Research energy efficient desalination membrane

Published on April 3rd, 2015 | by Tina Casey

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Methane To The Rescue! New Energy Efficient Graphene Desalination Membrane For The 99%

April 3rd, 2015 by  

The folks over at Oak Ridge National Laboratory are hot on the trail of a new graphene desalination membrane, which could free up vast amounts of the world’s water resources for human use. Currently, according to the lab, more than 99% of the world’s water is undrinkable, much of that being locked up in seawater

Somewhat ironically the whole thing is based on methane, the chief component in natural gas. Those of you familiar with natural gas fracking issues might be giving it the stinkeye on that account, but let’s take a look and see what they’re up to.

energy efficient desalination membrane

The Desalination Conundrum

Conventional desalination involves a process called reverse osmosis, in which water is forced through a membrane.

Reverse osmosis is a big step up from distillation in terms of energy consumption, and more efficient systems are in the pipeline (check out this four-in-one desalination process, for example).

Despite recent improvements, though, reverse osmosis still sucks up huge amounts of energy, and part of the problem is the membrane. Conventional membranes are based on polymers (plastics). They tend to get clogged up during the process, and they have to be cleaned regularly in order to keep operating at their personal best.

One emerging solution is solar-powered desalination. Renewable energy helps to reduce dependence on fossil fuels, but it doesn’t address the membrane issue. In an increasingly crowded world, energy efficiency is a critical factor, regardless of whether you’re using fossil fuels or renewables.



An Energy Efficient Graphene Desalination Membrane

That’s where the graphene comes in. And the methane, too.

The new Oak Ridge graphene research is still in the proof of concept stage, but things look promising. The idea is to replace conventional polymer membranes with graphene.

For those of you new to the topic, graphene is a relatively new form of carbon, first discovered in 2004. Since then it has engendered thousands of research papers as scientists dig into its unique properties.

Here’s a schematic look at graphene, showing its unique hexagonal structure (the two blue areas show the chemical bonds of impurities in the graphene sheet):

graphene courtesy of ORNL

Graphene is only one atom thick but it is super-strong. A graphene membrane could be made thinner and more porous than a polymer membrane, so you would need less pressure — and therefore less energy — to push water through it.

The problem is how to make the stuff at commercial scale. Graphene is only one atom thick, so fabricating graphene is a delicate task.

The Oak Ridge team also had to figure out how to punch precisely sized holes in a sheet of graphene, large enough to let water molecules through, but too small for salt ions to pass.

Here’s how the lab describes the methane part of the process for making graphene membranes:

To make graphene for the membrane, the researchers flowed methane through a tube furnace at 1,000 degrees C over a copper foil that catalyzed its decomposition into carbon and hydrogen. The chemical vapor deposited carbon atoms that self-assembled into adjoining hexagons to form a sheet one atom thick.

That was the easy part. The next step involved putting the graphene sheet on a chip of silicon nitride, and exposing it to an oxygen plasma in order to force out selected carbon atoms. That left a hole or pore in the sheet.

The team was able to tune the number and size of the pores by varying the length of time that the carbon sheet was exposed to the plasma.

That’s a whole story in itself. To calculate the most effective pore size, the team went over to a shared science user facility at Oak Ridge called the Center for Nanophase Materials Sciences, and asked to borrow their scanning transmission electron microscopy (STEM) gear.

STEM provided the team with an atom-scale image of their graphene sheet, which they used to correlate porosity with its transport properties. That enabled them to calculate the optimal pore size, and distribution level, for desalination.

In case you’d like to try this at home, that would be pores in the range of 0.5 – 1 nanometers across, distributed at a rate of one per 100 square nanometers.

The topmost image in this article shows the red graphene membrane stabilized with yellow silicon atoms. The circular figure is an enlargement to show off the honeycomb structure. Ignore the orange areas — those are residual blotches of a polymer.

Just What The World Needs: A Methane Based Graphene Desalination Membrane — No, Really

So far the graphene desalination membrane has passed its tests with flying colors, achieving almost 100 percent rejection of salt ions while allowing water to flow through at a rapid pace.

To ice the cake, according to Oak Ridge the methane-based fabrication method could be scaled up to a commercial level.

