Research on Optimized Experimental Conditions of Acid Leaching to Extract Alumina from Fly Ash

Acid leaching is used to extract alumina from fly ash with generally concentrated sulfuric acid as solvent and fluoride as co-solvent. This method has some problems such as low leaching rate, fluoride environmental pollution, etc. The factors influencing the leaching rate with orthogonal test method are studied in this paper. By optimizing the experimental conditions, not only is the leaching rate of aluminum improved but also the environmental pollution is reduced. The results show that when the temperature reaches the boiling temperature of the dissolution, the concentration of sulfuric acid is 12 mol/L, the solid-to-liquid ratio is 1∶3, the elution time is 120 min, and m(KF)∶m(fly ash)=0.04, the leaching rate of aluminum can be up to 91.2%, and the toxic fluoride dosage is reduced by half in the same leaching rate.