With roughly seventy percent of the Earth covered by water, it doesn’t make sense that clean water could be a precious commodity. But it is. Clean water is a resource that is growing increasingly scarcer. Researchers at MIT are looking to change that with a new approach to salt water desalination.
The new approach is called ion concentration polarization, and is described in a paper by Postdoctoral Associate Sung Jae Kim and Associate Professor Jongyoon Han and their associates in Korea. The paper was published on March 21st in the journal Nature Nanotechnology.
According to MIT News, “The system works at a microscopic scale, using fabrication methods developed for microfluidics devices — similar to the manufacture of microchips, but using materials such as silicone (synthetic rubber). Each individual device would only process minute amounts of water, but a large number of them — the researchers envision an array with 1,600 units fabricated on an 8-inch-diameter wafer — could produce about 15 liters of water per hour, enough to provide drinking water for several people.”
Water desalination is a time consuming and costly endeavor when using the current methods, which is usually reverse osmosis. Reverse osmosis requires salt water to be forced through membranes by strong pumps. These membranes filter out the salt but the pumps are subject to clogging and obviously require a constant flow of electricity to function.
MIT’s researchers see their “ion concentration polarization” method to be useful in a wider array of circumstances. Researchers Sung Jae Kim says, “That small size could actually be an advantage for some applications. For example, in an emergency situation like Haiti’s earthquake aftermath, the delivery infrastructure to get fresh water to the people who need it was largely lacking, so small, portable units that individuals could carry would have been especially useful.”
The researchers have already conducted successful tests of a single unit. Using seawater they intentionally contaminated with small plastic particles, protein, and human blood, the unit removed more than 99 percent of the salt and other contaminants.
The amount of electricity needed to produce the units needed for this method is slightly more than current reverse osmosis systems, but the researchers say if properly engineered, the system would only use about as much power as a conventional light bulb. Mark A. Shannon of the Center of Advanced Materials for the Purification of Water with Systems at the University of Illinois at Urbana-Champaign agrees with their assessment.
Mr. Shannon was not involved with the MIT research. He went on to say that the new system achieves “perhaps the lowest energy ever for desalinating microliters of water.” Shannon also applauds the fact that the system meets a very specific need, since there are few efficient small-scale desalination methods currently in place. This system will be useful both in remote areas of developing countries and for emergencies.