That’s not such great news when you factor in the rapid increase in environmental, public health and quality-of-life baggage carried by oil and gas fracking operations. In the US, for example, fracking (short for hydrofracturing) was practically a non-issue when it was confined to thinly populated areas in western regions, but in recent years it has exploded into more heavily populated areas as the result of new shale discoveries.

The use of methane in water purification particularly ironic, given that one of the major issues in natural gas fracking is water contamination from both fracking fluid and fracking wastewater disposal.

On the other hand, when you consider the growth of methane-rich, renewable biogas sources, perhaps some day in the sparkling green future that super-efficient graphene desalination membrane can trace its roots to your friendly neighborhood hog farm.

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Image Credits: Courtesy of Oak Ridge National Laboratory.


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About the Author

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. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.



  • Jonathan Fosdick

    “In case you’d like to try this at home” Lol!

    That made me laugh, and although it was said as a joke I thought for a minute how this could be done at home – and not in a multi-billion dollar National laboratory.

    Microwave ovens can create carbon plasma by using a gas flow of CO2 passing near the magnetron’s aperture at a safe distance of a few inches, but I fear who would dare to use O2 gas intstead! It could result in a giant fireball and explosion! Unless I had a lab with Halon fire extinguishers installed across the ceilings and walls, I would not try making oxygen plasma using a kitchen microwave. Then again there is the problem of fine-tuning the monolayer sheet of graphene’s exposure to the oxygen plasma to achieve the optimum pore size and density.

    Without a STEM or AFM, it would take ages to meticulously measure the sheet’s permeability with a constant flow of water (under precise pressure) and one would need to have the ability to measure even the minutest trace of any salt ions that could pass through if the pores were larger than 1nm.

    Unless you are a analytical chemist by trade, or a plasma physicist, I can’t imagine this could be done at home. Still, it made me chuckle thinking some reader out there possibly thought, “Hey, I want to try this at home!”

  • Rich Persoff

    Seems to me no matter how thin the membrane, or what it’s made of, the same amount of energy will be required to separate the sodium and chlorine ions from the water molecules. A better technology sinks the membranes deep in the oceans so that the pressure forces the water through the membrane. the sea water Then all one has to do is pump it to the surface.

  • huehuehe

    Fracking? Are you serious? What’s next, you’re gonna make an article about pantyhose and on the part that says they’re petroleum-based products you’re gonna bring up oil spills?

  • Rajeev Gupta

    WHEN WE USE THIS TYPE OF MEMBRANE IN WASTE TREATMENT

    • Bob_Wallace

      No all-caps, please.

  • omar

    Tina:

    Yesterday i found a press release on arabic journal saying that stamford bridge university have made a battery from alluminium that can rcharge in one minute and have 7000 cycle with solid electrolite. but they didnt provide more technical details and i didnt see this on your site here. do you have any thing about this ?

  • mikgigs

    The article was good until the Author jumped the shark with the methane :). What a bad twist of turn 🙂 how the graphene production is scaled to use of natural gas(methane) for other purposes- heating, electricity, plastic production? should be a fraction of tenth or hundreth of percent. Is that really true, that methane(a natural gas) could contaminate water!?! it would be interesting to compare fracking contamination to a coal mining water contamination, before scared in so bold font way. AWFUL.

  • Kyle

    Awesome. I wish stories like this would be told to the public via the media.

  • The way described seems to be the answer for manufacturing the graphene but it’s doesn’t seem to be an issue with the environment. How much of the membrane would needed to be created wouldn’t even compare to what 1 city uses in a day.

    I think discovering the properties of graphene are groundbreaking and will even reshape the world of electronics.

  • Jason hm

    Big aside but I dont’t really think Geim and Novoselov where the first to dicover or isolate Graphene. Why? because defense technology and the material studies funded by defense funds have been all over Carbon and it’s derivatives ever since ww2. Look at this from wiki on Radar absorbing materials.

