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

Abstract

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%.

Keywords:

• Municipal solid waste incineration fly ash
• low carbon
• heavy metal
• hydrothermal synthesis
• microwave pre-treating

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors acknowledge the financial support received from the National Key Research and Development Program of China (2021YFB3802001), the National Natural Science Foundation of China (Nos. 52178241 and 52242807), the Fundamental Research Funds for the Central Universities (Nos. 22120220599 and 2023-2-YB-20), and the Key Research and Development of the Shaanxi Province of China (No. 2022GY-163).