Efficient Method for Change of Asbestos Characteristics in Asbestos-containing Materials

Abstract

Objective Asbestos, which is a confirmed human carcinogen, has been used in the automotive and household goods industries, construction, and in the high-temperature processing of iron and steel materials. Therefore, asbestos waste is expected to occur steadily into the future. Under current South Korean regulations on disposal of the substance, 90% of asbestos waste is buried in designated sites in polyethylene wrapping following solidification. However, concerns regarding its potential exposure to the environment, the need for constant monitoring and management, and the declining availability of disposal grounds remain as limitations. The purpose of this study was to identify methods to effectively change the physicochemical characteristics of asbestos in asbestos-containing materials. Method The study focused on chrysotile, which makes up nearly 95 % of asbestos in use. Unprocessed chrysotile-containing materials from demolished buildings and laboratories (slates, Ceiling tiles, wire gauze, asbestos gloves, etc.) were treated in three conditions: (1) Heat treatment according to temperature and time (2) Acid treatment with oxalic acid (3) Combined treatment with temperature, time and oxalic acid. A polarized light microscope (PLM) was used for the qualitative analysis of both untreated and treated samples (reference: NIOSH Manual of Analytical Methods 9002). In the subsequent field emission scanning electron microcopy (FE-SEM) with an energy dispersive spectrometer, morphological and chemical changes (the existence, shape, and elemental change of asbestos fibers) in pre- and post-treatment samples were also examined. Results PLM and SEM/EDS analyses conducted on the heat-treated samples showed optical, morphological, and chemical changes at the condition of 700℃ for three hours for both asbestos gloves and wire gauze. Ceiling tile and slates showed incomplete changes when treated for a maximum of five hours at 1,100℃. In chemically treated samples (oxalic acid), differences were inconclusive throughout the test period, indicating that it would take more than 48 hours to treat asbestos with oxalic acid only. The combined treatment, designed to save energy and time, resulted in meaningful physicochemical property changes for all samples of gloves, wire gauze, ceiling tile and slate, with the condition of 0.3 M oxalic acid at 200℃ for 30 min-1 hour. Conclusion By using the 0.3 M oxalic acid and 200℃ heat for 30 min-1 hour under the condition of combined treatment, the transformation of asbestos occurred at a lower level of energy and in less time. Landfill disposal of asbestos in small countries like South Korea is limited. Research into morphologically changing the harmful properties is critical for effectively preventing public exposure through all possible exposure routes. The results of this study suggest useful data for future attempts to safeguard against asbestos waste, which otherwise poses a carcinogenic threat to generations to come.