Dual-modification engineering of Al-based Li adsorbents for enhanced sulfate resistance and anion-selective lithium...

Adsorption-based lithium extraction provides a convenient, efficient, and environmentally friendly route for recovering lithium from liquid resources. Among existing materials, aluminum-based adsorbents are the only systems that have achieved industrial-scale deployment; however, they still suffer from insufficient lithium uptake and structural deactivation during long-term dynamic cycles in sulfate-type salt-lake brines. To address these limitations, a dual-modified lithium-aluminum layered double hydroxide (PGLH) was synthesized via microemulsion-assisted coprecipitation.Structural characterization and computational analyses reveal that the intercalation of polycarboxylates within the interlayer galleries, coupled with graphene oxide (GO) surface modification, synergistically reinforces the layered framework and enhances Li⁺ selectivity. In gradient-concentration real sulfate-type brines, PGLH delivers a lithium adsorption capacity of 17.8 mg·g^-1. Sulfate resistance experiments and molecular dynamics simulations demonstrated a 260% increase in lithium uptake compared to unmodified adsorbents, along with 96.1% capacity retention after fifty cycles, which is attributed to steric hindrance and electrostatic repulsion that effectively suppress sulfate intercalation. Continuous-flow column tests further verified the material's durability, achieving more than tenfold Li⁺ enrichment and reducing the Mg/Li ratio from 2938:1 to 10:1. These findings provide mechanistic insights and design guidelines for developing robust, selective Al-based lithium adsorbents suitable for sulfate-rich brines.