(1) Sulfuric acid refining: 1. The fly ash is ground and calcined and activated, and then leached by sulfuric acid and concentrated to obtain aluminum sulfate crystals; 2. after calcination, an alkaline solution is added; 3. using iron removal technology, Aluminum hydroxide is obtained; 4. It is then calcined and aluminium is obtained. Because sulfuric acid has strong acidity and volatility, it not only poses a threat to the safety of operators, but also pollutes the environment. Therefore, pay attention to safety during the operation.
(2) Refining ammonium aluminum sulfate: 1. Grinding fly ash and mixing with ammonium sulfate, then calcining at high temperature; 2. Leaching with sulfuric acid and filtering; 3. Using ammonia water to make the pH of the filtrate to about 2.0, then Aluminium ammonium sulfate crystals were precipitated; 4. Sulfuric acid was added at 60 ° C and cooled to precipitate all crystals. And repeated operations 3 times to obtain ammonium aluminum sulfate; 5. The product is thermally decomposed to obtain aluminium. This method can obtain aluminium with higher purity.
(3) Fluorine ammonium refining: 1. Mix fly ash with ammonium fluoride (acidic) solution and heat to obtain crude alumina; 2. Add alkaline solution, then pass carbonation and pyrolysis to obtain purer aluminium. This method has a large extraction rate, but the cost is high.