PBDEs Emission from Waste Printed Wiring Boards during Thermal Process

摘要

Polybrominated diphenyl ethers (PBDEs) contained in waste printed wiring board (PWB) matrix and surface dust can be emitted into the air during thermal process, which is widely used to detach the electronic components from the base boards of waste PWB. In this study, PBDEs concentrations in air and dust samples were detected in a PWB-heating workshop, and men heating experiments of PBDEs-containing materials in a quartz tube furnace were performed to investigate the PBDEs emission mechanism. The results showed that the mean concentrations of Σ_8PBDEs in PM_(10) and TSP were 479 and 1670 ng/m~3, respectively. Compared with surface dust collected from waste PWB (15600 ng/g), PBDEs concentrations in dust from the workshop floor (31 100 ng/g), heating machine inside (84 700 ng/g), and the cyclone extractor (317 000 ng/g), were condensed after thermal process. Heating experiments showed that the emission rates of PBDEs from PBDEs-containing dust were obviously higher than those from PWB fragments in the first 1-h time. The cumulative amounts of PBDEs emitted from dust increased rapidly at first, and then leveled off to become asymptotic to the maximum amounts. At the temperature of 300 ℃, the PBDEs emission from dust mainly occurred within the first 5 min, and the average emission rates for BDE-28, -47, and -99 among the first 5 min were 1230, 4480, and 1950 ng/(g-min), respectively. During the initial 1-h period, the trends of PBDEs emission from PWB fragments had a linear increase, and the emission rates of penta-BDE (BDE-47, -99, -100) at different temperatures were at a range of 9.75-11.5 ng/(g-min). All the results showed that PBDEs emission from PWB waste happened during thermal process, and management strategies were provided to reduce the occupational exposure level of PBDEs for workers.