Kinetic study on the slow pyrolysis of nonmetal fraction of waste printed circuit boards (NMF-WPCBs)

In this study, the pyrolysis behaviour of nonmetal fraction of waste printed circuit boards (NMF-WPCBs) was studied based on five model-free methods and distributed activation energy model (DAEM). The possible decomposition mechanism was further probed using the Criado method. Thermogravimetric analysis indicated that the NMF-WPCBs pyrolysis process could be divided into three stages with temperatures of 37-330 degrees C, 330-380 degrees C and 380-1000 degrees C. The mass loss at different heating rate was determined as 26.85-29.98%, 13.47-24.21% and 20.43-23.36% for these stages, respectively. The activation energy (E-alpha) from various model-free methods first increased with degree of conversion (alpha) increasing from 0.05 to 0.275, and then decreased beyond this range. The coefficient (R) from the Flynn-Wall-Ozawa (FWO) method was higher, and the resulting E-alpha fell into the range of 214.947-565.660 kJ mol(-1). For the DAEM method, the average E-alpha value was determined as 337.044 kJ mol(-1), comparable with 329.664 kJ mol(-1) from the FWO method. The thermal decomposition kinetics of NMF-WPCBs could be better described by the second-order reaction.