Highly selective separation of lithium with hierarchical porous lithium-ion sieve microsphere derived from MXene

Lithium recovery from brine is critical for the sustainable development of energy-storage devices. However, the current lithium-ion sieve adsorbents are hampered by the adsorption rate and adsorption capacity. Herein, ultrathin nanosheets-assembled Li4Ti5O12 porous microspheres with hierarchical mesoporous structure are prepared by a hydrothermal method. Their high specific surface area (above 180 m2/g) exposed more adsorption sites and significantly accelerated the adsorption rate (equilibrium in 1 h). Besides, the H4Ti5O12 (HTO) microspheres showed superior Li+ adsorption capacity of 43.20 mg/g and high selectivity for Li+ from high Mg-containing aqueous solutions. The lithium adsorption over HTO is endothermic and can be well defined as pseudo-second-order kinetic model and Langmuir model, indicating the chemical adsorption and monolayer adsorption. The facial regeneration of HTO by HCl shows excellent stability and the Li+ adsorption capacity remains above 93% after 20 cycles. Thus, this HTO microspheres can be regarded as a helpful candidate for lithium recovery.