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Abstract
Two bisdiglycolamides (BisDGAs) of N,N,N′′′,N′′′-tetrabutyl-Nʹ,N′′-ethidene bisdiglycolamide (TBE-BisDGA) and N,N,N′′′,N′′′-tetrabutyl-Nʹ,N′′-m-xylylene bisdiglycolamide (TBX-BisDGA) were synthesized. Their extraction behaviors of Eu(III) and Am(III), as well as nitric acid were investigated from nitric acid medium by using n-octanol as diluent. Nitric acid is extracted as the form of HNO3·(BisDGAs)0.6 by BisDGAs and the conditional acid uptake constants of TBE-BisDGA and TBX-BisDGA were 0.26 and 0.10, respectively. The distribution ratios of Eu(III) and Am(III) increased with the increase of nitric acid and extractant concentration, whilst decreased with temperature rise. TBX-BisDGA had a stronger extraction power for Eu(III) and Am(III) than TBE-BisDGA. Both of the extractants displayed a higher affinity toward Eu(III) than Am(III). In the examination of the acidity range from 0.5 to 5.0 M, a maximum separation factor SFEu(III)/Am(III) can reach 8.0 at 3.0 M HNO3 for TBX-BisDGA; and 10 at 4.0 M HNO3 for TBE-BisDGA, respectively. Slope analyses showed that Eu(III) and Am(III) are extracted as di-solvated species by TBX-BisDGA or TBE-BisDGA. The extraction mechanism was described and the apparent extraction equilibrium constant as well as Gibbs free energy change, enthalpy change and entropy change were presented. In addition, their Eu(III) complexes were analyzed by using infrared spectra.