Assessment of brominated flame retardants in a small mixed waste electronic and electrical equipment (WEEE) plastic recycling stream in the UK

Abstract

Identifying the presence of brominated flame retardants (BFRs) within individual polymer types prior to extrusion has given us a unique perspective on which polymers may be problematic in meeting European Union (EU) low persistent organic pollutant (POP) content limits (LPCLs) and the potential for mixed engineering plastics (MEP) to be used as a viable recycled product. Our findings suggest that careful management of the polymer types within the feed chips prior to extrusion could deliver extruded polymer pellets that meet the EU LPCL values for POP-BFRs (i.e. <1000 mg/kg). Within this study, three fractions of extruded polymer pellets (“light”, “medium”, and “heavy” MEP) were created using density separation. Each fraction was characterised for 28 legacy and novel BFRs with brominated diphenyl ether-209 (BDE-209) (68–37,000 mg/kg) and tetrabromobisphenol-A (TBBP-A) (17–120,000 mg/kg) both predominant and ubiquitous. Portable X-ray fluorescence (XRF) was utilised to measure Br in 120 individual MEP chips of various polymer types. Those chips that XRF flagged as having high Br concentrations (>2500 mg/kg) were subjected to further evaluation for BFR content via mass spectrometry analysis and the results compared with the XRF Br data. This revealed that in 22% of the 120 chips studied, XRF incorrectly identified the LPCL to be exceeded. Our data also identifies the presence of the novel BFRs decabromodiphenyl ethane (DBDPE) and 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE) in plastics derived from waste electronic and electrical equipment (WEEE). While the “light-MEP” samples contained POP-BFR concentrations below LPCLs, the “medium-MEP” and “heavy-MEP” fractions exceeded such limits. Management of the polymer chips by colour sorting resulted in significant reductions in concentrations of all BFRs in the clear polymers such that LPCL limits were not exceeded; however, concentration reductions in white polymers were insufficient to meet LPCLs.