ZIF-8-Functionalized Manganese-Based Lithium-Ion Sieve: Synthesis and Lithium-Selective Extraction

The critical role of lithium in powering the new energy economy necessitates prioritizing efficient extraction methods. This study investigates a novel zeolitic imidazolate frame work (ZIF-8)-coated manganese-based lithium-ion sieve (LIS) for enhanced lithium recovery. The precursor of LIS, Li1.6Mn1.6O4, was synthesized via the hydrothermal method, followed by acid pickling to obtain the spinel lithium-ion sieve H1.6Mn1.6O4. The material was then immersed in a 2-methylimidazole/Zn(NO3)2 solution, undergoing ultrasonic-assisted hydrothermal growth to form H1.6Mn1.6O4@ZIF-8 composites. Under optimized conditions (30 °C, pH = 11, 24 h), the composite demonstrated superior lithium extraction performance compared to single-phase adsorbents, reaching 26.62 mg/g in the solution with 250 mg/L Li+. The adsorption capacity of the composite increased with Li+ concentration and reaction time. The adsorption kinetics followed a pseudo-second-order kinetic model and were dominated by chemisorption. The H1.6Mn1.6O4@ZIF-8 composite exhibited an enhanced Li+ partition coefficient Kd of 118.3 in a mixed solution containing ions such as Li+, Mg2+, K+, and Ca2+, each with a concentration of 250 mg/L (pH = 12); good structural stability with manganese dissolution of 1.6%; and a capacity retention of approximately 79.5% after five cycles (CLi+ = 250 mg/L).