Treatment of high-level waste (HLW) stored in Hanford and Savannah River (SRS) Sites is a challenge because of its heterogeneous nature, complicated and variable composition, high alkalinity and high ionic strength. The Actinide Removal Process (ARP), involving sorption of actinides and 90Sr on modified monosodium titanate, and the Next-Generation Caustic-Side Solvent Extraction (NG-CSSX) process, which extracts 137Cs into an organic medium containing a calixarene ligand, are currently successfully employed in SRS. The efficiency of overall HLW treatment could be potentially improved by modification of NG-CSSX through introduction of organic ligands with soft N-donor sites for combined Cs and An separation. Tripodal pyrazoles and sulfonamides can potentially bind and extract actinides in alkaline conditions. In this work, we study binding and extraction of trivalent lanthanides as surrogates for actinides, by both theoretical and experimental means. Ion-pairing and solvation have been found to have significant effects on cation binding for tripyrazole ligands. Binding of several trivalent lanthanides by derivatives of 1,3,5-tris(pyrazolyl)-2,4,6-triethylbenzene in organic solvents was confirmed by fluorescence and 1H-NMR titrations. Variable substitution in the 3,5-positions of the pyrazole ring was shown to have dramatic effects in Ln(III) binding and sensing. Extraction of Sm(III) from alkaline aqueous solutions into chlorinated organic solvents by various sulfonamides has been investigated by ICP-OES and UV-Vis spectrophotometric methods. DFT calculations demonstrated high affinity of some of the pyrazole and sulfonamide ligands for Sm(III) and Am(III) binding with interesting binding modes.

Binding and extraction of trivalent lanthanides by tripodal sulfonamides and pyrazoles: structural, theoretical and spectroscopic studies

256th National Meeting (2018)

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