Bio-inspired UV-curing Li2TiO3 composite membrane for efficient lithium extraction from brine and seawater

Titanium (Ti)-based lithium ion sieves (LISs) have advantages such as structural stability and environmental friendliness, making them promising for lithium extraction from salt lake brine. However, the adsorption kinetics and capacity of granulated Ti-based LISs are very limited, which restricts their industrial applications. Inspired by biomimetic channels for Li transport, herein, a Ti-based LISs membrane with fast kinetics and high adsorption capacity has been proposed. Firstly, a flower-shaped Li 2 TiO 3 (LTO) assembled by nanosheets with a superhydrophilic surface was prepared for the first time. Thereafter, the LTO was compounded into poly (oligo (ethylene glycol) methacrylate) (POEGMA) through UV-curing to obtain the PP@POEGMA/LTO membrane. Due to the lithiophilic properties of oligoethers in POEGMA, Li + ions could pass through the inner pathway preferentially and rapidly. Furthermore, the abundant hydroxyl functional groups in POEGMA enhanced the hydrophilicity of membrane, facilitating the mass transfer of ad/desorption. After 0.1 mol·L −1 HCl elution to obtain PP@POEGMA/HTO composite membrane, the adsorption equilibrium of membrane was found to achieve within 4 h, as fast as that of the powders HTO. Meanwhile, the equilibrium adsorption capacity reached 32.19 mg·g −1 . Dynamic adsorption experiments revealed that the composite membrane maintained a lithium removal rate of over 80 % within 30 min, with the adsorption capacity stabilizing at 20 mg·g −1 after five cycles. As for selective adsorption experiments in the Qarhan salt-lake brine and natural seawater, PP@POEGMA/HTO membrane showed a Li/Mg separation factor of 86.4 in spite of the Mg/Li as high as 249, and Li/Na separation factor of 14,508 in spite of the Na/Li as high as 60674, respectively. This work provides a straightforward approach for LISs membrane to achieving high-efficiency recovery, promoting their application in practical industries.