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New membrane will help to ensure many parts of the world have easy access to drinking water.

One of the biggest, but least appreciated problems facing many regions of the world is lack of clean drinking water, a common problem in impoverished nations.  Ironically, many of these nations rest beside large bodies of salt water. Ttypically, processing salt water into fresh water is expensive and requires large dedicated plants.

DailyTech previously chronicled how wind-power driven desalinization plants which used membranes were being developed.  Now another major breakthrough in the field has been devised, this time concerning the membranes.

Researchers from several international universities have developed a chlorine-tolerant membrane which turns salt water into clean drinking water.  Typically, salt water is treated with chlorine to remove bacteria and microorganisms that would grow and form a biofilm on the membrane, blocking it.  However, chlorine destroys past membranes which were build using amide-polymers (nitrogen based).  This meant that that the water had to be dechlorinated before being sent to the membrane, a relatively expensive and complex process.

The new membrane is formed from sulfonated copolymers.  It took researchers Professor Benny Freeman with the The University of Texas at Austin, James E. McGrath of Virginia Tech University, and Ho Bum Park of the University of Ulsan in South Korea three years to develop the membrane for which they have filed a patent.  The new membrane is resistant to chlorine allowing the elimination of dechlorination.

Says Professor Freeman, "If we make the desalination process more efficient with better membranes, it will be less expensive to desalinate a gallon of water, which will expand the availability of clean water around the world.  It promises to eliminate de-chlorination steps that are required currently to protect membranes from attack by chlorine in water.  We believe that even a small increase in efficiency should result in large cost savings."

Researchers also believe the design will help reduce carbon dioxide emissions in developing nations by decreasing the electrical needs of the generation process. 

Professor Freeman explains:

Energy and water are inherently connected.  You need water to generate power (cooling water for electric power generation stations) and generation of pure water requires energy to separate the salt from the water. That energy is often generated from the burning of fossil fuels, which leads inevitably to the generation of carbon dioxide. Therefore, if one can make desalination more energy-efficient by developing better membranes, such as those that we are working on, one could reduce the carbon footprint required to produce pure water.

It was a combination of luck and hard work that brought the researchers upon the novel suflonated class of membranes.  This class of materials enjoys a high tolerance to aqueous chlorine, making it surprisingly a far better fit than membrane materials currently in use.

Professor Freeman, who holds the Kenneth A. Kobe Professorship in Chemical Engineering and the Paul D. & Betty Robertson Meek & American Petrofina Foundation Centennial Professorship in Chemical Engineering, states, "Basically, Dr. McGrath radically changed the chemical composition of the membranes, relative to what is used commercially, and the new membranes do not have chemical linkages in them that are sensitive to attack by chlorine."

The research was funded by the Office of Naval Research and the National Science Foundation-Partnerships for Innovation Program. 

The findings will be reported in a paper in this month's edition of the German Chemical Society's journal, Angewandte Chemie, with Mehmet Sankir and Zhong-Bio Zhang, both of Virginia Tech, as additional coauthors.

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Another potential positive
By FITCamaro on 7/23/2008 12:22:38 PM , Rating: 2
Depending on how quickly these can desalinate water, you could build a conventional nuclear plant on the coast using sea water.

I know there are already plants that use just regular seawater but while I don't know the specifics, I would think that adds to the cost since you have to use metals that don't corrode. If this new membrane could keep up, you could convert the seawater to freshwater eliminating the need for the more corrosive resistant materials.

RE: Another potential positive
By SilentSin on 7/23/2008 3:13:19 PM , Rating: 2
I was thinking along those lines. Why hasn't more research been done in the area of desalination by distillation? It's not cost effective to use everywhere-it takes a lot of energy to heat water to the boiling point-but there are certain processes that we already use that release water vapor as a waste product.

Why not capture the vapor and use that? I've seen the cooling towers of the Shearon Harris plant in NC up close and it looks like it releases a metric shitton of watervapor into the sky (some of it does condense and is used to replenish the lake from which it draws). I couldn't even begin to think what kind of volume it actually releases. Distilled water isn't exactly eco-friendly, but it could be used to irrigate crops for sure and minerals could be added after distillation to make it a little less harsh to release back into nature.

The problem is always that the places with energy to spare are often not the places that need the water. Transportation will be a huge issue. In the future we may see water tankers instead of oil tankers, carrying lake-fuls of water to drying cities. It might not be as glamorous and profitable a business as oil transportation, but it is desperately needed.

The past few years in the southeastern US have been especially dry. Many places had lower water tables than any other point in time during recorded history. The Shearon Harris plant that I mentioned above was actually close to having to shut down because lake levels were so low. If we're having problems like that in the US, one of the most resource-rich locations on the planet, I can only imagine what it's like elsewhere.

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