LLNL Spinoff Porifera Uses Carbon Nanotube for Desalination

Wow. This is downright fun to report. Looks like the first generation (alpha)carbon nanotube membranes will come online within a year or two. Last time I posted a couple weeks back, I mentioned that the NanoTech Institute of the University of Texas at Dallas had learned to produce carbon nanotubes in industrial quantities. Then I opined  — wouldn’t it be nice if someone could adapt that carbon nanotube production method to the carbon nanotube desalination membranes that the LLNL team is working on

Well guess what?

Yep. Yeppers. Yup. Someone did. Now the press release below does not mention the industrial production method that they are using. But it does say that an LLNL spinoff called Porifera is going to be making carbon nanotube membranes for water purification. The first benefit that is touted is the anti fouling aspects of the membrane

The tubes are packed closely together and the water flows through them like it flows through straws. Chirality doesn’t matter, said company representatives I spoke to at the California Clean Tech Open, which held its award gala in San Francisco tonight. The opening of the tubes is so small (a few nanometers wide) that bacteria, biological material and other impurities get cleaned out of the water because they can’t fit where water molecules can. The filter will also likely be useful for desalinating seawater, although purifying waste water will likely be the first application.

Another added bonus: because the impurities get stuck outside of the tubes, membrane fouling is less of a problem. It is difficult to clean traditional membranes because material can be caught inside the membrane. If bacteria or salts accumulate on the outside [of the carbon nanotubes], they can just be swirled away with water.

Curiously the article only mentions the desalination abilities of the membrane as a secondary property. Its not clear why. Consider that  they make this astounding proposition:

Overall, Porifera’s array could cut the cost of desalination by 25 percent or more. In traditional purification and desalination systems, large amounts of energy are required to pressurize water and force it through a membrane. Here, gravity does a lot of the work.

Read that? Gravity does “a lot” of the work. Its not clear here how much “a lot” is. Current membrane technology requires pressures that are the equivalent of about 1700 feet of ocean water. Its too expensive to site desal at those depths. But what would happen to costs if you could site desal membranes in 100 feet of water a couple hundred feet offshore?   Here, look at this animate graphic of an undersea power & water producing unit using wave energy. Notice the desalting unit onshore. Just place the membrane on the ocean floor near the pumps. You let ocean pressures  press the water through the carbon nanotube membranes and let the wave action pumps force the fresh water ashore. (Hmm well some bright desal consultant would have to tease out the relative costs of onshore concentrate disposal/onshore membrane pumps vs offshore installation/offshore maintenance to figure out at what depth/pressure the nanotube membrane becomes more cost effective than onshore desal. Might help if  all the metal parts were coated these new nano scale coating products so as to kill maintenance costs. As well, it would probably be helpful to coat all the underwater machinery with thin layer of  cation-exchange groups. These cause electrostatic repulsion of organic molecules. That said, it might be best to just chuck the whole underwater electrical generation stuff, set the desal membranes offshore and pull the desalinated water onshore with onshore pumps powered by current generation solar cells that  make solar electrical production as cheap as coal.  In the next couple years those solar cell electrical generation costs will drop much further. Do enough solar electrical generation to use the grid as a battery. Another idea would be to have a California water official with seriously good social skills talk to The City of Carpinteria near Santa Barbara negotiating with Venoco over their proposed Paredon Project. The Paredon Project skirts the offshore drilling problem by siting the oil rigs onshore and then drilling down and sideways for a couple miles out into the Santa Barbara straights. California water guys might ask The City of Carpinteria to require of Venoco that they drill and maintain for four years (or the life of the oil wells–which ever is longer) a slant well for water desalination. This would be an experimental project. Whereas the oil wells go out several miles–the slant water well would go down and out only a couple hundred feet/yards. There would be a carbon nanotube membrane on the end of the pipe in the ocean. The state’s costs for the experiment would be to design nanotubes membrane fitting on the end of the well out in the ocean. From the membrane well head –fresh water would flow downhill toward the shore. Seperately, The Paredon Project will create a lot of waste salt water mixed with hydrocarbons and sulfer that needs to be treated. Clean up for this is already built into project costs. I would think If the carbon nanotube membranes can make that water fresh and clean for lower costs–then that might even make up for the costs of the experimental slant water well. )

Sorry about the tangent.

