New Process For Nanoscale Filtration Holds Promise of Cheap, Clean Water

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."

Re:Holy moly

[Zeromous]

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?

Re:Holy moly

[Ol Biscuitbarrel]

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]

Archaeologists found a sophisticatedrainwatercollection and storage system on the island of Crete while working on the reconstruction of the Palace of Knossos (1700 B.C.). However, with the development of building construction based on new materials such as lime and burnt clay bricks, new construction techniques like arches and domes developed. The ancient Romans became masters inrainwaterharvesting and the construction ofreservoirs. It was this new technique of building closed cisterns, and at the same time the urbanization within the Roman Empire around the Mediterranean, which resulted in the development of arainwatercatchment culture at all those places where water resources were limited. This is why oldrainwatercisterns are to be found on the islands of Capri and Malta and at places of historical interest in Spain and Turkey, in the Lebanon and on the island of Sicily.

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.

Re:Holy moly

[interkin3tic]

Yes, but we still need to figure out the other half of the problem of desalination, which is what to do with the high-salt brine. If you get 50% efficiency, as much water as you get out, you'll get out wastewater with 200% salt in it. In large volumes, you obviously can't store it or evaporate it off fast enough. Dumping it into the ocean will kill anything near the exhaust. And then there's still the problem of piping the water to cities.

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.

Clean water is going to become a huge problem.

[wanfuse123]

We have been polluting the water ever since the industrial age began and draining the water supply at the same time. Aquifers are getting depleted, its going to become an expensive problem. It is good to see this technology finally come about . It should help us bring water to arid lands. They say that with global warming it isn't the heat that is going to affect the plant life but the lack of water supply. It is an expensive proposition however to lay thousands of miles of pipe. 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? I would also suggest that we stop polluting the water with all the plastics and use it to recycle. We produce 37,000,000 tons of plastic each year that ends up in landfills and in the water. We could convert this into fuel energy. I have done a cost analysis on the energy from plastic recycling [rawcell.com].

Re:Holy moly

[the eric conspiracy]

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]

Re:Holy moly

[Anonymous Coward]

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.