(588z) Design of Ion-Sieve for Selective Adsorption of Lithium from Geothermal Brine

The growing demand for lithium-ion batteries necessitates efficient and sustainable lithium extraction technologies. Geothermal brines provide an alternative lithium source; however, their complex ionic composition challenges selective lithium recovery. Hydrogen manganese oxides (H₄Mn_4.5O₁₂) are widely studied as lithium-ion sieves due to their high selectivity for lithium ions. Still, its structural instability and manganese dissolution during adsorption-desorption cycles limit long-term performance. This study introduced zirconium (Zr) doping into the spinel-type Li₄Mn₅O₁₂ precursor through a one-step calcination process (450 °C for 24 hours at 10 °C min⁻¹), ensuring an energy-efficient synthesis process of Li₄Mn_4.5Zr_0.5O₁₂ (LMZO) matrix. The resulting spinel H₄Mn_4.5Zr_0.5O₁₂ (HMZO), after acid activation, underwent comprehensive characterization employing several analytical techniques, including Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) surface area, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The HMZO exhibited a lithium adsorption capacity of 26.81 mg/g in synthetic brine, with a maximum capacity of 35 mg/g at an adsorbent-to-solution ratio of 0.017 g/50 mL, while restricting manganese dissolution to 0.78% after five adsorption-desorption cycles. Adsorption kinetics followed the pseudo-second-order model, while the Freundlich isotherm indicated a heterogeneous Li-H ion exchange mechanism. The thermodynamic analysis confirmed that lithium adsorption was endothermic and entropy-driven, improving with increased temperature. These findings highlight the enhanced stability and reusability of HMZO, demonstrating its potential as a next-generation lithium-ion sieve for sustainable lithium recovery from geothermal brines. Further optimization, including refining zirconium content and activation conditions, is necessary to maximize long-term adsorption performance.