Drought isn’t just threatening the livelihood and health of people living in California and America’s Southwest. According to the Global Drought Information System, water scarcity is forcing cities around Taiwan to implement water rationing. In Madagascar, drought-caused crop failure is now threatening 200,000 people, while conditions are sliding throughout Africa’s equatorial region and south. Dengue fever is up in Brazil because of meager precipitation. Meanwhile Australia bakes, with parts of New South Wales not seeing rain in the last three years.

Lack of fresh water is a big, global problem. Yet insult is added to injury by the fact that 98 percent of the water covering Earth is salty. It can’t feed crops. It can’t quench thirst. It can’t cool power plants. The only way to use ocean water is to put it through desalination, which strips out minerals to make it fit for consumption and industrial use. But that process requires an often prohibitive amount of energy.

So it’s too bad that the filter shown above isn’t yet ready to go to work. Scientists at the Department of Energy’s Oak Ridge National Lab have demonstrated a much more energy efficient way to make potable water from the ocean. The trick is to make the filter out of the celebrated supermaterial graphene, which is a sheet of linked carbon atoms just one atom thick, with holes poked in it by oxygen ions whizzing through. Their work joins other projects advancing graphene as the heart of future energy-efficient production of safe water. Learn more below.

“Our work is a proof of principle that demonstrates how you can desalinate saltwater using free-standing, porous graphene,” said chemical physicist Shannon Mahurin, who co-led a study published recently in the journal Nature Nanotechnology.



The team made the new filter, really a high-tech version of those used for reverse osmosis, by first creating graphene sheets. Then they laid the sheets on top of a template with a micron-sized hole in it. Next, they exposed the sheet to a plasma of ionized oxygen, which shot through the graphene to knock out carbon atoms and leave precisely sized holes. These pores were sized to allow water molecules pass through but be too small for mineral compounds and salt ions.

When the team sent saltwater through their filter, they found that it rejected nearly all salt ions and left freshwater on the other side. They were able to get an order of magnitude more water moving through the graphene filter, a unit of measure called flux, than the best polymer-based reverse osmosis filters could achieve.

“If you can make the membrane more porous and thinner, you can increase the flux through the membrane and reduce the pressure requirements, within limits,” Mahurin said. “That all serves to reduce the amount of energy that it takes to drive the process.”



Study coauthor Ivan Vlassiouk said the technique they used to make the filter should be able to scale up to industrial production. “It’s a huge advance,” said Vlassiouk.

Top Image: Researchers created nanopores in graphene (red, and enlarged in the circle to highlight its honeycomb structure) that are stabilized with silicon atoms (yellow) and showed their porous membrane could desalinate seawater. Orange represents a non-graphene residual polymer. Image courtesy of Oak Ridge National Lab.