Why is aluminum‐based lithium adsorbent ineffective in Li+ extraction from sulfate‐type brines

Abstract Aluminum‐based lithium adsorbent (Li/Al‐LDH) is the only industrialized adsorbent for Li + extraction from salt lake brines. The inherent mechanism of declined Li + adsorption performance was revealed to explain the feebleness in sulfate‐type brines. SO 4 2− in brines could replace interlayer Cl − by a stronger electrostatic attraction with laminates, significantly altering the stacking structure and interlayer spacing, while Cl K‐edge of XAFS showed intercalated SO 4 2− would not obviously change the chemical environment of interlayer Cl − . Experiments as well as DFT and FEM simulations indicated the intercalated SO 4 2− regulated Li + adsorption of Li/Al‐LDHs at different ionic strength under a combined effect of expanded interlayers, close packing, and electrostatic repulsion. Although sufficient SO 4 2− contents in brines might promote the single Li + adsorption by offering ionic strength as a driving force, the long‐term usability would be severely impaired as SO 4 2− intercalation in interlayers reduced the subsequent Li + adsorption capacity and increased the desorption difficulty.