Chloroform cleanup: just the beginning for palladium-gold catalysts

Federally funded research pays off with new process for environmental remediation

Researchers from Rice University, DuPont Central Research and Development and Stanford University have announced a full-scale field test of an innovative process that gently but quickly destroys some of the world’s most pervasive and problematic pollutants. The technology, called PGClear, originated from basic scientific research at Rice during a 10-year, federally funded initiative to use nanotechnology to clean the environment.

PGClear uses a combination of palladium and gold metal to break down hazardous compounds like vinyl chloride, trichloroethene (TCE) and chloroform into nontoxic byproducts.

“Chlorinated compounds were widely used as solvents for many decades, and they are common groundwater contaminants the world over,” said Rice’s Michael Wong, professor of chemical and biomolecular engineering and the lead researcher on the PGClear project. “These compounds are also extremely difficult to treat inexpensively with conventional technology. My lab began its work to solve this problem more than a decade ago.”

DuPont researcher John Wilkens said, “The problem-solving for this technology began at the nanoscale. Mike and his team were working with nanoscale catalysts when they developed the technology that would ultimately become PGClear. The scale of the technology was subsequently enlarged to permit use in conventional reaction systems for field implementation.”

The first large-scale PGClear unit, which is designed to treat groundwater contaminated with chloroform, is scheduled for installation at a DuPont site in Louisville, Ky., in June. The 6-by-8-foot unit contains valves and pipes that will carry groundwater to a series of tubes that each contain thousands of pellets of palladium-gold (PG) catalyst. The pellets, which are about the size of a grain of rice, spur a chemical reaction that breaks down chloroform into nontoxic methane and chloride salt.

“The palladium-gold catalyst has so far performed well for remediating groundwater samples collected at DuPont,” said Brad Nave, director of the DuPont Remediation Project. “While the project is not yet full-scale, our next step will subject the technology to the rigors of real-world field conditions. Rice, Stanford and DuPont have been working on the details of the field pilot for several years, and we’re looking forward to a successful test.”

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