|NASA Invention Offers Slippery Solution for Environmental Contamination||
When a groundwater treatment team at Kennedy Space Center in Florida recently won NASA's Invention of the Year award, the honor came as a pleasant shock. "We about fell out of our chairs," said Jackie Quinn, an environmental engineer with the group.
The team received the award for developing a simple and clever substance for cleaning up water contaminated by harsh, chlorinated solvents. "It was like a dream come true! I couldn't believe it," beamed analytical chemist Kathy Brooks.
Image to right: Microscopic bubbles of emulsified iron draw in contaminants and react with them to form harmless substances.
Credit: NASA/University of Central Florida
Chemists classify chlorinated solvents as "dense non-aqueous phase liquids" which, like oil and water, remain separated in layers of liquid and won't mix together. The solvents are called "DNAPLs" for short and are harmful to the environment. Such solvents were used extensively around Kennedy during the 1960s and 70s to clean rocket parts and in everyday industries like dry cleaning.
"For so long, chlorinated solvents were used because they were considered so safe to humans. They didn’t know about the toxicity or long-term clean up issues," explained Brooks.
A standard method for treating contaminated water is to place iron walls in the water and let the metal reaction transform the offending chemicals. The Kennedy team wanted to take a different approach, so the group turned to the big potential of nanotechnology for a solution. Their answer came in the form of itty-bitty particles of iron 100 nanometers in size.
Image to left: NASA Associate Administrator Rex Geveden (center) presented the Invention of the Year award to team members Debra Reinhart (left to right), Cherie Geiger, Jacqueline Quinn, Kathleen Brooks and Christian Clausen at a ceremony in Washington. Credit: NASA/Bill Ingalls
Quinn, Brooks and three other researchers with the University of Central Florida devised a mixture of iron, vegetable oil and a substance called a "surfactant" that aids in attracting contaminants. The result was a black syrup the team dubbed "emulsified zero-valent iron." The goo is designed to be injected into groundwater where it behaves like the DNAPL solvents. The iron floats as a blob of little oily bubbles, closing in on the solvent -- a creeping wolf in sheep's clothing. "When iron gets close to it, it sucks it inside," said Quinn.
Like bugs in a popular pest control product, the solvent checks in, but can't check out. "The reaction takes place inside the bubble," described Quinn. "Nothing leaves the bubble until it's completely degraded." Once the reaction is finished, the only things left of the solvent are harmless chloride salt and ethene, a benign gas. And what of the vegetable oil still swimming around in the groundwater? "The oil will eventually be eaten by naturally occurring bacteria," said Quinn.
Even more stunning than the simple genius of the team's remedy is how quickly it works.
"In a really contaminated site, even though the complete reaction may take a couple of weeks or a month, once you pump this stuff into the ground, the water clears up immediately. So you can take samplings of the water and -- like wow -- the water is clean," said Brooks. "It's amazing."
The team's emulsified iron cleans up contaminated water so well, it's no wonder the compound is NASA's clear winner for the Invention of the Year.
NASA's John F. Kennedy Space Center