Granulation of Li1.33Mn1.67O4 (LMO) through the use of cross-linked chitosan for the effective recovery of Li+ from seawater

• Chitosan lithium manganese oxide (LMO) granule is meso-porous material.
• Sulfuric acid treatment extracts Li+ topotactically from chitosan LMO granule.
• Sulfuric acid treatment causes cross-linking of chitosan binder, simultaneously.
• Cross-linking of chitosan expands surface area and improves stability of granule.
• Chitosan granule shows similar Li+ adsorption capacity with powder adsorbent.

Spinel-structured lithium manganese oxides (LMOs) are the most effective material for the recovery of Li+ from seawater. LMO is granulated using chitosan as a binding material in this study. Prepared chitosan LMO granule is meso-porous material of which the pore size is 6.5–30.0 nm. In chitosan LMO granule, 19.4 wt% of chitosan is included in.Extraction of the Li+ from chitosan LMO granule is carried with 0.2 M sulfuric acid. X-ray diffraction (XRD) analysis confirmed that topotactical extraction of Li+ ion and 93% of Li+ extraction efficiency is obtained. After sulfuric acid treatment, Fourier transformation infrared spectrum (FTIR) of chitosan LMO granule peaks at 1650 and 1000–1400 cm−1 which represent NH3– and C–N functional groups of chitosan are significantly changed suggesting that chitosan in granule is cross-linked by reacting with SO42- ion in sulfuric acid. Cross-linking of chitosan causes increase of surface area from 2.37 to 14.58 g m−2. Also stability of chitosan LMO granule is improved from 88% to 100%.After Li+ extraction, LMO converts to hydrogen manganese oxide (HMO). Pseudo-second order kinetic model reveals that adsorption of Li+ onto chitosan HMO granule required more time than HMO powder because the diffusion of seawater into the chitosan binder occurred slowly. HMO powder and chitosan HMO granule exhibit similar (≈10 mg g−1) Li+ adsorption capacity when concentration of Li+ is 30 mg L−1. Because chitosan is water permeable polymer, Li+ adsorption capacity of HMO powder is not affected after granulation.