Recovery of lithium from alkaline brine by solvent extraction with functionalized ionic liquid

Lithium recovery from alkaline brine was carried out by solvent extraction (SX) using a hydroxyl-functionalized ionic liquid, 1-hydroxyethyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide ([OHEMIM][NTf2]) and a neutral ligand, trialkyl phosphine oxide (Cyanex923) as the extractants. Effect of extraction parameters, i.e. concentration of ionic liquid, extraction time, pH value of aqueous phase, phase ratio and mole ratio of sodium to lithium, on lithium extraction efficiency have been studied. Under the optimal parameters, over 93% of lithium was extracted in one single run. The extraction mechanism of lithium was investigated by the combination method of experiment and UV-visible spectroscopic characterization, and it was found that the ion exchange predominated during the extraction process. The extraction complex was determined by a slope analysis method, indicating that Cyanex923, Li+ and [NTf2](-) formed a 2:1:1 complex. The thermodynamic study indicated that lithium extraction reaction was spontaneous. Based on the above results, [OHEMIM][NTf2]-Cyanex923 extraction system showed a promising application in the recovery of lithium from alkaline brine. (C) 2019 Elsevier B.V. All rights reserved