Macroporous Hydrogen Manganese Oxide/Al2O3 for Effective Lithium Recovery from Seawater: Effects of the Macropores vs Mesopores

Hydrogen manganese oxide (HMO) has been widely investigated for recovery of lithium (Li) from seawater. For a practical application, it is essential to obtain a granulated HMO. However, granulation of HMO interferes seawater diffusion, thereby decreasing the Li adsorption performance. To minimize the hindrance of Li adsorption performance, macroporous LMO/Al2O3(MLA) was synthesized in this study. Highly porous γ-Al2O3 results in plenty of mesopores in cylindrical LMO/Al2O3. In addition, macropore is induced in LMO/Al2O3 by addition of hydrogel beads. During calcination, the hydrogel beads decomposed, leaving spherical macropores (500–1000 μm). After delithiation, Li adsorption performance of MLAs was evaluated in Li-spiked seawater. At high Li concentrations, all MLAs exhibited similar Li adsorption capacities. However, at low Li concentration (<50 mg/L), only MLA with the highest macropore density (porosity ≈ 60.3%) showed Li uptakes similar to that of HMO powder. In a dilute Li solution, such as seawate...