Impact of Anions and Water Content on [Li–Al] Layered Double-Hydroxide Stability

Abstract

[Li–Al] layered double hydroxides (LDHs) are compounds with potential as sorbents for lithium extraction from brine solutions. In this work, heat capacities were measured from approximately 2.5 to 300 K for six [Li–Al] LDHs with differing anions (Cl^–, OH^–, and SO₄^2–) and water content (denoted A for air-dried and O for oven-dried). These measurements were used to calculate the standard entropy at 298.15 K, and the results were combined with previously performed enthalpy measurements to calculate Gibbs energies of formation from the binary compounds. The calculated order of stability based on Gibbs energies of formation was Cl-LDH-O > OH-LDH-O > Cl-LDH-A > SO₄-LDH-O > SO₄-LDH-A > OH-LDH-A. Results support previous findings that higher water content generally raises the Gibbs energy of the LDH.