Research on the pyrolysis characteristics and mechanisms of waste printed circuit boards at fast and slow heating rates. (15th July 2022)

• Record Type: Journal Article
• Authors: Cao, Rui; Zhou, Ruishi; Liu, Yongqi; Ma, Duo; Wang, Jing; Guan, Yulei; Yao, Qiuxiang; Sun, Ming
• Is Part Of: Waste management. Volume 149(2022)
• Page Start: 134
• Page End: 145
• Publication Date: 2022-07-15
• Subjects: Waste printed circuit boards -- TG -- Py-GC/MS -- FTIR -- DFT analysis; BDE bond dissociation energy -- BPA bisphenol A -- DAEM distributed activation energy method -- DFT density functional theory -- DGEBA bisphenol A diglycidyl ether -- DTG derivative thermogravimetry -- Ea activation energy -- EDS energy dispersive X-ray spectroscopy -- F-M fast multi-step pyrolysis -- F-S fast single-step pyrolysis -- FTIR Fourier transform infrared spectrometer -- FWO Flynn-Wall-Ozawa -- GC/MS gas chromatography/mass spectrometry -- IDC International Data Corporation -- KAS Kissinger-Akahira-Sunose -- Py-GC/MS pyrolysis-gas chromatography/mass spectrometry -- SEM scanning electron microscopy -- S-M slow multi-step pyrolysis -- S-S slow single-step pyrolysis -- TG thermogravimetry -- WEEE waste Electrical and Electronic Equipment -- WPCBs waste printed circuit boards -- ZPE zero-point vibrational energy; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2022.06.008
• Languages: English
• ISSNs: 0956-053X

Abstract

Graphical abstract: The product distribution and pyrolysis kinetics of one-step and multi-step pyrolysis of waste printed circuit boards (WPCBs) were investigated by TG and Py-GC/MS at fast and slow heating rates. The pyrolysis mechanism of WPCBs was deduced by density functional theory (DFT). Highlights: WPCBs were pyrolyzed by TG and Py-GC/MS at the same fast and slow heating rates. Product distribution and kinetics of WPCBs by single-step and multi-step pyrolysis. Benzene was produced abundantly and its formation mechanism was deduced. WPCBs pyrolysis can produce light aromatic hydrocarbons and phenols. The pyrolysis mechanism based on free radical reactions was deduced by DFT. Abstract: The pyrolysis treatment of waste printed circuit boards (WPCBs) shows great potential for sustainable treatment and hazard reduction. In this work, based on thermogravimetry (TG), pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS), and density functional theory (DFT), the thermal weight loss, product distribution, and kinetics of WPCBs pyrolysis were studied by single-step and multi-step pyrolysis at fast (600 °C/min) and slow (10 °C/min) heating rates. The heating rates of TG and Py-GC/MS were the same for each group of experiments. In addition, the bond dissociation energy (BDE) of WPCBs polymer monomers was calculated by DFT method. Compared with slow pyrolysis, the final weight loss of fast pyrolysis is reduced by 0.76 wt%. The kinetic analysis indicates that the activation energies of main pyrolysis stages range from 98.29 kJ/mol to 177.59 kJ/mol. The volatile products of fast pyrolysis are mainly phenols and aromatics. With the increase of multi-step pyrolysis temperature, the order of the escaping volatiles is phenols, hydrocarbyl phenols, aromatics, and benzene (or diphenyl phenol). The pyrolysis residue of WPCBs may contains phenolics and polymers. Based on the free radical reactions, the mechanism and reaction pathways of WPCBs pyrolysis were deduced by the DFT. Moreover, a large amount of benzene is produced by pyrolysis, and its formation mechanism was elaborated.