Graphene to Desalinate Seawater, or Maybe Not

Graphene, Image: AlexanderAlUS

Recently science writers at various news outlets have been gushing over an announcement that scientists have been able to use graphene to remove the salt from seawater. CNBC lead with the exuberant headline, “Carbon-based filter which turns seawater into drinking water could help millions.” Science Alert’s headline was “Scientists Have Invented a Graphene-Based Sieve That Turns Seawater Into Drinking Water — Holy crap.”  While the enthusiasm is evident, what is not so clear is whether there is anything here to get so excited about.  

Graphene is the latest and greatest wonder material. Graphene is a carbon lattice one molecule thick which has some amazing properties. It is something like 200 times stronger than steel and transmits heat and electricity extremely efficiently. Potentially, it could be used for a myriad of purposes, including generating electricity, building far more efficient batteries, better and faster microchips and far stronger, lighter materials. Richard Branson of Virgin Airlines, has predicted airplanes built of graphene in not the too distant future.  And yes, potentially it could make desalination more efficient.

The claims for desalinization actually made by the scientists are somewhat more tentative than the headlines. As reported by CNBC:

Realization of scalable membranes with uniform pore size down to atomic scale is a significant step forward and will open new possibilities for improving the efficiency of desalination technology,” Rahul Nair, professor of material physics at the University of Manchester, said in a statement.

“This is the first clear-cut experiment in this regime. We also demonstrate that there are realistic possibilities to scale up the described approach and mass produce graphene-based membranes with required sleeve sizes,” Nair added.”

The problem with graphene is that, while it has incredible potential, so far, it has proven very difficult to work with.  A New Yorker article by John Colapinto sums up the problem: Graphene: Fast, Strong, Cheap, and Impossible to Use.  The Telegraph also has chimed in with The truth about miracle material graphene – and why you shouldn’t listen to Richard Branson.

This is not to say that graphene desalinization is not right around the corner. It may be. On the other hand, it may take decades more research. Metallic aluminum was first produced in 1825 but was not produced industrially for another 60 years and only gained widespread use in the 20th century. Practical uses for graphene may be developed much faster, or perhaps not.  

Even if graphene desalinization is developed on an industrial basis, it still must be proven that it is more cost-effective than current reverse osmosis desalinization systems. Most of the articles praising the new technology  fail to mention that reverse osmosis desalinization is relatively energy efficient and highly scalable. Reverse osmosis systems can range from hand cranked devices which can desalinate a little over a gallon per hour to city sized facilities. The reverse osmosis plant in Sydney, Australia can produce up to 500 million liters of fresh water from sea water per day. The Sydney plant is powered by renewable energy from the Capital Wind Farm located at Bungendore.

So, yes, graphene membranes may indeed make desalination cheaper and more efficient, or not. Only time and further research will tell. 

Thanks to Alaric Bond and David Rye for contributing to this post.

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