HYDROTHERMAL TREATMENT OF INDUSTRIAL WASTES AND ITS IMPLICATION FOR IMMOBILIZING OTHER TOXIC WASTES

Abstract

The influence of the temperature of hydrothermal treatment in water of fly ash and bottom ash from incineration of municipal solid wastes is presented in this work. The evolution of the liquid phase was characterized by pH and electric conductivity measurements, and that of the solid phase was characterized by X ray diffraction (XRD), FT infrared (FTIR) spectroscopy and surface area (BET- N2) analyses. The results showed, in the case of the bottom ash, the formation of ettringite, -C2SH and gel CSH at low temperatures (ambient and 50 C). Ettringite is converted to katoite after treatment at 100 C. A zeolite type scolecite is detected at 200 C. As a result, the surface area of the bottom ash increased. In the case of fly ash, Friedels salt is massively formed at 100 C leading to an increase of 5 times the surface area. Hexagonal Friedels salt converted to cubic katoite after treatment at 150 C, subsequently decreases its surface area. Gel CSH and C2SH0.35 were also formed.