Nanocomposite Sorbents Based on TiO2 Containing Manganese Spinel for Concentration of Lithium Ions

A method for obtaining nanocomposite sorbents, which are selective towards $\mathrm{L}\mathrm{i}^{+}$ ions, has been proposed. The samples are based on adsorptive active anatase, the selective component is lithium-manganese spinel $\mathrm{L}\mathrm{i}\mathrm{M}\mathrm{n}_{2}\mathrm{O}_{4}$. This component was synthesized preliminarily, its nanoparticles were inserted to the sol of insoluble titanium hydroxocomplexes, the nanocomposite was precipitated from this suspension and calcined at 500° C. A number of sorbents with different molar ratio of Ti:Mn was obtained by this manner, they were investigated by means of chemical analysis, X-ray diffraction, optical microscopy, TEM and SEM. The size of nanocrystallites is 20-30nm. Increasing the spinel amount has been found to decrease the sorbent grain size, however, they are mechanically durable due to $\mathrm{T}\mathrm{i}\mathrm{O}_{2}$, which is a binder. Adsorption of $\mathrm{L}\mathrm{i}^{+}$ from the solution containing an excess of $\mathrm{N}\mathrm{a}^{+}$ ions was studied. The optimal amount of $\mathrm{L}\mathrm{i}\mathrm{M}\mathrm{n}_{2}\mathrm{O}_{4}$ (13 %) has been found. The sample is obtained in a form of rather large grains $(\approx 0.3 \mathrm{~mm})$, the selectivity coefficient $\mathrm{L}\mathrm{i}^{+}/\mathrm{N}\mathrm{a}^{+}$ is about 500. The sorbent is regenerated with a 1 M HNO3 solution without manganese leakage. After 10 cycles of sorption-desorption, the concentrate was obtained, Further the concentrate can be used for $\mathrm{L}\mathrm{i}_{2}\mathrm{C}\mathrm{O}_{3}$ precipitation.