TBP-D2EHPA协萃体系分离盐湖卤水中锂镁

Separation of lithium and magnesium from salt lake brine by TBP-D2EHPA synergistic extraction system

针对磷酸三丁酯(TBP)-FeCl_(3)萃取体系从镁锂比高的盐湖卤水分离锂镁工艺中存在的反萃酸度高、再生有机相试剂消耗大等问题,筛选出添加二(2-乙基己基)磷酸(D2EHPA)的协萃体系。探究了有机相组成、Fe/Li摩尔比、萃取相比等因素对盐湖卤水中锂镁萃取分离效果的影响。在有机相组成为40%TBP-20%D2EHPA-40%260#溶剂油、Fe/Li摩尔比为1.5、相比O/A=2的优化萃取条件下,单级Li^(+)萃取率达78.56%,锂镁分离系数达46.26。使用水作为洗涤剂及反萃剂,优选了洗涤相比O/A=60及反萃相比O/A=20,单级洗涤及反萃阶段锂镁分离系数分别为46.26和22.97,取得了较好的锂镁分离效果,可为后续扩大试验与工业设计提供依据。

Aiming at the problems of high acidity stripping and consumption of a large amount of reagents for organic regeneration in the process of separating lithium and magnesium from salt lake brine with high magnesium-to-lithium ratio by tributyl phosphate(TBP)-FeCl_(3) extraction system,a synergistic extraction system with addition of bis(2-ethylhexyl)phosphate(D2EHPA)was screened out.The effects of organic phase composition,Fe/Li molar ratio,extraction ratio and other factors on the extraction and separation of lithium and magnesium from salt lake brine were systematically investigated.Under the optimal extraction conditions of organic phase composition of 40%TBP-20%D2EHPA-40%260#solvent oil,Fe/Li molar ratio of 1.5,and O/A=2,the single-stage Li^(+) extraction rate reached 78.56%and the lithium-magnesium separation coefficient reached 46.26.Using water as the washing and stripping agent,the washing ratio of O/A=60 and the stripping ratio of O/A=20 were preferred.A good lithium-magnesium separation effect was achieved,providing a basis for subsequent pilot experiments and industrial design.