Microwave-assisted hydrothermal synthesis of autoclaved bricks from municipal solid waste incineration fly ash and coal fly ash (MSWIFA) and its carbon emission

In this study, the feasibility of manufacturing low-carbon autoclaved municipal solid waste incineration fly ash and coal fly ash (MSWI-FA) bricks from MSWI fly ash and coal FA with microwave-assisted hydrothermal synthesis was investigated. To facilitate the experiment, block samples were prepared. The effects of microwave pre-treating parameters on the performance of block samples were investigated. Mechanisms of microwave pre-treating were studied. The effects of microwave pre-treating were further investigated by micro-analyses of synthesized block samples. Environmental impacts were discussed from heavy metal solidification/stabilization and CO2 emission. The results showed that the optimal microwave parameters were 30 min and 385 W. With microwave pre-treating, Al-substituted tobermorite crystallites were generated in raw material mixtures. For block samples, more Al-substituted tobermorite crystals were observed, and lower total pore volume and pore diameter were found. The solidification/stabilization rates of Cu, Pb, and Zn increased by 163.20%, 24.89%, and 78.77%, respectively, and CO2 emission could be reduced up to 53.40%.