The high similarity in chemical properties between Li⁺ and Mg²⁺ poses a substantial challenge for their selective separation from salt lake brine with high Mg-Li (m/m) ratios. Herein, a highly efficient solvent extraction system was reported for Li⁺/Mg²⁺ selective separation, with tributyl phosphate (TBP) and di(aminobenzo)-14-crown-4 (CE) as extractants, [C₄mim][NTf₂] (IL) as co-extractant, and methylene chloride as a diluent. Simulated brines included 0.01 M LiCl and 0.01 and 0.2 M MgCl₂ with Mg/Li mass ratios of 3.5 and 70, respectively. Molecular dynamics (MD), density functional theory (DFT), and ¹H NMR analysis were employed to reveal the hydrogen bond interaction and compatibility between CE, TBP, and IL. Under the optimal extraction conditions containing a concentration of 20 mg/mL CE and 0.61 mmol/mL IL, the maximum single-stage Li⁺ extraction rate of the TBP-CE-IL extraction system with Mg/Li mass ratios of 3.5 and 70 were 89.5 and 81.8 %, and the separation factor of Li to Mg were up to 515 and 422. Compared with the TBP-IL extraction system, the addition of CE effectively improved the extraction rate of Li⁺ and the selectivity of Mg-Li, which was due to the hydrogen bond interaction between CE and TBP/IL and the cavity size effect between CE and Li⁺, improving CE coordination and endowing the complex generated in the organic phase with greater stability. The possible structure of the complex in the organic phase was determined to be 2TBP·Li·NTf₂-CE·Li·NTf₂ through Li⁺ extraction dynamic analysis. In summary, this work provides an efficient separation technology for Li⁺ extraction from salt lake brine.

^{Li +}和Mg ²⁺化学性质高度相似，这对从高Mg-Li (m/m)比盐湖卤水中选择性分离它们提出了重大挑战。在此，报道了一种用于Li ⁺ /Mg ²⁺选择性分离的高效溶剂萃取系统，以磷酸三丁酯（TBP）和二（氨基苯并）-14-crown-4（CE）作为萃取剂，[C ₄ mim][NTf ₂ ](IL)作为共萃取剂，二氯甲烷作为稀释剂。模拟盐水包括0.01 M LiCl 以及0.01 和0.2 M MgCl ₂，Mg/Li 质量比分别为3.5 和70。采用分子动力学 (MD)、密度泛函理论 (DFT) 和¹ H NMR 分析揭示了CE、TBP 和 IL 之间的氢键相互作用和相容性。在20 mg/mL CE和0.61 mmol/mL IL的最佳萃取条件下， Mg/Li质量比为3.5和70的TBP-CE-IL萃取体系的单级Li ⁺萃取率最大为89.5%和81.8%，Li与Mg的分离因子分别达到515和422。与TBP-IL萃取体系相比，CE的加入有效提高了Li ⁺的萃取率和Mg-Li的选择性，由于CE与TBP/IL之间的氢键相互作用以及CE与Li ⁺之间的空腔尺寸效应，改善了CE配位并使有机相中生成的络合物具有更大的稳定性。通过Li ⁺萃取动力学分析，确定有机相中配合物的可能结构为2TBP·Li·NTf ₂ -CE·Li·NTf ₂。综上所述，本工作为盐湖卤水提取Li ^{+提供了一种高效的分离技术。}