Airborne emission characteristics of non-metallic waste printed circuit board pyrolysis

Waste printed circuit boards (WPCB) constitute a complex and rapidly growing fraction of waste electrical and electronic equipment, yet fundamental data on the pyrolysis behavior of brominated flame-retardant WPCB, particularly regarding volatile organic compound (VOC) evolution and bromine fate, remain limited. In this study, the physicochemical characteristics and pyrolysis behavior of brominated WPCB were systematically investigated to provide essential information for environmentally sound resource recovery. Elemental analysis indicated that WPCB contains 14–18 wt% carbon and 1.2–1.4 wt% hydrogen, while X-ray fluorescence analysis revealed a high ash content dominated by CaO (33–47%), SiO₂ (19–30%), and Al₂O₃ (2.7–5.6%), with residual copper also present. WPCB samples with particle sizes ranging from 0.38 to 4.0 mm were subjected to pyrolysis. Thermogravimetric analysis identified a distinct two-stage degradation mechanism, consisting of a sharp decomposition at 350–400 °C followed by a broader degradation region at 500–600 °C, with a cumulative mass loss of 15–25% at 950 °C. The apparent activation energy of the first degradation stage was 98.7–139.7 kJ·mol −1 .At elevated temperatures, VOC were dominated by aromatic hydrocarbons (44%), followed by alkanes, oxygenated compounds, and brominated species. Major VOC included isopentane, bromomethane, acetone, toluene, xylene, trimethylbenzene, and ethylbenzene. Most bromine was volatilized during pyrolysis and effectively recovered as bromide in aqueous scrubbing systems. These results provide new insights into the coupled relationships among composition, thermal degradation, VOC evolution, and bromine behavior in brominated WPCB. • WPCB has high ash (SiO₂, CaO) and is rich in C, Br, and Cu. • Pyrolysis proceeds via two distinct degradation stages at 350–400 °C and 500–600 °C. • Moderate activation energies indicate thermally controllable initial pyrolysis. • Liquid yield rises with temperature, along with VOCs and Br-containing compounds release. • Bromine is preferentially volatilized and recovered as bromide via aqueous gas scrubbing