High Complexation Selectivity of U(VI) over Rare Earths by N,N ‐Dihexyl‐2‐ethylhexanamide (DH2EHA): Experimental and Theoretical Evidence

A new amide based extractants namely N,N ‐Dihexyl‐2‐ethylhexanamide (DH2EHA) has been synthesized and characterized for extraction of uranium. The formation of UO 2 (NO 3 ) 3 .2DH2EHA complex in the organic phase was established by X‐ray diffraction. The X‐ray structure was further corroborated by the density functional theoretical calculation. Furthermore, DFT approach was adopted to explain the relative stability of uranium and rare earth complex with DH2EHA by determining the free energy of extraction. The calculated selectivity trend from free energy of extraction using 1:2 stoichiometry for Nd and Yb was found to be Yb 3+ >UO 2 2+ >Nd 3+ which does not follow the experimental trend of UO 2 2+ >Nd 3+ >Yb 3+ . But, the correct selectivity order is recovered after consideration of 1:3 stoichiometry for Nd and Yb. Thus, the correct selectivity order was understood from a combined experimental and density functional theoretical studies.