Hierarchical Spheres of Mg-Al LDH for Removal of Phosphate Ions: Effect of Alumina Polymorph as Precursor
In order to tailor the morphology of the layered double hydroxides (LDHs) particles, we focused on a synthesis method that involves the use of Al2O3 as a precursor, employing Al2O3 with different crystal structures (e.g., α-Al2O3, θ-Al2O3, and γ-Al2O3) as well as amorphous Al2O3. When θ-Al2O3 and γ-Al2O3 were used, a three-dimensional network of plate-shaped LDH particles was formed even though α-Al2O3 barely reacts to form the LDH phase. Finally, adsorption tests involving HPO42− ions confirmed that the fabricated LDH particles exhibited high ion-removal rates. Hydrogen phosphate ions (HPO42−) in a concentration of 0.40 mmol g−1 could be removed completely within 10 min using the LDH particles prepared with θ-γ-Al2O3 and γ-γ-Al2O3; this is approximately 20 times shorter than the time taken by the LDH particle prepared from amorphous γ-Al2O3.