Forgot your password?
typodupeerror
Science

Graphene Membranes Superpermeable to Water 292

Posted by Soulskill
from the it-slices-it-dices dept.
Dr Max writes "Not only is graphene the strongest, thinnest and best conducting material known to man, it is now shown to have superpermeability with respect to water as well. This allows a membrane made with graphene to pass water right through it (PDF), while another atom or molecule (even helium) gets blocked. 'The properties are so unusual that it is hard to imagine that they cannot find some use in the design of filtration, separation or barrier membranes and for selective removal of water,' said one of the researchers."
This discussion has been archived. No new comments can be posted.

Graphene Membranes Superpermeable to Water

Comments Filter:
  • Does this mean... (Score:2, Insightful)

    by Anonymous Coward

    ...you don't need a pressure source like you do for reverse osmosis?

    • by imboboage0 (876812) <imboboage0@gmail.com> on Friday January 27, 2012 @11:20AM (#38839591) Homepage
      After reading the second article, I'm not sure. I didn't read in detail, but they did some experiments with a pump. I'm not sure if it's required, but that is how they did it to research it.
      • by Tsingi (870990)

        After reading the second article, I'm not sure. I didn't read in detail, but they did some experiments with a pump. I'm not sure if it's required, but that is how they did it to research it.

        Even sub um thick membranes were strong enough to withstand a differential pressure P up to 100 mbar.

      • by msheekhah (903443)
        Can we use this for desalination? That would be epic.
    • Re:Does this mean... (Score:5, Informative)

      by The Grim Reefer (1162755) on Friday January 27, 2012 @11:31AM (#38839713)

      ...you don't need a pressure source like you do for reverse osmosis?

      Even if it does not, I would think it would be much more resilient toward chlorine and iron. Perhaps it won't need as much pretreatment done to the water as a conventional film membrane requires. Currently most decent RO systems have a 10 micron sediment filter, followed by 5 and 1 micron carbon filters. If you have high iron content in the feed water, then you need a softener or some other way to reduce it prior to the sediment filter too. Since the three RO pre-filters typically need to be replaced every 6-12 months, they are the most frequent replacement item. A typical RO membrane last 2-5 years. Perhaps this would be lengthened too.

    • by trout007 (975317)

      There has also been studies showing you can make a selective filter by making nanotubes with the right diameter to let water through but not larger molecules. In addition because the walls are so "smooth" there is much less pressure to flow the water through then expected.

      • by chill (34294) on Friday January 27, 2012 @12:05PM (#38840129) Journal

        Yes, but here they're showing that the membrane allows WATER through but will stop HELIUM. If I'm not mistaken, helium molecules are smallerthan water molecules. That's the freakish quality.

        • I don't really know, but I'd suspect that it has something to do with like,electrical charge or something, not size - e.g. they're both small enough to fit through, but the helium experiences some sort of repulsive force which the water does not as it passes through the field created by the graphene.

          • by geekoid (135745)

            If only they had an article you cold read that tells you how it works.

          • by tbird81 (946205)

            This is what they said:
            "In conclusion, unimpeded evaporation of water through Heleaktight membranes sounds next to impossible. The closest analogy is probably the permeation of protons (atomic hydrogen) through thin films of transition metals, the phenomenon known as superpermeability. To explain our experiments, we propose the model that can be summarized as follows. GO laminates contain 2D capillaries that, under ambient conditions, are filled with an ordered monolayer of water. A capillarylike pressure p

        • by Dr Max (1696200)
          Exactly. Which doubles it's uses not only as a water filter but as a strong light weight container for almost anything. I'm thinking Airships that don't need re-filling and light weight gas tanks for fuel cells.
        • One of the problems with a "hydrogen economy" is storage as hydrogen leaks out of pretty much everything.

          Wonder how well this blocks it.

          • Re:Hydrogen (Score:4, Informative)

            by Patch86 (1465427) on Friday January 27, 2012 @03:14PM (#38843335)

            According to TFA (well, the BBC article on the same subject, anyway) it blocks helium molecules with what appears to be 100% efficiency. Helium molecules are smaller than the molecules in a standing mass of hydrogen, since hydrogen atoms bond together to form H2.

