Lithium ion sieve synthesized via an improved solid state method and adsorption performance for West Taijinar Salt Lake brine

Monoclinic β-Li2TiO3 (LTO) is regarded as a lithium adsorbent precursor. In order to inhibit agglomeration during solid state reaction, C2H3LiO2·2H2O instead of Li2CO3 was firstly used as the lithium resource to synthesize LTO. Lithium ion sieve H2TiO3 (HTO) was then obtained by acid treatment of LTO. Physicochemical properties of obtained LTO and HTO were characterized via powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and particle size distribution analysis (PSD). Lithium adsorption selectivity and stability of prepared HTO for West Taijinar Salt Lake were investigated. Solid state reaction mechanism of C2H3LiO2·2H2O and TiO2 was investigated by TG-DTA analysis. Results show that melting of C2H3LiO2·2H2O (at 64.5 °C) during the early calcination stage could form liquid–solid phase and remarkably improve mixing of C2H3LiO2·2H2O and TiO2. Compared to Li2CO3 used as the lithium resource, huge heat and gases released during the reaction of dehydrated C2H3LiO2·2H2O and TiO2 (between 380 °C and 515 °C) accelerate the nucleation process and effectively inhibits agglomeration, which leads to a smaller particle size (∼70 nm). It is shown that lithium uptake and adsorption rate were improved because of easier mass transfer during the ion-exchange process. Lithium adsorption behavior could be well described by the Langmuir isotherm and pseudo-second-order kinetic model. Seperation factor α (Li/Mg) of obtained HTO in West Taijinar Salt Lake brine reached 5441.17, meaning remarkable lithium adsorption selectivity in real lake brine. Besides, adsorption uptake remained 24.5 mg/g after 5 cycles in West Taijinar Salt Lake brine, which indicates obtained HTO has good stability.