Lithium is becoming one of the most eye-catching metal elements in modern industry, mainly because of its crucial role in manufacturing lithium-ion batteries. The demand for lithium in the new energy market is burgeoning significantly, while enormous lithium resources reserved in salt lakes in northwest China are not exploited effectively, due to the high Mg/Li mass ratio. Although the TBP extraction system has been applied in lithium extraction from salt lake brines, there are still some problems to be solved, such as its high solubility, easy degradation, and so on. In this work, a novel low dissolution loss extraction system was developed, with DEHEHP and FeCl 3 serving as extractant and co-extractant, respectively. A real brine from Da Qaidam Lake was used to prove its practicality and effectiveness. After studying the detailed conditions of each process, a whole countercurrent process was performed, including eight stages of extraction, two stages of scrubbing, three stages of stripping, and regeneration. It was found that 99.4% of Li + was successfully recovered from the brine, and the stripping liquor contained 22.74 g/L Li + , 0.51 g/L Mg 2+ , and 3.16 g/L B. The concentration of Li + increased approximately 20-fold while the Mg/Li mass ratio decreased by a factor of 3900, from real brine to stripping liquor. High-purity (>98.5%) lithium carbonate products were prepared from the stripping liquor by precipitation. The dissolution loss of the organic phase in the raffinate was only 22.5 ppm, much lower than published works. Finally, the mechanism of extraction and co-extraction were systematically studied and the structure of the complex formed during extraction was revealed as LiFeCl 4 ·2DEHEHP.
Recognized as a critical element, lithium underpins the advancement of renewable energy and nuclear technologies. Most lithium reserves in China are distributed in the salt lake brines of the Qinghai and Tibet regions. However, the formidable technical challenges associated with recovering lithium from salt lakes have limited their development and utilization, particularly for salt lakes with a high Mg/Li ratio. Traditional extraction systems often suffer from drawbacks, including low extraction efficiency, high water solubility, and poor economic feasibility. In this study, an innovative and efficient extraction system (DEHEHP-MIBK) was proposed for recovering lithium via countercurrent extraction from brines with a high Mg/Li ratio. The optimal parameters, including extractant concentration, Fe/Li molar ratio, brine pH, equilibrium time, and O/A phase ratio, were determined. Through 6-stage countercurrent extraction, 99.9% of lithium was extracted from the brine. Subsequently, the scrubbing and stripping conditions were investigated, yielding a stripping solution with a lithium content of 22.56 g/L and a Mg/Li ratio reduced to 0.002. The 98.9% purity lithium carbonate (Li 2 CO 3 ) products were fabricated through precipitation from the stripping liquor. The intrinsic mechanism of lithium extraction in the DEHEHP-MIBK system was probed using a slope analysis method and Fourier transform infrared (FT-IR) spectroscopy. It can be inferred from the results that the composition of the extracted compound is LiFeCl₄·DEHEHP·MIBK. Density functional theory (DFT) computations further explain the superior performance of this system in depth. This study provides an efficient method that offers novel insights into the selective recovery of lithium from high Mg/Li ratio salt lakes.
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