Thermal Decomposition and Phase Transformation of Chrysotile in Asbestos-Containing Waste

In Korea, asbestos-containing waste (ACW) is disposed of in landfills. However, due to the limited landfill capacity and the potential health risks of asbestos contamination, alternative, safer disposal methods are needed. Heat treatment has been suggested as an alternative disposal method for ACW. Therefore, it is necessary to determine the optimal conditions for the thermal decomposition of chrysotile in ACW and reveal the mineralogical composition of heat-treated ACW. In this study, asbestos cement roof (ACR) and asbestos gypsum board (AGB) samples were heat-treated at 600, 700, 800, and 900 degrees C to identify the optimal heat treatment parameters to eliminate chrysotile fibers. The thermal, chemical, and mineralogical characteristics of the ACW were determined before and after heat treatment using multiple analytical methods. The ACR consisted of chrysotile, calcite, and ettringite, and the AGB consisted of chrysotile, gypsum, and calcite. After heat treatment at 900 degrees C, the ACR was mainly composed of cement component minerals and lime, while the AGB additionally contained anhydrite. SEM-EDS analysis confirmed the persistence of fibrous minerals in the ACW up to 800 degrees C. Furthermore, TEM-EDS analysis revealed hollow tubular morphology of chrysotile in the heat-treated ACR at up to 700 degrees C and in the heat-treated AGB at 600 degrees C. These results suggest that heat treatment at temperatures of at least 900 degrees C may be necessary for the complete thermal decomposition of chrysotile in ACW.