Treating toxins with nanoparticles
More nanotech from Earth & Sky: All things nano
DB: Researchers are looking to nanotechnology for better ways of cleaning the hundreds of thousands of toxic waste sites across the U.S.
JB: These sites contain chemicals like TCE – a common groundwater pollutant that’s been linked to cancer. Nanoparticles of a metal called palladium have been known to remove TCE from the environment. Rice University’s Michael Wong discovered a more efficient and less expensive way to break down TCE to clean groundwater, by using gold in a process called catalysis.
Wong: Not very intuitive there. Gold is expensive, and of course, palladium is expensive too. But as it turns out in the field of catalysis, gold is known to make other metals to be more active for catalysis.
DB: Wong expected that gold would make this reaction go faster. He didn’t expect how much faster. With gold, the breakdown was 100 times as fast.
JB: So far, Professor Wong has tested the nanoparticles only in the lab. Within the next two years, he hopes to begin pumping polluted groundwater through large filters coated with gold–palladium particles. This process could help reduce the billions of dollars it currently costs to clean toxic waste.
DB: For today, that’s our show. With thanks to the National Science Foundation, we’re Block and Byrd for Earth & Sky.
Dr. Wong told Earth & Sky, “The danger is, if we don’t treat it, the TCE will remain underground and slowly break down, but too slowly.
“TCE underground will continue to spread out. For most of sites, it’s now well within boundaries for the sites. But groundwater moves. It continues to flow. The front of the TCE–contaminated water continues to move down path of groundwater flow to the aquifer. Where do we get our water? From aquifers. So, if you don’t take care of those contaminated sites, then that TCE will eventually break through and enter into the drinking water system,” he said.
Speaking of catalysis as a way to remove the harmful TCEs from the water, Wong added, “Is there a way to chemically break down the undesired compounds such that those compounds no longer exist in the environment in water phase, solid phase, or gas phase? Our purpose was to use the idea of catalysis. It’s a chemical phenomenon where the molecules that you want to react momentarily sits on the surface of your particle, in our case nanoparticles, and that momentary absorption on that surface causes it to convert into another compound. The molecule we are interested in looking at is trichloroethylene, abbreviated as TCE, and this molecule essentially binds to the surface of our nanoparticles and it converts to ethane. Ethane is much safer, and the chloride atoms that were part of TCE pop off as chloride salt.”
Our thanks to:
Michael Wong
Rice University
Houston, Texas
More nanotech from Earth & Sky: All things nano
