New Process For Nanoscale Filtration Holds Promise of Cheap, Clean Water 116
New submitter Spinnakker writes "Lockheed Martin, traditionally known for its development of military systems and aircraft, has developed a process for perforating graphene (carbon sheets only one atom thick) that could potentially reduce the energy required for desalination by two orders of magnitude. The process tailors the hole size to the molecules being separated. In the case of desalination, one would create holes in the graphene large enough to allow water to pass but small enough to block the salt molecules. The advantage to using graphene comes from how extremely thin the material is compared to traditional filters. The thinner the filter, the less energy is required to facilitate reverse osmosis."
Holy moly (Score:5, Insightful)
I remember when this theoretical technology was proposed about a year ago, and figured it would be a decade before they could actually do it.
Cheap desalinization and filtration would mean an end to one of the biggest world health problems(safe drinking water), and could improve world-wide standards of living dramatically.
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It's very hard to keep prices up and maintain austerity measures if fresh, clean water becomes more abundant. Desalination seems like such a waste when we can collect, harvest, and distribute rain water. But low profit margins will keep that from happening. Making war and stealing other peoples' water is the market solution.
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we already do collect rain water
upstate NY the rain falls into lakes and rivers and then into the NYC water system
i don't think its feasible collecting rain water straight from the sky though
Re:Holy moly (Score:5, Informative)
i don't think its feasible collecting rain water straight from the sky though
Sure it is, people have been doing it for millenia: Brief Outline of the History of Rainwater Catchment Technologies [ernet.in]
Plenty of research is being conducted on modern approaches to rainwater harvesting. In the developed world these often come into conflict with environmental regulations regarding water quality, and in general there's a surfeit of water from other sources that is ran through central filtration facilities so no great press is on to tap rainwater as a major source. It's something popular with people who are interested in green tech and the like.
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we already do collect rain water
gp never said we didn't
We do use rain water (Score:1)
Here in Australia most of the households use rain water, I'm not even connected to the town water (and I'n not a threehugger...).
The idea initially sounded weird (I'm from Europe), but it works fine and the quality is excellent, without fluoride and other craps.
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I bet you are a lot of fun at parties:
"The punch is probably poisoned".
"You are just contributing to Big Liquor".
"I bet none of these girls really like me. They're just after my money"
"Did you know that Halliburton owns Frito Lays?"
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The problem with existing home RO is that the pressure available is low resulting in a lot of wasted water. Efficiency is maybe 15%. This may be a big help in that regard.
The other limitation with membranes is they are not sufficient for sterilization. Holes in the membranes plus the lack of residual action means additional treatment is needed downstream of the filter. This is not likely to address that issue.
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It would have to be a hole through several layers of membrane, but yes a mild standard treatment afterwards may be more than enough. This is hardly the expensive part of desalinization.
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Re:Holy moly (Score:5, Informative)
Holes in membranes are a fact of life. The reason they aren't crucial for desalinization is that you don't need ion free water for it to be potable. In fact it's common to add ions back in after desalination because pure water is much more corrosive than typical drinking water.
Disease organisms are a different issue altogether.
Post treatment growth of micro-organisms is a fact of life. Some sort of treatment with a residual action is absolutely needed. Usually this is chlorine or chlorine compounds. Maybe in a home system you can get away without it but certainly not in a municipal water system.
This isn't new knowledge folks. People have been doing this for decades.
http://www.fwrj.com/techarticles/1109%20fwrj_tech1.pdf [fwrj.com]
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But surely the biggest use of this technology is not for drinking water but for irrigation? Turning the desert into arable land...
Re:Holy moly (Score:4, Informative)
No bacteria would pass though due to size, so coagulation not necessary. Chlorination also not necessary.
So what does that leave, purification of certain compounds which happen to be smaller than H2O? (likely a mild chemical treatment process judging by other filtration techniques.) Since this is a desalination filter process seems safe to assume anything above Ng on the perdioc table would not pass through ( I am not a chemist by trade so please correct me if I am wrong). This leaves H He Li Be Bo C N O Fl Ne to be worried about from a chemical standpoint after filtration.
So what really is left after passing through graphene?
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Ach, anything above Ne* I mean (Boron just B, also Flourine is just F). Told you I wasn't a chemist, but not bad from memory.
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In practice, a fraction of the living bacteria can and do pass through RO membranes through minor imperfections, or bypass the membrane entirely through tiny leaks in surrounding seals. Thus, complete RO systems may include additional water treatment stages that use ultraviolet light or ozone to prevent microbiological contamination.
wikipedia
Re:Holy moly (Score:4, Informative)
what does that leave, purification of certain compounds which happen to be smaller than H2O. ... This leaves H He Li Be Bo C N O Fl Ne
He & Ne aren't a problem - 1) they're a gas, and He, at least, is sparingly soluble in water, so it'll all bubble off. 2) They're as inert as they get, so wouldn't make much of a difference even if they were in the water.
C N O - Aren't found as mono-atomic atoms. Will always be in larger molecules, which for the most part are larger than water.
