Recovery of lithium from the desorption solutions of salt lakes using β-diketone synergistic extraction system

Lithium has become increasingly important because of its irreplaceable role in lithium-ion batteries. Addressing the complex process and high energy consumption of the current adsorption-membrane integrated process for lithium extraction from high Mg/Li ratio salt lake brine, this study put forward an integrated process of adsorption-solvent extraction. Taking the desorption solution of adsorption method as raw material, the process parameters and extraction mechanism of lithium by the novel extraction system were investigated. A novel process of lithium recovery from the desorption solutions of salt lakes by solvent extraction was proposed for the first time. The composition of the extraction system was studied and determined to be HTTA-P113-kerosene. Compared with the previously reported neutral ligands (TOPO, Cyanex923), P113 not only exhibited excellent synergistic extraction ability but also had good miscibility and a green synthesis process. The effects of saponification degree, extraction time, temperature and phase ratio on lithium extraction and βLi/Na were systematically investigated. Through the four-stage countercurrent extraction, more than 99.2 % of lithium could be extracted by the organic phase consisting of 0.4 mol L−1 HTTA, 0.4 mol L−1 P113, saponification degree of 80 % at O/A ratio of 1:1 and equilibrium pH of 6.78. Furthermore, after the scrubbing and stripping process, the lithium-rich solution containing 21.64 g L−1 Li+ and 0.037 g L−1 Na+ was obtained. The Li2CO3 products with a purity of 99.5 % were successfully prepared from the lithium-rich solution by precipitation method. Finally, the extraction mechanism was studied via the slope analysis method and FT-IR spectra. It was indicated that the extracted lithium species were Li(TTA)(P113).