Carbon Nanotube Sponge Can Absorb Toxic Oils and Solvents up to 180x Its Weight!
Photo: Peking University and Tsinghua University
Is There Anything We CAN'T Do With Carbon Nanotubes?
Cleaning up toxic spills has always been a problem. It's hard, and it's expensive, and you have to be thorough. But things might have just got easier: Scientists from the Peking University and Tsinghua University have created a sponge like no other. It is made of carbon nanotubes - regular carbon atoms arranged in a specific cylindrical shape - and can absorb organic pollutants from the surface of water (such as oil and solvents) up to 180x its weight (!) without absorbing water (see video below to see how light it is). And once its full of toxic liquids, the best part is that you can just wring it and start again.
These new sponges seem to be clearly better than what we're using at the moment:
Current commercial absorbents for oil spill recovery and industrial use tend to be based on cellulose or polypropylene. These materials can absorb only up to 20 times their own weight and are impractical for large spills, where dispersants are used. Dispersants allow the oil to become diluted, but it remains in the water. Other materials based on porous oxide-based materials or other polymers can absorb up to twice as much pollutant per weight, but generally need to be heated to remove the organic material. High-temperature heating is not practical on small scales or on ships, and a clear advantage of a squeezable sponge is that the oil can be readily recovered and reused. For other applications including solvent cleanup, the sponges can be heated to remove the pollutant, without affecting the properties of the sponges.
180 times its weight seems to be the maximum that such a sponge can absorb (it depends on what you're mopping up). The figure for diesel fuel is 143x, and for ethylene glycol its 175x.
What Are They Made Of?
The sponges are made from interconnected carbon nanotubes that are about 30-50 nanometres across and tens to hundreds of micrometers long, and they are over 99% porous (which leaves a lot of space to absorb oil and solvents). And since carbon nanotubes are hydrophobic, there's no modification required to make them not absorb water.
But That's Not All
If these sponges were only good for cleaning up toxic spills, that would be something. But according to professor Anyuan Cao of Peking University, they could also be used "as filters, membranes, or absorbents to remove bacteria or contaminants from liquid or gas. They could also be used as noise-absorption layers in houses, and soldiers might benefit by using these sponges in impact energy absorbing components while adding little weight. Thermally insulated clothing is also possible." Talk about versatile!
Via Materials View, Green Car Congress
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