Abstract: There is provided a process for preparing alumina. The process comprise leaching an aluminum-containing material (for example an industrial waste product chosen from red mud, fly ashes and a mixture thereof), with HCl so as to obtain a leachate comprising aluminum ions and a solid, and separating the solid from the leachate. Then, the process comprises reacting the leachate with HCl so as to obtain a liquid and a precipitate comprising the aluminum ions in the form of AlCl3, and separating the precipitate from the liquid. Then, the precipitate is reacted with a base. Finally, the process comprises heating the precipitate under conditions effective for converting the precipitate into Al2O3.