Solvent extraction of lithium from aqueous solution using non-fluorinated functionalized ionic liquids as extraction agents

• Published in: Separation and purification technology 2017-01, Vol.172, p.473-479
• Main Authors: Shi, Chenglong, Jing, Yan, Xiao, Jiang, Wang, Xingquan, Yao, Ying, Jia, Yongzhong
• Format: Article
• Language: English
• Subjects: Aqueous solutions; Fourier transforms; Infrared spectroscopy; Ionic liquids; Lithium; Lithium ions; NMR spectroscopy; Solvent extraction; Stripping
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2016.08.034

The functionalized ionic liquid extractant diluted in methylbenzene is a much better solvent extraction system than the corresponding acidic extractant diluted in methylbenzene. [Display omitted] •Two novel functionalized ionic liquids were successfully synthesized and used for lithium extraction.•Mechanistic pathway was different as compared to imidazolium ionic liquid diluents.•Nature of extracted species was found out to be 1:1.•Ionic liquid systems were reusable. Two non-fluorinated ionic liquids (ILs), namely tetrabutylammonium bis(2-ethylhexyl)-phosphate, [N4444][DEHP], and tetraoctylammonium bis(2-ethylhexyl)-phosphate, [N8888][DEHP], were synthesized and fully characterized by 1H and 13C NMR spectroscopy. These functionalized ILs were subsequently evaluated in terms of their ability to extract lithium ions from aqueous solution. The extraction efficiencies of these functionalized ILs for lithium ions were measured as a function of various extraction parameters, including aqueous acidity, temperature and extractant concentration. The extracted species were determined using a slope analysis method, which indicated that the ILs formed a 1:1 (metal:ligand) complex. Fourier transform infrared spectroscopy studies were conducted to better understand the nature of the extracted species. We also investigated the stripping of the lithium ions from the organic phase and the re-use of the ionic liquid in a subsequent extraction step.