Synthesis and Adsorption Properties of Li1.6Mn1.6O4 by a Combination of Redox Precipitation and Solid-Phase Reaction

Orthorhombic LiMnO2 (o-LiMnO2), spinel Li1.6Mn1.6O4 precusors, and spinel H1.6Mn1.6O4 ion sieves were synthesized by a combination of controlled redox precipitation and solid-phase reaction. o-LiMnO2 was synthesized by a controlled redox precipitation using Mn­(OH)2, LiOH, and (NH4)2S2O8. Spinel Li1.6Mn1.6O4 precursor was prepared by the heat treatment of o-LiMnO2. Further, an ion sieve (H1.6Mn1.6O4) was synthesized by the acid (HCl) treatment of Li1.6Mn1.6O4. The effect of redox precipitation and solid-phase reaction on the structure and ion-exchange property of the ion sieve was examined by powder X-ray diffraction, scanning electron microscopy, and Li+-selective adsorption measurements. The results showed that the ion sieve exhibited highly selective adsorption capacity for Li+ (3.88 mmol·g–1) from Qarhan salt lake brine, which was significant for the Li+ extraction from low-grade brine.