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Researchers Develop Portable Desalination Device

A new energy-efficient desalination device, the size of a postage stamp, could be made into a portable desalination system operated by current battery technology

American and South Korean researchers have demonstrated a nano-technology based method for converting sea water into drinking water. So far, the invention only purifies tiny amounts of water, but scientists say the technology may someday be used in low-power facilities to remove salt and other contaminates.

The desalination process was tested on a postage stamp-size chip, which uses an electric current to help separate electrically charged salt particles and other impurities from water to make it drinkable.

Conventional, industrial-size desalination facilities use a process called reverse osmosis to filter salt and other contaminants out of sea water. But they are expensive to run and require a lot of power, which makes them a poor fit for many low-income countries, says Massachusetts Institute of Technology Biotechnology Professor Jongyoon Han. "Many of these countries that suffer from the water shortages also [do not] have the water delivery infrastructure, do not have electricity infrastructure to power these large scale plants. I think these are some of the combined challenges that we need to address," he said.

Han and his colleagues have developed ion concentration polarization, which improves the efficiency of the filtering process by adding a small electrical charge to the salt and other impurities.

The chip removed 99 percent of the salt and other contaminants from samples of undrinkable water.

Han says the technology might one day be available as a personal water purification appliance or used to bring drinking water to communities by scaling up the technology to create plates containing thousands of chips. "And then run all of these little devices at the same time to get the flow rate at the levels of perhaps a hundred milliliters per minute. That flow rate is the typical flow rate you can get from the household filtration devices," he said.

Han would like to develop a way to power the devices so they can bring water in the wake of natural disasters, such as this year's devastating earthquake in Haiti. "It needs to be run without the need for continuous power supply because some of these countries or disaster zones [do not] have working power or electricity. So, we think the power efficiency of this device is good enough so we can run this small unit with the solar power," he said.

Han describes the desalination-on-a-chip technology this week online in the journal Nature Nanotechnology.