Preparation of low melting temperature glass–ceramics from municipal waste incineration fly ash

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Glass–ceramics have been prepared from air pollution control residues (fly ash) of a municipal solid waste incineration (MSWI) plant in southern China. The use of additives was investigated in order to decrease the melting temperature of the waste and thus to reduce the costs of production of glass–ceramics from the vitrified waste. Results showed that the melting temperature can be decreased significantly from 1500 to 1200 °C, which was achieved by combining the MSWI fly ash with silica sand powder and a Fe 2O 3-rich and CaO-rich iron slag to form a glass in the SiO 2–CaO–Al 2O 3–Fe 2O 3 quaternary phase system. Sodium carbonate and borax were used as fluxing agents and TiO 2 of chemical grade was added as a nucleation agent. The main crystalline phase in both high and low melting temperature glass–ceramics was found to be diopside (Fe-bearing), and the microstructure exhibited the presence of fine crystals of size in the range 100–200 nm which developed at crystallization temperatures in the range 800–900 °C for 1–2 h. The leaching behaviour of the glass–ceramic materials was tested, and it was found to be lower than that of a cement-stabilized body that was fabricated using the same waste for comparison. The results demonstrate the feasibility of reusing MSWI fly ash for glass–ceramic production at relatively low melting temperature, e.g. in a less energy-intensive process, as a viable approach for tackling the problem of hazardous MSWI residues.