Recovering of Li⁺ from the mother liquor obtained during the process of Li₂CO₃ production has been considered as a promising solution to the shortage of lithium resources. However, as the mother liquor is a complex saline system with high concentration of Li⁺ (1.42 g/L) and a large amount of Na⁺ (55.62 g/L), there is no competent method to carry out for the effective utilization of Li⁺. This work reports a class of hydrophobic deep eutectic solvents (HDESs) formed by tetrabutylammonium chloride (TBAC) and oleic acid (OA), which is a novel co-extraction reagent for Li⁺ extraction. In addition, tributyl phosphate (TBP) is used as extractant and ammonia is applied to regulate pH. TBAC/3OA showed the highest extraction efficiency in single extraction (76.8%) with the ammonia concentration, the volume ratio of organic phase and aqueous phase (O/A phase ratio), and volume fraction of HDES as 1.5 mol/L, 1, and 30%, respectively. Mechanism studies through the UV-vis and FT-IR proved that cation exchange between Li⁺ and HDES, and Li⁺ coordination was the dominant force in the separation process. The complexing ability of P=O in TBP led to the selective extraction of Li⁺. The reusability experiments of organic phase demonstrated that the extraction efficiency was still above 60% after five cycles, indicating the favorable stability of the extraction system. Finally, the separation factor (β_Li/Na) of Li/Na in the mother liquor was 20.5, indicating that the TBP-HDES system has the capability to selectively extract Li⁺ with high Na/Li ratio. This will help to design possible green HDES for lithium recovery.

从生产Li ₂ CO ₃的过程中获得的母液中回收Li ⁺被认为是解决锂资源短缺的一种有前途的解决方案。但是，由于母液是复杂的盐水系统，具有高浓度的Li ⁺（1.42 g / L）和大量的Na ⁺（55.62 g / L），因此没有有效的方法可以有效利用李⁺。这项工作报告了一类由氯化四丁铵（TBAC）和油酸（OA）形成的疏水性深共晶溶剂（HDES），这是一种新型的Li ⁺共萃取试剂萃取。另外，磷酸三丁酯（TBP）用作萃取剂，氨水用于调节pH。TBAC / 3OA的单次萃取效率最高（76.8％），其氨浓度，有机相与水相的体积比（O / A相之比）和HDES的体积分数为1.5 mol / L，1，和30％。通过UV-vis和FT-IR的机理研究证明，Li ⁺和HDES之间的阳离子交换以及Li ⁺配位是分离过程中的主导力量。TBP中P = O的络合能力导致对Li ⁺的选择性萃取。有机相的可重复使用性实验表明，经过五个循环，萃取效率仍高于60％，表明萃取系统具有良好的稳定性。最后，分离系数（β_锂/钠在母液中的Li /钠）为20.5，这表明TBP-HDES系统有能力选择性地提取锂⁺具有高的Na /李比。这将有助于设计用于锂回收的可能的绿色HDES。