Emissions of brominated compounds and polycyclic aromatic hydrocarbons during pyrolysis of E-waste debrominated in subcritical water

Abstract

Degradation of brominated flame retardants present in printed circuit boards (PCBs) was tested using subcritical water in a high pressure reactor. Debromination experiments were carried out in a batch stirred reactor at three different temperatures (225 ºC, 250 ºC and 275 ºC) keeping a solid to liquid (S/L) ratio of PCB:water=1:5 during 180 min. Results indicated that debromination efficiency was increased with temperature (18.5 to 63.6% of bromine present in the original PCB was removed).Thermal decomposition of the debrominated materials was studied and compared with that of the original PCB. Thermogravimetric analyses were performed at three different heating rates (5, 10 and 20 K min -1 ), studying both the pyrolysis (inert atmosphere) and combustion (in air). Pyrolysis runs of the debrominated materials were also performed in a quartz horizontal laboratory furnace at 850 ºC, in order to study the emission of pollutants. More than 99% of the bromine was emitted in the form of HBr and Br 2 . Emissions of polycyclic aromatic hydrocarbons (PAHs) and bromophenols (BrPhs) decreased with the increase in the treatment temperature; naphthalene (10800 -18300 mg kg -1 original sample) and monobrominated phenols (12.8 -16.9 mg kg -1 original sample) were the most abundant compounds.

Pollutant formation in the pyrolysis and combustion of materials combining biomass and e-waste

“…The maximum total yield of 79.0 mg/kg was obtained when 281 pyrolyzing the sample of CWP+20% WCBs. This result can be explained by the marked initial 282 bromine content of this sample, as TBBPA is the flame retardant present in the used WCBs 283 (Soler et al, 2017). With respect to congener distribution, as occurred in the case of ClPhs, monosubstituted 287 congeners predominated, followed by dibrominated phenols.…”

“…Elemental analysis, ash content and the concentration 109 of bromine and chorine of this material can be found in a previous study (Soler et al, 2017). 110…”

Thermal degradation and pollutant emission from waste printed circuit boards mounted with electronic components

“…During the heating process, the organic materials, including board resin, plastics, brominated flame retardants (BFRs) contained in WPCB-ECs are degraded, and pollutants such as particulate matter (PM), volatile organic compounds (VOCs) (An et al, 2014;Chen et al, 2016;He et al, 2015), semi-volatile organic compounds (SVOCs) are emitted to the environment, thus causing contamination in the workshop and environmental pollution of surrounding areas (Ortuño et al, 2014a). Emission characteristics of pollutants such as polybrominated diphenyl ethers (PBDEs) (Die et al, 2019;Guo et al, 2015a, b), polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs) (Xiao et al, 2016), polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs), polycyclic aromatic hydrocarbons (PAHs), released from thermal treatment of WPCB have been investigated extensively (Li et al, 2018;Cai et al, 2018a, b;Duan et al, 2011;Soler et al, 2017;Ortuño et al, 2014b). However, previous studies on pollutant emission during thermal treatment have focused on the base boards of WPCB, and rarely on the pollutant emission released from ECs.…”

Chemical Recycling of Used Printed Circuit Board Scraps: Recovery and Utilization of Organic Products

“…However, pyrolysis generally requires high temperature (>300 • C) and generates toxic organic materials [2][3][4]7]. In particular, hazardous gases including bromine compounds are released [10,18,19]. Nevertheless, owing to its high efficiency and short residence time, pyrolysis has been frequently employed for the recycling of UPCB to obtain valuable materials [18,20].…”

“…In particular, hazardous gases including bromine compounds are released [10,18,19]. Nevertheless, owing to its high efficiency and short residence time, pyrolysis has been frequently employed for the recycling of UPCB to obtain valuable materials [18,20]. Chemical recycling, including glycolysis, aminolysis, and alcoholysis, demonstrates promise for the depolymerization of thermoplastic and thermosetting resins [11,[21][22][23][24][25].…”