Recovery of Lithium from Seawater Using a New Type of Ion-Sieve Adsorbent Based on MgMn2O4

Abstract

A new type of ion-sieve manganese oxide, HMnO(Mg), was prepared by an acid treatment of MgMn₂O₄. The HMnO(Mg) showed a remarkably high selectivity for lithium ions among alkali metal and alkaline earth metal ions. The selectivity sequences were Na ? K ? Li for alkali metal ions and Mg ≤ Ca ≤ Sr ≤ Ba for alkaline earth metal ions at pH 8. The HMnO(Mg) showed a high selectivity for lithium ions in seawater. The lithium uptake increased with increasing solution pH and adsorption temperature. The maximum lithium uptake from native seawater reached 8.5 mg/g, corresponding to a lithium content of 1.8% in the form of Li₂O. The adsorbed lithium could easily be eluted with a dilute acid solution. The adsorptive capacity for lithium ions gradually decreased through repeated adsorption/elution cycles. The HMnO(Mg) after 4 cycles showed a lithium adsorptivity which was about 60% of the initial value.