Acid Leaching Aluminum from Boiler Slag - Effect of Fluoride Additives on the Aluminum Dissolution

The objectives of this work are to study the influence of fluoride additives on aluminum recycling from the boiler slag. The effect of adding different amounts of fluoride, such as NaF, NH4F, KF and CaF2, was investigated. An elemental analysis of aqueous solutions leached by sulfuric acid and hydrochloric acid was determined by EDTA-Na2-ZnCl2 titration method. The components and microstructures of the samples were examined by means of XRF, XRD and SEM. Acid strength, leaching time, solid/liquid ratios and different additives were conducted in this experiment. The fluoride additives have a significant effect on the leachability of alumina in the boiler slag. NH4F is the best choice economically because of low dosage and high efficiency.