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New method to remove mercury from contaminated soil will make a cleaner, safer environment
OAK RIDGE, Tenn.,
Sep. 1, 1995
A new cleansing process developed by the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL) to remove mercury from soil may soon be making it easier to clean the environment and make it safer.
This process will save time and money while removing mercury more efficiently than any other process, say ORNL scientists. It will also eliminate the costly prospect of permanently storing thousands of drums containing mercury-contaminated soil in controlled hazardous waste sites.
"We are moving away from a system that stores mercury-contaminated soil to one that cleans it up," said Clay Easterly, the primary researcher and inventor of the remediation process. Easterly worked with Arpad Vass and Richard Tyndall, now retired, to develop the process as a new way to deal with environmental cleanup problems.
"You could store that mercury and it will never change," said Easterly, a member of ORNL's Health Sciences Research Division. "Anytime in the future it will still pose the same risk as the day it was collected. Now we have a way to deal with it." This new method allows the soil to be returned to the land and used again.
Most of the mercury in Oak Ridge has been in the soil since the late 1950s to early 1960s. Mercury was a key element used to create enriched lithium by separating the lithium isotopes.
Mercury is a heavy, silver-white element that is liquid at room temperature. Depending on its chemical form and quantity, mercury may be harmful. Mercury is a natural part of the atmosphere. During the earliest years of the earth's formation, the volcanic activity and high temperatures emitted mercury vapor into the air. Small, tolerable amounts of mercury are still found in our air, food and water. However, when mercury levels rise, the health risks increase.
The removal of mercury begins by mixing water, copper-based pellets, an amoebic isolate and mercury-laden soil in a cylinder. An amoebic isolate is a "dispersing agent that separates soil particles and disperses mercury, allowing copper to have better contact with mercury," Easterly said. As the cylinder turns, the amoebic isolate loosens the clumps of soil, similar to the way detergent in a washing machine loosens the dirt from clothes. While the clumps of soil break into particles smaller than sand, the copper pellets, containing a small amount of magnetic metal, attract the mercury from the particles. Next, a magnet removes the mercury-covered copper pellets and places them in a vacuum oven, where heat separates the mercury from the copper.
The amoebic isolate of the new process will particularly be helpful in extracting mercury from contaminated areas on the Oak Ridge Reservation that have "very tight soils," Easterly said. Tight soils make it more difficult to break the soil into smaller pieces for better contact between the copper and mercury. The dispersing effect of the isolate, he said, is the key to breaking up the soil and making the removal process more efficient. Also, the amoebic isolate is safe to use because it comes from bacterial origins that make it biodegradable and nontoxic.
No dangerous chemicals are used in the removal process, Easterly said. The cleaned soil can be used anywhere and the copper pellets can be used again. The reclaimed mercury can be sold to industries that need the element for their manufacturing. Other advantages are the mobility of the equipment, short setup time and minimal environmental hazard during the operation.
The sale of the mercury could offset the cost of processing, particularly when charges associated with the alternative of storage/ disposal of the contaminated soils as hazardous waste is considered, Easterly said. The low-technology chemistry and equipment costs less than the more expensive and cumbersome storage process or any other chemistry or energy intensive methods.
The extracted mercury would be valuable in the electrical field because it becomes superconducting when cooled, conducting electricity with virtually no resistance, and by the chemical industry in chlorine production.
The new mercury-removal process helps to fulfill an ORNL mission of finding more efficient, less expensive ways to clean the environment.
You can learn more about this research and many other exciting projects by visiting ORNL on Oct. 21, 1995, during its Community Day event. Many of our facilities will be open to the public that day. For additional information, call ORNL Public Affairs, 865-574-4160.
ORNL, one of DOE's multiprogram national research and development facilities, is managed by Lockheed Martin Energy Systems, which also manages the Oak Ridge K-25 Site and the Oak Ridge Y-12 Plant.