Nanofiltration membrane for enhancement in lithium recovery from salt-lake brine: A review

Lithium recovery from salt-lake brines is experiencing an tremendous increase in demands due to the rapid growth in the manufacture of electric vehicles and electronics products. The development of cost-effective technologies has therefore become greatly important. This article comprehensively reviews nanofiltration (NF) technology for lithium uptake and recovery. Surface grafting, aqueous additives, non-conventional monomers, and interlayer modifications are effective to obtain selective NF membranes according to layer-tailored strategies. Positively charged NF membranes outperform commercial negatively charged ones in lithium extraction from salt-lake brines due to important synergistic effects such as the Donnan effect, steric hindrance, and dielectric effects. Furthermore, the improvement in separation performances can be achieved by employing multi-step NF processes. Due to its better capability and adaptability in currently used production facilities, the positively charged NF-based technology plays a vital role in the ion-targeted separation and enrichment. Further identification of industrial challenges and development of better solutions would significantly advance technologies for efficient lithium recovery from various sources (e.g., salt-lake brines) and, therefore, address the challenges on globally increasing demands for lithium resources.