Slashdot Mirror
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."
If they've found a way to desalinate water with much less energy, practically, that's huge.
Bruce Perens.
Surely it won't last forever, but the membrane lifetime could be extended by using normal filters to retain impurities, and let the graphene deal with pure saline water. Maybe the graphene filter can be cleaned a couple of times and be reutilized.
This is only a guess by RO filters have two things that take power. They require a high pressure differential across the membrane which makes for expensive pumps, piping and electric bills. Also they have a lot of bypass water which wastes energy by making you bring it up to pressure and then just dump it out.
If this membrane requires less pressure and less bypass it will significantly reduce both the capital costs and operating costs of such a system.
I love Jesus, except for his foreign policy.
All of those would be larger molecules than H20, don't you think? This is a pretty cool discovery/invention.
The cesspool just got a check and balance.
I agree,getting salt out is fine, but, fishy smell, fish pee, industrial pollution (mercury 'n'such ).
Err, no one does that... Seriously. Fishy smell? Fish pee? wtf??
Mercury is not toxic much anyway, unless it is in organic forms.
But then on the plus side, if Uranium cost were > $350/lb, it would be economical to mine Uranium from sea water. It doesn't mean this concentration is toxic for you.
Where I live, most of the water is from a lake, with fish pee and moose pee all mixed in together. haha
Water Molecule: 275 pico-meters
Ecoli Bacteria: 0.6 micro-meters (109,000x larger)
Rhinovirus: 30 nm (110x larger)
You sell it as fancy eco-friendly sea salt for $15/lb.
"[Regarding the 'cloud,'] ownership was what made America different than Russia." -- Woz
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.
the highly concentrated brine from these graphene filters could potentially be valuable for harvesting sea salt.
The concentrated brine could also be useful for generating electricity. Demand for desalinated water is highest in warm, arid regions with plenty of sunshine. So here is what you do:
1. Pump seawater through the graphene filter to separate it into fresh water and brine.
2. Move the brine into evaporation ponds, to concentrate it even further.
3. Generate electricity using the electric potential between the brine and regular seawater
4. Use some of the electricity to power step #1, sell the rest.
5. Profit!
Basically, this is a cheap way to collect solar energy (the sunshine falling on the evaporation ponds) while generating fresh water in the process.
Keep in mind that this process is regarding desalinization, not water purification. I'm sure if graphene solves the problems of desalinization, it will work wonders with purification, but there are adequate water purification systems located in most places, but water desalinization is a massively expensive procedure in comparison.
A robust and cost effective desalinization system is literally one of the biggest necessities we're going to need in the next century, as average rainfall levels continue to fall all over the U.S.
I know it may be impractical but I see giant desalinization inlets from the ocean leading to a network of irrigation and river systems for the West coast.
My kingdom for a donkey!
Also keep in mind that DRINKING water (fish pee smell) is not the big issue. People will pay $4 for 350 mls of brand-name water purified from tap water due to marketing and consumers being illogical. Agriculture is the bigger issue. Increasing water costs a few cents per gallon would have major consequences for agriculture, subsidies from the government would have to be substantially increased. Fortunately, it need not be purified as much as drinking water does. If running it through a graphene filter desalinates water to the point of being useful for agriculture but not pure enough to drink, the problem is still solved.
It's been pointed out that the most efficient way to do things would be to recycle city waste water for drinking water, since it's more free of some contaminants like mercury, and, more to the point, is already at the point where we'd need it. Piping drinking water from the ocean just to piss it into a river is hugely wasteful.
The biggest impediment to that is the ick factor you just brought up: if the idea of drinking water that had fish urine removed from it, people are going to throw a hissy fit before they'll drink water recycled from their own pee.