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Making Saltwater Drinkable With Graphene 303

Posted by samzenpus
from the water-water-everywhere dept.
An anonymous reader writes "Graphene once again proves that it is quite possibly the most miraculous material known to man, this time by making saltwater drinkable. The process was developed by a group of MIT researchers who realized that graphene allowed for the creation of an incredibly precise sieve. Basically, the regular atomic structure of graphene means that you can create holes of any size, for example the size of a single molecule of water. Using this process scientist can desalinate saltwater 1,000 times faster than the Reverse Osmosis technique."
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Making Saltwater Drinkable With Graphene

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  • A foul subject. (Score:5, Interesting)

    by Anonymous Coward on Sunday July 01, 2012 @11:43AM (#40510717)

    So how durable is this membrane when it comes to dealing with impurities?

    • Re:A foul subject. (Score:5, Informative)

      by Anonymous Coward on Sunday July 01, 2012 @11:54AM (#40510759)

      Graphene membranes are highly durable. The main problem would be clearing the inlet side of the filter from the buildup of blocked particles.

      Prevous Slashdot article here: http://science.slashdot.org/story/12/01/27/1354240/graphene-membranes-superpermeable-to-water

      http://www.manchester.ac.uk/research/news/display/?id=7895

      http://arxiv.org/ftp/arxiv/papers/1112/1112.3488.pdf

      • Re: (Score:3, Insightful)

        Well assume they can reverse-flush it on a regular basis and that it won't collapse that way, either.

      • by theshowmecanuck (703852) on Sunday July 01, 2012 @07:48PM (#40513131) Journal

        RO is not like using a traditional filter. I'll see if I can explain it quickly without the explanation getting too muddy. The last RO project I worked on was in 1990 (and wasn't for salt, but same principles apply), but I doubt the basic structure of the equipment has changed much. Probably more changes are in the actual membranes.

        On an industrial scale membranes are placed in canisters and usually in large banks of them. The way the canister is built is usually a couple of sheets of membrane, sandwiching a substrate that allows a reasonable liquid flow rate through it, the whole is then spiral wound (like a roll of paper towel), or better yet, like film on a film winder that goes into a film development tank for those who remember film cameras and how to develop negatives :). The edges of the substrate and membranes are attached to a framework such that the purified liquid can be collected and channelled out either one or both ends of the spiral assembly when the assembly is inserted into a properly designed tube/canister. You put the wound membrane assembly in the tube that has one inlet and two or three outlets (depending on whether you want the purified liquid outlets at either end or just one). So say we have one feed outlet and one purified outlet. On the inlet side you flow your feed liquid at high pressure. One of the two outlets is your "purified" liquid and the other is an outlet for feed liquid.

        Because of the pressure differential between the feed side of the membrane and the substrate side of it, the "pure" liquid will be forced through and then flow through the substrate and the pure liquid outlet (at a much, much lower flow rate than the pressurized feed liquid). On the feed side of the membrane, this results in a slightly higher concentration as it passes the membrane and thus, the feed outlet side has a higher concentration of solute than the inlet. But you are always maintaining a flow across the membrane at high pressure and what you end up with is the slightly higher concentration liquid flowing out the far end from the inlet. Note that the downstream line from the canister is still under pressure.

        So you don't really need to backflush to clean it, or not as often as you might think. You always have a flow of material over the surface in low enough concentration to keep the salt in solution. Granted that sometimes they will chain membrane canisters, the outlet from one going into the next. Or they may have a feedback loop that keeps a set (higher) concentration on the outlet. This reduces the inlet flow and increases the concentration of the output, but it also increases the pressure required. Regardless, the membrane is usually kept from clogging from the movement of the feed.

        FWIW, in some systems you might want a certain concentration on the outlet to use as feed for another process. You might be able to use it to concentrate sugars, or even the salt we're talking about. The more water you squeeze out, the less you need to evaporate. But in the case of desalination, I can think of cheaper ways to get salt (like mining), but this serves as an example of what can be done.

        For maintenance in some operations (like for example, in the food industry), once the system is shut down, they will run cleaners through the system and if it needs to stay shut down for a period, they'll fill the system with purified water (if water is the output they can use that). They might add a bacterial inhibitor so that nothing could possibly grow and build up in the system. If they don't keep the canisters full of liquid they will dry out and usually become useless. And they are quite expensive.

