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Making Saltwater Drinkable With Graphene
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."
So how durable is this membrane when it comes to dealing with impurities?
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?
what about the holes getting blocked by minerals and impurities? seems high maintenance job.
I mean, you probably can't filter water through a block of carbon, but what you can do is cheat and just use individual graphene layers placed very closely together. Also, if you don't rely on the force of gravity but instead let the water enter sideways or upwards, deposits would be a smaller problem.
Nestle should be all over this.
Unfortunately the would probably bury it.
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.
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.
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
If they've found a way to desalinate water with much less energy, practically, that's huge.
Bruce Perens.
God I loved "Top Secret"
I love Jesus, except for his foreign policy.
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.
Ezekiel 23:20
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 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
However that references Nanoporous graphene could outperform best commercial water desalination techniques
Now we finally we get to the actual link Water Desalination across Nanoporous Graphene (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?
I am Slashdot. Are you Slashdot as well?
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 still no getting around that darned osmotic pressure.
Bugrit! Millenium hand and shrimp!
Once we figure out how to make nanobots out of stem cells and graphene, every problem known to humanity will be solved!
http://alternatives.rzero.com/
Hey, doesn't that mean that there's another way to produce 100% pure ethanol? http://en.wikipedia.org/wiki/Ethanol_purification#Molecular_sieves
Did you know 80 to 90% of the moderators on slashdot wouldn't recognize a troll even if one dragged them under a bridge.
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.
This is my signature. There are many like it, but this one is mine.
Here's a link to the original paper on Grossman's website.
Old idea is old.
How much energy is consumed with this form of filtration? Then we need a way to handle the salt and calcium that is left behind. Dumping that by-product back into the ocean is not a reasonable idea. Perhaps we could find some old salt mines and pack the by-products down into those huge old mines. Then we would have to consider the energy required to store all of that waste.
I feel like science theory seems to be easy top come by but useful, applied, science that actually helps man kind seems to be rare and hard to put into play/
These people who didn't discover the Internet till this century...kindly remove yourself from my area of cultivated graminoids.
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
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.
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All notions of cause and effect are merely assertions of faith in statistics.
An atom is roughly 5 orders of magnitude smaller than a virus; so on that scale a salt molecule wouldn't be significantly bigger than a single atom.
If others have found a way to abundance of energy, we won't need graphene to desalinate water.
That wouldn't be huge, that would be disruptive.
1 - 3 July at College of William & Mary; International Low Energy Nuclear Reactions Symposium (ILENRS-12)
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".
Rethinking email
Michael Pritchard presented a filter device at TED in 2009 which used a similar concept to filter water. The video explains why bacteria and viruses are filtered out, and he demonstrates the process and drinks the resulting filtered water (taken from a sewage bath he concocts). Perhaps graphene's physical strength will make it a more sturdy water filter, which would be a particularly important criteria for use in the third world, but there is at least already a working prototype using a non-graphene material. http://www.ted.com/talks/michael_pritchard_invents_a_water_filter.html
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.
File under 'M' for 'Manic ranting'
I'm going to start putting it in my coffee.
Figure 8 on Page 6 of the actual paper 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.
But if this works, it would be nice to have:
Bruce Perens.
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 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/ It does kind of bug me a little when websites find someone else's story, don't contribute anything then go around plugging it like it's their scoop.
And BTW that Water Online source itself is lifted verbatim (stated as being with permission) from Phys.org.
Still pissy that you live in your mom's basement? some day you will be able to save enough to pay a hooker to let you actually touch a boob.
Actually, he already moved out and is rolling in the high-end prostitutes thanks to all the money he saved by not buying high end electronics.
Conclusion. Our MD simulations indicate that nanoporous graphene membranes are able to reject salt ions while letting water flow at permeabilities several orders of magnitude higher than existing RO membranes.
Whether it can be made to actually work and whether it scales is left as an exercise for the reader.
This is a Theory, not a fact.. No such Graphene membrane exists or has even been invented yet. All they did was run a computer simulation, and then say that it should work this way IF somebody can invent the membrane.
Just asking...
These things should be roughly interchangeable. The Water Online article gives a nice plot with "water permeability" in units of "L/cm2/day/MPa", showing a 2-3 order difference on a log scale. This is a slightly odd set of units, but essentially this is a flux/pressure applied. That is a pretty good metric for membrane performance. Pressure and area will scale with cost and energy in a roughly linear fashion; membrane technology is notorious for not enjoying economy of scale in the same way traditional operations such as distillation do. As this is a theoretical model, we don't know what additional costs and issues there might be in terms of auxiliary systems.
How much energy are we talking? For example, if the device is cheap and simple enough that each household could desalinate their own drinking water, would it be enough to have someone climb a ladder and sit on a sea-saw-like lever for a while?
This might allow more internal water recycling within industrial facilities like the Alberta Tar Sands, since the graphene filter could assure a high level of purity of the recycled water, as opposed to drawing more fresh water and discharging "within allowable limits" effluent.
The most useful substance never mass-produced.
I once took an excursion to Reddit, and later HN. Unlimited up/down voting sucks when dealing with a hive-mind.
Or we could use it to generate power
I'm a dreamer, the world is my playpen. But hey, I'm a serious person, I can't dream all the time.
