Selective separation of lithium ions by MnO2 nanocrystals

The main objective of this study was synthesis of proper ion sieves for selective extraction of lithium from solutions. Therefore, in the first stage, MnO2 nanostructure oxidizer, spinel type Li-Mn-O precursor and lithium ion sieve of MnO2 nanorods were synthesized under two different conditions of a controlled hydrothermal method and the structure characteristics and ion exchange ability were studied by XRD and SEM analysis. Then, the Li+ adsorption isotherm, kinetics and selectivity measurements were investigated, separately. The produced MnO2 nanorods, with the size about 30–60 nm in diameter and 0.5–2 μm in length, were found to have a remarkable lithium ion-sieve property. In addition, the study on equilibrium distribution coefficients (Kd) of synthesized ion sieve indicating high selectivity for Li+ ions in the presence of other coexisting ions such as Na+, K+ and Mg2. In addition, adsorption isotherm followed the Langmuir equation and the maximum monolayer uptake capacity of Li+ ions was 4.45 mmol/g estimated in the optimized condition. Consequently, it appears that the synthesized ion sieves have the adequate potential for extraction lithium from brines or seawater.