    “The earliest forms of RAM were the materials called Sumpf and Schornsteinfeger, a coating used by the German navy during World War II for the snorkels (or periscopes) of submarines, to lower their reflectivity in the 20-cm radar band the Allies used. The material had a layered structure and was based on graphite particles and other semiconductive materials embedded in a rubber matrix. The material’s efficiency was partially reduced by the action of sea water.[1][2]

    “Germany also pioneered the first aircraft to use Radar absorbing materials during World War II in the form of the Horten Ho 229.
    It used a carbon-impregnated plywood that would have made it very
    stealthy to Britain’s primitive radar of the time. It is unknown if the
    carbon was incorporated for stealth reasons or because of Germany’s
    metal shortage.[3]”

    Yeah know ever since ww2 our military must of been all over carbon and it’s unique properties in regards to Radar signatures. Heck Graphene is probable the major component of the stealth tech secrete formula. We where probable making this stuff by the barrel back in the 1970’s, possible even earlier.

  • TinaCasey

    As always thank you all for another lively conversation. The winner in the race to the marketplace will be least expensive, most reliable fabrication method for turning out high quality graphene products. Regardless of Lockheed Martin’s patents, they’re going to have to watch their backs as new research evolves.

    Some of you brought up the point that only a minor amount of graphene (and therefore, methane) would be needed for the global desalination industry. Considering the many uses for graphene outside of desalination membranes, a methane-based production method will eventually open up a can of worms — though that doesn’t necessarily have to happen, considering renewable methane sources as well as alternative fabrication methods.

  • spec9

    We here in California are eagerly awaiting more information and an affordable commercial version. 🙂

    • Joseph Dubeau

      It’s no joke. Roy just posted an article.

  • Marion Meads

    Tina here did not do her research well enough, nor the Oak Ridge Team. They are bound to lose their millions of dollars and wasted Tina’s and other people’s time here.

    That is because you haven’t been listening to me, the smarter one of you guys when it comes to these things. For more than a year now, I have been yakking about Lockheed Martin’s already patented graphene membrane and they call it perforene.

    Sorry folks, all of you should bow down to my super sharp memory, especially about many game changing technologies.

    http://www.businessinsider.com/lockheed-martin-desalination-graphene-filters-2013-3

    As to the Oak Ridge Team, all your efforts are in vain, you are still talking about building prototypes while Lockheed Martin has been granted the patent already.

    And this excellent energy efficient desalination membrane has been a couple of years old!!!

    My golly people!

    • Marion Meads

      To show the Oak Ridge Team and you people that this is really old technology news that you have no memory of, this has been plastered everywhere and I can’t believe no one has remembered!

      http://www.greenprophet.com/2014/12/graphene-nanotechnology-makes-desalination-100-times-more-efficient/

      http://seekingalpha.com/article/2350985-lockheed-martins-newest-innovation-isnt-what-you-expect

      http://www.desalination.com/wdr/50/9/graphene-membrane-technology-update

    • Philip W

      If you’re so damn smart, why aren’t you a billionaire yet?
      Oh yeah right, you’re not that as smart as you might think…

      Take down that pink mirror, Marion.

      • Michael G

        That expression “if you’re so smart, why ain’t ya rich?” has been around for-ev-ah. One ancient Greek philosopher got tired of hearing it so after the olive oil had been pressed from one harvest year he quietly went around and bought up all the olive presses. The next harvest year you HAD to buy from him if you wanted to make olive oil (a huge export product for classical Greece). He became very, very rich. So be careful, Marion may set one of her posse after you.

        • Philip W

          Yeah that expression is more rethorical I guess.
          But she wrote that she is smarter than all the other people here, how cocky is that?

          If she is the same in real life like she is here, I certainly wouldn’t want to be around her.

          P.S.: She would have to send her posse to Germany.

          • MarTams

            The context was defined. It was about advances in the desalination technology. If she were smart like politicians she would already be a trillionaire and wont spend a nanosecond of her time here torturing us mere mortals.

    • Joseph Dubeau

      Marion, you seem to get caught up on these article of Tina’s.
      There are just research reports. I usually read about them on Science Daily before I see them here. I know we all like science, right!
      Desalination with nanoporous graphene membrane
      http://www.sciencedaily.com/releases/2015/03/150325210330.htm
      This stuff is year away from being commercialized.

