Recovery of Li2SO4 from lithium-precipitated mother liquor via a Pb/FePO4 membrane-free electrochemical system

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2023-07, Vol.467, p.143247, Article 143247
• Main Authors: Huang, Zian, Xu, Wenhua, Zhao, Zhongwei, Liu, Dongfu, He, Lihua, Liu, Xuheng
• Format: Article
• Language: English
• Subjects: Electrochemical membrane-free system; LiFePO4; Lithium extraction; Lithium-precipitated mother liquor
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2023.143247

[Display omitted] •A novel “(+) Pb/FePO4 (−)” membrane-free Li2SO4 extraction system is proposed.•The new method suits Li+ extraction from the lithium-precipitated mother liquor.•Li+ concentration can be reduced to 0.014 g·L−1 with a Li+ recovery rate of 98.9%.•The separation coefficient of lithium to sodium is up to 304. Ore is the primary source of Li2CO3 production, but approximately 10–15% of lithium remains in the lithium-precipitated mother liquor for each ton of Li2CO3 produced. Therefore, efficient recovery of Li2SO4 from this solution is essential to ensure Li2CO3 supply. The conventional “(+) LiFePO4/FePO4 (−)” membrane system has been successfully used to extract LiCl from brine. However, the large radius of SO42− in the mother liquor significantly increases the cell voltage of this system, which is not favorable for separating Li+ and Na+. We therefore developed a novel “(+) Pb/FePO4 (−)” membrane-free Li2SO4 extraction system that uses Pb and FePO4 to capture SO42− and Li+, which was then released by switching the electrode polarity after the adsorption was completed. The Li+ concentration in the mother liquor decreased from 1.3 to 0.014 g·L−1 in two cycles, and the Li+ recovery rate was 98.9%. The Li+ concentration in the recovery liquor reached 1.356 g·L−1, with a Li–Na separation coefficient of 304. In addition, the new system did not suffer from lead dissolution loss, and the adsorption capacity of Li+ was 95.44% of the initial capacity after 15 cycles. Overall, this membrane-free lithium extraction system can provide a direction for extracting Li2SO4 from sulfate systems.