Leaching behavior of Pb and Zn in air pollution control residues and their modeling prediction

Increasing attention has been paid to air pollution control (APC) resi dues in China recently due to the rising proportion of waste incineration and th e hazardous characteristics of the residues, among which heavy metal leaching to xicity plays an important role. Leaching behavior and potential risk of Pb and Z n in the APC residues from a Shanghai municipal solid waste (MSW) incinerator wa s studied, based on the leaching tests under different conditions and theoretica l calculation using a geochemical thermodynamic equilibrium model MINTEQA2. Res ults showed that, extractant species and liquid to solid (L/S) ratio predomina ntly controlled the leaching toxicity of Pb and Zn, while ionic strength, vibr ation method and leaching time had less effect on the metals release. Leachate/f inal pH determined the metal leaching behavior, which changed the speciation of heavy metals in the extraction system. The equilibrium aqueous speciation, preci pitation-dissolution of Pb and Zn was investigated according to the model comput ation, which was well in agreement with the experimental results.