The Synthesis Of Pyrazolamide And Calix-crown Extractants And Their Solvent Extraction For Ln³⁺ And Cs⁺

The key components of the high-level radioactive liquid waste（HLW）are minor actinides（MA）and fission products（FP）.If ¹³⁷Cs,⁹⁰Sr and ²⁴¹Am are removed,the heat release by HLW may be significantly reduced,which may decrease the heat releasing power per unit mass of vitrified HLW,thus increase the accommodation density of the geological disposal repository for HLW and significantly reduce the final disposal cost.In addition,the separation of trivalent actinide ions(An³⁺)from HLW is one of the keys to the"separation-transmutation"strategy,and the difficulty lies in An³⁺separation from trivalent lanthanide ions(Ln³⁺).Solvent extraction has been the preferred solution for the separation issues related to the nuclear fuel cycle due to its advantages such as continuous and convenient operation,and the key lies in the selection of a suitable extractant for the concerned separation.For the separation of Ln³⁺and An³⁺from HLW,two structurally novel pyrazole-amide based polyfunctional ligands were designed and synthesized:Carboxamidethyl-（1H-3-hexyl pyrazol-5-yl）ether（L₁）,Carboxamide ethyl-（1H-3-ethyl pyrazol-5-yl）ether（L₂）;four calix[4]crown-6 ligands with different group substitutions were synthesized:25,27-di（n-octyloxy）calix[4]arene-26,28-crown-6（L₃）,25,27-bis（8-hydroxyoctyloxy）-calix[4]arene-26,28-crown-6（L₄）,25,27-bis（n-hexyloxy）calix[4]ar-ene-26,28-crown-6（L₅）,25,27-bis（6-hydroxyoctyloxy）-calix[4]arene-26,28-crown-6（L₆）,where L₄ and L₆ were not reported in the literature;the synthesized ligands were characterized by FT-IR,TOF-MS,¹HNMR,and elemental analysis;the extraction behavior and extraction mechanism of L1 and L₂ for Ln³⁺were investigated;the extraction behavior and extraction mechanism of L₃-L₆ for Cs⁺were studied.The results showed that in the nitric acid system with 1,2-dichloroethane as diluent,L₁ and L₂ formed 1:2 type（Ln/L）extractive complexes with Ln³⁺,and the extraction reached equilibrium within 5 min.The acidity had almost no apparent effect on the extraction partition ratio.In the complexes,the O atoms of amide and ether groups,and the N atom of pyrazole group participated in the coordination with Ln³⁺.With n-octanol as the diluent,L₃-L₆ showed good extraction selectivity for Cs⁺,and the ligands and Cs⁺formed a 1:1 type of extractive complexes,respectively.At low acidity,Cs⁺distribution ratios by L₃-L₆ were small,which could be used as a back-extraction condition.The introduction of hydroxyl groups on the alkyl chain terminal improved the extraction distribution ratios of the ligands.The results of this thesis provide a new reference system for the exploreation of ligands for Ln³⁺/An³⁺separation,a new ligand option for the selective extraction of cesium from strongly acidic conditions,and an important reference for further optimization of calix[4]crown-6 extractant structures in the context of radioactive cesium separation from liquid HLW.