Effects of Basicity (CaO/SiO2) on the Behavior of Heavy Metals from Sludge Incineration Ash by Vitrification Treatment

Heavy metals are one of the important factors that need to be considering for the disposal of sludge incineration ash. Vitrification by melting has been identified as a potentially effective tool that can solidify the heavy metals into the glass matrix structure. In this.paper, the characteristics of heavy metals in sludge incineration ash (SIA) were studied by using Community Bureau of Reference (BCR) sequential extraction procedure. Fractions extracted by the BCR sequential procedure were acid soluble/exchangeable, reducible, oxidizable and residual fraction, respectively. The total contents of Cu were the highest, followed by then Zn, Cr and Ni, and the content of Pb was the least. The effects of basicity (CaO/SiO2) on the solidification efficiency of heavy metals and the leaching toxicity of obtained molten slag were investigated. The molten slags demonstrated strong capacity on the stabilization/solidification of heavy metals. With the basicity value increasing from 0.4 to 0.8, the solidification efficiency of Cu, Zn, Pb and Ni decreased first and then increased, while that of Cr decreased straightly. The heavy metal leaching test results of the molten slags were far lower than the limits required by the regulatory standard of EPA, confirming the possibility of engineering and construction applications.