Slashdot Mirror

← Back to Stories (view on slashdot.org)

Graphene-Based Sieve Turns Seawater Into Drinking Water (bbc.com)

Posted by BeauHD on from the water-into-wine dept.

An anonymous reader quotes a report from BBC: A UK-based team of researchers has created a graphene-based sieve capable of removing salt from seawater. The sought-after development could aid the millions of people without ready access to clean drinking water. The promising graphene oxide sieve could be highly efficient at filtering salts, and will now be tested against existing desalination membranes. It has previously been difficult to manufacture graphene-based barriers on an industrial scale. Reporting their results in the journal Nature Nanotechnology, scientists from the University of Manchester, led by Dr Rahul Nair, shows how they solved some of the challenges by using a chemical derivative called graphene oxide. Isolated and characterized by a University of Manchester-led team in 2004, graphene comprises a single layer of carbon atoms arranged in a hexagonal lattice. Its unusual properties, such as extraordinary tensile strength and electrical conductivity, have earmarked it as one of the most promising materials for future applications. But it has been difficult to produce large quantities of single-layer graphene using existing methods, such as chemical vapor deposition (CVD). Current production routes are also quite costly. On the other hand, said Dr Nair, "graphene oxide can be produced by simple oxidation in the lab." Graphene oxide membranes have already proven their worth in sieving out small nanoparticles, organic molecules and even large salts. But until now, they couldn't be used to filter out common salts, which require even smaller sieves. Previous work had shown that graphene oxide membranes became slightly swollen when immersed in water, allowing smaller salts to flow through the pores along with water molecules. Now, Dr Nair and colleagues demonstrated that placing walls made of epoxy resin (a substance used in coatings and glues) on either side of the graphene oxide membrane was sufficient to stop the expansion.

83 of 111 comments (clear)

  1. yes but.... by Anonymous Coward · · Score: 1

    The biggest problem isn't removing the salt, it is what to do with all the excess salt that remains. If you dump it back into the ocean, it wipes out all sea life in a large radius. It is pretty devastating.

    1. Re:yes but.... by camperdave · · Score: 3, Funny

      We could use it as salt, or we could fill in the salt mines we've been digging, or we could drop it into the oceans to counteract all the freshwater melt coming off the polar ice caps from the global warming.

      --
      When our name is on the back of your car, we're behind you all the way!
    2. Re:yes but.... by telchine · · Score: 1

      or we could drop it into the oceans to counteract all the freshwater melt coming off the polar ice caps from the global warming.

      I think this was OP's point. If you dump it back in the oceans then... unless you spread it very, very thinly over a wide area, you'll end up with pockets of highly concentrated saline ocean which is very harmful to sea life.

    3. Re:yes but.... by ShanghaiBill · · Score: 5, Funny

      unless you spread it very, very thinly over a wide area, you'll end up with pockets of highly concentrated saline ocean which is very harmful to sea life.

      An obvious solution would be to dilute it with fresh water before dumping it into the ocean.

    4. Re:yes but.... by Dog-Cow · · Score: 2

      I really hope you were being sarcastic.

    5. Re:yes but.... by Zocalo · · Score: 1

      Salt can work fairly well as an energy storage device in green energy systems that are prone to fluctations in flow like solar and wind. Basically, you use some excess energy to heat up a volume of salt (to around 3000C is typical) then, when the wind drops or night falls, harvest that thermal energy back to provide power as the salt cools. Reheat the salt when your power source returns, and repeat.

      --
      UNIX? They're not even circumcised! Savages!
    6. Re:yes but.... by namgge · · Score: 1

      Whoosh!

    7. Re:yes but.... by slashrio · · Score: 2

      No need to be sarcastic. It's relatively cheap to transport salt to a location where fresh water is abundant, compared to moving that fresh water to where the salt is obtained as a result of desalination.

      --
      "Trump!!", the new Godwin.
    8. Re:yes but.... by slashrio · · Score: 1

      How do you contain salt at 3000 C?

      --
      "Trump!!", the new Godwin.
    9. Re: yes but.... by Anonymous Coward · · Score: 1

      Why not sell it to the upper-class restaurants in the US as a finishing salt. I'm sure with some clever marketing a few oz could be like $30, which could be used to purchase fresh water. It's all in the marketing...maybe Salt of the Earth.

    10. Re:yes but.... by DarkOx · · Score: 1

      I expect the GP was being sarcastic but that isn't perhaps so crazy. We already treat waste water heavily in most places before we dump it back into rivers or the ocean. If you are doing this on a community scale I don't see why transporting the salt over to the waste water plant and mixing it back into the that isn't entirely impractical.