H Li Be B F - Found as monoatomic species, but only as ions. With ions you always get a shell of hydration around them, and it's a significant amount of work to strip that away. Effectively, you don't have a Li+ on its own, you have a Li+(H2O)x complex, which by necessity will be bigger than a single water molecule
The only thing you'd be worried about are small, neutral molecules. Something like methane might be a problem, but if you have methane in your source water, you probably know it, and will have some other pre-treatment to deal with it specially.
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The only times methane in the water is a problem is when you burp while smoking or when the glass gets knocked out of your hand due to a gas bubble going through the water tap.
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downstream treatment can be very simple though, appropriate filter, heating to high enough temp for appropriate time but without boiling, etc.
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Downstream is truly the wrong word. The highest cost of desalination is, everywhere you want to use the water is going to be 'upstream' from it source. Most fresh water is used downstream from it's source less or no expensive pumping. Getting that water uphill is the real cost, pumping tons and tons of it, many kilometres inland and many hundreds of even thousands of metres uphill is the real cost problem. Cheap energy produces cheap water and low cost nuclear is still the best interim goal to producing lo
Re:Holy moly (Score:5, Informative)
It makes more sense to use this to filter out municipal waste water and re-use it for drinking water. It's right there where you need it, it's got less junk to get out than seawater, and there is less byproduct. The only problem with that is people don't like the idea of drinking their own sewage, even if it has been filtered well.
Not to be a wet graphene blanket: this is a very good thing, you're absolutely right that it will improve the standard of living worldwide if it pans out, and we do need better filtration technology. Just that we shouldn't forget the ecological concerns.
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1. put it back into the ocean
2. put it back into the ocean?
3. how about try to read the above again.
How difficult is it to actually think these days? You don't dump it with 2x salt contents. You dump it at 5% higher salt content or 1% higher salt content or whatever. Make a long pipe 2km long and dump it there.
What's the problem?
And please don't say "how you can do that when process outlet is 200+% salt content of input".
But if you really don't want to dump it back in, you can
1. make sea salt from i
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we shouldn't forget the ecological concerns.
Like that's going to happen.
We could flood the planet with the bodily fluids of armchair ecologists bitching about stuff using their Chinese computer hardware.
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The salt doesn't filter out, many places the underground aquifers are saline, we have a local pickle factory that has a brine well.
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Ummmm.... the ocean is big, really big, and whatever water a major city needs is a small consideration compared to evaporation. You could tap a supply for all of south Florida from a single point and still dilute it to harmless levels just by mixing your 200% brine solution with 10 parts of straight seawater before discharge. I suspect industrial scale desalination would discharge much more dilute brine than 200%, unless they were attempting to also harvest sea salts, anyway...
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I remember when this theoretical technology was proposed about a year ago, and figured it would be a decade before they could actually do it.
It would be fascinating to troll through the /. archives and find out what fraction of things that were predicted to come to market in timescale X actually did so. XKCD aside, I don't think this question has ever been properly addressed.
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I'd like to know, though, if it has any applications to dialysis. We really need an artificial kidney. For those who don't know how it works: when you're on dialysis, they only dialyse you enough to survive, not enough to feel like normal people feel. People on dialysis are permanently tired and feel sick, pretty much. There was a study where they decided to find out what it'd take and they dialyzed "the heck" out of their subjects -- running them 7 days a week for 8 or more hours IIRC. And guess what: that
Waterworld (Score:1)
How soon before I can pee into a Mr. Coffee and get iced tea?
captcha: profound
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> How soon before I can pee into a Mr. Coffee and get iced tea?
You could do that for McDonalds right now. Booya!
Q: What's the difference between roast beef and pea soup?
A: Anybody can roast beef!
Re:Waterworld (Score:5, Funny)
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I thought you run it through a horse.
Beer (Score:2)
Q: How do you turn a German beer into an American beer?
A: Filter it to get the raw sewage out, then refrigerate.
Re:expensive filter will get gummed up in no time (Score:5, Funny)
...how many holes?
Enough to fill the Albert Hall
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So they had to count them all, then.
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so that means each hole will be permanently gummed up with a single molecule? how many molecules of salt (etc) are there in a liter of water? how many holes? and how expensive are these graphene filters?
You back flush the filter like most desalt plants. The patent shows them using gravity as the pressure source and the only real power being the flush and filling the gravity feed tanks.
Wait a moment (Score:3)
I thought part of the problem with current desalination techniques was that it removed all of the salts making us have to go back and re-add a bunch of phosphates and whatnot that are found in fresh water sources and are somewhat expected/required by our and plant's biological functions. That is, we were making the water too pure to be used without additional processing. This sounds like that taken the next level, so how much more efficient can it really be if the process requires even more post-processing to make it usable?
Re:Wait a moment (Score:4, Interesting)
Yes you need to re-add minerals when you use this new filter for watering plants and properly hydrating the human body, but think about it. With this invention you get a filter that will pretty much last forever with no degradation as long as it is maintained properly, and you can get fresh water from the sea and toxic sources without having to use up a ton of energy and money. In the end this idea is win-win, just make sure to include the trace minerals before drinking.
