a holy grail in water planning, offering as it would the means to help alleviate water scarcity. Current desalination methods, though, are either energy intensive and expensive, or (like the Watercone or fogcatchers) only workable on small scales.

That may be about to change. A team of researchers at the Lawrence Livermore National Laboratory recently published a paper (subscription required, companion paper) in Science detailing a method to produce carbon nanotube membranes that could reduce the cost of desalination by 75%. As Technology Review reports:

The carbon nanotubes used by the researchers are sheets of carbon atoms rolled so tightly that only seven water molecules can fit across their diameter. Their small size makes them good candidates for separating molecules. And, despite their diminutive dimensions, these nanopores allow water to flow at the same rate as pores considerably larger, reducing the amount of pressure needed to force water through, and potentially saving energy and costs compared to reverse osmosis using conventional membranes.

Both liquids and gases flow through the carbon nanotubes at rates thousands of times greater than in conventional polycarbonate membranes. If the nanotube membranes can effectively separate salt from water, they might also be useful for removing CO2 and other pollutants from flue gases. The researchers anticipate that it will take five to ten years before the technology will be ready for the market. Innovations like this show that while some applications in nanotechnology like molecular manufacturing are decades off, others are almost ready to change the world.

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Great post! Very interesting to catch up on this!

Posted by: anonymous on 15 Jun 06

Interesting how small but crucial changes in materials science change the world. Nanotubes are getting easier and easier to make in quantity and length. It seems that hardly a month passes now that we don't find some new application for them.

Posted by: Pace Arko on 15 Jun 06

The Namib Desert, one of the driest regions in the world, gets less than half an inch of rain per year. But early in the morning, a light fog drifts over the desert, offering the plants and animals living in that harsh environment their only chance for a life-sustaining drink.

When that fog rolls in, the Namib Desert beetle is ready with a moisture-collection system exquisitely adapted to its desert habitat. Inspired by this dime-sized beetle, MIT researchers have produced a new material that can capture and control tiny amounts of water.

The material combines a superhydrophobic (water-repelling) surface with superhydrophilic (water-attracting) bumps that trap water droplets and control water flow. The work was published in the online version of Nano Letters on Tuesday, May 2.

Potential applications for the new material include harvesting water, making a lab on a chip (for diagnostics and DNA screening) and creating microfluidic devices and cooling devices, according to lead researchers Robert Cohen, the St. Laurent Professor of Chemical Engineering, and Michael Rubner, the TDK Professor of Polymer Materials Science and Engineering.

Posted by: andreas buechel on 15 Jun 06

Metal foams made of grains and pores only nanometers or billionths of a meter wide are lighter than Styrofoam, enough to float on water. The extraordinarily high surface areas these unprecedented foams possess suggest they could serve as excellent platforms for chemical reactions that for instance help generate electricity or remove pollutants, experts told UPI's Nano World.

Posted by: andreas buechel on 15 Jun 06



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