Synthesis, Characterization and Performance Evaluation of Lithium Manganese Oxide for Lithium Adsorption

The recovery of lithium from seawater via adsorption is a promising separation technique that could be incorporated within integrated salt recovery schemes. In this work, spinel-type manganese oxide adsorbents were prepared and utilized for selective lithium adsorption from synthetic solutions. The semi-dry solid-state method was adopted to prepare spinel-type ion sieves using different manganese and lithium sources; manganese carbonate, manganese oxide, lithium carbonate and lithium hydroxide. Synthesis was conducted at different Li/Mn starting molar ratios, firing temperatures and firing durations. The prepared spinels were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Moreover, average particle size and zeta potential were measured for selected spinel adsorbents. In addition, their sorption capacities and lithium removal efficiencies from synthetic solutions were evaluated. Lithium uptake results suggested that the spinels (H1.1Li0.08Mn1.73O4.05) prepared from manganese carbonate and lithium hydroxide at Li/Mn ratio of 0.75 exhibited at pH 12 the highest lithium sorption capacity among other prepared spinels. The equilibrium of lithium sorption onto this adsorbent was best described by Langmuir isotherm model and the maximum equilibrium sorption capacity was found to be 50 mg/g. This capacity was obtained using 0.25 g/L of the adsorbent at pH 12 and its value is higher than previously reported values. Thus, the prepared spinel shows promising features that favor its utilization for lithium removal from wastewater and concentrated brines.