Apr
19
2013

TL9 Watch: molecular filters.

As Ken Hite noted last night on Twitter, this is kind of a big deal.

A defense contractor better known for building jet fighters and lethal missiles says it has found a way to slash the amount of energy needed to remove salt from seawater, potentially making it vastly cheaper to produce clean water at a time when scarcity has become a global security issue.

The process, officials and engineers at Lockheed Martin Corp say, would enable filter manufacturers to produce thin carbon membranes with regular holes about a nanometer in size that are large enough to allow water to pass through but small enough to block the molecules of salt in seawater. A nanometer is a billionth of a meter.

It may be a while before we see the stuff from Lockheed, though: turns out that there are production issues with making a sheet that’s literally one atom thick (which I assume means that the stuff is both effectively invisible and barely existing in the space-time continuum). Who knew?

Moe Lane

5 Comments

  • Crawford says:

    Is a salt ion really bigger than a water molecule? Chlorine only has one more “shell” (I know — those aren’t real) than oxygen, and water is just oxygen with a couple of hydrogen Mickey-ears…

    • sicsemperstolidissimum says:

      Vague memories and guesses. IIRC, table salt, NaCl, goes to Na+ Cl- in solution. Fl should be a bit bigger than an Oxygen. IIRC, Fl- is bigger than Fl. (More negative per same positive means the negatives are more loosely held.) Cl- is again, bigger than Fl-.
      .
      Shells were used to describe orbits, IIRC, and what I learned might not yet be entirely obsolete. Wouldn’t it be two shells, plus some spare electrons?
      .
      If it stops the Cl- and other such, the Na+ should stay on that side, due to electrical charge, neglecting conductors. (Do we know if this stuff insulates? I wonder if this would allow for anything special in the way of batteries.)

  • acat says:

    Now that’s interesting.
    .
    I wonder how sharp the edges would be…
    .
    That said, if Cali stops drinking the Colorado River dry, yeah, that gets all kinds of interesting.
    .
    Mew

    • sicsemperstolidissimum says:

      Likely pretty sharp. The knives made for scientific purposes that have edges like that tend, IIRC, to be both very sharp and very delicate. On the other hand, maybe it flops around so much that it is like cutting your finger on a bolt of cloth.

  • sicsemperstolidissimum says:

    Dunno about the invisibility. I really know very little about the optical properties of such materials. I’d think that depending on what the specific properties are, it might well be visible.
    .
    Totally exists in space-time, if they can make it.
    .
    The strength they mention is important. With pure on one side (neglecting the smaller contaminants), and impure on the other, there will be an osmotic pressure across the filter. With pressure, it becomes easier to tear, I guess, and enough will burst it.
    .
    Limits on the system flow will include size of filter (limited by some combination of manufacturing technique and material strength), the pressure that can be put across the filter without tearing, and the holes per unit area. Without knowing more about these, we won’t for sure know flow rate per unit power per unit investment.
    .
    I hardly know anything about existing solutions.
    .
    Anyway, until the engineering is done, and the things can be manufactured, we won’t know about maintenance, oversight, parts and supplies, and so forth. I don’t know that we can say much about how revolutionary it is until somebody has that information.
    .
    That said, where tech advancement is concerned I have expectations towards the conservative, hedge my statements, and expect to eat a fair amount of crow. Maybe on this one, maybe not, but certainly many more times in the future.

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