Extraction Of Several Rare-Earth Metal Ions Using IsoBu-BTP/[C₂mim][NTf₂] System

With the tremendous development of nuclear power, how to deal withspent fuel has attracted lots of attention. However, one of the problemsduring the spent fuel reprocessing is the separation of Minor Actinide fromHigh Level Liquid Waste, especially the separation of An (III) and Ln (III),which have similar chemical properties. In current researches, the newnitrogen donor ligands--R-BTP (bis-triazine-pyrdine) have beensynthesized and tested as the extracting agents with potential selectivity foractinides (III) over lanthanides (III). It is the first time that the extractionbehavior of rare-earth metals ions from nitric acid solution was studied byusing a novel extracting system based on R-BTP and ionic liquid. Weattempt to establish a new solvent extraction system for the separation ofminor actinide and lanthanide.The extraction behavior of several rare-earth metal ions (Y (III), Nd(III), Eu (III), Dy(III)) was investigated by using a novel extracting system,which is made up of2,6-bis(5,6-dibutyl-1,2,4-triazin-3-yl) pyridine(isoBu-BTP)--acted as extractant which can separate lanthanides andminor actinides effectively in nitric acid solution, and1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][NTf2])--acted as an extraction medium which shows a great solubility againstisoBu-BTP. We study the extraction behavior of Dy (III)(simulatingactinide) and Eu (III)(simulating lanthanide) from nitric acid solution byusing the R-BTP/IL system, to simulate An/Ln separation in spent fuelrecycles. This research could be divided into3parts.Part A. The influence of the concentration of nitric acid, the concentration of extractant and the stripping condition have beeninvestigated in detail. It has been proved that theisoBu-BTP/[C2mim][NTf2] extracting system is favorable to extractrare-earth metals at low acidity condition (<0.1mol/L), and back-extract athigh acidity condition (>3mol/L). In addition, Dy has been found to beselectively extracted and shows great extraction kinetics in currentextracting system.Part B. The extraction mechanism for the extraction of Dy (III) hasalso been discussed. A lg-lg plot of the DDyvalues versus isoBu-BTPconcentration suggested that most Dy from aqueous phase was extractedby BTP, which can form a3:1molar complex with Dy (III); while a smallquantity of Dy was extracted by ionic liquid itself. The cation exchangeand co-extraction, which were induced from ionic liquid, functioned toextraction and resulted in such stoichiometry mentioned above.Part C. The γ-irradiation effects on several rare-earth metal ions (Y(III), Nd (III), Eu (III), Dy(III)) extraction by isoBu-BTP/[C2mim][NTf2]system and γ-irradiation stability of isoBu-BTP/[C2mim][NTf2] systemwere studied in detail. The γ–irradiation almost has no effect on theextraction of REs by isoBu-BTP/[C2mim][NTf2] system. The UV-vis(Ultraviolet-Visible) and NMR (Nuclear Magnetic Resonance) spectrumshows that the structure of isoBu-BTP remains unchanged after γ–irradiation (1000kGy). However, the result of UV-vis and color changesuggest that [C2mim][NTf2] has partly radiolysis after γ–irradiation, butnot strong. What’s more, we found precipitate when γ–irradiated[C2mim][NTf2] contact with REs solution, which proves the radiolysis of[C2mim][NTf2]. All in all, isoBu-BTP/[C2mim][NTf2] system shows adesirable γ-irradiation stability.