      There are two problems
      1) the waste water already will contain a number of dissolved substances it may or may not be able to still dissolve enough salt to match the salinity of the ocean.
      2) Not all the water comes back as a waste water to the treatment plant, much of it waters crops or is boiled off in industrial processes etc. So there might not be enough water to redissolve all the salt even if supplemented with storm run off.

      At any rate I would expect at least a large portion of the salt could be returned to the environment be simply diluting it in 'fresh' water first. The rest might well be fed into the many industrial and agricultural application for salt.

      --
      Repeal the 17th Amendment TODAY! Also Please Read http://www.gnu.org/philosophy/right-to-read.html
    11. Re:yes but.... by jbmartin6 · · Score: 2

      But it is great for SEA MONKEYS®

      --
      This posting is provided 'AS IS' without warranty of any kind, implied or otherwise.
    12. Re:yes but.... by JoeMerchant · · Score: 1

      Nah, just make flamingo nesting grounds with it. Environmentally friendly, if you're a flamingo.

    13. Re:yes but.... by Applehu+Akbar · · Score: 1, Interesting

      "The biggest problem isn't removing the salt, it is what to do with all the excess salt that remains. If you dump it back into the ocean, it wipes out all sea life in a large radius. It is pretty devastating."

      This is classic enviro bullshit. You just claimed that if we suck in some seawater, separate the water from the minerals, and then return the minerals to the ocean again, that they magically turn toxic against the same species that have been spending their lives in it? Human desalination cannot change the amount of water or salt in the environment. "Excess salt" does not exist.

      In fact, because salt has value in commerce, a lot of desalination salt will be retained on land for use in industrial processes. So large-scale desalination could technically be used to decrease the amount of salt in the ocean - though the amounts of salt and water we are talking about are so small compared to what is in the oceans that we could never detect the change in any foreseeable future.

    14. Re:yes but.... by Ol+Olsoc · · Score: 5, Insightful

      "The biggest problem isn't removing the salt, it is what to do with all the excess salt that remains. If you dump it back into the ocean, it wipes out all sea life in a large radius. It is pretty devastating."

      This is classic enviro bullshit.

      And your response is typical reaction to an uninfomed person, making their statement magically said by all people concerned about the environment

      You just claimed that if we suck in some seawater, separate the water from the minerals, and then return the minerals to the ocean again, that they magically turn toxic against the same species that have been spending their lives in it? Human desalination cannot change the amount of water or salt in the environment. "Excess salt" does not exist.

      Okay lads, let's sit down and talk like adults, because you are both wrong.

      One of the first things we have to look at is the amount of salt that might be returned to the ocean. So we have a desalinization plant. Until the plant is taking a significant amount of water out, extracting the salt, and returning the salt to the ocean, it is hardly going to be a blip in the percentage of salt. So that environut you're railing at is generally wrong. Because there is one hellava lot of water in the ocean.

      note: because of local conditions, you would want to have a distributed return of the salt. You do not want to just dump it on the shoreline.

      But before you go patting yourself on the back, it is possible to get so much salt that it affects what if anything can live in the water. Mono Lake is one example. It has become so salty that no fish live in it. Brine shrimp and algae are it. The salinity level has varied - topping out at alomst 100 framps per liter in the early 80s. We've stopped diverting so much water, and the salinity level is lowering now, the target is 70 grams per liter. The reason we'r eallowing the lake to replenish is that it is an important migratory pathway for a lot of birds. The Great Salt Lake in Utah, which is the remnant of Lake Bonneville is another hypersaline body of water, and ecologically similar to Lake Mono. The Dead Sea is another hypersaline area, and it's named dead sea for a reason. Not much can live there. A few types of bacteria. So you are completely wrong - It is highly possible to have excess salt.

      So by spreading the return of the salt to the ocean over an area that avoids local hypersalinization, we'll not have much effect on the salinity of the oceans.

      --
      The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
    15. Re:yes but.... by MightyYar · · Score: 2

      That's not "the biggest problem". In fact, it's not really much of a problem at all. You don't end up with "salt", you end up with water that has a higher salinity than the input water. You keep enough new salty or brackish water moving through the input side to dilute the effect of pulling water out. Compared to the amount of water moving around in the tides, the desalinization plant is small potatoes. Compared to the amount of water removed from the oceans by evaporation, it is insignificant.

      Now perhaps you could argue that it would affect shallow inland seas and the like (Arabian Gulf), but probably a lot less so than the damming of rivers to capture their fresh water.

      --
      W..w..W - Willy Waterloo washes Warren Wiggins who is washing Waldo Woo.
    16. Re:yes but.... by PPH · · Score: 1

      So by spreading the return of the salt to the ocean over an area that avoids local hypersalinization, we'll not have much effect on the salinity of the oceans.