        Pure water is not always what is sought after. Lower pressure RO, usually called ultra filtration has various uses. For instance, I saw one project using it in making raspberry juice. Don't ask me what they were doing with it, I just saw it in passing at a food research place. I was seconded to a research institute in a past life to study using RO to purify waste

    • Re:A foul subject. (Score:5, Insightful)

      by Anonymous Coward on Sunday July 01, 2012 @11:58AM (#40510787)

      Surely it won't last forever, but the membrane lifetime could be extended by using normal filters to retain impurities, and let the graphene deal with pure saline water. Maybe the graphene filter can be cleaned a couple of times and be reutilized.

    • Re:A foul subject. (Score:5, Informative)

      by foniksonik (573572) on Sunday July 01, 2012 @12:35PM (#40511055) Homepage Journal

      http://www.wateronline.com/doc.mvc/nanoporous-graphene-could-outperform-best-commercial-water-desalination-techniques-0001 [wateronline.com]

      Article linked from summary links to the above article as a source.

    • Re:A foul subject. (Score:4, Informative)

      by marcosdumay (620877) <marcosdumay&gmail,com> on Sunday July 01, 2012 @12:41PM (#40511091) Homepage Journal

      Well, TFA brings absolutely no detail. It won't even let you know it it is about something produced in a lab, some theoretical contruction, or even if nobody has no idea how to create such a filter.

      Now, graphene is pretty stable. It probably cloges with time, as other athoms get in the place of carbon, but that is an incredibly slow process. A membrane composed of a single graphene sheet should last more than any other component of your plant.

      Ok, all the above is great, and etc. But when you get in the real world, membranes get old because of impurities that accumulate on its porous. A single graphene sheet has nowhere for those impurities to accumulate, if you reverse whash it, all impurities are gone (except for the mechanism at the above paragraph). But no practical membrane is composed of a single graphene sheet, thus, durability will be probably all over the scale depending on the quality of the actual membrane, from trash that can't be used on a lab to as good as ceramic filters.

      • Re:A foul subject. (Score:5, Informative)

        by manicb (1633645) on Sunday July 01, 2012 @02:38PM (#40511711)

        According to the other article [wateronline.com] people are posting, this is based on Molecular Dynamics simulations. MD is a theoretical technique that uses time-dependent Newtonian mechanics. It relies heavily on having good-quality data for the interactions between the atoms, but allows relatively large systems to be modelled. The wikipedia article [wikipedia.org] contains a fair bit of information (probably too much).

        TLDR: This is just based on computational modelling. The model is fairly crude, but is a standard technique for this scale of system and the results should be taken seriously.

  • "scientist" (Score:5, Funny)

    by Anonymous Coward on Sunday July 01, 2012 @11:44AM (#40510721)

    Using this process scientist can desalinate saltwater 1,000 times faster than the Reverse Osmosis technique.

    Well isn't that swell for 'scientist', but does scientist plan to share?

    • by axlr8or (889713) on Sunday July 01, 2012 @01:04PM (#40511231)
      Don't worry, they are meeting with Apple execs as we speak to save the world. It will be called, the iDsalter. The commerical will be giving a can of Redbull to an astronaut, and kicking him out the airlock of the ISS with a parachute and a pair of augmented reality googles, bluetooth paired to an iPad so he can watch ads all the way down while recording his POV.
      • Re: (Score:2, Insightful)

        by Anonymous Coward
        Wow. You have no sense of humor.

        Let's break down why you are unfunny.
        1. Starting with Apple execs, it's obvious you are trying to be funny, so hopefully the last half of the sentence will be funny. Oh but the punchline is "to save the world." Hmm, not funny at all.
        2. You try to recover from that bomb with the old Apple-prepending-i-for-all-their-products gag. But you wedge a D clumsily in there. Now, it's confirmed you've got nowhere to go but down, Dane Cook style with a completely unnecessary story that se
  • Holes? (Score:3, Insightful)

    by Anonymous Coward on Sunday July 01, 2012 @11:46AM (#40510731)

    what about the holes getting blocked by minerals and impurities? seems high maintenance job.

    • Re:Holes? (Score:4, Insightful)

      by PPH (736903) on Sunday July 01, 2012 @11:59AM (#40510797)
      Backflush?
    • Re:Holes? (Score:5, Interesting)

      by sam_handelman (519767) <{skh2003} {at} {columbia.edu}> on Sunday July 01, 2012 @12:05PM (#40510845) Homepage Journal

      A couple of people have raised this issue, and it relies on a fundamental mis-understanding of how the universe works on a molecular scale.

