EXTRACTION OF SOME LANTHANIDES AND ACTINIDES BY 15-CROWN-5 THENOYLTRIFLUOROACETONE MIXTURE IN CHLOROFORM

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Abstract
The extraction of Eu3+, Tm3+, and Yb3+ by a mixture of thenoyltrifluoroacetone (HTTA) and 15-Crown-5 (15C5) in chloroform from a 0.1-ionic strength acetate buffer was investigated. Large enhancement in the extraction for these lanthanides was obtained when a mixture of the two extractants was used. Experimental data indicated that this enhancement is a result of the formation of a lanthanide adduct in the organic phase of the type Ln(TTA) 3° 2CE, where CE refers to a crown ether. The synergistic factors (S.F.), mixed extraction constants and formation constants of the different adducts in the organic phase were found to take the sequence Eu3+ > Tm3+ > Yb3+. Using 12-Crown-4 (12C4), no enhancement in the extraction was observed. This was explained in terms of the small cavity size of 12C4 relative to 15C5. The same system comprising HTTA-15C5 was also studied for the extraction of Pu4+, Am3+, Nd3+, and Er3+. Moderate enhancement was obtained for the extraction of Am3+ while no increase in the extraction was found for Pu4+.The metal concentration in the aqueous phase was found to largely affect the S.F. values for Nd3+ and Er3+.