      Right. But who would build a desalinization plant in a location that would be susceptible to local hypersalinization? The plant efficiency would drop and fresh water production would eventually cease. Plants will be built in places with sufficient ocean currents to dilute their brine output and carry it away.

      --
      Have gnu, will travel.
    17. Re:yes but.... by khallow · · Score: 1

      Well just how devastating can local effects be? Sure, if you have huge numbers of desalinization plants running up the coast of say, California, dumping very salty water right off shore, it's going to cause problems for that region. But we have rather simple and low energy technologies for mixing salt into water that can greatly reduce the problem.

    18. Re:yes but.... by EndlessNameless · · Score: 1

      The real problem is:

      3) Places where freshwater flows into the ocean are brackish, and the organisms there are adapted to a low-salinity environment. Increasing the salinity there can disrupt the ecosystem just the same as it would further out in the ocean.

      There is really no good place to dump the excess salt. We can't just dump massive amounts of salt anywhere there is life. Maybe it could be prepared for human consumption---sea salt is often treated as a premium grocery item. I have no idea what volume to expect from a desalination plant, so it is possible the salt production could exceed our dietary needs.

      As always, there are other technical solutions, but the economic viability depends on the price and availability of other inputs.

      --

      ---
      According to the latest ruleset, this post should be modded as Vorpal Flamebait +5.
    19. Re:yes but.... by Zocalo · · Score: 1

      You keep it in a glorified pressure cooker; the higher thermal difference just means more energy can be reclaimed. I couldn't find a link to the research faculty I read about that was taking it to that extreme some years back (maybe it went nowhere), but this company is doing something similar at a much more routine atmospheric pressure approach at 566C, and this one was working towards a solution closer to boiling point with a storage temp of 1200C.

      --
      UNIX? They're not even circumcised! Savages!
    20. Re:yes but.... by EndlessNameless · · Score: 1

      The plant efficiency would drop and fresh water production would eventually cease.

      The plant might see reduced efficiency, but there is a limit on how high the salinity will go since there is always some fresh water coming in. The problem is that desalination plants will remain effective in a large salinity range----a range which includes levels harmful to oceanic life.

      E.g., Israel plans to desalinate water from the Red Sea, which is one of the saltiest bodies of water on Earth. Only the Dead Sea and a few obscure lakes are saltier.

      Israel plans to address their problem by pumping the brine into the Dead Sea where it won't really hurt anything. The Dead Sea only has a few microscopic lifeforms that have adapted to that environment, so they don't have to worry about killing off fish, vegetation, crabs, etc.

      --

      ---
      According to the latest ruleset, this post should be modded as Vorpal Flamebait +5.
    21. Re:yes but.... by skids · · Score: 1

      You might even be able to recover some energy from the brackish water as you mix it back in via an osmotic power cells.

      --
      Someone had to do it.
    22. Re:yes but.... by TechyImmigrant · · Score: 1

      The biggest problem isn't removing the salt, it is what to do with all the excess salt that remains. If you dump it back into the ocean, it wipes out all sea life in a large radius. It is pretty devastating.

      I thought the biggest problem was violating the laws of thermodynamics. Salt water is at a lower entropy than separated water and salt. It takes energy to separate salt and water. We already know how to separate salt and water. Maybe this is more efficient?

      --
      I should use this sig to advertise my book ISBN-13 : 978-1501515132.
    23. Re:yes but.... by Ol+Olsoc · · Score: 1

      So by spreading the return of the salt to the ocean over an area that avoids local hypersalinization, we'll not have much effect on the salinity of the oceans.

      Right. But who would build a desalinization plant in a location that would be susceptible to local hypersalinization? The plant efficiency would drop and fresh water production would eventually cease. Plants will be built in places with sufficient ocean currents to dilute their brine output and carry it away.

      My reply was in the context of the people having the disagreement. Of course, you don't want to dump in the same area you extract from.

      --
      The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
    24. Re:yes but.... by Ol+Olsoc · · Score: 1

      With all the ocean shipping, wouldn't it be possible to pay the ships to take a few containers and drop it at a controlled rate overboard as they travel? This prevents any particular location from being overly concentrated and allows ocean currents to further distribute it worldwide.

      Possibly. I was thinking of a barge loaded with the salt, which will be kind of a wet griny state, and with a slow conveyer, plop it back into the water. No reason a container ship couldn't tow it. Also, there are some places like offshore Greenland that are having a large influx of freshwater, so it might re-salinate the ocean around there.

      Although, the East Coast of North America isn't likely to need the desalinization plants. We tend toward too much water.

      --
      The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
    25. Re:yes but.... by mrchaotica · · Score: 3, Interesting

      This entire thread has been idiotic, because everybody's missing the most important factor:

      The desalinized water doesn't leave the system; it gets used and returned.

