Li Cui,Kun Jiang,Junfeng Wang,Kun Dong,Xiangping Zhang,Fangqin Cheng
The solvent extraction of Li + by Cyanex 923 was investigated upon the addition of different imidazolium-based ionic liquids (ILs). The results showed 1-hydroxylethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HOEmim][NTf 2 ]) can improve the extraction of Li + most effectively. The fundamental mechanism is that [HOEmim][NTf 2 ] can remarkably enhance the coordination ability of Cyanex 923 to Li + to form more stable and hydrophobic ion-pair species [Li(Cyanex 923) n ][NTf 2 ] ( n max = 3) resulting from the electrostatic interaction and typical hydrogen bonding of IL, and thus facilitating the transfer of Li + into organic phase. This work has revealed the transfer mechanism of Li + in a solvent extraction system comprising of IL and neural ligand. The knowledge of the coordination environment of Li + in the presence of IL also gives us a new insight into the separation of 6 Li/ 7 Li. The disadvantage of this process is the loss of IL. However, this study provides guidance for the design of better IL-based systems for the separation of metal ions.
Du Jinjing,Wang Dongbo,Ma Jiayi,Zhai Ruitong,Lin Haiyang,Wang Bin,Li Qian,He Xihong,Zuo Heng
This study investigated the extraction performance of the DBM (bibenzoylmethane) + Cyanex 923 system, proposing a novel method for the selective recovery of lithium from lithium sulfate solutions. Density functional theory (DFT) calculations were employed to elucidate the synergistic extraction mechanism. The results demonstrated that the DBM + Cyanex923 synergistic system effectively achieved lithium–sodium separation, with the organic phase composition and equilibrium pH significantly influencing the separation efficiency. Under optimized conditions (organic phase: 0.5 mol/L DBM + 1 mol/L Cyanex923; aqueous phase: 2 g/L Li, 50 g/L Na; pH 12; 25°C; phase ratio O/A = 1:1), a single-stage lithium extraction rate of 92.1% was achieved. For the simulated feed solutions containing 2 g/L Li and 50 g/L Na, a two-stage countercurrent extraction process at O/A = 1:2 yielded more than 99% lithium extraction. Using 0.5 mol/L H 2 SO 4 as the washing solution at O/A = 2:1 through two-stage countercurrent extraction, the sodium concentration in the loaded organic phase was reduced to less than 0.05 g/L, with a washing efficiency exceeding 97.8%. Three-stage countercurrent stripping with 1.5 mol/L H 2 SO 4 at O/A = 3:1 produced stripping solutions containing 17.12 g/L Li and 1.02 g/L Na, resulting in sodium impurity removal rates above 98%.
Junya Cao,Zhen Meng,Jianfeng Zhang,Qiyu Meng,Meng Wei,Li Wang,Huiyong Wu,Marco Wenzel,Jan J. Weigand,Huizhou Liu,Liangrong Yang
Direct and efficient recovery of lithium from precipitation mother liquor has garnered increasing attention, but challenges remain due to the low concentration of Li+ and high Na+ excess. To address these issues, we proposed a synergistic extraction system using 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HPMBP) as the extractant and Cyanex 923 as the synergist, which exhibits high selectivity for lithium in industrial mother liquors. In a single-stage extraction, HPMBP-Cyanex 923 achieved 85% Li+ extraction with only 4% Na+ and K+ from a real mother liquor solution containing 1.46 g/L Li+, 67 g/L Na+ and 2.57 g/L K+. The total organic carbon (TOC) test showed that HPMBP-Cyanex 923 exhibited significantly lower dissolution loss (220 mg/L) compared to that of the commonly used benzoyl-1,1,1-trifluoroacetone (HBTA, 432 mg/L), indicating superior hydrophobicity, which is essential for a green extraction process. The results demonstrate that 97% Na+ in the organic phase can be scrubbed prior to Li+ stripping, and much lower acid concentration (0.2 M HCl) is required to strip the lithium due to a lower pKa value of pyrazolone compared to traditional β-diketones. Single-crystal analysis, slope analysis, and DFT calculations revealed the observation of a binuclear structure, [Li2(PMBP)2(TBPO)2], which could serve as a general structural formula for systems involving pyrazolones and an organophosphorus co-ligand with a short alkyl chain. This work presents a novel lithium extraction system that offers enhanced selectivity and hydrophobicity, along with a lower stripping acid requirement compared to traditional β-diketones. These features make it highly promising for future industrial applications.
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