      Off topic.
      If you are interested DYI, there is Robert Murray-Smith on youtube who show you how make graphene at home.
      Here he is making Ultrasand – water desalination and purification using graphene coated sand
      https://www.youtube.com/watch?v=NbbQfu_VaHk

      • Babam

        Marina n has an excellent point! The technology has been patented and it is beyond research. So judge for yourself who’s being the smart ass here.

      • MarTams

        Will have to side with Marion here. Lockheed-Martin has all the patents cornered using graphene as RO membrane and has the technology for licensing. Which part of it you don’t understand? The research are now useless. How can you make a rebuttal when the patent has been approved for a company that has an army of IP attorneys?

        • Bob_Wallace

          Can you patent graphene membranes or only the process for turning graphene into a membrane?

          • MarTams

            Bob, it takes a few keystrokes to inquire of such thing in Google Patents search engine. You should have read the articles in the link but you didn’t. Shame on laziness, you want to be spoonfed? I have read those old links. Patent office publications are public.

          • Bob_Wallace

            Yes, I do want to be spoon fed from time to time.

            I spend hours every day passing on information to others. I don’t have time to read every link in every article. I wouldn’t mind being on the receiving end of the spoon once in awhile.

            Show your TopCom some love….

        • Joseph Dubeau

          You made that up. They don’t own graphene or holes in graphene or any small defects that may useful.

          • MarTams

            The primary news in this article is to use graphene as an efficient desalination RO membrane and that has been patented by Lockheed-Martin already. So the Oak Ridge Team is dead for such an application and therefore voiding this article. If it is about a new method of making graphene from methane, and it has not been patented, then the article should be revised. As it is the Oak Ridge Team is already bankrupt if they did not read about the desalination patent.

          • Bob_Wallace

            Again. Can you patent materials?

            If you can then why doesn’t some company own the patent for glass in windows? Or plastic for cell phones?

          • Ronald Brakels

            Technically the way it is supposed to work is only a process to make materials can be patented and not materials themselves, but in practice the US patent office has become a farce and anything can be patented from corners to the concept of clicking on something once instead of twice. It’s so bad that technological development in the United States would probably be improved if the patent system was abolished.

            Of course the best solution would be to put things back the way they used to be a few hundred years ago, but why do things by halves? What’s the fun in that?

          • stuart21

            new, useful, unobvious materials; Yes.

          • Joseph Dubeau

            So what you are saying our federal funded Oak Ridge National Laboratory is reverse engineering the intelligently property held by a private company? And in turn publishing this research as their own so that a reporter like Tina can write article for us to read for our entertainment.

            Well then, that’s brilliant.

          • Offgridman

            With all of the billions invested at Oak Ridge it would seem that some of it is used for a patent attorney and research people, it is not a small operation by any means. Even if Lockheed has made a desalination filter from graphene there is no reason someone else can’t by using a different process. If in the end there is some type of infringement Lockheed can receive a residual if the Oak Ridge process works out to be more economically viable on the commercial scale.
            Y’all are using toothpicks to bat at basketballs to think that they haven’t considered this aspect and will go bankrupt over it.

    • Offgridman

      Marion, you may be very good at remembering product announcements, but you have a very poor understanding of patent law. It doesn’t matter if Lockheed has come out with a carbon based membrane already, because if the Oak Ridge process for making it is just slightly different and includes or excludes a few molecules it is patentable.
      Lots of companies sell similar products, so long as they are made in a slightly different way, no patent hassles. Just look at solar panels for a prime example. How many different companies are making monocrystalline ones?

  • Tina is the best. If you’re a defense contractor and run secrete extraordinary rendition services for the CIA and Army, Tina is your PR person.

    Jumping from methane to desalination is kind of a weird jump. RO media already uses methane and ethane as feedstock in manufacturing. Polyesters and whatnots for example.

    Graphene based RO still needs prefiltration just like it does now. The major cost is pumping, but that can be optimized with efficiency measures and solar power to drive pumps.

    Having to get seawater ready to pass through extremely expensive filtering/exchange media will become more and more difficult as water temperatures raise in shallow areas where intakes are typically located. One of the biggest problems with RO is bacteria growth. The hydrocarbon based media makes a perfect biofilm.

