Raiguel Stijn, Van Bogaert Laura, Balcaen Tim, Binnemans Koen
KU Leuven, Department of Chemistry Celestijnenlaan 200F P.O. box 2404 B-3001 Leuven Belgium
Green Chem. 2024 Dec 20;27(4):1194-1205. doi: 10.1039/d4gc04760e. eCollection 2025 Jan 20.
Direct lithium extraction (DLE) from natural surface and geothermal brines is very challenging due to the low ratio of lithium to other metals, and the lack of suitable materials that bind lithium with sufficiently high selectivity. In this paper, a synergistic solvent extraction system is described that comprises a liquid ion exchanger (saponified bis(2-ethylhexyl)dithiophosphoric acid) and a lithium-selective ligand (2,9-dibutyl-1,10-phenanthroline) in an aliphatic diluent. The extraction mechanism was investigated and was confirmed to involve the binding of lithium to the selective ligand, while the liquid ion exchanger facilitates the transfer of metal ions from the aqueous to the organic phase. The variables influencing the selectivity for lithium were also determined. The selectivity improved greatly in highly concentrated salt solutions with low concentrations of lithium, rendering the process ideal for the sequestration of lithium from natural brines. Stripping could be achieved with stoichiometric amounts of hydrochloric acid. Applying the system to a synthetic geothermal brine, an extraction percentage of 68% was obtained in a single stage, with separation factors of 620 ± 20 for lithium over sodium, 3100 ± 200 for lithium over potassium, 596 ± 9 for lithium over magnesium and 2290 ± 80 for lithium over calcium.
从天然地表水和地热卤水中直接提取锂（DLE）极具挑战性，这是因为锂与其他金属的比例较低，且缺乏能够以足够高的选择性结合锂的合适材料。本文描述了一种协同溶剂萃取体系，该体系由一种液体离子交换剂（皂化双（2-乙基己基）二硫代磷酸）和一种锂选择性配体（2,9-二丁基-1,10-菲咯啉）在脂肪族稀释剂中组成。对萃取机理进行了研究，证实其涉及锂与选择性配体的结合，而液体离子交换剂则促进金属离子从水相转移到有机相。还确定了影响锂选择性的变量。在锂浓度低的高浓度盐溶液中，选择性大大提高，这使得该工艺成为从天然卤水中螯合锂的理想选择。用化学计量的盐酸即可实现反萃取。将该体系应用于合成地热卤水，单级萃取率为68%，锂对钠的分离因子为620±20，锂对钾的分离因子为3100±200，锂对镁的分离因子为596±9，锂对钙的分离因子为2290±80。
