Method for producing hydrated silicon dioxide and aluminum-iron water treatment agent by using coal ash

The invention discloses a method for producing hydrated silicon dioxide and an aluminum-iron water treatment agent by using coal ash as a raw material. The method comprises the following steps of: crushing coal ash until granularity is less than 500mu m, mixing and stirring the crushed coal ash and a cosolvent NaF according to a proportion, adding water, mixing, adding concentrated sulfuric acid, mixing, and dissolving and separating Al and Fe out of a glass body through one-step leaching; performing two-step leaching on the separated glass body, preparing gel, regulating pH, raising the temperature, isolating, ageing, filtering, washing, drying under vacuum and grinding to prepare solid superfine silicon dioxide; performing neutralization, oxidization, alkalization, precipitation and filtration on the Al and Fe crystalline solids separated out through one-step leaching to obtain iron-containing filter cakes and polymerized aluminum sulfate filtrate; and performing activation, stable emulsification and the like on the iron-containing filter cakes to obtain solid polymerized ferric sulfate, performing evaporation, activation, stable emulsification and the like on a part of the polymerized aluminum sulfate filtrate to obtain solid polymerized aluminum sulfate, and preparing an AlF3 product from the other part of the polymerized aluminum sulfate filtrate. The method has the advantages of high added value, higher comprehensive utilization degree, higher practicability, and simple process and equipment, and is easy to operate.