Lithium Selective Extraction from Zabuye Lake Brine by Task-Specific Ionic Liquids

Lithium (Li) is a critical resource for energy storage, yet its selective extraction from high Mg/Li ratio salt-lake brines presents significant challenges. The conventional TBP/FeCl 3 extraction system is effective but limited by FeCl 3 hydrolysis. This study introduces iron-based task-specific ionic liquids (TSILs), such as [Emim]FeCl 4, [Bmim]FeCl 4, and [Hmim]FeCl 4, as coextractants to improve Li recovery from brines with high Mg/Li ratios. Optimization of extraction conditions ( A/O ratio, pH, TSIL dosage, and time) yielded a high efficiency of 86.1% at A/O = 0.5, pH = 7.2, and 10% TSIL volume fraction. Moreover, [Bmim]FeCl 4 demonstrated the highest extraction performance, achieving Li recovery rates of 72.7 and 65.7% from the sinking lithium mother liquor and Zabuye Lake brine, respectively. The TSILs enhanced extraction stability and mitigated hydrolysis, outperforming FeCl 3 . FTIR, UV–vis, and Raman spectroscopy confirmed TSIL stability and revealed that lithium extraction proceeds through cation exchange between [Bmim] + and Li + . Thermodynamic analysis indicated an exothermic and spontaneous process. Additionally, [Bmim]FeCl 4 maintained stable extraction performance over five cycles, demonstrating industrial viability. This study highlights the TBP-[Bmim]FeCl 4 system as a robust, efficient, and hydrolysis-resistant approach for Li extraction from complex brines, offering a scalable solution for Li resource development.