Synergistic Extraction of U(VI), Th(IV), and Lanthanides(III) from Nitric Acid Solutions Using Mixtures of TODGA and Dinonylnaphthalene Sulfonic Acid

The extraction of U(VI), Th(IV), and lanthanides(III) from aqueous nitric acid solutions with mixtures of N,N,N,N-tetra(n-octyl)diglycolamide (TODGA) and dinonylnaphtalene sulfonic acid (HDNNS) in n-decane has been investigated. The extraction efficiency of U(VI), Th(IV), and Ln(III) ions is greatly enhanced by addition of HDNNS to an organic phase containing TODGA. The synergistic effect arises from the higher hydrophobicity of U(VI), Th(IV), and Ln(III) extracted species formed by TODGA and DNNS- anions as compared to those formed by TODGA and NO3- ions as counter anions. The synergistic effect for U(VI), Th(IV), and Ln(III) extraction from aqueous nitric acid solutions with mixtures of TODGA and HDNNS becomes weaker when the acidity of the aqueous phase increases. A high synergistic enhancement is accompanied with a high selectivity of Ln(III) extraction from nitric acid solutions.