苯并-15-冠-5/离子液体体系液液萃取锂

以高同位素效应的苯并-15-冠-5(简写为B15C5)为萃取剂,绿色稳定的1-丁基-3-甲基咪唑双(三氟甲烷磺酰)亚胺盐(简写为[C4MIm]NTf2)离子液体为溶剂,建立了B15C5-[C4MIm]NTf2/LiA(阴离子分别为双三氟甲基磺酸亚胺根NTf-2、三氟甲磺酸根OTf~-和Cl~-)-H2O液液萃取体系以高效分离锂同位素。重点考察了体系平衡时间及冠醚浓度、锂盐浓度、温度和pH对分配比D的影响,结果表明:体系萃取平衡较快,t≤30s;提高B15C5浓度和适当降低锂盐浓度有利于分配比D的提高,同等条件下分配比大小为LiNTf2LiOTfLiCl,均远高于其他萃取体系;温度和pH对分配比无显著影响。此外,对络合物晶体的研究发现锂盐与B15C5均形成1∶1络合物[Li4(B15C5)4(OH)2(H2O)](NTf2)2,离子液体体系中Li+可能多数以阳离子交换方式萃入有机相。

Liquid-Liquid Extraction of Lithium by Benzo-15-Crown-5/Ionic Liquid System

By using high isotope effect extracting agent benzo-15-crown-5(B15C5) and green and stable solvent-ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide([C4MIm]NTf2), liquid-liquid extraction system B15C5-[C4MIm]NTf2/LiA(anions were bis(trifluoromethylsulfonyl) imide(NTf-2), trifluoromethanesulfonate(OTf-) and Cl-)-H2O was established to separate lithium isotopes efficiently.Equilibrium time, effect of concentration of B15C5 and lithium salts, temperature and pH on distribution coefficient(D) were examined.The results indicate: the extraction equilibrium are short, t≤ 30 s;increasing the concentration of B15C5 and reducing the concentration of lithium salts are conducive to improve the distribution coefficient(D).Under the same conditions, the order of the D is LiNTf2>LiOTf>LiCl, much higher than other extraction system;temperature and pH have no significant effect on the distribution coefficient.In addition, single crystal structure analysis of the complexes shows that all lithium salts are formed the same 1∶1 complex as [Li4(B15C5)4(OH)2(H2O)](NTf2)2 with B15C5, indicating that Li+ is most likely extracted into organic phase by cation exchange process in ionic liquid system.The extraction system is efficient, green and has large capacity of lithium, it may have a high application value in industrial production.