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Again? (Score:1)
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Very similar article [slashdot.org] was published half a year ago. Is there something new now?
It's gone from "A group of MIT researchers" to "Lockheed Martin", the latter of which could actually make it commercially available.
Current technology is already efficient (Score:4, Interesting)
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Where's that energy currently coming from? I know nothing about desalination, but maybe better filters allow for purely gravity-fed tanks rather than some pressurized or multi-passed treatment system?
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Where's that energy currently coming from?
Casimir forces.
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My point is that it's not just the pure energy input. The mode will have an inherent efficiency.
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>The press release is culpably deficient in conveying this crucial distinction.
Significantly. Less maintenance on membranes, likely more re-usable. Less post filtration treatment. Lighter, smaller, faster, better.
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Possible explanations if they're actually citing laboratory results and not just blowing smoke for PR purposes:
1) Our current theory of filtration efficiency is flawed
2) Our current theory is inapplicable in this case due to some quantum level effects
Not that this is necessarily directly applicable, but a while back I read a study where researchers found that water in a container sealed with a multilayer graphene cover evaporated just as quickly as from an uncovered container - the water vapor molecules jus
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Are you talking about osmosis or reverse osmosis? There is a thermodynamic limit to the osmosis process, but reverse osmosis uses high pressure pumps and wastes lots of energy.
I'm not aware of any thermodynamic limit to reverse osmosis efficiency. Can you provide a link?
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Salt water has higher entropy than fresh water and salt separately. When separating salt water into salt and fresh water, entropy is therefore being decreased. This must be compensated by work from the outside. The minimal possible work needed is given by the difference in free energy between the initial and final state, independently of the method used to go between these states (the method will only affect how much energy above that minimum will be expended). When the start and end states are at the same
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And that's almost all there's to it. The energy demands for desalination don't include, obviously, the material and energy costs of filter media and their maintenance. The subject technology is all about reducing those.
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WOW! Enormous Consequences (Score:2)
If this turns out to be as good as it sounds, the financial and social impacts will be staggering.
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It's more likely to stop people from staggering.
Reverse osmosis (Score:2)
I had an under-the-sink reverse osmosis system (Ametek, no longer in business) more than 20 years ago. I bought it for some of the plants I was growing at the time (insectivores, epiphytes, etc.), but then I discovered that *I* liked the taste of pure water myself and my usage doubled. Those damned RO membrane cartridges were quite expensive, and I eventually stopped using it. It would be nice to see the technique revamped with graphene if it can lower the cost in general (since home RO never used electr
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Even that is considerably cheaper than in years/decades past. Last I checked they were $75 and lasted at most two years.
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Clean water is going to become a huge problem. (Score:3, Informative)
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But perhaps it will become cheap enough to take and desalinate water and fill up major rivers so that natural distribution can be restored. It would take a lot of energy to do it but with the two orders of magnitude cheaper maybe it would be cost effective?
So, as a practical matter, major rivers tend to run downhill - that is, the lowest end of the river tends to be at sea level, and the highest end at a significantly higher altitude (and often thousands of miles away). As they say, "Gravity sucks". So "fill up major rivers" involves, first, the energy necessary to desalinate the water, then you get to build a pipeline to the upper end of the river 1000 miles away, and then you can fill the river.
As an example, New Orleans might not be very happy with the
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Lake Huron is 577 ft (176 m) above sealevel, Superior is 600 ft (180 m) not 2000 ft.
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I've always though that plastics were a by-product of petroleum fuel - all this cheap plastic furniture is basically cast-off from the fractioning process, sure it could be used as fuel, but why not just sell it cheap to Little Tykes to make disposable backyard junk?
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It is an expensive proposition however to lay thousands of miles of pipe.
I take it'll be cheaper than to lay thousands of miles of oil pipe.
soon (Score:1)
so after we've got these water chips, stimpacks, we setup the vaults and wait out the inveitable nuclear winter.
so who'll thinks they'll be a vault dweller? and would you be willing to venture out for a new chip?
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??????
Can someone please explain to me what removing the salt from water has to do with global warming?????
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Abundant fresh water could mean an increase of vegetation, crops or otherwise. Plants sink carbon from the atmosphere. Atmospheric carbon is supposedly the cause of "global warming" which is supposedly bad.
Salt molecules? (Score:3)
Salt is a crystal formed by ionic bonds, there's no such thing as a salt molecule. They must be making holes small enough for a single sodium ion. Not sure why they need to tailor the holes for each chemical, though. Just make them a bit bigger than water molecules, right? Than I guess a second filter that's a bit smaller, to remove contaminants that are smaller...
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Na: 3 electron shells.
Cl: 3 electron shells.
O: 2 electron shells.
H: 1 electron shell.
and not only that (Score:1)
Each hole also has a Maxwell's demon standing guard.
Blood-Brain barrier (Score:2)
Once upon a time, asbestos was also considered a miraculous futuristic material with seemingly near limitless applications.
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Now that's just dumb. You mix it with seawater to dilute it, and dump it back into the ocean. That's all there's to it.