        Suppose that I have my colander and I wash some vegetables in it. Gunk can get stuck in the holes and it has to be washed off, which requires a fair amount of work because I have to break the interaction between the gunk and the surface. That's your macroscopic intuition about how filters and such work.

        But your macroscopic intuition will lead you astray in this case. The individual holes in graphene do not work that way; yes, occasionally, molecules of one kind or another will spend some time stuck to the graphene (a useful phenomenon in other circumstances - http://en.wikipedia.org/wiki/High-performance_liquid_chromatography [wikipedia.org]) but, on the scale of atoms, they are effectively in a high-powered washing machine ALL THE TIME.

        Can't find quite the movie I want... this'll do:
      http://protonsforbreakfast.wordpress.com/2012/04/11/brownian-motion-observed-in-milk/ [wordpress.com]

        So you see those oil bubbles wiggling around? Given that amount of constant wiggle, are you worried about having them "stuck" anywhere? That's thermal vibration from being at room temperature. Those milk bubbles are over 1,000 water molecules across, so each of those "wiggles" is 10 or 100 times the size of an individual graphene pore; are you worried about anything another 1000x smaller being "stuck" anywhere? It would be like worrying about gunk stuck in your colander while your colander was sitting in a fire-hose 24/7.

        Anyway- to cut to the chase:
      obviously you could have you take the graphene and you run the sea water *past* it at high pressure. Occasionally some gunk gets in there but it washes away sooner or later; and nothing spends any appreciable amount of time stuck in an individual graphene hole.

      • Re:Holes? (Score:5, Funny)

        by ffflala (793437) on Sunday July 01, 2012 @12:55PM (#40511171)

        Occasionally some gunk gets in there but it washes away sooner or later; and nothing spends any appreciable amount of time stuck in an individual graphene hole.

        She was a real hot-shooter, that bubble. I should have known she'd be trouble from the get go; she was naturally "charged" as they say when they're trying to be polite.

        With her bouncing around all over the place even at room temperature, I guess I should have seen it coming. But, as will happen to palookas and wishful thinkers, my hopes and processes got the best of me. I was convinced that any trouble would wash away as soon as it cropped She didn't even say goodbye, just left a note saying she'd thought she had found a solution with me, but couldn't stand the suspension and was afraid of becoming just another precipitate.

        That was three years ago. I took the tube directly to this here graphene hole; it was the closest one I could find. I've been stuck here ever since.

      • by EdIII (1114411)

        Lol.

        I love that video. The music reminds me of The Life Aquatic with Steve Zissou.

      • not disagreeing with your assessment, but:

        Gunk can get stuck in the holes and it has to be washed off, which requires a fair amount of work because I have to break the interaction between the gunk and the surface. That's your macroscopic intuition about how filters and such work.

        I think people may be basing their assumptions on typical RO membranes, which are microscopic in function and do get gunked up and need to be replaced. In fact, that's next on my project list for the kitchen, after I get done wasti

  • Why stop at salt? (Score:5, Interesting)

    by cryfreedomlove (929828) on Sunday July 01, 2012 @11:56AM (#40510773)
    How does this filter work on bacteria and viruses? The standard of living in the 3rd world would go up dramatically with free access to clean water.
    • Re:Why stop at salt? (Score:5, Interesting)

      by RPGillespie (2478442) on Sunday July 01, 2012 @12:10PM (#40510873)
      Well considering that the holes are the size of water molecules, I think it would be safe to say that bacteria and viruses would not fit. It would be like trying to force a tennis ball through a hole in a pasta strainer.
    • Re:Why stop at salt? (Score:5, Interesting)

      by girlintraining (1395911) on Sunday July 01, 2012 @12:45PM (#40511117)

      The standard of living in the 3rd world would go up dramatically with free access to clean water.

      There's a trend towards decreasing access to freshwater in many developed parts of the world as well. Much of the southern United States will be uninhabitable within our lifetimes if they do not secure another source of fresh water. I do not think just the '3rd world' has this problem. We will all be '3rd world' if the trend continues. And then no world... because almost all life on land depends on it.

      • Re:Why stop at salt? (Score:5, Interesting)

        by bill_mcgonigle (4333) * on Sunday July 01, 2012 @12:56PM (#40511175) Homepage Journal

        Much of the southern United States will be uninhabitable within our lifetimes if they do not secure another source of fresh water

        yet if you mention this to people who live there they go absolutely bonkers denial on you. I guess I'm not speaking about the small minority who will profit from doing the math.

