Heavy metal migration during vitrification of municipal solid waste incinerator fly ash

Fly ash from municipal solid waste incinerators contains various pollutants including potentially hazardous heavy metals. Vitrification is an effective technique for stabilizing the heavy metals. The influence of ash composition on the migration characteristics of six heavy metals was studied in experiments performed in a lab-scale furnace with an air atmosphere at 1460°C with the basicity of the CaO/SiO₂ fly ash varied from 0.6 to 4.6. A model was developed to evaluate the binding efficiency of the heavy metals. The results show that an increased CaO content results in decreased binding of the heavy metals except Cd. Increase of the SiO₂ content has the opposite effect. A critical basicity gives the highest binding efficiency of heavy metals. For the fly ash used in these tests, the critical basicity is about 1.0.