        • Helium (Score:4, Informative)

          by TuringCheck (1989202) on Friday January 27, 2012 @01:47PM (#38841801)
          Actually the helium atom is the smallest possible molecule. The hidrogen atom is smaller but it forms H2 molecules which are much larger than a single atom, even if much lighter.

          Gaseous helium difuses through pretty much everything. These graphene membranes should have truly amazing properties.

          Armies of physicists will work years to explain such remarkable phenomenons. Neutrinos light than faster like just.

      • Re:Does this mean... (Score:4, Informative)

        by slew (2918) on Friday January 27, 2012 @12:33PM (#38840465)

        There has also been studies showing you can make a selective filter by making nanotubes with the right diameter to let water through but not larger molecules. In addition because the walls are so "smooth" there is much less pressure to flow the water through then expected.

        Although I doubt this orientation will allow for filtering out "helium" as the original posting.

        The mechanims that the original posting paper is speculating, it that the way they made the graphene oxide (not pure graphene) membrane, it is has embedded capilaries which when wet (filled with water) allow for nearly unimpeded transport of water, but when these capilaries dry out, their diameter constricts so that nothing gets through (even helium).

        So to contrast, the "tubes" are not rigid and the walls are not so "smooth" in this case, the "tubes" are sort of like chinese finger puzzles. When filled with water, allow water to pass easily, but when you try to pull the last bit of water out of them, the diameter constricts and nothing can get past.. Well maybe the chinese finger puzzle analogy was a bad one, but I couldn't think of anything else...

    • by X0563511 (793323)

      Could you not use gravity? I have a filter on my counter that does just that.

      • Re: (Score:3, Insightful)

        by Anonymous Coward

        You're using energy to get that water higher than it's final location, just like a pump.

        • by jasno (124830)

          Yeah but you could use tidal action... Sure, it limits the rate of clean water, but it's free.

          Hell, if you had a cistern below sea-level then gravity would do the work for you - you'd only expend energy to pump up the water. Humans are used to that, so it's really like having free groundwater.

    • by Cyberax (705495)

      You do, of course. Otherwise you'll be able to create a perpetum mobile by using this membrane to filter out pure water and then using pure water to dilute brine (it produces energy) on the other side of the membrane.

      • I did design a perpetual motion machine involving a really deep tube in the ocean with a RO membrane at the bottom, exploiting the slight density difference between fresh and salt water to produce the required pressure. I know it can't work, because if it did it would be producing energy from nothing, but I still can't figure out exactly why it wouldn't work.
        • by Grishnakh (216268)

          I wonder if that's one of those things that really would work, but not because it's perpetual motion, but instead because it's taking energy out of the system that's already there. For instance, look at wind power: just stick up a windmill in a windy place and you get free energy. Except that's not quite free: there's energy in the atmosphere, which is causing this wind, so your windmill is removing (a very small amount of) energy from the atmosphere and converting it to electricity. It works ok because

        • by HiThere (15173)

          That's not a forbidden class of perpetual motion machine. It ultimately gets it's energy from the sun. And you are quite limited in the amount of energy that you can extract that way. I've never designed one, but there are a few analogous systems that are (or were, before solar power got cheaper) operating on remote islands. They were all test systems and none of them was cost effective, but that's more a design and materials problem than anything basic.

          IIRC there was one system that cost several thousa

    • The laws of physics are rather strict on this account: You must, absolutly must, have a pressure source or some form of energy input. You can get energy out when you dilute a solution, and must put energy in to seperate them. It is possible it'll be more efficient though, so you don't need as much pressu.re
  • by geekopus (130194) <geekopus@[ ]oo.com ['yah' in gap]> on Friday January 27, 2012 @11:21AM (#38839603)

    Now we know what the water receptacles in Dune were made of.

  • Super desalination? (Score:5, Interesting)

    by Draconi (38078) on Friday January 27, 2012 @11:22AM (#38839607)

    Press and squeeze a hydraulic press of water through a few layers of graphene = no more salty water?

    • by felipekk (1007591)

      Better yet, no more polluted water!

