The demand for lithium resources continues to increase due to the rapid development of electronic vehicles, energy storage equipment, and other electronic products. Extracting lithium from salt lake brines is of great significance because of the predominance of brine lithium resources. Because both sodium and lithium ions are monovalent cations and have similar chemical properties, it is difficult to extract lithium from high-sodium brine. Herein, an adsorption-coupled electrochemical (ACEC) technology was utilized for lithium extraction. Manganese oxide coated with an ultrathin (1–2 nm) carbon layer (core@shell MnOx@C), obtained by a precursor method, is utilized as a membrane electrode in a membrane capacitive device. The crystal structure and carbon layer thickness of MnOx@C are effectively controlled by adjusting the preparation conditions. When the core is mainly a MnO phase, the lithium extraction capability of the membrane electrode is significantly improved. The lithium adsorption capacity reaches as high as 51.8 mg/g, and the adsorption time is 550 s from high-sodium brine (Na/Li ratio = 48.6). The desorption rate of lithium ions is 91.3% during a reverse process. Compared with either membrane capacitance or adsorption methods, the adsorption capacity reached with this technology is in the lead. The synergy of adsorption and Faradaic redox reactions leads to remarkably enhanced lithium extraction capability. This ACEC technology provides an alternative pathway to extract lithium from brines with high efficiency and facile operation.
Ang Mi,Xinbo Qin,Fei Zhang,Rongping Yun,Youjing Zhao,Min Wang,Xu Xiang
Salt-lake brines have emerged as a promising source of lithium; however, the separation of Li + ions from other coexisting ions remains challenging. To surmount this issue, a three-dimensional wrinkled membrane that was based on a H 1.6 Mn 1.6 O 4 (HMO) ion sieve and comprised graphene oxide (GO) and hydroxylated graphene (GOH) was fabricated in this study. The designed structure provided abundant channels for ion migration. The hydroxyl groups of graphene allowed the membrane to exhibit improved Na + –Li + sieving ability. The lithium adsorption capacity of HMO-GOH/GO (20.6 mg/g) was considerably higher than that of HMO (8.9 mg/g) in a low-concentration lithium solution. The adsorption capacity and separation coefficient of HMO-GOH/GO in a high-sodium brine of Na/Li = 49:1 (48.0 mg/g and 47.1) were higher than those of HMO (21.6 mg/g and 29.3, respectively). The adsorption capacity of HMO-GOH/GO remained at 90.8 % of its initial value after 10 adsorption–desorption cycles, thus demonstrating excellent cyclic stability. HMO/GO-GOH shows higher specific capacitance than HMO based on the cyclic voltammetry results. The density functional theory calculations on adsorption energy of Li + ·4H 2 O and the energy barrier across the GOH pore confirm the Na + /Li + sieving capability. The adsorption mechanism was studied by in situ Raman spectroscopy, verifying the formation of Li O bond during lithium adsorption. Overall, this study provides guidance in the pursuit of a remedy for Na Li separation.
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