There are provided processes for treating fly ash. For example, the processes can comprise leaching fly ash with HCl so as to obtain a leachate comprising aluminum ions and a solid, and separating the solid from the leachate; 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; and heating the precipitate under conditions effective for converting AlCl3 into Al2O3 and optionally recovering gaseous HCl so-produced.