UPTON, NY -- Some of the most polluted soil and waste ash in the world may have met its match with a new process based on natural ingredients and developed at the U.S. Department of Energy's Brookhaven National Laboratory.

The patented process, which uses simple citric acid, naturally occurring soil bacteria and sunlight, is described in the current edition of Environmental Science & Technology by two scientists from BNL's Department of Applied Science. It extracts metal contaminants from soil and wastes and then converts them to a concentrated and stable form.

The researchers report that their process removed nearly all the toxic metals and uranium from soil taken from polluted sites in Ohio and Tennessee. It also successfully cleaned incinerator ash from a municipal solid waste plant. In addition, it may be useful for other wastes and sludges.

"The resulting cleaned soil is much less hazardous and costly to dispose of, and can even be re-used," said A. J. Francis, one of the co-authors and co-inventors of the process. "Since the process separates the metals from the radioactive elements, the problem of mixed toxic-radioactive waste disposal is solved, the amount of waste is diminished greatly, and it's possible to reclaim the metals for a beneficial use."

Among the metals that can be separated from soil and ash using the process are cadmium, lead, zinc and copper. It can also remove radioactive elements, or radionuclides, such as uranium, thorium, plutonium, cobalt, cesium and strontium.

The process starts with a "washing" of the soil with liquid citric acid, the same acid found in oranges and lemons. The acid binds to the metals and radionuclides, carrying them with it when it washes through the soil. This forms compounds called metal citrates and, in the case of uranium uranyl citrate.

The citric acid is much less destructive on the soil than other methods, and does not linger in th
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Contact: Kara Villamil
karav@bnl.gov
516-344-5658
DOE/Brookhaven National Laboratory
30-Dec-1998