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Welcome to the Energy & Environment (E&E) Exchange, a blog dedicated to science and engineering topics that are (generally) related to energy and the environment. This blog is meant to encourage discussion about the challenges and possibilities surrounding sustainability through science and technology. The blog's owner, cheme_wordsmithy, is a former technical writer and engineering editor at IEEE GlobalSpec, the company that powers CR4.

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Cleaning Oil with a Nanosponge

Posted May 16, 2012 9:00 AM by cheme_wordsmithy

If you've been keeping up with the latest developments in technology, then you've probably heard about at least one new development stemming from nanotechnology. The ability to control matter on the molecular scale has opened up a new door that is brimming with possibilities. Nanotech allows for the creation of new materials with unique and enhanced properties, and has specific implications for the electronics and biomedical industries.

One of the latest nanotech discoveries came through researchers at Rice University and Penn State. They found that adding boron to carbon during nanotube construction creates spongy blocks that have amazing oil absorbing properties.

(Image Credit: Rice University - Jeff Fitlow)

How It Works

The typical chemical vapor deposition process which grows multiwalled carbon nanotubes on a substrate usually produces straight tubes with no interconnections. But adding boron introduces defects into the nanotubes by encouraging carbon to form covalent bonds at the atomic level, resulting in a tangled and complex network of tubes. In short, adding boron puts kinks and elbows into the otherwise straight carbon tubes.

From this:

To This:

(Image Credit: Elsevier)

To add boron, scientists use very high temperatures in a furnace, essentially 'knitting' the substance to the nanotube fabric in a one step process. The result is a material with a very low density and large available volume for capturing and holding oils.

Nanosponges have been created before, but the processes used to induce the unique structure were always post-growth, meaning they were done after the nanotubes were already formed. The use of boron allows the tubes to form proper covalent connections during their creation.

What It Does

The nanosponge is extremely hydrophobic, giving it the natural tendency to float on water and not absorb it even when submerged. It is also ferromagnetic, meaning it can be controlled or retrieved using a magnet. The density of the material is extremely low, making the available volume for oil uptake very high. Not only can it soak up over 100 times its weight in oil as it floats on the water, but it can store the oil for later retrieval. The oil can then be squeezed out or burned off, allowing the sponge to be reused. The researchers also tested the sponge's robustness and reusability in the lab - it maintained elasticity even after 10,000 compressions. Safe to say, this material has tremendous power as an agent for surface oil cleanup.

This video from Rice University gives a visual demonstration of the material's properties.

What It Means

The process used to create the sponge is the perhaps real success story here. The main drawback with past nanosponges was their inability to be produced on a large scale. With this one-step formation process, production of the material can be scaled up to bigger production quantities much more easily. The next step for researchers is in finding ways to create the large sheets needed for oil spill applications.

Of course, what it all comes down to is cost effectiveness. Can these nanosponges eventually be made cheap enough to complete or displace other oil cleaning technologies and methods? And will their oil-cleaning properties be useful enough in real-life oil spill problems, where a lot of the oil collects underneath the surface of the water.

What's interesting is that, like many new technologies, this product may have other potential applications besides environmental cleanup. Researchers say it could be used for making lighter and more efficient batteries, scaffolds for bone-tissue regeneration, composites for the automotive and aerospace industries, or membranes for filtration. It is a testament to the versatility of materials developed at the nanoscale.


RICE University - Nanosponges soak up oil again and again


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