Comparative Investigation of Natural Mineral-Supported Li/Al-LDHs Adsorbents for Lithium Recovery from High Mg/Li Ratio Brines

Lithium recovery from salt lake brines with high Mg/Li ratios remains highly challenging due to the comparable physicochemical properties of Mg2+ and Li+, while lithium–aluminum-layered double hydroxides (Li/Al-LDHs) have emerged as promising lithium-selective adsorbents. However, their practical application is hindered by particle aggregation, limited structural stability, and insufficient processability under continuous-flow conditions. Herein, a mineral-directed synthesis strategy was developed to construct natural mineral-supported Li/Al-LDHs composite adsorbents using three abundant clay minerals, chlorite, montmorillonite, and illite, as structural substrates. The mineral crystal structures were demonstrated to regulate the nucleation, growth behavior, and dispersion of Li/Al-LDH nanosheets, resulting in distinct hierarchical architectures and lithium adsorption performances. Comprehensive structural characterization revealed the successful integration of Li/Al-LDH phases with different mineral matrices while preserving the intrinsic layered structures of both components. The results demonstrated that different mineral substrates significantly influenced the crystal growth, dispersion, and interfacial structure of Li/Al-LDHs. Among the prepared composites, montmorillonite @Li/Al-LDHs exhibited the optimal lithium adsorption performance, achieving a lithium adsorption capacity of 6.0 mg·g−1 and a remarkable Li+/Mg2+ separation factor of 73.5 in a brine with a high Mg/Li ratio of 61.25. Furthermore, the optimized adsorbent maintained 81.7% of its initial adsorption capacity after 100 adsorption–desorption cycles and demonstrated stable lithium recovery performance under continuous-flow conditions. This work establishes the relationship between natural mineral crystal structures and Li/Al-LDH adsorption behaviors, providing new insights into the rational design of economical, scalable, and environmentally friendly lithium adsorbents for sustainable recovery of lithium resources from Mg-rich brines.