On the mechanism of trivalent actinide extraction in the system HDEHP—Lactic acid with DTPA
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The dependence of the distribution coefficients on the hydrogen ion concentration and HDEHP concentration in the process of extraction from lactic acid solutions in the presence of DTPA and without it has been investigated. It has been shown that when the lactate ion concentration is higher than 0.01M, Cm is extracted predominantly as the first lactate complex. The presence of DTPA does not change the extraction mechanism. Similarity of the observed regularities for trivalent actinides and lanthanides is confirmed by the extraction of Bk(III), Ce(III), and Eu(III). It is suggested that the nature of carbonic acid used in TALSPEAK-process greatly influences the efficiency of group separation of TPE and lanthanides. It is supported by some experimental data. The extraction and stability constants of the first lactate complex (Cm Lact2+) have been found to be: Ke=2, β 1 0 = 7,7 · 103. In the practical lactic acid concentration range (1 M) the unextractable complex, Cm Lact3, is also formed in the aqueous phase. The stability constant of this complex has been found to be β 3 0 = 1.2 · 107.
KeywordsLactic Acid Distribution Coefficient Stability Constant DTPA Carbonic Acid
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