      People drink the water, piss it back out, and flush it down the drain. The drain goes to the sewer. The sewer goes to the wastewater treatment plant. So re-salinize the wastewater after treating it and you can dump it back into the ocean at the same salinity you started with! (Give or take losses from outdoor watering and gains from precipitation falling into combined sewers, anyway. The net difference could be significant, but we shouldn't dismiss the idea out-of-hand by assuming so.) So just build the two treatment plants next to each other and pipe the salt across from the desalinizer to the resalinizer.

      Or better yet, just build one plant capable of treating any water (seawater or wastewater) to a drinkable standard, and make the damn thing a closed loop!

      --

      "[Regarding the 'cloud,'] ownership was what made America different than Russia." -- Woz

    26. Re:yes but.... by AaronW · · Score: 1

      Dump it in the great salt lake. I don't think anyone will notice.

      --
      This post is encrypted twice with ROT-13. Documenting or attempting to crack this encryption is illegal.
    27. Re: yes but.... by bigpat · · Score: 1

      Problem solved... Well done everyone.

    28. Re:yes but.... by Applehu+Akbar · · Score: 1

      Well, missing from your rant is localized effects. But carry on, angry ignorant fool.

      Okay, carrying on. Soaker hoses exist, allowing us to place concentrated brine back into the sea without oversalting any one place. Compared to the separation problem, this will be the trivial part of desalination.

    29. Re:yes but.... by Applehu+Akbar · · Score: 1

      Salt lakes like the big one in Utah are historically sources of salt, not places where we are going to dump more of it. Ever driven I-80 between SLC and Wendover? You see salt extraction plants lined along the highway, taking salt out of the lake. One level higher up is the Bonneville Salt Flat, which we are tryingto keep salty so we can race on it.

      We will be desalinating from the oceans, and what salt we return will be to the oceans.

    30. Re:yes but.... by Applehu+Akbar · · Score: 1

      This was my point. Water on the Earth circulates in a closed system, with none of it being "used up" or permanently sequestered. When fresh water leaches soluble minerals out of the rocks in the places where it flows, nature dumps all of the minerals into the oceans or into land basins without an outlet.

      Man has the ability to optionally pull dissolved minerals out of the natural circulation and use them for human purposes. Now that desalination is about to vastly increase the amount of dissolved minerals that we can control, we have the opportunity to use more of them. Those that we don't, we dump back in the ocean the natural way.

    31. Re:yes but.... by Ol+Olsoc · · Score: 1

      This entire thread has been idiotic, because everybody's missing the most important factor:

      The desalinized water doesn't leave the system; it gets used and returned.

      People drink the water, piss it back out, and flush it down the drain. The drain goes to the sewer. The sewer goes to the wastewater treatment plant. So re-salinize the wastewater after treating it and you can dump it back into the ocean at the same salinity you started with!

      Well, since you called me an idiot, there is a problem with your great wisdom.

      Imagine a fellow so much smarter than others that he suggests injecting saline brine into freshwater streams. Apparently in genius world, all sewage treatment plants are along the coast.

      Who knew? Thanks for elightiening us, I better check to see if those sewage plants near me are actually CIA listening stations or something. The allegedly treated effluent they are allegedly dump into the alleged freshwater streams and can be allegedly observed by my alleged eyeballs is apparently a dream.

      tl:dr version. Don't call people idiots and propose a solution that is magnitudes more idiotic.

      --
      The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
    32. Re:yes but.... by Ol+Olsoc · · Score: 1

      This was my point. Water on the Earth circulates in a closed system, with none of it being "used up" or permanently sequestered.

      However, if you think that pushing saltwater into freshwater streams is even remotely a good idea, you might look up what saltwater does to freshwater flora and fauna.

      The return paths are not paved with salt, but freshwater. Either through evaporative processes like water to cloud to rain, or via streams, virtually all that are freshwater.

      --
      The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
    33. Re:yes but.... by Lehk228 · · Score: 1

      carefully.

      --
      Snowden and Manning are heroes.
    34. Re:yes but.... by Applehu+Akbar · · Score: 1

      "However, if you think that pushing saltwater into freshwater streams is even remotely a good idea, you might look up what saltwater does to freshwater flora and fauna."

      Nowhere did I mention dumping salt into fresh water. We have plenty of salt water where it can go.

    35. Re:yes but.... by mrchaotica · · Score: 1

      Well, since you called me an idiot...

      No I didn't; I called the thread idiotic. There's a difference.

      Apparently in genius world, all sewage treatment plants are along the coast.

      ...But now I will, you blithering moron!

