Improved Method to Clean-up Legacy Radioactive Waste
Chemistry provides a route to selective binding and extraction of radioactive cesium
Fundamental separations science research developed an understanding of the synthesis, structure, and thermodynamics of molecules that selectively bind radioactive cesium-137, a troublesome fission product, allowing trace cesium to be selectively separated from concentrated salt solution.
Impact: The calixarene extractant’s extraordinary selectivity for cesium ions versus sodium ions provides the necessary selectivity for removal of cesium from legacy radioactive waste tanks; it was developed into a commercial process and has been used in a pilot plant to clean-up over 3 million gallons of high-level salt-waste. A full-scale $1.7B plant is under construction at the Savannah River Site.
The BOBCalix6 (Calix[4]arene-bis(t-octylbenzo-crown-6) molecule shown with a positively charge cesium ion held inside one of its cavities.
Summary: During the Cold War, nuclear weapons production created many radioactive fission byproducts, a major one being cesium-137. These by-products continue to be stored in tanks at the facilities where the processing took place. The mixture of materials, consisting of a small mass of toxic radionuclides in 90 Mgal of inorganic salts, in these tanks make clean up particularly challenging, a truly needle-in-the-haystack type of problem. Fundamental research in separations science at Oak Ridge National Laboratory identified a molecule that selectively binds to cesium called BOBCalixC6. The research focused on the principles of host-guest chemistry, emphasizing the synthesis of tailored host molecules such as crown ethers and calixarenes that selectively bind cesium. By studying the structure of crown ethers and calixarenes complexes with alkali metal ions and the thermodynamics of ion binding and extraction, the researchers opened a door to exploiting the potential of these novel molecules for the cesium separation problem. Applied research incorporated BOBCalixC6 into the Caustic Side Solvent Extraction (CSSX) process and provided critical insights toward overcoming technical problems and improving the technology for scale-up and maturation. Partnerships with Argonne, Savannah River, Pacific Northwest, and Idaho National Laboratories were key in the engineering and scale-up. Since 2008, a pilot plant based on CSSX has successfully processed almost three million gallons of high-level salt-wastes at the Savannah River Site. A full-scale facility, the Salt-Waste Processing Facility (SWPF), is moving towards deployment; this facility will play a key role in the treatment and disposition of 34 million gallons of high-level salt waste at this site ($10B life cycle). Even before the SWPF is commissioned, the next-generation CSSX process, also a spin-off of BES sponsored research, offers such dramatic improvements in waste decontamination and processing rate that it will be implemented in the pilot facility in 2013. Ultimately, the treatment and disposition these wastes will enable tank closure and complete one of DOE’s Office of Environmental Management’s highest environmental priorities at significant cost savings.
he Modular Caustic Side Solvent Extraction (CSSX) Unit nearing completion at the Savannah River Site.
Contacts: Bruce Moyer, ORNL, moyerba@ornl.gov; Phillip Britt, ORNL, brittpf@ornl.gov.
Publication(s):
Journal articles:
Y. Deng, R. A. Sachleben, and B. A. Moyer, "Equilibrium Aspects of the Extraction of Cesium Nitrate by Dicyclohexano-21-crown-7, Dibenzo-21-crown-7, and Bis-[tert-alkylbenzo]-21-crown-7," J. Chem. Soc., Faraday Trans. 1995, 23, 4215-4222.
R. A. Sachleben, Y. Deng, and B. A. Moyer, "Ring-Size and Substituent Effects in the Solvent Extraction of Alkali Metal Nitrates by Crown ethers in 1,2-Dichloroethane in 1-Octanol," Solvent Extr. Ion Exch. 1996, 14(6), 995-1015.
R. A. Sachleben, Y. Deng, and B. A. Moyer, "Ion-Pair Extraction of Alkali Metal Nitrate Salts by Lipophilic Benzo-Substituted 24-Crown-8 Ethers," Sep. Sci. Technol. 1997, 32, 275-284.
