Effect of Slag Composition on the Pb Leaching Behavior of Waste Molten Slag

For the purpose of understanding the relationship between slag composition and the Pb leaching behavior of waste molten slag, two tests—a reagent addition test and an actual slag test—were performed using optical basicity as a composition indicator. In the reagent addition test, under acid-leaching conditions, the Pb leaching ratio showed a positive correlation with optical basicity. Under water-leaching conditions, the higher the optical basicity of the slag was, the higher the leachate pH was. Moreover, the higher the leachate pH was, the lower the Pb leaching concentration was because the saturated solubility of Pb hydroxide was low in the pH range of 9-11. In the actual slag test, the overall tendency was same as in the reagent addition test, but the correlation of the data fell. We consider that the result was also influenced by the grain-size of the slag and the chemical form of Pb. Under water-leaching conditions, Pb leaching behavior could not be proved clearly because the Pb concentration of the actual slag was low.