Scientists Develop Catalyst That Removes Perchlorate From Groundwater

Scientists at the University of Illinois at Urbana-Champaign announced on Sept. 11 they have developed a new chemical catalyst that uses hydrogen gas to efficiently remove and destroy harmful perchlorate in contaminated groundwater.

Perchlorate, primarily used in rocket fuel, explosives, fireworks, road flares and airbag inflation systems, is an inorganic chemical that is known to interfere with iodine uptake of the thyroid gland. A reduction in iodine uptake can result in decreased production of thyroid hormones, which are needed for prenatal and postnatal growth and development, as well as for normal metabolism and mental function in the adult.

Because perchlorate is readily soluble in water, it can be transported vast distances in groundwater or rivers. A plume of contaminated groundwater from a manufacturing plant near Las Vegas, for example, reached the Colorado River and spread throughout the Southwest. Cleanup could take decades.

"Perchlorate has been recognized as a significant environmental contaminant in U.S. water supplies, and its physical and chemical properties pose a serious challenge for remediation," said John Shapley, a professor of chemistry at Illinois and co-developer, with graduate student Keith Hurley, of the new catalyst.

Efforts at remediation using naturally occurring microorganisms or existing pump-and-treat technology are too complicated, too energy intensive or too slow to be practical, Shapley said.

The new catalyst is composed of two metals -- palladium and rhenium -- supported on activated carbon. The catalyst operates at room temperature under normal atmospheric pressure, and does not dissolve in water.

"In catalytic operation, the rhenium removes an oxygen atom from the perchlorate molecule in what is called an atom transfer reaction," Hurley said. "Meanwhile, the palladium activates the gaseous hydrogen atoms so they will react with the freed oxygen. What's left is harmless chloride and water." The catalytic reaction continues as long as there is both hydrogen gas and perchlorate contaminant present.

"While current technologies -- such as ion exchange systems -- can concentrate and remove perchlorate from water, they cannot destroy it," Shapley said. "Our catalyst would take a concentrated stream of perchlorate and get rid of it altogether."

John Shapley: http://www.scs.uiuc.edu/chem/jshply.htm

This article originally appeared in the 09/01/2006 issue of Environmental Protection.

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