For boaters and fishermen in the southeast United States, Salvinia molesta has become a big headache. It covers lakes and ponds with a thick mat of floating leaves that chokes out sunlight, robs the water of oxygen and kills aquatic life below. Originally from Brazil, the fern-like plant has been spreading west from Florida toward Texas, Arizona and California.
Now, German researchers have found that this pesky aquatic weed may be useful in soaking up petroleum without taking in the water around it. That could be a huge help to environmental workers looking for non-toxic ways of cleaning up oil spills without creating a big disposal headache.
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"We are looking at nature, trying to understand what nature does and how it works, and using that for technical applications," said Claudia Zeiger , a researcher at the Karlsruhle Institute of Technology and lead author on the new report published today in the journal Bioinspiration & Biomimetics.
"Salvinia has a hairy microstructure," she said. "What we did was the first step ... trying to understand the principal of how it works."
Photo:
Salvinia molesta
can soak up oil while leaving surrounding water behind. Credit: Thinkstock
Zeiger, together with researchers from the Nees Institute for Biodiversity of Plants at the University of Bonn, have been discovering what makes these plants so special. They looked at four species of Salvinia for the shape of hairy outgrowths called trichomes. Each trichome had a different rate of oil absorption.
This video shows how fast Salvinia molesta soaks up oil, while repelling water.
Three years ago, IMT developed a synthetic version of these hairy surfaces called "nanofur," which is produced by pressing a hot rough plate into a polymer foil. "The surface of the polymer melts, and when the steel plate is retracted, micro- and nanoscaled hairs are pulled from the surface," explained Zeiger. "It's like cheese on a pizza. The surface melts and pulls up and then freezes as we get a surface that is hairy and has similar structures."
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Zeiger believes that both the Salvinia plant and the synthetic nanofur can be used to clean up oil spills, depending on the application. In some areas, like a cooling tank for a power plant, for example, the nanofur degrades more quickly.
Zeiger says she and her colleagues are working to scale up the nanofur so it can be used outside the laboratory.
"It's quite a challenge," she said.
Martin Hubbe, professor of forest biomaterials at North Carolina State University, likes the idea of using invasive aquatic weeds to soak up oil spills. "The thing to bear in mind is that superabsorbent character can easily be damaged or contaminated," Hubbe said about using other types of synthetic absorbing materials. "That's why the present work is so promising: One can potentially use natural products, which inherently have a low environmental impact. Follow-up treatments, including composting or incineration, then could be studied."
Hubbe said there are plenty of obstacles, including harvesting and maintaining the plants. "Crude oil rather quickly undergoes changes in chemistry and physical state, so it may not behave like a liquid," Hubbe said in an e-mail. "So, even if one had the "perfect sorbent", major oil spills often mainly need other kinds of intervention, such as preventing them in the first place, the use of skimmers, etc."
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