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Global WarmingHealthScienceWater

New Nano-tech Device Takes Salt Out of Sea Water

With clean water access becoming an issue of major concern for many of the world’s peoples, we are seeing more investment in water desalination (salt removal) and purification technologies and systems. While current desalination technology (using ‘reverse osmosis’ filtering) can effectively remove salt from water, the process is slow and does not remove some pollutants and microbial pathogens.

Now comes a nano-technology solution from the engineers at MIT in the form of a super-tiny, ion channel polarization (ICP) system–so small that hundreds could fit on one’s thumbnail…

Engineers at MIT–lead by Jongyoon Han–have recently developed a promising nano-tech system for separating charged salt ions from water, and which also separates out unicellular contaminants. But more challenges remain.

In an ICP system, sea water is sent through a tiny channel that is forked at one end, and which has an electrical potential applied to it–repelling the charged ions in the water (the NA+ and Cl – ions) and forcing them to separate from the water and into a separate channel.

This 4 mm-by-4 mm wafer (insert) may one day help researchers create portable desalination devices that could provide fresh drinking water during emergencies.

The innovative system has also been tested for its ability to filter/separate out potential pathogens in the form of microbes (bacteria, etc.), using red blood cells (RBCs) that contain a fluorescent protein used for tracking cellular movement.  The ICP system successfully separated the RBCs out of the water stream (as determined by the lack of fluorescence in the water).

But other challenges and drawbacks remain: the system does not yet remove all pollutants (charcoal filtering would still be necessary), and smaller pathogens might possibly make it through undetected (note: filtering water through a matrix of titanium dioxide [TiO2] nano-particles shows promise for water purification).

Further, the envisioned, portable device has yet to be built, as currently, the desalination system exists only on a small disc and would need to be scaled up considerably to provide appreciable amounts of clean water.

Seawater Diagram showing concentrations of various salt ions in seawater: Cl− 55%, Na+ 30.6%, SO2−4 7.7%, Mg2+ 3.7%, Ca2+ 1.2%, K+ 1.1%, Other 0.7%

Some critics doubt whether the device is superior to traditional reverse osmosis filtering systems (in which pressure is applied to sea water, forcing the ions through a one-way membrane) in removing salt and thus making ‘potable’ drinkable water. However, this criticism can be addressed as the system is scaled up and water purity analyses are conducted.

The engineers at MIT, reporting in the journal Nature Nanotechnology (March, 2010), see the future, scaled-up version becoming a life-saving gadget in areas hit hard by drought (forcing people to flee towards coastal regions), which climate change forecasts predict will occur at greater frequency in the coming years.

Nanotechnology involves the manufacturing of devices that control matter at the atomic or molecular level. Huge advances in nanotech have been achieved in the past decade, making it one of the most investment-intensive, new industries to emerge in the 21st Century.

More information about this nanotech development can be found here.

top photo: (Sea water in the Strait of Malacca)  Jyi1693, wikipedia.org, Creative Commons Attribution-ShareAlike 3.0 License.

Nanotech diagram: Credit: Mark A. Shannon, Nature Nanotechnology, 5, Advance Online Publication (April 2010); (inset) Sung Jae Kim/MIT.

bottom diagram: Seawater Diagram showing concentrations of various salt ions in seawater; derivative work: Tcncv (talk), Sea_salt-e_hg.svg: Hannes Grobe, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany; SVG version by Stefan Majewsky, Creative Commons Attribution-Share Alike 2.5 Generic license.




3 comments
    1. Michael Ricciardi

      Dear Apar

      this is an important question. mos people of conscience who care about preserving the natural world that we depend upon, ask themselves this question. Sometimes, it seems that the problem is so big, so over-whelming, that nothing we do seems significant enough.

      …but there are many things we can do:

      First, become informed on the important ecological and environmental issues that affect your local community, region and nation.

      Reach out (“network”) to others with similar concerns and interests.

      Join an organization that does good work that you support.

      Make contact with local, regional and (if possible) national leaders who have decision-making power on eco/enviro policies.

      When you can afford to, donate money to local / regional / national / international groups that are working to preserve ecosystems, natural resources..or those seeking to strengthen eco/enviro laws (and stay in touch with these folks).

      Encourage friends and relatives and neighbors to take small measures to protect the quality of your immediate natural environment.

      Try to decrease one’s energy consumption and waste generation (if you drive a car to work, try to carpool at least twice a week).

      Seek and use alternative energy sources (energy use and needs vary from country to country, so, this may require some research).

      Recycle as much as possible (starting a recycling campaign in your neighborhood or community is a good step).

      Teach your children well.

      Anyone of these is a step in the right direction. No one is perfect (no one is an “eco saint”). Do your best.

  1. davidryal

    Great find! I always wondered as a kid why people didn't just evaporate and recondense sea water if they wanted drinking water…

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