Contaminants and levels of occurrence in washed and shredded poly(ethylene terephthalate) from curbside collection. Part 1: Extraction conditions

Abstract

The aim was to determine which contaminants were present in washed and dried shredded poly(ethylene terephthalate) (PET, flake) obtained from curbside collection and whether the concentrations were above the US FDA threshold of 215 ppb. Thirty-two semivolatile contaminants were extracted from the treated flake by Soxhlet extraction using dichloromethane as a PET swelling solvent and gas chromatography-mass spectrometry (GC-MS) was used for identification and quantification. Soxhlet extraction of flake ground to 0–300 µm was effectively completed in 24 h, whereas sonication reduced the extraction time to 3 h. In contrast, Soxhlet extractions of flake ground to a larger particle size range (300–425 µm) were completed in 4 h, possibly due to less aggregation in the extraction thimble. The levels of 26 contaminants were below 215 ppb, but six were not. Dodecanoic acid was present at about 1200 ppb, 2-butoxyethanol was approximately 1000 ppb, limonene, benzophenone and methyl salicylate were above 800 ppb, and 2-methylnaphthalene near 215 ppb.