Extraction\nand Complexation of Fission Products with\nUnsymmetrical Phenanthroline Diamide Ligands from Simulated High-Level\nLiquid Waste

The extraction performance and complexation properties\nbetween\nsome typical fission products (FPs) with phenanthroline-based ligands <i>N</i><sup>2</sup>,<i>N</i>,<sup>2</sup><i>N</i><sup>9</sup>-triethyl-<i>N</i><sup>9</sup>-tolyl-1,10-phenanthroline-2,9-dicarboxamide\n(DE-ET-DAPhen) and <i>N</i><sup>2</sup>-ethyl-<i>N</i>,<sup>9</sup><i>N</i><sup>9</sup>-dioctyl-<i>N</i><sup>2</sup>-tolyl-1,10-phenanthroline-2,9-dicarboxamide (DO-ET-DAPhen)\nwere described in this work. The low distributions of Ln(III) observed\nin the solvent extraction study showed the potential of the ligands\nfor the separation of actinides and lanthanides in high-level liquid\nwaste (HLLW). Further extraction studies on other FPs showed that\nthe ligands could efficiently extract Pd(II) and Cd(II) using <i>n</i>-octanol as a diluent. Various methods including slope\nanalysis, <sup>1</sup>H NMR titration, UV–vis spectroscopic\ntitration, and single-crystal X-ray diffraction were adopted to explore\nthe complexation behavior of the ligands with target metal ions. The\ncomplexation study results indicated that the ligands formed 1:1 complexes\nwith Ln(III) in single-phase solutions, while 1:1 and 2:1 complexes\nwith Cd(II) and Pd(II) were detected. Meanwhile, the stability constants\n(log β) of the complexes measured through UV–vis spectroscopic\ntitration were reported. According to the diffraction data of the\nsingle crystals, the complex structures of [Ln(DE-ET-DAPhen)(NO<sub>3</sub>)<sub>3</sub>] (Ln = La, Tb, and Lu) and [Cd<sub>2</sub>(DE-ET-DAPhen)<sub>2</sub>(NO<sub>3</sub>)<sub>4</sub>] were proposed. The systematic\nstudy of the extraction and interaction between some typical FPs with\nthe ligands provides a comprehensive understanding of the ligands’\nproperties, which contribute to the development of the application\nprocess of the ligands in the reprocessing of HLLW.