What else?

It would probably be a good idea for someone to mention the problem that evolving membrane technology creates for desal plant designers like Posiden. I mentioned this a couple blogs ago. They’ll need to be able to design new desal plant in such a way that they have has the ability to change over cheaply to future generations of membranes that don’t need pre treatment. For example, if you figure on the outside that these carbon nanotube membranes come out of alpha in 2 years and beta in 5 years…any desal plant coming onstream in the next five years is going to be outdated for much of its productive life.)

Oh and don’t forget to patronize  Porifera

Anyhow here is the article:

Michael Kanellos

Start-Up Cuts Water Purification Costs With Carbon Nanotubes November 6, 2008 at 10:32 PM

Single walled carbon nanotubes are the child prodigy of the material science world.

The tubes-which are spools of carbon atoms that resemble rolls of chicken wire–are stronger than steel and conduct electricity better than metals. They are also incredibly thin, only a few nanometers wide, which gives them an ability to transport other particles with very little energy.

Unfortunately, they also tend to be somewhat tempermental and difficult to control. Manufacturing them in large batches in a uniform manner has proved extremely difficult. The chirality, or how the carbon atoms are arranged in relation to one another in the wall, varies from tube to tube, which changes their properties in many applications. It’s one of the big reason that carbon nanotube semiconductors keep getting pushed further and further into the future. Other applications, such as tennis rackets, can get by with the less spectacular cousin, the multi-walled nanotubes.

Porifera, a spin out of Lawrence Livermore National Labs, has come up with a way to skirt the manufacturing problem and devise a product that leverages the unique thinness of single walled nanotubes. It has made a water filter of single walled carbon nanotubes. The tubes are packed closely together and the water flows through them like it flows through straws. Chirality doesn’t matter, said company representatives I spoke to at the California Clean Tech Open, which held its award gala in San Francisco tonight. The opening of the tubes is so small (a few nanometers wide) that bacteria, biological material and other impurities get cleaned out of the water because they can’t fit where water molecules can. The filter will also likely be useful for desalinating seawater, although purifying wastewater will likely be the first application.

Another added bonus: because the impurities get stuck outside of the tubes, membrane fouling is less of a problem. It is difficult to clean traditional membranes because material can be caught inside the membrane. If bacteria or salts accumulate on the outside, they can just be swirled away with water.

Overall, Porifera’s array could cut the cost of desalination by 25 percent or more. In traditional purification and desalination systems, large amounts of energy are required to pressurize water and force it through a membrane. Here, gravity does a lot of the work.

A nanotube membrane also has the advantage of simplicity. Some companies, such as Denmark’s Aquaporin, are working on molecular filters that rely on a synthetic version of a natural protein called an aquaporin. Although scientists have struggled with making reasonably uniform carbon nanotubes,they are farther along than trying to make synthetic aquaporin. (General Electric, which has been snapping up water companies in the past few years, is working on similar molecular straw membranes.)

Porifera by the way were the runner-up the air, water and waste award at the Clean Tech Open. The winner was Over the Moon Diapers, which is working on environmentally friendly diapers. The prize for Over the Moon came with a $100,000 value and attracts attention from VCs.

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Explore posts in the same categories: LLNL Research, membrane research, Water Desalination Research and Development

3 Comments on “LLNL Spinoff Porifera Uses Carbon Nanotube for Desalination”


  1. […] Desalination Research And Development Breaking News Incisive Analysis « LLNL Spinoff Porifera Uses Carbon Nanotube for Desalination […]


  2. […] Salazar will be interested in accelerated funding for all forms of desalination R&D from Proifera plus a dozen other cutting edge membrane companies to left handed ideas like low temperature […]


  3. […] my last post, I mentioned that membranes may be so efficient that maybe  five years from now you could drill a slant well out a couple […]


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