(534g) Production of Alumina From Fly Ash By a Mild and Cleaner Hydrometallurgical Process

Fly ash is a large volume solid waste generated during the coal combustion by coal-fired power plants, wherein the valuable alumina content could be up to 30-50%. A mild hydrometallurgical process to produce alumina from fly ash only by alkaline solution at comparatively low pressure and temperature was investigated. This novel process is also a cleaner process, where the excess alkaline solution reactant is recycled to the leaching of fly ash, followed by the crystallizing of sodium aluminate hydrate and then its seed decomposing to prepare aluminum hydroxide, calcined to produce alumina. By controlling the phase transformation of the multiphase complex components in the fly ash, overall more than 90% of alumina was recovered from fly ash. The final residues could be utilized as feedstock in construction materials. Furthermore, the reaction mechanism of the process is investigated. This mild and cleaner process could also be appropriate for the produce of alumina from other high Al-containing solid wastes.