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

Abstract

A fluoride-free ionic liquid 1-butyl-3-methylimidazolium phosphotungstate ([Bmim] 3 PW 12 O 40 ) 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] 3 PW 12 O 40 , and dimethyl phthalate (DMP) were used as extractant, co-extraction reagent, and diluent, respectively. Effects of molar ratio of [Bmim] 3 PW 12 O 40 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 phase was investigated. A total of 10 regeneration cycles of extraction processes showed that the organic phase was highly stable for selective extraction of Li + . Finally, the extraction mechanism using the proposed extraction system was also explored. The results showed that the highly selective extraction of lithium ion was realized by cation exchange and coordination between TBP and Li + .

Combining Selective Extraction and Easy Stripping of Lithium Using a Ternary Synergistic Solvent Extraction System through Regulation of Fe3+ Coordination

“…In such extraction, the cations of the ionic liquids enter into the aqueous solution and the anions are involved in the complex formation with Li + . [19][20] Following this discovery, many kinds of ionic liquids [21][22] and salts (e.g. NaClO4 and NaB(Phen)4) with symmetric anions were found to be similar in extraction capability of lithium with TBP.…”

A Nano‐Heterogeneous Membrane for Efficient Separation of Lithium from High Magnesium/Lithium Ratio Brine

“…To this end, molecular design of task‐specific monomers for surface modification is crucial. Recently, ionic liquids show high efficiency in liquid extraction, ion sieving, and gas separation, [ 31–34 ] yet ionic liquid membranes have not been reported for high performance lithium separation from salt lake brines. In particular, previous ionic liquid monomers contain only one reactive group that limits the in‐depth modification and structure modulation.…”

Opposite selectivities of tri‐n‐butyl phosphate and Cyanex 923 in solvent extraction of lithium and magnesium

“…In the synergic solvent extraction of Li by the TBP/FeCl 3 system, the role of FeCl 3 is to form an anionic [FeCl 4 ] − complex that can further form an ion pair with the cation [Li(TBP) x ] + ( x = 1, 2), as shown in Equation (). In recent years it was found that anions of ionic liquids (ILs), such as [PF 6 ] − , [NTf 2 ] − , [B(Phen) 4 ] − and [PW 12 O 40 ] 3− can replace [FeCl 4 ] − as counter anions, provided that the cations of the ILs are hydrophilic 21‐25 . Therefore TBP can also synergically extract Li from Mg‐containing solutions in combination with ILs, although the use of ILs instead of FeCl 3 is not economic because of the high cost of ILs and the difficulty of recycling the ILs. where x = 1, 2, and the overbar means that the compound resides in the organic phase.…”