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Researchers at the Bhabha Atomic Research Centre (BARC) in Mumbai, India, are studying the potential use of carbon nanotubes—hollow carbon fibers—to filter viruses, bacteria, toxic metal ions, and large noxious organic molecules out of water. According to Physorg.com, "the smooth and water repellant interior of carbon nanotubes means that a filter based on this technology would be very efficient, allowing a high flow rate of water through the filter without fouling. Importantly, the power needed to drive water through such a system will be low compared to conventional membrane technology."

As CleanTechnica.com points out, solutions to the problem of contaminated water are desperately needed. But carbon nanotubes are not likely to be that solution, at least not any time soon.

Among the reasons:

• Nanotubes would be extremely difficult to arrange into a filter. The caveat that Physorg.com mentions touches on a very important point that could pose the greatest stumbling block to carbon nanotube-based water filters: "To be useful as a nanotech filtration system for contaminated water, these nanoscale structures need to be engineered to form well-defined arrangements to allow the efficient decontamination of water." As I learned this week at a nanotech workshop at the University of Wisconsin-Madison, nanotubes don't exist in individual forms. Instead, they cluster in clumps and are very difficult to separate. In fact, it was only two years ago that researchers at Trinity College Dublin discovered that carbon nanotubes could be unbundled without damaging or weaking them, according to Philip Streich, the 17-year old co-founder of Graphene Solutions, LLC in Platteville, Wis. Trying to filter water through a clump of nanotubes pointing in different directions (with some tubes possibly being blocked by other tubes) is not likely to be efficient.

• The nanotubes would have to be extremely tiny (even by nano standards) to filter out contaminants. Although bacteria are about 1,100 nanometers in diameter, viruses can be between 70 and three nanometers in diameter. You would need a carbon nanotube with roughly the dimensions of a strand of DNA in order to block out the smallest contaminants.

• The carbon nanotubes  may pose health risks There is no conclusive evidence that ingesting carbon nanotubes is dangerous, but there also are no studies proving that it's safe. Until scientists have a better handle on this, it's probably wise to avoid drinking or inhaling them. The former would be hard to do if any of the nanotubes were to shake loose from the filter and end up in the water supply.

8 Comments

1. 1. AndrewJayPollack 10:23 PM 9/17/08

   There is nothing that carbon nanotubes will not do. They will cure all diseases, clean all water, turn deserts into farmland, and protect the cities from rising water.

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2. 2. JayHawk 08:39 AM 9/18/08

   Wow, this is a pretty cool discovery. Question: Would this filter be used in homes and business as a personal device or would it be used for municipalities and city drinking water supplies? 'Cause I know that most U.S. cities have simply been using chlorine to make their water safe for about 100 years.

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3. 3. jdwilson 10:02 AM 9/18/08

   Water purification products using CNTs are available now. http://www.seldontech.com
   
   
   
   Seldon has developed a new nanostructured material which includes carbon nanotubes: nanomesh

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4. 4. senojjones 07:12 PM 9/18/08

   One might think about making the nanotubes "bottom heavy". Complete the last phase of the reaction with deuterium. Then centrifuge the nanotubes. They might orient vertically..
   
   Vertical orientation may allow them to be bundled with the heavy ends orientated together.

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5. 5. senojjones 07:58 PM 9/18/08

   One also might be able to "cap" the nanotubes chemically, using the differential reactivity of deuterium and hydrogen. Chlorinating deuterated tubes that had a hydrogen tip would give you a tube with a reactive group predominately on one end. Chlorine could be substituted for a charged group, ie sulfonate. Then the ends of the tubes would be grossly different.
   They could be oriented in an electric field or by selective absorption on to a surface.
   
   anyone ever tried to selectively modify a carbon nanotube stereospecifically?
   
   

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6. 6. Intelligent materials 06:53 AM 10/24/08

   NANOSHEL makes more than 50 types of products, among which the main products are nanotubes, SWCNT�s, MWCNT�s, nanoparticles,. These products are widely used in the fields such as textile industry, ceramics, chemical fiber, plastics, coatings, cosmetics, rubber, electrical and electronic equipments, electric power generation and boiler and so on
   
   Wow this is a great discovery.
   For more information please visit www.nanoshel.com

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7. 7. Intelligent materials 01:25 AM 11/11/08

   NANOSHEL makes more than 50 types of products, among which the main products are nanotubes, SWCNT´s, MWCNT´s, nanoparticles,. These products are widely used in the fields such as textile industry, ceramics, chemical fiber, plastics, coatings, cosmetics, rubber, electrical and electronic equipments, electric power generation and boiler and so on. Through providing the customers with nanomaterials and the application process solution, the company commits itself to assist clients to improve the functionality and technology content of the products so that the clients can promote their product added-values and market competitive competencies, keep their creative advantages for a long time in the concerned fields and make good economic benefits. www.nanoshel.com

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8. 8. shubhamindia 05:23 AM 12/13/10

   Activated Carbon Filter
   
   Highly absorbent carbon obtained by heating granulated charcoal to exhaust contained gases, resulting in a highly porous form with a very large surface area. It is used primarily for purifying gases by adsorption, solvent recovery, or deodorization and as an antidote to certain poisons. Also called activated carbon
   
   
   
   <a href="http://carbonfilter.co.in/activated_carbon_filter.htm">Activated Carbon Filter</a>
   
   <a href="http://carbonfilter.co.in/activated_carbon_filter.htm">Activated Carbon Filter</a>(ACF) is a natural material derived from bituminous coal, lignite, wood, coconut shell etc., activated by steam and other means, and each one have different adsorption properties (e.g. bituminous carbon for high chlorine reduction capacity). We also use various blends of carbon to achieve specific water quality and contaminants reduction (e.g. coconut shell carbon for "sweet taste").
   

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