        • Re:Why stop at salt? (Score:5, Informative)

          by jbeach (852844) on Sunday July 01, 2012 @01:10PM (#40511263) Homepage Journal
          Agreed. People can show even more denial with this than with the Peak Oil problem we're going to be facing. Not the Pentagon; they're busy making plans and releasing public papers that point out the upcoming world shortages in water AND oil. But they're a bunch of pointy-headed eco-socialists apparently.
      • Re:Why stop at salt? (Score:5, Interesting)

        by evilviper (135110) on Sunday July 01, 2012 @05:30PM (#40512469) Journal

        Much of the southern United States will be uninhabitable within our lifetimes if they do not secure another source of fresh water.

        Nonsense. Less than 1/4th of all fresh water goes to domestic use. First, other southern states will start adopting some of California's water conservation methods, like low-flow fixtures (toilets, shower-heads, large-drip sprinklers, leech lines), and then it'll escalate to cutting off of ornamental fountains, and disappearing lawns. In the longer-term, grey water systems will be put in-place, and municipalities will be more inclined to supplement groundwater with recycled (sewer) water.

        We will all be '3rd world' if the trend continues. And then no world... because almost all life on land depends on it.

        That's just mind-numbing... This is just a method to make desalination CHEAPER. And desalination is just one method of water filtration and reprocessing. My $10/mo water bill going up, even drastically, will have practically no effect on me, while it will make gathering other water sources, and more aggressive processing methods become economical for municipalities... It's good old supply and demand.

        Some people pay more per-gallon for water than they do for gasoline, thanks to "bottled water", so we can obviously afford a higher price here in the first-world.

      • For areas east of the Mississippi River, my understanding is that they will not become uninhabitable, merely that the current rate of population growth for those areas is unsustainable. For areas west of the Mississippi River it is more complicated. All of them are experiencing population growth that will soon outstrip the available water supply (frequently they already have and are draining the groundwater reserves faster than they can be replenished). Some of areas rely on groundwater almost entirely, tho
    • Theoretically, yes, something that works at the molecular level will filter out viruses and bacteria. But best practices in water treatment require some form of sterilization downstream, whether chemical (chlorine, chloramines or ozone), mechanical (submicron or ulta filtration), or Ultraviolet light. A failed membrane would allow enough pathogens through to kill, depending on what was in the water to begin with, as well as the age or physical condition of the person drinking the contaminated water.
  • by vlm (69642) on Sunday July 01, 2012 @11:57AM (#40510777)

    Basically, the regular atomic structure of graphene means that you can create holes of any size, for example the size of a single molecule of water. Using this process scientist can desalinate saltwater 1,000 times faster than the Reverse Osmosis technique.

    It is a RO membrane, just a really good one? They've described exactly how a RO membrane works. Of course this may have more "holes per sq inch" or whatever, maybe even 1000 times as many.

    • by trout007 (975317) on Sunday July 01, 2012 @12:03PM (#40510829)

      This is only a guess by RO filters have two things that take power. They require a high pressure differential across the membrane which makes for expensive pumps, piping and electric bills. Also they have a lot of bypass water which wastes energy by making you bring it up to pressure and then just dump it out.

      If this membrane requires less pressure and less bypass it will significantly reduce both the capital costs and operating costs of such a system.

      • by qvatch (576224) on Sunday July 01, 2012 @12:30PM (#40511017)
        The abstract: "We show that nanometer-scale pores in single-layer freestanding graphene can effectively filter NaCl salt from water. Using classical molecular dynamics, we report the desalination performance of such membranes as a function of pore size, chemical functionalization, and applied pressure. Our results indicate that the membrane’s ability to prevent the salt passage depends critically on pore diameter with adequately sized pores allowing for water flow while blocking ions. Further, an investigation into the role of chemical functional groups bonded to the edges of graphene pores suggests that commonly occurring hydroxyl groups can roughly double the water flux thanks to their hydrophilic character. The increase in water flux comes at the expense of less consistent salt rejection performance, which we attribute to the ability of hydroxyl functional groups to substitute for water molecules in the hydration shell of the ions. Overall, our results indicate that the water permeability of this material is several orders of magnitude higher than conventional reverse osmosis membranes, and that nanoporous graphene may have a valuable role to play for water purification." Emphasis added for why, and the introduced problem
    • by phme (1501991)

      From phys.org [phys.org]:

