Preparation of High-Purity Aluminum Oxide via Mechanochemical Oxidation of Aluminum in a 0.1 M KOH Solution, Followed by Chemical and Heat Treatments

Abstract

We have examined the feasibility of preparing high-purity aluminum oxide by oxidizing granulated aluminum in a 0.1 M potassium hydroxide solution, followed by heat and acid treatments of the oxidation products. The aluminum oxidation product, consisting of two phases of Al(OH)₃ (bayerite and gibbsite), was first heat-treated at temperatures of 300, 600, 900, and 1200°C; then treated with hydrochloric acid; and calcined at a temperature of 1450°C. It has been shown that raising the preheat treatment temperature increases the total concentration of impurities, including Fe impurities, but reduces the concentration of alkali metals (K, Na, and Li). Using 99.7%-pure aluminum, we have prepared aluminum oxide with a purity at a level of 99.886%. Using 99.98%-pure aluminum, we have obtained aluminum oxide with a purity at a level of 99.993%.