Design and adsorption performance of hollow structure nano-metatitanic acid lithium ion sieve with strong structure stability and large adsorption capacity

Lithium is a national strategic resource, and the high-efficiency separation of lithium and magnesium in Salt Lake is the key to ensure the sustainable utilization of lithium resources in China. It is vital important to develop a highly stable lithium ion adsorbent. In this work, Li2TiO3 is synthesized by calcination TiO2 and Li2CO3, then which is ion-exchanged with HCl solution to obtain H2TiO3. The experimental results show that hollow structure H2TiO3 has a large pore volume (2.67 cm3/g) and specific surface area (111.57 m2/g). The lithium adsorption performance is systematically investigated by using it as an adsorbent to recover of Li+ from aqueous solution. The adsorption experiments results show that high solution pH environment is more beneficial to adsorb of Li+, and the maximum adsorption capacity of 36.2mg/g is obtained at pH=13. The results of kinetic experiments indicate that the adsorption behavior of Li+ conforms to the pseudo-second-order model, demonstrating the adsorption process is chemosorption. Additionally, Li+ adsorption conforms to the Langmuir model, indicating adsorption behavior is monolayer adsorption. The thermodynamic experimental results show that the higher temperature is beneficial to Li+ adsorption, and the Gibbs free energy ΔGϴ of the adsorption process is negative, indicating that the adsorption process is spontaneous. Meanwhile, ΔHϴ is greater than zero, indicating the process is endothermic. The results of ion selectivity experiments show that H2TiO3 has a high selectivity for Li+ (2.91mmol·g-1) in a mixed solution contains of Li+, Na+, K+, Rb+ and Cs+. The sorption capacity of H2TiO3 also maintained at 27.55mg/g after 5 adsorption/desorption cycles, and the dissolution loss rate of titanium is only 0.07%, indicating the hollow H2TiO3 had a strong structure stability in the process of Li+ adsorption. Therefore, the hollow structure H2TiO3 lithium ion sieve with large adsorption capacity and high stability is a promising adsorbent in the application of lithium extraction from Salt Lake brine.