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

Abstract

AbstractAluminum‐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. SO42− 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 SO42− would not obviously change the chemical environment of interlayer Cl−. Experiments as well as DFT and FEM simulations indicated the intercalated SO42− 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 SO42− 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 SO42− intercalation in interlayers reduced the subsequent Li+ adsorption capacity and increased the desorption difficulty.