Novel trends in the thermo-chemical recycling of plastics from WEEE containing brominated flame retardants

• Published in: Environmental science and pollution research international Vol. 28; no. 42; pp. 59190 - 59213
• Main Authors: Charitopoulou, Maria Anna, Kalogiannis, Konstantinos G., Lappas, Angelos A., Achilias, Dimitriοs S.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-11-2021; Springer Nature B.V
• Subjects: Additives; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Biodegradability; Biodegradation; Bromination; Bromine; Catalysts; Chemical recycling; Dioxins; Earth and Environmental Science; Ecotoxicology; Electronic devices; Electronic equipment; Electronic waste; Environment; Environmental Chemistry; Environmental Health; Environmental science; Flame retardants; High temperature; Life span; Monomers; Phenols; Plastic debris; Plastics; Plastics recycling; Pretreatment; Pyrolysis; Recent Developments and Innovative Strategies in Environmental Sciences in Europe; Recycling; Solvent extraction; Solvents; Supercritical fluids; Sustainability management; Trends; Waste Water Technology; Water Management; Water Pollution Control; Pyrolysis; Pretreatment; Chemical recycling; Catalytic pyrolysis; WEEE; Brominated flame retardants
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-020-09932-5

The amount of plastics from waste electric and electronic equipment (WEEE) has enormously increased nowadays, due to the rapid expansion and consumption of electronic devices and their short lifespan. This, in combination with their non-biodegradability, led to the need to explore environmentally friendly solutions for their safe disposal. One main obstacle when recycling plastics from WEEE is that they usually comprise harmful additives such as brominated flame retardants (BFRs) that need to be removed before or during their recycling. This paper reviews existing techniques for the recycling of plastics from WEEE and focuses specifically on the advantages, disadvantages, and challenges of pyrolysis as an environmentally friendly method for the production of value-added materials (monomers, hydrocarbons, phenols, etc.). Current technological trends available for the recycling of plastics containing brominated flame retardants are reviewed in an attempt to provide insights for future research on the sustainable management of plastics from WEEE. Emphasis is given on conventional pyrolysis, where a pretreatment step for the debromination of products is applied. This is required since brominated compounds treated at high temperatures may result in the production of harmful to health compounds such as dioxins. All current pretreatment methods (solvent extraction, supercritical fluid technology, etc.) are presented and compared in detail. Co-pyrolysis is also investigated, as it seems to be a very interesting approach, since no catalysts or solvents are used, and at the same time, more plastic wastes can be consumed as feedstock. Furthermore, catalytic pyrolysis along with key parameters, such as the type of the catalyst or pyrolysis temperature, are fully analyzed. Catalysts affect the products’ distribution and enhance the removal of bromine from pyrolysis oils. Finally, an emerging technique, that of microwave-assisted pyrolysis, is also highlighted, as it offers many advantages over conventional pyrolysis. Of course, there are some impediments, such as the operational costs or other difficulties as regards the industrial implementation of the mentioned techniques that need to be overcome through future works.