      In contrast to RO, which uses high pressure to slowly push water molecules (but not salt ions) through a porous membrane, nanoporous materials work under lower pressures and provide well-defined channels that can filter salt water at a faster rate than RO membranes.
      However, this is the first time that scientists have explored the potential role of nanoporous graphene as a filter for water desalination. Single-layer graphene, which is just one carbon atom thick, is the ultimate thin membrane, making it advantageous for water desalination since water flux across a membrane scales inversely with the membrane’s thickness.
      [...]
      The scientists explain that there are two main challenges facing the use of nanoporous graphene for desalination purposes. One is achieving a narrow pore size distribution, although rapid experimental progress in synthesizing highly ordered porous graphene suggests that this may soon be feasible. The other challenge is mechanical stability under applied pressure, which could be achieved using a thin-film support layer such as that used in RO materials.

    • by fermion (181285)
      It is not an RO membrane which is why it may be difficult to make it work. In RO the majority of the filtrand is automatically washed away as only a small amount of the water makes it through the filter. So, for instance, if you have an RO filter installed in your house, you may use 100 gallons of filtered water, but will be charged for 1000 gallons, as this is the amount that flows through the filter. The disadvantage is that the water must be pressurized. This is not a huge expense as one can buy a g
  • If they've found a way to desalinate water with much less energy, practically, that's huge.
    • Given that energy is power exerted over time, making something 1000 times faster using the same energy means using 1000 times the power. Making it 1000 times faster using the same power would use 1/1000th of the energy.

      -------

      All notions of cause and effect are merely assertions of faith in statistics.
    • Ok, that almost summarizes it.

      The only thing missing is that the article implies that nobody have actualy created it. But there aren't enough details to be certain of that. I'd say, "they found, or somebody found, or there are people looking for it, or they think people could look for it".

    • Figure 8 on Page 6 of the actual paper [mit.edu] shows what they're measuring. They're comparing filter materials by Salt rejection % vs Water permeability measured in L/cm2/day/MPa. That unit incorporates all the energy-efficeny goodness you want in a filter without looking at what pump technology is actually used to provide the energy input. It says that more filtered water (L) per square centimeter of filter (/cm2) per day (/day) per MegaPascal of pressure (/MPa, the energy input) is more good. Assuming any particular pump technology would give you a number for MPa/MJ that you could apply, but it doesn't help you understadn the performance of the filter itself. The figure for improvement vs existing technology they actually give is 2-3 orders of magnitude (100-1000x) so TFS is taking the optimistic side.

      The bottom line is that this has a huge potential but is still a ways from practical application.

      • Yes, there's a lot of materials science to be done before this is practical, and there may be unforeseen complications.

        But if this works, it would be nice to have:

        • A practical filter for drinking saltwater through a straw.
        • Some really big changes in California and places with similar water issues.
    • by DaveGod (703167)

      If they've found a way to desalinate water with much less energy, practically, that's huge.

      TFA isn't wholly explicit but it actually talks about "efficiency" rather than "faster" as per the submission:

      According to researchers at MIT, graphene could also increase the efficicency of desalination by two or three orders of magnitude [...] while you can remove the salt from the water, the current methods of doing so are laborious and expensive. Graphene stands to change all that by essentially serving as the world’s most awesomely efficient filter. If you can increase the efficiency of desalination by two or three orders of magnitude (that is to say, make it 100 to 1,000 times more efficient) desalination suddenly becomes way more attractive as a way to obtain drinking water.

      Though following TFA's source link to Water Online [wateronline.com] we come back to "2-3 orders of magnitude faster" and then reference to energy and cost:

      In a new study, two materials scientists from MIT have shown in simulations that nanoporous graphene can filter salt from water at a rate that is 2-3 orders of magnitude faster than today’s best commercial desalination technology, reverse osmosis (RO). The researchers predict that graphene’s superior water permeability could lead to desalination techniques that require less energy and use smaller modules than RO technology, at a cost that will depend on future improvements in graphene fabrication methods.

      To me that implies subby read that source article, which is a rather better article, leading me to suspect "anonymous reader" subby is from http://www.geekosystem.com/ [geekosystem.com] It does kind of bug me a little when websites find someone else's story, don't contribute anythi

  • by trout007 (975317) on Sunday July 01, 2012 @11:59AM (#40510793)

    God I loved "Top Secret"

  • by K. S. Kyosuke (729550) on Sunday July 01, 2012 @11:59AM (#40510803)
    I just wonder if a graphene membrane could filter out the words "awesomely", "incredibly" and "super" from awesomely incredibly super texts, leaving only texts. *That* would be quite useful.
  • This sounds like it could be revolutionary - lack of fresh or clean water is one of the world's biggest problems. I'm assuming pathogens are larger than a molecule of water? Wonder what the cost would be, if it would be cheap enough to just churn out sheets of the stuff, or custom-made filters. The biggest problems aside from production would be clogging/cleaning and accidental contamination of the output stream.

