Recovering lithium resources from salt lake brine utilizing a novel extraction system DEHEHP-MIBK

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.