High-Efficiency Lithium Extraction From Lithium Precipitated Mother Liquor Using the IPE-Z Lithium Extractant Under Weakly Alkaline Conditions

As a critical strategic metal, lithium is subject to increasingly stringent resource utilization efficiency requirements. Lithium precipitated mother liquor is the final hurdle in the recovery of lithium resources. Due to its high sodium-to-lithium ratio, strong alkalinity, and complex impurity composition, it poses a significant challenge to the selectivity and stability of traditional extraction systems. In this study, we investigated the influence of different substituents on the enolization capacity of β-diketone extractant molecules based on the electrostatic distribution patterns of extractant molecules. Using this as the primary criterion, we developed a novel extraction system (IPE-Z/tributyl phosphate (TBP)) and examined the effects of various factors, such as pH, extractant concentration, co–extractant ratio and agitation intensity, on extraction yield. Furthermore, the adaptability of this extractant to different feed solutions was verified and its extraction mechanism analysed. The results show that this extractant can achieve over 85% extraction efficiency in a single-stage process and a sodium separation factor (βLi/Na) of 178.72. Meanwhile, the pH of the extractant raffinate is 7.9, suggesting that lithium can be extracted from lithium–precipitated mother liquor without consuming alkali. In the extractate, the coordination ratio of the extractant molecules, the co-extractant molecules, and the lithium ions is 1:1:1. Infrared spectroscopic analysis of the organic phase before and after extraction confirmed that the extractant’s molecular structure remains stable during extraction and back-extraction. Cyclic extraction experiments indicate that this extractant can achieve an extraction efficiency of 98.70% for lithium precipitated mother liquor. The pH of the raffinate is 7.2, enabling the near-neutral extraction of lithium from lithium-precipitated mother liquor, which demonstrates good industrial application prospects.