Lanthanide actinide separation, Talspeak

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

Alkyl pyrocatechol extractants provide greater group separation factors. Eu/Am separation factors of 70 have been reported for a non-equilibrium extraction in the system 4-(a,(z-dioctylethyl)-pyrocatechol/NaOH/DTPA (diethylenetriamine-N, N, N, N, N-pentaacetic acid) (or DTPP - diethylenetriamine-N, N, N, N", N"-pentameth-ylenephosphonic acid) (Karalova et al. 1982). The separation factors are based mainly on the difference in the rates of the metal-DTPA (or DTPP) complexation equilibria for Eu and Am. They are therefore highly dependent on the contact time. A principal limitation of the practical application of such a separation scheme is the relatively long contact times (> 10 min) required for extraction. However, the slow equilibration compares favorably with that for other lanthanide-actinide separation processes (e.g. TALSPEAK, section 7). 

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. 

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). 

TALSPEAK A process for separating lanthanides from trivalent actinides. 

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-... 

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).

A promising application of HDEHP extraction appears to lie in the partitioning of actinides from lanthanides. The TALSPEAK process (Trivalent Actinide Lanthanide Separation by Phosphorus Reagent Extraction from Aqueous Komplexes) involves extraction of Ln s with HDEHP from an aqueous solution of a complex (such as DTPA) which has a high affinity for and represses extraction of the middle and heavier lanthanons and actinide elements most of all . The separation factor between the An s, Am and Cm ", and the Ln s exceeds 100. 

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