title: Excellent selectivity for actinides with a tetradentate 2,9-diamide-1,10-phenanthroline ligand in highly acidic solution: a hard-soft donor combined strategy.
abstract: In this work, we reported a phenanthroline-based tetradentate ligand with hard-soft donors combined in the same molecule, N,N'-diethyl-N,N'-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen), for the group separation of actinides over lanthanides. The synthesis and solvent extraction as well as complexation behaviors of the ligand with actinides and lanthanides are studied experimentally and theoretically. The ligand exhibits excellent extraction ability and high selectivity toward hexavalent, tetravalent, and trivalent actinides over lanthanides in highly acidic solution. The chemical stoichiometry of Th(IV) and U(VI) complexes with Et-Tol-DAPhen is determined to be 1:1 using X-ray crystallography. The stability constants of some typical actinide and lanthanide complexes of Et-Tol-DAPhen are also determined in methanol by UV-vis spectrometry. Density functional theory (DFT) calculations reveal that the An-N bonds of the Et-Tol-DAPhen complexes have more covalent characters than the corresponding Eu-N bonds, which may in turn lead to the selectivity of Et-Tol-DAPhen toward actinides. This ligand possesses merits of both alkylamide and 2,9-bis-(5,6-dialkyl-1,2,4-triazin-3-yl)-1,10-phenanthroline (R-BTPhen) extractants for efficient actinide extraction and the selectivity toward minor actinides over lanthanides and hence renders huge potential opportunities in high-level liquid waste (HLLW) partitioning.
authors.affiliation: Key Laboratory of Nuclear Radiation and Nuclear Energy Technology and Key Laboratory For Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences , Beijing 100049, P.R. China.
authors.forename: Cheng-Liang
authors.initials: CL
authors.lastname: Xiao
authors.forename: Cong-Zhi
authors.initials: CZ
authors.lastname: Wang
authors.forename: Li-Yong
authors.initials: LY
authors.lastname: Yuan
authors.forename: Bin
authors.initials: B
authors.lastname: Li
authors.forename: Hui
authors.initials: H
authors.lastname: He
authors.forename: Shuao
authors.initials: S
authors.lastname: Wang
authors.forename: Yu-Liang
authors.initials: YL
authors.lastname: Zhao
authors.forename: Zhi-Fang
authors.initials: ZF
authors.lastname: Chai
authors.forename: Wei-Qun
authors.initials: WQ
authors.lastname: Shi