    • Bob_Wallace

      “If you’re a defense contractor and run secrete extraordinary rendition services for the CIA and Army, Tina is your PR person”

      Dial it back, please. Tina pays attention to what the US military is doing and the US military is an early adopter and developer of some things that are good for the planet.

      • So it’s true about cleantechnica and its “client” relationships? Some pretty shady stuff. The only reason the US Military is an early adopter of technology, green or military wise, is it has never been told no to getting money to early adapt. Tying in clean technology sales with everlasting war is not very pleasing.

        • Shane 2

          Michael, the military is involved in cleantech so it is reportable here and no amount of bleating from you is going to change that. If you don’t like reporting of cleantech developments by the military or companies with defence contracts go and bleat on an anti-military website. Go away troll.

        • Bob_Wallace

          BS, Michael.

          Cleantechnica does run a sponsored article from time to time. And those articles are 1) deemed honest/informative and 2) clearly identified.

          The US does have extremely generous funding which has allowed it to do research in areas which aren’t well funded by other departments. Take self-driving cars. That’s a DARPA spin-off.

          If everlasting wars is your concern, the US military does not start wars. US wars, as with wars everywhere, are started by politicians. Focus your concern on the workman, not his tools.

          • rockyredneck

            The U.S. military may not start wars, but between them and politicians they make a lot of wars their own.

          • Bob_Wallace

            Yes, once sent in they do want to win. But I can’t think of any wars started by armies and not political leaders. Uprisings/coups excepted.

          • rockyredneck

            Many political leaders are military or ex military. The mindset seems to be (if we can win, fight, if we can’t, negotiate.)
            Worked for me in school too.

      • Marion Meads

        I can’t believe that Bob has no recollection about the perforene for desalination, already patented by Lockheed Martin, and have told Bob about this for a long time now!

        Too bad, it is already patented, the Oak Ridge Team has just wasted millions of dollars for nothing!

        http://lockheedmartin.com/content/dam/lockheed/data/ms2/documents/Perforene-datasheet.pdf

        • Marion, do you work for Lockheed? You seem a bit too enthusiastic. Who cares if its DoD or DoE. Or Lockheed Martin or Battelle/Bechtel (whoever is running Oak Ridge). It’s all government money anyway.

        • Bob_Wallace

          You can’t believe I have no recollection about something?

          Lord, woman, you certainly don’t know me. I have the memory of a bucket full of rust holes.

    • Shane 2

      Michael Berndtson ***If you’re a defense contractor and run secrete extraordinary rendition services for the CIA and Army, Tina is your PR person.***
      Get lost troll. The military works on cleantech and that is reportable here. Trying to tie Tina to rendition is just an indication that you are a loathsome troll.

      • What if say a black sites are solar powered? Is that reportable. Say somewhere in Eastern Europe?

        You do know that its all government work, right?

      • Bob_Wallace

        Turn up you chill dial a bit, please.

      • rockyredneck

        I often disagree with Michael, but most of his arguments are reasonable and considerate. I see no reason for calling him a troll.

  • Ronald Brakels

    A carbon atom takes up an area about one tenth of a nanometer across in graphene. There are around 10 to the 24 carbon atoms in 200 grams of graphene. This means 200 grams of carbon could create about 100 square meters of graphene. There are 200 grams of carbon in 270 grams of methane. So a kilogram of methane could produce roughly 375 square meters of graphene which is an areas equal to one and a half tennis courts.

    • angry647

      “There are around 10 to 24 carbon atoms in 200 grams of graphene.” Wait… that would make 1 carbon atom weigh as much as 20 grams! I think your numbers might be off.

      • angry647

        And right after I posted that, I learned how to read and realized that you wrote “10 to the 24 carbon atoms…” So, I have just outed myself as a knucklehead. Sorry

        • Ronald Brakels

          It’s easy to miss a word. And perhaps I should learn how to type superscripts.

  • Michael G

    Normally I would expect a tech like this to take 20-30 years to get to market (if ever) but desalination is going to be increasingly important as global heating dries out (or submerges) more and more of our world. I hope this (or something like it) gets out in the next 10 years.

    We will be living with the after-effects of our self-destructive behavior for *at least* 100 years even if we stopped all GHG emissions now (whch ain’t happenin’).

