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

Abstract

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, CO₃²⁻, 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. 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.