Lithium extraction from salt lake brine with a high mass ratio of Mg/Li by counter-current method using TBP-DIBK extraction system was investigated in this study. In the extraction process, TBP and DIBK acted as extractant, kerosene was used as diluent, and FeCl3was used as co-extractant. The operation conditions of extraction, scrubbing, stripping, and regeneration were investigated. In this study, 5.5 mol/L LiCl + 0.5 mol/L HCl was used as a scrubbing solution for purifying products, and 6 mol/L HCl solution was used as a stripping agent to transfer Li+from organic phase to aqueous phase. Furthermore, 2 mol/L NaOH and saturated MgCl2were used as the regeneration agent to remove H+from organic phase. The counter-current extraction experiments of 3-1-1-3 stages were carried out. After 10 cycles, the lithium extraction efficiency reached 99.90%; the separation factor of Li/Mg, Li/K, Li/Na, and Li/Ca was 5.215 × 104, 2.159 × 103, 3.659 × 102, and 3.104 × 102, respectively. The results indicated that the TBP-DIBK extraction system was effective at extracting lithium from salt lake brine with a high mass ratio of Mg/Li. Furthermore, the study of extraction thermodynamics suggested that lithium extraction was an exothermic process and that lower temperature promoted lithium extraction.Keywords:lithium extraction;salt lake brine;TBP-DIBK;extraction thermodynamics
To develop a more stable and more efficient extraction system, a novel amide extraction system, containing extractant N , N -bis(2-ethylhexyl) acetamide (N523) and diluent diisobutyl ketone (DIBK), was proposed in this work. A series of operation conditions, such as the concentration of initial lithium in aqueous phase, the volume ratio of N523 and DIBK, phase ratio of O / A , the molar ratio of Fe/Li, were carried out. The lithium extraction rate reached up to 92% under the optimal extraction conditions. Considering the mass transfer of two phases and consumption of extractant, the three-stage counter-current extraction experiment was conducted. After 6 cycles experiment of the three stage counter-current extraction, the lithium extraction rate reached 99.89% and the separation factor of Li/Mg, Li/Na, Li/K, and Li/Ca were 103,300, 5288, 5233, and 760.4, respectively. The stoichiometry of the complex was LiFeCl 4 ·N523 by the slope method. The results indicated that N523-DIBK extraction system was effective to recovery of lithium from salt lake brine with high mass ratio of Mg/Li. Furthermore, the extraction thermodynamics study revealed lithium extraction was an exothermic process, which meant lower temperature promoted lithium extraction. Graphical Abstract
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