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New Nano Desalinization Method
lbmouse writes "The Technology Review is reporting that researchers at the Lawrence Livermore National Laboratory have announced a way to use carbon nano-tube technology to reduce the cost of desalination of ocean water by 75 percent over current methods of reverse osmosis. From the article: 'The technology could potentially provide a solution to water shortages both in the United States, where populations are expected to soar in areas with few freshwater sources, and worldwide, where a lack of clean water is a major cause of disease.' The technology may also lead to new ways of eliminating carbon dioxide emitted from power plants."
Now, as sea levels rise, we can just drink it up.
Woo-Hoo!
Just think of the patent licensing fees they can charge!
That's "Mr. Soulless Automaton" to you, Bub.
If your short of drinking water in the US.. stop watering your lawn...
We'd probably call it vaporware
This could solve all the UK's problems with our current drought! An island nation, somehow surrounded by water, it sounds like it could be a great way to give us plenty of water to drink.
Although Thames Water fixing all the leaks could also be a huge help...
- Do you realize what this would mean to the starving nations of the planet?
- WOW! They'd have enough salt to last forever!
Cool work nevertheless. I wish they could do something with silicon nanowires as silicon is the second most abundant element on earth.
Where are these US water shortages? Broadband in the US may suck but I wasn't aware of any water rationing.
Also, this micro fluid dynamics intrigues me. Increased flow rate at reduced diameters. Very cool. Sounds like a possible research field for the old PhD.
I've heard it said that materials science is the slowest science - and it's almost certainly true. It is taking forever to get consumer products from carbon nanotubes (with a few exceptions).
But all the uses found for a new material and all the new applications discovered - in many respects it certaily seems to be the most fruitful science (at least in the engineering and day-to-day sense).
My Computer Music Tutorial Videos
I was wondering how I was going to get all that salt out of my iPod.
If you mod me down, I shall become more powerful than you can possibly imagine.
When I first read the headline I was wondering how iPods got salty in the first place.
The days of the digital watch are numbered.
Cheap Drinking Water from the Ocean
Carbon nanotube-based membranes will dramatically cut the cost of desalination.
A water desalination system using carbon nanotube-based membranes could significantly reduce the cost of purifying water from the ocean. The technology could potentially provide a solution to water shortages both in the United States, where populations are expected to soar in areas with few freshwater sources, and worldwide, where a lack of clean water is a major cause of disease.
The new membranes, developed by researchers at Lawrence Livermore National Laboratory (LLNL), could reduce the cost of desalination by 75 percent, compared to reverse osmosis methods used today, the researchers say. The membranes, which sort molecules by size and with electrostatic forces, could also separate various gases, perhaps leading to economical ways to capture carbon dioxide emitted from power plants, to prevent it from entering the atmosphere.
The carbon nanotubes used by the researchers are sheets of carbon atoms rolled so tightly that only seven water molecules can fit across their diameter. Their small size makes them good candidates for separating molecules. And, despite their diminutive dimensions, these nanopores allow water to flow at the same rate as pores considerably larger, reducing the amount of pressure needed to force water through, and potentially saving energy and costs compared to reverse osmosis using conventional membranes.
Indeed, the LLNL team measures water flow rates up to 10,000 times faster than would be predicted by classical equations, which suggest that flow rates through a pore will slow to a crawl as the diameter drops. "It's something that is quite counter-intuitive," says LLNL chemical engineer Jason Holt, whose findings appeared in the 19 May issue of Science. "As you shrink the pore size, there is a huge enhancement in flow rate."
The surprising results might be due to the smooth interior of the nanotubes, or to physics at this small scale -- more research is needed to understand the mechanisms involved. "In some physical systems the underlying assumptions are not valid at these smaller length scales," says Rod Ruoff, a physical chemist and professor of mechanical engineering at Northwestern University (who was not involved with the work).