J. C. Bryan, L. H. Delmau, B. P. Hay, J. B. Nicholas, L. M. Rogers, R. D. Rogers, and B. A. Moyer, "Cesium Recognition by Supramolecular Assemblies of 2-Benzylphenol and 2-Benzylphenolate," Structural Chem. 1999, 10(3), 187-203.
R. A. Sachleben, A. Urvoas, J. C. Bryan, T. J. Haverlock, B. P. Hay, and B. A. Moyer, "Dideoxygenated Calix[4]arene Crown-6 Ethers Prefer the 1,3-Alternate Conformation and Exhibit Enhanced Selectivity for Cesium over Potassium and Rubidium," J. Chem. Soc., Chem. Commun. 1999, 1751-1752.
Sachleben, R. A.; Bonnesen, P. V.; Descazeaud, T.; Haverlock, T. J.; Urvoas, A.; Moyer, B. A. Surveying the Extraction of Cesium Nitrate by 1,3-Alternate Calix[4]arene Crown-6 Ethers in 1,2-Dichloroethane. Solvent Extr. Ion Exch. 1999, 17, 1445–1459.
K. Kavallieratos, R. A. Sachleben, G. J. Van Berkel, and B. A. Moyer, "Novel Dual-Host Approach in Ion Pair Extraction – A Simple Tripodal Nitrate Host Facilitates CsNO3 Transfer to 1,2-Dichloroethane by a Large Crown Ether," Chem. Commun. 2000, 187-188.
Cai, M.; Marlow, A. L.; Fettinger, J. C.; Fabris, D.; Haverlock, T. J.; Moyer, B. A.; Davis, J. T. Binding Cesium Ion with Nucleoside Pentamers. Templated Self-Assembly of an Isoguanosine Decamer. Angew. Chem., Int. Ed. 2000, 39, 1283–1285.
Levitskaia, T. G.; Bryan, J. C.; Sachleben, R. A.; Lamb, J. D.; Moyer, B. A. A Surprising Host-Guest Relationship between 1,2-Dichloroethane and the Cesium Complex of Tetrabenzo-24-Crown-8. J. Am. Chem. Soc. 2000, 122, 554–562.
Levitskaia, T. G.; Macdonald, D. M.; Lamb, J. D.; Moyer, B. A. Prediction of the Carrier-Mediated Cation Flux through Polymer Inclusion Membranes via Fundamental Thermodynamic Quantities: Complexation Study of Bis(dodecyloxy)calis[4]arene-crown-6 with Alkali Metal Cations. Phys. Chem. Chem. Phys. 2000, 2, 1481–1491.
Kavallieratos, K.; Danby, A. M.; Van Berkel, G. J.; Kelly, M. A.; Sachleben, R. A.; Moyer, B. A.; Bowman-James, K. Enhancement of CsNO3 Extraction in 1,2-Dichloroethane by Tris(2-aminoethyl)amine Triamide Derivatives via a Dual-Host Strategy. Anal. Chem. 2000, 72 (21), 5258–5264.
Nash, K. L.; Barrans, R. E.; Chiarizia, R.; Dietz, M. L.; Jensen, M. P.; Rickert, P. G.; Moyer, B. A.; Bonnesen, P. V.; Bryan, J. C.; Sachleben, R. A. Fundamental Investigations of Separations Science for Radioactive Materials. Solvent Extr. Ion Exch. 2000, 18(4), 605–631 (Invited Review).
T. G. Levitskaia, R. A. Sachleben, J. C. Bryan, B. A. Moyer, “Synthesis, Structure, and Extraction Behavior of 4,5’,4”,4’”-Tetra-t-butylbenzo-24-crown-8,” J. Chem. Soc., Perkin Trans. 2001, 2, 808-814.
T. G. Levitskaia, K. L. Fox, J. D. Lamb, and B. A. Moyer, “Selective Carrier-Mediated Cesium Transport Through Polymer Inclusion Membranes by Calix[4]arene-Crown-6 Carriers from Complex Aqueous Mixtures,” Radiochim. Acta 2002, 90, 43-52.
