Synthesis of nano-alumina powder via recrystallization of ammonium alum

Abstract

In the present study, a recrystallization method was implemented to recover alumina powder from ammonium alum crystal. The ammonium alum was completely dissolved in water and treated by ultra-sonication to prevent the agglomeration of the alum crystal. The white precipitate was dried at 150 °C for 6 h, and calcinations at different temperatures were performed for 2 h. The XRD results indicated the crystalline structure of alumina with two main phases: γ-Al2O3 and α-Al2O3 at 800 and 1200 °C, respectively. The N2 adsorption/desorption isotherm results indicated that the surface area for the powder in the γ phase, which can be applied in catalysts, was 142.5 m2/g, while, in the α-phase, it was 15.3 m2/g. The morphologies elucidated that the powder particles were widely distributed in the range of ≤160 nm at different calcination temperatures and this may be attributed to increments in the particle agglomeration as the calcination temperature increased.