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/FeCl3 extraction system is effective but limited by FeCl3 hydrolysis. This study introduces iron-based task-specific ionic liquids (TSILs), such as [Emim]FeCl4, [Bmim]FeCl4, and [Hmim]FeCl4, 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]FeCl4 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 FeCl3. 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]FeCl4 maintained stable extraction performance over five cycles, demonstrating industrial viability. This study highlights the TBP-[Bmim]FeCl4 system as a robust, efficient, and hydrolysis-resistant approach for Li extraction from complex brines, offering a scalable solution for Li resource development.