Heavy metal removal from MSS fly ash by thermal and chlorination treatments

The thermal behavior of heavy metals in the co-incineration of municipal solid waste-sludge incinerator fly ash (MSS fly ash) was studied using a laboratory-scale tube furnace. The results indicate that without the addition of chlorinating agents, temperature was an important parameter and had significantly influenced on heavy metal removal, whereas the residence time had a weak effect. Between 900 and 1000 °C for 60 to 300 min, heavy metals reacted with chloride-inherent in the fly ash, and approximately 80 to 89% of Pb, 48% to 56% of Cd, 27% to 36% of Zn and 6% to 24% of Cu were removed. After the adding chlorinating agents, the evaporation rate of the heavy metals improved dramatically, where the evaporation rates of Cu and Zn were larger than that of Pb and Cd. As the amount of added chlorinating agents increased, the removal rate of heavy metals increased. However, the effect of the type of chlorinating agent on the chlorination of heavy metals differed considerably, where NaCl had the weakest effect on the removal rate of Cu, Cd and Zn. In terms of resource recovery and decontamination, MgCl(2) and CaCl(2) are the best choices due to their efficient removal of Zn.