To make the membranes, the researchers started with a silicon wafer about the size of a quarter, coated with a metal nanoparticle catalyst for growing carbon nanotubes. Holt says the small particles allow the nanotubes to grow "like blades of grass -- vertically aligned and closely packed." Once grown, the gaps between the nanotubes are filled with a ceramic material, silicon nitride, which provides stability and helps the membrane adhere to the underlying silicon wafer. The field of nanotubes functions as an array of pores, allowing water and certain gases through, while keeping larger molecules and clusters of molecules at bay.
Holt estimates that these membranes could be brought to market within the next five to ten years. "The challenge is to scale up so we can produce usable amounts of these membrane materials for desalination, or gas separation, the other high-impact application for these membranes," he says, adding that the fabrication process is "inherently scalable."
Eventually, the membranes could be adapted for a variety of applications, ranging from pharmaceuticals to the food industry, where they could be used to separate sugars, for example, says co-author Olgica Bakajin, a physicist at LLNL. "Practically, the next step is figuring out how to take a general concept and modify it to a specific application," Bakajin says.
"There are many studies that one can imagine to build upon this study," says Northwestern's Ruoff. "Our understanding of molecular processes will be helped by experiments of this type. There are interesting possibilities for nanofluidic applications, such as in nanoelectromechanical systems and in 'smart' switching [on and off] of the flow through such small channels."
"You should never doubt what nobody is sure about." -- Willy Wonka
The article doesn't say how much waste water would be needed to de-salinize a given volume of H20, but if the water flows through with considerably less force than a traditional RO unit maybe there will be less waste water. This could be more important than the energy savings. A good comercial RO filter produces roughly 1 gallon of waste water for every gallon of potable water, and most home units produce two or more.
The challenge is not about methods to desalinize (there's plenty of methods), it's about finding a method which requires very little energy (and thus money) that it becomes advantageous to proceed to desalinization in the first place...
Animoog.org
I once read something about a class of fractals called >orchids.
They are the result of monitoring crowd flow dynamics and producing the formulas.
They too noticed that for a large crowd (concert, football match) crowd flow speed INCREASES with a number of small gates rather than one large gate, hence one by one through the turnstyles actually makes the process quicker.
This appears to be a similar unintuitive process.
Anyway, I know it wasn't totally on topic I just thought I would share.
liqbase
I wonder if it will also sterilize any water passed through it, as carbon nano tubes seem to evoke cell death upon contact. This is one area where that could actually prove to be a benefit rather than a set-back.
Just being able to desalinize water cheaply is a pretty damn big breakthrough though, I know Los Angeles could use it with all the draughts they have. I mean how ironic is it that they'll have a 7 year drought and water shortages, and yet be right on the coast of the largest body of water in the world?
Go ahead and call me unreliable; reliable is just a synonym for predictable.
Think of the other ramifications, one of the huge problems with cracking hydrogen from water is getting pure enough water to start with. If you can cut the cost of desalination significantly, you can reduce the total cost of hydrogen production.
-Rick
"Most people in the U.S. wouldn't know they live in a tyrannical state if it walked up and grabbed their junk." - MyFirs
This new method should only require pumps. From your description of condensation it requires temprature differentials. That will require power input as well as the pumps.
It may be more efficient (and cheaper) by simply being, well, simpler.
The obscure we see eventually. The completely obvious, it seems, takes longer. - Edward R. Murrow
Just as current wars are fought over oil, wide predictions are that future ones will be fought over access to water resources.
1) Why do they bother calling it "reverse osmosis?" From a quick review of high school biology, I have come to realize "reverse osmosis" really means "pumping through a filter."
2) I saw this other method in Discover that I really liked. Basically, it proposes using deep water and methane to flash-freeze water. All you need to do is to pump methane into water of the right depth, and it instantly freezes into that flammable ice mining rigs love to dig up and play with, without like, refrigerating it. Anyways, as it freezes, all the salt gets pushed out and it floats to the top, so all you have to do is melt the ice and reuse the methane. It appealed to the recycler in me, and it seems to me some tubes and plumbing would be easier than nanotubes, eh?
Google: "All your data are belong to us."
