By Kim Tong-hyung
Staff Reporter
Scientists have found a way to make smaller portable desalination machines, which could be ``immensely'' useful in countries with scarce water resources, or for decontaminating wells in disaster-struck regions.
The new technique, suggested by researchers from the Massachusetts Institute of Technology (MIT) and Pohang University of Science and Technology (POSTECH), is based on the use of tiny, four-by-five-millimeter devices designed to exploit the electrochemical transport phenomenon, ``ion concentration polarization.''
It would take from 1,000 to 10,000 of these devices to make a single desalination machine, which would be comparable in size to a conventional desktop computer.
Such machines would obviously be useful in the earthquake-rattled Chile and Haiti, where the shortage in drinking water has been a problem, the researchers said.
The study was published by Nature Nanotechnology, a peer-review journal.
``A device produced through the technology of our findings would produce a smaller amount of fresh water compared to existing equipment, but would be small enough to carry around, making them effective for relief efforts in disaster areas or for military use,'' said POSTECH's Kwang Kwan-hyoung, who participated in the research led by MIT's Kim Sung-jae and Han Jong-yoon.
``The hydrogen ion concentration level of the water produced by these devices range between 7 and 7.5 pH, with salt concentration of around 3 mm, thus qualifying as potable water by World Health Organization (WHO) standards. The method also allows for the removal of micro particles and pathogens.''
The shortage of fresh water is a critical global challenge, a situation made more severe by population growth and increased industrial and agricultural activities, and this has scientists around the world devoting themselves to developing more effective technologies to convert seawater into fresh water.
The current standard approaches to seawater desalination are reverse osmosis, which employs high-pressure pumps to force brine from water brine through a membrane impermeable to salt, and electro-dialysis, a process that uses electricity to draw salt ions out of water through a membrane.
Although these methods are relatively energy efficient in terms of freshwater conversion, they both require large plant-scale operations and significant amounts of power consumption, while the removal of bacteria and other pathogens presents another challenge.
Therefore, researchers have been focusing on developing portable, low-power desalination systems, which would be useful for government and military use in disaster-stricken areas or resource-limited settings. And the Korean researchers claim they have the best solution for now.
Ion concentration polarization, also called as ion depletion or enrichment, occurs when a current is passed through ion-selective membranes, and the Nature Nanotechnology paper suggests a mechanism to use this phenomenon to isolate desalinated water from seawater streams.
The desalinated and ``concentrated'' streams are divided and flow into different channels ― the process is also designed to push salt and other large particles away from the membrane, which eliminates the possibility of membrane fouling, a frequent problem in reverse osmosis and electro-dialysis plants.