Self‐Assembled 3D Hierarchically Structured Gamma Alumina by Hydrothermal Method

Self‐assembled γ‐ Al 2 O 3 with hierarchical structure was successfully obtained via thermolysis of γ‐boehmite (γ‐ AlOOH ) particles, which was hydrothermally derived from aluminum ammonium sulfate hydrate ( NH 4 Al ( SO 4 ) 2 ·12 H 2 O ), urea, poly‐glycol ( PEG )‐2000, and deionized water. SEM observations indicate that the as‐synthesized γ‐ AlOOH has hierarchical flower‐like structure, composing of needle‐like building blocks. After calcinations at 800°C, it converts to cubic γ‐ Al 2 O 3 with hierarchical structure retained by a topotactical process. N 2 adsorption and desorption reveal that the obtained γ‐ Al 2 O 3 has a BET surface area of 101 m 2 /g with a narrow mesoporous size of about 13 nm and a broad macroporous‐size distributions of 200–500 nm, respectively. The as‐generated γ‐ Al 2 O 3 with hierarchical structure shows good capacities for removing Congo red from wastewater, indicating that 3D hierarchical structure has excellent adsorption ability.