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. Typically, 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 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.
DailyTech - Fresh Drinking Water From Salt Water Coming Using New Chlorine-tolerant Membrane
