Applications of Diglycolamide Based Solvent Extraction Processes in Spent Nuclear Fuel Reprocessing, Part 1: TODGA

Abstract

Over the last decade there has been much interest in the applications of diglycolamide (DGA) ligands for the extraction of the trivalent lanthanide and actinide ions from PUREX high active raffinates or dissolved spent nuclear fuel. Of the DGAs, the N,N,N',N'-tetraoctyldiglycolamide (TODGA) is the best known and most widely studied. A number of new actinide separation processes have been proposed based on extraction with TODGA. This review covers TODGA based processes and extraction data, specifically focusing on how phase modifiers have been used to increase metal loading and thus enhance the operating process envelopes. Effects of third phase formation and the organic phase speciation are reviewed in this context. Relevant aspects of the extraction chemistry of important solvents (TODGA-modifier-diluent combinations) are described and their performances demonstrated by a consideration of the published flowsheet tests. It is seen that modifiers are successfully enabling the use of TODGA in actinide separation processes but to date the identification and testing of suitable modifiers has been rather empirical. There is a growing understanding of the fundamental chemistry occurring in the organic phase and how that affects extractant speciation and metal loading capacity but studies are still needed if TODGAbased flowsheets are to become an industrially deployable option for minor actinide (MA) recovery processes.

Solvent extraction of intra-lanthanides using a mixture of TBP and TODGA in ionic liquid

“…Since TODGA is a neural tridentate extracting agent, which has a very strong affinity to f-elements, it can be used for a highly efficient extraction of trivalent lanthanides and minor actinides from highlevel liquid nuclear waste solutions. 5,[38][39][40] As expected, the distribution of Eu(III) ions between an aqueous 3 M HNO3 solution and an organic phase containing TODGA alone was high, i.e. 0.01 M TODGA diluted in [C4mim][Tf2N] ionic liquid or nonane yields DEu of 5.9 or 104.7, respectively ( Figure 1).…”

“…46 For the trivalent ions, the inner coordination sphere is completed by (TODGA)x(NO3)y, where x + y = 3 and x = 2 or 3. 40 EXAFS studies of TODGA extracted Pr(III), Nd(III), Eu(III), Yb(III), and Lu(III) showed that the inner coordination sphere of these lanthanide cations saturated by the organic ligand. [Ln(L)3] 3+ species is predominant.…”

Solvent extraction fractionation of manganese, cobalt, nickel and lithium using ionic liquids and deep eutectic solvents

“…We report herein the successive solvent extraction of manganese with N,N,N',N'-tetra(n-octyl) diglycolamide (TODGA) dissolved in imidazolium-based ionic liquids. TODGA extractant has a particular affinity for trivalent metals and particularly for the rare earth elements and actinides (Whittaker et al, 2018) when used in combination with a molecular diluent such as kerosene or toluene. Several studies reported unexpected higher distribution ratio values when using this extracting molecule in combination with ILs (Panja et al, 2012), (Pan and Hussey, 2013), (Turanov et al, 2016), (Zhang et al, 2014), (Shimojo et al, 2008), (Billard, 2013).…”

Stability studies of GANEX system under different irradiation conditions

“…The development and applicability of these extraction processes are limited by safety issues related to the resistance to radiation because they must work in continue operation in the recycling plant. For that reason, extractants like the diglicolamide TODGA (N,N,N 0 ,N 0 -tetraoctyldiglycolamide), which shows promising extraction properties and a good resistant to radiation, are being used widely for these applications [1][2][3][4][5][6][7].…”