Study On The Separation Of Re/Tc By Functionalized Ionic Liquids And Their Impregnated Resins

long-lived radionuclide ⁹⁹Tc is produced during the process of the nuclear fuel cycle.The separation of Tc O₄^-from strongly acidic and highly salty high-level liquid waste（HLLW）is difficult,but of great significance.The extraction performances of conventional anion exchangers are unsatisfactory due to the lack of functional groups that are able to strongly interact with Tc O₄^-.Imidazole and amide functional groups have strong affinity for Tc O₄^-.In this thesis,a series of new functionalized amideimidazolium type ionic liquids and their impregnated resins were prepared based on the structural designability of imidazole ionic liquids,and their behaviors of selective separation of Re（VII）/Tc（VII）from different solutions were investigated.The research work of this thesis is mainly divided into two parts:1.A series of ionic liquids were designed and synthesized by adjusting the length and straight chain and branching of carbon chains,and designing the combination scheme of single or double amide functional groups.Their performance in liquid-liquid extraction for Tc O₄^-/Re O₄^-in aqueous solution under neutral conditions was tested.After screening,the functionalized ionic liquid of imidazolium containing branched diamides was found to have the best extraction performance.It also systematically tested its extraction performance under acidic,neutral and alkaline solution,and evaluated the performance of Tc O₄^-/Re O₄^-in simulated alkaline low-level radioactive waste liquid（LLRW）and 1M/3M nitric acid high level radioactive waste liquid（HLRW）.All extraction processes reached equilibrium within2 min,and 0.5 mol/L of MIMDIDOA organic phase could extract 96.5%of Tc O₄^-from the simulated 3M HNO₃HLLW;The effects of the presence of multiple coexisting anions varies differently,and the partition of different anions in the organic phase conforms with the Hofmeister order;ESI-MS,XPS,FT-IR and EDS techniques were used to study the extraction mechanism,it was anion exchange;In the range of p H 2-13,the performance of amide imidazolium ion liquid extraction Re O₄^-is ZMJ-1<ZMJ-2<MIMDIDOA,which indicates that the amide group plays an important role in the extraction of Re O₄^-,and the side-branch alkyl chain is beneficial to improve the adsorption capacity of the material.Combined DFT calculation further explains the interaction between MIMDIDOA and Re O₄^-/Tc O₄^-:in addition to electrostatic interactions,there are p-πand p-p interaction,which is a key factor for its excellent extraction performance and selectivity.Tc in the organic phase can be stripped with high hydrochloric acid and nitric acid,and the ionic liquid can be regenerated.After three cycles of extraction and stripping with 6M HNO₃,the ionic liquid still maintains an extraction rate of more than 92.5%.2.Tree diamide-imidazole ionic liquids were impregnated into Amberchrom CG71 or diatomaceous earth macroporous resins to make four kinds resins,namely MAPE-1,MAPE-2,MAPE-3 and MAGD-1.At p H～7,they have the best adsorption efficiency of Re/Tc,MAPE-1 resin can reach equilibrium within 20minutes,the adsorption capacity of Re O₄^-is 202mg/g,MAGD-1 resin can reach equilibrium within 90 minutes,Re O₄^-adsorption capacity is 149mg/g,and MAPE-2and MAPE-3 can reach equilibrium within 60 minutes,the adsorption capacity of175mg/g and 164mg/g,respectively.The removal rates of 0.1g MAPE-1 or MAGD-1for Re O₄^-in simulated denitration HLLW could reach 95%and 92.3%.The adsorption process was studied by ESI-MS,XPS,FT-IR,and SEM techniques and the mechanism was anion exchange.In addition,compared with the adsorption results of these four resins,it was found that the branched chains of the amide group for the same carbon number of double amide-imidazolium ionic liquids are conducive to the adsorption of Re O₄^-/Tc O₄^-the adsorption of Re O₄^-/Tc O₄^-;the longer the carbon chain of the amide group for the same type of ionic liquids,the more unfavorable the separation of Re O₄^-/Tc O₄^-.The functional ionic liquids show the selective separation performance of Tc O₄^-/Re O₄^-both as extractant and impregnated resins,which lay foundations for the application of spent fuel reprocessing.