Kinetics and debromination studies on the pyrolysis of waste printed circuit boards with the addition of copper and copper oxides

Abstract

Pyrolysis has proven an effective method of recycling waste printed circuit boards (WPCBs) for high-value product generation. The kinetics and debromination studies on the pyrolysis of WPCBs with copper species was performed using a thermogravimetric-mass spectroscopy analyzer and a vertical quartz-tube reactor. A multiple distributed activation energy model (M-DAEM) was applied to illustrate the potential multiple reactions over the thermal decomposition process. The introduction of copper species into WPCBs reduced the initial activation energies, resulting in lower decomposition temperatures. Meanwhile, several distinct subprocesses were observed and resolved by three-reaction models. The addition of CuO obtained the lowest liquid yield (53.9 wt %) and the maximum gas yield (8.9 wt %), and the introduction of Cu2O resulted in the highest solid yield (40.4 wt %). Copper particles preserved 57 % of bromine in residual solid, while CuO and Cu2O particles resulted in approximately 65 % and 74 % retention of bromine in the residues, respectively. Particularly, less than 3.7 % of bromine was transferred into the liquid when Cu2O was added. The optimal debromination performance of Cu2O was attributed to its effective capture capacity of HBr/Br2, fairly high catalytic efficiency on dissociating C–Br bond, and multipath conversion of organobromine to cross-linked carbonaceous compounds.