Duchemin, C. R.; Engle, N. L.; Bonnesen, P. V.; Haverlock, T. J.; Delmau, L. H.; Moyer, B. A. Solvatochromic Solvent Polarity Measurements of Alcohol Solvent Modifiers and Correlation with Cesium Extraction Strength, Solvent Extr. Ion Exch. 2001, 19(6), 1037-1058.
J. C. Bryan, T. Chen, T. G. Levitskaia, T. J. Haverlock, C. E. Barnes, and B. A. Moyer, “Solvation of Calix[4]arene-bis-crown-6 Molecules,” J. Inclusion Phenom. 2002, 42, 241-245.
R. A. Sachleben, J. C. Bryan, G. Das, T. Descazeaud, Y. Sun, and B. A. Moyer, “Synthesis, Structure, and Extraction Properties of paco-Calix[4]arene Crown-6 Ethers,” J. Inclusion Phenom. 2002, 43, 55-64.
Haverlock, T. J.; Mirzadeh, S.; Moyer, B. A. Selectivity of calix[4]arene-bis(benzocrown-6) in the complexation and transport of francium ion. J. Am. Chem. Soc. 2003, 125(5), 1126–1127.
Levitskaia, T. G.; Bonnesen, P. V.; Chambliss, C. K.; Moyer, B. A. "Synergistic Pseudo-Hydroxide Extraction: Synergism and Anion Selectivity in Sodium Extraction Using a Crown Ether and a Series of Weak Lipophlilic Acids," Anal. Chem. 2003, 75(3), 405–412.
Sachleben, R. A.; Bryan, J. C.; Engle, N. L.: Haverlock, T. J.; Hay, B. P.: Urvoas, A.; Moyer, B. A. Rational Design of Cesium-Selective Ionophores: Dihydrocalix[4]arene Crown-6 Ethers, European J. Org. Chem. 2003, 4862–4869.
Delmau, L. H.; Lefranc, T. J.; Bonnesen, P. V.; Bryan, J. C.; Presley, D. J.; Moyer, B. A. Fundamental Studies Regarding Synergism Between Calix[4]arene-bis(tert-octylbenzo-crown-6) and Alcohol Modifiers in the Solvent Extraction of Cesium Nitrate. Solvent Extr. Ion Exch. 2005, 23, 23–57.
Moyer, B. A.; Bonnesen, P. V.; Custelcean, R.; Delmau, L. H.; Hay, B. P. Strategies for Using Host-Guest Chemistry in the Extractive Separations of Ionic Guests. Kem. Ind. 2005, 54 (2), 65–87 (Invited review).
Levitskaia, T. G.; Maya, L.; Van Berkel, G. J.; Moyer, B. A. Anion Partitioning and Ion-Pairing Behavior of Anions in the Extraction of Cesium Salts by 4,5"-bis(tert-octylbenzo)dibenzo-24-crown-8 in 1,2-Dichloroethane. Inorg. Chem. 2007, 46 (1), 261–272.
Kříž, J.; Dybal, J.; Makrlík, E.; Vaňura, P.; Moyer, B. A. Interaction of Cesium Ions with Calix[4]arene-bis(t-octylbenzo-18-crown-6): NMR and Theoretical Study. J. Phys. Chem. B 2011, 115, 7578–7587.
Kim, S. K.; Vargas-Zúñiga, G. I.; Hay, B. P.; Young, N. J.; Delmau, L. H.; Masselin, C.; Lee, C.-H.; Kim, J. S.; Lynch, V. M.; Moyer, B. A.; Sessler, J. L. Controlling Cesium Cation Recognition via Cation Metathesis within an Ion Pair Receptor. J. Am. Chem. Soc. 2012, 134(3), 1782–1792.
Makrlík, E.; Toman, P.; Vaňura, P.; Moyer, B. A. Interaction of the Cesium Cation with Calix[4]arene-bis(t-octylbenzo-18-crown-6): Extraction and DFT Study. J. Mol. Struct. 2012, 1033, 14–18
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