Immobilization of hydrogen manganese oxide (HMO) on alpha-alumina bead (AAB) to effective recovery of Li+ from seawater

• Spinel type hydrogen manganese oxide (HMO) is immobilized on alpha-alumina bead (AAB).
• HMO immobilized AAB (HMO/AAB) shows excellent Li+ adsorption capacity in real seawater.
• The highest Li+ recovery was obtained with 4 M Li/Mn precursor concentration.
• HMO/AAB shows less than 2% Li+ adsorption capacity loss after 14 repeated use.

In this study, hydrogen manganese oxide (HMO) is immobilized on alpha-alumina beads (AABs) to effectively recover Li+ from seawater. HMO is immobilized on AABs by immersing AABs in Li/Mn acetate solution followed by calcination and acid treatment. The concentration of the Li/Mn acetate solution was varied from 2 to 8 M. The amount of HMO immobilized on the AABs increased proportionally to the concentration of the Li/Mn acetate solution and became saturated at 6 M due to limited surface area. The samples prepared with 6 and 8 M solutions showed maximum HMO loadings of 69.3–75.6 mg/cm3. In seawater spiked with 30 mg/L Li+, HMO showed the highest Li+ adsorption capacity (21.7 Li+ mg/HMO g) when the Li/Mn precursor concentration was 2 M. Considering the Li+ adsorption capacity and the immobilized amount of HMO on AAB, the highest amount of recovered Li+ per volume was achieved with a Li/Mn precursor concentration of 4 M. AABs with immobilized HMO (4 M Li/Mn precursor) showed an excellent Li+ adsorption capacity (8.87 mg Li+/g HMO) in real seawater, even though the Li+ concentration in seawater is low.HMO/AAB shows even greater Li+ adsorption capacity than HMO powder because immobilization improve the seawater contact with HMO. After the Li+ adsorption–desorption process was repeated 14 times, HMO immobilized on AAB lost less than 2% of its Li+ adsorption capacity compared with fresh HMO. This result demonstrates the potential of HMO immobilized on AAB to recover Li+ from seawater.