Regulating lithium extraction based on intercalated SO42- in Li/Al-LDHs.

ABSTRACT

Reasonable construction of Li/Al-LDHs with interlayer anions is essential to improve the adsorption performance, especially for intercalating SO42- anions and blocking Li+ desorption. Hence, anion exchange between Cl- and SO42- in the interlayer of Li/Al-LDHs was designed and prepared to demonstrate the strong exchangeability of SO42- for Cl- intercalated in the Li/Al-LDH interlayer. Intercalated SO42- enlarged the interlayer spacing and significantly transformed the stacking structure of Li/Al-LDHs, resulting in fluctuating adsorption performance with changes in the intercalated SO42- content at different ionic strengths. What is more, SO42- repelled the intercalation of other anions, thus inhibiting Li+ adsorption, as verified by the negative correlation between adsorption performance and intercalated SO42- content in high-ionic-concentration brines. Desorption experiments further revealed that enhanced electrostatic attraction between SO42- and the Li/Al-LDH laminates hindered Li+ desorption. Additional Li+ in the laminates was essential for preserving the structural stability of Li/Al-LDHs with higher SO42- contents. This work provides a new insight into the development of functional Li/Al-LDHs in ion adsorption and energy conversion applications.