Investigation of Imprinted Polymers for Lithium-Ion Recovery from Low-Grade Brine: Preparation, Application, and Evaluation.

The surging demand for lithium in new energy storage has shifted the focus of lithium extraction from high-grade resources to low-grade brines. Low-grade brine is rich in lithium resources. However, its extraction process is quite challenging due to the severe interference from coexisting ions. Traditional extraction technologies are characterized by low selectivity and high energy consumption. In contrast, lithium-ion imprinted polymers (Li-IIPs) based on the "lock and key" recognition mechanism offer a promising alternative for the efficient recovery of lithium from low-grade brines. This review systematically summarizes the latest research achievements on Li-IIPs. It covers the preparation principles, selection criteria for raw materials, and comparative analysis of mainstream manufacturing methods. Surface imprinting technology is highlighted for its superiority in enhancing the adsorption capacity and mass transfer efficiency by mitigating imprinted site encapsulation. Moreover, a comprehensive performance evaluation system is established. It includes adsorption capacity, selectivity, kinetics, and regeneration stability, with emphasis on the regulatory effects of complex brine conditions (pH, time, temperature, and coexisting ions). The synergistic effects of Li-IIPs in combination with precipitation, membrane separation, solvent extraction, and other emerging technologies are further discussed. Finally, the current bottlenecks and future development directions are identified. Overall, this review aims to provide guidance for the advancement of Li-IIP technology and facilitate its translation from the laboratory scale to the industrial scale, thereby promoting the extraction of lithium resources from low-grade brines.