摘要
Dense LLTO-Al 2 O 3 membrane (∼20 μm) for /Li + from high Mg 2+ /Li + brine. • Optimised LLTO (x = 0.11, 1250 °C/6 h): tetragonal, 3.26 × 10 3 S/cm. • La-poor/La-rich enables 2D Li + transport; Mg 2+ blocked by size. • Intergranular defects are main pathway for Mg 2+ co-permeation. • Selectivity 16.06, 99.61% Mg 2+ rejection (6 h); energy 23.21 kW·h (24 h). To solve the problem of lithium extraction from salt lake brine with a high magnesium‑lithium ratio, a composite ceramic membrane electrodialysis technology based on perovskite-type superionic conductor Li 3x La 2/3-x TiO 3 (LLTO) was proposed. LLTO powder was synthesised by the sol-gel method. The lithium doping amount (x = 0.11), sintering temperature (1250 °C) and time (6 h) were systematically optimised to obtain tetragonal LLTO with high ionic conductivity (3.26 × 10 −3 S/cm). Then, the LLTO-Al 2 O 3 composite film was prepared by a spin coating process (PVA content of 20%, LLTO solid content of 0.08 g/mL, spin coating 10 times) with porous alumina as the substrate. After calcination at 1275 °C for 6 h, a dense film with a thickness of about 20 μm was formed. Molecular dynamics simulations show that the two-dimensional selective transport of Li can be realised in the LLTO inner layer based on the La-poor / La-rich alternating structure, while Mg 2+ is hindered by the size effect. Intergranular defects are the main pathway leading to the co-permeation of Mg 2+ . The electrodialysis experiment showed that the membrane had good selectivity (selectivity coefficient 16.06) and Mg 2+ rejection rate (99.61%) for Li at the initial stage of operation (6 h), and the energy consumption was 23.21 kWh after 24 h of electrodialysis. This study provides a reference for membrane material design, preparation process and transmission mechanism for lithium extraction from high magnesium‑lithium ratio brine, and has potential application value.
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