Damascus steel is certainly some impressive stuff, but my understanding is that it is created through a great deal of work, bonding and folding and rebonding to get steel with alternating layers of hard and tough steel. Definitely not a naturally occurring material. Free lead, nickle, cadmium, and copper all occur in their free state and can be found naturally. Likewise asbestos, although it is usually in with mica, I think.
Of course heating to ignition with microwaves would be an effective means of disposal for CNT waste, but first it would need to be located. That is probably going to be the challenge if quantities of CNT material are spilled.
I believe that CNN's do occur naturally, as in Damascus Steel of the Medieval to mid 1800's, when the iron ore mines(thought to have been in Kerala in India) were cleaned out.
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.
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.
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.
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.
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.
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.
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