在同位素技术方面,必须能够生产具有丰富同位素丰度的材料(即,用2H标记的化合物同位素,13C,6Li,18O或37Cl),这与自然丰度不同。同位素标记的化合物可用于研究不同的自然过程(例如用2H标记的化合物,13C,或18O),或者它们可以用于产生其他同位素,如6Li的情况,可以用来生产3H,或产生LiH,其作用类似于对快中子的保护罩。同时,7Li同位素可用作核反应堆中的pH控制器。COLEX进程,这是目前唯一可用于工业规模生产6Li的技术,由于汞废物和蒸气的产生,具有环境缺陷。因此,需要新的环保技术来分离6Li。用冠醚在两个液相中的化学萃取方法对6Li/7Li的分离系数与COLEX方法相当,但缺点是Li的分配系数低,萃取过程中会损失冠醚。通过6Li和7Li之间的迁移率差异电化学分离锂同位素是锂同位素分离的绿色和有前途的替代方案之一,但是这种方法需要复杂的实验设置和优化。置换色谱法,如不同实验配置中的离子交换,也已用于富集6Li,结果有希望。除了分离方法,还需要开发新的分析方法(ICP-MS,MC-ICP-MS,TIMS)用于富集时可靠地确定Li同位素比。考虑到上述所有事实,本文将通过介绍所有的化学分离和光谱分析方法,试图强调锂同位素分离技术的当前趋势,并突出它们的优点和缺点。
In terms of isotopic technologies, it is essential to be able to produce materials with an enriched isotopic abundance (i.e., a compound isotopic labelled with 2H, 13C, 6Li, 18O or 37Cl), which is one that differs from natural abundance. The isotopic-labelled compounds can be used to study different natural processes (like compounds labelled with 2H, 13C, or 18O), or they can be used to produce other isotopes as in the case of 6Li, which can be used to produce 3H, or to produce LiH that acts like a protection shield against fast neutrons. At the same time, 7Li isotope can be used as a pH controller in nuclear reactors. The COLEX process, which is currently the only technology available to produce 6Li at industrial scale, has environmental drawbacks due to generation of Hg waste and vapours. Therefore, there is a need for new eco-friendly technologies for separation of 6Li. The separation factor of 6Li/7Li with chemical extraction methods in two liquid phases using crown ethers is comparable to that of COLEX method, but has the disadvantages of low distribution coefficient of Li and the loss of crown ethers during the extraction. Electrochemical separation of lithium isotopes through the difference in migration rates between 6Li and 7Li is one of the green and promising alternatives for the separation of lithium isotopes, but this methodology requires complicated experimental setup and optimisation. Displacement chromatography methods like ion exchange in different experimental configurations have been also applied to enrich 6Li with promising results. Besides separation methods, there is also a need for development of new analysis methods (ICP-MS, MC-ICP-MS, TIMS) for reliable determination of Li isotope ratios upon enrichment. Considering all the above-mentioned facts, this paper will try to emphasize the current trends in separation techniques of lithium isotopes by exposing all the chemical separation and spectrometric analysis methods, and highlighting their advantages and disadvantages.