Making Saltwater Drinkable With Graphene 303
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."
A foul subject. (Score:5, Interesting)
So how durable is this membrane when it comes to dealing with impurities?
Why stop at salt? (Score:5, Interesting)
Re:Holes? (Score:5, Interesting)
A couple of people have raised this issue, and it relies on a fundamental mis-understanding of how the universe works on a molecular scale.
Suppose that I have my colander and I wash some vegetables in it. Gunk can get stuck in the holes and it has to be washed off, which requires a fair amount of work because I have to break the interaction between the gunk and the surface. That's your macroscopic intuition about how filters and such work.
But your macroscopic intuition will lead you astray in this case. The individual holes in graphene do not work that way; yes, occasionally, molecules of one kind or another will spend some time stuck to the graphene (a useful phenomenon in other circumstances - http://en.wikipedia.org/wiki/High-performance_liquid_chromatography [wikipedia.org]) but, on the scale of atoms, they are effectively in a high-powered washing machine ALL THE TIME.
Can't find quite the movie I want... this'll do:
http://protonsforbreakfast.wordpress.com/2012/04/11/brownian-motion-observed-in-milk/ [wordpress.com]
So you see those oil bubbles wiggling around? Given that amount of constant wiggle, are you worried about having them "stuck" anywhere? That's thermal vibration from being at room temperature. Those milk bubbles are over 1,000 water molecules across, so each of those "wiggles" is 10 or 100 times the size of an individual graphene pore; are you worried about anything another 1000x smaller being "stuck" anywhere? It would be like worrying about gunk stuck in your colander while your colander was sitting in a fire-hose 24/7.
Anyway- to cut to the chase:
obviously you could have you take the graphene and you run the sea water *past* it at high pressure. Occasionally some gunk gets in there but it washes away sooner or later; and nothing spends any appreciable amount of time stuck in an individual graphene hole.
Re:Why stop at salt? (Score:5, Interesting)
Re:Why stop at salt? (Score:5, Interesting)
The standard of living in the 3rd world would go up dramatically with free access to clean water.
There's a trend towards decreasing access to freshwater in many developed parts of the world as well. Much of the southern United States will be uninhabitable within our lifetimes if they do not secure another source of fresh water. I do not think just the '3rd world' has this problem. We will all be '3rd world' if the trend continues. And then no world... because almost all life on land depends on it.
Re:Why stop at salt? (Score:5, Interesting)
Much of the southern United States will be uninhabitable within our lifetimes if they do not secure another source of fresh water
yet if you mention this to people who live there they go absolutely bonkers denial on you. I guess I'm not speaking about the small minority who will profit from doing the math.
Uhmm....I sense a problem with scale. (Score:5, Interesting)
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.
Re:Holes? (Score:4, Interesting)
Oh please. For one thing, we already have desalination plants in some places dumping brine back into the sea; obviously it's not a big problem. There's a lot of water in the oceans. Secondly, the highly concentrated brine from these graphene filters could potentially be valuable for harvesting sea salt. We already have giant sea salt plants, where basically ocean water is left to dry out so we can take the salt out; between humans taking sea salt and leaving the water, and taking water and leaving the salt, I don't think there's any net effect on the oceans. And these graphene filters could make sea salt harvesting potentially more efficient.
Re:A foul subject. (Score:5, Interesting)
Re:Why stop at salt? (Score:5, Interesting)
Re:Why stop at salt? (Score:5, Interesting)
Re:Holes? (Score:4, Interesting)
In that case it is easy. The solution to this pollution is dilution.
I find it so funny how Slashdot seems to be a bastion of anti-tech these days. Many of the issues "Flamable drinking water" actually seem to predate actual fracking. Any contamination of drinking water must be taking place on the down pipe and not the actual fracking zone since natural gas is found below the water table and not above. So the big problem seems to be simple pipe failure which is something that can be fixed. Of course the EPA should regulate the ingredients of the fracking fluid but over all the fear factor on Slashdot is very disappointing. Frankly it almost seems as if coal companies are paying people off for this.
Re:Holes? (Score:2, Interesting)
except this is only a simulation, done on a computer. i don't yet see anyone hydrogenating graphene at a sustainable plant, that doesn't simply let us build las vegas style resorts with water they planned to go to farms in the desert.
and who will run those farms, giant corporations that squeeze every dollar they can out of 'indentured servants'(contract slaves)
what happens when we reach the breaking point? because there is a breaking point. the math of how science can change the world has proven to me that every generation is going to have it's dissenters, and every set of leaders is going to have thier own corruption. so lets say we can build cheap fast desalination to grow pinapples in the desert, (instead of agave) we still have problems to solve. let us say someone gives me $20 million to build one of these desal plants and it works, if it's not run by the government the water will go where the free market dictates and that is human consumption. so it makes the problem worse, not better. and if the government does it, it will be super expensive, so who do we get to do the feasability study and if it works roll it out? wont more food choices make more sick humans with closer epidemic possibilities?
cheap desal research it i like the idea, but it is only one resource and there are many problems besides water resources. there are equasions that never change that apply universally that just plain work. i don't store those equasions except as books and movies, but it took me a good 32 years to realize i wasn't following a path to sustainable happiness.
Re:Why stop at salt? (Score:5, Interesting)
Nonsense. Less than 1/4th of all fresh water goes to domestic use. First, other southern states will start adopting some of California's water conservation methods, like low-flow fixtures (toilets, shower-heads, large-drip sprinklers, leech lines), and then it'll escalate to cutting off of ornamental fountains, and disappearing lawns. In the longer-term, grey water systems will be put in-place, and municipalities will be more inclined to supplement groundwater with recycled (sewer) water.
That's just mind-numbing... This is just a method to make desalination CHEAPER. And desalination is just one method of water filtration and reprocessing. My $10/mo water bill going up, even drastically, will have practically no effect on me, while it will make gathering other water sources, and more aggressive processing methods become economical for municipalities... It's good old supply and demand.
Some people pay more per-gallon for water than they do for gasoline, thanks to "bottled water", so we can obviously afford a higher price here in the first-world.
Re:Holes? (Score:5, Interesting)
Actually, as with most situations where humans dump heaps of something somewhere without worrying about the consequences too much, the buildup of salt in the ocean potentially can have significant harmful effects on sea life.
This is a major issue near where I live at the moment - we have no water (driest state in the driest continent on Earth) so we are keen on desalination, but the planned desal plant may kill a unique local form of giant cuttlefish because we are going to pump heaps of salt into a gulf that doesn't flush out quickly:
http://www.abc.net.au/news/2007-04-16/cuttlefish-at-risk-from-desalination-plant/2243198 [abc.net.au]
I guess it'd like fish deciding that pumping a few percent of extra CO into the local atmosphere won't be a problem for us because the atmosphere is so big. At a certain point you don't want to be too near the outlet.