UV aging of microplastic polymers promotes their chemical transformation and byproduct formation upon chlorination

• Published in: The Science of the total environment Vol. 858; no. Pt 2; p. 159842
• Main Authors: Liu, Hang, Zhang, Xian, Ji, Bin, Qiang, Zhimin, Karanfil, Tanju, Liu, Chao
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2023
• Subjects: byproducts; Chlorination; chlorine; dimethyl phthalate; disinfection; Disinfection byproducts; environment; haloacetic acids; mass spectrometry; Microplastic polymers; microplastics; Polyamide; polyamides; polyesters; polyolefin; toxicity; UV aging; wastewater; Polyamide; Microplastic polymers; UV aging; Chlorination; Disinfection byproducts
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.159842

The presence and accumulation of microplastics (MPs) in water and wastewater is a growing concern. When released to the water bodies, microplastics can be subject to surface weathering due to ultraviolet (UV) exposure. In this study, the effects of UV aging of six MP polymers from three groups (e.g., polyamide, polyester, and polyolefin) on their chlorine reactivity, chemical transformation, and formation of disinfection byproducts (DBPs) were studied. Polyamide (e.g., polyamide 6) in both virgin and UV-aged forms showed significantly higher chlorine demands than other MP polymers (915.5–947.9 versus 7.0–21.1 μmol/g MP in 24 h), and polyolefins were relatively inert to chlorine. UV aging enhanced the destructions of functional groups of polyamide and polyester upon chlorination, promoting the chlorine demands and leaching of organics by up to 1.7- and 2.4-fold, respectively. Polymer monomer and oligomers of polyamide 6 and toxic or endocrine disrupting additives (e.g., dimethyl phthalate and butyl octyl phthalate) were identified in leachates from chlorinated MP polymers by mass spectrometry. Meanwhile, up to >10-fold increases in the yields of trihalomethane, haloacetic acid, haloacetaldehyde, haloacetonitrile, and haloacetamide were observed from 30-day UV-aged MP polymers as compared to their virgin counterparts. Overall, this study reveals that UV aging can promote the reactivity and chemical transformation of MP polymers during chlorination, especially for polyamide and polyester, increase the release of polymer monomers, oligomers, and additives, and aggravate the role of MP polymers as DBP precursors. [Display omitted] •Polyamide showed the highest chlorine reactivity and disinfection byproduct yield.•UV aging increased the chlorine reactivity of polyamide and polyester.•Chlorine induced damages on functional groups of UV-aged polyamide and polyester.•UV aging enhanced chemical transformation of microplastics during chlorination.•Chlorinated microplastics served as source of organics and disinfection byproducts.