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

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. 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.

Automated summary

Aluminum-based lithium adsorbent (Li/Al-LDH) is the only industrialized adsorbent for Li+ extraction from salt lake brines. The declined Li+ adsorption performance in sulfate-type brines is explained by the replacement of interlayer Cl- with SO42-, which alters the stacking structure and interlayer spacing. The intercalated SO42- regulates Li+ adsorption of Li/Al-LDHs through expanded interlayers, close packing, and electrostatic repulsion.