Sources, concentrations, and screening of hazardous brominated flame retardants from waste streams in Ireland
Sharkey, Martin James
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Brominated flame retardants (BFRs) are organohalogen compounds which are applied to polymer-based materials in order to meet fire safety standards. Some of the most commonly-used of these BFRs in consumer plastic over the last few decades were polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCDD) and tetrabromobisphenol-A (TBBP-A), which have been extensively used in: electrical and electronic equipment (EEE), household furniture and furnishings; vehicular textiles and plastics; and cavity wall insulation panels. However, comprehensive studies on these BFRs have resulted in their listing in the Stockholm Convention on Persistent Organic Pollutants and also in EU legislation, which define concentration limits on their use/presence in consumer articles. Plastics and textiles containing listed BFRs in excess of these limits are therefore considered “hazardous” and cannot be disposed of via conventional waste management methods. Within the Republic of Ireland, there has been a dearth of knowledge regarding the prevalence of these BFRs in waste streams, and there is currently no mechanism in place for the removal of the resulting hazardous waste from circulation. The present research aimed to fill this knowledge-gap, by determining concentrations of the above BFRs in consumer plastics and textiles entering the recycling stream, as well as in leachate collected from 40 municipal solid waste landfills across the country. Accompanying the collection of recyclable waste was an assessment of portable x-ray fluorescence (XRF) as a potential tool for the on-site screening of plastics and textiles containing BFRs in compliance with legislative limits. Approximately 800 samples were collected from eight waste and recycling sites around Ireland, undergoing in-situ determination of elemental bromine via XRF analysis. BFR concentrations were then quantified in 555 of these samples via established mass-spectrometric techniques in order to (i) establish a database of hazardous BFR concentrations in plastics and textiles in Irish waste and the resulting implications for recycling practices, and (ii) evaluate the efficacy of XRF as a screening tool for legislative compliance. Due to the large number of samples collected, a new method for the extraction of BFR compounds from plastics and textiles was developed, as existing techniques proved too slow and costly in terms of consumable-use. The new method involves the dissolution of samples in dichloromethane, followed by vortexing, sonication, and a final clean-up using concentrated sulphuric acid. The method showed equitable accuracy, as well as requiring less solvents and fewer consumables, compared to similar extraction techniques. This extraction method was then applied to all plastic and textiles samples collected as part of this research for the quantification of BFRs. The results of said quantification shows that BFRs are found in various types of plastic and textile waste, most notably in televisions and display units, small household appliances, insulation foams, and household furniture. Using the most recent figures available, it’s estimated that approximately 4,000 tonnes of hazardous plastic and textiles waste is generated yearly in Ireland. As there is currently no mechanism for the removal of this waste from circulation, it is likely that a large proportion of BFR-treated plastics are being recycled/re-used. In addition to recycled waste, landfills are also shown to contain notable amounts of BFR-treated waste, with high concentrations of PBDEs in particular (in excess of 350 ng L-1) being found in some leachate samples collected. In general, the concentrations of BFRs in leachate were found to be lower at older sites which do not have effective leachate control and clean-up operations in place (i.e. unlined sites). This suggests that there is considerable contamination of the environments surrounding older landfill sites with hazardous BFRs. An effective way to ultimately remove BFRs from circulation would be via the screening of waste using portable XFR at recycling sites. The methodology developed in the present work uses XRF-determined elemental bromine as a surrogate for BFR-content in plastics and textiles, designating waste as “hazardous” if bromine is detected in excess of 710 mg kg-1. This methodology shows an effective screening rate of roughly 94 %, successfully segregating the waste as either safe to recycle, or requiring specialised treatment as hazardous waste. Further refinements to this methodology – separating plastics from electronics in EEE and using elemental antimony as a BFR-qualifier – can further improve this rate to ca. 97 %. The reliable use of this methodology will require continuous monitoring of BFR-use in plastics and textiles as novel BFRs may become increasingly used in place of the now restricted compounds.
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