Facile sonochemical preparation of γ-AlOOH nanopowder via corrosion and erosion of Al coarse particles

Boehmite (γ-AlOOH) nanopowders were facilely synthesized at room temperature by sonochemical corrosion and erosion of Al particles. After 24 h of sonication in N₂H₄·H₂O, Al powders were completely converted into γ-AlOOH nanopowders. The obtained γ-AlOOH particles had an average diameter of 158.2 nm in 0.1 M NaOH aqueous solution, and a specific surface area of 360.9 m²/g. In contrast, γ-AlOOH powders were not obtained after magnetic stirring of Al powders in N₂H₄·H₂O at 30 °C, indicating that sonochemical effects (hotspots, microjets and shock waves) significantly facilitated the corrosion reaction and surface erosion of Al, resulting in the formation of γ-AlOOH nanocrystals. The isoelectric point and adsorption rate of γ-AlOOH toward Congo red (CR) were also investigated. γ-AlOOH nanopowders exhibited an adsorption capacity of 100.0 mg/g after 60 min of stirring with a 100 mg/L CR solution at pH 8.70. The sonochemical process involving Al powders and N₂H₄·H₂O is preferable synthetic route for preparing γ-AlOOH nanopowders due to its simplicity.