Sintering Stabilization of Heavy Metals in Municipal Solid Waste Incineration Fly Ash

The stabilization of heavy metals in municipal solid waste incineration (MSWI) fly ash has become a prerequisite for landfill disposal and resource utilization. This study focuses on a low-cost, one-step, medium-temperature sintering method for stabilizing heavy metals in fly ash to provide a reference for the stable and safe disposal of fly ash. Co-sintering of fly ash and silica fume at 1100 °C yielded new crystal phases including dicalcium silicate and ilvaite. The sintering process stabilized the heavy metals in the fly ash. The concentrations of typical heavy metals in the acetic acid leachate of calcined fly ash were lower than 0.05 ppm. Compared with the heavy metal concentration in the acetic acid leachate of untreated fly ash, the concentration of Ni was reduced by more than 95%, and the leaching concentrations of heavy metals such as Cu, Zn, Pb, and Cd were reduced by more than 99%. The heavy metal leaching toxicity of the calcined fly ash was significantly reduced, and its environmental hazard was extremely low.