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

One of the most complex and still unresolved problems in spent nuclear fuel (SNF) reprocessing is the separation of 99Tc (a β-emitter, t½ = 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.