      In case you hadn't noticed, the topic of this thread is desalinization. That's something you only consider doing in the first place when the ocean is the least-inconvenient place to get the water supply from. Given that assumption, can you guess what the most convenient body of water to discharge the wastewater into might be?

      That's right, the ocean!

      I admit, there are places that have water supplies other than the ocean. But in that case, they have water supplies other than the ocean and the problem of what to do with the excess salt is moot because you're not desalinizing to begin with!

      --

      "[Regarding the 'cloud,'] ownership was what made America different than Russia." -- Woz

    36. Re:yes but.... by Ol+Olsoc · · Score: 2

      That's something you only consider doing in the first place when the ocean is the least-inconvenient place to get the water supply from. Given that assumption, can you guess what the most convenient body of water to discharge the wastewater into might be?

      That's right, the ocean!

      I admit, there are places that have water supplies other than the ocean. But in that case, they have water supplies other than the ocean and the problem of what to do with the excess salt is moot because you're not desalinizing to begin with!

      Hold on a second. Your story has changed - a lot If I recall, and cutting and pasting seems to verify that. You wrote :

      "People drink the water, piss it back out, and flush it down the drain. The drain goes to the sewer. The sewer goes to the wastewater treatment plant. So re-salinize the wastewater after treating it and you can dump it back into the ocean at the same salinity you started with!

      I don't recall myself or anyone else in this subthread saying that the saline sludge shouldn't go back in the ocean. Given the puny amount we can remove, it isn't going to make much of a difference as long as we don't create local hypersaline spots. That isn't difficult. And I myself will state pretty strongly that your concept which you possibly seem to have abandoned quickly, that of "re-salinize the wastewater after treating it and you can dump it back into the ocean at the same salinity you started with! isn't going to work. Other people want that treated fresh water.

      You don't know how Cali works it might appear. This place lives and dies on fresh water, and has been taking all that the West can give it, and wants more. Taking fresh, even if not potable treated waste water and dumping waste brine in it to pump it into the ocean is not going to go over well at all there. In fact, here's what is happening now, Cali is using a lot of wastewater to irrigate, and plans using more. http://www.waterboards.ca.gov/...

      One of the most interesting things this moron can imagine is that the smart people seem to think that desalinization is some sort of miracle cure, that will solve California's water issues.

      It won't.

      In 2010, California used 38 billion gallons per day of water from all sources. 67 percent of the total water used, and 74 percent of all non saline water use went to irrigation. RIght away, that tells us that there isn't going to be any use for desalination other than spot uses, and providing providing potable only water. https://ca.water.usgs.gov/wate...

      So California's farmers are going to want that treated sewage water, just like they do now, and the amount of desalination taking place is going to be spot located, and returned to the ocean in some other manner, not in the badly needed, treated fresh wastewater.

      --
      The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
    37. Re:yes but.... by q4Fry · · Score: 1

      There is really no good place to dump the excess salt.

      Modest proposal: Carthage.

    38. Re:yes but.... by q4Fry · · Score: 1

      Are they taking the salt out to use it? Or because it would be problematic to leave it in the lake?

    39. Re:yes but.... by Applehu+Akbar · · Score: 1

      The one company I remember from that route is Morton Salt. You know, the salt that's in every kitchen.

  2. Seer by dohzer · · Score: 1, Informative

    Sure, but the Water Seer can turn air into drinkable water!

    1. Re:Seer by Anonymous Coward · · Score: 1

      Water Seer is a sorry hoax.

      https://www.youtube.com/watch?v=LVsqIjAeeXw

  3. Two questions by malx · · Score: 3, Interesting

    1. What throughput / flowrate can you achieve, per unit of area?

    2. How do you clear clogging?

    1. Re: Two questions by Antique+Geekmeister · · Score: 2

      For small scale, "one time use filters", you can simply distill the water by boiling it. It's the industrial scale "water our crops", "provide drinking water for a community", or "provide water for industry" that require large scale systems and for which the maintenance cost and energy cost of known, stable techniques like evaporation make it impractical.

    2. Re:Two questions by 140Mandak262Jamuna · · Score: 1
      It is easy to clear the clogging. You use another graphene filter to get more freshwater to clear clog in the original filter.

      Oh, yeah, how you clear clog in the other filter? Come on, Sherlock, you just have cleared the clogs and have a fresh good clean graphene filter in your hand don't you realize that. You use the original to clear the clog of the other filter. Simple. Just. use. your. brain.

      --
      sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
    3. Re:Two questions by swb · · Score: 3, Informative

      From what I've read in the marine world, there's no cure for clogging, just ways to minimize it. Multi-stage sea strainers cheaply and/or easily replaced and cleaned to get the water as de-gunked as possible before it hits the really good membrane. And enough water storage that you don't have to run your water maker in poor quality harbor or shallows water.

