STRUCTURAL EFFECTS INN,N-DIALKYL AMIDES ON THEIR EXTRACTION BEHAVIOR TOWARD URANIUM AND THORIUM

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Abstract
Extraction behavior of four N,N-dialkylamides with varying alkyl substituents on the α carbon atom with respect to carbonyl group, viz. di-(2-ethylhexyl)acetamide (D2EHAA), di-(2-ethylhexyl)propionamide (D2EHPRA), di-(2-ethylhexyl)isobutyramide (D2EHIBA), and di-(2-ethylhexyl)pivalamide (D2EHPVA) toward nitric acid, U(VI), and Th(IV) has been investigated. The conditional acid uptake constant (K H) values for 1:1 species predominant in the acidity range 0.5–3 M HNO3 are in the following order: D2EHAA (0.28±0.03) > D2EHPRA (0.20±0.01) > D2EHIBA (0.15±0.04) > D2EHPVA (0.06±0.002). The stoichiometry of the extracted species of uranium conforms to UO2(NO3)2·2A (where A = amide). The conditional extraction constants (K ex.) for uranium were found to vary in the following order: 34.0±2.0 (D2EHAA) > 5.6±0.4 (D2EHPRA) > 1.2±0.1 (D2EHIBA)>0.51±0.03 (D2EHPVA). Third phase has been observed in the case of D2EHAA (≥1 M HNO3) and D2EHPRA (≥3 M HNO3) in the presence of macro concentration of thorium (220 g/L). The sepa...