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New nanotech-based filtration could save buckets of energy.

Seawater desalination is no easy task. Traditionally, vacuum distillation techniques have been used, and this process requires a great deal of energy. More recently, reverse osmosis facilities have come online. These facilities use a special permeable membrane to separate salts and minerals from liquid water. As of January, there are more than 13,000 desalination plants pumping out over 12 billion gallons of water a day.

While cogeneration facilities have helped to cut down the cost of vacuum distillation and reverse osmosis plants are marginally more efficient in terms of energy used, work in the unrelated field of biology and molecular transport systems may promise an even better type of filtering membrane for osmosis systems.

Researchers at the Lawrence Livermore National Laboratory, while studying the process of molecular transportation across cell membranes, have come up with a new type of filter. The filter mimics the properties of cell membranes and is especially efficient in the transport and filtration of water molecules. Their work is based on -- you guessed it -- carbon nanotubes.

What makes these CNT-based filters so efficient is their hydrophobic properties, or the way they repel water molecules. Water moves through the CNT channels in a membrane much more quickly than in conventional filters because the molecules do not stick to the sides of CNTs. Instead, they stream through them unhindered, like a bullet train.

After this discovery, the researchers tested their artificial membrane for desalination efficiency. They found that the 1.6nm diameter tubes successfully prevented the ions that make up salts from traversing while letting the water molecules flow freely. The mechanism for this selectiveness lies in the small diameter of the channel along with the charge held at the end of the nanotubes.

Aleksander Noy, a senior member of the LLNL research team explains, “while carbon nanotube membranes can achieve similar rejection as membranes with similarly sized pores, they will provide considerably higher permeability, which makes them potentially much more efficient than the current generation of membranes.”

While the LLNL findings promise a great deal for desalination and other processes where similar filtering is used, some refinement will still be required. The ability to construct membranes of different materials and control the charge and diameter of the nanotube pores will weigh heavily into their efficiency and usefulness in different applications.



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CNTs in 30 years
By djc208 on 6/10/2008 9:28:37 AM , Rating: 2
I'm fascinated by all the cool things scientists are doing with these carbon nano-structures but I can't help but feel that they have the same hype today that you saw with Nuclear power back in the early days. All these SF stories of nuclear powered wrist watches and refrigerators and how energy would be too cheap to even charge for.

I have no doubt we will find many good uses for CNTs and other similar structures (just like nuclear power) but the other shoe has yet to drop on these things. We've seen some concern over toxicity but I don't think we've had the real rain on this parade yet.




RE: CNTs in 30 years
By TheSpaniard on 6/10/2008 10:04:18 AM , Rating: 2
the concern over toxcicity has been mostly muted because of the usage.... but you see all those asbestos exposure lawyers? imagine what will happen when people start to realize

OMGZ CNTs CAUSE CANCER!!!

with that being the favorite illness to freak out about... I don't know if that itself will rain on the parade


RE: CNTs in 30 years
By masher2 (blog) on 6/10/2008 10:07:03 AM , Rating: 2
> "All these SF stories of nuclear powered wrist watches and refrigerators and how energy would be too cheap to even charge for."

It could have all come true...however, mankind pretty much abandoned nuclear power, due to irrational fears over radioactivity. While (some) nations still operate nuclear reactors, they're essentially all 1960s-era designs.


RE: CNTs in 30 years
By mattclary on 6/10/2008 11:31:34 AM , Rating: 2
RE: CNTs in 30 years
By Ringold on 6/10/2008 5:32:34 PM , Rating: 2
In a way, we have to call it even with the French. While we have irrational fear of nuclear, they have irrational fear of genetically modified crops.

So we starve ourselves of cheap energy, they just plain starve people.

Now, if we could just get everybody on board with nuclear and GM crops, a lot of problems in the world would evaporate!


RE: CNTs in 30 years
By pnyffeler on 6/11/2008 1:29:58 PM , Rating: 2
I like your analogy of carbon nanotubes (CNT's) to nuclear energy.

So what you're saying is that if I blast a spider with CNT's, and it happens to bite me, I will be able to climb walls and make out upside down with Kirsten Dunst?


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