If you can make it work as a simple sieve rather than reverse-osmosis, it would be nice if the energy of sucking upon a straw would make it work. And for larger scale processes, the energy of a gravity feed (like a 6-foot head of water) would be nice.
Bruce Perens.
where can I get a few sheet of that membrane?
It just struck me:
This is kind of like a Maxwell's Demon.
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.
I don't believe this is a linear relationship (without digging up a book, and I'm lazy today). Putting the first 10 PSI in a tire is easy, but the higher the pressure the harder it is to pump, and the more energy expended per unit of pressure.
So if there is a technology which requires super high pressure, and another which can get by fine with a low pressure, the L/cm2/day/MPa values may not be usable for comparison.
Even those who arrange and design shrubberies are under considerable economic stress at this period in history.
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
-- I ignore anonymous replies to my comments and postings.
Water water everywhere but ... wait a few seconds, let's drink!
All these slashdot posts about graphene, however I don't see a single realized application for this miracle particle...
Yeah.
This post expresses my opinion, not that of my employer. And yes, IAAL.
Basically, the regular atomic structure of graphene means that you can create holes of any size
Any size you want ... as long as it's this one.
...Its 1000 times as fast as previous reverse osmosis... so how fast /is/ reverse osmosis now? My friend the Google told me that current (well 1960's - 1980's reverse osmosis desalination plants) can produce just over 1 million cubic meters per day. 1000 x 1000000 cubic meters per day is 1000000000 cubic meters per day, which is also 1 cubic kilometer per day. That is a lot of water: 1 trillion litres, or 264.18 billion US gallons per day. One plant could (nearly) quench California's thirst.
When thinking of water filtration, a lot of you automatically conjure up a mental picture of a conventional water filter -- ie, dirty water poured from the top, and impurities get trapped in between, and clean clear water drips out from the bottom
In large scale water filtration operation, that traditional top-down model does not work
Instead, raw water is pumped into the inner tube of a double-layered pipe, which is slanted upwards, at a 30-60 degree angle
Sections of wall of the inner tube are made up of filtering membrane - such as Graphene
As the raw water flows upstream , and because of the smaller diameter of the inner tube , pressure building up inside the inner tube of the double layered pipe.
Because of the higher pressure inside the inner tube, molecules of clean water flows out of the inner tube, through Graphene (or other filtration membrane), into the larger pipe on the outer layer of the double-layered pipe
And because the pipe is slanting upward, gravity causes the filtered (clean) water in the outer pipe to flow down and eventually it gathers at a collecting point (usually a tank, or a pool) at the bottom
At the top of the double-layered pipe, there is an opening for the inner-pipe for the impure-water to exit
Because of the outlet, there is no need to do any "back flushing" since impurities, including salt, are continuously being flushed away
Hope this helps
Muchas Gracias, Señor Edward Snowden !
Article caused a popup asking to do a free check to speed up my PC.
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
Wouldn't you be filtering the water out of the hydrogen?
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
Besides desalinating water, it's easy to envision other uses. There's a lot of potentially valuable... I believe the technical term is "crap", floating around in water, being able to make water drinkable by filtering out NaCl is just the start. Imagine mining sea water or river water for valuable or poisonous metals, straining out microbes that are vastly larger than water molecules... there are other things you could filter too. Imagine how quick and easy it should be, using graphene with holes of appropriate size to take 5% or 7% alcohol, and ratchet the percentage all the way up to 100, simply by filtration. (This is assuming the alcohol or whatever is in the alcohol won't attack the graphene and make holes in it...) But maybe I'm just being optimistic. Guess we'll just have to wait, unless someone has some graphene and a bunch of lab equipment laying around, then we could all get together and play with it...
I wonder if there are any graphene workshop hackerspaces...
Wine makers have been modifying their wine to achieve a higher alcohol content.
This RO process might be one method in extracting the H2O molecule from the
C2H5OH. Hopefully in near future more good wine at cheaper price.
Just ell 'em brine return is needed to counter the "global saltwater diffusion problem" caused by that evil climate issue colloquially known as "rain."
Won't be long before people are signing petitions, lol.
If the graphene filter works, you could use it to filter seawater on a small scale in much the same manner as those filtered water jugs for people who don't like their tapwater. It might not sound like a big thing, but many a person trapped on a raft at sea has wished for his own pocket desalinization plant.
The big question is: can you make those matrices small enough so that only O2 molecules fit through the gaps? Because that would be even sweeter.
Is there nothing it can't do?
If graphene is 1k times more efficient than RO, is the waste 1k more?
Yes ,but is it cost effective to use
Jack of all trades,master of none
Why do the canisters become useless if you let them dry out?
I heard someone say this would still let dihydrogen monoxide through (its a small molecule), which is one of the most dangerous substances know to man. /sarc
Morton Salt in the US is mostly harvested from the Great Salt Lake in Utah
Morton Salt is MORMON SALT!
Isn't graphene the same stuff that pencil lead is made out of? Have they written off the possibility of lead poisoning?
The canisters don't... it's the membrane and substrate in the canisters that get pooched.
-- I ignore anonymous replies to my comments and postings.
They'd have enough salt to last forever!
It doesn't mean much now, it's built for the future.
Original poster here, dipshit. You obviously have several girlfriends making you happy right now, all because of your posting on slashdot. Bravo idiot!