Talspeak studies

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). 

Since HDEHP is both a cation exchanger and a coordinator in most extraction situations, coordinated water must be removed from the metal ion in the extraction. Because this sometimes leads to a slow reaction step, the kinetics of HDEHP extraction is important. The kinetics of the Talspeak process (14,15) has been investigated (63) the kinetics of Am(III) and Th(IV) extraction by HDEHP in an unstirred system has also been studied (64). 

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). 

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 ... 

Nilsson, M. and K.L. Nash. 2009. Trans-lanthanide extraction studies in the TALSPEAK system Investigating the effect of acidity and temperature. Solvent Extraction and Ion Exchange 27(3) 354-377. 

Aside from the subtle effect of the An-amine binding in the An-DTPA complexes of TALSPEAK, and the chloride, thiosulfate interaction with the actinides in ion-exchange studies, we have not discussed the proposal that there is of slightly greater covalency in actinide complexation (both by hydrophobic and hydrophilic ligands). In this section, the effect of binding of actinides to nitrogen and sulfur donor molecules is discussed within this model. 

Mechanism Study of TALSPEAK-Like Extraction of REEs... 

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