(Chelation/Electrodeposition of Toxic Metals from Soils)
IT Corporation has conducted laboratory-scale research on an innovative process that removes heavy metals from contaminated soils and sludges by forming a soluble chelate. The metals and the chelating agent are then separated from the soils and recovered.
The treatment employs two key steps (see figure below): (1) a water-soluble chelating agent, such as ethylenediamine tetra acetic acid, bonds with heavy metals and forms a chelate; and (2) an electromembrane reactor (EMR) recovers the heavy metals from the chelate and regenerates the chelating agent.
Soils are screened before the chelation step to remove large particles such as wood, metal scrap, and large rocks.
The chelate is dewatered to separate the water- soluble chelating agent from the solid phase. The separated chelating agent, which contains heavy metals, is then treated in the EMR. The EMR consists of an electrolytic cell with a cation transfer membrane separating the cathode and anode chambers.
The technology may be applicable to a wide variety of metal-contaminated hazardous wastes, including soils and sludges. Limited work has also been conducted to determine its effectiveness in removing cadmium from soils and sludges.
This technology was accepted into the SITE Emerging Technology Program in July 1994. The Jack's Creek site, located near Maitland, Pennsylvania, was selected for evaluation of the technology. The site was operated as a precious and nonprecious metal smelting and nonferrous metal recycling operation from 1958 to 1977. A portion of the property is currently operated as a scrap yard. The lead concentration in the contaminated soil used for the evaluation was approximately 2 percent. Toxicity characteristic leaching procedure (TCLP) analysis on the contaminated soil showed lead levels of 7.7 milligrams per liter (mg/L), which is above the regulatory limit of 5 mg/L. During the project, IT Corporation will establish appropriate conditions for removal of lead from the soil and reduce TCLP concentrations of lead in the soil to below regulatory levels.
EPA PROJECT MANAGER:
George Moore
U.S. EPA
National Risk Management Research
Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
513-569-7991
Fax: 513-569-7276
TECHNOLOGY DEVELOPER CONTACT:
Radha Krishnan
IT Corporation
11499 Chester Road
Cincinnati, OH 45246-4012
513-782-4700
Fax: 513-782-4807