Research On The Extraction Of Sr²⁺ From Acid Nitrate Media With DCH18C6

The reprocessing of depleted fuel becomes a hot issue with the development of nuclear industry. 90Sr , 137Cs are the main radionuclides in high level liquid waste ?HLLW? which have been dealt with by the spent fuel reprocessing process. 90Sr ?Ti/2=28.5? has the characteristics of high radioactivity and strong heat release, and it is beneficial to deal with radioactive waste after removing strontium from HLLW. In this paper,solvent extraction method has been adopted, and dicyclohexano 18 crown 6 ?DCH18C6? dissolved in different diluents was used to extract Sr²⁺ from aqueous phase.Extracting Sr²⁺ using DCH18C6 in mixture of 1-octanol and tetrachloroethane, ionic liquid CnmimNTf2?n=2,4,6? and C4mimPF6 has been investigated. The affecting factors,such as equilibrium time, HNO3 concentration, extractant concentration, initial concentration of Sr²⁺ and temperature, et al were studied systematically. Additionally, experiments on the separation of Sr²⁺ from the simulated HLLW were carried out using the selected mixture diluent extracted system and ionic liquid extracted systems.Based on these experimental results, the process of extracting Sr²⁺ from aqueous phase with DCH18C6 in these different diluents reached dynamic equilibrium quickly. For the studied traditional solvents,encouraging results were observed that lower acidity of DSr?max?,less heat release, higher extraction and stripping efficiency of Sr²⁺ were obtained with mixture diluents as compared to pure 1-octanol used as the diluent. In addition, considerable Dsr values could be obtained when DCH18C6-70% 1-octanol + 30% acetylene tetrachloride was selected to remove Sr²⁺ from the simulated HLLW. On the other side, the extraction efficiency of Sr²⁺ in these ionic liquids extracted systems ranked as follows: EC2mimNTf2>EC4mimNPF6>EC6mimNTf2 in identical conditions. During the process of extraction,HNO3 had a great influence on the extraction of Sr²⁺ with these ionic liquid extracted systems,and the Esr decreased with HNO3 concentration increasing quickly. Moreover, the rising temperature also reduced the extraction efficiency of Sr²⁺ from aqueous phase,while C2mimNTf2 and C4mimNTf2 extracted systems showed better extraction of stability compared with the other two systems. As for the factor of initial Sr²⁺ concentration, the observed results suggested considerable Esr values even for aqueous phase containing higher Sr²⁺ concentration when 0.01M DCH18C6 was in the selected ionic liquids. Finally, ESr was determined for the extraction of Sr²⁺ from the simulated HLLW using DCH18C6 in these four ionic liquids,and it could be concluded that DCH18C6-CnmimNTf2, C4mimPF6 systems had poor selectivity for Sr²⁺ from the simulated HLLW due to the competition from some cations such as K+,Cs+, et al.