      • Plus we can sell the harvested toxic waste to Hormel, or Hollywood, or Congress, or somebody.

      • Re: (Score:2, Informative)

        by Adriax (746043)

        Water so completely pure you'd have to introduce contaminants just to make it safe to drink.
        http://en.wikipedia.org/wiki/Water_intoxication [wikipedia.org]

        • by Chuckstar (799005)

          You won't get water intoxication merely by drinking pure water. Regular drinking water contains such low proportions of minerals that, from a physiological perspective, drinking water is effectively pure water. The main problem with pure water is that it doesn't taste "right". If you've ever tried drinking distilled water... yuck.

          • by gman003 (1693318)

            At the very least, it could be used for agriculture. Plants don't exactly care how water tastes. It could probably be used in soft drinks as well. Plus making cooling water that doesn't corrode stuff or build up residue - I can imagine this being used in nuclear reactors.

            If it really is as simple as "run water through graphene sheets, get 100% pure hydrogen oxide", there's no limit to how many places it could be used.

          • You're right, but details are needed.

            Water intoxication can happen with either tap water or ultrapure water.

            If you add hydration you need to add electrolytes or your system goes out of balance. Your body can handle only so much imbalance. As it goes too far out of whack, that's effectively water intoxication.

            Drinking a glass of ultrapure probably won't hurt you, nor a glass of tap. But have a bunch of either in a short period and you will have a problem. Read the Wikipedia water intoxication article's "

        • Re: (Score:3, Informative)

          Please, stop spreading the FUD. Regular tap water can just as well cause water intoxication if you drink too much of it, and ultra-pure water is by no means unsafe to drink.

    • by Tim4444 (1122173)

      I understand that one of the current problems with desalination filtering is that the salt left behind clogs up the filter fairly quickly. Hopefully researchers will test to know for sure, but this may well suffer from the same problem. The other problem is that the water wants to be with the salt - ie. it's an energetically stable state. You have to put in some energy (usually via pressure) to get it through a filter and away from the salt. Compare that to simply filtering out fine particulates that might

  • Fresh water? (Score:5, Insightful)

    by gmuslera (3436) * on Friday January 27, 2012 @11:23AM (#38839615) Homepage Journal
    So you could pass thru i.e. ocean or contaminated water and get fresh, drinkable, pure water on the other side? If that could scale could be great.
    • by trout007 (975317)

      Or you could mine salt by dragging a net of graphene behind a boat.

    • Re: (Score:2, Interesting)

      by CastrTroy (595695)
      If it's really only letting water through, you'd still have to add minerals in at the other end. Last I checked, drinking distilled pure water is probably as bad as drinking salt water.. With salt water your body accumulates too much salt. With distilled water. all the minerals (that your body needs to function) get picked up by the water. However it it works well, it would be simple to add minerals back in after everything had been extracted.
      • Re:Fresh water? (Score:4, Insightful)

        by cunniff (264218) on Friday January 27, 2012 @11:58AM (#38840035) Homepage

        Spend a little time thinking about it, and you will realize that distilled water urban legend is silly. In your mouth, it is mixed with saliva and mucous and whatever else is stuck to your teeth, gums, and tongue. The instant it hits your stomach, it is mixed with stomach acids and whatever you ate recently. I.e. it is no longer pure distilled water. From there, the molecules wander through your body like any other water molecule. Distilling water does not give its component molecules magic properties.

        • by Baloroth (2370816)
          The problem, I think, is if you only drink distilled water, the electrolytes and minerals that leave your system in urine aren't being replaced as fast as they are when you drink tap water. Sure, you'll get some from food, but much less than normal. This could be a major issue, especially if you are drinking a lot of water. I.e. drinking a lot of distilled water could result in electrolyte depletion that would not happen with tap water. But this is probably something very few people will ever be in danger o
      • by Joce640k (829181)

        Last I checked, drinking distilled pure water is probably as bad as drinking salt water.

        Where did you 'check' that? Maybe you need better sources.

        There's loads of people out there who drink nothing but distilled water believing it's healthier - Google "home water distiller" for proof.