    Living in CA I see the incredible human reaction to this. Half the neighbors are putting in native CA drought-tolerant plants to conserve water and provide habitat for native species of birds, bugs, etc. but the other half get defensive and say “there’s plenty of water if (some other guy) would stop wasting it on (whatever)”.

  • JamesWimberley

    For heaven’s sake. What does the use of methane in an experimental industrial process have to do with the climate impacts of large-scale natural gas? Suppose the process is successful and goes into commercial production, You would be talking of a few thousand tonnes a year, noise in the gas burning statistics.

    Nothing is nature is good or bad by itself, though guinea worms and HIV stretch the case. It’s what humans make of nature.

    • Shane 2

      ***For heaven’s sake. What does the use of methane in an experimental industrial process have to do with the climate impacts of large-scale natural gas?***
      We have a winner. People need to get a sense of proportion. Even if this process becomes commonplace, we are talking about nanometer thin membranes. This is not going to require anything but a tiny proportion of the methane currently extracted from the ground. Methane is easily obtained from anaerobic digestion of biomass such as algae if you insist on a solar sources. The major cost of this process will not the cost of the methane. It will be the cost of the specialised molecular manipulation. All the handwringing about fracking is a irrelevant to this story.

      • Offgridman

        Yes to much was made of the use of methane when we already have many non fossil fuel sources for it. What I got wondering about was the need for the high temperature furnace and then the plasma deposition process in order to make the membrane. In some cases the high energy use to produce the membrane may be worthwhile. But in many places if we could just quit wasting our fresh water supplies (like for fracking, or inefficient farming methods), and stop the pollution of the sources that we have the need for desalination would become irrelevant.

      • Mint

        As another example of people lacking proportion, consider just regular reverse osmosis powered by a natural gas plant using fracked gas.
        http://belfercenter.ksg.harvard.edu/files/ETIP-DP-2010-15-final-4.pdf

        “the water consumption for the production of shale gas appears to be lower (0.6 to 1.8 gal/MMBtu) than that for other fossil fuels (1 to 8 gal/MMBtu for coal mining and washing, and 1 to 62 gal/MMBtu for U.S. onshore oil production).”
        1 MMBtu of gas can generate up to 170 kWh of electricity, and 1kWh can desalinate 80 gallons of water.

      • Nick Girard

        The efficiency savings would be massive and perhaps offset the extraction. Carbon nanotubes will revolutionize everything. Imagine a substance as strong as diamond with electrical perfection that can hold extremely high charges and can also be paper thin. The plane would be very light, humans and luggage would be the heavy parts.

      • Frank

        We could get the methane from cow flatulence!

        The tech sounds cool.

  • Ronald Brakels

    Well they could probably use hydrogen cyanide instead of methane. That’s what used to be used to poison harpoons to kill whales. Unfortunately, besides being really toxic, it’s made from methane. Hmm… How about just heat a piece of charcoal up to 3,700 degrees to vapourise it? That should do the trick. We can get a flame that hot by burning cyanogen, another really toxic cyanide compound in pure oxygen.

  • Anders Hove

    Without knowing how much methane is needed per unit of membrane, or how much per unit of H2O created by the membrane over its lifetime, it’s hard to evaluate whether this has any relevance to the fracking debate. As the article points out, methane comes from a variety of sources, not just fracking, and there’s no rule that says the membranes are best made in the U.S. Maybe Qatar or Nigeria would be best? Without more info, hard to know.

    • Angus2100

      The fact that it’s only one atom thick shows how little methane would be needed per unit area.

  • Radical Ignorant

    How much this membranes could be build? 100k tonnes to filter whole water in the world? How much methane you need for that?

    • Michael G

      Since the methane is only used to form the graphene, perhaps another method of making graphene (which is just carbon) could be used. It is still in early stages of research so we can hope for and expect a lot of improvements.

      • William Edstrom

        It’s ridiculous that methane’s relation to fracking and global warming was mentioned. The methane in those situations is geologic in scale. We are talking about BILLIONS of times less for a process like this. In any case, it’s carbon/greenhouse gase neutral because it’s a net energy saver.

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