Practical synthesis of manganese oxide MnO2·0.5H2O for an advanced and applicable lithium ion-sieve

Highlights: • The precursor was prepared by practical two-stage solid-phase sintering technique. • The Li_1.6Mn_1.6O₄ exhibited excellent adsorption performance. • The materials showed the highly selective adsorption from Qarhan raw brine. Solid-phase reactions were used for the synthetization of the spinel Li_1.6Mn_1.6O₄ powder and the lithium ion-sieve MnO₂·0.5H₂O was subsequently obtained by the leaching of the lithium. The physical characterization showed that the polycrystalline precursor and the MnO₂·0.5H₂O were nearly pure spinel, as well as that during the process of the adsorption-desorption, the structural stability was high. The Langmuir isotherm and pseudo second-order kinetics model showed consistency with the adsorption behavior, which indicated the presence of homogeneous adsorption sites for the lithium adsorption and that its process was chemisorption. Adsorbents were found to remain being characterized with a relatively high Li⁺ uptake (26.13mgg⁻¹) with low manganese extracted (1.71%) after the circulation experiment was performed up to 5 times, proving a significant repeatability and stability for the lithium ion-sieve. The concentration factors exhibited the highly selective adsorption capacity for absorbent from Qarhan raw brine with high concentrations of Na⁺, K⁺, Ca²⁺, Mg²⁺. The adsorbents could be efficiently used for Li⁺ recovery from Salt Lake brine as well as its excellent potential for further application.