    4. Re:Two questions by jafiwam · · Score: 1

      2. How do you clear clogging?

      Review a diagram of a current desalination plant.

      Two things can declog. First, you can run the filter backwards for a short time, water in motion can dislodge built up material far in excess of the water that flowed forward gathering that material. Second, for salts themselves clogging, you let natural entropy take care of it for you.

      These filters are often tubes through which high pressure water is added, cleaned water enters the outer jacket area and falls off. Higher salinity water continues down the tube at high pressure and is discharged.

      It's this higher salinity (but not solid salt) water that carries would would be solid salt off the filter for discharge.

      These engineering "gotchas" the amateurs are coming up with here have already been taken care of a long time. Current desalination plants work don't they? What do you think they do in those? Wave a magic wand?

    5. Re:Two questions by Verdatum · · Score: 1
      Serious answers: 1. It sounds like they don't have numbers yet; and there's more to it than flow-rate. Massively more important than flow-rate is the theoretical watts per Liter needed to force the water through under pressure. ("Theoretical" because you don't worry about pump-efficiency when comparing filter performance.)

      2. "Clearing" the filter isn't exactly a thing because the salt never crystallizes. It remains in the water that's on the intake side of the filter. You "clear" the filter by not allowing all of the water from the sea-water to pass through the filter. a portion of it is channeled off. That portion has a higher salinity than seawater, ideally, about as close to saturated as possible. This pressurized salt-solution, known as concentrate, is first used to drive a turbine to recover the potential energy of being pressurized. The turbine drives a pump that helps raise the pressure of the incoming seawater (Externally powered pumps pressurize the incoming water the rest of the way). The concentrate, now at low pressure is either returned to the sea, or it's sent to evaporation pools to make sea-salt. In most cases, no, it's not a problem to return the concentrate to the sea. When done with a properly designed marine-outfall, oceans are really really huge and constantly churned by tides and currents, so the effect it has on ocean saline levels is nothing compared to the effect of solar evaporation.

      Larger particulate is filtered earlier in the process. These filters can become clogged or "fouled". This can be solved using a process similar to what's described above, or by automated processes that constantly cycle the filters in use, and pressure-washing the fouled filters. There are also mechanical scrubber mechanisms and potentially sedimentation-pools that use flocculants to cause particulates to fall to the bottom where it can be scraped away as sludge; but these are all standard water-treatment processes that we've had solved for ages now.

    6. Re: Two questions by EndlessNameless · · Score: 1

      There are evaporation plants, but they are only feasible where solar energy is abundant. If solar concentration tech improves, the band where these plants are feasible will expand.

      With the green energy focus in industrial nations including solar power plants, it is possible the desalination industry may see a fringe benefit due to the engineering of better concentrators.

      --

      ---
      According to the latest ruleset, this post should be modded as Vorpal Flamebait +5.
    7. Re:Two questions by DraconPern · · Score: 1

      Since this is a filter, I am going to guess it will probably be like a replaceable filter system.  This is huge for not needing energy to work.

  4. Re:I'm no chemistry expert, but... by Mal-2 · · Score: 4, Insightful

    I'm no chemistry expert, but isn't graphene oxide simply CO2?

    Only the same way graphene is diamond.

    Allotropes.

    --
    How is the Riemann zeta function like Trump rallies? Both have an endless number of trivial zeros.
  5. Re:I'm no chemistry expert, but... by fisted · · Score: 1

    pretty sure it's just C

    --
    CLI paste? paste.pr0.tips!
  6. Re:I'm no chemistry expert, but... by Rei · · Score: 5, Informative

    No. But it's not graphene either. Graphene oxide has been around since the 1850s. Graphene (isolated planes of graphite). The first single-layers of graphene were grown in small amounts in the 1970s, but it wasn't really until the 2000s that sizeable amounts produced by macroscopic means were achieved.

    This article is playing on graphene hype to try to play up graphene oxide, which is a more mundane substance. Don't get me wrong, it's neat and has uses (due to how planar its membranes are), but it doesn't have the properties of graphene itself. And it's been used in this particular application (desalination membranes) since the 1960s. Lockheed has had them on the market since 2013.

    --
    Kneel Before Christ!
  7. Reverse osmosis is an old hat by Anonymous Coward · · Score: 5, Informative

    Desalination of seawater by reverse osmosis is an old hat. The main challenge from an energy POV is the high pressure differential (and the flow, of course) needed. This won't change much with a new membrane.

    Of course, a new membrane might have other desirable properties (cost, robustness, whatever), so every new option is a Good Thing, but the abstract suggests that graphene is something new here. It isn't. Just one more tool in an old chest.

