Study On Radiation Chemistry Of Typical Lanthanides/Actinides Extractants In Imidazole Ionic Liquid

Room temperature ionic liquids(RTILs)have been widely studied for their potential application in the reprocessing of spent nuclear fuel,due to a number of unique properties,such as nonvolatility,good solubility,and radiation stability.The extraction efficiency of the novel extraction system using traditional extractants Octylphenyl-(N,N-(diisobutyl)carbamoyl-methyl)phosphine oxide(CMPO)/ N,N,N‘,N‘-tetraoctyldiglycolamide(TODGA)or 2,6-bis(1,2,4-triazin-3-yl)pyridines(BTPs)dissolving RTILs were obviously enhanced.In light of the reason that extractants would inevitably be exposed to strong radiation due to the long-lived radionuclides,the radiation effect on the extractability of novel extraction system should be evaluated carefully before its practical applications in SNF reprocessing.It was widely acknowledged that the trace amount and variety of the radiolytic products was the difficult point of radiolysis study.Meanwhile,RTIL-based extraction systems improved the difficulty due to the challenge in clearly separating extractant,ionic liquid and their radiolytic products.At present,a lot of these studies merely focused on pure solvent or extractant,which can not explain the radiolysis mechanism of the system containing extractant and solvent.In this work,the radiolysis study of extraction system consisted of extractant and RTIL was performed firstly.The method for radiolysis study was firstly established using ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry(UPLC/Q-TOF-MS)and matrix assisted laser desorption ionization/Fourier transform mass spectrometry(MALDI-FTMS).In addition,the density functional theory(DFT)calculations of extractability for the first time.Moreover,three novel extractants(CA-BTP?CA-BTBP?CA-BTPhen)were synthesized and the radiation-stability was studied preliminarily.Quantitative analysis of CMPO,TODGA,2,6-bis(5,6-dibutyl-1,2,4-triazin-3-yl)pyridine(isobutyl-BTP)in RTIL was performed using UPLC/Q-TOF-MS firstly,and the radiation stability of extractants in RTIL was discussed.Identification of radiolytic priducts was performed using MALDI-FTMS ? UPLC-ESI-MS/MS,and the result indicated that the radicals(such as ·[C2mim]?·CF3)generated from RTIL would attack the extractant and formed the radiolytic priducts.To furtherly understand the radiolysis behaviour of extractant in RTIL,semi-quantitative analysis of radiolytic products was performed.The results indicated that the extractant in molecular solvent prefered degradation,and it become reaction between extractant and radicals when that in RTIL.More over,radiolytic products would furtherly radiolysis with radiation.As for the influence of radiation on extractability,we found that CMPO/[C2mim][NTf2] or TODGA/[C2mim][NTf2] still reached extraction rate more than 99% under 0.01 M HNO3 even at 800 k Gy.The DFT caculations presented that the TODGA-[C2mim]+ simulated compound(TMDGA-C2mim)+ kept patial extractability.Three novel extractants(CA-BTP?CA-BTBP?CA-BTPhen)were synthesized.The radiolysis study of pure extractant indicated that the radiolysis behaviour were not observed under 1000 k Gy using FTIR and 1H NMR.The extraction order under 0.01 M HNO3 were CA-BTPhen> CA-BTBP> CA-BTP>isobutyl-BTP.The extraction of CA series extractant under high HNO3 consentration was inhibited and the extraction system for high nitric acid need to be explored furtherly.At last chapter,the main conclusions and innovations of this thesis were resented.Finally,the prospect in future work was speculated.