| Summary: | Lithium extraction from salt lake brine is critical for satisfying the increasing demand of a variety of lithium products. We report lithium recovery from pre-synthesized LiAl-layered double hydroxides (LDHs) via a mild solution reaction. Lithium ions were released from solid LiAl-LDHs to obtain a lithium-bearing solution. The LiAl-LDHs phase was gradually transformed into a predominantly Al(OH)<sub>3</sub> phase with lithium recovery to the aqueous solution. The lithium recovery percentage and the concentration of the lithium-bearing solution were dependent on the crystallinity of LiAl-LDHs, the initial concentration of the LiAl-LDHs-1 slurry, the reaction temperature, and the reaction time. Under optimized conditions, the lithium recovery reached 86.2% and the Li<sup>+</sup> concentration in the filtrate is 141.6 mg/L. Interestingly, no aluminum ions were detected in the filtrate after solid−liquid separation with high crystallinity LiAl-LDHs, which indicated the complete separation of lithium and aluminum in the liquid and solid phases, respectively. The <sup>27</sup>Al NMR spectra of the solid products indicate that lithium recovery from the lattice vacancies of LiAl-LDHs affects the AlO<sub>6</sub> coordination in an octahedral configuration of the ordered Al(OH)<sub>3</sub> phase. The XPS O 1<i>s</i> spectra show that the O<sub>ad</sub> peak intensity increased and the O<sub>L</sub> peak intensity decreased with the increasing lithium recovery, which indicated that the Al-OH bond was gradually formed and the metal−oxygen−metal bond was broken.
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