The effect of ionic liquids as co-extractant with crown ether for the extraction of lithium in dichloromethane-water system

Publication date: 1 July 2019Source: Journal of Molecular Liquids, Volume 285Author(s): Wenbo Zhu, Yongzhong Jia, Quanyou Zhang, Jinhe Sun, Yan Jing, Jie LiAbstractWith different anionic and cationic structures of ionic liquids influencing the efficiency of Li+ extraction, 16 different kinds of ionic liquids with the crown ether-dichloromethane system were investigated primarily. The experimental results showed that smaller relative molecular weight, hydrophobicity, uniform electron distribution on cation, and weak electron donating on anion of ionic liquids with the ligand crown ether promoted the highest extraction of lithium ions in the dichloromethane-water system. The extraction system with [BMIm][NTf2] had the largest extraction rate and distribution coefficient at 26.35% and 0.358, respectively. Cation exchange behavior between Li+ in the aqueous phase and [BMIm]+ in the organic phase was examined through fitting the line of Li+ concentration in the organic phase and [BMIm]+ concentration in the aqueous phase. The anion of [BMIm][NTf2] coordinating with the cationic lithium-crown ether complex in the organic phase was also verified by infrared spectroscopy. For the thermodynamic studies in the system using [BMIm][NTf2] and crown ether, the extraction process of Li+ was an exothermic spontaneous reaction while lower temperature was beneficial to lithium extraction.Graphic abstract
Source: Journal of Molecular Liquids - Category: Molecular Biology Source Type: research