Extraction of Lithium from Salt Lake Brine with Triisobutyl Phosphate in Ionic Liquid and Kerosene

Three ionic liquids（ILs）, namely, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-me- thylimidazolium bis[（trifluoromethyl）sulfonyl]imide and 1-ethyl-3-methylimidazolium bis[（trifluoromethyl）sul- fonyl]imide with the triisobutyl phosphate（TIBP） and kerosene system were respectively used to extract lithium ion from salt lake brine with a high concentration ratio of magnesium and lithium experimentally. Results indicate that the highest extraction selectivity for lithium was obtained with IL 1-ethyl-3-methylimidazolium bis[（trifluoromethyl）- sulfonyl]imide. The effects of solution pH and phase ratio R（O/A） on the extractive step and the influence of acid concentration of the stripping solution and R（O/A） on the back extraction step were also investigated systematically. The single-step extraction efficiency of lithium ion was 83.71% under the optimal extraction conditions, and the single-step back extraction efficiency was 85.61% with a 1.0 mol/L HCI in 1.0 mol/L NaCI medium as stripping agent at R（O/A）=2. The liquid-liquid extraction mechanism and the complex of the ligand with lithium were proposed.