Making Salt Water Drinkable Just Got 99 Percent Cheaper

Access to steady supplies of clean water is getting more and more difficult in the developing world, especially as demand skyrockets. In response, many countries have turned to the sea for potable fluids but existing reverse osmosis plants rely on complicated processes that are expensive and energy-intensive to operate.

Good thing, engineers at Lockheed Martin have just announced a newly-developed salt filter that could reduce desalination energy costs by 99 percent.

The Reverse Osmosis process works on a simple principle: molecules within a liquid will flow across a semi-permeable membrane from areas of higher concentration to lower until both sides reach an equilibrium. But that same membrane can act as a filter for large molecules and ions if outside pressure is applied to one side of the system. For desalination, the process typically employs a sheet of thin-film composite (TFC) membrane which is made from an active thin-film layer of polyimide stacked on a porous layer of polysulfone. The problem with these membranes is that their thickness requires the presence of large amounts of pressure (and energy) to press water through them.

Lockheed Martin's Perforene, on the other hand, is made from single atom-thick sheets of graphene. Because the sheets are so thin, water flows through them far more easily than through a conventional TFC. Filters made through the Perforene process would incorporate filtering holes just 100nm in diameter — large enough to let water molecules through but small enough to capture dissolved salts. It looks a bit like chicken wire when viewed under a microscope, John Stetson, the Lockheed engineer credited with its invention, told Reuters. But kilo for kilo, its 1000 times stronger than steel.

"It's 500 times thinner than the best filter on the market today and a thousand times stronger," Stetson explained to Reuters. "The energy that's required and the pressure that's required to filter salt is approximately 100 times less."

Lockheed is reportedly already ramping up production efforts for the filters — and trying to find a way to keep them from tearing — though there are no announced plans on when they'd hit the market. Tomorrow isn't soon enough. [Reuters via MetaFilter - Wikipedia]

Image: Shutterstock/Lightspring


Comments

    Oh, dont we wish we had discovered this before the Wonthaggi desalination plant!

      You said it! We will be paying for that elephant for the rest of our lives...... Ah the short sighted ness of our fearless leaders!

        I'm sick of people bad mouthing the desal as short-sighted. We're lucky that we've come out of the drought and don;t need the desal water, but when it was commisioned things were looking bad,

    There seems to be a lot happening with graphene. I can't wait for the graphene battery to be mass produced.

    and trying to find a way to keep them from tearing That's a big problem to solve right there. Graphene may be far stronger that steel but at one atom thick it's still going to rip easily. Just think Spider Web, it's far stronger than steel too but you can tear it apart real easy. Don't start buying stock just yet.

    Last edited 17/03/13 12:20 pm

      Yeah I guess in their testing they were generating 1 or 2 millilitres of pure water a minute... Still there's a promise of better. Maybe a graphene net could one day "catch" water from the humidity in the air?

      I was about to post the same thing.

      It's a bit like saying ''We have developed fantastic new rocket propulsion technology! Now we are trying to find ways to stop it exploding on the launch pad.''

      :-|

      Graphene is weak under certain circumstances.. It's more of a manufacturing problem than anything to be honest.. Things like making sure the liquid is at a constant, uniform pressure with no air bubbles or anything, add or minus probably a few other thousand design considerations.

      Still got a long way to go but exciting stuff, could put an end to poverty ^_^

    Graphene is awesome, but when it flakes, it can be a health hazard like asbestos if inhaled
    Can't imagine graphene nanoparticles in your gut are going to come out either

    Also, wouldn't the filter get clogged with salt particles really quickly?
    Guess you'd need two jets of water, one to encourage water to go through the filter, and another perpendicular to flush salt particles out of the filter

    They'd have to stack graphene sheets on top of eachother for strength, but getting the filter holes to line up would be challenging

      All of the small scale RO-filters I've encountered have had a backwash system where everytime the filter's performance starts to drop some of the purified water gets run through it in reverse to wash out the contaminants and then dumped. As I understand it this is also how large de-sal plants work which is why everytime one gets built there is a big arguement over where they should put the outflow pipe to dump all of the super-saline water from the backwashing process.

      Also, current filers are already made of many sheets stacked together. Having them all together means each sheet is like a safety harness for the one next to it so they don't just tear strait though.

      Interesting claim about the health risks. Do you know of any research which backs that up?

    I'm guessing of course, but with lower pressures you can just cycle sea water. It goes up to a tank, then dribbles down a pipe. The pipes have slots with the new filter material, and gravity forces SOME water through the filter. With enough flow, the slightly [saltier] water gets returned to the ocean.
    It's only when you want Every Last Drop of fresh water extracted, that you run into problems. And you usually want that to maximise the return for your energy expenditure.

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