Synthesis of Li-Al-carbonate layered double hydroxide in a metal salt-free system

This work describes a novel method based on a metal salt-free system to synthesize a Li-Al-CO₃ layered double hydroxide (LDH) by simply adding powdered AlLi intermetallic compound (IMC) to a stirred water-bath at ambient temperature and atmosphere. The AlLi powder in the water-bath hydrolyzed strongly, subsequently forming an alkaline Al³⁺- and Li ⁺-containing aqueous solution of pH 12.3. Additionally, dissolution of CO₂ gas from the ambient atmosphere into the stirred alkaline solution produced the anion, CO₃^2-, in the solution to form Li-Al-CO₃ LDH. Washing in water was unnecessary because metal salts were not used to synthesize the LDH. Notably, transmission electron microscopy (TEM) results indicate that nano-sized Al particles were incorporated on the surface of Li-Al-CO₃ LDH flakes. Chemical analysis data suggest that the chemical formula of Li-Al-CO₃ LDH was Li _0.33Al_0.67(CO₃)_0.17(OH) ₂·mH₂O. This work also investigates the removal of the fluoride ions from an aqueous solution by using Li-Al-CO₃ LDH. Experimentally, residual fluoride concentration decreased to 0.4 ppm with an initial concentration of 20 ppm, which satisfies World Health Organization (WHO) guidelines for drinking water quality.