A fundamental study on selective extraction of Li with dibenzo-14-crown-4 ether: Toward new technology development for lithium recovery from brines.

The present study has proposed a selective Li extraction process using a novel extractant of dibenzo-14-crown-4 ether functionalized with an alkyl C16 chain (DB14C4-C16) synthesized based on the ion imprinting technology (IIT). Theoretical analysis of the possible complexes formed by DB14C4-C16 with Li and the competing ions of Na, K, Ca and Mg was performed through density functional theory (DFT) modeling. The Gibbs free energy change of the complexes of metal ions with DB14C4-C16 and water molecules were calculated to be -125.81 and -166.01 kJ/mol for lithium, -55.73 and -117.77 kJ/mol for sodium, and -196.02 and -291.52 kJ/mol for magnesium, respectively. Furthermore, the solvent extraction experiments were carried out in both single Li and multi-ions containing solutions, and the results delivered a good selectivity of DB14C4-C16 towards Li over the competing ions, showing separation coefficients of 68.09 for Ca-Li, 24.53 for K-Li, 16.32 for Na-Li, and 3.99 for Mg-Li under the optimal conditions. The experimental results are generally in agreement with the theoretical calculations.