Design and synthesis of the next generation of crown ethers for waste separations: An interlaboratory comprehensive proposal. 1997 annual progress report

'The purpose of this task is to undertake the design, synthesis, and characterization of the next generation of crown ethers for metal-ion separations applicable to the US Department of Energy''s (DOE''s) environmental needs. The general target problem is the removal of alkali and alkaline-earth metal contaminants from certain environmental and waste streams. Although not a radioactivity hazard, Li{sup +} ions leaching from burial sites containing more than 12 metric tons of lithium compounds contaminate the groundwater at the Oak Ridge Y-12 Plant and have raised noncompliance concerns because of the resultant toxicity to aquatic biota. A more highly visible problem has been treatment of high-level wastes stored in underground tanks at Oak Ridge National Laboratory (ORNL), Idaho National Engineering and Environmental Laboratory, and especially the Hanford Site. The fission products {sup 90}Sr and {sup 137}Cs have been explicitly targeted for removal by the following DOE programs: the Office of Environmental Management, the Office of Science and Technology, the Tank Waste Remediation System, the Tanks Focus Area, and the Efficient Separations and Processing Cross-Cutting Program. These seemingly ubiquitous fission products also appear in soil and groundwater at numerous DOE sites. In addition, radium has recently been named as a target contaminant at the Niagara Falls Storage Site. Unfortunately, the separations technologies needed to address these problems either do not exist or exhibit substantial deficiencies. Established techniques such as solvent extraction and ion exchange certainly have a strong role to play, especially as enhanced with the use of the new highly selective metal-ion hosts such as crown ethers and calixarenes. Recently applied results in the United States, France, Russia, and elsewhere have demonstrated the effective performance of crown ethers under realistic or actual process conditions for the removal of alkali and alkaline-earth metal ions from waste, including high-levelnuclear waste. From these results, one can readily appreciate how improvements in selectivity and extraction strength can immediately translate to improvements and cost savings in existing technologies. One can also envision extending crown-ether-based chemistry to solve other problems, such as groundwater remediation. Achieving these ends will require the design and synthesis of new crown compounds with next-generation capabilities, which will in turn require efforts to build upon the current base of fundamental knowledge pertaining to host-guest chemistry, solvent extraction, and ion exchange.