New hydrophilic triple-charged cationic receptors for binding pertechnetate and perrenate anions in acidic aqueous...

One of the most complex and still unresolved problems in spent nuclear fuel (SNF) reprocessing is the separation of ⁹⁹Tc (a β-emitter, t_½ = 2.13 × 10⁵ years). Technetium is one of the most environmentally hazardous radionuclides contained in SNF in the form of the pertechnetate anion TcO₄^-. Many researchers around the world have been working for the past 30 years to create highly selective molecular receptors for its binding in aqueous solutions. In this study, we synthesized and thoroughly characterized a large series of new receptors containing three cationic pyridinium moieties. The structures of these compounds and their complexes with TcO₄^- and ReO₄^- anions were studied using a combination of physicochemical methods (X-ray diffraction, NMR, and mass spectrometry) coupled with quantum-chemical modeling based on density functional theory (DFT). Extraction tests of the new receptors showed that they effectively suppress TcO₄^- transfer into the organic phase during uranium and plutonium extraction using both the TODGA/F-3 and TBP/kerosene systems, opening up prospects for their use as hydrophobic masking agents for TcO₄^- binding in nitric acid during SNF reprocessing.