Waste-derived glass-ceramics fired in nitrogen: Stabilization and functionalization

In a circular economy perspective, waste-derived materials are attractive once the adopted manufacturing technology combines low costs, absolute stabilization of pollutants and interesting functionalities of the product. This paper deals with the enhancement of chemical stability and functionalities of highly porous glass-ceramic foams, from vitreous residues the plasma processing of municipal solid waste (‘Plasmastone’), by firing in nitrogen, at 800–1000 °C. Before firing, the processing relied on alkali activation of glass suspensions, followed by intensive mechanical stirring. Previous experiments had demonstrated that the stabilization of pollutants could be achieved only by mixing Plasmastone with 30 wt% recycled boro-alumino-silicate glass, in samples fired in air. The change in the atmosphere had a significant impact on the Fe²⁺/Fe³⁺ balance, leading to a different phase assemblage, in turn causing the stabilization of pollutants even operating with more common recycled soda-lime glass. The new phase assemblage also promoted functionalities such as electrical conductivity, relative permittivity and electromagnetic shielding effectiveness.