DAYTON — Because they were once used widely as coolants and lubricants in electrical equipment, PCBs now contaminate an estimated 525 million tons of soil at more than 400 sites in the United States, including five in Montgomery County.
Exposure to PCBs, or polychlorinated biphenyls, can cause acne, rashes and liver damage.
But ridding soil and sludge of PCBs isn't easy. Clay can trap the material and make it harder to heat and break down. And cooking PCBs at extremely high temperatures can release even more toxic dioxins into the air.
Researchers at the University of Dayton believe they have come up with a simple recipe for solving both problems.
By mixing the contaminated soil with a slurry of iron nanoparticles — each so small a thimble can hold many trillions — the PCBs can be neutralized at much lower temperatures, saving money, energy and, better still, avoiding the release of dioxins.
The iron nanoparticles "go into the different nooks and crannies and find the PCBs wherever they are hiding," making them more susceptible to heat, said Sukh Sidhu, a professor of mechanical engineering at UD and a distinguished research scientist at the University of Dayton Research Institute. "It's a very simple idea really."
The brainstorm occurred about three years ago when Sidhu, whose research focus has been air contaminants from combustion, began discussing the problems of decontaminating PCBs with a friend who works for Environmental Chemical Corp. in Burlingame, Calif.
Sidhu assigned UD graduate student Patanjali Varanasi to test the idea. She discovered that the addition of just one unit of iron nanoparticles to every 1,000 units of contaminated soil lowered the heating requirement for neutralizing PCBs from about 800 degrees Celsius to just 300 degrees.
The results were published in September 2006 in the environmental journal Chemosphere.
Sidhu said the nanoparticles could potentially be used to eliminate any toxic solvent susceptible to heat.
ECC plans to try the process on a landfill in Germany contaminated with the pesticide lindane. The toxic soil, iron nanoparticles and a small amount of water will be mixed together in a large rotating heating chamber, much like a concrete mixer.
The goal now, Sidhu said, is to prove the approach is economical. A pound of iron nanoparticles, which is mixed with up to a half ton of contaminated soil, costs about $10. But the lower energy requirement may more than compensate for the cost of the nanoparticles, he said.
Varanasi and Sidhu estimate the technique will be ready for widespread use in two years.
Contact this reporter at (937) 225-2437 or jdebrosse@DaytonDailyNews.com.