Carbonate heap leach of uranium-contaminated soils
- Los Alamos National Lab., NM (United States); and others
A new approach to removal of uranium from soils based on existing heap leach mining technologies proved highly effective for remediation of soils from the Fernald Environmental Management Project (FEMP) near Cincinnati, Ohio. In laboratory tests, remediation of uranium-contaminated soils by heap leaching with carbonate salt solutions was demonstrated in column experiments. An understanding of the chemical processes that occur during carbonate leach of uranium from soils may lead to enhancement of uranium removal. Carbonate leaching requires the use of an integrated and closed circuit process, wherein the leach solutions are recycled and the reagents are reused, resulting in a minimum secondary waste stream. Carbonate salt leach solution has two important roles. Primarily, the formation of highly soluble anionic carbonate uranyl species, including uranyl dicarbonate (UO{sub 2}CO{sub 3}{sub 2}{sup =}) and uranyl tricarbonate (UO{sub 2}CO{sub 3}{sub 3}{sup 4-}), allows for high concentration of uranium in a leachate solution. Secondly, carbonate salts are nearly selective for dissolution of uranium from uranium contaminated soils. Other advantages of the carbonate leaching process include (1) the high solubility, (2) the selectivity, (3) the purity of the solution produced, (4) the relative ease with which a uranium product can be precipitated directly from the leachate solution, and (5) the relatively non-corrosive and safe handling characteristics of carbonate solutions. Experiments conducted in the laboratory have demonstrated the effectiveness of carbonate leach. Efficiencies of uranium removal from the soils have been as high as 92 percent. Higher molar strength carbonate solutions ({approx}0.5M) proved more effective than lower molar strength solutions ({approx} 0.1M). Uranium removal is also a function of lixiviant loading rate. Furthermore, agglomeration of the soils with cement resulted in less effective uranium removal.
- Research Organization:
- Univ. of Arizona, Tucson, AZ (United States). Coll. of Engineering and Mines; New Mexico State Univ., Las Cruces, NM (United States); Waste-Management Education and Research Consortium (WERC), Las Cruces, NM (United States); US Department of Energy (USDOE), Washington DC (United States)
- OSTI ID:
- 111627
- Report Number(s):
- CONF-940225-Vol.3; TRN: 95:021723
- Resource Relation:
- Conference: Waste management `94: working towards a cleaner environment, Tucson, AZ (United States), 27 Feb - 3 Mar 1994; Other Information: PBD: 1994; Related Information: Is Part Of Technology and programs for Radioactive Waste Management and Environmental Restoration. Volume 3; Post, R.G. [ed.] [Arizona Univ., Tucson, AZ (United States). Coll. of Engineering and Mines]; PB: 857 p.
- Country of Publication:
- United States
- Language:
- English
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