Recent analysis of the test used,the methylthiazol tetrazolium (MTT) test shows that the test may have been screwed up by the fact that the MTT was binding to the nanotubes. Using a different toxicity test, NO toxicity was found.
Based on this, carbon nanotubes should probably be considered cleared of causing cell death for now.
Inconvenient for your filter, but a boon for many many other applications.
-- perl -e'print pack"H*","6e656d6f406d38792e6f7267"'
What I never understand with these kind of filters is where the waste ends up. There is quite a lot of salt in the water, so these filters should clog pretty quickly, and just rinsing them every minute does not seem to be very practical. Does anyone know how this works?
Then you won't have to desalinize it
I am hard pressed that anyone living where there is normal rainfall for growing grass (i.e. Georgia) and has a water table high enough to tap with a private well isn't simply recycling the water by pumping it from below and discharging it on the surface. In fact, ground-source heat pumps are the next big thing in saving energy resources -- some of the systems are closed loop with a coil to pipe in the ground, other systems are open loop, lifting water from a well and discharging it on the surface. The various state DNR's that issue permits for such open loop systems want you to discharge on the surface -- they certainly don't want you pumping water that you have handled directly back into the aquifer without being filtered through the ground.
I agree that lawn watering is a serious use of resources in the desert Southwest U.S. You can be Fremen in your view of lawns on Arrakis, but to argue the same point on Caladan is stretching matters a bit far.
I really am looking forward to batteries lasting 100x longer, nanopaper and this latest discovery. I just have absolutely no read on how far we are out on practical implementations of this technology.
That ocean water scheme is taking much lower grade heat, thermodynamically, than the energy in Diesel fuel, but it still requires 1000 BTU's of heat per pound of water (8000 BTU's per gallon). That is a lot of heat to take out of the environment, and a lot of heat to transfer.
Another way for more efficient desalination is to recycle that 1000 BTU/lb -- use 1000 BTU to evaporate a pound of water to purify it and then condense that water vapor to get back that heat to evaporate more water. Trouble is that water condenses at the same temperature it evaporates, and you need at least a small temperature differential to get heat to flow downhill.
There are two approaches to recycling the heat. One approach is multi-effect distillation. You evaporate at a higher temperature and pressure, and then condense at that same temperature, which you use to evaporate other water at a lower temperature and pressure in a vacuum chamber. You have a cascade of evaporators at successively lower pressures and keep reusing the same heat. This method was developed by Norbert Rillieux, the Louisiana son of a French engineer and an American former slave, and is widely used in food preparation -- sugar from cane or beets, orange juice concentrate, and so on.
The second approach is vapor compression. You boil at one temperature, but you condense at a higher temperature by compressing the vapor to a higher pressure using something akin to an automotive supercharger driven by an electric motor, and that way the heat from condensing at a slightly higher temperature and pressure is recovered by the evaporator. This requires only a single "effect" on account of the vapor pump instead of the multi-effect cascade into successively lower pressure chambers, but it needs the electric motor and vapor pump, and you need to move a lot of heat at low temperature differentials across large surface area plate heat exchangers.
Reverse osmosis is a pure mechanical process that doesn't require exchange of the 1000 BTUs per pound of water, but the osmosis membrane offers resistance to pumping in excess of the natural osmotic pressure (the pressure differential required to overcome the salinity differential, the PV work representing the true thermodynamic cost of desalinating the water, which is much less than the 1000 BTU's per pound). By the way, it is always more cost effective to desalinate slightly-salty (brackish) water from marshes or irrigation runoff or other sources than going for the highly-salty sea water on account of the energy inherent in the dissolved salt as reflected in the higher osmotic pressure).
It reminds me of the contention between regardless and irregardless. Yeah, I hate irregardless too.
My first thought was much more sinister.
Steve
A work that expires before its copyright never enters the public domain and thus enjoys eternal copyright protection.
Could this be used to filter water from urine? That might come in handy in survival situations, or in closed environments such as habitable space modules. Or simply for weirdo geeks.