Steering interlayer interaction of lithium-aluminum layered double hydroxide beads for stable lithium extraction from sulfate-type brines

Lithium-aluminum layered double hydroxide (LiAl-LDH) is the most successful industrialized adsorbents for lithium extraction from salt lake brines with high Mg²⁺/Li⁺ ratios. Nevertheless, its applications in SO₄²⁻-type brines hit an “Achilles heel”, i.e., the poor Li⁺ extraction due to the desorption obstacle arising from spontaneous intercalation of SO₄²⁻. Herein, a novel strategy of steering interlayer interaction was developed by embedding portion of PO₄³⁻ into interlayers of LiAl-LDH beads (BLDH-P). Owing to the lower binding energy (E_b) and stronger diffusion energy barrier of SO₄²⁻ within interlayers, BLDH-P featured property of preventing SO₄²⁻ intercalation, with the unchanged adsorption and desorption capacity in Lop Nor brine (the largest SO₄²⁻-type brine in the world) during the long-term recycling. BLDH-P also showed excellent Li⁺ extraction performance, as the results of enlarged interlayer spacing and selective electrostatic repulsion. The static and dynamic Li⁺ uptake reached 5.26 mg/g and 3.96 mg/g, with high separation factors of 39.84, 48.14, and 144.87 for Li⁺/K⁺, Li⁺/Na⁺, and Li⁺/Mg²⁺, respectively, superior to those of reported and commercialized LiAl-LDH. This work offers a feasible strategy of using interlayer modulation for long-term Li⁺ extraction by LiAl-LDH from SO₄²⁻-type brines, and inspires the development and design of next-generation lithium adsorbents.