    1. Re:Reverse osmosis is an old hat by Chrisq · · Score: 1

      Desalination of seawater by reverse osmosis is an old hat. The main challenge from an energy POV is the high pressure differential (and the flow, of course) needed. This won't change much with a new membrane.

      Of course, a new membrane might have other desirable properties (cost, robustness, whatever), so every new option is a Good Thing, but the abstract suggests that graphene is something new here. It isn't. Just one more tool in an old chest.

      That's what they're hoping from TFA:

      "When the capillary size is around one nanometre, which is very close to the size of the water molecule, those molecules form a nice interconnected arrangement like a train," Dr Nair explained.
      "That makes the movement of water faster: if you push harder on one side, the molecules all move on the other side because of the hydrogen bonds between them. You can only get that situation if the channel size is very small."

      ...

      "This is our first demonstration that we can control the spacing [of pores in the membrane] and that we can do desalination, which was not possible before. The next step is to compare this with the state-of-the-art material available on the market," said Dr Nair.

    2. Re:Reverse osmosis is an old hat by brianerst · · Score: 1

      I've never heard a good explanation why we don't use tidal energy to create the requisite pressure. Open gates at mean sea level, wait for high tide to flood reservoir, close gates, open much smaller exit path past filters during tide retreat, rinse, repeat. The massive water reserve attempting to push through the narrow exit path raises the pressure of the water.

      There must be a good physics or economics explanation as to why this doesn't work (not enough pressure, the amount of energy required to build the original system exceeds the amount of energy used by a regular desalinator, etc.).

  8. The famous Nick Rivers' Reply by Provocateur · · Score: 3, Funny

    Scientist: Do you know what this means?

    Nick: There'd be an *awful* lot of salt.

    --
    WARNING: Smartphones have side effects--most of them undocumented.
    1. Re:The famous Nick Rivers' Reply by Ol+Olsoc · · Score: 1

      Scientist: Do you know what this means?

      Nick: There'd be an *awful* lot of salt.

      And some gold too.

      --
      The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
    2. Re:The famous Nick Rivers' Reply by Sloppy · · Score: 1

      It's "Wow! They'd have enough salt to last forever!"

      --
      As copyright owner of this comment, I authorize everyone to defeat any technological measure which limits access to it.
    3. Re:The famous Nick Rivers' Reply by TechyImmigrant · · Score: 1

      Scientist: Do you know what this means?

      Nick: There'd be an *awful* lot of salt.

      And some gold too.

      Cowboy Neal is salty too.

      --
      I should use this sig to advertise my book ISBN-13 : 978-1501515132.
    4. Re:The famous Nick Rivers' Reply by Ol+Olsoc · · Score: 1

      Scientist: Do you know what this means?

      Nick: There'd be an *awful* lot of salt.

      And some gold too.

      Cowboy Neal is salty too.

      Seems like the basis for a song there.

      --
      The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
  9. Re:I'm no chemistry expert, but... by houghi · · Score: 2

    There is editing. It is just called Preview.

    --
    Don't fight for your country, if your country does not fight for you.
  10. Is there anything Graphene CAN'T do? by Merk42 · · Score: 4, Funny

    Yes.
    Come to market.

  11. Osmosis abides by Anonymous Coward · · Score: 1

    The natural process of osmosis will persist. This is the tendency for water to flow through the filter in the wrong direction (the fresh water flows into the salt water). Sea water has (I looked it up) an osmotic pressure of 28 atmospheres (411 pounds per square inch)...one must supply a pressure of this amount to stop the exfiltration. To make a substantial amount of water go through in the right direction, you'll need double this...at least 800 psi. To maintain this pressure requires a lot of energy. Usually Electricity --> motor --> pump.

    It's really a new membrane for reverse-osmosis water purification. These devices are widely used in the Bahamas, Key West, thousands of other locations -- but haven't expanded widely due to high energy requirements.

  12. Re:I'm no chemistry expert, but... by Applehu+Akbar · · Score: 1

    Using graphene for desalination was previously researched at MIT:
    https://www.google.com/url?sa=...

  13. Re:I'm no chemistry expert, but... by es330td · · Score: 2

    I'm pretty sure a substantial number of /. posters think their code will run the first time it executes. Why would they preview a post?

  14. Re: I'm no chemistry expert, but... by phaserbanks · · Score: 1

    Those were only computer simulations.

  15. How Much Salt? by sycodon · · Score: 5, Interesting

    Los Angeles consumed about 17,957,000,000 in August of 2013

    A gallon of sear water contains 4.5 oz of salt

    So if LA used exclusively desalinized water, they would have 10,100,812,500 lbs of salt on their hands (17,957,000,000*4.5/8)

    This is about 126,260,156 cubic feet.

