Recovery of Lithium Ions from Salt Lake Brine with a High Magnesium/Lithium Ratio Using Heteropolyacid Ionic Liquid

A fluoride-free ionic liquid 1-butyl-3-methylimidazolium phosphotungstate ([Bmim]3PW12O40) was synthesized and first used as co-extraction reagent for recovery of lithium ions from salt lake brine with a high Mg/Li ratio. Fourier transform infrared spectra (FT-IR), nuclear magnetic resonance (NMR) and thermogravimetric analysis (TGA) were used for characterizations of the prepared ionic liquid. Tributyl phosphate (TBP), [Bmim]3PW12O40, and dimethyl phthalate (DMP) were used as extractant, co-extraction reagent, and diluent, respectively. Effects of molar ratio of [Bmim]3PW12O40 to Li+, O/A phase ratio, volume fraction of TBP,and carbon chain length of ionic liquid on extraction efficiency and separation factor of Li+ were investigated. The overall extraction efficiency of Li+ was 99.23% after five stages cross-current extraction experiments under optimal conditions. The washing and stripping experiments of the organic phase were conducted, and the parameters were optimized. The reusability of the organic ...