Extraction Behavior of Ln(III) Ions by T2EHDGA/n-Dodecane from Nitric Acid and Sodium Nitrate Solutions |
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| Authors: | Emily Campbell Vanessa E Holfeltz Gabriel B Hall Kenneth L Nash Gregg J Lumetta |
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| Affiliation: | 1. Actinide Science Team, Pacific Northwest National Laboratory, Richland, Washington;2. Chemistry Department, Washington State University, Pullman, Washington;3. School of Nuclear Science and Engineering, Oregon State University, Corvallis, OR;4. Chemistry Department, Washington State University, Pullman, Washington |
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| Abstract: | The diglycolamide extractant T2EHDGA has proven to be promising for the separation of lanthanides and minor actinides in high-level nuclear waste reprocessing. This neutral extractant has shown significant extraction capacity for HNO3 into the nonpolar organic phase, along with hyper-stoichiometric nitrate dependence on extraction of trivalent f-elements. The transport behavior of T2EHDGA/n-dodecane toward trivalent lanthanides is not well understood. This work found a significant increase in distribution ratios for Eu(III) extracted from aqueous HNO3 media compared with that from NaNO3. The extraction of Eu(III) from HNO3 results in a different thermodynamic product than predicted by classic solvent extraction of 3:1 ligand–metal complex as observed with NaNO3 in FTIR and UV-vis spectroscopy. Experimental distribution measurements in conjunction with mass-action modeling using the solvent extraction modeling program SXLSQI suggest participation of 1 to 2 HNO3 molecules in the Eu(III)/T2EHDGA complex upon extraction from HNO3 media, indicative of a mechanism change responsible for the enhanced extraction behavior toward lanthanides in the presence of HNO3. |
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| Keywords: | ALSEP T2EHDGA speciation model trivalent actinides and lanthanides extraction constant |
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