Inhibition of Polybrominated Dibenzo-p-dioxin and Dibenzofuran Formation from the Pyrolysis of Printed Circuit Boards

Abstract

Waste printed circuit boards containing brominated flame retardants were pyrolyzed in a high-temperature melting system to observe the formation behaviors of polybrominated dibenzo-p-dioxins (PBDDs) and dibenzofurans (PBDFs). In this study, the results showed that the formation of PBDD/ Fs during pyrolysis can be destroyed under controlled primary combustion conditions. There were two significant factors that influenced the extent of PBDD/F formation. The first factor was temperature. The results showed that, both the total PBDD/F content in the bottom ash and the total PBDD/F emission factor from the flue gas decrease by approximately 50% with an increase of the pyrolysis temperature from 850 to 1200 degrees C. The second factor was the addition of CaO. The possible mechanism involves the reaction between CaO and HBr to form the solid-phase product CaBr2. Thus, the addition of CaO is effective in adsorbing HBr and results in the inhibition of PBDD/F synthesis by more than 90% and further prevents the acid gases (HCl and HBr) that corrode the equipment. In conclusion, due to the persistence and toxicity of PBDD/Fs, a combined regulation for controlling both PCDD/Fs and PBDD/Fs is of great importance for environmental protection issues.

Pyrolysis and combustion of electronic wastes

“…Zeolites and inorganic bases are used to reduce these emissions [8][9][10][11]. Blazsó and Czé gé ny [8] used some molecular sieves in the pyrolysis of polycarbonate blended with TBBPA and epoxy resin containing TBBPA.…”

“…These same authors copyrolyzed printed circuit boards with some solids with basic character obtaining the debromination of bromophenyl groups and a decrease in the yields of bromostyrenes [9]. Lai et al used CaO to adsorb the HBr emitted in the combustion of ECs and to inhibit the PBDD/F synthesis [10]. Finally Hall and Williams used zeolites in the pyrolysis of two flame-retarded plastics and found a positive effect in the removal of volatile organobromine compounds [11].…”

Materials recovery from waste printed circuit boards by supercritical methanol

“…Effect of reaction temperature on the product conversion rate and distribution (reaction time: 60 min; S/L: 1:30, g/mL). sures (9,12,15,18, and 21 MPa) were applied in the SCM process.…”

“…Chemical recycling is to decompose the waste polymers into their monomers or some useful chemicals by means of chemical reactions. Pyrolysis is a chemical recycling technique that has been widely researched [7][8][9][10] as a method of recycling polymers in waste PCBs. During the pyrolysis process (heating without oxygen), the organic part is decomposed to low molecular products (liquids or gases), which can be used as fuel or chemical source.…”

Electronic Waste Disassembly with Industrial Waste Heat

“…Therefore, disassembling ECs from WPCBs is a crucial step in the WPCBAs recycling chain to conserve scarce resources, reuse functioning ECs, and eliminate potential exposure to hazardous materials. 2,22,23 Developing sustainable technology for WPCBAs disassembly is urgent, particularly in the developing countries in Asia and Africa, where unregulated recyclers use artisanal tools to separate ECs by simply heating WPCBAs on a coal-heated plate to melt solders. Serious environment pollution and severe exposure to toxic chemicals result from these crude practices.…”