A H-Bonding and Electrostatic Interaction Combined Strategy for TcO₄^– Separation by a Nitrotriacetate-Derived Amine–Amide Extractant

Abstract

Effective and selective separation of technetium from acidic nuclear liquid waste is highly desirable for partitioning and transmutation but is of significant challenge. Highly efficient extraction of pertechnetate can be achieved by taking H-bonding and electrostatic interaction combined strategy. Base on this strategy, an amine-amide ligand NTAamide(<i>n</i>-Oct) was employed to extract TcO₄^- in HNO₃ solution. Using <i>n</i>-dodecane as a diluent, NTAamide(<i>n</i>-Oct) demonstrated excellent extractability and good selectivity toward TcO₄^- with a rapid extraction equilibrium that could be reached in less than 1 min. Its maximal loading capacity for TcO₄^- was almost 100 times as much as that of traditional amine extractant Aliquat-336 nitrate. Meanwhile, TcO₄^- could be efficiently stripped from the loaded organic phase by (NH₄)₂CO₃ solution. Slope analysis indicated the formation of a 1:1 complex of NTAamide(<i>n</i>-Oct) with TcO₄^-. The extraction conformed to the anion exchange extraction model, as confirmed by analyses of single-crystal X-ray diffraction, ¹H NMR titration, FTIR, and ESI-MS.