Recovering lithium resources from salt lake brines using a novel low dissolution loss extractant of DEHEHP with FeCl3

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 FeCl3 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 Mg2+, 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 LiFeCl4·2DEHEHP.