Pre-desilication method, leaching method, dealkalization method and separation method for coal fly ash, and method for extracting aluminum from coal fly ash

The present invention discloses a method for extracting aluminum from coal fly ash. According to the methods disclosed by the present invention, polypropylene glycol and/or an anionic macromolecular surfactant are added into slurry obtained after a pre-desilication reaction and a leaching reaction, and at least one of auxiliary agents of the polypropylene glycol, the anionic macromolecular surfactant and alkanolamine is selected to add into slurry obtained after a dealkalization reaction, so that the separation performance of the slurry is improved, and separation energy consumption of energy-consumption separation apparatuses, such as a plate and frame filter, and the like, is reduced; at the same time, sedimentation performance of the slurry further can be obviously increased, so that more liquid phases can be separated through sedimentation; and material amount fed into separation apparatuses, such as the plate and frame filter and the like, is reduced, burden of the separation apparatuses is effectively reduced, and separation energy consumption is further reduced. The methods disclosed by the present invention are simple to operate, and easy to implement.