Thermal treatment of MSWI fly ash with different additives by microwave heating

In this study, a new modified process was served for immobilization of combined municipal solid waste incineration (MSWI) fly ash/copper sludge, MSWI fly ash and washed fly ash/activated carbon, and MSWI fly ash/coal ash by microwave heating. From the present study emerges that the microwave process applied to the tailored mixtures is a useful technique to valorize the fly ash. The obtained sintered products or glassy materials show low metals ions releases with respect to the original ashes. From the thermal characterization it appears that the materials are also suitable for the obtainment of sintered products or glassy materials. Lead and copper metals were well restrained in the structure of glass-ceramics and the leaching concentration can meet the legal criteria. The hardness sintered products are higher compressive strength and meets the allowable limits (10 kgf/cm²) for landfill disposal in Taiwan. The weight ratios of the fly ash/coal ash (1/1) can be vitrified (made glassy) by melting, and heavy metals in the fly ash can be immobilized in the amorphous to form highly stable glassy or slag. An accurate selection and proper ratios of the used wastes allows producing glassy with suitable properties and suggests a possible way for MSWI fly ash re-utilization.