Scientists develop sponges to clean up oil spills

In a development arising from nanotechnology research, scientists in Madison, Wis., have created a spongelike material that could provide a novel and sustainable way to clean up oil spills.

It's known as an aerogel, but it could just as well be called a "smart sponge."

To demonstrate how it works, researchers add a small amount of red dye to diesel, making the fuel stand out in a glass of water. The aerogel is dipped into the glass and within minutes, the sponge has soaked up the diesel. The aerogel is now red, and the glass of water is clear.

"It was very effective," said Shaoqin "Sarah" Gong, who runs a biotechnology-nanotechnology lab at the Wisconsin Institute for Discovery in Madison.

"So if you had an oil spill, for example, the idea is you could throw this aerogel sheet in the water and it would start to absorb the oil very quickly and efficiently," said Gong, an associate professor of biomedical engineering at the University of Wisconsin-Madison. "Once it's fully saturated, you can take it out and squeeze out all the oil."

The material's absorbing capacity is reduced somewhat after each use, but the product "can be reused for a couple of cycles," Gong said.

Researchers in Madison have patented their aerogel technology and are now seeking paper or petroleum industry partners to collaborate or fund research to test it on a larger scale.

Details of the aerogel discovery were published in January in the Journal of Materials Chemistry. Researchers say the product has the potential to help reduce water pollution that leads to water shortages around the world.

The aerogel absorption technology is the result of a collaboration between the Wisconsin Institute for Discovery and a nanotechnology pilot plant established two years ago at the U.S. Department of Agriculture's Forest Products Lab in Madison.

At the nanotech lab, researchers are working to develop new uses for wood that could provide a boon to Wisconsin's paper industry by finding new markets for forest products. It can also help manage forests and prevent wildfires, supporters of the technology say.

On a nano scale, the aerogel harnesses the absorbent qualities of wood pulp that have made it a key ingredient in diapers. And wood-derived cellulose nanofibril material in the aerogel is valued because of its strength.

A strand of it is as strong as a synthetic fiber such as Kevlar. Cellulose nanofibrils are about 1,000 times smaller than paper fibers.

A key challenge that the new research overcomes is that the tiny cellulose particles absorb water.

In Gong's lab, graduate student Qifeng Zheng combined the nanocellulose with polyvinyl alcohol — an ingredient commonly found in contact lens solutions. He then treated the mixture with a water-repelling coating. The process is considered environmentally friendly.

In carrying out the experiment, "He found this interesting phenomenon: It [the aerogel] did not take any water but was just taking oil. The first time he came to me, I said, 'This is crazy,' " Cai said.

That prompted Cai to think back to 2010 and the BP oil spill in the Gulf of Mexico. Researchers at the Forest Products Lab were approached after the spill to see if any of their research could help with the cleanup.

Cai told his boss that the lab could produce a fiberboard that would absorb oil, but it would also absorb water. Zheng's experiment allowed the aerogel sponge to repel water but absorb petroleum or metals.

"The recent development of cellulose nanocrystals and nanofibrils opens a brave new world for wood products," according to an endowment report last year. "When CNCs and CNFs are added to other materials, products can be made stronger, lighter, more cheaply, and from renewable resources."