Feasibility of stabilizing Cd, Pb, and Ni in MSWI fly ash using leachate as an alternative stabilizer

For the synergistic disposal of municipal solid waste incineration (MSWI) fly ash and leachate, MSWI fly ash was stabilized using leachate, sodium sulfide (Na2S), and sodium diethyldithiocarbamate (DDTC) separately or simultaneously. Results show that the leaching concentration of Cd, Ni, and Pb can be reduced when leachate is used alone but exceeds the landfill admission contents. The leaching concentration of heavy metals were lower than the threshold of the pollution control standard of Chinese garbage landfill (GB 16889-2008) after curing for 14d when DDTC was beyond 1.5%, and Na2S more than 10% except for Pb. The results of orthogonal experiment showed that the lowest leaching concentration was got at 5-fold dilution of leachate, 3% Na2S and 0.8% DDTC, and DDTC was the most influential factor. The leachate can be utilized as a partial stabilizer for stabilization of fly ash. After chemical stabilization, the crystal structure of fly ash changed little, and the surface was densified. The analysis of two-dimensional correlation spectroscopy results showed that the different order between the major function groups of fly ash and stabilizers was got, may be related to chelation, chemical reactions, and precipitation.