Study On The New Systems Of Lithium Isotopes Extraction Separation

Lithium is composed of two stable isotopes6Li and7Li. Each lithium isotope hasimportant application in nuclear energy source and nuclear industry. Lithium isotopesseparation is quite challenging due to6Li and7Li similiar chemical and physical property.Lithium amalgam method applies to industrial separation lithium isotopes and causes seriousenvironmental problems. Study a new lithium isotopes separation system is of greatsignificance. The new lithium isotopes extraction systems were designed in this article.Specific research contents involved in the following aspects:1、Study on the new system of liquid-liquid extraction separation of lithium isotopes.(1)The effects of four kinds of aliphatic ether extraction agent, including glyme, diglycol,triglyme, tetraglyme for separating lithium isotopes were investigated. The extractionparameters such as the anion of lithium salt, the concentration of lithium ion and extractionagent, extraction time were optimized. The effect of back-extraction agent and the mechanismof extraction system were discussed. The maximum single-stage separation coefficient oflithium isotope of aliphatic ether extraction system is1.006±0.002. The lighter isotope6Liwas enriched in the organic phase while the heavier isotope7Li was concentrated in theaqueous phase.(2) The effects of binaphthol and7-(4-ethyl-1-methyloctyl)8-hydroxyquinoline as extraction agent separation of lithium isotopeseparation system were examined. The effects of extraction agent concentration, synergeticagent concentration, sodium hydroxide concentration on the lithium isotopes separationsystem were investigated. The mechanism of extraction system was discussed. The maximumsingle-stage lithium isotope separation of binaphthol extraction system is1.007±0.002. Thelighter isotope6Li was enriched in the organic phase. The maximum single-stage lithiumisotope separation coefficient of7-(4-ethyl-1-methyloctyl)8-hydroxyquinoline extractionsystem is1.003±0.002.7Li was enriched in the organic phase.2、Study on sol-gel materials doped with ionic liquids and benzo15-crown-5solid-liquid extraction separation of lithium isotopes. Three kinds of imidazolium based ionicliquids ([C8mim][BF4],[C8mim][PF6],[C8mim][(CF3SO2)2N]) and benzo15-crown-5hadbeen prepared and characterized. New mesoporous silica materials IL15SGs (HF15SG,TF15SG and DF15SG) doped with benzo-15-crown-5(B15) and imidazolium based ionicliquids ([C8mim][BF4]、[C8mim][PF6]or [C8mim][(CF3SO2)2N]) have been prepared whichapplied to lithium isotopes separation for the first time. The parameters of solid-liquidextraction system such as the concentration of lithium salts, initial pH, extraction time andcounter anion of lithium salt on the lithium isotopes separation were examined. The study ofthermodynamic parameters of system indicated that three kinds of mesoporous silicamaterials extraction lithium isotope systems are exothermic reaction and forward reaction is aspontaneous process and the chaos of system decrease. X-ray crystal structure analysisindicated that the lithium salt was extracted into the solid phase with crown ether forming[(Li0.5)2(B15)2(H2O)]+complexes. The solid-liquid extraction maximum single-stage isotopesseparation factor of6Li-7Li was up to1.0460.002. The heavier isotope7Li was concentrated in the solution phase while the lighter isotope6Li was enriched in the gel phase. IL15SGswere also easily regenerated and reused in the consecutive removal of lithium ion.3、Study on ionic liquid impregnated resin (IR) extraction lithium isotopes. XAD-7resin acted as carrier which doped with benzo-15-crown-5(B15) and imidazolium based ionicliquids ([C8mim][BF4]、[C8mim][PF6] or [C8mim][(CF3SO2)2N]) for lithium isotopesseparation for the first time. The effects of lithium anion, initial pH of aqueous phase,extraction time on extraction separation of lithium isotope were investigated. The mechanismof extraction system was studied. The thermodynamic parameters of the system were obtainedby studying the influence of different temperature on the extraction separation of lithiumisotopes. The maximum adsorption quantity of different ionic liquid impregnation of resinmaterials for lithium isotopes was measured. The lighter isotope6Li was enriched in the gelphase. The solid-liquid extraction maximum single-stage isotopes separation factor was up to1.0460.002. The reuse of the impregnated resin extraction system indicated that theimpregnated resin can regenerated easily. The parameters of mesoporous silica materials andionic liquid impregnated resin extraction system are compared.