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

• γ–AlOOH nanopowder was synthesized by 24 h of ultrasonication of Al in N 2 H 4 ·H 2 O at 30 °C. • The obtained γ–AlOOH was nanocrystals with the average size of 158.2 nm, and the specific surface area of 360.9 m 2 /g. • γ–AlOOH nanocrystals were generated via corrosion and erosion of Al coarse particles under sonication in N 2 H 4 ·H 2 O. • γ–AlOOH nanopowder exhibited an adsorption capacity of 100.0 mg/g after 60 min toward Congo red solution at pH 8.70. Boehmite (γ-AlOOH) nanopowders were facilely synthesized at room temperature by sonochemical corrosion and erosion of Al particles. After 24 h of sonication in N 2 H 4 ·H 2 O, 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 m 2 /g. In contrast, γ-AlOOH powders were not obtained after magnetic stirring of Al powders in N 2 H 4 ·H 2 O 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 N 2 H 4 ·H 2 O is preferable synthetic route for preparing γ-AlOOH nanopowders due to its simplicity.