Highly efficient diglycolamide-functionalized dendrimers for the sequestration of tetravalent actinides: solvent extraction and theoretical studies

Abstract

Two diglycolamide (DGA) functionalized poly(propylene imine)diaminobutane dendrimers, first generation (Gen I) and second generation (Gen II), termed as L_I and L_II, were used for the extraction of the tetravalent actinide ions Np⁴⁺ and Pu⁴⁺ from nitric acid medium. The metal ion extraction followed a ‘solvation’ type mechanism showing increasing metal ion extraction with increasing nitric acid concentration with species of the type: M(NO₃)₄·L (M = Np or Pu) with some contribution of M(NO₃)₄·2L for Pu. Pu⁴⁺ formed much stronger complexes with both DGA-dendrimer ligands as compared with Np⁴⁺, as reflected in their two-phase extraction constants and higher ΔH values, attributed to its higher ionic potential. Binding of the metal ions was to one ‘DGA pocket’ in each of the dendrimers. The structure and bonding analysis was done on the basis of DFT studies.