    • Re: (Score:3, Interesting)

      by WebSorcerer (889656)

      I'm a Ph.D. Chemist who has done some water purification studies. One difficulty is the build-up of particulate matter on/in the filter which slows down (eventually stops) flow through the filter.

      This problem can be addressed with the use of two filters in parallel, one of which is being back-flushed while the other operates. With the current types of filters, the system eventually plugs due to micro particulates. Perhaps this Graphine filter is immune to plugging, and merely flushing the surface will cl

  • by tverbeek (457094) on Friday January 27, 2012 @11:25AM (#38839641) Homepage

    But can it be used as a dessert topping?

  • Important detail (Score:5, Informative)

    by zAPPzAPP (1207370) on Friday January 27, 2012 @11:25AM (#38839643)

    It's not mentioned in the opener, but the article says it lets water "evaporate" through it.
    So it's not like you can just pour water on it, and let it drip through.

    I wonder if this just means steam can pass through it, or if it has to evaporate on the graphene for it to get through?
    If it was the former, then why are they wording it so complicated?

    • by Joce640k (829181)

      It's not mentioned in the opener, but the article says it lets water "evaporate" through it.
      So it's not like you can just pour water on it, and let it drip through.

      It says they sealed some water containers with graphene and the water evaporated as if the graphene wasn't there. They didn't heat/boil the tubes, they just let them stand for several days.

      It doesn't say what happens if you pour water on it. It might drip...maybe they're waiting for more funding so they can perform such a complex experiment.

  • by THE_WELL_HUNG_OYSTER (2473494) on Friday January 27, 2012 @11:28AM (#38839679)
    The material they used was NOT graphene. It was graphene oxide.
  • by tomhath (637240) on Friday January 27, 2012 @11:30AM (#38839695)

    graphene-based membranes are impermeable to all gases and liquids (vacuum-tight). However, water evaporates through them as quickly as if the membranes were not there at all.

    Thanks for clarifying that. Anyway, this is a very amazing material.

  • by swb (14022) on Friday January 27, 2012 @11:35AM (#38839777)

    Lets all the delicious moisture through, blocks the stuff you want blocked???

  • What about the Water Memory [wikipedia.org]? Does this membrane erase all this information or is a there a mechanism to determine which information to be deleted? Would be an invaluable Material for all that homeopathy stuff...
    • by Tassidus (2562187)
      Seems a bit weird to respond to a scientific discussion, with scientific proof and evidence, with an article that says "No scientific evidence supports this claim". It's equivalent to sitting in an evolution debate and proposing the idea of creationism. :-p
    • by Pope (17780)

      What about the Water Memory [wikipedia.org]? Does this membrane erase all this information or is a there a mechanism to determine which information to be deleted? Would be an invaluable Material for all that homeopathy stuff...

      Are you clinically retarded?

    • by Dishevel (1105119)

      Water has no memory. You are being lied to so people can make money off you.
      If you want cheap homeopathic results just drink tap water and believe it is fixing you.
      With the proper belief you will get the benefit of the placebo effect without paying extra and as a bonus you can believe that the water is doing a whole host of killer things for you.

  • by DickBreath (207180) on Friday January 27, 2012 @11:50AM (#38839933) Homepage
    If it blocks Helium this has very important applications.

    Helium molecules are very small. It is difficult to contain Helium gas in cylinders.

    There are even far more important applications for the global economy. It may finally be possible to make Helium balloons that don't leak the tiny molecules so quickly.
  • So if people can make exotic materials like graphene, why can't my doctor make my low back pain go away?
  • by PPH (736903)

    My kids' diapers.

  • Last pdf page:

    The fact that the water fills the 2D channel even under a negative pressure in the left reservoir indicates [...]

    I understand that sometime negative pressure means lower pressure than global/ambiant pressure.
    But here in this 2D atomistic simulation I don't know what they mean.

  • If this process were used in bootlegging, it would eliminate the still's heat signature. It would eliminate the still's distinctive sound. It might make it economical for many people to have their home stills in their garages. I see governmental regulation soon.

Take care of the luxuries and the necessities will take care of themselves. -- Lazarus Long

Working...