Talspeak separation

Fig. 3. Distribution ratios for trivalent lanthanides and actinides for the TALSPEAK separation system (0.3 M HDEHP/diisopropylbenzene/l.OM lactic acid-0.05 M DTPA-pH 3.0), from Weaver and Kappelmann (1968).

Weaver, B.S., Kappelmann, F.A. 1964. Talspeak A new method of separating americium and curium from lanthanides by extraction from an aqueous solution of aminopo-lyacetic acid complex with a monoacidic phosphate or phosphonate. ORNL-3559. 

Persson, G., Svantesson, I., Wingefors, S., Liljenzin, J-0.1984. Hot test of a TALSPEAK procedure for separation of actinides and lanthanides using Recirculating DTPA-Lactic acid solution. Solvent Extr. Ion Exch. 2 (1) 89-113. 

Svantesson, I. 1984. A reversed TALSPEAK process for the separation of actinides from lanthanides. Thesis. Chalmers University of Technology, Goteborg. 

Del-Cul, G.D., Bond, W.D., Toth, L.M. et al. 1994. Citrate based TALSPEAK lanthanide-actinide separation process. ORNL/TM-12785. 

Historically, pairs of processes have been developed throughout the world to achieve An(III)/Ln(III) partitioning TRUEX + TALSPEAK in the United States, TRPO + CYANEX in China, DIDPA + DIDPA in Japan, and DIAMEX + BTP or DIAMEX + ALINA in Europe, but cross combinations of processes are possible. The one-cycle processes (e.g., SETFICS and DIAMEX-SANEX/HDEHP) appear more attractive and more compact than the two-cycle processes, as they do not use two different solvent loops to carry out the separation of An(III) from Ln(III), but they sometimes generate much larger aqueous streams than the feed input. 

Di(2-ethylhexyl) phosphoric acid (HDEHP) is an extractant molecule used for An(III)/Ln(III) separation. Used in TALSPEAK-type processes in a mixture with TBP, or in the DIAMEX-SANEX process in a mixture with a malonamide (154-157), it has also been proposed, in a mixture with TBP, to remove strontium from PUREX acid waste solution in the Hanford B plant (158). Therefore, numerous studies have focussed on the radiolytic degradation of HDEHP and its effects on the extraction of Sr(II), lanthanides(III), and actinides(III) (10, 158-163). 

The y-irradiation of HDEHP-n-paraffins in contact with TALSPEAK-type aqueous phase at pH 3 (DTPA + lactic acid) increased DAm and DLn, and slightly decreased the separation factors SFLn/Am (12, 161). The effect was stronger when lactic acid was replaced by NaN03, as presented in Figure 8.3 (161). 

Tachimori, S., Nakamura, H. 1979. Radiation effects on the separation of lanthanides and transplutonides by the Talspeak-type extraction. J. Radioanal. Chem. 52(2) 343-354. 

While the Talspeak system allows the best separation of the group, systems using TBP or TLAHNO- allow good separation of americium with light rare earths whicn, as is well known, make up the bulk of the mass of lanthanides present in the irradiated targets (14). 

TALSPEAK A process for separating lanthanides from trivalent actinides. 

Extraction processes (TRUEX, PUREX, Talspeak, DIAMEX, PARC, etc.) generally involve complexation of transplutonium elements by alkyl phosphines, phosphine oxides, phosphoric acids, carbamoyl phosphonates, diamides, and thiophosphinates in aqueous/organic extractions, within derivatized solid supports, or on coated particles. There are excellent reviews of the processes and significant complexes by Mathur et al. and selected chapters in The Chemistry of the Actinide and Transactinide Elements to be published in 2003. " Work on the separation for nuclear waste management in the United States, France, and Russia have been reviewed. " ... 

The separation of transplutonium elements from the lanthanides constitutes the delicate phase of chemical treatment, owing to their comparable affinities for the usual extractants HDEHP, TBP and TLAHNO3. Among all the systems described in the literature and covered by a recently published critical compilation (JO), we selected those which appeared to be much suitable for adaptation to extraction chromatography the Talspeak process (7) and the... 

The aqueous strip solution will form directly the feed solution of the Am, Cm/RE countercurrent separation step, to be performed according to the operating conditions of the TALSPEAK process (15). The presence of a complexing agent like DTPA will prevent the extraction of Am and Cm whereas the RE will be more easily extracted by di(2-ethylhexyl)phosphoric acid (HDEHP) in n-dodecane (pH = 3). 

Also in the case of the TBP process, only simulated HAW solutions have been until now used to study the process feasibility. Results have already been reported (9), which indicated that separation yields of about 99.9% can be obtained for Am after three successive extraction stages operating with a concentrated HAW solution adjusted to 0.1 — 0.2 M HN03, 0.65 M AI(N03)3 and 1.3 M NaN03. The back-extraction of all the actinides and RE from loaded TBP (30% in n-dodecane) was carried out by means of Na5 DTPA-glycolic acid solution which can be then used directly to separate Am and Cm from RE according to the Talspeak process (15). 

The main purpose of the separation of Am-Cm from RE by the well known Talspeak process is to liberate the RE fraction from actinides. The acceptable resi-duel RE content in the actinide stream on the contrary will depend widely on the further destination of the latter. It is in any way not a critical point. Therefore, high A/O ratios and an efficient aqueous scrub section must provide for an as low as possible extraction of Am and Cm. For these operations mixer-settler batteries seem to offer the most convenient approach, taking into account radiation levels, flow rates and extraction (and back-extraction) kinetics. 

Studies (1, 2, 3, 4) on the separation of americium-curium from lanthanide elements indicate that both cation exchange chromatography (8, 9) and the Talspeak solvent extraction process (U), 11) are promising methods. Only the most recent work at Oak Ridge National Laboratory is reported in this paper. Potential chemical processes for americium-curium removal and evaluations of their feasibility have been reported previously (U 2, 3, 4). The most recent experimental work carried out includes the following ... 

In the Talspeak process, the separation of trivalent actinides and lanthanides is accomplished by coextracting the two groups of elements into di(2-ethyl hexyl)phosphoric acid (HDEHP) from a carboxylic acid solution and then partitioning the acti-... 

Table III. Effect of H2MEHP Concentration on the Separation Factor for Americium and Europium in Talspeak Partitioning...

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