Effect of Ti-containing precursors on structure and adsorption performance of Li4Ti5O12 and Li2TiO3 oxides to Li+ ions

Using solid-phase synthesis method, Li4Ti5O12 and Li2TiO3 oxides were synthesized and used as adsorbents for Li+ ions. The physical–chemical properties were studied, using X-ray diffraction analysis, IR-spectroscopy, low-temperature adsorption–desorption of nitrogen, and scanning electron microscopy. It was shown that, using anatase as a Ti-containing precursor, single-phase oxides Li4Ti5O12 (d 26.5 nm, a 8.401 Å, V 569.5 Å3) and Li2TiO3 (d 26.5 nm, a 7.731 Å, V 462.1 Å3) with macro-mesoporous structure (ABET 11 and 16 m2/g, VBJH des 0.03 and 0.03 cm3/g, DBJH des 6 and 6 nm, respectively) and spherical-like morphology were obtained. For the samples obtained from rutile, an impurity of unreacted Ti-containing precursor was detected. The effect of the nature of Ti-containing precursors, concentration and temperature of HCl regeneration solution, and contact time on the degree of conversion to H-form and adsorption capacity of the obtained adsorbents was studied. The highest efficiency of ion exchange of Li+ ions with H+ (γH+ 96.7–100 %) was reached in conversion of adsorbents to H-form, during treatment with 0.1 M HCl at temperature of 70 °C for 48 h. Adsorbents H4Ti5O12 and H2TiO3 prepared from anatase showed higher adsorption efficiency of Li+ ions (qe 95.1 and 84.0 mg/g, α 34.7 and 32.9 %, respectively) compared to samples obtained from rutile (qe 75.7 and 81.2 mg/g, α 23.8 and 29.9 %, respectively). After three cycles of acid regeneration, the adsorption capacity was maintained at 40.6–47.0 mg/g for Li4Ti5O12, and at 34.8–38.4 mg/g for Li2TiO3, respectively. The hydrogen demonstration during adsorption–desorption cycles increased from 8.4 to 10.8 for Li4Ti5O12, and from 8.0 to 11.2 for Li2TiO3. Anatase Ti-containing precursor recrystallization into rutile modification and further amorphization was determined. The presented results are interesting for developing highly efficient adsorbents for Li+ ions recovery from aqueous solutions.