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| Human World on Jan 21, 2013

New water desalination technology shows promise

Scientists from MIT have designed a next-generation water desalination membrane that could greatly improve our ability to extract drinkable water from the sea.

Material scientists from the Massachusetts Institute of Technology (MIT) have designed a next-generation water desalination membrane that could greatly improve our ability to extract drinkable water from the sea. The membrane is composed of a one-carbon atom thick sheet of graphene. Their research about this new form of nanotechnology was published on July 5, 2012 in the journal Nano Letters.

Water scarcity is a growing problem in many parts of the world. Less than 1% of the world’s freshwater is accessible for human use. Most of the water on earth is seawater. Although desalination technology exists that can extract drinking water from seawater, it is energy intensive and costly to use.

Image Credit: USGS via Wikimedia Commons.

David Cohen-Tanugi and Jeffrey Grossman are scientists from the Department of Materials Science and Engineering at MIT. They were interested in determining if graphene, a pure carbon substance, could be used for water desalination. Graphene is already being used in other technological applications such as DNA sequencing. However, its potential for use in water desalination is just beginning to be explored.

Cohen-Tanugi and Grossman built a molecular computer model to examine how well graphene could purify seawater. Graphene is produced in a sheet of bonded carbon atoms that are arranged into a hexagonal, honeycomb-shaped structure. They found that with the correct pore size in the nanometer range, a graphene membrane could effectively filter out large salt molecules while allowing smaller water molecules to flow quickly through the pores. Because graphene membranes are much thinner than conventional membranes, their use in desalination plants would have the potential to greatly reduce the amount of energy needed for water purification.

Illustration of a next-generation water desalination membrane. Water molecules are shown in white and red and sodium and chlorine ions are shown in green and purple. Image appears courtesy of David Cohen-Tanugi via MIT News.

Unfortunately, engineers have not yet found a way to punch holes in the graphene with the degree of precision that this new desalination technology would require. Hopefully, they will soon.

David Cohen-Tanugi, a PhD candidate at MIT and lead author of the study, commented on the study’s findings in a video interview with MIT News. He said:

The enhanced water permeability of nanoporous graphene could be an important advantage over existing water desalination technology. So while there is still a lot of work to be done on this topic, we are very encouraged by our existing results and we’re excited to see the role that nanoporous graphene could play in the future of global water resources.

The research was funded by an MIT Energy Initiative and a John S. Hennessy Fellowship to David Cohen-Tanugi. This research was cited by the Smithsonian as one of the top five most surprising scientific milestones of 2012.

Bottom line: Material scientists from the Massachusetts Institute of Technology (MIT) have designed a next-generation water desalination membrane that could greatly improve our ability to extract drinkable water from the sea. The membrane is composed of a one-carbon atom thick sheet of graphene. Their research about this new form of nanotechnology was published on July 5, 2012 in the journal Nano Letters.

Bridget Scanlon on groundwater depletion and solutions

Heather Cooley on reasons for and against desalination

Amy Zander led a scientific assessment on turning salt water to fresh