In this study, α-LiAlO2 was investigated for the first time as a Li-capturing positive electrode material to recover Li from aqueous Li resources. The material was synthesized using hydrothermal synthesis and air annealing, which is a low-cost and low-energy fabrication process. The physical characterization showed that the material formed an α-LiAlO2 phase, and electrochemical activation revealed the presence of AlO2* as a Li deficient form that can intercalate Li+. The AlO2*/activated carbon electrode pair showed selective capture of Li+ ions when the concentrations were between 100 mM and 25 mM. In mono salt solution comprising 25 mM LiCl, the adsorption capacity was 8.25 mg g-1, and the energy consumption was 27.98 Wh mol Li-1. The system can also handle complex solutions such as first-pass seawater reverse osmosis brine, which has a slightly higher concentration of Li than seawater at 0.34 ppm.
This review critically examines the effectiveness of ion-imprinted membranes (IIMs) in selectively recovering lithium (Li) from challenging sources such as seawater and brine. These membranes feature customized binding sites that specifically target Li ions, enabling selective separation from other ions, thanks to cavities shaped with crown ether or calixarene for improved selectivity. The review thoroughly investigates the application of IIMs in Li extraction, covering extensive sections on 12-crown-4 ether (a fundamental crown ether for Li), its modifications, calixarenes, and other materials for creating imprinting sites. It evaluates these systems against several criteria, including the source solution's complexity, Li+ concentration, operational pH, selectivity, and membrane's ability for regeneration and repeated use. This evaluation places IIMs as a leading-edge technology for Li extraction, surpassing traditional methods like ion-sieves, particularly in high Mg2+/Li+ ratio brines. It also highlights the developmental challenges of IIMs, focusing on optimizing adsorption, maintaining selectivity across varied ionic solutions, and enhancing permselectivity. The review reveals that while the bulk of research is still exploratory, only a limited portion has progressed to detailed lab verification, indicating that the application of IIMs in Li+ recovery is still at an embryonic stage, with no instances of pilot-scale trials reported. This thorough review elucidates the potential of IIMs in Li recovery, cataloging advancements, pinpointing challenges, and suggesting directions for forthcoming research endeavors. This informative synthesis serves as a valuable resource for both the scientific community and industry professionals navigating this evolving field.