Ann, this is indeed a concern. Like many of the clever solutions to engineering problems, we have to think of the effect on living organisms, not just humans. Semiconductor manufacturing also uses many toxic chemicals, for example, and these have to be controlled. This is true at the point of manufacture and at the point of disposal. I recall that even the ink used in thermal printers, such as those that are used to print receipts at stores, can be toxic. We need to be careful in handling exotic, engineered materials.
One question I do have is about the detection method. Since microwaves are used, I assume that the tests done on earhtworms are destructive. Soil, even after being exposed to microwaves, is still just soil. An earthworm on the other hand...
Good article explaining the detection method for CNT's in soil. Are there toxicity concerns for CNT's in product? Also, are there concerns with the processing method used to add the CNT's to the base material?
Its carbon, the thing that loves to react with oxygen... Light it up :) Let's find out how fast this material will decay or adhere to larger particles. How much of it is released in the industry, as well as from end use products and compare it with the amount of material required for it to be a threat prior to hitting the panic button.
It's good to have that voice of reason to set some perspective. Still, it's better to find it now and accomodate its problems than much, much later when it's everywhere. Asbestos comes to mind in that regard.
Asbestos is absolutely safe (inorganic and non-reactive). It's the genetic material that rides along with it when asbestos (because it's ends are needle sharp) puncture a cell's wall that kills. Which is why asbestos was used everywhere without any concern for human health (in schools, ships, tile floors). Human history is full of examples of "safe" technology that that was over-exploited before realizing the dangers.
Carbon nanotubes probably have similar mechanical effects. I was told by an ME friend that carbon fiber (yes, not nanotubes, but still relevant) is much more dangerous than fiberglass. Where you get fiberglass on or in your skin, it works its way out. Carbon fiber works their way in ...
I read in Science News a few years ago, nanotubes in the environment do NOT disperse like other polutants (perhaps this is a good thing?)
In any case, if they are so reactive to microwave's, perhaps this is the solution. Just blast the contaminated soil with a high enough dose to destroy the bonds and turn them back into simple carbon.
Interesting comments. This is the first I've heard about toxicity concerns in CNT's. Guess it's time to dump my stock in graphene futures! When I hear about toxicity concerns, the scientist voice inside my head always asks, "But what is the mechanism at work?". As you point out, it may be an issue of mechanics rather than chemistry. Once this is understood, then a potential solution is usually at hand. In the meantime I'll start using a HEPA filter when I sharpen my #2 pencil.
It seems that the alleged toxicity of these nanotubes must be a mechanical thing, although none of the reports bothers to say anything about the mechanism of toxicity. The good news is that these nanotubes don't occur naturally, at least I have not heard of them being natural. So the proliferation should be quite a bit less. Also, they are kind of expensive, I think, so perhaps users may be motivated to avoid spilling them.
It would be good if those who go around bleating out noninformational phrases could somehow be motivated to provide more actual information and less intention toward causing hysteria.
Of course, if the nanotubes are locked into a composite material they may be a lot less free to cause any type of problems, although it would seem that machining the composite could be a bit hazardous.
If microaves can heat up the CNT then they can destroy them. Collect the waste and bath it with microwaves, waste disposal problem solved. Light them up! A plasma furnace would also work and other metals can be recovered. iRobot can probably build a Roomba robot that will do manufacturing cleanup and CNT destruction at the same time.
Transfers the control of a large number of motion axes from one numerical control kernel to another within a CNC system, using multiple NCKs, and enables implement control schemes for virtually any type of machine tool.
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