Highly porous and surface-expanded spinel hydrogen manganese oxide (HMO)/Al2O3 composite for effective lithium (Li) recovery from seawater

Lithium (Li) recovery from seawater is currently attracting great attention due to increasing industrial demand. Hydrogen manganese oxide (HMO) is a promising adsorbent for Li recovery from seawater, but powder-type HMO is difficult to apply and it is essential to obtain a granulated material for practical application. To minimize Li adsorption capacity loss and to obtain high mechanical stability in seawater, highly porous cylindrical HMO/Al2O3 composites have been synthesized, and their Li adsorption behavior has been investigated in seawater. Various ratios (1:4, 1:5, 1:9, 1:19, and 1:39) of lithium manganese oxide (LMO):alumina gel were tested for the synthesis of HMO/Al2O3 composites. All of the LMO/Al2O3 composites exhibited large surface area owing to the mesoporous character of gamma-Al2O3. By increasing the Al(2)O(3)content in the composite, the surface area is expanded and a more porous structure is obtained, but the crystallinity of the spinel phase of LMO is decreased. After delithiation, the HMO/Al2O3 composite was applied for Li adsorption from seawater. HMO/Al2O3 composites exhibited similar Li uptakes compared to HMO powder (ca. 9 mg Li/g HMO) due to their highly expanded surface area and porous structure. During the recovery of Li adsorbed on the HMO/Al2O3 composites by acid treatment, more manganese (Mn) was dissolved from composites containing more Al2O3 due to the low crystallinity of the spinel HMO. Finally, it was found that HMO/Al2O3 containing 25% Al2O3 exhibited less than 1% Mn dissolution, and its Li adsorption performance did not decrease over five Li adsorption-desorption cycles.