The quality of postconsumer (PC) plastic wash water is essential for safe recycled plastic production, especially for food-contact applications. This study assesses the proliferation of chemicals of concern (CoCs) (e.g., phthalates and bisphenols) in waste wash water. To conduct the research work, various washing methods, for example, trommel, friction (only water), surfactant-caustic, caustic, and ultrasonic-assisted washing, are applied to PC polypropylene (PP). The phthalate and bisphenol concentration in PC PP wastewater has been determined by gas chromatography–triple quadrupole mass spectrometry and revealed di(2-ethylhexyl) phthalate and di-cyclohexyl phthalate. Wash water from ultrasonication-assisted washing and surfactant-based washing contains the highest CoC concentrations compared to other methods. Surfactant-containing wash water is reused for 15 batches of PC PP, determining no significant rise in phthalates or bisphenols until the 10th batch. Surfactant concentration declines over subsequent plastic batch washing. It is hypothesized that surfactant is adsorbed to the plastic’s surface as it is removed from the wash water. This is concerning because Triton X-100 (surfactant) can degrade into 4-tert-octylphenol, a known endocrine disruptor. Hypothetically, surfactant availability influences the targeted analyte’s accumulation in PC PP wash water. This study highlights that ultrasonication and surfactant-based washing generate more contaminated wastewater, potentially due to higher PC PP cleaning efficiency.
This research was supported by IAFNS Food Packaging Safety & Sustainability Committee