Zheng Zhang,Jinfeng Zhang,Zhihua Zhang,Xiao Du,Xiaogang Hao,Xiaowei An,Guoqing Guan,Jun Li,Zhong Liu
A novel physically blended polyvinylidene fluoride (PVDF) and polyacrylic acid (PAA) composite binder enhanced LiMn 2 O 4 /C (carbon black) film based electrode was successfully fabricated, and applied in an electrochemically switched ion exchange (ESIX) process for selective extraction of Li + from high Mg/Li ratio brine. The multifunctional composite binder system enabled the obtained LiMn 2 O 4 /C/PVDF- b -PAA film coated electrode to exhibit superior mechanical, hydrophilic and electrochemical properties compared with the LiMn 2 O 4 /C/PVDF film coated electrode. Based on the density functional theory (DFT) calculations, the ion exchange interaction between H + of –COOH groups in PAA and Li + facilitated the transport of Li + at the electrode interface, which enhanced lithium extraction performance of the film coated electrode. For treating the simulated brine (Mg/Li: ∼500), the intercalation capacity of Li + was about 15.1 mg g −1 , and the total extraction efficiency of lithium reached up to 62.8% after two electrochemical intercalation tests. Moreover, the film coated electrode displayed excellent selectivity towards Li + ions even in pre-treated actual brine (Mg/Li: ∼292.2). The Mg/Li mass ratio in the recovery solution could decrease to 0.46, and the calculated Li + /Mg 2+ separation coefficient reached as high as 631.08. In particular, the highly stable and scalable electroactive film could be prepared effectively, thus increasing its applicability. It is expected that such a LiMn 2 O 4 /C/PVDF- b -PAA film coated electrode could be a promising candidate for the selective extraction of Li + from high Mg/Li mass ratio brines.
Here, we report a new liquid-membrane electrodialysis capable of selectively recovering lithium from high Mg/Li ratio brines. The liquid membrane is composed of an ionic liquid system as the Li + carrier that presents high selectivity toward Li + and long-term sustainability, and 2 solid cation-exchange membranes to sandwich the carrier. Recognition and selective electromigration of Li + can be achieved by the sandwiched liquid membrane assisted by an electric field. The Mg/Li decreases from 50:1 in the initial feeding brine to 0.5:1 in the receiving solution after electrodialysis at a current density of 4.375 A·m − 2 for 12 h. Moreover, higher current efficiency (65%) and lower specific energy consumption (16 Wh·g − 1 Li) are obtained compared to typical electrodialysis processes. From the perspective of practical application, the Mg/Li drops to 0.26:1 from 53:1 in the old brine from West Taijinair, and K + and Ca 2+ in the brine are almost completely blocked by the liquid membrane. This method displays a great perspective on the application for lithium recovery from high Mg/Li brines owing to its high selectivity, efficient energy utilization, and environmental friendliness.
Exploring a facile method to recover Li + is crucial for liquid-liquid extraction from high Mg/Li ratio brine for energy conversion and storage. A simple and effective approach herein that involves the lithium recovery from high Mg/Li ratio brine at a controlled temperature is proposed. Liquid-liquid extraction of Li + from high Mg/Li ratio brine was carried out using tributyl phosphate (TBP) diluted in temperature-responsive ionic liquid as the extraction organic phase. The introduction of this ionic liquid allows for the solid-liquid conversion of the extraction phase by adjusting the temperature, and then achieves effective phase separation after liquid-liquid extraction. The parameters such as pH value, the dosage of IL, and phase ratio were optimized by experiments to achieve more than 80% of lithium recovery from a high Mg/Li ratio solution. The loaded organic phase was regenerated by HCl stripping, and the stripped organic phase can be recovered with no crud or emulsification during the process. In this work, a novel and green method was developed for lithium selectivity recovery by using a switchable temperature-responsive TBP-IL system.
The high Mg/Li ratio in salt lake brine in China remains a challenge for the efficient separation of Mg and Li and the Li extraction. A reaction-coupled separation technology we proposed has been successfully applied to the highly efficient separation of Mg and Li from the brine. In this work, we conducted intensive investigations both experimentally and theoretically on the boundary conditions of Mg/Li separation from the brine in association with the initial Mg/Al ratio and Mg/Li ratio. We analyzed the relationship between the composition and the formation of precipitates by changing the Mg/Al molar ratio and the Mg/Li mass ratio in feedstock solution to determine the boundary conditions. The experimental results show that the Mg/Al molar ratio in the initial solution has a great influence on the separation of magnesium and lithium. It is evident that lithium enters the solid as a LiAl-layered double hydroxides (LiAl-LDHs) phase when the Mg/Al molar ratio is less than 2. It has also been found that the precipitate is independent of the Mg/Li mass ratio. From the theoretical results, it has been determined that an increase in the number of Li + clusters results in a decrease of the binding energy in the same system. Al 3+ prefers to combine with Mg 2+ to form MgAl-LDH clusters. However, when the Mg/Al ratio is lower than 2:1, Li + can form a cluster of LiAl-LDH layer. It can also be seen that different Li + numbers do not change the formation of clusters. Good agreement was found between the theoretical simulation results and the experimental data. This work provides a key criterion for the efficient separation of magnesium and lithium from the brine by a reaction-coupled separation technology.
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