Improving stabilization/solidification of MSWI fly ash with coal gangue based geopolymer via increasing active calcium content

Municipal solid waste incineration fly ash (MSWI FA) is categorized as a hazardous waste, which demands environmentally acceptable treatment due to its easy leachability toxic of heavy metals. This study investigated an innovative and improved method for stabilization/solidification (S/S) of MSWI FA with coal gangue based geopolymer by the addition of active calcium content. The specimen with addition of calcium oxide up to 10 % reached the compressive strength of 2.14 MPa at 28 d. The addition of 30 % calcium oxide resulted in the highest immobilization efficiencies of Cd (98.96 %) and Pb (99.19 %). X-ray Diffraction (XRD), Fourier Transform Infrared Spectrometry (FTIR), Scanning Electron Microscope (SEM), and thermogravimetric (TG) analysis indicated the generation of calcium-containing hydration products was promoted after the improvement of calcium content in binder. Heavy metals were stabilized through the chemical adsorption and ions exchange of amorphous hydration products. On the whole, this study illustrated that the incorporation of active calcium content can improve efficiently S/S of hazardous ash waste such as MSWI FA.