Lithium adsorption properties of porous LiAl-layered double hydroxides synthesized using surfactants

Porous LiAl-layered double hydroxides (LiAl-LDHs) of Li₂Al₄(OH)₁₂](CO₃)·4H₂O were hydrothermally synthesized in one-pot by mixing LiCl, AlCl₃, urea, and one surfactant each (sodium dodecyl sulfate (SDS), octadecyl amine (OA), and sodium lauryl sulfonate (SLS)) as soft templates. The LiAl-LDHs were granulated by crosslinked sodium alginate. The LiAl-LDHs were characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and porosity. Special attention was focused on the rise of Li⁺ adsorption capacity based on the porous morphology in synthetic and real salt lake brine. The adsorption capacity of granulated LiAl-LDHs-SLS reaches 8.48 mg/g in a solution containing 300 mg/L of Li⁺ at pH = 7 and 11.8 mg/g from Da Qaidam brine with 1.0 g/L of Li⁺. Lithium adsorption followed the Langmuir isotherm and pseudo-second-order kinetics. Temperature, solution pH, and other electrolytes had a minor effect on the adsorption performance of porous LiAl-LDHs. The structure of surfactants had a significant influence on the porosity of synthesized LiAl-LDHs, and thus on the adsorption capacity.