Microstructural changes of processed vitrified solid waste products

Toxic lead-rich solid industrial wastes were stabilized by the vitrification method. Vitrification was attained by the addition of SiO2 and Na2O as vitrifying and melting agent, respectively. The non-toxic, homogeneous, vitreous products studied in the present work, contain 60 wt.% of solid waste. Products with such a high content of solid waste comprise an economically realistic suggestion, but are easily devitrified in conditions of large-scale production due to the difficulty to achieve rapid cooling conditions in the whole volume of a large piece of stabilized product. Thus, it must be ascertained that the loss of homogeneity is not accompanied with the loss of chemical stability. Differential Thermal Analysis (DTA) was applied in order to inspect the prospect to crystal phase separation. The separated crystal phases were characterized by X-ray diffraction and transmission electron microscopy. Possible devitrification processes are investigated in order to interconnect the microstructure with the chemical stability of the devitrified products. (C) 2002 Elsevier Science Ltd. All rights reserved.