    Your average Panamax cargo ship has about 3.6 million cubic feet of space.

    This is about 35 ships worth of salt.

    There are about 16,900 bulk carrier ships operating in the world.

    --
    When Fascism comes to America, it will call itself Anti-Fascism, and tell you to give up your guns.
    1. Re:How Much Salt? by TechyImmigrant · · Score: 1

      Given that the salt came from the oceans, you could just dump it back into the sea.

      --
      I should use this sig to advertise my book ISBN-13 : 978-1501515132.
    2. Re:How Much Salt? by dgatwood · · Score: 1

      There are 16 ounces to a pound, not 8, so it's half that. Still, that's a lot of salt.

      --

      Check out my sci-fi/humor trilogy at PatriotsBooks.

    3. Re:How Much Salt? by sycodon · · Score: 1

      Yikes.

      This is why I'm not a mathematician and I'm overweight by 40 lbs.

      --
      When Fascism comes to America, it will call itself Anti-Fascism, and tell you to give up your guns.
    4. Re:How Much Salt? by sycodon · · Score: 1

      Three ships leaving port a month and dumping the salt during the trip to HI would be enough.

      Really...given the ships plying the waters these days distributing the salt over a large area is a trivial exercise.

      --
      When Fascism comes to America, it will call itself Anti-Fascism, and tell you to give up your guns.
  16. Re:I'm no chemistry expert, but... by Verdatum · · Score: 1

    The important bit here is the swelling thing. They indicate that graphene-oxide wasn't particularly good at filtering sodium-chloride and allowing water to pass, and they resolved the issue by making what sounds like a graphene-oxide/epoxy composite. Good for them. It's a pretty obvious solution to the problem, and this is just materials-science chugging along at the speed of research, but still, good for them. Naturally, mainstream news has to spice up the story to make readers care, but honestly, BBC didn't do that horrible of a job this time. They aren't claiming this is revolutionary. They aren't claiming a single benefit over existing polymer filters because the data isn't in yet. But it's true that there's not much point in talking up how cool graphene is, and should've stuck to explaining how graphene-oxide is an older different animal that just happens to have been given a new name that designates when graphite-oxide is in its one-layer thick form.

  17. Re:I'm no chemistry expert, but... by TechyImmigrant · · Score: 1

    pretty sure it's just C

    Graphene is like Boost::C++ or something.
     

    --
    I should use this sig to advertise my book ISBN-13 : 978-1501515132.
  18. So... by SlaveToTheGrind · · Score: 1

    Graphene is finally worth its salt?

  19. Re:I'm no chemistry expert, but... by camperdave · · Score: 1

    Graphene by itself is just carbon (C) so graphene oxide would be CO or CO2.

    --
    When our name is on the back of your car, we're behind you all the way!
  20. Re:I'm no chemistry expert, but... by camperdave · · Score: 1

    Just because an element has allotropes, doesn't mean the oxides are allotropes (or maybe it does, as I said, I'm not a chemist). Either way, the oxide is CO or CO2.

    --
    When our name is on the back of your car, we're behind you all the way!
  21. Re:I'm no chemistry expert, but... by fisted · · Score: 1

    Oh, I didn't see the part where you said oxide. My bad.

    --
    CLI paste? paste.pr0.tips!
  22. Re:I'm no chemistry expert, but... by Mal-2 · · Score: 1

    Then the better term is structural isomer. It is still untrue that carbon + oxygen has to form CO or CO.

    But there's no need to take my word for it. Graphite oxide (includes graphene oxide as a subdivision).

    --
    How is the Riemann zeta function like Trump rallies? Both have an endless number of trivial zeros.
  23. Re:I'm no chemistry expert, but... by q4Fry · · Score: 1

    I was debugging your logic and I think I fou

  24. I created the Perforene article... by GPS+Pilot · · Score: 1

    It's cool that you found it.

    It's not exactly on the market though... the article says "The product was not expected to be released until 2020."

    --
    That that is is that that that that is not is not.
  25. Re:I'm no chemistry expert, but... by camperdave · · Score: 1

    Carbon+oxygen forms compounds containing carbon and oxygen. It doesn't form compounds containing hydrogen. Or is the energy released in the combustion enough to synthesize new elements?

    --
    When our name is on the back of your car, we're behind you all the way!
  26. Re:I'm no chemistry expert, but... by Mal-2 · · Score: 1

    Hydrogen gets trapped if it is available. If it's not, the graphene still oxidizes without it. If you're not inclined to read the linked article, then I'm not going to summarize it for you.

    --
    How is the Riemann zeta function like Trump rallies? Both have an endless number of trivial zeros.