Thermal degradation and pollutant emission from waste printed circuit boards mounted with electronic components

Abstract

Waste printed circuit boards mounted with electronic components (WPCB-ECs) are generated from electronic waste dismantling and recycling process. Air-borne pollutants, including particulate matter (PM) and volatile organic compounds (VOCs), can be released during thermal treatment of WPCB-CEs. In this study, organic substances from WPCB-ECs were pyrolyzed by both thermo-gravimetric analysis (TGA) and in a quartz tube furnace. We discovered that board resin and solder coating were degraded in a one-stage process, whereas capacitor scarfskin and wire jacket had two degradation stages. Debromination of brominated flame retardants occurred, and HBr and phenol were the main products during TGA processing of board resin. Dehydrochlorination occurred, and HCl, benzene and toluene were detected during the pyrolysis of capacitor scarfskin. Benzene formation was found only in the first degradation stage (272–372 °C), while toluene was formed both in the two degradation stages. PM with bimodal mass size distributions at diameters of 0.45–0.5 and 4–5 μm were emitted during heating WPCB-ECs. The PM number concentrations were highest in the size ranges of 0.3–0.35 μm and 1.6–2 μm. The research produced new data on pollutant emissions during thermal treatment of WPCB-ECs, and information on strategies to prevent toxic exposures that compromise the health of recyclers.