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REMEDIATION OF RADIUM FROM CONTAMINATED SOIL
Citation:
Misra, M., R. K. Mehta, AND P. Lan. REMEDIATION OF RADIUM FROM CONTAMINATED SOIL. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/R-01/099, 2001.
Impact/Purpose:
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Description:
The objective of this study was to demonstrate the application of a physico-chemical separation process for the removal of radium from a sample of contaminated soil at the Ottawa, Illinois, site near Chicago. The size/activity distribution analyzed among the particles coarser than 5 micron showed that the activity was uniformly distributed. Almost 50% of the Ra-226 activity was associated with particles of size 5 micron and less. These size fractions are: coarse (+300 micron), medium (300 x 10 micron), and fine (-10 micron).
A series of mild chloride washing and flotation experiments showed that the +300 micron and 300 x 10 micron size fraction can be remediated below a criterion level of 6 pCi/gm. This criterion was based upon the 5 pCi/g plus background standard of 40 CFR 192. The criterion is often a relevant and appropriate requirement for Superfund. Also, chemical washing utilizing the chloride based lixiviants was found to be potentially useful for the remediation of -10 micron soil fraction. The radium from coarse fraction up to 50 mesh (300 micron) could be easily removed by screening and chloride washing. However, there was a difficulty in achieving a low radium value in the medium sized fractions using flotation. In order to accomplish this goal, several different reagents (specific to radium), effect of temperature and the effect of chloride washing were evaluated.
Experimental results demonstrated that a combination of reagent using (R-801+8-HQ) was uniquely specific for radium. Using the combined flotation reagent, a volume reduction of 80% with a radium level of 6 pCi/gm was obtained. The tests showed that with chloride washing of coarse materials (+300 micron) and flotation of 300 micron x 10 micron, the overall volume reduction of 80% can be accomplished. The typical results are summarized below:
The gross count analysis conducted at the University of Nevada, Reno was found to be consistent with the Ra-226 gamma scan data analyzed by Thermo NUtech on the selected samples.
On the basis of the test work conducted in this project, a flowsheet was developed which can be used for on-site demonstration. This report was submitted in fulfillment of Cooperative Agreement No. CR-826147 by the University of Nevada, Reno under the sponsorship of the United States Environmental Protection Agency. This report covers a period from 10/01/97 to 09/30/2000.