Talspeak

Talspeak process, 6, 959,960 Tanabe-Sugano diagrams, 1, 238 Tannic acid in gravimetry, 1, 524 Tanning... 

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. 

Nilsson, M., Nash, K.L. 2007. Review article A review of the development and operational characteristics of the TALSPEAK process. Solvent Extr. Ion Exch. 25 (6) 665-701. 

Collins, E.D., Benker, D.E., Bailey, P.D. etal. 2005. Hot test evaluation of the TALSPEAK process. Proc. GLOBAL 2005, Tsukuba, Japan, October 9-13. Paper No. 186. 

There are various types of organic proton exchangers (34, 35, 38). Diesters of phosphoric acid, (RO)2P = 0(0H), phosphonic acids, R(RO)P = 0(0H), and phos-phinic acids, R2P = 0(0H), where R represents linear or branched alkyl or phenyl substituents, are the most common cation exchangers developed in liquid-liquid extraction for the extraction of trivalent 4/and 5/elements. They were initially developed for the American TALSPEAK and the Japanese DIDPA processes and have recently been introduced in the French DIAMEX-SANEX process. As for previously described NOPCs, these organophosphorus acids present oxygen-donor atoms (hard bases) in their structures and therefore will easily coordinate trivalent lanthanide and actinide cations, but they will not allow complete discrimination of the two families of elements. However, contrary to previously described neutral organophosphorus... 

In the reverse TALSPEAK process, the An(III) + Ln(III) fraction is first coextracted from a feed, the acidity of which has to be reduced to 0.1 M by denitration or nitric acid extraction. An(III) are then selectively stripped using DTPA in citric acid (1 M) at pH 3 (hence the name reverse TALSPEAK process), and the Ln(III) are finally stripped by 6 M HN03. Attempts to apply this TALSPEAK variant to the treatment of actual UREX + raffinates are reported in the literature, but they involve several steps. The problematic Zr and Mo elements are first removed by direct extraction with HDEHP (0.8 M in di-iso-propylbenzene) from the high-acidity raffinate stream arising from the UREX + co-decontamination process (238). The remaining fission products and actinides can then be concentrated by acid evaporation and denitration processes. This concentrate is further diluted to a lower acidity (e.g., [HN03] = 0.03 M) to allow the coextraction of An(III) and Ln(III) by the TALSPEAK solvent. 

Di(2-ethylhexyl) phosphoric acid, used in the TALSPEAK process, which extracts trivalent metallic cations at low acidity by proton exchange. 

As in the SETFICS and TALSPEAK processes, the DIAMEX-SANEX/HDEHP process involves selectively back-extracting the trivalent actinides by a hydrophilic polyamino-carboxylate complexing agent, HEDTA, in a citric acid buffered solution (pH 3). However, the combination of HDEHP and DMDOHEMA at high acidity promotes the coextraction of some block transition metals, such as Pd(II), Fe(III), Zr(IV), and Mo(VI), which must be dealt with by specific stripping steps (as described on Figure 3.26) that increase the total volume of the output streams ... 

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). 

The same protective effect was observed in the TALSPEAK process, where the lactic acid added to the aqueous phase reduced the degradation of DTPA (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). 

An initial experiment involving the treatment of small irradiated Pu/Al targets for the production of americium 243 and curium 244 was carried out in France in 1968 (2). The chemical process was based essentially on the use of a system comparable to the Talspeak system. After plutonium extraction by a 0.08 M trilaurylammonium nitrate solution in dodecane containing 3 vol % 2-octanol, the actinides (americium, curium) were coextracted with a fraction of the lanthanides by a 0.25 M HDEHP -dodecane solvent from an aqueous solution previously neutralized by A1(N0 ) x(0H)x and adjusted to 0.04 M DTPA. The actinides were selectively stripped by placing the organic phase in contact with an aqueous solution of the composition 3 M LiN0 -0.05 M DTPA. While this experiment achieved the recovery of 150 mg of americium 243 and 15 mg of curium 244 with good yields, the process presented a drawback due to the slow extraction of Al(III) which saturates the HDEHP. This process was therefore abandoned. 

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