Hierarchical spheres of Mg–Al LDH for the removal of phosphate ions: effect of alumina polymorph as precursor†
In order to tailor the morphology of the layered double hydroxide (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. A three-dimensional network of plate-shaped LDH particles was formed when θ-Al2O3 and γ-Al2O3 were used, 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. The LDH particles prepared with θ-Al2O3 and γ-Al2O3 could remove the hydrogen phosphate ions (HPO42−) in a concentration of 0.40 mmol g−1 completely within 10 min; this is approximately 20 times shorter than the time taken by the LDH particles prepared from amorphous Al2O3.