Detoxification of Asbestos and Recovery of Valuable Metals from Detoxified Asbestos

Abstract

Studies on detoxification of asbestos and recovery of valuable metals from detoxified asbestos were conducted. First, asbestos was detoxified by a microwave heat treatment that used silicon carbide balls, which are inorganic heating elements that absorb microwaves and release heat at room temperature. For efficient heat treatment, the asbestos containing waste (ACW) was powdered by crushing and grinding processes and then a detoxification heat treatment was performed. Microwave heat treatment temperature and time variables were adjusted to investigate the detoxification properties according to heat treatment conditions. After heat treatment, treated ACW was analyzed for detoxification properties through crystal structure and microstructure analysis using X‐ray diffraction (XRD) and scanning electron microscopy. Complete asbestos detoxification was confirmed when the microwave heat treatment was performed at 1200°C for over 60 min and at 1300°C for over 10 min. Second, recovery of valuable metals from detoxified asbestos was carried out. The main components, Si, Ca, and Mg, of detoxified asbestos‐containing waste (DACW) were separated and recovered in the form of SiO2, CaSO4, and Mg(OH)2. SiO2 was separated first after treatment of DACW with HCl. Ca in the form of sulfate, CaSO4, was recovered when subsequent treatment of remaining aqueous acid solution with H2SO4. The remaining Mg was recovered by precipitation as Mg(OH)2 form under strong basic conditions. Each separated component was confirmed by XRD and Inductively Coupled Plasma (ICP) analysis.