A team of researchers at MIT has developed a way to use atom-thin sheets of graphene for water filtration, which could lead to an inexpensive and energy-efficient way to desalinate seawater. Though we can’t exactly drink our way our way out of the effects of rising sea levels, drawing more potable water from the ocean would provide a critical boost to the world’s water resources at a time of rising heat, drought, and human demand.
Energy Efficient Desalination
Currently, the desalination method of choice is a process called reverse osmosis. The drawback is that it requires a significant level of water pressure, which in turn requires a copious amount of energy.
One solution has been to improve the efficiency of conventional reverse osmosis. The U.S. Navy, for example, has developed a prototype for a high-efficiency desalinating system that uses about 65 percent less energy.
An entirely different approach is illustrated by the University of Colorado, where researchers are working on a microbial fuel cell that can run on seawater or wastewater. Aside from generating electricity, the new fuel cell would desalinate and purify water, and also produce hydrogen gas.
A Graphene Solution for Desalination
Like the microbial fuel cell, the MIT research represents a significant break from reverse osmosis technology.
As described by MIT writer David L. Chandler, the team fabricated a sheet of graphene containing a precise series of holes, just one nanometer across. With the addition of other materials, the edges of the holes interact on a molecular level with water to either repel or attract.
Since the graphene process is based on a chemical interaction, it requires very little water pressure compared to reverse osmosis (as Chandler notes, reverse osmosis requires a membrane that is 1,000 times thicker than graphene).
In terms of energy use, a graphene-based system could generate desalinated water at a far greater rate using the same amount of energy, or it could simply be run at lower pressure.
That flexibility could provide graphene desalination systems with a greater range of applications, using small-scale solar power and other forms of renewable energy rather than having to rely on a relatively large supply of fossil fuels.
There are quite a few steps left to go between the MIT research and real-world application, though. So far the system has checked out on computer modeling. The next step would involve additional an analysis of its economic feasibility.
One Graphene to Rule Them All
If graphene seems to be popping up everywhere, that’s because, well, it is. Since its discovery in 2004, graphene has generated thousands of research papers for applications in various types of filtration (Chandler mentions DNA and gas separators, in addition to water), solar power, and next-generation electronics along with many others.
The study of this unique material has also given rise to new ways of tweaking conventional materials to achieve similar results, such as the “plastic graphene” developed at the Polytechnic University of Valencia in Spain.
Graphene is an ultra-thin, ultra-strong sheet of carbon atoms that has superior properties as a semiconductor, though it is notoriously difficult to work with, let alone fabricate on a commercial scale.
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Tina Casey specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. You can also follow her on Twitter @TinaMCasey and Google+.