Speciation of copper in the thermally stabilized slag

The Taiwan universities laboratory hazardous wastes have been treated by incineration at the temperature range of 1173–1273 K. By X-ray absorption near edge structure (XANES) spectroscopy, mainly CuO and CuSO4 are found in the incineration bottom and fly ashes. The incineration fly ash can be stabilized thermally at 1773 K in the plasma melting reaction chamber (integrated with the incinerator), and converted to slag. The concentration of leachable copper in the slag is reduced significantly mainly due to the fact that copper is encapsulated in the SiO2 matrix. In addition, the refined extended X-ray adsorption fine structure (EXAFS) spectra of copper also indicate formation of the Cu–O–Si species in the slag as the bond distances of 1.95 Å for Cu–O and 2.67 Å for O–Si are observed. This work exemplifies utilization of the synchrotron X-ray absorption spectroscopy to facilitate the thermal stabilization treatments of the fly ash hazardous waste using the plasma melting method.