  • The real link (Score:5, Informative)

    by OzPeter (195038) on Sunday July 01, 2012 @12:02PM (#40510817)

    The TFA is just a BS article that says nothing.
     
    A better link (and is in the TFA) is Nanoporous Graphene Could Outperform Best Commercial Water Desalination Techniques [wateronline.com]
     
    However that references Nanoporous graphene could outperform best commercial water desalination techniques [phys.org]
     
    Now we finally we get to the actual link Water Desalination across Nanoporous Graphene [acs.org] (which unfortunately you need to have the right credentials to see - which I don't)
     
    How come I can follow those links and the TFS can't?

  • Thank you, anonymous reader, for a confused summary of an idiotic blog post about a moderately dumbed-down article about an interesting article.

    What they're talking about is reverse osmosis, and there's no way to make it two or three orders of magnitude more efficient. Commercial systems already hit 30% to 60% of the thermodynamic limit for energy efficiency; all graphene offers in this case is a way to increase the speed, decrease the filter size, or reduce the unnecessarily wasted energy. There's sti
  • trifecta (Score:5, Funny)

    by tverbeek (457094) on Sunday July 01, 2012 @12:04PM (#40510843) Homepage

    Once we figure out how to make nanobots out of stem cells and graphene, every problem known to humanity will be solved!

    • Once we figure out how to make nanobots out of stem cells and graphene, every problem known to humanity will be solved!

      What about the as-of-yet unsolved problem of "Where shall we have lunch?"

      • by gl4ss (559668)

        Once we figure out how to make nanobots out of stem cells and graphene, every problem known to humanity will be solved!

        What about the as-of-yet unsolved problem of "Where shall we have lunch?"

        I think you're looking for http://www.wherethefuckshouldigotoeat.com/ [wherethefu...otoeat.com]

    • by barfy (256323)

      Only if it improved battery life by 10x...

      • by Spodi (2259976)

        Only if it improved battery life by 10x...

        That would only be possible if it is done in the cloud.

    • I realize this was intended as a joke, and I understand why it's funny. But has it occured to anyone else that it's also entirely plausible? Turn the stem cells to white cells, reprogram them, give them little CNT arms to wiggle around, poof, you've got a bunch of injectable robots.
  • Hey, doesn't that mean that there's another way to produce 100% pure ethanol? http://en.wikipedia.org/wiki/Ethanol_purification#Molecular_sieves [wikipedia.org]
    • "Troll" is nothing to do with fantasy monsters and everything to do with fishing. A troll is someone who floats a line with yummy bait across a discussion board and waits to see who bites, having failed to notice that the grub or worm is on a hook.

      These people who didn't discover the Internet till this century...kindly remove yourself from my area of cultivated graminoids.

  • While I'm sure this process would be useful by itself, I wonder if the same or similar techniques could be used for purifying other materials. For example, maybe new levels of purity in various fuels.
  • The original paper (Score:5, Informative)

    by jmichaelg (148257) on Sunday July 01, 2012 @12:14PM (#40510907) Journal

    Here's a link to the original paper on Grossman's website. [mit.edu]

  • by mark-t (151149) <markt@PARISlynx.bc.ca minus city> on Sunday July 01, 2012 @12:59PM (#40511193) Journal

    Water molecule size, roughly 0.340 nm
    Salt molecule size, roughly 0.500 nm
    Graphene molecule size, roughly 0.142 nm
    Difference in size between water and salt molecule, roughly 0.160 nm
    The difference in size between water and salt is just barely more than the size of a single graphene molecule, so that leaves absolutely *NO* margin for error when designing the graphene sheet with those holes.

    This might very well have already been proven to really work... but I expect it would be extremely cost ineffective at larger scales owing to the consistent and extremely accurate precision that would be needed when trying to do this at a macroscopic scale.

  • Graphene: (Score:4, Funny)

    by MyFirstNameIsPaul (1552283) <myfirstnameispaul@gmail.com> on Sunday July 01, 2012 @03:51PM (#40512019) Homepage Journal
    The most useful substance never mass-produced.
  • Yeah [discovermagazine.com].

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