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

Solid-phase reactions were used for the synthetization of the spinel Li 1.6 Mn 1.6 O 4 powder and the lithium ion-sieve MnO 2 ·0.5H 2 O was subsequently obtained by the leaching of the lithium. The physical characterization showed that the polycrystalline precursor and the MnO 2 ·0.5H 2 O 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 (26.13 ​mg ​g−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. Due to the sieving effect (steric hindrance effect and hydration free energy effect), the lithium ion-sieve selectively adsorbed Li+ when the ion-sieve was immersed in brine, indicating that the ion-sieve MnO 2 ·0.5H 2 O was expected to recover Li+ from the solutions including Salt Lake brine, seawater, and wastewater. Image 1 • The precursor was prepared by practical two-stage solid-phase sintering technique. • The Li 1.6 Mn 1.6 O 4 exhibited excellent adsorption performance. • The materials showed the highly selective adsorption from Qarhan raw brine. [ABSTRACT FROM AUTHOR]