Synthesis of Porous Lithium Ion Sieve with High Purity for Li+ Adsorption

With the depletion of solid lithium ore, extracting lithium from salt lake brine has become a critical focus for future endeavors. A four-step method was used to synthesize high-purity H_1.6Mn_1.6O₄ for extracting Li⁺. Porous cubic Mn₂O₃ was hydrothermally synthesized with carbon spheres and surfactants as templates. Then, it was converted to LiMnO₂ by calcining with Li₂CO₃. After roasting and acid pickling, H_1.6Mn_1.6O₄ was successfully synthesized. The impacts of calcination temperature, Li/Mn molar ratio and glucose addition on LiMnO₂ composition, loss percentage of dissolved Mn in precursor, and the adsorption characteristics of the lithium ion sieve were studied. Glucose inhibited the formation of LiMn₂O₄ and promoted the formation of pure LiMnO₂. The resulting precursor without impurities showed porous structure. After acid pickling, H_1.6Mn_1.6O₄ showed a high-adsorption performance and excellent cycle performance. After five cycles, adsorption capacity remained above 30 mg/g, and the loss percentage of dissolved Mn stabilized at about 1%. The Li⁺-H⁺ exchange conformed to pseudo-second-order adsorption dynamics and the Langmuir adsorption isotherm equation, indicating that the adsorption process can be classified as monolayer chemical adsorption.