After the Deepwater Horizon accident, when oil began blobbing up to the surface, it was hard not to look at the mess and wish there was some giant sponge that could just soak it all up.
That sponge is here and ready for action, though it is not giant. In fact, it's what's happening at the nanoscale that makes the material near miraculous. Built of boron-spiked carbon nanotubes, the new sponge has several remarkable properties that may make the next oil spill hardly a spill at all.
Daniel Paul Hashim, a graduate student in materials science engineering and nanotechnology for environment and energy at Rice University, Houston, TX, had been searching for a better cathode when he first doped carbon nanotubes with boron. He'd read a theoretical paper that suggested that the "boron impurity sites" would have an affinity to lithium ions.
The carbon nanotube sponge can reject water and soak up oil.Until then, carbon nanotubes had only been used in a loose powder form or aligned on a silicon substrate. The boron joined the nanotubes, turning them into a three-dimensional sponge. "Upon playing with this material, I immediately noticed that it was superhydrophobic," says Hashim. Dunk it in water and it comes out dry to the touch.
Dunk it in oil and that's another story—the highly porous sponge soaks up the oil instantaneously.
Once saturated, such sponges (conveniently ferromagnetic) could be scattered over a slick and then harvested with a magnet-bedecked ship. And the recovered oil is not lost to whatever company first harvested it. It can be squeezed out of the sponge and retain its resale value. Or, if need be, it can be burned right in the sponge; the material is temperature invariant as well.
Daniel Paul Hashim created the nanotube sponge.With its density at 5 mg per cubic centimeter, Hashim's sponge is now the second least dense material on the planet (Aerogel, the least dense material, is 1 mg per cubic centimeter)—hard to believe when eyeing the black rubbery polymer. Its lightness makes it ideal for spill prevention as well as clean-up. A tanker could be filled with the sponge before being loaded with oil. If it should happen to overturn, or even crack wide open, the oil would just sit there in the sponge. "It's 99 percent air," says Hashim. "That's the beauty of it—it's 99 percent free space. It's a good sacrifice, that one percent, to prevent spills."
The remarkable material has other applications. Electrically conductive, it may also be able to help desalinate and purify water. But first Hashim has to be sure the material itself is not toxic. Though the sponge has yet to be tested, he's confident it will prove benign. "When you think about a polymer, the individual units are toxic. Once linked, the material becomes safe, he says. "I think you can find a similar trend with nanotubes. If you can crosslink them to create a monolithic structure, they're safe."
The carbon nanotube sponge holds the potential to aid in oil spill cleanup.Oil companies and water purification companies have already come knocking on Hashim's door. Though the material is ready for production, he is not yet ready for production. "It's ready to go for testing in the field," says Hashim. "As far as cost goes, the current lab-scale design I have in place is certainly not ideal for a cost-effective sponge."
Once the sponge is produced at a larger scale, however, the disaster known as an oil spill may be only marginally more worrisome than the proverbial glass of spilt milk.
Michael Abrams is an independent writer.