Enhancing Cyclic Performance of Lithium–Aluminum Layered Double Hydroxides Type Adsorbents via Vanadium Anions Intercalation for Li⁺ Extraction from Sulfate-Type Brines

Owing to its excellent eco-friendliness and facile water elution properties, aluminum-based lithium adsorbents have attracted a surge of interest for selectively extracting Li⁺ from Salt Lake brines, which account for more than 60% of the global lithium resources. However, structural collapse, facile deactivation during desorption process, and ultra-low actual adsorption capacity limit its further large-scale application, particularly in low-grade sulfate-type brines. Herein, considering its advantages, limitations, and structural features, the structural collapse of the aluminum-based lithium adsorbent was effectively suppressed by the in situ intercalation of VO₃⁻ and V₂O₇⁴⁻ into the interlayer of [LiAl₂(OH)₆]⁺. Evidently, the initial adsorption capacity and α_Mg^Li of as-configured adsorbents powder are 14.96 mg g⁻¹ and 192.42 in real sulfate-type West Taijinar Salt Lake brines following NaCl salts removal with 800 mg L⁻¹ Li⁺ and 9.56 g L⁻¹ SO₄²⁻. Furthermore, the initial and retained adsorption capacities of these novel adsorbents granulate in brines after 100 adsorption/desorption cycles are 26.68 and 10.36 mg g⁻¹, respectively, which are almost 10 times higher than those of industrially utilized products. Based on experiments and density functional theory calculations, the process and mechanism of anion intercalation control were preliminarily elucidated. Furthermore, research findings indicate that intercalated anions can influence not only interlayer interactions but also the backbone strength of LDH-type adsorbents. This work significantly overcomes the major utilization challenges of aluminum-based lithium adsorbents, thereby enabling the high-efficiency and stable extraction of Li⁺ from low-grade brines, including sulfate-type brines.